Diffusion / absorption in small room - ratio?

[666666]

I know there are acoustic forums, but just wanted some opinions from this forum here.

Generally speaking... take a small room, about 10'X15' with an 8' ceiling... used for recording instruments such as drums, etc... rug on floor and foam in ceiling (to kill early reflections from cymbals)

For the walls: What would you say is a good ratio / percentage in terms of diffusion verses absorption for a good all-purpose character, meaning not too live and not too dead? 50/50 perhaps?

I realize this is a VERY general question, but just wondering if there is a general rule of thumb, or if you guys have arrived at a general ratio that seems to work in most cases.

I plan on building custom 1 foot square absorption panels (thick foam or similar) and also 1 foot square diffusion panels (complex patterns made of hard wood, something like a "skyline"), for the walls. I plan to arrange things in such a way that I can move the panels around easily, changing the pattern and ratio of diffusion to absortion at will, etc. I think it's a neat idea.

BUT, before I build such panels (which will take time and money), I am trying to get a feel for what ratio will probably work best. Maybe I should go 75% diffusion and 25% absorption???? I hope to not wind up making too many of either type of panel.

Any thoughts appreciated. Thanks.

[Kiwiburger]

Small rooms are always a problem. In many ways, it can be best to simply kill all reflections to try to avoid problems. If this was a vocal booth, I would tend to go for 50:50, with complementary opposing surfaces.

In other words, if your foam is arranged in a checkerboard pattern, when you consider the opposite wall, don't have foam point back at foam - stagger them so the opposite wall has the opposite surface directly opposed. (Not sure how well I explained that ).

Since this is a drum room, you might want it as live as you can get without problems. The drums themselves are diffusers and break up a lot of the parallel surfaces, so you could perhaps put all your foam into the corners, to help kill the room nodes. Proper bass traps would be better.

[Tone Obsessed]

Go here: http://www.auralex.com/pcf/

You can download a.pdf file, fill it out and they'll come back to you with solutions at no charge ( suggestions for their products). Also, check with Ethan here:http://www.realtraps.com/

There's a good start.

TJ

[ricfoxx]

It wont be long before the acoustic experts chime in with the "fill your room with bass traps" line. Be careful putting too much acoustic abortion in your room if it will be a tracking space, it will be unnatural and musically uninspiring. We have a small space with 3 different rooms ( 2 10X10 rooms and a 20X20) and we spent time acoustically treating each room for our needs. The 20X20 room has DIY diffusers and a couple of bass traps. Its lively with smooth and rich ambience. We have a booth that has 100% absortion and is completely dead and unnatural but works in different applications. We spent the most time on our mixing room. We put a laminate floor in with an acoustical tiled ceiling. We put "Superchunks" in all 4 corners and in between at the ceiling and walls. We also put 2'X4' DIY 2" broadband panels at all first reflection points with 2 clouds above the mix position. This room is Sooooo tight and accurate and sounds great for mixing and is acceptable to track in.

Hope this helps,

[thebearingedge]

No Diffusion.

Your diffusers would have to be at least a foot deep and be of the RPG skyline type with VERY small pieces. Just treat it with rigid insulation and/or acoustical cotton. The trouble with trying to use foam in that small of a room is that the foam absorbs little to no bass and the truth is, the bass will be as bad as the reflections. A respectable eq and reverb will take care of the ULTRA dry sources you capture. Even drums if you've got a good enough signal chain and convolution.

Best of luck!

[Kiwiburger]

I constantly hear this myth about foam vs fiberglass. There isn't a lot of difference pound for pound - except foam won't rip yer lungs out.

All absorbant material has the basic problem that it is more effective on highs than on lows. Bad room acoustics tend to have a preponderance of bass node problems, so absorbancy is sort of exactly what you don't need.

If you want to use foam, buy high density, flameproof, bacteria proof - and go as thick as you can. You don't have to worry about breathing in glass fibres. You can even paint the stuff! This makes it more effective on bass - extreme highs will bounce off, lows go right through. The membrane effect absorbs more bass too, so paint actually assists to address the weakness of foam.

I believe diffusion is especially recommended for small rooms. A cheap way is to use thin convex panels. They act as membrane bass traps to. Just rubber mounts some thin panels into aluminum channel - with some foam behind them.

Or just buy a bunch of commercial bass traps - there is a lot to be said for that.

[thebearingedge]

Originally Posted by Kiwiburger

I constantly hear this myth about foam vs fiberglass. There isn't a lot of difference pound for pound - except foam won't rip yer lungs out.

All absorbant material has the basic problem that it is more effective on highs than on lows. Bad room acoustics tend to have a preponderance of bass node problems, so absorbancy is sort of exactly what you don't need.

If you want to use foam, buy high density, flameproof, bacteria proof - and go as thick as you can. You don't have to worry about breathing in glass fibres. You can even paint the stuff! This makes it more effective on bass - extreme highs will bounce off, lows go right through. The membrane effect absorbs more bass too, so paint actually assists to address the weakness of foam.

I believe diffusion is especially recommended for small rooms. A cheap way is to use thin convex panels. They act as membrane bass traps to. Just rubber mounts some thin panels into aluminum channel - with some foam behind them.

Or just buy a bunch of commercial bass traps - there is a lot to be said for that.

Are you saying that 8lb rock wool absorbs the same amount of lows as foam? I think you might mean "square foot for square foot." Also, I haven't heard anybody at the acoustics forums mention paint membrane absorbstion, might be a good once to bounce off of them.

Sure free fibers my be an irritation but you cover it so that's that.

I'm not an expert but after looking at many solutions for long time, I feel that dismissing the superiority of rigid/commercial insulation as a myth is simply unreasonable.

Also I'm pretty dumbstruck by your claim that absorption will not help with nodes. You mean absorbing all highs and not enough lows right? You mean absorbing as much lows as possible while avoiding absorbing too many highs, right?

Convex panels ("Polys") are what I've heard recommended by those more experienced than myself, but they've also recommended a VERY aggressive (large and/or deep) design in order to really have any use in a small room. Look, diffusion means that the sound reflects in a dispersed manner, right? How dispersed will the sound be before hitting the mic/ears if it has only traveled like 10ft since reflection?

I must say, I'd like to know what you've used and your room's dimensions and the styles you work on. You seem very certain of your strategy. I'm pretty new to this recording mess and it would be a shame to squander precious time on useless acoustics treatments.

Though my tone may not suggest it, I will readily admit that there is a real possibility I am wrong... always. Also, not trying to call anybody out on anything but your post seemed kind of vague.

For any who care about acoustics in their spaces, please look at the Acoustics forum at Music Player.

[Glenn Kuras]

> You mean absorbing as much lows as possible while avoiding absorbing too many highs, right?<

Thats what you should be doing.

>Convex panels ("Polys") are what I've heard recommended by those more experienced than myself, but they've also recommended a VERY aggressive (large and/or deep) design in order to really have any use in a small room. Look, diffusion means that the sound reflects in a dispersed manner, right? How dispersed will the sound be before hitting the mic/ears if it has only traveled like 10ft since reflection?<

Yep!!!!!!!! Polys are super cool, but they really should be used in bigger rooms, for the reason you have given above.thumbsup
For the recorded I have nothing against diffusion, but should only be used in a bigger room (for the reasons you just listed above).

[Glenn Kuras]

Originally Posted by Kiwiburger

v

If you want to use foam, buy high density, flameproof, bacteria proof - and go as thick as you can. You don't have to worry about breathing in glass fibres. You can even paint the stuff! This makes it more effective on bass - extreme highs will bounce off, lows go right through. The membrane effect absorbs more bass too, so paint actually assists to address the weakness of foam.
.

I would not recommend painting foam. One thing about foam is it absorbs much more high end then low end (the reason why mineral wool or rigid fiberglass is better). Paint is going to reflect the high end and make the foam useless at that point.

Also you made a point about fibers in the air. I agree and you should cover the panels to make sure this does not happen. thumbsup

Glenn

[Kiwiburger]

Fair enough - don't believe me. For the sake of anyone else who might be wondering:

I see so many internet "experts" who dismiss foam, and then recommend fibreglass which does effectively the same thing (but with health hazards if not covered up).

When looking at absorbants, obviously square area is a factor - but that's not what I meant. I would expect you to compare the same surface area in any fair comparison between foam and fibreglass.

With any absorbant, depth is a major factor. Comparing 2" foam with 6" fibreglass is not fair, and I also would expect you to compare the same depth.

But foam comes in different densities. The lightweight stuff is fairly useless. That's what I mean about comparing "pound for pound" - the heavy stuff is good.

There are companies selling "acoustic" foam products, and all they do is carve a pretty pattern into it, and paint or otherwise cover it up. They charge far too much for it, but it does look nice. The pattern doesn nothing except look nice, and in fact the absorbtion would be greater if they had not carved it away.

Room nodes in a small room create a bass problem. If there is any room sound you want to salvage, it will be the high frequencies. What I am saying about absorbants such as fibreglass or foam is that they do exactly the opposite of what you want. They kill any desirable highs, and leave the problem lows to muddy up the room.

What you want is bass trapping - and absorbants can be used with skillfull design to make bass trapping, but they are not naturally good at killing bass.

Diffusion is certainly about re-directing sound waves. That's exactly how convex panels work. To do that, your diffusers need large dimensions, relative to the wavelengths of the frequencies you want to diffuse. Large panels, bent into a reasonable radius can achieve more than small ornamental diffusers that really only affect the highs.

I built bass traps from thin panels mounted into the corners to form convex shapes with a radius of around 2 - 3 feet (I varied them on purpose). My concrete rooms had an enormous, cavernous bass problem - they fixed it (along with a lot of 4" foam on the walls for mids and highs).

Acoustic control is usually a compromise between budget and cosmetics and sound. There are many ways to achieve similar things.

I was as surprised as you about the painting foam thing. I saw this done in a studio, and thought they had gone crazy. It's a useful thing to know.

[Glenn Kuras]

Originally Posted by 666666

I know there are acoustic forums, but just wanted some opinions from this forum here.

Generally speaking... take a small room, about 10'X15' with an 8' ceiling... used for recording instruments such as drums, etc... rug on floor and foam in ceiling (to kill early reflections from cymbals)

For the walls: What would you say is a good ratio / percentage in terms of diffusion verses absorption for a good all-purpose character, meaning not too live and not too dead? 50/50 perhaps?

I realize this is a VERY general question, but just wondering if there is a general rule of thumb, or if you guys have arrived at a general ratio that seems to work in most cases.

I plan on building custom 1 foot square absorption panels (thick foam or similar) and also 1 foot square diffusion panels (complex patterns made of hard wood, something like a "skyline"), for the walls. I plan to arrange things in such a way that I can move the panels around easily, changing the pattern and ratio of diffusion to absortion at will, etc. I think it's a neat idea.

BUT, before I build such panels (which will take time and money), I am trying to get a feel for what ratio will probably work best. Maybe I should go 75% diffusion and 25% absorption???? I hope to not wind up making too many of either type of panel.

Any thoughts appreciated. Thanks.

There is a fine balance between absorption and diffusion. Problem with diffusers is you really need to be far from them or you can still get comb filtering coming off of them. If you don't want to make your room "dead", which I am with you on that one, then for the bass trapping cover the fronts with FRK to keep some of the highs in the room. Also one trick we have done is some drum rooms is build panels that are 6"x 4' and space them out on a wall every 4". This will give kind of a diffusion and absorption effect. All and all you will want to kill most of the room sound, but the trick is to not only absorb the high end but also the low end.

Glenn

[Kiwiburger]

I would not recommend painting foam. One thing about foam is it absorbs mush more high end then low end (the reason why mineral wool or rigid fiberglass is better). Paint is going to reflect the high end and make the foam useless at that point.

You seem to be contradictiong yourself.

Yes - foam has a problem because it absorbs the highs more than the lows.

Painting it makes it more reflective to high, which helps to compensate for that problem. Also, the paint forms a membrane - like a kick drum - which vibrates with bass notes and the foam dampens it.

Any way you look at it - painting foam (which seems wrong) makes the foam absorb more bass and less highs - making it more desirable.

Contraversial I know - but this wasn't my idea.

[Glenn Kuras]

Originally Posted by Kiwiburger

Fair enough - don't believe me. For the sake of anyone else who might be wondering:

I see so many internet "experts" who dismiss foam, and then recommend fibreglass which does effectively the same thing (but with health hazards if not covered up).

When looking at absorbants, obviously square area is a factor - but that's not what I meant. I would expect you to compare the same surface area in any fair comparison between foam and fibreglass.

With any absorbant, depth is a major factor. Comparing 2" foam with 6" fibreglass is not fair, and I also would expect you to compare the same depth.

But foam comes in different densities. The lightweight stuff is fairly useless. That's what I mean about comparing "pound for pound" - the heavy stuff is good.

There are companies selling "acoustic" foam products, and all they do is carve a pretty pattern into it, and paint or otherwise cover it up. They charge far too much for it, but it does look nice. The pattern doesn nothing except look nice, and in fact the absorbtion would be greater if they had not carved it away.

Room nodes in a small room create a bass problem. If there is any room sound you want to salvage, it will be the high frequencies. What I am saying about absorbants such as fibreglass or foam is that they do exactly the opposite of what you want. They kill any desirable highs, and leave the problem lows to muddy up the room.

What you want is bass trapping - and absorbants can be used with skillfull design to make bass trapping, but they are not naturally good at killing bass.

Diffusion is certainly about re-directing sound waves. That's exactly how convex panels work. To do that, your diffusers need large dimensions, relative to the wavelengths of the frequencies you want to diffuse. Large panels, bent into a reasonable radius can achieve more than small ornamental diffusers that really only affect the highs.

I built bass traps from thin panels mounted into the corners to form convex shapes with a radius of around 2 - 3 feet (I varied them on purpose). My concrete rooms had an enormous, cavernous bass problem - they fixed it (along with a lot of 4" foam on the walls for mids and highs).

Acoustic control is usually a compromise between budget and cosmetics and sound. There are many ways to achieve similar things.

I was as surprised as you about the painting foam thing. I saw this done in a studio, and thought they had gone crazy. It's a useful thing to know.

As I don't agree with all of your methods of treatment (the corner bass traps you made. ). I do respect anyone that has taken the time to understand that the room sound is pretty damn important. Hat off sir.
I have nothing against foam, besides trying to use it for the low/mid bass. I have clients all the time that already have foam in there room. I don't tell them to "rip it down", but try to then go in and balance out the room. Like I have said before it is all about balance.

Glenn

[Glenn Kuras]

Originally Posted by Kiwiburger

You seem to be contradictiong yourself.

Yes - foam has a problem because it absorbs the highs more than the lows.

Painting it makes it more reflective to high, which helps to compensate for that problem. Also, the paint forms a membrane - like a kick drum - which vibrates with bass notes and the foam dampens it.

Any way you look at it - painting foam (which seems wrong) makes the foam absorb more bass and less highs - making it more desirable.

Contraversial I know - but this wasn't my idea.

no I am saying that it would then be usless.

Do you have any lab data on painting foam? Not being a smartass, but only asking. Your right it is contraversial, BIG TIME!!

Glenn

[ricfoxx]

Originally Posted by myfipie

no I am saying that it would then be usless.

Do you have any lab data on painting foam? Not being a smartass, but only asking. Your right it is contraversial, BIG TIME!!

Glenn

These are the type of comments that get me going! Tell me what a Great Lab result looks like...A flat line across the spectrum...Hummmmm (in a mixing room maybe)...Maybe you have tested great sounding rooms (determined by EARS, not by numbers) and then published some type of paper regarding Scientific Properties that Create a Great Sounding Room.

See the thing is, all of our favorite gear usually has "Mojo" bumps in certain frequencies or 2nd and 3rd order distortion which creates a pleasing sound to our ears. Same for a Great Room, usually harmonic overtones and a larger than life sound from good sound reflections. Now there are alot of variables that effect the sound of a room, not just what absorbs sound on the walls. What is above the ceiling (free space or insulation), what is behind the walls or what is in the room. Hell, even the air pressure effects how we hear, that is why Im against the "broadband absorption is the answer for all acoustical problems" comments. Diffusion is importantant, more important to me in a 10'X15' room than throwing up panels or foam on the wall. Believe me, we tried alot of things in our rooms; foam, broadband panels, poly's and superchunks and it took a variety of those solutions to get our room sounding good.

Now, your room and my suggestions...

On the parallel 15' walls...build (2) 8' Poly's (simple to build, just do a search) and put them on those walls making sure they are directly across from each other.

On the 10' walls...build or buy (4) Broadband panels (they all work about the same, I prefer ones with 8lb Mineral Wool) and place 2 on each walls but not right across from each other (stagger them.)

For the Corners...buy 4 bundles of 8lb mineral wool (PM me, I know where to get a good deal on it) and cut 8 perfect triangles out of each Mineral wool panel. This will give you 48 perfect triangles and will fill up a corner up to 8'. Go to your Walmart and in the fabric dept you can usaully find fabric for $1/yard (make sure you can blow through it.) Get enough for you 4 corners and if you are making your own panels. Buy 8 1X2's at your local Home Depot or Lowes. Now attach 1X2's (screws, nails or glue) in the corners so that they are slightly smaller than the front of your wool triangles. Now stuff the corner with the wool triangles. I would suggest putting something like cardboard in front of the wool. Now Cut your fabric for your corners and staple it so that the fabric goes around the edge of the 1X2. All you have to do is trim out the 1X2 with shoe molding.

You will have to work a little bit building this stuff but it really works as a solution.

As I stated early, there are too many variables, so when you are treating your room, make sure you use you ears. People are musically inspired by what we did in our rooms using all of the solutions above. PM me if you need further explanations.

Good luck,

[Kiwiburger]

I agree that it's all about balancing the room to your taste. This is a tracking room, right? Not a mixing room? I believe that was established right at the start.

Room acoustics for tracking are always a compromise - there is no such thing as the perfect room; just that some rooms are much better for certain instruments.

Acoustic technicians tend to rely on published specifications and calculations - which is a good starting point. But you simply can't get published specs on every possible material. The foam makers aren't going to publish specs for painted foam, because there are too many variables. At best they might suggest using a light coat of non-bridging paint - but that's because they are assuming that you want similar performance to their published specs.

Suggesting cardboard in front of wool is just as valid as suggesting a coat of paint over foam. It does not make it "useless". What it does is address the imbalance that any absorbant has: foam, fibreglass, wool - they are all more effective on the highs than the lows.

My ears like to hear a tight low end and some ambiance in the high end. So foam, fibreglass, wool - left uncovered will do exactly the opposite of what I want to hear.

As far as i'm concered, I don't care about calculations. I know what I want to hear (or don't want to hear), and I know a bunch of basic principles.

There are many ways to achieve what you want - with many compromises. I think it's worth knowing about the painted foam trick. An advantage is that foam gets a bit faded with age - painting can make them look better.

[thebearingedge]

Originally Posted by myfipie

As I don't agree with all of your methods of treatment (the corner bass traps you made. ). I do respect anyone that has taken the time to understand that the room sound is pretty damn important. Hat off sir.

+1 thumbsup

[Glenn Kuras]

Ricfoxx and kiwiburger,

Ok guys before you guys start my head let me explain about painting the foam. For the most part foam is going to absorb mostly high end and if you paint it you could end up just killing the high end so you end up with nothing left. Kind of a strong statement, I know, because there would be something left, but maybe not enough to really do much. Hey that might be what you want.

Now the statement about lab numbers and things. The reason for lab numbers is so you know how the product performs. Think of it as audition tape of a player. It is not an absolute by any means and I am not saying there should be guys in white lab coats telling you this or that about your room sound. There are many different ways to treat a room and some work better then others, but there are certain things that are used in some rooms that will not give the intended effect. A good example of this is using polys in a small room. Will it help? yes. Can you make it work. yes but you have to understand that you will get comb filtering off of them if you are close to them. If you do want to use diffusion, for a smaller room you might get better diffusion effects with something like a QRD. If there was a thread about what kick drum mic to use and some guy chimed in and said “your all crazy all you need is a sm57”. I am sure you would chime in on why that might not be the best choice. Well that is all I am saying in the above.

I am with you guys room sound is a personal touch.

Glenn

[666666]

Thanks so much for all the replies.... all very interesting.

Let me elaborate a bit on the specific purpose of this room.

It will be mainly a drum tracking room.... for tracking standard drum kit... big kit, loud "high energy" music most often.

The room is in the basement of a building. The room will be constructed of dual decoupled stud walls with two layers of sheetrock on each, spaced about 2 feet away from the outer basement concrete walls. This may be a good thing (?) as some bass frequencies will be able to travel out through the sheetrock and into the 2 foot gap before they hit the solid concrete walls.... I'd think this would allow some low frequencies to "escape" the room itself, would be better than if the concrete walls were the actual walls of the tracking room itself. I need to build a dual decoupled wall system within the basement regardless in order to reduce sound leakage into the surrounding and building... yes, the ceiling of the room will sit on top of the new stud walls and none of this will touch the surrounding building at all except for sitting on the concrete floor. I'm basically building a self standing room, about the size of a small one car garage (but lower), inside the basement.

Yes, I could cover the entire inside of the room with foam to kill ALL room sound (since the room will be small), but I've been in 100% foamed rooms, and they are just terrible... totally unnatural sound, I don;t think it's "healthy" to record in such an odd sounding space. I'd really like to have SOME ambience if at all possible.

Bass frequencies... well, with drum kit, I'd think that low frequencies would not be as much of a problem than if this was a bass amp tracking room or a mixing room (where you'd have constant blasting low frequencies). Yes, the kick drum will dish out some powerful low end waves, but bass drum low end output is intermitant, not constant (like a bass guitar). A few bass traps perhaps right behind the kit (on the floor) and maybe even a few feet in front of the bass drum might help without having to go too nuts treating the entire room itself with 50 bass traps.

Cymbals need to be tamed. Close reflections of cymbals turn cymbal content into a big sheering blurry mess, plus adds lots of hi-end bleed into the tom mics, etc... so... I was already planning on completely foaming the entire ceiling (being a pretty low ceiling)... but I hope to be able to achieve some type of favorable balance between absorption and diffusion on the surrounding walls to help add SOME life and ambience without allowing close reflections etc to cause trouble.

I do not expect to achieve wonderful room reverb, however I just don't want to have a room that has either a SUPER dead sound with all the life sucked out of it (100% absorption), but also cannot tolerate a room with serious problems such as nasty close reflections, standing waves, whatever.

I realize the solution is to get a BIGGER room, but unfortunately, after trying to indeed get a bigger room, it has proven to be totally impossible for many reasons... I am stuck with the space I have, for a long time... so I must make the best of it.

On the bright side, the last drum recording I did was done in an even SMALLER room with a lower ceiling (if you can believe that)... foam on the entire ceiling and maybe 60% or 70% foam on the sheetrock walls... and nothing else. I recorded close mics and OHs only, no room mics. The tracks came out very well considering... needed a little eq-ing, added some nice room reverb with some good effects units, it all worked out. However, I would like to take things up a notch (or several notches) next time, hopefully, plus I'd like to use "distant" mics this time as well, which means some of the room will be picked up too... so the room cannot be horrible... needs to be somewhere in a zone of acceptibility one way or another.

Keep the ideas coming. I'd totally agree with the concept of trying to trap the low end and diffuse some upper end (of which foam does the opposite). I also realize and agree that you can do all the calculations in the world, but the bottom line is how does it sound... and I think there probably ARE many different ways to make things work, the trick though is to find a way that is not too expensive and time consuming to make happen. Plus, though it will always be an experimental process, I'd like to aim as closely at the target as possible from the get go so I need not spend TOO much time experimenting... because then I'll wind up spending more time playing with room acoustics than actually recording, and that's no good.

So now, given that this will be a drum kit tracking room ONLY, what do you think?

[Glenn Kuras]

Originally Posted by Kiwiburger

I
Suggesting cardboard in front of wool is just as valid as suggesting a coat of paint over foam. It does not make it "useless". What it does is address the imbalance that any absorbant has: foam, fibreglass, wool - they are all more effective on the highs than the lows.

.

To be clear I was talking about using FRK on the fronts of bass traps that would be in the corners. That would absorb more low end at that point to keep more of the air in the room.

Glenn

[thebearingedge]

Originally Posted by 666666

So now, given that this will be a drum kit tracking room ONLY, what do you think?

Use the MAXIMUM number of bass traps that you can, foil-faced. Then, try getting the sound you want using absorption like Kiwiburger's statement about making sure to do the reverse of your patterns on opposing walls (hope that's clear what I mean).

BEFORE you start treating for reflections - SET UP A KIT and have a friend present to play it.

Then, treat bit by bit until you find a point where you like the kit and do not feel the need for more. Any diffusers you use will need to be EXTREMELY efficient to be of any benefit. I've always wanted to build some deep, miniature skyline PRD's!

Although bass notes are supposed to be brief on a drum kit, ringing will occur at some frequencies in a rectangular room. I just came off of a project where the guy had a NASTY resonance at a very high bass/low mid cycle. And he has a bigger room than you. You can NEVER overtreat for bass. This is why I suggest using dense rigid insulation for your treatment. Not only will it help with your reflected highs you are taming, but will absorb lower frequencies than your typical foam treatment which, as I said, is GEWD.

The fact that you are even this concerned about the room before talking about the kit type, mic choice (or even placement) or any of that crap puts you way ahead of the game. You get a thumbs up thumbsup

[Kiwiburger]

While you are at it - build a solid drum riser to get your kit off the floor, and reduce conductance into the floor. Rubber and/or air mounting. (A piece of plywood on some tyres at the minimum).

If purpose building for a drumkit, you might consider a permanent tunnel for the kick. Remember that the kit will be a major part of the room, and the convex surfaces are all good. No matter how you treat your room, there will be nodes and standing waves, and your kick and toms will sound vastly different at different parts of the room. A good trick is to set the floor tom where it sounds best, and then build the kit around that location.

I think toms work best on a rack, angled so the heads aren't parallel to the floor.

Just more factors that could affect your design. You could build a lot of bass trapping into a drum riser or kick tunnel or gobos ...

IMO you need to think bass trapping at every opportunity - not just purchasing some commercial units, but thinking in terms of everything in the room. I have two identical sofas that are part of my bass trapping strategy in my mix room. Everything affects everything else.

[Ethan Winer]

Originally Posted by ricfoxx

all of our favorite gear usually has "Mojo" bumps in certain frequencies

I know what you're getting at, but I can't see how any peak or null is beneficial whether it happens to fall on "pleasing" frequencies or not. In a tracking room a resonant peak adds that quality to every single thing recorded. In a mix room it influences every single thing you tweak - regardless of the key of the music. I am all for mojo - I really am! - but I'd rather add it via EQ so it can custom suited for each tune.

--Ethan

[Ethan Winer]

Originally Posted by Kiwiburger

Comparing 2" foam with 6" fibreglass is not fair, and I also would expect you to compare the same depth.

Agreed. One of the problems with foam is that it's usually sculpted. So foam that's sold as two inches thick is not really that thick because half of it was scooped out to create the surface pattern. I'm not convinced that 2-inch thick non-sculpted foam is as good as 2-inch thick 705 rigid fiberglass though. And for bass trapping, which is the most difficult part of acoustic treatment, 705 FRK beats any foam of the same thickness hands down.

Large panels, bent into a reasonable radius can achieve more than small ornamental diffusers that really only affect the highs.

Yes, in a large room curved wood can reduce flutter echo, but it doesn't reduce comb filtering as well as a real QRD diffusor. For anyone recording or mixing in a typical size home studio, a QRD well or skyline diffusor is a much better choice.

--Ethan

[Ethan Winer]

Glenn,

Originally Posted by myfipie

I have clients all the time that already have foam in there room. I don't tell them to "rip it down", but try to then go in and balance out the room.

Exactly, and this is what I do too. If someone has decent foam there's no reason it can't be used at reflection points for example. I'd rather see someone do that and put the cash they save into getting more bass traps. Now, when someone has Foam By Mail I do indeed suggest they throw it out. I also ask if they bought it recently, and if so I instead tell them to return it and demand a refund. But that's another story.

Likewise, when someone already has LENRDs I suggest moving them to ceiling corners or somewhere else useful.

Do you have any lab data on painting foam? Not being a smartass

Hey Glenn, you're my favorite smartass!

Seriously, this can be settled with lab data, or even a home made test using the ETF software or equivalent. The ETF Help file describes a ghetto method you can use to measure absorption without needing a lab. The idea is to point a loudspeaker at a wall, put the measuring microphone between the speaker and wall, then measure the comb filtered response with and without the absorption in place.

By seeing how much the peaks and nulls are reduced with and without the absorption, you can calculate how much of the sound is absorbed versus how much hits the wall and comes back. For this test to work you need a wall thick/massive enough to reflect back to the lowest frequency of interest.

--Ethan

[soupking]

I'm no expert, but I'm soundproofing and diffusing sound in a pretty small room like 14x18 with 1/3 made into a control room (though only half the height of the room).

I will have to add that big thick theatre curtains are a great for absorbtion (sp?). But I only use them in the corners with bass traps because I don't want my room to sound completely dead. Maybe hang some canvased paintings on the walls for some reflection and inspiration/vibe.

Just because the room is smaller doesn't mean it's crippled, it's just smaller sounding. There are other ways to maximize what you have. Maybe get a pink noise EQ, but there's no sense in going crazy about a room unless you can afford to I figure. And if you can afford to, why not get another room?

Peace,
-soupking

[NLP]

Is 8lb mineral wool ok (?!) or such dense material reflect higher frequencies (above 4-5kHz)?

[Ethan Winer]

Originally Posted by NLP

Is 8lb mineral wool ok (?!) or such dense material reflect higher frequencies (above 4-5kHz)?

Yes, 8 pound is fine.

--Ethan

[Glenn Kuras]

Originally Posted by NLP

Is 8lb mineral wool ok (?!) or such dense material reflect higher frequencies (above 4-5kHz)?

8 pound will work fine up to about a 6" panel. At that point (something like filling a full corner with wool) working with 4 pound will work just fine.

Glenn

[NLP]

So this threads "means nothing":

http://209.85.135.104/search?q=cache...lnk&cd=1&gl=si

http://209.85.135.104/search?q=cache...lnk&cd=4&gl=si

http://209.85.135.104/search?q=cache...t=clnk&cd=2&gl

...and interesting points from lovecow...:

http://www.recording.org/modules.php...20947&start=30

just curious