# Low frequency acoustic diffusion



## Jeffrey Peterson (Sep 14, 2013)

I just moved and am designing my new studio downstairs. Auralex is taking forever to respond with a free analysis of my room so while I wait I was wondering about low frequencies and diffusion products.

In my last work space I had major hot and null spots from 60Hz to 200Hz. In my new studio in the basement I have a hot spot in the middle of the room and a null spot right where my listening position is. I will be buying about $1000 worth of acoustical treatment. Currently I have 4 Lenrd bass traps and 4 2' x 4' x 2" wedges foam from auralex, but have not put them up in the new work space yet.

I was quoted by a couple of acoustic professionals at $3000-$4000 to help me treat my room, and that isn't including the materials so at his point I can't afford that.

QUESTION A. Do Lenrd bass traps help with hot and null spots for an even mix in the bass zone? For example bass traps going from each corner floor to ceiling. My impression was that absorption is only for slap and echo problems, but I could be wrong.

QUESTION B. If diffusion is the only way to treat hot and null spots in a room then what are some low frequency diffusion products? Auralex T'fusors only diffuse down to 800Hz maybe lower if you had insulation in them but not in the critical 60Hz to 200Hz range. Can someone suggest a low frequency diffuser? Wave lengths are 10ft long at 100Hz and from what I've learned so far you need a 1/4 of the size the wave length you are trying to diffuse in treatment. So 2.5 ft would help with 100Hz lengths?

Thanks for any help, I will be mixing with Focal Solos.


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## Oliver_Codd (Sep 14, 2013)

Jeffrey,

The auralex won't do much for the lower frequencies. That stuff is better used to eliminate flutter echo from frequencies in a higher range. Diffusion won't do much for the lower frequencies either. I would recommend broadband absorption. Check out GIK acoustic or Real Traps. They both offer great products and free advice on how to treat your space. If you're really tight on money, broadband bass traps are fairly easy to make on your own. Fill the corners, back wall, and early reflection spots for a starting point. Add diffusion later to liven up the space a bit.


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## FriFlo (Sep 15, 2013)

With the lack of detail you give it is impossible to give any hints. Take a look at john Sayers studio design forum to get a grasp of what you have to analyze and explain first, before anyone can help you in any meaningful way. With $1000 You will only get so far, however. Build some diy Absorber Panels and super chunks for the corners. Any acoustical Treatments by companys like auralex will Not work, as you will need more money to get the amount of products necessary. Hence, DIY is te only option


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## wst3 (Sep 15, 2013)

The good news is that you are just now starting to design the space! Now is the time when you can get the largest impact for your budget.

The maybe-not-so-good news is that your budget may not be sufficient, and at the risk of sounding a tad nasty, it appears you do not have a firm grasp of how to treat a small critical listening space.

More good news... you can learn this stuff, it is basic physics, not rocket science, and the math required is minimal.

From my perspective - being both budget constrained and having build a handful of studios - DIY is a good option, but it requires tremendous patience. The other option, of course, is to secure the services of someone with the required experience, but I'm pretty sure that would sap your entire budget.

So it comes down to the age old triangle, quick, cheap, good - pick at most two.

I'd vote for cheap and good, which means DIY. There are three compelling reasons to do it yourself:
1) it's cheaper
2) you can get a great result
3) you'll know why foam products are not effective at low frequencies, and why you might choose diffusion, reflection, or absorption for any given problem.

To help you through the morass of really bad advice that exists out there I would suggest that you start with some fundamentals.

Learn how sound behaves in an enclosed space. This means learning to translate frequencies to wavelengths - it's a real eye opener!

Learn how each of the three tools (diffusion, reflection, and absorption) affect the sound in the room.

Learn how placement (monitors AND ears) can affect the use of the three tools.

Do NOT believe anyone that tells you a single tool or approach will work. Any single tool or approach may solve one problem, but it will not solve them all.

Learn to make measurements in your space. While there are really good tools out there that make measurement a snap, you can get meaningful measurements with stuff you already have. Capturing the information is trivial, understanding it is not.

Learn that you must take into account Energy (NOT amplitude), frequency, and time. And from this learn why you can not solve problems in one domain from an alternate domain.

Seem like a lot? I guess it is, at first, but if you can learn to play music you can learn (in time) how to treat your studio.

Sayer's web site is excellent, but some of the conversations there wander a bit, and can be confusing or even disconcerting. I'd suggest that you visit that site after doing some other reading.

There are excellent white papers and tutorials available on the web. Once again you need to somehow sift the wheat from the chaff. I wish there was an easy way to do that<G>!

Google some of the following folks for a starting point: Peter D'Antonio, Richard Heyser, Malcolm Chisolm, Wes Lachot, Jeff Syzmanski and Eric Desart - no particular order! Follow the links that they provide for more sources.

I hope you do not find this to be discouraging!


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## Oliver_Codd (Sep 15, 2013)

Awesome post *wst3*!! Couldn't have said it better o-[][]-o


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## Nick Batzdorf (Sep 15, 2013)

That budget may not be enough if you want to use commercial acoustic products to make a dead room.

But I'll say the same thing I always say: hard, flat sides; soak up excess reverb at the front of the room; diffusion at the rear and overhead if you want it; and bass trapping anywhere except the hard, flat sides. white papers tend to say what Auralex will tell you: muffle everywhere, and I disagree with that.

And my advice is to concentrate on your listening position, not on what's going on anywhere else in the room.

The LENRDs are those foam wedges, right? I have a couple of them. They're very good absorbers, but they're not really bass traps.

If you want a one-size-fits-all commercial product, I like - and use - the baffles from the ASC Mix Station:

http://www.acousticsciences.com/products (last picture bottom right - scroll down)

But not the way they have it set up. Ideally I'd want just the front wall covered with those baffle assemblies. The side ones are all wrong - I believe in hard, flat sides, as I said.

Now, I have a window in the front of my room, so I have them on the sides, but I'm well back from the front wall, and my speakers are near the end of those side baffles and pointed in so the imaging is not affected.

The reason I like that particular product is that it's both broadband and bass trapping. Its stiff fiberglass panels (about 1-1/2" thick) flex to catch bass, plus the spaces behind the panels are tuned with those fins you see sticking out, plus the panels are absorbent themselves.

They work very well. And you could make something similar.


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## wst3 (Sep 15, 2013)

Nick's approach can work, but not at your budget, and not without either understanding why it can work, or hiring someone that understands why it can work.

No disrespect to Nick (he knows that) but again I have to underscore: do not listen to anyone that offers you an off-the-shelf, one size fits all solution. It works for them, great, but it may not work for you... it probably won't.

Definitely check out Malcolm Chisolm if you want a little insight into why Acoustic Sciences stuff works as well as it does. Also read everything on their web site... another trusted source that I left off the list (it's actually a long list!)

Probably the most important part of Nick's post:

"And my advice is to concentrate on your listening position, not on what's going on anywhere else in the room. "

That can cause problems, but they won't be huge problems.


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## Oliver_Codd (Sep 15, 2013)

I believe Bill mentioned speaker placement already, but I wanted to quickly bring that up again. I couldn't believe how drastically things would change just by shifting my monitors a few inches one way or the other. I was able to fix a lot of my serious bass problems just by moving them around and taking measurements. It's a pain, and takes time. but it's totally worth it. Good luck!!


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## Nick Batzdorf (Sep 15, 2013)

"My" approach - I wish I'd invented it - is an inexpensive way to make a room usable. Of course you want to have a goal when you do anything; it makes zero sense to "buy room treatment" just because products are available.

But I actually do believe those ASC baffles in the right place will help any room that doesn't already have something else performing the same functions (getting rid of excess reverb and trapping bass).

And to tell you the truth, it's hard to imagine how anyone could go wrong with, say, a mattress on the front wall. It might look like hell and I'm not necessarily recommending it, but you get the point: there are certain things that pretty much every small room benefits from. Broadband absorption in the front and bass trapping (broadband bass trapping) are in that category.

What's complicated is the final 5% that makes the room fantastic rather than just workable.

And absolutely do experiment with speaker placement. Measuring can open up a can of worms if you only know enough to be dangerous - and I put myself in that category when it comes to acoustics...after having read a whole lot about it and experimented over the years. The reason is that the measurements change a lot from inch to inch. But speaker placement is very important.


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## Nick Batzdorf (Sep 15, 2013)

I want to offer one other opinion: a lot of people tend to sit too close to their speakers for my taste. The theory that you're eliminating the room is bankrupt; yeah you hear details and great imaging from nearfield monitors, but they sound just isn't right when you're right up against them. You need some room influence for them to sound right.

My opinion only - lots of people disagree, and that's fine because it's just a matter of preference.


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## Jeffrey Peterson (Sep 17, 2013)

Thank you everyone for your input. I've decided to use the DIY using (7) 2' x 4' x 6" for the corners and (9) 2' x 4' x 3" for every where else. Its a 18' x 11' room. The material will be Roxul Safe n' Sound with wood frames. 

The (7) 6" bass traps(just panels) will obviously have a gab in them and the (9) 3" panels will have about 2" - 4" between them and the wall.

My room is about to get a lot smaller.


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## Nick Batzdorf (Sep 17, 2013)

You're going to cover the entire room?

Ouch.


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## gsilbers (Sep 17, 2013)

not sure if it helps but you might want to look in ebay since there are smaller companies selling there that would otherwise be hard to find. 

http://www.ebay.com/sch/i.html?_from=R4 ... aps&_rdc=1

there is one company ..i forgot the name.. but its ex-auralex employees who opened up their own shop. 

besides that... my own opinion, which i know it goes against all established audio engineer/musicians in this and gearslutz forum, but i dont think auralex or other high end acustic treatment co. are doing anything special other companies are. 

i bought myself $100 worth of acustic foam (almost the same NRC than auralex) from an ebay store and i can almost cover my whole room. that would be 8 bass traps and 28 big 1inch depth panels. 
with double that i can cover all the room. 
now, how would that compare to having the same with auralex? dont know. maybe not as good, but its a home studio and it did make a big difference. 

i know theres problably something thats makes this foam not good, but i didnt see/hear it..and im happy with what i got...
so just for sake of helping those non haters with a low budget 
here is the store i bought mine from . (fyi-these are not the ex-auralex employess)
http://www.foamexpress1.com/Acoustic_Sound.php (bottom of the page has the acustic info)
also check on the link on the side that have bass borders and design foam.
and the ebay store:
http://www.ebay.com/usr/foamexpress
and here are the auralex data sheets:
http://www.auralex.com/testdata/

hope this helps not only the OP but anyone else lurking by 
0oD


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## Jeffrey Peterson (Sep 17, 2013)

Nick Batzdorf @ Tue Sep 17 said:


> You're going to cover the entire room?
> 
> Ouch.



What do you mean "ouch"? Price wise? DIY is probably going to be about $300.


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## Nick Batzdorf (Sep 17, 2013)

Soundwise.

Ouch.


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## Jeffrey Peterson (Sep 17, 2013)

Thanks for elaborating in such great detail on what you mean Nick.

No it will not be covering the whole room, there will still be way more dry/paint showing than acoustic treatment.


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## stevetwist (Sep 18, 2013)

If you're interested in getting a better grasp over the physics of acoustics, and have a basic capacity for physics and mathematics, the book "Master Handbook of Acoustics" by F. Alton Everest (currently 5th edition) really helped me understand the discussions of other people on the internet with regard to acoustic treatment:

http://www.amazon.com/Master-Handbook-Acoustics-Alton-Everest/dp/0071603328/ref=sr_1_1?ie=UTF8&qid=1379520794&sr=8-1&keywords=master+handbook+of+acoustics (http://www.amazon.com/Master-Handbook-A ... +acoustics)

The chapter on diffusors was particularly enlightening, as it clearly illustrates the different algorithms for calculating the specific height sequence a Schroeder diffusor needs to follow in order to be effective (and which target frequency range it will be effective for). Reading that chapter, I feel I could quite easily build my own diffusor using basic materials from a hardware store.


I'm starting to think about treating my bedroom studio, and so I've been reading as many resources as I can on acoustic treatment. Another book I read, targeted at the DIYer, is Sound on Sound Magazines' "Studio SOS Book". I can't testify to the effectiveness of the treatments suggested (I haven't tried them out yet!), but some (if not all) of the physics seems sound (forgive the pun!), and their treatments are very cost effective.


I'd hope to be able to provide more insight once I've begun working on the treatment of my room, which is very much going to be a budget DIY job (as that's all I can afford, really - plus, doing it yourself is way more fun, if you ask me!).


Best of luck with your room treatment,
Steve


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