Rob,
Square rooms are a drag for audio. Also you say you want a room that is "optimal" for mastering. There is a term for a room that is of the correct dimensions in audio. This term is "legal" as in a "legal room". To meet the criteria for a "legal room' you need to have a minimum dimension of 14 feet. Ceilings and walls. An example of a legal room would be 25' X 18' X 14'. You can make the room useable with treatments but it is never going to be "optimal". The main thing you’re going to need to do is reduce one of the dimensions of the room so that it isn't square. After you decide how you want to achieve that you should think about 4" foam and as you mentioned diffusion. There is a guy here that is building diffusers for home studios for a very good price. PM me and I will hook you up with him. Forum rules prevent me from posting a blatant Spam regarding this. You’re going to need some serious bass trapping in a room that small although the 4" foam will help. Place foam on the walls in front of the mix position and along the side walls to the point where you sit to mix. If possible, foam on the ceiling to the sitting position would be desirable. Diffuse the rear wall and add some corner traps in the front and rear corners. This will get the room to a useable point. This is a standard studio design termed as an LEDE (live end, dead end) room. I recommend that you select you monitors to limit the extreme lows. Pick a pair that roll off around 50 or 60 Hz. This will help minimize bass loading and modes in the room. Sorry, this is never going to be a space suitable for mastering, however you will be able to track and mix in there. Fats
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Tannoy, Dynaudio, Blue Sky, JBL, Earthworks, Westlake, NS 10's :D ,
Genelec, Hafler, KRK, and PMC
Those are good. …………………….. Pick one.
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Got to agree with Fats.

Re the parallel walls........you need to have these at least 12 degrees out of parallel to minimise standing waves. This can be done with one wall per parallel pair or approx., 6 degrees on each wall. This should also be applied to the parallelism (I like that word :D ) of the floor/ceiling if at all possible.

A suggestion for monitors that are fairly good bang for buck are Tannoy Reveals, either passive or active as these go down to the sugested 60Hz.

:cool:

I'll be using Dynaudio BM6a's. Thanks for the comments.

Rob,

> I have a 12 X 12 mixing room that I want to treat for optimal mixing/mastering. <

As CFF suggested, you're going to need real bass traps for a room that size and with those dimensions. Forget foam and get real bass traps. Owens-Corning 705 fiberglass is four times more absorbent at low frequencies than any foam. But even four inches of 705 is not adequate for the bass range.

> I don't want an acoustically dead room, and hope there is a formula for this. <

Diffusion will definitely help given your parallel walls. But understand that diffusers do nothing to solve bass problems unless they're at least 4-8 feet deep.

The best "formula" is to alternate hard and soft surfaces, either in vertical strips maybe two feet wide, or with a checkerboard pattern using two foot squares. I suggest installing membrane bass traps in all four corners, plus a few more on the rear wall, and then apply 1-inch 703 fiberglass in strips or a checkerboard pattern on the remaining wall surfaces. You can cover the fiberglass with fabric to make it more attractive.

You probably want the ceiling mostly absorbent, and the floor mostly reflective. Again, you can alternate the floor and ceiling treatment so as not to have a single large area of soft or hard surfaces anywhere.

--Ethan

Ethan posted

Owens-Corning 705 fiberglass is four times more absorbent at low frequencies than any foam.

I was researchig this same subject just a little while ago and I learned that the 4" foam is actually as absorbant as the 705. That's why I suggested it. 705 is hard to find and can be a danger to your health when cutting it if your not careful. I don't see any way to splay the walls in a space that small. Your just going to need to bring one of those dimensions down to 10' or so. Fats

Fats,

> I learned that the 4" foam is actually as absorbant as the 705. <

I'd be curious where those specs came from. I have a chart compiled by John Storyk's firm that shows 4-inch thick 705 having an absorption coefficient of 0.75 at 125 Hz. Compare that to 4-inch Auralex Studiofoam which is 0.31, or 4-inch Sonex which is only 0.20.

These specs are all when the material is mounted flat against the wall. The low frequency performance of all these materials increases as it is spaced away from the wall. But even with an air gap of one foot, none of these products are nearly as effective as wood membrane panel traps at the lowest frequencies.

> I don't see any way to splay the walls in a space that small. <

Yes, I agree. That's why diffusion makes sense for Rob's room.

--Ethan

Ethan,
I read that in the December 2002 issue of EQ magazine in an article by Mitch Gallagher about turning an attic space into a studio. These guys had had John Storik design a plan for them but due to cost considerations ($10,000!) they changed some of the specifications. They did however as you mentioned mount the foam on a plastic lattice and install it with an 4" air gap between the wall and the foam. This could be a good way to splay the walls. Fats

Fats,

> I read that in the December 2002 issue of EQ magazine in an article by Mitch Gallagher about turning an attic space into a studio. <

Ah, now I see where the confusion comes from! I contributed to that article, so I can clear this up.

The panels Storyk originally specified were 2-inch thick 703 fiberglass, not 4-inch. Further, 705 is twice as dense as 703, which makes it much more effective at the lower frequencies. So overall, 705 is about three times more absorptive at low frequencies than foam.

Also, since you have that article, you'll note that John Storyk recommended membrane absorbers for trapping the lowest frequencies, which is what Mitch bought.

--Ethan

Ethan,
Cool to have you contributing here at RO! Please continue. I stand corrected regarding the 703 / 705/ The article didn't specify which was used. I saw the bass traps thing also but later in the article it was stated that a savings could have been made using foam traps instead of the membrane type. From this I extrapolated that they would be comparable in performance. I myself don't see much to be gained by investing a large chunk of dough in the space that is described here. As I stated at best the room will be useable but never optimal.
---------------------------------------------------------------------------------
Tannoy, Dynaudio, Blue Sky, JBL, Earthworks, Westlake, NS 10's :D ,
Genelec, Hafler, KRK, and PMC
Those are good. …………………….. Pick one.
---------------------------------------------------------------------------------

Fats,

> Cool to have you contributing here at RO! <

Glad to. This is a great place.

> it was stated that a savings could have been made using foam traps instead of the membrane type. From this I extrapolated that they would be comparable in performance. <

Yes, that generated a lot of confusion! No, foam rubber and fiberglass are nowhere near as effective as real membrane panel traps. Especially at the lowest frequencies.

> I myself don't see much to be gained by investing a large chunk of dough in the space that is described here. As I stated at best the room will be useable but never optimal. <

True, but when that's the room you have, you do what you have to to make it work. And even though real bass traps may seem expensive, a room full of traps costs about the same as one Massive Passive EQ. :)

--Ethan

Hey guys,
Thanks for the great suggestions. The framers came today and I'm actually dealing with 11 x 11 now (damnit). I can knock about 6 inches off of one wall if that would help at all. I am interested in the fiberglass Ethan. Where could I find that? Also, where would I find the best prices on treatments in your opinions? Thanks for the suggestions.

Rob

Rob,

> I'm actually dealing with 11 x 11 now (damnit). <

I feel your pain! :)

> I can knock about 6 inches off of one wall if that would help at all. <

Don't do it. The insignificant change in modal response is not worth losing six inches of your already tight working space.

> I am interested in the fiberglass Ethan. Where could I find that? <

You won't find 703 or 705 rigid fiberglass at Home Depot, but you can get it from places that specialize in insulation. I get mine from Kamco, a chain in the New York / Connecticut area. Look in the yellow pages under Insulation or go to the Owens-Corning web site where you can look up distributors in your area:

http://www.owenscorning.com

Or call them at 800-GET-PINK.

> Also, where would I find the best prices on treatments in your opinions? <

Here's a link to the bass traps Mitch Gallagher bought for his studio, which he wrote about in EQ magazine:

http://www.realtraps.com

(Bias alert: this is my company)

--Ethan

The 705 Owens glass board may or may not be hard to find .. memory serves me right it was 9lb density. I went to a local supply house (not Home Depot!), talked with the guy, and ended up with a product made by Manley. 2' x 4'x 2" panels .. I bought a few "bundles" of this .. remember to ask for unfaced both sides, as it is offered with and without facing. I believe it was like $5-$7 per panel..

I think diffusion is the term to look at, rather than absorbtion. If you can stop the walls/cieling/floor from any resonant problems, then simple diffusion in a good sized room may do the trick. My control room is 10' high x 29' x 15', and I used the ceiling as a trap. Since the roof had a gentle slope, I placed solid panels in front of either soffitt monitor, and then the manley glass panels, and some lightly packed unfaced glass above that.. got some guilford cloth, installed that and then wood trim. Take a look at my site, you'll see the trap, and you can also view a page labeled "Construction" that shows the actual steps during that construction. If I can help in any manner, I'd be glad to.

Also, if you do the simple math f=1130/d (frequency = speed of sound / distance) you can plot the three initial room modes (front to back, side to side, and top to bottom ... these would be the "d"). So .. f= 1130/29 feet (f = 39hz), 2nd harmonic would be 39x2=78hz, 3rd =78x2=156hz

If you carry this math out to 10 or 12 harmonics for all three dims, this will show what areas of frequency might and/or will present problems, since you would like to see all those modes be different numbers at each harmonic to prevent standing waves.... you'll also can see why a square room is a problem for that. This is a starting point to consider in construction, and reforming a room as well.

KS,

> I think diffusion is the term to look at, rather than absorbtion. <

Yes, diffusion is often useful at the mid and high frequencies, but it won't prevent the standing waves that cause severe peaks and dips throughout the low frequency range. If you want to see how flat a room really is, play various low frequency sine waves - say, 40 Hz. to 250 Hz. - and walk around. Most room analysis is done with pink noise or swept sine waves, but those ignore the reality of sustained bass notes!

> If you carry this math out to 10 or 12 harmonics for all three dims, this will show what areas of frequency might and/or will present problems <

That is certainly valid, but still ignores the effects of standing waves which are the real problem in most rooms. While knowing the room modes can reveal where the resonances will be worst, an untreated room will still have peaks and dips at all frequencies due to acoustic interference. It's easy to test this yourself, again using continuous sine waves. Pick a frequency - any frequency - play it, then walk around and you'll see what I mean.

By the way, I went to your studio site. That's a gorgeous control room!

--Ethan

Rob, what is behind the Panelling? If it is framing, it will act like a panel absorber if you seal the airspace behind it. You could vary the thickness of the paneling over each 2 ft section to change the frequencies that it will absorb. The thicker the panel (until you get to the point that it doesn't resonate) the lower the bass it will absorb. There are formulas that will predict the frequencies absorbed. Each of these sections must be air tight!!!!!! Put some insulation inside (not touching the panel), this will give a little more broadband response.

Be creative. Hope this can help.

Eric

The 705/mineral wool/rockwool is the way to go. For a room this small, i would get the 4" stuff check comercial building supply places.. (this stuff is required as firecode insulation in most comerial applications) just call up and act as if you are a contractor on a job, and u just "ran out" and need a few more pieces.

I built pine framed boxes 2'x4' x8" pieces and stained them. put the mineral wool to the front, leaving an air gap between the insulation and the wall. then i covered them in speaker grill cloth (you can email me for mailorder co.'s) and top it off with half-round trim. dont make the mistake i made, mounting them with brackets on the inside, because you will eventually want to move them. This stuff absorbes sound like nothing else.. i made a "dead room" for guitar cabs and whatnot.. its just erie in there.

with a room that small i think u need a dead ceiling. consider accoustic tile. (but u cant afford to give up height, so it would have to be bare minimum distance from the existing cieling) I would also consider some serious thick carpet/padding. maybe you dont want it "dead" , but a room that small u dont have too many options.

these are just a few of my options ( and i have many more...) on diy , bootstrap studios..

I had the same type of issues with my control room. It's only 10x11 8 ft ceiling. I used mostly 703 fiberglass(front corners and 2" on side walls). I couldn't get a hold of 4", so I glued 2" panels together. I also made some of the plywood faced diaphragmatic bass traps on the rear ceiling. I still have a couple peaks in the 140Hz range, but I'll kill those off with some Helmholtz slat absorbers. Yes, an RTA and sound meter can be your best friend.

themidiroom

Thanks guys,
I am trying to get some sheets of 705 board from a friend of mine who's a contractor. I called Owens Corning myself, but they won't deal with anyone without a contractor number. I am thinking of using a 4 X 4 sheet of latice to trace and cut out a pattern in the 705 to get a checkerboard pattern. I have been reading a few web sites that provide instructions for buiding bass traps, but I am having trouble understanding it completely without seeing step by step photos. Anyway, I am going with 705 board if I can get my hands on some. Thanks again. If anyone has a source for reasonably priced acoustic foam or dispersion boards, I would appreciate the info.

Rob

Rob,

> I am thinking of using a 4 X 4 sheet of latice to trace and cut out a pattern in the 705 to get a checkerboard pattern. <

A checkboard pattern is useful to get an even distribution of reflective and absorbent surfaces, but don't make each square less than 2x2 feet. If you cut very small openings in the 705 you'll reduce its effectiveness at low frequencies.

> I have been reading a few web sites that provide instructions for buiding bass traps, but I am having trouble understanding it completely without seeing step by step photos. <

Have you seen the plans at my web site? They're pretty clear, and if you have questions I'm right here ready to help. :) My "Build a better bass trap article" is listed on my Articles page:

http://www.ethanwiner.com/articles.html

> If anyone has a source for reasonably priced acoustic foam or dispersion boards, I would appreciate the info. <

Forget foam, as it's less effective - and much more expensive - than 703 or 705 fiberglass. For diffusion, any reflective panel will work fine. It doesn't have to be fancy, just large and mounted at an angle.

--Ethan

We appologize for the inconvenience, but this member's posts have been deleted.

SonOfSmawg
Administrator

[ January 29, 2003, 12:44 AM: Message edited by: SonOfSmawg ]

Ethan .. thanks for the kind words on the control room .. it was a year in thinking, and a ball to build.

The point on standing waves IS one of the largest and least delt with issues, agreed. I thought I mentioned in this post that the 1st issue is to decouple the walls etc before treatment .. if possible .. since this will begin to deal with the standing wave problems (and a good bass trap also be required). I have read, absorbed, and spoken with people who know far more than I'll ever understand on all this.. but one thing really rings true, and, IMO, should be the starting point:
"Build as good a room and as well thought out a room as possible, using proven ideas, keeping your own desire in sight. When done, do what everyone else does.... adjust it. This will be the best you can do, and it may be beter or worse than what you or anyone imagined. There is no right or single best design or way."
That was from a guy who was in on 4 renovations at a major label who had multiple rooms. I bounced my ideas off him, he approved and/or suggested .. in the end he flew in to tune it, and was amazed at how well it ended up... so was I. Endless hours of sealing, checking, and rechecking paid off.
My control room ended up with @$30,000 invested during construction .. concrete, elec, air cond, to diffusion panels on the wall, and 5 months of my own work. I think that this is dirt cheap for what I ended up with.

Thanks for the ideas guys. I still haven't found the 705. I did think of a question though. Does the volume at which I mix offer any possibilities as far as limiting some of the problems associated with a small room? I will treat it as best I can, but if mixing at a lower volume would be advised, I will to that. I wish I had tons of cash to build a better space, but what do you do? It is just a project studio, and I'm not looking to produce grammy winning results, just the best I can do. I guess if I get clean tracking, I can always send my projects to one of you pros for real mixing in a real room. I think that serious home studio users should probably do that anyway. Spending 10 hours of less per week average in the studio doesn't really give me the experience need to do the job right. Thanks again.

Rob

Hey rob,
you have a PM from me with the delatils of this supply house wher I got my insulation .. ask for Charlie, use my name ...
Jim

Keener Insulating & Supply Inc 77 Pitney Rd Lancaster PA 17602-2661 tel;717-299-1341 - Lancaster County

Rob,

> Does the volume at which I mix offer any possibilities as far as limiting some of the problems associated with a small room? <

No, it's a myth that using nearfields at low volumes avoids the affects of the room. If standing waves and acoustic interference cause a 15 dB. hole at 80 Hz. where you sit right in front of your loudspeakers, that hole is still present and still 15 dB. whether the music is playing loudly or softly.

--Ethan

Except for extreme levels, which would probably change the characteristics of your monitoring system, the only change caused by monitoring at different levels would be your PERCEPTION of frequency response, due to Fletcher-Munson effect. That would cause you to make different decisions, and should be avoided.

As Ethan pointed out, other than that you would have the same room response only quieter. The recorded result would be the same at any reasonable mixing level (other than bad decisions bassed on PERCEPTION), assuming the level "to tape" was the same.

One other possible band-aid for your square room would be to set up your mix position "catty-corner, then make sure the two walls behind you are quite dead - this should cut down on early reflections at the mix position and help minimise flutter echo. I'd make sure the corner behind the mix desk (in front of you) was bass trapped with a corner trap; I don't think there's any practical way to eliminate the modes at 50, 100, 150, etc, caused by your two 11 foot dimensions, since you'd need to take care of these every 50 hZ up to around 400. That would mean traps tuned to 6 or 7 different frequencies, plus extra bass trapping for the bottom.

You didn't mention, and nobody has asked yet, what your ceiling height is - if it's 8 feet, the third harmonic of ceiling height and the 4th harmonic of your wall dim's are within about 5 hZ of each other and will most likely make the 200 hZ range even MORE problematic.

If you build a slat resonator, you might want to tune it to around 205 hZ just for that reason.

If you use a spreadsheet to calculate values, be aware that the slat-eng-met.xls one found at Studiotips.com (haven't finished confirming this yet, only know it gives different results from Everest's formula) seems to be set up for PERFORATED Helmholz traps, NOT slat absorbers. (If you intend to do this, let us know - I'll post the link to the one I use)

Oh, BTW, welcome to the impossible-to-win battle of Ergonomics vs. Acoustics - for a control room, there will ALWAYS be compromises - at least that's the conclusion I've come to while studying acoustics these past 15 years or so... Steve