# Method for tuning your speakers to your room



## kidpolaroid (Dec 17, 2016)

Last night, I was checking out a pair of studio monitors that provide a feature where the speakers are able to tune to your room.

They are a pair of JBLs that you can find if you google online.

If you read the reviews for them, many people agree that this feature is very helpful.

The way in which they do this, is that they come with a microphone that is placed in your room. The computer plays a sine sweep from the monitors and the mic listens while the JBL software creates a special EQ for your room to help combat some acoustic issues.

At least, that is my understanding of it.

The cool thing about the software is that it EQs *all* audio that passes through your monitors. You can A - B your mixes against anything with the speaker tuning remaining effective.


I was wondering how I could do that manually for my room. My monitors don't have this feature but I feel like if I were able to find a software that allows me to route all my computer's audio through an EQ that I have control over, I could tune the monitors to myself.

The Mac I use comes with an EQ feature but it only EQs audio that is sent through the "internal speakers". The EQ is also not great.

Does anybody have any idea how I could EQ all the audio of my computer while still sending it out of my interface? Thank you!

-Kyle


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## higgs (Dec 17, 2016)

What kind of audio interface do you have? Some interfaces, like the UAD line, make it possible to route sound through plugins before playing through the speakers. It takes a bit of clever routing, but is doable. 

The UMIK-1 microphone is great for use with calibration software like the freeware REW (Room EQ Wizard). There is some excellent instruction and advice on this topic on the Studio Building / Acoustics sub-forum of the Gearslutz site.


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## Gerhard Westphalen (Dec 17, 2016)

Reference 3 is probably the best software option around right now. There are higher end programs like Acourate or hardware boxes like the DEQX ones that do it as well. With Reference you can get another application to route all of your computer's audio through it. 

If you really want a cheap hardware solution you could get a graphic EQ but I'd advise against that.


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## kidpolaroid (Dec 17, 2016)

higgs said:


> What kind of audio interface do you have?


 Right now, just a scarlett 2i2 but soon it will be replaced with an apollo twin duo.


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## kidpolaroid (Dec 17, 2016)

Gerhard Westphalen said:


> Reference 3 is probably the best software option around right now. There are higher end programs like Acourate or hardware boxes like the DEQX ones that do it as well. With Reference you can get another application to route all of your computer's audio through it.
> 
> If you really want a cheap hardware solution you could get a graphic EQ but I'd advise against that.



Can you elaborate on the graphic EQ you mentioned and why that method is unadvisable? Thanks


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## higgs (Dec 17, 2016)

I added info to my original post above that gives some links to good info. Please see above.


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## Gerhard Westphalen (Dec 17, 2016)

kidpolaroid said:


> Can you elaborate on the graphic EQ you mentioned and why that method is unadvisable? Thanks



You can get something like the dbx 231s for $150 but I wouldn't want to pass all of my audio through a $150 box. It'll be much lower quality than using a software solution. You also don't have much control and can't have linear phase. You can get Reference 3 for basically that same cost and it'll give you infinitely better results. The only drawback is the complex routing you need if you want it system wide. In my case I just have a channel I feed through Cubase using the RME TotalMix's loopback feature. On Macs there are a number of programs that let you route the audio internally and then put in the plugin.


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## wst3 (Dec 17, 2016)

please allow me to rain on the parade...

It is theoretically possible to create a dynamic transfer function and the apply the inverse transfer function, with tweaks, to correct room problems of any ilk. The catch is that we haven't figured out how yet. Impulse responses are, by definition, time invariant, which means they take a single snapshot in time, and are blind to time dependent variations. One of the reasons we just don't know if this is really possible is that there isn't enough processing power<G>!

If you search for a system called LARES you can read more than you wanted to know about electronic room corrections, and why it isn't feasible right now.

All of the systems on the market today can correct SOME frequency domain problems. They do so by splitting the audio into hundreds of very narrow bands. Even then the corrections can be worse than the errors. A 33 band (1/3 octave) equalizer is simply not up to the task of correcting frequency domain room problems, they can be very effective at correcting frequency domain problems in the electronic portion of the system, and a well designed 1/3 octave equalizer will probably sound better (fewer artifacts) than even a well designed parametric filter set because filter summing is paramount in a graphic equalizer.

Time domain problems are an entirely different issue, and a frequency domain filter isn't going to do much to solve them. Time domain problems are caused by room dimensions that reinforce specific modes, or reflections that cause destructive interference. If the issue is reasonably static, and not large in magnitude you might just minimize it, but you can't cure it.

Which leads to the question are any of these systems worth purchasing. And the answer, sadly, is "it depends". I've heard such systems (specifically the Genelec system) in rooms that were already pretty darned good, and they did make a difference, and the difference was pleasing to the ears. I've heard others (names omitted) in more typical listening environments, and in every case I preferred the sound without the processing.

If you have $X to spend on room correction I think it is best spent on physical corrections. If you have nothing to spend there are still steps you can take to minimize problems - most notably loudspeaker and ear placement, which isn't always practical, but more often than not can make a positive difference.

Sorry to be a buzzkill, but there remain some laws of physics that refuse to bend to our wills!


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## pinki (Dec 17, 2016)

I use Coneq P2 Pro software from RealSound (which is now looked after by Innoton in Germany) to do what you say and it performs flawlessly and makes my monitors flat. You need to do some acoustic treatment too of course. There is a non Pro version I used for years before upgrading https://www.thomann.de/gb/real_sound_lab_coneq_p2.htm which uses less 'taps' (which is effectively the number of filters or bands) for a low price. A hardware graphic equaliser is a bad idea...it is too limited in the number of bands. Also the point of these solutions is that they offer an integrated solution...an analysis and resultant filter in one.


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## Gerhard Westphalen (Dec 17, 2016)

wst3 said:


> please allow me to rain on the parade...
> 
> It is theoretically possible to create a dynamic transfer function and the apply the inverse transfer function, with tweaks, to correct room problems of any ilk. The catch is that we haven't figured out how yet. Impulse responses are, by definition, time invariant, which means they take a single snapshot in time, and are blind to time dependent variations. One of the reasons we just don't know if this is really possible is that there isn't enough processing power<G>!
> 
> ...



I believe both Acourate and the DEQX boxes work on time domain problems. DEQX does so for speaker correction but I'm not sure if it also does so for the room correction. I've never heard one so I'm not sure how effective it is. The only down side is that it's a $6000 unit. Using active room treatment can also take care of this.

I'd agree that in some cases the correction makes things worse. I once tried Reference 3 in a room that was around +/- 2dB down to about 60Hz and it only made it worse.


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## mc_deli (Dec 20, 2016)

Gerhard Westphalen said:


> I once tried Reference 3 in a room that was around +/- 2dB down to about 60Hz and it only made it worse.


That sounds very odd without qualification. Had you done the test measurements? Were you at the listening position? Was the room treated at all?


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## Gerhard Westphalen (Dec 20, 2016)

mc_deli said:


> That sounds very odd without qualification. Had you done the test measurements? Were you at the listening position? Was the room treated at all?



Well when you're at +/-2dB it already sounds great so the phase shifts of all of the bands that it uses to try to straighten it all out causes more problems than it's worth to get it flatter. On those speakers you could hear everything. On linear phase mode it's fine. 

The +/-2dB was based on Reference's measurements done with an Earthworks measurement mic. Doing measurements with different programs revealed that it wasn't as flat and Reference didn't make it all that much flatter. There was also a digital EQ taking care of some frequencies as well as tuning the crossover points of the drivers in the main speakers. 

This was at the listening position in a room set up by someone who designs mastering studios. He had just tuned the speakers so I wanted to see if Reference could make any further improvements. There wasn't all that much room treatment. Just covering all of the first reflection points but the room was big enough with a massive ceiling that there aren't really any modal issues.


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## Hannes_F (Dec 20, 2016)

kidpolaroid said:


> Last night, I was checking out a pair of studio monitors that provide a feature where the speakers are able to tune to your room.
> 
> They are a pair of JBLs that you can find if you google online.



These are the JBL LSR 4328 (which I have but do not use for studio work any more) or 4326.

Actually, they are not doing what you think (and what I thought). All they do is to find one (1) resonance - the biggest - and pull that out. Yes, it is a 1 band EQ, at least I never saw them doing more.

They are nice speakers for some use but that feature is more a gimmick than anything else.


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## chillbot (Dec 20, 2016)

Hannes_F said:


> These are the JBL LSR 4328


I have these and love them, they sound so clear. Used for writing not for mixing except some A/Bing. But I never considered trying to use the gimmick... good speakers though anyway.


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## mc_deli (Dec 20, 2016)

Gerhard Westphalen said:


> Well when you're at +/-2dB it already sounds great so the phase shifts of all of the bands that it uses to try to straighten it all out causes more problems than it's worth to get it flatter. On those speakers you could hear everything. On linear phase mode it's fine.
> 
> The +/-2dB was based on Reference's measurements done with an Earthworks measurement mic. Doing measurements with different programs revealed that it wasn't as flat and Reference didn't make it all that much flatter. There was also a digital EQ taking care of some frequencies as well as tuning the crossover points of the drivers in the main speakers.
> 
> This was at the listening position in a room set up by someone who designs mastering studios. He had just tuned the speakers so I wanted to see if Reference could make any further improvements. There wasn't all that much room treatment. Just covering all of the first reflection points but the room was big enough with a massive ceiling that there aren't really any modal issues.


Well answered sir!


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## Joe_D (Dec 21, 2016)

wst3 said:


> If you have $X to spend on room correction I think it is best spent on physical corrections. If you have nothing to spend there are still steps you can take to minimize problems - most notably loudspeaker and ear placement, which isn't always practical, but more often than not can make a positive difference.



That's my opinion also. In a nutshell: fix the room instead of messing with the sound of your speakers.

For room fixing, speaker/ear placement info, head on over to the Gearslutz Studio building, acoustics forum. There are lots of cheap DIY ways to improve your room sound. 

Also, if you are on a Mac, check out FuzzMeasure software (I can't comment on the PC alternatives). Software can help you to understand what needs to be fixed in your room, and also which balance problems you are hearing are truly mix problems and which are room problems.


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## Nick Batzdorf (Dec 22, 2016)

Shockingly, I agree with Bill again:



> If you have $X to spend on room correction I think it is best spent on physical corrections.



Bill goes on to mention the basics: speaker placement and ergonomics.

Now, while I don't use it (other than the HF and LF screws on my UREI 809As), a small amount of speaker correction can be good. There are exceptions like the B&O bass calibration built into their Beolab 5s, but in general you're correcting minor things in the speakers, not the room. I haven't been crazy about the complicated inverse-curve-generating EQ I've tried; it just took the character out of my speakers without making it easier to hear.

So my opinion is that before anything else, you want to make your room workable. And I'm going to post the same thing again.

If you have money to call in the architects to customize room dimensions, float your room, soffit-mount speakers, whatever... never mind.

But setting up any standard room so it's good enough to work in really doesn't require as much crazy stuff as people have been led to believe. (This is for monitoring, not recording.)

The number one problem is too much reverb. You can solve that with broadband absorption behind the speakers, on your front wall. That also solves the problem of reflections coming from the same angle as the speakers, which are the only ones that combine with them in your ears (yes it's really true: side reflections categorically do not combine with the ones coming from the speakers in front; our brains separate them *).

The second problem is bass, which requires trapping because our rooms are too small to reproduce 56' waves without folding back. You can solve that with thick enough absorption at the front too, or you can use bass traps.

Those are the biggies, but a bookcase or something else diffusive - even acoustic diffusors! - behind you is usually good. And diffusion overhead is a good idea too.

* My friend Dave Moulton believes in hard, flat side walls. I did a lot of experimenting back in the day, and I agree with him. But his partner Manny LaCarruba recently told me he likes diffusors on the sides. Manny may be the best speaker designer in the world (along with all the things that go with that - acoustics, etc.), so I'm inclined to believe that he knows what he's talking about. I haven't tried diffusors on the sides.


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## higgs (Dec 22, 2016)

Shockingly, I agree with Nick... 

In my current space, I've added bass traps to as many corners as I could afford while trying my best to strike a balance between LF control and preservation of HF. Bass build up was really an issue for the first couple of weeks that I started. I found that, at least in my space, the cloud (3 broadband absorption panels) over my listening position made a tremendous difference. For the broadband absorption panels immediately behind my monitors, I chose to use a foil-faced insulation panel to retain high frequencies. 

It can be a deep rabbit hole to address and knock out acoustic unpleasantries. Ultimately, if you can work comfortably for a decent amount of time without feeling the absolute _need_ for a break, then you're going to be pretty well off - certainly better than several folks I know who just throw panels on the walls all willy-nilly without regard to what matters most: your ears, your comfort, and the accuracy of mixes.

There are lots of takes on how to tackle acoustics, but you might find the process least frustrating by accepting the notion that the process will be served well by really taking your time and not expecting it to be perfect...ever. But you can really do so much by even just repositioning speakers and/or moving your listening position, if that's an option.



Nick Batzdorf said:


> The number one problem is too much reverb. You can solve that with broadband absorption behind the speakers, on your front wall. That also solves the problem of reflections coming from the same angle as the speakers, which are the only ones that combine with them in your ears (yes it's really true: side reflections categorically do not combine with the ones coming from the speakers in front; our brains separate them *).
> 
> The second problem is bass, which requires trapping because our rooms are too small to reproduce 56' waves without folding back. You can solve that with thick enough absorption at the front too, or you can use bass traps.
> 
> Those are the biggies, but a bookcase or something else diffusive - even acoustic diffusors! - behind you is usually good. And diffusion overhead is a good idea too.


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## tack (Dec 22, 2016)

Nick Batzdorf said:


> But his partner Manny LaCarruba recently told me he likes diffusors on the sides.


FWIW, this was the advice from GIK too. Bass traps in the corners behind the speakers and diffusion on the sides and back. The only thing they suggested that I think you would disagree with is to have absorption at the first reflection point on the sides. For other side panels they suggested diffusors.


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## Nathanael Iversen (Dec 22, 2016)

There is some great advice in this thread. I have the Genelec 8351a's and the GLM kit that "optimizes for the room". Prior to getting the Genelecs, I had Mackie 824's and a very powerful sub - the original ones which served me well for over 12 years. I spent much more than the Mackie's on GIK room treatments - All corners floor to ceiling, behind speakers, first reflection points (including the ceiling), etc. I carefully optimized the placement of the Mackie's using a measurement omni microphone and Smaart (RTA software + a transfer function - lots of cheaper options if you don't mix live sound). I ended up with +-5db from 27Hz to 20kHz with 1/12th octave smoothing with five carefully placed DSP filters in a speaker processor that was serving as the sub crossover. The time domain was within the recommended specs for a Dolby mix room, so I called it done and happily set to using the system.

When I upgraded to the Genelecs this year, I did the same thing - tape off the floor in a 6" grid pattern in from front of the desk to the front wall, marking the centerline. This provided the ability to make fine adjustments and preserve symmetry and toe-in, etc. I set the measurement mic right where my head goes, and set up the rig for transfer function and pink noise @ 76 dbSPL = -20dbFS. By working the grid carefully, finding the optimal speaker placement is fairly straightforward - first going for most even bass response, and then working on the high's with toe-in. After music listening, and general validation, the first impression was not one of having "more bass or more highs" - I had a solid system with cheap Mackie's. The higher driver quality, better transient response, better imaging, etc all were apparent - but the actual frequency response wasn't that different. It was incremental, not night and day despite the huge price difference between the speaker sets. 

I finished by running the GLM optimization software and it made some surgical DSP changes that netted some improvements. The DSP made no wild adjustments - it can't fix mode issues. I saved it all into the speakers, and haven't thought about it since. The room is still +-5db @ 1/12th octave smoothing, ~25Hz-20Khz. The speakers are in a slightly different position than the Mackie's, but not hugely. The room is still the room, and since I haven't changed treatment, it is about the same. My desk is still my desk, and reflects in the same ways, etc. I still have a gigantic mode right at the 49Hz "G1". I would need to go after it with tuned membrane traps and/or some of the new AAVA active bass traps, which look interesting. 

So, the DSP is not magical, but it is fast and easy and made "smoothing" changes. The room treatment was some of the best money I've ever spent. The room sounds good just to be in. I've had visiting engineers comment that just standing in it "sounds good". The comment about having good time domain response is not to be overlooked. Getting rid of bass "ringing" is a very big deal, and the corner bass traps are significant.


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## Nathanael Iversen (Dec 22, 2016)

To give you an idea, how this works, I'll first give you the final plots from my Mackie installation, then I'll give you the same shot from the current Genelec installation. Here's the Mackie setup, with a very large Danley PA subwoofer filling in the low end - I set the crossover using Smaart - around 80Hz if memory serves. The Genelecs play low enough that they fill in the whole chart without a sub - and actually measure lower than the Danley in room. Note this is +-5 db with 1/24th octave smoothing, so this is a very granular plot. You can see what a well-treated room still looks like! It is far from "perfect", even though it "sounds great". 







Next is the RT60 - this is the time domain measurement mentioned above. It would be perfect if the line were flat. That is not happening without dedicated construction and acousticians. I was thrilled with this result using treatments mounted to walls.






And finally, the group delay, again with very conservative 1/24th octave smoothing to not hide anything:


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## Nathanael Iversen (Dec 22, 2016)

And now, here's the frequency response of my current installation, with 1/24th octave smoothing:






You can see that it is still +-5 dbSPL. I didn't retake the RT-60 because I didn't change any treatment, so that is not going to change - the room is still the room. So, why spend all that $$ on speakers? The overall result doesn't seem that impressively different.

The answer is partly visible in the phase traces. Notice how smooth the Genelec phase traces are, and with fewer inversions. This is the coaxial drivers in the 8351a's with DSP crossover vs. a well-executed standard two-way design with standard electrical crossover. The DSP in the Genelecs also accounts for and removes certain driver resonances and imperfections, and creates an optimal crossover for these three-way speakers. Taken together, this gives the Genelecs a VERY even off axis response, which is shown in the detailed specs Genelec publishes for these speakers. That off-axis response plays a big part in how the speakers radiate into the room, and how even they sound when I move around in front of the desk. The improvements in phase and coherence translate into a more transparent sound, pinpoint imaging, and a very "natural" presentation.

These details are noticed because of the treatment. Without the treatment, the raw room had the typical -20db suckouts, big modal spikes, etc. All the fancy speaker optimizations would be swamped by the room response. It is well worth spending $$ on buying or making acoustic treatment - certainly before dropping big coin for fancy monitors. You can have very modest monitors and have a very usable setup - even with very picky measurement standards that aren't hiding anything.


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## Nathanael Iversen (Dec 22, 2016)

And just for kicks - here's the 1/3rd octave smoothed response - the type of thing that manufacturers normally publish.






Look how smooth and perfect it is! But you already know from the previous posts that this is not really what is going on. 1/3rd octave smoothing is supposed to roughly correspond to human hearing. And indeed, the response in my room sounds even and smooth. It doesn't sound all cut up and jagged. But, what I know is that by working to improve the 1/12th or 1/24th octave response, the 1/3rd gets better and better. 

Oh, and for interest's sake, notice how the high end seems to roll off ~6db in this plot? That is part of how measurements don't always tell the whole truth. The wavelengths at 20kHz are VERY tiny and so is the tip of a 1/2" measurement microphone. Just moving the microphone tip an inch can cause wild swings in the highest end of the graph. With two speakers producing sound, there is significant comb-filtering just from the speakers interacting, and this also affects the accuracy of the measurement. Moving the microphone tiny amounts changes how that comb filtering affects the measured response. You can make the measurement "flat" or "bad" with micro-movements smaller than my head. So the graph is accurate for one 1/2" of space - but there are more of them.... and that's where the microphone doesn't tell the whole story, even though it is very accurate exactly where it is. The high end does not sound "soft" or muted in the room. 

This is all "stuff you can't control" past a certain point. You get the big modal and time domain stuff right with acoustic treatment, install monitors you can afford, tweak placement and DSP to the best of what is possible in your space, and you make music.


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## Nathanael Iversen (Dec 22, 2016)

Oh, and to answer the original poster - if you want to DSP stuff yourself.... use Room EQ Wizard mentioned above (free). Buy the Behringer measurement mic for less than $100. https://www.amazon.com/Behringer-DCX2496-Ultradrive-High-Precision-Loudspeaker/dp/B000NJ3YI8/ref=sr_1_6?ie=UTF8&qid=1482465068&sr=8-6&keywords=behringer+speaker+processor (You can buy a Behringer speaker processor (DCX2496)) for $300. Then you work with your software to figure out what correction you need and you put that into the Behringer and re-measure until you are happy. Don't try to correct modal issues. If you change an EQ setting to something radical like -10db and the measurement doesn't change at all, you are fighting a room mode. You can only correct it with treatment. The DSP is not magic and can't undo physical reality. For that you need the physical reality of treatment. But for less than $400 you can have quality DSP and a measurement setup that will let you know exactly what you are getting.


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## wst3 (Dec 23, 2016)

I don't know the particulars, but those phase measurements would make me nervous.

The final tests are really (a) do you enjoy working in the space, and (b) do projects translate well to the rest of the universe? It the answer to both is "YES" then you can pretty much rest until your ears become more discerning, which happens naturally over time.

Back to the discussion of physical treatment, because Nick's comment intrigued me!

There are three tools at your disposal - reflection, absorption, and diffusion. You have to use all three, and it is the manner (and proportion) in which you use them that makes the difference.

I wish it were so simple as 30% reflection, 30% diffusion and 40% absorption, it isn't!

The goal, roughly speaking, is to get the audio to your ears in a coherent fashion, with as few "bad" reflections as possible.

The best way to do that is room geometry. I can't imagine any designer arguing that... which is all fine and good except that it is complex and expensive and just flat out doesn't happen except in the top tier rooms. So we are left with treating the room geometry.

I've slowly evolved my opinion from a rather rigid formula to an approach of just get it right. Any of the three tools will work in the front, on the sides, in the rear, or on the ceiling of floor. Some are more practical, so that's where you start. I find the idea of diffusion on side walls to be very attractive because it eliminates the need for significant room depth - if you place diffusors in the rear you need about 12 feet of space from the back of your head to the rear wall. Place diffusors to close and you'll hear immediately why it matters!

Now I need a new room project where I can try this<G>...


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## Nathanael Iversen (Dec 23, 2016)

wst3 said:


> I don't know the particulars, but those phase measurements would make me nervous.



Can you elaborate? I feel the opportunity to learn something coming on. Are you referring to my observations about variability in the very high end, or to the phase trace irregularities above the frequency response. If I can improve my setup with action that is less than wholesale rebuilding the room from scratch, I'm quite interested! 

The problem with it being "the best sound I've had in my space" is that it may not be "the best sound that I could or should have given my gear."


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## Nick Batzdorf (Dec 23, 2016)

> The goal, roughly speaking, is to get the audio to your ears in a coherent fashion, with as few "bad" reflections as possible.
> 
> snip
> 
> Any of the three tools will work in the front, on the sides, in the rear, or on the ceiling of floor



Well, we don't agree 100% about that.

I might have mentioned a few hundred times that the brain separates reflections from the sides from sound coming from the front all day long, no matter how reverberant the space. It's easy to pinpoint exactly where something is coming from wherever you are.

And since we've all decided it's better to listen to speakers in a room rather than an anechoic chamber or outdoors, why would you want to deaden the sides? That's the place to let the room be the room.

The same applies to coherence in general. Sure you want the speakers to be coherent with themselves, i.e. you don't put the tweeter 20' and the woofer 10" away. And for imaging, you want symmetry in the room if possible - but that's so the primary reflections are coherent with themselves, not with the sound from the speakers. Muffling the sides just isn't the best approach.

One of these days I'll leave this alone and let people believe whatever they want.


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## wst3 (Dec 23, 2016)

Nick Batzdorf said:


> Well, we don't agree 100% about that.
> 
> <snip>Muffling the sides just isn't the best approach.



Yeah, my previous post was a little bit lazy... while there are opportunities to use absorption on the side walls it is probably not the tool to reach for first. Our ear/brain is very good at identifying the location of a sound, whether we know it or not, side reflections in a room can mess with that, but absorption is not always the best way to resolve that.



Nick Batzdorf said:


> One of these days I'll leave this alone and let people believe whatever they want.



a day before I do, or a day after?<G>


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## wst3 (Dec 23, 2016)

Nathanael Iversen said:


> Can you elaborate? I feel the opportunity to learn something coming on. Are you referring to my observations about variability in the very high end, or to the phase trace irregularities above the frequency response. If I can improve my setup with action that is less than wholesale rebuilding the room from scratch, I'm quite interested!



At the risk of coming off as a complete jerk, I'm not sure I can explain it in a single (even lengthy) post, but I can tell you that the phase should not be crossing the 0 axis so often. I expect that some of the audible anomalies are phase related, and the phase shifts are almost certainly caused by the filters that are inserted in the signal chain. A single cross-over in a loudspeaker would not look like that.



Nathanael Iversen said:


> The problem with it being "the best sound I've had in my space" is that it may not be "the best sound that I could or should have given my gear."


And that's an important distinction. Work with it, learn what's good about it, and what's maybe not so good, and then fix those parts


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## Nick Batzdorf (Dec 23, 2016)

By the way, I have to look into diffusion on the sides more. Manny LaCarruba was very specific about the depth and everything.


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## Nathanael Iversen (Dec 29, 2016)

wst3 said:


> At the risk of coming off as a complete jerk, I'm not sure I can explain it in a single (even lengthy) post, but I can tell you that the phase should not be crossing the 0 axis so often. I expect that some of the audible anomalies are phase related, and the phase shifts are almost certainly caused by the filters that are inserted in the signal chain. A single cross-over in a loudspeaker would not look like that.



I took the time to play with SMAART and the DSP in the Genelecs and to see what I could learn. 

1) The DSP is not causing the phase shifts. I can turn it off and on using a button in their UI. The frequency response shifts (obviously), but the roughness of the phase traces in the midband doesn't change. That indicates to me that the phase measurement is distortion from comb filtering - it is literally the ripples in the frequency response expressed in time. I don't think I am surprised by this - Genelec would use linear phase filters - or do fancy math to get stuff to sum correctly, I think. Also, there are no filters active in the most damaged area - certainly it could be harmonic ringing, but when nothing changes with the DSP completely off, I don't think it is the DSP.

So what is going on? There are two things I observe after more playing around

2) I have a large desk. It is wide and deep. A look at the calculated impulse response is instructive:






In a perfect world, there would be the spike of the impulse, no ringing and a nice tail. What I see is a large and powerful reflection at 5.6-6.2ms. That works out to a path length difference of a bit more than half a foot. Playing with a laser measure, that is pretty much exactly the path differential to several points on the desk. Given that the desk is wider than the speakers are apart, and covered in gear - that is going to leave a mark - and it clearly does. This is in the category of "not going to fix it right now, but now I know". I'm not buying a different desk. I could raise the speakers higher in the air, and angle them to miss the desk more - which would involve reworking all the first reflection treatment, new speaker mounting, cables, etc. Lots of work, and at the end there will still be reflections from lower frequencies - I will have just shifted them. 

3) There's a modal thing going on that is big and low. With the DSP off, it is very clear. Sometimes it expresses as a peak, sometimes as a trough the DSP can't fix. In the sub-bass, it is 10db+ gain at ~33Hz and 67Hz. The series is benign at 135Hz, but there is a giant suckout at ~270Hz, and no amount of moving treatment around helps. It is not a reflection. The 33Hz exactly corresponds to my position in roughly the middle of the room, width-wise. Physics at work. Maybe something like the AAVA active traps would help, but they are a significant outlay. 

So, at the end of it, I have amazing monitors that I am very happy with. The desk I sit behind and where it is in the room cause me to get less than perfect response from my really great monitors (Captain Obvious checks in). To improve from here (bass traps in every corner, all first reflections treated, speakers carefully positioned and everything measured to "best fit") is going to be inconvenient and expensive. The law of diminishing returns steps in. 

The setup is very nice to listen to. Human brains are funny things and we don't perceive what the measurement microphone shows with fine smoothing. We certainly discern more than 1/3rd octave bands. At 1/6th octave the space is very nice with the DSP on. The DSP is pretty much tamping down 33Hz through 65Hz by almost 10dB, with a minor tweak holding down the bump at 2khz. I just don't have enough low bass trapping for the sub bass to be correct in my room. 






Thanks for the great dialog and the encouragement to go after it a bit more. There is always more to learn, and this will not be my final setup! If you have any other thoughts I am certainly listening. I appreciate your experience on the forum.


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## muk (Dec 30, 2016)

If you are looking for an inexpensive microphone here is an interesting option:

http://shop.hifi-selbstbau.de/produkt/elektret-mikrofon-kalibriert-unter-0-und-90/

It's only 40€, and it's individually calibrated. That second part is rather important for measurement tasks. You get a correction curve for your individual mic, not just a generic one for the mic model. In REW you can import that correction curve, and I'm sure other measurement software offers that option as well. Makes for a more precise measurement than more expensive but non-calibrated mics. If you can spend a bit more you can also buy an individually calibrated ECM-40 mic with preamp from that site.


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## Nathanael Iversen (Dec 31, 2016)

Nick Batzdorf said:


> By the way, I have to look into diffusion on the sides more. Manny LaCarruba was very specific about the depth and everything.



This is an interesting topic. I grabbed my copy of Floyd Toole's "Sound Reproduction - Loudspeakers and Rooms" off the shelf while I was re-measuring my space to read up on phase and its audibility. As with most interesting books, I didn't read just that one bit, but also read up on first reflections. There is compelling literature to state that humans prefer to listen to stereophonic reproduction without damping the first reflections points. That said, the overwhelming preference of audio engineers is to work in a space with first reflections damped. He also quotes research that shows that many musicians are up to 7-9x MORE sensistive to changes in reverberation than average listeners, and so, may prefer to have the room "less lively". But the studies he quotes indicate that people generally prefer to do pleasure listening in a space with undamped first reflections points - including audio engineers listening at home! This is discussed at length with references to over 30 years of academic studies on pg. 99 of the book. 

The book is 2008, and is heavily documented with relevant academic and scientific papers. It is an excellent survey of human auditory perception and what is known to date.


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## Nick Batzdorf (Dec 31, 2016)

Floyd Toole is not just some casual guy, of course.

The question is still which of the six first reflections - floor/console/desk, sides, ceiling, front, rear. Reverb - how live the room is - is a separate issue. You can make a room very dead with absorption/trapping just on the front.


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## wst3 (Jan 1, 2017)

Read everything Floyd has written, and while you are at it, everything Philip Newell has written as well. Too bad they don't agree on everything<G>...

So what to damp and where?

I think many engineers prefer fewer reflections, and especially first reflections, because it provides a sound closer to what they'd hear in the studio proper, and thus allows them to treat the tracks more accurately, although accurate is not the exact word I'm looking for. And a big part of that is the engineers that trained us, and probably the engineers that trained them. 

Ultimately it is an issue of personal taste (and Toole is in the minority investigating that), and training/experience. Within reason, if you know the monitoring system you are using well (warts and all) you'll have an easier time getting good results.

You can swing things in your favor - at least that's my belief - with room treatments.


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## Piano Pete (Jan 7, 2017)

For DIY diffusion panels, does the dimension of the room dictate the design of the panel? I currently have absorption situated on the reflection points to the left, right, above, and behind my sitting position, in addition to some additional absorption along the walls as there was some high ring after I started treating the low end with bass traps on the speaker side corners. I am wondering if replacing my absorption panels (several 12"x12" squares of 4" to 2" thickness) with diffusers would be worth wild. I have found several DIY methods, but do I need to find one as tailored to my room as possible? I have found some designs that diffuse certain frequencies more than others, but nothing specifically mentioning how many I can place, or if they are for specific sized rooms. If the size doesn't matter, I can make several and place them next to each other to try to dampen the effect of my parallel walls.

Here are two of the sources I have found:

http://www.audioundone.com/do-it-yourself-acoustical-treatments

http://arqen.com/acoustics/acoustic-diffusers/


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## Nick Batzdorf (Jan 7, 2017)

My knowledge of diffusors is woefully lacking, other than that the design isn't arbitary. But in my opinion you have the absorption in exactly the wrong places (except possibly overhead - it's okay there), so I'd say yes, that would be an improvement.

How are you hearing the high ring, i.e. are you clapping and hearing pinging? That's bad if you're recording, but your speakers can't excite reflections like that.


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## Piano Pete (Jan 7, 2017)

What would you be your opinion Batzdorf?

The current placement of my treatment has been based on the recommendations of Auralex. From what I have added to the room, it has made a big difference. Auralex also suggested trying to decrease the symmetry of my room, a giant bookcase full of scores helps, and recommended possibly adding diffusers -- hence my previous question.


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## jcrosby (Jan 7, 2017)

Personally I would avoid Auralex, both their products and their advice. They're incredibly overpriced and have made a killing selling cheap foam as "bass traps." Foam can't absorb bass period... You need either mass or tuned absorbers to address low end.

Anyway... although a book case will scatter the sound it's not the same as a diffusion. Decreasing symmetry is generically bad advice... If you're not building an actual space designed by an acoustician you're better off with symmetry and strategically positioned treatment... The bookcase line is total BS. You're way better off absorbing your rear wall depending on the size of your room, and in your average home studio setup, (if it's a bed room converted into a music space), it's the better choice.

Diffusion scatters the sound in mathematically predictable ways and targets specific frequency ranges. Like speakers, placement is important and it really depends on the room. (My room for example is too small for diffusion to be effective on the rear wall, a common place for it...) The only option for my space is to absorb. As for Auralex, most of their diffusors aren't truly quadratic, the few that claim they are are way to expensive for the quality you get, and a few of them are polystyrene. Diffusion should be rigid, let alone think of how much their financially raking you over the coals by selling you expanded foam for a couple hundred bucks...

The point is you don't just diffuse for the sake of it being an acoustic treatment, the shape and size of your room determine what kind of treatment is most effective in your space.

 This guy has a great explanation about mass and low energy absorption... the main point about this is IMO Auralex is marketed crap. Their stuff is fine for upper mids and highs, but they've deliberately mismarketed low end treeatments and I would avoid their advice and hop on to GS...)


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## Piano Pete (Jan 7, 2017)

Thanks for the comment and video! I went on to watch the second part. Pretty much what he said is how I have set up my room. While I did take advantage of Auralex's advice, I did not use their products. I agree with you, they are expensive. I also used other resources and books to figure out what to do with my room. I cant say that what I have done was a waste, as my room's response has become much flatter than before; most notably, I have been able to tame the low frequencies. My goal is to eventually get higher quality treatment down the road.

With treating my room, I was not really thinking about diffusion, as I have heard that absorption for home studios tends to do the bulk of the work. It was a comment during a discussion with a friend that resulted in me looking into it more. As both you and Batzdorf stated, I know that diffusers work very precisely. After this, I do not know anything about it. I'll definitely continue doing my homework on the matter!


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## Nathanael Iversen (Jan 7, 2017)

Diffusors have to be DEEP to diffuse even the low midrange well. The math is all very complex, but we musicians don't have to do it. That said, quality quadratic diffusors that go low are not cheap. Alton Everests book, "The Master Handbook of Acoustics" has excellent explanations. Great summary of the space without the post-calculus mathematics that is actually involved.


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## Nick Batzdorf (Jan 8, 2017)

I actually like Auralex' products when they're used properly, but last time I heard their president Eric Smith's advice was in the late '90s when I was the editor of Recording magazine. His advice for monitoring rooms was to deaden everywhere, under the thinking that the best sound was directly from the speakers and everything else in the room made it go downhill from there.

He may have changed his mind since then, but I disagree. The room adds a lot to the sound, which is why we don't mix in anechoic chambers.

jcrosby, I have a different philosophy, which I've posted a lot: soak up extra reverb at the front of the room, trap bass if necessary, and leave the sides bare. Of course room ratios are also important, but that basic design will help any room regardless of size.


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## jcrosby (Jan 8, 2017)

Nick Batzdorf said:


> I actually like Auralex' products when they're used properly, but last time I heard their president Eric Smith's advice was in the late '90s when I was the editor of Recording magazine. His advice for monitoring rooms was to deaden everywhere, under the thinking that the best sound was directly from the speakers and everything else in the room made it go downhill from there.
> 
> He may have changed his mind since then, but I disagree. The room adds a lot to the sound, which is why we don't mix in anechoic chambers.
> 
> jcrosby, I have a different philosophy, which I've posted a lot: soak up extra reverb at the front of the room, trap bass if necessary, and leave the sides bare. Of course room ratios are also important, but that basic design will help any room regardless of size.



My room's a uniquely weird scenario. I have a two story loft and the only option for me is to work in the second story which is an open loft looking down into the living room.

It's open on one side for about half the length of the space. (Basically I have 3 walls and a half wall...) I had to convert it into a closed room. On top of that it's a 'sideways' A-Frame only 7 1/2 feet wide... Basically it's an acoustic nightmare. I get insane flutter echo that sounds like you're inflating a football 

Any inkling of leaving the room intact made the flutter echo even more apparent in areas that weren't absorbed. And because it's narrow with a uniquely weird ceiling I had all kinds of room modes going on and had to go heavy on the bass absorption as well...

I spent a lot of time researching while building the space and treatment. Overwhelmingly the consensus I found was that for small rooms, (especially a-typical spaces), absorption is much more effective. And as I started hanging panels I found it was true, at least in the case of my room... (Interestingly, one of the acoustics companies I consider to be leading the pack in terms of acoustic technology found sidewalls to be one of the most critical areas to absorb in small studios. In my room I found this to be totally on point...)

Case in point I had 12 inch traps (Part 703 part 705, roughly the density of 18 inch 703) in all corners and along the rear wall. I have about a 14 inch gap between the traps and rear wall for more efficient bass absorption.

I also converted my crawl space into Low Frequency an 'absorber' using peg board and 703. (There's a great segment by Dennis Foley from Acoustic Fields about open window being an ideal 'absorber' - in the sense the low frequencies decay and don't return. I found a few guys on some acoustics forums who did this and found it to be very effective in managing low end... So far I can't complain about the low end in my room. I can hear a 40 hz sine wave with no a sub like it's sitting right in front of me...)

I have a false front wall with about 6 feet of space between the physical front wall, (and an opposing crawl space also with the peg board/703 cover on the physical front wall. (The room is about 20 feet long. Ideally it would be the other way around; 6 feet in the rear and 14in in the front but due to the height of the ceiling and where the peak of the A-Frame is that isn't an option...)

After that I hung 705 panels on the ceiling above the listening position and walked around the room doing the 'clap' test. The flutter echo was still really bad, even from the listening position.

I added panels from the center to down the first half of the rear ceiling. (The ceiling is a-symetrically longer in the back.) Still insane flutter echo...

I rinsed and repeated down the last section of the ceiling and still echo....
Even as I put panels along the side the echo was still somewhat audible from the listening position and it didn't go away until I had run panels all along the side walls...

In the case of my room, (and the consensus from a few well regarded acoustic engineers) often absorption is an excellent solution in a small room. It may not be the best solution for everyone, but is best for my space... I am going to build some Quadratic panels this summer and see how they work out in my space but really won't know until they're in there... I'm just too curious not to see how it turns out... I have hunch I'll prefer the way things are but am hoping to be pleasantly surprised.

I'll also say that despite claims of it being unpleasant to mix in a fairly dead room I find it to be pleasant working in here. High end in no way feels "sucked out of the room" like some people claim. I actually find the opposite. High end is really clear and detailed, just not fatiguing or blurry, and the psychoacoustic effect of audio 'moving back', or 'behind the speakers' when adding reverb is more pronounced. I basically have a clearer picture of the 3d sound stage than any room I've had previously...

With all that said my room is an anomaly... It's not typical of just about anyone else's room... But I do support the approach that on average absorption can be the better solution in a smaller room... but every room is different and mine is particularly a-typical...

About Auralex... I'm not saying it's is useless, it's fine for absorbing flutter echo in your average room, but I do question their integrity when they market expanded foam as 'bass traps'. And I do think their products are overpriced when compared with tried and true acoustic solutions since durability is a huge part of the equation...

Anyway, this is what I had to work with...







And this is what I ended up with...


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## Nick Batzdorf (Jan 8, 2017)

That is a tough space with unique problems, no question. The only part I'm not onboard with is the idea that you have to soak up everything in small rooms - at least not categorically. Now, I've been in small rooms that used ASC Tube Traps - or something like that, possibly Attack Wall? - all around, with the monitors in the "wall." That's certainly a workable approach, in fact some people like it... which is the X factor: people have different tastes.

Anyway, I think you're talking about that triangle thing they sell as a bass trap. Is it called LENRD? I have one in my garage, the one that's skewered on a mic stand. Yeah, it isn't really a bass trap, you're right, although it works very well for voice recording just as absorption behind the mic.


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## Nick Batzdorf (Jan 8, 2017)

The room looks nice in spite of that, by the way.


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## jcrosby (Jan 8, 2017)

Nick Batzdorf said:


> That is a tough space with unique problems, no question. The only part I'm not onboard with is the idea that you have to soak up everything in small rooms - at least not categorically. Now, I've been in small rooms that used ASC Tube Traps - or something like that, possibly Attack Wall? - all around, with the monitors in the "wall." That's certainly a workable approach, in fact some people like it... which is the X factor: people have different tastes.
> 
> Anyway, I think you're talking about that triangle thing they sell as a bass trap. Is it called LENRD? I have one in my garage, the one that's skewered on a mic stand. Yeah, it isn't really a bass trap, you're right, although it works very well for voice recording just as absorption behind the mic.



I'm not saying you should to soak up everything, not at all... In the case of my room I basically did though...

Even when I had all side panels up except one, when I stood at the corner of the opposing wall where the last panel went I still had that pinging flutter echo. (I'm not joking when I say it sounded like inflating a football. It was really bad...) If I had a wider longer room I'd have probably done live end dead end with diffusion on the back... (When I build the diffusion panels this summer I'm going to see how they do in the rear of the room 1st and then move them around and see if there's a sweet spot for them. Hoping so...)

And thanks Nick. I spent 3 months, all the moneys, and got carpal tunnel and tennis elbow doing it 
That's why I say only DIY if you're a masochist...

I'm not saying all Auralex is useless, most of us have had it on the walls at some point... It's only since people have gotten hip to building DIY absorbers have they finally started to modernize their line to have some honest solutions... Their prices though! Through the roof when compared to someone like GIK... Their Quadratec is $700, a QRD the same size from GIK is $260...


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## wst3 (Jan 9, 2017)

Piano Pete said:


> What would you be your opinion Batzdorf?
> 
> The current placement of my treatment has been based on the recommendations of Auralex. From what I have added to the room, it has made a big difference. Auralex also suggested trying to decrease the symmetry of my room, a giant bookcase full of scores helps, and recommended possibly adding diffusers -- hence my previous question.


I'm not Nick, but I am very concerned that Auralex recommended decreasing symmetry, I haven't seen your room, but I can't think if a single case where reducing symmetry would be a good idea. Left/Right symmetry is critical, front/rear symmetry not as much, and they may be using the term in a manner I'm not familiar with.

Once upon a time Auralex had a world class acoustician on staff. You could trust any advice he provided. He is no longer there, he moved on to an A&E firm... can't blame him!

There is a ton of good information in print and online - you have to do some sifting online. There are no fail-proof formulae, there are probaby hundreds of really bad ideas, and a couple dozen good ones, which of those works best in any given room requires experience or experimentation (which is how one gains experience<G>!)

My experience, worth about what you are paying, most rooms require some absorption, some diffusion, and even a little reflection/re-direction. Room geometry is still king, but most of us are not in a position to do a lot with that. Room construction comes in a close second, but again not always an option. After that it is room treatment, and you can do wonders with the tools (absorption, reflection, and diffusion) at hand. Keep in mind that absorption and diffusion can be wide band or narrow band. In general (huge reach here) you will have fewer problems with broadband treatments. The exception (and there is always an exception) is bass trapping, if you need it you should probably take a look at tuned traps.

Last thought - Peter D and company are brilliant, and their diffusors work really well. But at a cost! You might want to look at poly-cylindrical diffusors as an option. And believe it or not, the bookshelf loaded with books can provide a reasonably random diffusion effect, it will also provide some absorption.

Please let us know what you do, and how well it works!


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## Nick Batzdorf (Jan 9, 2017)

> when I stood at the corner of the opposing wall



That doesn't necessarily matter. It's the listening position you're concerned with, or really the speakers in your listening position (i.e. you can clap your hands and hear pinging across the side walls, but your speakers can't excite that).


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## Piano Pete (Jan 9, 2017)

I have rechecked the information provided to me by Auralex, and the comment regarding symmetry had to do with the dimensions of my room, its a box, one of the other suggestions was to open up a closet along the back wall to artificially alter the length. At this point I do not know how valid this comment was. I have read about doing this to resolve some issues on some other forums.

Anyways, this thread has been great.

For all the information I have seen going back and forth on whether the DIY fiberglass panels work, do they?


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## Nathanael Iversen (Jan 9, 2017)

The DIY fiberglass panels out of Owens Corning 703 or similar are essentially identical to many pre-made panels. Look at GIK Acoustics. I used their products for my room. For the price, I was not interested in trying to make them. It is not hard, but theirs are professionally finished, and all I had to do is hang them.


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## wst3 (Jan 10, 2017)

Thanks so much for clearing that up - Auralex is an odd company, but I've never known them to dispense incorrect advice - questionable sometimes? Yes. Focused on sales of foam? yes... but at least it has never been blatantly incorrect.

To your next question - depending on the location and size of the closet that could work. Also look for information on "loosely coupled spaces" - a neat 'trick' that can enhance the effect, if the stars align. Russ Berger was the author, I think.

And lastly - sound waves in air do not care what they run into, foam, fiberglass, your 100 pound German Shepherd... makes no difference. What does make a difference is the efficiency (with respect to space) of the absorber, but that only matters to us humans. Rock wool and fiberglass happen to be reasonably efficient. They work quite well, you still have to get placement right...

If you are handy with some basic tools (and glue) they are very simple to build, and very cost effective. Having built a few over the years I've discovered that no matter what I do I still end up with the itchies - so my next panels will likely be purchased (unless the cheap in me decides to give ONE more try!)


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