# Acoustic Theory



## JonFairhurst (Jul 8, 2015)

I'm interested in recommendations on books/papers/websites on acoustically treating rooms.

I'm remodeling a daylight basement as a multipurpose AV, music, whatever room. It's roughly 25 x 15 x 8, which isn't far from dimensions of 3x2x1, which would be terrible. At least it's not a perfect cube...

I've just added a wood floor. The room has some small windows and a sliding glass door. With the bookshelves removed it's a real echo box.

I've purchased some Corning 703 panels and will use burlap covering as a design element in the room. I will also be building in some new bookshelves, which work great as diffusers and bass traps - simply pull the books out from the back a bit to leave space and stagger them to diffuse the sound.

The thing about the 703 panels is that I'm not sure how many would be optimal. Use none and the room is too live. Surround yourself in them and it's too dead. So what's the correct balance?

Anyway, this is for a residential room and it's a budget, DIY project. I don't need perfection here, but I'd rather be a bit more informed so that I'm not just randomly adding treatment and saying, "hey, that sounds better. Well, maybe..."

Thanks in advance!


----------



## Hannes_F (Jul 8, 2015)

This
https://www.gearslutz.com/board/studio-building-acoustics/


----------



## sleepy hollow (Jul 8, 2015)

JonFairhurst said:


> I will also be building in some new bookshelves, which work great as diffusers and bass traps - simply pull the books out from the back a bit to leave space and stagger them to diffuse the sound.


That's not how you build diffusers. The books will absorb some sound energy in a certain frequency range - that is the opposite of what a diffuser is supposed to do. Also you'd probably have to cut your books into shape, depending on what kind of diffuser you want to build. Here's a good article: http://www.gikacoustics.com/how-diffusion-works/

Also, a simple bookshelf isn't a bass trap; it can be turned into one, though. You'd need absorptive material (similar to the Owens Corning panels you mentioned) and proper placement. What is your plan regarding the bass traps?


----------



## wst3 (Jul 9, 2015)

good for you!

depending on your level of experience and education you might be able to skip a couple of these, but what the heck, they are all good reading!
_
Don Davis et. al. - *Sound System Engineering* - any edition will suffice. This is by far the best introduction to the foundation of sound systems available. Obviously the later editions cover the most current thinking,but the book is really meant for system designers, for which the basics have not changed.

Philip Newell - the guy is almost as prolific a writer as he is a designer.
- *Project Studios* - read this first, read it a few times!
- *Recording Studio Design* - a lot deeper, but you'll learn a lot
- *Recording Spaces* - really esoteric stuff
- *Studio Monitor Design* - you probably won't design your own monitors, but read it anyway
- *Loudspeakers *- not specifically about recording studios, but a good read

Jeff Cooper - *Building a Recording Studio* - a remarkable book, slightly dated, but covers the foundations of building a room specifically for critical listening

Michael Rettinger
- *Acoustic Design and Noise Control* - a great source, even as old as it is, on noise control
- *Studio Acoustics* - old but still a ton of really good information
- *Applied Architectural Acoustics* - might not be useful for studio design, maybe put it on the bottom of the pile

F. Alton Everest - *Master Handbook of Acoustics* - an old standby. I have an older edition, haven't gone back to it in a while, but at the time I read it several times.

Philip Giddings - *Audio Systems Design and Installation* - geared more for large scale installed systems, this book remains the best resource for power, grounding, and interconnection. There are sections that are a bit dated, and it is NOT a cookbook I'm afraid, but it is worth reading.

Gary Davis - *The Sound Reinforcement Handbook* - ignore the title, another great introduction to audio basics

Roger D'Arcy et. al. - *The Recording Architecture Book of Studio Design* - the history of recording studios, what more could you ask?

Bruce Swedien - *Make Mine Music* - ok, not specifically about studio design, but by far my favorite bio from an engineer.(I am biased, Bruce and I co-sysoped an audio forum before the web)

Rod Gervais - *Home Recording Studio: Build It Like The Pros* - I have mixed feelings about the first edition, and should probably get the current edition. Most of the hands on info is terrific, some of the more theory based chapters were a bit weak.

Trevor Cox and Peter D'Antonio - *Acoustic Absorbers and Diffusers* – really deep, really informative

Ken Pohlmann - *Handbook of Sound Studio Construction* - I have not read it in depth yet, but I like Ken as an author.

*Journal of the AES, June 1995 issue* - the standard for information about audio interconnections._

Where to start? That is a bit tougher, but I guess Sound System Engineering (Davis), Project Studios (Newell), Studio Acoustics (Rettinger), Building a Recording Studion (Cooper) and Audio System Design and Installation (Giddings) would be my first pass.

The other thing I recommend (to anyone that will listen): *read these books BEFORE you wander the world wide web. *These books have been thoroughly (viciously in some cases) peer reviewed, and revised, and they represent the best thinking. They are not as easy to read as a web forum, but they are the yardstick by which most forums should be measured. If you read and understand these texts you'll be in a great position to be able to sift fact from BS. Which is not to suggest that web forums do not have value, you just need the tools to be able to figure out

None of this is rocket science, but some background in math is really helpful. And you'll understand recording at an entirely new level!


----------



## Tanuj Tiku (Jul 10, 2015)

Great post Bill!

I have only read books by Philip Newell. He is also helping me build my studio at the moment. I have a thread going here as well.

Philip's book is amazing! I have learnt so much from it. 

Whichever book or design philosophy you may choose, remember that information about studio design on forums is mostly rubbish. What is more, you will find that any thread eventually spirals out of control with personal insults and nonsensical pseudo science. 

The people who have written these books have dedicated their lives to studio design and conducted years of research. They are also immensely experienced in this field because they have built many studios in different countries with varying climate. Hence, they have solutions to many problems encountered in building a studio. 

Before anyone says, oh well...I just need to make a basic room, I would like to add that if you just go by some half baked idea on forums or theories from friends, you are likely to entirely waste your money. It may make your room slightly better in some respects but it will also add a bunch of other problems altogether. 

Like Philip said to me once that the proper way to build a room for a teenage drummer or a superstar rock drummer is absolutely the same. It costs no more, no less. I am largely paraphrasing here!

It is a science. People's need or understanding may have changed over the years but the physics does not change.

I understand this is a DIY project and that you do not wish to spend a lot of money but read any one of these books and whether or not you have the budget, you will surely have a better understanding of acoustics. I am sure, whatever you do after reading the book will be better than what you were planning to do before.

Good luck!

Tanuj.


----------



## JonFairhurst (Jul 10, 2015)

Wow! Thanks all - with a special shout out to Bill for that comprehensive list.

I've done some initial reading, and it looks like my room has the potential to be reasonably good.

1) It has a hardwood floor, which is recommended - and now I understand why. It's better to reflect all of the frequencies than to use carpet and absorb only the highs.
2) I plan to suspend some panels with a small space between them and the ceiling. This appears to be the perfect solution. I'll use 705 there, which will reach all the way down to the expected 74 Hz vertical mode.
3) The room is reasonably large - about 3200 cubic feet - so it won't sound like a bedroom.
4) I'm setting things up symmetrically.
5) I can put an absorptive or diffracting surface across from every hard reflecting surface.
6) I've designed the built-in bookshelves/filing cabinet/desk on the back wall to be staggered, so I won't face a single, unified reflection. As shown, books aren't a true diffuser, but can do some dampening. I have some space available behind the shelves, in which I can add some fiberglass. I can even port it to make a Helmholtz resonator, if I get industrious.

As I'm not building a pro recording space, I don't need perfection, but it looks like I'll get a nice result without spending a ton of money.

Consider that the lower part of the outer wall is currently covered by some really horrid paneling. I looked at various espresso houses to see about alternative materials. Stone and metals (like copper sheet) are really expensive. Faux materials make trailer parks look classy by comparison. A local Starbucks uses burlap and some coffee houses use old coffee bags. As it turns out, burlap over 703 or 705 is acoustically excellent - and much cheaper than real stone or metal. So there it is!

I can't wait to get this together. The room is currently so boomy and echoey that I find it an unpleasant place to spend time. It's ironic. Previously, I had ugly carpet and a lot of clutter, and it was more pleasant to be in there then than it is now with no junk and with a beautiful floor. Acoustics matter!


----------



## wst3 (Jul 10, 2015)

Tanuj Tiku said:


> Great post Bill!


Thanks!



Tanuj said:


> Whichever book or design philosophy you may choose, remember that information about studio design on forums is mostly rubbish. What is more, you will find that any thread eventually spirals out of control with personal insults and nonsensical pseudo science.



That's not an entirely fair assessment... there are some really smart, very generous folks sharing their knowledge and experience on various forums. The trick is to be able to figure out who knows something, and who maybe doesn't, and the only way to do that is to study - there is, I'm afraid, no shortcut.



Tanuj said:


> The people who have written these books have dedicated their lives to studio design and conducted years of research. They are also immensely experienced in this field because they have built many studios in different countries with varying climate. Hence, they have solutions to many problems encountered in building a studio.



In a similar vein, there are some truly horrible books on studio design out there as well. "Believe nothing that you read and only half of what you see" (well, in our cases hear) is not a bad bit of advice. But if you read the books written by acknowledged experts (most of whom would shun the term expert) you'll be all set. 

Now I'm just waiting for Russ Berger, Chips Davis, and George Augspurger to write their books!


----------



## JonFairhurst (Jul 10, 2015)

Regarding online stuff, yeah, I'll mostly ignore the "some guy posted it" level of acoustic theory. 

That said, I felt that there was a lot of good information here: 
http://ethanwiner.com/acoustics.html#mhf absorbers

One person I respect over at DV Info noted a design approach of Live End / Dead End (LEDE) in recording spaces. The idea is to put absorption on one surface and reflection/diffusion on the opposing surface. Move the performer/mic to taste. This doesn't really apply to my situation, which is more of a control room (home theater & listening / mixing area), but it's an elegant concept.

I'll have LEDE for the floor and ceiling. That's the easy part. 

I'll have a staggered back wall which might help or hurt, but it's 25 feet or so from the front speakers, so it won't be the most significant factor in the sweet spot. I have some flexibility in how I treat the front wall to balance it. The side walls are more difficult. With high windows and a patio door - plus a staggered (but half a foot) lower wall, I can't get perfect symmetry or control all of the variables. I'll do my best to avoid opposing reflective surfaces and will try to balance the amount of reflection and absorption right and left. Decorative window/door coverings might help or hurt, and will be selected for decor as much as anything. Ahh, compromises...

I have an omni reference mic. I plan to do some testing before deciding on the bass traps. After the bookshelves, absorptive ceiling, and other treatment is placed within the physical limits, I'm afraid that the complexity will overwhelm the math (for instance, what will that stairwell do exactly? help? hurt?) Anyway, theory and seat-of-the-pants will only get me so far. We will see what the mic says...

Should be a fun ride. Painting starts this weekend. Next are the hardwood stairs. And then the fiberglass and burlap panels. One step at a time...


----------



## Tanuj Tiku (Jul 10, 2015)

Bill,
Sure there is some good information on some forums but you have to have a basic grasp of acoustics before you can decide who is saying something that makes sense. 

I am speaking from experience. Earlier I used to feel that so many people were gracious in sharing their views and were right on many parts, only to later realise that it was misleading or inaccurate. 

In any case, if one was serious enough to put in any money into a project, a good book would be the way to go not some thread on Gearslutz. 

Regarding the books, I was only reacting to your list. Needless to say there are a lot of horrible books written in any field.

Updated books are also an insight into new research and ideas that have developed further. LEDE is not the same as it used to be for example.

More and more studios are now going for an absorbent rear wall. Control room decay times are also reducing. 

It is a 'Control room' after all 

Forums are increasingly becoming misleading these days on specialist subjects.

Anyway, I am not an expert on this subject. Just sharing my views from what I understand of all this.


----------



## Tanuj Tiku (Jul 10, 2015)

What forums are good for is very specific advice. If you need an answer to something small quickly or you are looking for a direction or perhaps a way to get into something. 

I find that beyond a point, forums usually lack the necessary depth any subject would require to be discussed at length. 

This is not a criticism as such, just an observation. By design, forums can obviously not serve that purpose, neither do they exist for that.


----------



## Tanuj Tiku (Jul 10, 2015)

JonFairhurst said:


> I'll have LEDE for the floor and ceiling. That's the easy part.




Jon, 
I would check on that. I believe the LEDE concept is between the front and rear walls, not the floor and the ceiling.


Tanuj.


----------



## wst3 (Jul 10, 2015)

JonFairhurst said:


> Regarding online stuff, yeah, I'll mostly ignore the "some guy posted it" level of acoustic theory.





JonFairhurst said:


> One person I respect over at DV Info noted a design approach of Live End / Dead End (LEDE) in recording spaces. <snip>



LEDE(tm) is a pretty cool idea, although it never quite gained the traction I'd have expected. It works, but there are some fairly dramatic caveats. You need to learn to listen again, because (a) most of us aren't expecting to hear the recording space in the monitoring space, and (b) very few people have LEDE(tm) listening rooms<G>!

And there is a LOT more to LEDE(tm) design than just the dead front end and the live back wall. It is all about timing of reflections.



JonFairhurst said:


> I'll have LEDE for the floor and ceiling. That's the easy part.



That won't work - and I almost never say that. And actually, what I mean to say is it will NOT be an LEDE(tm) room.



JonFairhurst said:


> I'll have a staggered back wall which might help or hurt, but it's 25 feet or so from the front speakers, so it won't be the most significant factor in the sweet spot.



The distance from the back of your ears to the rear wall needs to be at least 12 feet, so you have that going for you. That does assume that you are using some kind of scattering treatment on the rear wall. But even with a reflective rear wall the distance is essential to maintain the proper relationships and timing for those evil (?) reflections.



JonFairhurst said:


> I have an omni reference mic. <snip>



I'd suggest that listening is probably more valuable than measuring unless you have the right tools, and understanding of how to use them, and some appreciation of what the measurements mean. You might want to be careful not to spend too much time measuring.



JonFairhurst said:


> Should be a fun ride. Painting starts this weekend. Next are the hardwood stairs. And then the fiberglass and burlap panels. One step at a time...



And that's the key - it should be fun!! So have fun!


----------



## wst3 (Jul 10, 2015)

Tanuj Tiku said:


> What forums are good for is very specific advice. If you need an answer to something small quickly or you are looking for a direction or perhaps a way to get into something.



There is only one forum that I trust completely - Synergistic Audio Concepts. It is not free, but it is not too expensive, and it is some of the brightest minds in audio.

Beyond that I can't really recommend any of the online communities.


----------



## wst3 (Jul 10, 2015)

Tanuj Tiku said:


> Bill,
> Sure there is some good information on some forums but you have to have a basic grasp of acoustics before you can decide who is saying something that makes sense.



That was what I was trying to say...



Tanuj said:


> Updated books are also an insight into new research and ideas that have developed further. LEDE is not the same as it used to be for example.



Actually, LEDE(tm) is exactly what it always was. It is a very specific set of criteria, and some suggestions as to how one might meet them.

There has been a lot of research since the 1980s, and there have been several new ideas about how to design a critical listening space - Reflection Free Zone, and Non-Environment to name but two.

None of them is a silver bullet.


----------



## JonFairhurst (Jul 10, 2015)

Thanks for the follow on discussion!

Yes, as I thought about it, LEDE needs to be between front and rear. Side to side makes little sense as that would upset the symmetry of the room. Floor to ceiling makes little sense, unless you plan to squat for more reflection and stand on tip toes for less. 

That said, I expect to have a reflective floor (hardwood) and absorptive ceiling (705) in my standard 92" tall room. That's probably the easiest decision in the project. The design will largely be aesthetic, with eight panels of 16x9 aspect (to mirror the display aspect ratio). The panels will be between wood frames that include lighting and they will be biased toward the center of the room, rather than the edges. To adjust things, I could replace some panels with 703 or with a reflective material behind the cloth. I'll study some of the recommended books before finalizing the details.

Anyway, with the ceiling panels somewhat biased toward the center of the room, that will leave space for bass traps without making them look pinched. I've seen some rooms designed for audio that didn't consider the visual aesthetics. I don't plan to do that. I want visitors to say, "beautiful room" when they walk in. If they don't notice the sound of the room, it probably means I did the acoustics right - especially if they say, "great sounding speakers" once the music or film plays.

And point taken about using ears above measurements. If it sounds wrong, it is wrong.


----------



## Mike Greene (Jul 10, 2015)

Everything that Bill said. And I see you posted again while I was typing, so I'm kinda repeating some of what you just said about aesthetics. :D I’ll add a few random thoughts:

If the room is boomy (as opposed to just being too live), then I would find that frequency now, before you add too much treatment. My guess is that that frequency will always be a bit of a problem (although not necessarily very noticeable) since it’s likely a function of your room dimensions, so you’ll probably want to build a Helmholtz resonator or two. Resonators are built for specific frequencies, so knowing what frequency it should be tuned to will be helpful.

Bookcases are great. I don’t think you have to get too concerned about their placements, though. Just put them and the desk where they make sense functionally. Personally I wouldn’t put absorption behind the bookcases.

Burlap is the traditional covering for 703, but I say the type of cloth doesn’t really matter. Get something pretty instead. And if it’s stretchy, it will be easier to work with. In L.A., there’s a textile district downtown where you can get cloth for a buck or two per yard. I’ll bet Portland or Seattle (I forget which you’re close to) has something similar.

703 comes in 2” thick bats. I always double them up for 4”, because it gives a bit better low end absorption. It costs twice as much this way, of course, but the low end will always be the toughest enemy, so it’s how I did my room, and the result is I don’t have that low end “whump” that some studios have. (I really love the sound of this room.)

Trial and error is your friend. I read all the books (there weren’t as many back then :D ) and they were definitely helpful, but ultimately it was my ears saying, “Hmmm, still a little live,” and then “Nope, now I’ve gone too far” and then finally, “Ahhh, here’s the porridge baby bear would like.”

For that matter, I would treat the room with an eye towards appearances and function, rather that trying to do some symmetrical or textbook design.

Just my thoughts, and definitely take with appropriate amounts of salt, since I have designed a grand total of three rooms in my entire life, so my experience is fairly minimal.


----------



## JonFairhurst (Jul 10, 2015)

Great tip about measuring the resonances now. There are a couple locations in the stairwell where I plan to add some 703. I'll probably do that first to keep it from whistling into the main room.

How do you recommend I do the test? One approach would be to put the mic in the sweet spot and to pop a balloon in each speaker location. I prefer this to a sweep as it takes the speaker response out of the equation. Any particular tools that you recommend?


----------



## Mike Greene (Jul 10, 2015)

The one time I had this happen, the resonance was really obvious. So I took a synth and made a short sine wave pop (like a kick drum), then slowly swept the frequency as I played notes until the resonance reared its ugly head. When I hit that frequency (99 to 100 hz), all of a sudden the boominess became really pronounced and it was like I was hearing an 808 boom from a rapper's car.

The cool part was that after I bought the books (specifically because of this problem) and learned about acoustics, mathematically that frequency is exactly what I should have expected, based on the room dimensions. So I built two big 4' x 8' resonators with holes drilled to tune to exactly 100hz and it was like magic how the resonance disappeared.

I would say that if your resonance isn't obvious enough that that method shows a specific problem frequency, then it's not a big enough problem to worry about, since the general treatment you're going to do will take care of most of it anyway.


----------



## JonFairhurst (Jul 10, 2015)

Sweet. Easy enough. And, yeah, it's not like the speaker response will come into play with this test. Isolating the frequency is very different from measuring a 20-20kHz frequency response.

I'm considering building panel traps into my rear bookshelf contraption. See 'Better Bass Traps' and Figure 7 here: http://ethanwiner.com/acoustics.html#better traps

This weekend I'll play around with some frequency generation to hear the results. I can predict the modes at 74, 38, and 23 Hz, plus their harmonics. The stranger stuff will happen at the stairwell frequencies. I'll scan these to see what I get. If I damp the stairwell, it's possible that these frequencies will get sucked out of the room - like a Helmholtz staircase.


----------



## wst3 (Jul 10, 2015)

fwiw, the stairs are probably not going to be a modal problem - they are irregular enough that they will actually break up modes.

You probably know this already, room modes become problems when they are not spread out evenly. This is usually the result of room dimensions that 'overlap'. Measuring is good, but you'll get really close with the standard calculations.

If you do want to measure Mikes tip about using your synthesizers is great.

Impulse responses are also great, but require software to transform them into frequency domain results. There are lots of cool tools that do this, but none of them are free.

Swept sine wave tests are great because they are nearly immune to room noise. There is also "Maximum Length Sequence" or MLSSA, also immune to noise, but a lot trickier to do.

Finally there are the 3-dimension tests, time vs energy vs frequency - aka TEF(tm). For smaller spaces you want a log sweep, and you have to remember that you are measuring energy, not amplitude.

Which is why, most of the time, I use a simple warble generator (Acoustilog Impulser, really cool), and my ears, or if I am having trouble an old fashioned oscilloscope. I do have a test set that does a variation on TEF, but frankly most studios are unwilling to pay for the time required to make the measurements and then analyze them, and that's fair, most studios do not need that rigorous an assessment.

Last thought for the night - real bass traps are tuned devices, usually a narrow bandwidth or high Q, and they need to be built for the space. The big foam things marketed as bass traps are really wide band absorbers that happen to be big enough to absorb lower frequencies. Which turns out to be good for most of us. I recommend always starting with wide band absorbers because they cause fewer problems. About the only thing you can do wrong with foam or rock wool is put up too much of it, and that is easily reversed (although sometimes it can hurt the wallet.)

Pay attention to symmetry, sufficient distance between the walls and the listening position (especially the rear wall), obvious "bad" reflections, and energy build-up at lower frequencies and you'll have the room tamed. Then focus on placement of loudspeakers, ears, and sometimes gear.


----------



## Tanuj Tiku (Jul 11, 2015)

Well, this has definitely become a thread with lots of great information!

Thanks Bill and Mike!


Tanuj.


----------



## JonFairhurst (Jul 11, 2015)

Speaking of rear wall reflections, the rear wall will have no fewer than eight different depths. The room length will vary from something like 20 to 26 feet. It's not going to be symmetrical, but it should happen to ensure that I don't have any strong modes in that dimension. That should result in a "low Q" response, so broadband absorption might be just what I need. It also sends me back into the measurement domain as this won't be a simple rectangular box.

Good news about the stairwell. I plan to add a couple of 'coffee bag' absorbers in strategic places to break up the parallel walls. I don't know if it will help the main room, but it should make entry into the room sound nicer.

Here's an odd thing. When I play music in the room as I work, it sounds relatively good. I think we get used to prerecorded music played in bad spaces, and we don't mind a bit of extra reverb. But when I'm in the room without music, voices and incidental noises sound horrid to me. I have a different expectation of what reality should sound like, and the room really colors it. So I've learned to keep iTunes running to cover the place up. It really helps with my experience.


----------



## JonFairhurst (Jul 16, 2015)

I've received twelve 703 panels, took six out of their boxes and simply placed them around the room. The characteristics are hugely different with hand claps. It's an interesting mix of live and dead. I've wiped out most of the side to side bounces but I won't do the ceiling structure until much later, so vertically, the room still rings. There's a bunch of junk in here right now to break things up, so it's not as live as when the room was empty, but the room is still more alive than I'd like.

And now I really hear the stairwell. When I clap, the sound bounces around in there from wall to wall and eventually returns. The clap in the room dies out with a pitched echo returning later from the stairwell. No problem. There are three locations where I will add some 703 which should tame all three sets of parallel surfaces. Two are 40 inches apart and the third is smaller and spaced at 8 feet, so I expect that 703 without bass traps should do it. Sound can go in as long as not much comes back out after a small delay.

Still lots to do. I ran out of paint on a Sunday, then had a road trip. (The good news is that the paint is 40% off tomorrow.) Then I'll do the hardwood stairs. 

Regarding the material, I ordered the full swatch set from ATS Acoustics. We've chosen the Ivory burlap, which matches the colors in the room perfectly and is a nice, clean weave. It's much more like 1960s speaker grill cloth than some old potato sack. When people see it, they'll think "textile", not "burlap". According to their site, they ship it in rolls, rather than folded, so it should look good. 

Anyway, with the panels in here, the room is a lot more pleasant to be in. I just did a nearfield listen to Pink Floyd's "On the Run" from "Dark Side of the Moon" on my little JBL LSR305s and the imaging was fantastic. If 703 leaning on a few walls makes this much improvement, I can't wait to hear the finished room with my Custom JBL 4430 mains.


----------



## Hannes_F (Jul 17, 2015)

I've generally stopped discussing acoustics in forums because for every insght you share there are three folks at last that will oppose it. Use measurements and don't fall for wishful hearing. Here is an orientation table that I've put up some years ago and that made it into the gearslutz FAQ at least:



> Originally Posted by *Hannes_F*
> It would be important that reading the mentioned stickies and following the most popular suggestions will get you most probably to level 1 or 2 of the following list. The higher levels need more information and - and this is very important - individual measurements and calculations. For most people hiring a consultant will be the only way to ever get there.
> 
> Level 1 or 2 can be sufficient for the given project or not depending on the conditions and purpose. However it should be important to realistically estimate the goals and to give at least a glimpse on advanced possibilities.
> ...


----------



## JonFairhurst (Jul 17, 2015)

Thanks, Hannes,

No doubt, my room will be far from perfect. It's non-symmetrical (small windows and sliding glass door on the left side and a stairwell on the right side near the front wall) and I will only sacrifice the visual aesthetics so far. With luck, I'll get to Level 2.5.  

I'll say this though, while Level 1 above seems really poor compared to the other levels, it sounds many times better than an untreated room. 

_*0th level:* Untreated, existing room with hard surfaces on walls, floor and ceiling
Result: FR is the least of your worries. The modes and decay time are so bad that it's a physically painful place to be._ 

Clearly, my initial plan was "1st level". I've got some ideas for adding true diffusion and for bass capture. I won't go with the "thick absorption" approach, so Level 4/5 aren't options.

BTW, the information at this site looks to be quite good for an online resource: http://arqen.com/


----------



## Mike Greene (Jul 18, 2015)

I love that feeling of "magic" after testing a few 703 panels. I still don't really know why it works, but it's great that it does. 8) 

As far as what level you're going for, I'm of the same mind as you, where I wouldn't sacrifice too much functionality or appearance just for the sake of "better" sound. The costs (financial plus aesthetics) to make incremental acoustic improvements gets to "diminishing returns" status really quickly.

A few more thoughts come to mind. First, along the lines of my personal philosophy of _"I wouldn't go too crazy trying to tweak the room," _it's helpful to know that drywall is a fairly decent low frequency absorber. So if your walls are drywall, as opposed to concrete, then you'll have fewer bass issues.

Speaking of drywall, make sure the walls are insulated, if possible. It helps with the acoustic damping of the wall (to absorb low frequencies.) Plus it also lessens sound transmission from room to room. You get something like an additional 10db drop, just by insulating a wall. (More fiberglass magic!) Don't want to hear Junior's stereo from his bedroom? Then insulate his walls.

It sounds like you might be buying your 703 panels from an audio company. (It's typically in plastic wrapped bundles of eight, and doesn't normally come in "boxes.") Nothing wrong with that, but if you need more and want to save a few bucks, you can get it from lumber yards. Also, there are competing/equivalent products to Owens Corning 703, including one by Johns Manville that I've used. (Some lumber yards have different distributors.)

If you want to save even more money, ordinary household insulation is also effective. You don't want to stick it on your walls, of course, but if you build resonators or bass traps, you can stuff them with regular wall insulation rather than buying 703.

Or depending on how your walls are constructed, you might even consider pulling off the interior drywall from one wall, leaving the wall open with insulation between the studs. Staple cloth to cover, then if you want to get extra fancy, put wood slats over the cloth for that pro studio look. This makes that wall completely dead and would be ideal for the front wall. This idea only works if you have concrete or cinder blocks behind the wall, of course. (I think you said it's a basement, so I'm not sure how the walls are constructed.) Just a thought.


----------



## JonFairhurst (Jul 20, 2015)

Great thoughts, Mike.

It's a daylight basement, where the room faces the downhill slope, with the height of the concrete decreasing from the top of the small hill. There are some utility walls where there is a gap between drywall and concrete. So the interior is all drywall, but the stuff and the gap behind the drywall varies. The one concrete surface is the floor, which is now hardwood. I can't wait to install the "cloud" above it.

The painting is completed (so I don't plan to rip out drywall) and I'm now starting on the hardwood stairs. The ivory-colored burlap arrives this week. I plan to buy some muslin to put between burlap and fiberglass. Not only will this ensure no pesky fibers in the air, it will keep the yellow fiberglass from tinting the off-white burlap. It should help ensure a smoother surface as well.

I'm really looking forward to treating the stairwell. It exits to the side at the right-front corner of the room. In essence, it's a giant bass trap in that there is no immediate corner pressure build-up there. The sound goes up the stairwell, bounces around to create mid-frequency resonances, and sends back a delayed, contoured signal. At 42-inches wide, the main mode is 161 Hz. There's another mode around 70 Hz. These are hard, drywall surfaces, so I get all the harmonics too. And sure enough, I hear serious smearing in the high-bass/low-mids. Three panels and some small bass traps should take it out of the equation. My opposite front corner could probably use some serious bass trapping to match the non-corner on the other side.

The nice thing about the room - even with my current, lazy placement of naked panels - is that the low bass already sounds quite good. The JBL 4430 clones use JBL 2235H woofers. These produce sound down to their resonance point of 20 Hz and are tuned to -3dB at 35 Hz. While the high-bass is currently smeared and sloppy due to the room, kick drums and other very deep sounds have an effortless feel to them. Since we're used to speakers with a big 80 Hz bump, sometimes these speakers sound like the bass is weak. Then you listen closely and hear low tones that we don't normally hear from typical sound systems.

http://www.jblpro.com/pages/components/2235h.htm
http://www.lansingheritage.org/images/jbl/specs/pro-speakers/1984-4430-35/page06.jpg

On to the hardwood stairs and then the stairwell treatment...


----------



## Tanuj Tiku (Jul 20, 2015)

Just too add to what Mike said...

If you are using plasterboard, I am assuming it is fixed on a pine frame. You can use cheaply available cotton waste felt to fill the cavities to avoid resonance. This is used as an alternative to rockwool which is difficult to work with.

A simple layering of plasterboard-deadsheet-plasterboard is good for basic insulation and it does take care of bass frequencies. 

But, you need to allow the sound to enter through the fabric and any final layer such as wood wool panels made with pine shavings and concrete (some use magnesite bonding and are more expensive but not required to be so). They absorb a wide range of frequencies but allow the low frequencies to pass through.

Also if you are applying any fabric it must let the sound pass through. 

In my limited opinion you are better off making a reflective front wall and an absorbent rear wall. 

Diffusion is another game altogether but once again I have no knowledge of this. 

Do share some pictures so we can understand better!

Good luck!


----------



## wst3 (Jul 21, 2015)

I fear that some reading this may confuse two very different issues - sound isolation and (for lack of a better term) room treatment.

Sound isolation is all about keeping noise in or out of a space. It is darned difficult to do effectively, especially at low frequencies. (ironically, a well isolated room is much more difficult to treat, since all the energy stays put<G>!)

Room treatment is all about making the audio in the room sound good - for whatever value of "good" you desire. Fundamentally simpler to understand, but there are so many good solutions it can still be somewhat confusing.



Tanuj Tiku said:


> If you are using plasterboard, I am assuming it is fixed on a pine frame. You can use cheaply available cotton waste felt to fill the cavities to avoid resonance. This is used as an alternative to rockwool which is difficult to work with.



Pretty sure you already have the walls in place, but if you do not, consider metal studs to frame the walls. They can take the place of resilient channel. Stuffing the cavities is a great practice.



Tanuj Tiku said:


> A simple layering of plasterboard-deadsheet-plasterboard is good for basic insulation and it does take care of bass frequencies.



Well, "it depends"... loaded vinyl (deadsheet) can decrease transmission through a wall, but even that only goes so far. Two layers of plasterboard are a must, and it it better to use dissimilar densities... except of course that the only way to really isolate is massive walls, in which case you'd want two layers of the densest sheetrock. What's a fellow to do?

The thing to avoid is multiple mass-spring (usually air space)-mass configurations. Mass-spring-mass is good, so you'd think mass-spring-mass-spring-mass would be better. You would be wrong. Don't do it!



Tanuj Tiku said:


> But, you need to allow the sound to enter through the fabric and any final layer such as wood wool panels made with pine shavings and concrete (some use magnesite bonding and are more expensive but not required to be so). They absorb a wide range of frequencies but allow the low frequencies to pass through.



Can you elaborate? I've no idea what you mean, but somehow think I should, or need to.



Tanuj Tiku said:


> In my limited opinion you are better off making a reflective front wall and an absorbent rear wall.



And here we go<G>... there are literally dozens of design concepts for a critical listening space. In my limited experience they all work, or at least they all can work, if implemented well.

This is where it gets really tricky (Nick B will disagree). The first thing you need to decide is exactly what you are trying to accomplish, and that covers a lot of turf. In no particular order - stereo or multi-channel placement, coverage, frequency response, support for desired listening levels, noise, isolation, and so on, and that is just the acoustics. You also need to factor in power, grounding, interconnections, ergonomics, lighting, HVAC, etc.

It is enough to make a grown man cry!

Oh, and did I mention limits imposed by silly little things like physical space, existing construction, and (dare I say it?) budget?



Tanuj Tiku said:


> Diffusion is another game altogether but once again I have no knowledge of this.



It really is not all that tricky. Specifically for the room treatment part of the puzzle you have three tools:

absorption - you want to convert some of the energy into heat - might be to balance out the frequency response, might be to battle specific low frequency modes, no matter, the goal is to convert that energy into some inaudible form. Note this has almost no effect on isolation.

reflection - sometimes you want to re-direct energy, usually away from your ears. You may be redirecting it to an absorber or diffuser. Sometimes you simply want it to arrive at your ears at some later time.

diffusion - sometimes you want the energy to stay in the room, but you don't want it be coherent. (Am I being coherent?) Mostly we use diffusers to create a more effective simulation of a reverberant field. The problem with small rooms is that they are not (usually) statistically reverberant. And we LIKE reverberation. Makes music sound better. If the space can not be truly reverberant then we up the ante with diffusion.



Tanuj Tiku said:


> Do share some pictures so we can understand better!


Agreed!


----------



## JonFairhurst (Jul 21, 2015)

Photos? Here they are!

http://fairhurst.com/photos/Remodel/During/

Regarding isolation, the only challenge I have is from the HVAC system in the utility room. As I note on the photo page, I'll add a Murphy Door and sound-proof it as best I can. Fortunately, the HVAC is mainly white noise from mid to high frequencies. There are no bass drums in there. I should be able to get adequate isolation for my needs.

As Bill wrote, I'll be dealing with reflection, absorption, and diffusion.


----------



## Mike Greene (Jul 21, 2015)

Great pictures! That's going to be a really cool room.

My first thought is that you're going to need a lot more 703.  

I see now what you mean about the stairwell, and why you've spent so much time thinking about it. I wonder if you might be better moving your mixing desk to one of the long walls. Don't get me wrong, I think it will be cool where you have it now. I'm just throwing the idea out there, and Bill would know better than I about whether a shorter distance behind you is a problem.

Those are cool looking speakers, by the way.


----------



## JonFairhurst (Jul 21, 2015)

Yeah, I previously had the desk on the long wall next to the stairwell.

Keep in mind that this will be more of a shared space than a mixing room. I'll add some surround speakers, TV and seating to make it a home theater. And my wife wants to see the screen while on the treadmill.

Rather than a desk, I plan to use a wireless keyboard and lap tray from the sweet spot for general use. I would also like to make a small cart with a MIDI keyboard that I can use in the room. As we've moved from desktops to laptops to tablets with ChromeCasts on a big screen, I'd like to take editing and composing in a similar direction. Leave the screen on the wall and the workhorse PC(s) nearby and move the controls to a comfortable place in the room. Unfortunately, wireless USB didn't happen. Bluetooth is weak. I expect to use a small laptop or micro computer to connect my input devices, headphones, and whatever. I'd then use various remote client and MIDI over LAN technologies to get to the big PC & screen. It's my vision for a ditch-the-desk computing lifestyle change - without giving up rich control surfaces. But this could take a while. For now, the desk lives...

FWIW, here is more info on the speakers... http://www.fairhurst.com/jon/speakers/


----------



## Tanuj Tiku (Jul 21, 2015)

Jon,


Well, you have one thing going already and that is a fantastic vibe! The room looks great already! Obviously, you are not in a position to build more walls and isolate further and perhaps you do not need it as much as you need acoustic control.

Bill could really help you out here. Even though I am in the middle of building my own studio, I have a very superficial knowledge about this stuff. My designer is the one telling us what to do at every stage. 

@Bill, when I was speaking of the fabric, I simply meant choosing something transparent that actually allows the sound to pass through to the layers in the walls. Far too often in DIY projects I have seen people use thick sofa fabric and that does not help so much! The wood wool panels are something Philip has asked me to fix in my studio. They are made of pine shavings with concrete mix. It will be fixed as the final layer on the floated walls and the ceilings. 

You can go through my build here: http://vi-control.net/community/index.php?threads/my-studio-diary.44864/

Anyway, back to you Jon - great going! 

A solid door for the HVAC room could be just the thing you need. You could also use a heavy laminated glass door made very easily. But, again Bill can you help you here. Also Nick B!


----------



## JonFairhurst (Jul 21, 2015)

Thanks Tanuj,

Yes, for the cloth, I will use muslin to ensure that the fibers don't migrate or show-through and a high-quality burlap for the visible, outside layer. The burlap just arrived today. 

Interesting stuff, muslin: https://en.wikipedia.org/wiki/Muslin 

* It gets its name from the Indian port town Masulipatnam, known as _Maisolos_ and _Masalia_ in ancient times and the name 'Muslin' originated from the name _Maisolos_. 
* Used in theater, photos and film for backdrops, including green screens.
* Used as a sunlight diffuser in the silent films before they had bright enough lights and fast enough film stock.

And, yes, I've been following your project. Your results should be stunning!


----------



## JonFairhurst (Jul 31, 2015)

Here's a quick update:

I continue to work on the stairwell. I've wired the stairs for motion sensors and LED lighting, have done some structural work on them, and have started mounting the hardwood steps and risers. I'll send photos once complete.

As a quick aside, I first purchased a reel of Warm White HitLights from Amazon, which cost about $10 for 5 meters. Unfortunately, the color quality was very poor. It clearly had a large green spike. I have since purchased a high CRI (90+) reel from Super Bright LEDs for about $100. The color is beautiful. It's especially important to have good color lighting for showing the complex color of wood. It went from a sickly look to a rich look. As I'm only using 10-inches of light per step, one reel does it for me. It was $100 well spent.

Continuing with the stairs, rather than focus on treating the overall space, I'll focus on reducing the final reflections that return back into the room. In other words, I don't care what sound goes in and I don't care what sound bounces around. So my new goal is to limit the sounds that come back out. This means heavily treating the wall that extends from the main room's front wall as well as another wall in the stairwell that faces into the main room.

That leaves the stair risers that directly face the speakers. I believe that they cause delay and smear of the high bass and low mids on the right channel. I'm not willing to sacrifice the hardwood look, but I have the opportunity to make micro-bass traps. Each riser will have a small box behind it, which is about 7 inches tall, 40 inches wide, and 1.5 inches deep. I will minimize the thickness of each riser and mount them in a way that isn't overly rigid, so there they can flex a bit with bass waves. I will add some absorptive material in each cavity behind but not touching each riser.

Will my micro bass traps make any difference? Probably not. But the cavities are already there. Using a thin backing board is cheaper than thick wood. Throwing a bit of insulation in each cavity is simple. So overall, it won't really cost any time or money. Yeah, it might not help but it certainly won't hurt. I'll test the concept by giving it a thump and turning up some loud bass content while feeling for vibrations. My guess is that I won't be able to confirm anything, but what the heck.

The main improvement will come from treating the walls that would radiate sound back into the room. That _will_ make a difference.


----------



## wst3 (Jul 31, 2015)

you have a unique opportunity here! The spaces between and behind the steps could be turned into a very cool absorber, but it would have to be active. Read up on Hemholtz resonators and similar devices. It will take a little math, but the results could be quite good! If you take this approach try to lean towards broadband overall, narrow band resonators can cause as many problems as they solve!

On the lights - new technologies do seem to skip the whole color temperature thing don't they?


----------



## JonFairhurst (Aug 7, 2015)

Well, the stairs won't really work as bass traps. I mounted the hardwood on thin material for the risers, but they are too solid. The resonance frequency is much, much too high to be of use. 

In theory, I could have used the larger space under the stairs for a Helmholtz resonator, but this would have required ripping out a fair amount of the existing structure and would have required holes in the risers. My wife was already worried about some small holes letting critters into the house. An array of holes would have been a poor relationship decision. 

The project continues...


----------



## wst3 (Aug 8, 2015)

I was assuming you'd use the space under the stairs as part of each trap. Making the traps the height and width of the spaces between the steps, and then varying the depth could be a very effective broadband trap. However, never good to create doubt on the part of the spouse - save that for new sample libraries!


----------

