My home studio is 11x11 with 8 ft ceilings.
The floor is carpet but I've put a piece of oak plywood about 4x6 on the floor.
I have lenards style bass traps in the verticle corners and corner fill in the lateral corners.
I've made a bunch of diffusors out of pvc pipe and stuffed them with polyester filling. The pipes are 2.5, 3 and 4 inches thick and 3 to 4 ft long. I've just hung them on the parallel walls in no certain order just to try and diffuse the sound.
I have about 21 of these diffusors hanging on the walls and also a couple wooden diffusors that are basically just two oak boards glued together and attached to the wall with the joining end facing out to diffuse sound.
I am wondering if it is possible to have too much diffusion. Could I actually get to a point that I am killing my natural reflections by having too much diffusion??
If so, about how many of these diffusors should I have hanging on my walls?
Also, should I have end caps on the pvc pipes so sound can get inside the pipes and be absorbed by the polyester filling?
I am mainly using this room to record vocals and acoustic guitar. I will be mixing in another room.
Right now I am still not happy with my acoustic guitar sound. It almost seems like I'm not getting enough reflection.
I GREATLY APPRECIATE ANY ADVICE!!

Well, I applaud the DIY effort. The diffusors you've described can be somewhat helpful if they were larger (the pipes) and maybe not quite so many of them.

You say you have Lenrd 'style' traps - what are they specifically? You still need some absorbtion in the space. What is the 'corner fill' in the lateral corners?

The bass traps are the typical corner bass traps thatare thick foam that fits into the corners. These are exactly like the LENARDS bass traps by AURALEX.
The corner fill is 4 inch thick long cubes. THen on one wall I have one row of the 4 inch corner fill in the corner where the wall and ceiling meet and then one row of 3 inch thick wedge foam up against the corner fill.
On the opposite wall I have the 3 inch wedge foam the entire length of the lateral corner where the wall and ceiling meet.
I actually treated this room with lots of foam a couple of years ago and probably had about 60-65% of the walls treated with acoustic foam. My guitar tracks sounded terrible because I was absorbing all my high end and I was left with a bass heavy track. Therefor I took down a bunch of the foam and basically left the corners treated to deal with the bass buildup in a small room.
THen I made these diffusors in an attempt to diffuse the sound and hopefully make the room sound good and balanced for recording.

How many of these diffusors would you recommend I use and where would you recommend I place them?
On the middle areas of the parallel walls? Near the bass trap treated corners??

I appreciate any help!! Thanks!

Unfortunately, in 11x11x8 there isn't much option for effective diffusion - you're just not far enough away. The best you can hope for IMO is getting rid of the slap without killing the ambience too much for a live room.

That's why I recommended the panels I did. Think of something like a Chinese dressing screen that will stand up in a 'W' shape. Also, you can play with making smaller polycylindrical diffusors either on wall or on stands. They're basically just a bent pc of plywood (damped with insulation fill) that do more dispersing than diffusing but they will help.

I'd also recommend looking into some better bass control. The Auralex LENRDs are kind of special in terms of foam. (That's a nice way of saying they're about the ONLY ones that really do anything). If they're not Auralex per se, investigate some 6-8 lb mineral wool straddling the corners, 4" of 705, or 6" of 703 as a MUCH more effective bass absorber. For the corner fills, 3" of 'unknown' foam really isn't doing much - sorry.

The foam is exactly like auralex as far as I can tell. It was rated the same as far as absorption. I got it at http://www.foambymail.com
What would you say is the difference? They look exactly the same and supposedly absorb sound the same.
If there is a big difference Maybe I will look at better bass absorption.

Why will the pvc diffusors not work in a room this size?
Won't they provide a round surface to reflect the sound back into the room at different angles?? They are sticking out from the wall about 3-4 inches. I thought this would diffuse the sound enough.
Actually it did seem to be helping but I put up more and now it doesn't seem to sound as good. Can I possibly have too much diffusion?

Sorry to be the bearer of bad news but FBM is, well, crap. They have been caught lying about the specs. That foam is basically worthless for bass control.

The PVC will be OK but it's just not big enough radius wise to be effective down low enough. MAYBE it would do down to 2kHz - maybe.

Not too much diffusion as much as the small PVC causing cancellation and focusing issues due to the small radius.

I'm talking about something with a 10-20 FOOT radius.

Bryan

What is the main difference between the FBM and Auralex foam?? What makes the Auralex that much better?

Would it make any difference if I put 1 inch thick styrofoam behind the bass traps I have now??
Why are Auralex diffusors any good being the size that they are?? The minifusors are deeper than just about any other Auralex diffusor and they are only about 5 inches deep and a foot across. The other Auralex diffusors are even smaller.

Is there any kind of report showing that FBM lied about their specs??

Is is possible to get a good recording sound in a room the size of mine or is it impossible?

OK, I found an article explaining about the FBM and Auralex.
Ok, I must rethink my room. SHould I just make DIY bass absorbers and get rid of all my FBM foam??
SHould I just forget diffusion in this room and concentrate of bass absorption??

Can this room be made good enough for acoustic guitar recording?

Please tell me exactly what I should do and I'll give it a shot.
My room is again, 11x11 with 8 ft. ceilings.
Please tell me how to make the bass traps as cheaply as possible. Please tell me what to make them out of, how thick, what size,etc.
And also tell me where to put them in my room.

I know this is asking a ot but I really appreciate all of your help.

Putting styrofoam behind them won't help. If anything it would hurt. Styrofoam has almost no absorbtive properties.

If it were me, I'd start with some real bass absorbers across the vertical corners of the room - floor to ceiling if you can. Use something like 6" of 703 or 4" of 705. The cheapest way to go is 4" of 8lb mineral wool and it will do a good job for you.

Since this is a 'live' room, I'd face at least 2 of them with an FSK facing.

Initially, take down the diffusion and get the bottom end under control first. Then maybe start adding it back a little at a time to see if you like what it's doing and when is too much.

You can also just build some of the movable hard/soft gobos to help minimize the parallel surfaces - but again - wait till you get the bottom end under control first.

Sorry to be so blunt about the FBM.

Bryan

Don't know if this helps, but here is a little How-To I put together on building cheap traps for a small room much like yours. Ethan looked at it and didn't tear my plans apart, so I assume they are within the realm of reason.

Link to the How-To


Unfortunately as was mentioned above, diffusion doesn't do much in a small room. The analogy I use is a fire hose. In a gigantic warehouse hanging from the rafters, a diffused fire hose creates a gentle mist that covers a large area.... In your home office/studio, everything still gets soaked.

Thanks for the plans. Unfortunetly the last few pictures of the absorbers in the studio didn't show up in the article. Can you possibly post the pics so I can see exactly how you hung them?
I really appreciate your help.
Any idea where to get the mineral wool?
Lowes? Home Depot??

Also, one of my corners has a doorway in it. I could treat above the door and the wall beside the door but not the actual corner because of the door. Is that OK??

Try viewing that page again. The pics load fine for me. As for where to get material, check the top of this forum. There is a thread on suppliers. Worst case, hit the yellow pages and start calling insulation supply places around your area. Someone is bound to have mineral wool or semi-rigid fiberglass available. Home Depot and Lowes are dead ends.

Do you have to remove the foil from one side of the panel? Will the bass not absorb as well with the foil left on?
Could the trap be wrapped on some type of plastic before applying the fabric to insure the fibers don't get in the room or will the fabric definetly hold the fibers in?
Is DOW brand TUFF-R a type of insulation that will work??

Would it work if I just took the mineral wool panels and wrapped them in fabric and stood them in my verticle corners?? That way they wouldn't have to be attached to the wall and I could stand one in the corner where the door is when the door was shut.
Also, in a room as small as mine should I maybe consider using mineral wool panels without FRK since the drywall parallel walls already reflect the mid and high frequencies??

You can certainly start with just 4 panels straddling the corners free-standing. Eventually, you'll want more corner coverage though.

I'd start with 2 of them faced and 2 unfaced and see how it sounds to you. You have to be the final judge of how live or dead you want it. The foil will not stop bass absorbtion at all. In fact, with a denser material as the base, it can actually act somewhat like a membrane - enhancing low frequency absorbtion - just a matter of where which depends on the core material. What the foil will do is to reflect some of the upper mids and highs (will still absorb a bit) to keep it from being too dead and allowing you to use that HF absorbtion on wall panels to assist with reducing slap.

When you say more coverage are you talking about the wall/ceiling corners?
I am having a hard time finding anyone who sells the mineral wool panels or fiberglass.

Initially, since you said you were just going to lean them, I assumed you were only doing 4 2'x4' panels. If you're going to build them full height, that may be sufficient for your needs. I'm sure it could use more - just a matter of balance.

Bryan

Do we know for a fact that Foam By Mail really is not as Auralex?? I looked into it and I'm pretty sure that the fire proof rating is not as high as FBM claims and that they basically copied the NCR ratings from Auralex but I'm not sure there is a real big difference. FBM claims to have a 2 lb per cubic foot density rating. Auralex won't state what theirs is.
Is there a independant study showing FBM is substantially inferior? I think FBM basically copied Auralex products and then claimed the same specs but is it a proven fact that the specs are not similar?

Also, the only place I can find that sells the Mineral wool is in Virginia and they have a good price but UPS charges an as much or more to ship the panels than what they cost. That makes them not a very good economical choice.

To make bass traps for my studio I could get the mineral wool for about $160.00 which is good but the ripoff artists known as UPS will charge me almost that same amount to ship them. Because of the size of the panels UPS will charge for 90 lbs. packages even though they are only 50 lbs. each. THis kind of puts a damper on building my own traps. By the time I pay for the wool and shipping and additional supplies I could probably just buy enough Auralex acoustic foam to effectively treat the room.

Does anyone know of a mineral wool dealer in Ohio??

I believe Ethan did an unofficial study with measurements in one of his rooms and the FBM performed horribly.

Bryan

Why not try a few Quadratic residue diffusors?

http://www.mhsoft.nl/Diffusor.asp

They aren't expensive to make, if you have access to wood working tools (+ someone who knows how to use them), $40-50 of MDF, and wood glue.

They're quite attractive as well, but I don't know what you'd need for a room that size.

Thanks for the link Mike.
I looked at the quadratic diffusor and I can't see why that would perform much better than the diffusors I made from pvc. The pvc is sticking out from the wall at different heights from 2.5 inches to 4 inches and the pvc pipes are round so they should scatter/diffuse the sound into the room.
Maybe I'm missing something but I can't see why the Quadratic diffusors would diffuse the sound better than my pvc.
Can anyone explain this??

Well I have my mineral wool on order. The kind I'm getting does not have the foil face.
Is this bad?
My room is only approximately 11x11 with 8 ft. ceilings. In a room this size should I not be worried about not getting the reflection of mids and highs? Could I get a really good sound just putting these bass traps in the corners? Keep in mind that I'll also put one 4 ft bass trap in each lateral corner where the ceiling and wall meet.
If I do need some reflection what would you recommend I do to the rock wool panels? Wrap them in plastic? Thanks for any input.
I really appreciate everyone's help.

Also, Can I definetly get a good recording environment in a room that is 11x11 if I treat it effectively??
My biggest concern is recording great acoustic guitar sounds in this room. Most everything else, bass electric guitar, synth & keys will be recorded direct.

Just make sure you face some of it. For a RECORDING room - especially acoustic guitar - you want it a bit more live but still need the bass control.

Bryan

Thanks for the input. If I can't get the facing do you have any other options for getting some reflection?

You can try heavy Kraft Paper but the real thing works better and will give you a better membrane effect.

What about the foil tape used to seal duct work? Not duct tape. I'm talking about the actual foil tape used on air conditioners, furnaces and sometimes where ducts come together. It is foil and almost mirror like or chrome looking. Would that work?
If so I'm thinking of putting in in strips on the front of the traps under the fabric, of course. It is about 3 inches wide and I could put it on the front with about 3 inches between each strip. Would that give a good balance of absorption and reflection??

Might work but you wouldn't gain any of the membrane benefits. Not sure how thick that tape is either.

Bryan

Bryan,

> I believe Ethan did an unofficial study with measurements in one of his rooms and the FBM performed horribly. <

Just to be perfectly clear, I paid IBM to measure both Foam By Mail corners and Auralex LENRDs in their acoustics lab. This was not a home made test!

You can see the results at the RealTraps site on the Product Data page, linked in the Acoustics Info section. It's in the second graph down on the page.

--Ethan

I checked with my supplier of mineral wool and ask him about the foil facing. I could order some from them for about an extra $60 and then glue it on myself. I ask him about the foil tape and he said it is the same thing as the foil facing. except that it is already sticky on one side so I wouldn't need any glue.
The tape is available at just about any hardware store for about $7.00 per roll. If anyone has a chance to check out the tape let me know if it really is the same as the foil facing.
With all the parallel walls in this small room I'm wondering if I could get away without using and foil because I get a lot of reflection of the drywall. What do you guys think??

The foil tape is about .03mm thick. What exactly is the membrane going to do that won't be done with just foil tape??

Why would it not work to just treat the corners with the bass traps without any foil for reflection but then not use any mid/high absorbers on the parallel walls.
Would this be that much different than using foil on the bass traps to reflect the highs and some mids but then having to put mid/high absorbers on the parallel walls.
It almost seems to me that what I'd be reflecting from the the foil on the bass traps I'd then have to absorb with the mid/high absorbers on the parallel walls.
Am I over simplifying things? Is it because the 4" bass traps would absorb way to much mids and highs??
Also I'd appreciate if someone could explain why a quadratic diffusor would work any better than my pvs diffusors which actually provide a bigger area of diffusion and it is actually curved to spread the sound into a broader area.

Ethan, that was very cool of you to have made such an FBM review. I just had a friend buy a bunch of that stuff. I am making some simple 4" bass traps for her cheap to compensate a bit.

Again, to the original poster, another diffusion option is the wood slat diffusor. I'm making two 3'x4' units this week using 1"x4" pine and expect they should be pretty nice.

From Steven Klein's site:

"We consider these to be perhaps the best sounding and most versatile acoustic treatment available. Though we have classified them as a diffusion product, they also have an absorption quality due to their spacing and well depth."

http://www.soundcontrolroom.com/products/diffusion/woodSlat.htm

edit: It appears I will not be making these any more. Change of plans ...

I am having trouble finding FSK without spending a lot of money. If I put a sheet of plastic (about he thickness of a trash bag) on the front of each bass trap & then put the foil tape strips on that would that be enough to reflect the mids & highs?
Would the plastic by itself be enough?

Adding plastic yourself will help to reflect mids and highs but it may not give the same improvement at low frequencies you get from FRK fiberglass where the facing is bonded firmly. A thick coating of spray adhesive might work better than tape for that.

--Ethan

Well, I went ahead and bought the FSK from sensiblesoundsolutions.com. I figured I may as well not cut any corners and then regret it later. I can't wait to get these bass traps built and see how my studio sounds. I greatly appreciate all of your help! This site is awesome.