John Sayers' Recording Studio Design Forum Archive

Hey everyone,

This is just my second post, but I think I've got most everything ready for the first rough draft of my new stuido build. I don't have any questions in particular right now, just would love any input you guys might have.

Purpose: mainly for a drum practice and recording space. Will also function as a practice space for my band (8 people: drums, electric x 2, bass, keys, vocalists x 3) and as a place for live recordings for my band.

This is a new build in on my property with the closest neighbor being 200 feet away, so I don't need pristine sound isolation, but sufficient. Max SPL would be around 115 db at most, more often 110 db. If we could get that down to 65 db, that would be fantastic, but 70 would be ok. So aiming for 45 db reduction.

Current plan is for a rectangular room 23 feet x 17 feet x 11 feet. This will function as both a control room and live room. Construction will be room within a room. Outside will be 2x4 studs 16" oc with regular sheathing and acoustic caluk with r38 insulation. I might include an extra layer of dry wall in between studs, but I'm thinking I might could get away with not having this. Inside room will be 2x4 16" oc with two layers of 5/8" drywall and green glue and acoustic caulk. Here's a very rough sketch of the lay out:
There's a closet included for amps during live recordings as well as storage.

My main area that I would like some feedback would be for the acoustics of the space. I chose a combo live and control room because the majority of the time it will be just me practicing and recording. Although I will have many times of recording other instruments as well where I will play the role of engineer instead of musician. Won't be as conveinent as having two separated spaces, but one big space is a better "bang for your buck" in my mind. So in order to try and get the best of both world, I will plan on having adjustable panels made of 4" 703 that I can use to adjust absorption and RT60 (yes I know, to some purists, this room might not be big enough for RT60 to come into play, but after reading the Master Handbook of Acoustics, I still think it's an important goal to shoot for.) Live room RT60 will be around 0.6 seconds (roughly calculating 320 sabins for this - in between Eyring and Sabine equations). Control room with absorption will be RT60 of 0.3 seconds (roughly 640 sabins - closer to Eyring result - I might increase this to be closer to 660).

Ceiling design: 2" 703 with a 4 inch gap between panel and ceiling. Will take up the whole ceiling space except for an 18" perimeter. Skyline diffusors (1.5" well, 4.5" max column length with diffusion of 1k to 4.5k) - 41 panels will be interspersed on ceiling. Canned lights will be mounted between these.

All 4 corners will have panel absorption traps from floor to ceiling based Ethan Winer's design - can adjust front panel from 1/4" to 3/8" based on results of REQW, but I'm thinking the 3/8" might cover the trouble frequencies better. 1" 703 per Ethan Winer's design. These should be cheaper to make than superchunk bass traps.

Walls will have tons of diffusion. The leanfractal design by Tim Ferry. The two 23' side walls will have a 15 modulation design on each wall. These should diffuse from 300Hz to pretty high given the fractal design. According to Perry the critical distance from these should be about 5 feet (less than others recommend, but I think the room will be big enough that I'm not freaking out about it). The back wall will have 9 diffusor modulation with 1 lone diffusor on each end. The front wall will have 5 modulation design flanked by two on each end (the right one will cover the door).

To adjust the acoustics - 10, 4'x8' panels made of 4" 703 will be placed in the room (these will also double as gobos for isolation and in amp closet during full band live recordings and rehersal - will monitor with IEMs). These will hang on top of the leanfractal panels (max depth is 7.5" with modulation). They will be mounted behind the monitors on the front wall, at the first reflection points on the side wall, and then 3 other places on the side walls, none on the back wall. This is shown via the blue rectangles in the picture.

Monitors will be Yamaha HS8s, but will hopefully upgrade soon to something like Genelec 8350. I decided not to flush mount for now to make it easier to function as a live room and to maximize space. Monitor setup will be equilateral triangle with 5 foot listending distance. Speakers will be placed on stands behind mixing desk, about 2-3 inches in front of absorption.

Floor will be laminate. No windows, just one door leading into the sound lock. I won't get into HVAC design, as I don't have it all planned out yet, but I'm going for a central ducted unit with plenums etc. to reduce noise.

Bob Gold's calculator and AMROC look ok to my eye? There could be something I'm missing.

I'm sure I'm leaving details out. This is the first rough draft that I'm happy with. Would love to get your feedback. Thanks in advance!

Sorry, forgot to mention about the leanfractal design. These will be placed 1 foot off of the floor and will be 6 feet high, oriented vertically to diffuse in the horizontal plane. A few inches above these, there will be a horitontal row (16" wide approximately) to diffuse in the vertical plane.

Here are some better images I made that include the design of the leanfractals. Any feedback is greatly appreciated! Thanks in advance!

Hi Jeff, and Welcome!

This will function as both a control room and live room.

Not sure if you are aware, but that's rather hard to achieve... The acoustic response needed for mixing is very different from the acoustic response needed for playing and recording live instruments. Mixing requires a totally neutral acoustic response that does not affect the direct sound in any way.... and sounds terrible for most instruments. A good room for recording instruments is acoustically bright, more "live", warm and pleasant, with character.... and sounds terrible for mixing. Some people think: "Well then, I'll just make it in between! A bit neutral and a bit warm!" And what they get is a room that is no good for either instruments or mixing! If you insist on going with a single room approach, then your only real option here, is to make the room variable: Make adjustable acoustic treatment, so you can switch over from "neutral" to "live", for the two different situations. However, a much better option would be to build a studio with two rooms: one designed specifically for mixing, and the other specifically for jamming, rehearsal, tracking, etc. With nearly 400 ft2 for the building, you do have space for that: Both rooms would be smaller than ideal, but overall it might be better. If you could make the building itself bigger, that would be the best of all possible outcomes.

Outside will be 2x4 studs 16" oc with regular sheathing and acoustic caluk with r38 insulation. I might include an extra layer of dry wall in between studs, but I'm thinking I might could get away with not having this.

You need high isolation, so a single layer of 1/2" OSB on the outer leaf is not going to go anywhere near far enough to get that. So you WILL need more mass on the outer leaf, but I would not go to all the hassle of trying to do it between the studs! Just put an extra layer or two of something massive on the outside of the studs, before you put up your final finish outer surface. That's another thing: What is your final outer finish going to be? Vinyl siding? Stucco? You didn't mention what you want to use for that, but it is important...

Also, if you plan to have 11 foot ceilings, I doubt you'd be able to use 2x4s for your outer leaf. 11 foot inner leaf ceiling implies probably 13 feet or more to the eaves. Building codes usually specific 2x6 framing for walls taller than 12 feet, and often also for walls taller than 10 feet.

So you should re-plan your building with 2x6 framing for the outer leaf, and perhaps 1 layer of 3/4" OSB on the studs, then a layer of 10mm fiber cement board (with Green Glue), then your final outer finish surface. You could substitute a second layer of 3/4" OSB instead of the fiber cement board if you wanted. That would be the minimum mass that I would put on the outer leaf of a studio meant to isolate an 8-man rock band with live acoustic drums.

Inside room will be 2x4 16" oc with two layers of 5/8" drywall and green glue and acoustic caulk.

What size gap are you planning between the two frames? What type and thickness of insulation in the gap?

I don't need pristine sound isolation,

So there's no outside noise in Houston? It never rains? No thunder, hail, wind? No aircraft or helicopters flying over? No traffic, sirens, neighbors, lawn mowers, or people outside? No radios, TV? Nothing at all that makes any noise that could trash a recording session inside?

If we could get that down to 65 db, that would be fantastic, but 70 would be ok.

I'm not sure if you realize just how loud that would be! 70 dBC outside is louder than normal conversation level: two people standing outside your studio would have to raise their voices to have a conversation and be heard above the din coming through the walls.... And most of the sounds I mentioned above would make it through to the studio, to be clearly picked up by the mics during a recording session. A single helicopter flying past a few miles away would be plenty to trash a session. A radio playing in a car parked outside would do the same....

So aiming for 45 db reduction.

I would aim for at least twice that (subjectively), in order to have a usable studio. 55 is a good goal, and achievable.

Here's a very rough sketch of the lay out:

Many issues: first, your main entry door is directly where your speakers and front bass trapping need to be, and you will have to drag instruments and gear around the speakers and desk for load-in and load-out. I would suggest flipping the layout, so the main door is in the middle of the rear wall, leaving the entire front wall for the control room, with no interference.

Also, your mix position is way too far forwards, and the speaker geometry is no correct. The speakers need to be further apart than you are showing, and angled correctly to provide the right geometry at the mix position. Forget the famous mythical "equilateral triangle", and instead do the geometry sensibly.

Your "sound lock" is not necessary, and wastes a lot of space.

I chose a combo live and control room because the majority of the time it will be just me practicing and recording. Although I will have many times of recording other instruments as well where I will play the role of engineer instead of musician. Won't be as conveinent as having two separated spaces, but one big space is a better "bang for your buck" in my mind.

It might be "better bang for your buck" in economic terms, but certainly not in acoustic terms, for the reason I outlined above: the acoustic response that you need for a control room is rather different from the acoustic response that a live room needs. And trying to go for something in the middle will actually get you something that is no good for either!

Control room acoustics needs to comply with ITU BS.1116-3, or at least get close. Live room acoustics needs to be very different, with decay times that are three to four times as long (at least), and NOT the neutral, flat X-curve (or B&K curve) frequency response of a control room.

So in order to try and get the best of both world, I will plan on having adjustable panels made of 4" 703 that I can use to adjust absorption

It's not just absorption that you need to adjust, but also reflection, and in a room that is 17' long, diffusion as well.

and RT60 (yes I know, to some purists, this room might not be big enough for RT60 to come into play,

"Decay times" is a better term, technically, for small rooms, since there is no reverberant field in a small room below the natural Schroeder frequency, roughly. So it's not quite the same, in pure technical terms, but "RT-60" still covers the concept of decay times. And yes, it is VERY important, for both room scenarios (control room and live room). But RT-60 is not controlled only with absorption: as I mentioned above, it is also controlled with intelligent use of reflection and diffusion.

Live room RT60 will be around 0.6 seconds

For a room that size, 600 ms would be on the dead side. For drums especially, I would shoot for something much higher that that.

Control room with absorption will be RT60 of 0.3 seconds

For a small room like that, I would go for somewhat less: maybe around 250 or so. Take a look at this room, http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 It is much larger than yours, but I designed it for a decay time of 285ms, and it sounds very neutral, ideal acoustics for a control room.

Ceiling design: 2" 703 with a 4 inch gap between panel and ceiling. Will take up the whole ceiling space

Why do you want your entire ceiling to be absorptive at only one specific frequency range? What issues are you expecting in that range? Why do you not want to deal with the low end on your ceiling? How will you manage the vertical axial modes, and the tangential modes associated with your ceiling, if you only have that thin insulation?

Skyline diffusors (1.5" well, 4.5" max column length with diffusion of 1k to 4.5k) - 41 panels will be interspersed on ceiling

Ummmm... WHY? For what reason do you want the entire ceiling to only be diffusive in the high end? What issues are you expecting that you think you will need such a large amount of tightly focused diffusion? And how wil you prevent that from grossly messing with the smooth, flat, even, uncolored response that you need at the mix position?

All 4 corners will have panel absorption traps from floor to ceiling based Ethan Winer's design - can adjust front panel from 1/4" to 3/8" based on results of REQW, but I'm thinking the 3/8" might cover the trouble frequencies better. 1" 703 per Ethan Winer's design. These should be cheaper to make than superchunk bass traps.

sorry, but I'm totally not understanding the design concept here: You mention "absorption traps", but then you talk about extremely thin absorption that basically won't do anything at all for low frequencies. 1/4" of OC-703 will do totally zilch, zip and nada for bass trapping. You would not even be able to measure the effect, let alone hear anything. The same holds true for 1" of OC-703. Here's the actual data put out by the manufacturer for OC-703:
As you can see, below 500 Hz 1" of OC-703 does pretty much nothing at all. That is the real data as published by Owens Corning themselves, not something I made up. A one inch thick OC703 absorption panel will not do anything for your bass. Bass trapping requires deep, thick, large devices, many inches thick.

These should be cheaper to make than superchunk bass traps.

A bicycle is also cheaper than a Mack truck, but when you need to heavy transport, the bicycle is no use at all.... ditto 1" absorption as a bass trap... There's a reason why Superchunks were invented, and why they are so popular; because they are very effective, and they work! Consider this: if 1" 703 is enough, then how come no studios use that? Why is it that all pro studios and all properly designed home studios use a couple of FEET of absorption? Why do people go to all that trouble and expense, if 1 simple panel of 1" thick 703 would do the same job?

Walls will have tons of diffusion.

In a CONTROL ROOM???? Surely you jest... You should probably read the book by D'Antonio and Cox on the theory and practice of diffusers, to see why that is such a terrible idea.

The leanfractal design by Tim Ferry. The two 23' side walls will have a 15 modulation design on each wall.

Tim has a great design, and I have used his LeanFuser in several rooms (some of which are under construction right now), but I would NEVER use it the way you are suggesting.

According to Perry the critical distance from these should be about 5 feet

According to D'Antonio and Cox, that isn't true. The LeanFractal is a tuned design, using resonant wells, and it follows the same laws of physics as all other numeric-sequence diffusers. Including the ones about minimum wavelengths. You need 3 full wavelengths AT LEAST for the lobing to smooth over to acceptable levels. You mentioned 300 Hz: the wavelength at 300 Hz is 3.7 feet. So you need at least eleven feet from the face of the diffuser to anyone doing critical listening... such as you, at the console, when mixing, for example.

If I'm not wrong, what Tim actually says is that with the leanfuser, the field starts to even out after about 5 feet: I don't recall that he said it is fully even and smooth at that distance.

You can use the lean fractal on the rear wall, and that would be excellent, since it will be further than 11 feet from your head. But not on the side walls, and most certainly not on the front wall...

but I think the room will be big enough that I'm not freaking out about it

What makes you think that Cox and D'Antonio are wrong? Have you ever listened to a numeric-based diffuser up close, just five feet away? Especially one tuned down to 300 Hz?

The front wall will have 5 modulation design flanked by two on each end

Why, why, why on earth would you want tuned diffusion on the FRONT wall, right next to the speakers and your head? Please explain the design concept here. In what way will that help to achieve BS-1116.3?

To adjust the acoustics - 10, 4'x8' panels made of 4" 703 will be placed in the room

Where will you put those while you are tracking / rehearsing / jamming? They can't be inside the room, of course, so they will have to go out, but I don't see any area designated for storing those. Do you plan to leave them outside in the open air?

I decided not to flush mount for now to make it easier to function as a live room and to maximize space.

On the other hand, you have an unnecessary "sound lock" at one end of the building, which probably takes up more space than both soffits would, combined....

Are you aware of the massive gains in acoustic performance that flush-mounted speakers provide in a room?

Monitor setup will be equilateral triangle

The equilateral triangle is a myth. A very, very well established, and very well propagated, published, and repeated myth, but a myth nevertheless. I promise you that you will NOT be arrested by the Speaker Triangle Police if you have your speakers angled at 31° instead of 30°. Nor at 28°, or 35°, or 26°... nor even at 45° !! The reason you see that in so many places, is because it is dead easy to set up. But that does NOT mean that it is the best arrangement for all rooms and all speakers and all situations! Not even close. One size does NOT fit all.

To start with, the famous "equilateral triangle" places the apex in the middle of the head. And that would be fine for all humans who have their ears located on the front of their eyeballs! Because that's where the acoustic axis of each speaker is pointing, with the equilateral triangle layout. Take a close look. Human ears are actually located quite a few inches away from that, out on the edge of the head, so the acoustic axis of the speaker should be pointing there, not at your eye! The smoothest, flattest, best frequency response for any studio monitor is always ON axis, so it stands to reason that you want the axis pointing at the part of your body that is sensitive to sound, not the part that is sensitive to light. Aiming speakers at your eyes is about as logical as aiming the TV screen at your ears...

So, in reality, the CORRECT method for getting the speaker angle, is to set up the room so that the speakers are in the optimal location, and your head is in the optimal location, then rotate the speakers so they are pointing at a spot about 18" behind your head, which will ensure that the acoustic axis of the speaker is pointing at your ear lobe, or even a little further out, away from your head, which actually gives the best situation. If the resulting speaker angle happens to be 30° toe-in, then that's great and wonderful. But if it happens to be 27° or 33°, or anything else, then that's great too. Having a larger angle will give you a slightly wider sound stage and better stereo image. Having a smaller angle will give you a slightly wider sweet spot. But apart from that, there's no real difference, and the effects are small in any case.

with 5 foot listending distance. Speakers will be placed on stands behind mixing desk, about 2-3 inches in front of absorption

OK, so let me get this straight: You will have the rear edge of the speaker 3 inches in front of the absorption panel. The absorption panel will be 4" thick, and is in front of the diffuser. The diffuser is 7.5" deep. so your speaker will be 3 + 4 + 7.5 = 14.5 inches! Why do you want to create a massive SBIR dip at the mix position at roughly 200 Hz? Do you not like to hear snares and toms well in your mixes?

Floor will be laminate.

Floor will be laminate. No windows, just one door leading into the sound lock. I won't get into HVAC design, as I don't have it all planned out yet, but I'm going for a central ducted unit with plenums etc. to reduce noise.

Plenums don't reduce noise much. Silencer boxes do. You really should do the HVAC layout as well, since HVAC for studios is large, and takes up a lot of space.

Sorry, forgot to mention about the leanfractal design. These will be placed 1 foot off of the floor and will be 6 feet high, oriented vertically to diffuse in the horizontal plane. A few inches above these, there will be a horitontal row (16" wide approximately) to diffuse in the vertical plane.

I'm still not understanding the design concept of a room with no bass trapping and surrounded all sides with huge diffusers all tuned to the exact same frequency range.... I also do not understand how you intend to get the RT-60 time down to just 300 ms when the entire room is basically a giant reflective cave. The reverberant field will be nicely diffuse, to be sure, but the decay times will still be rather looooonnnnnggggg.....

Here are some better images I made that include the design of the leanfractals.

The ones on the rear wall are fine. The others: not so much!

Any feedback is greatly appreciated!

If that were going to be my room, I would flip the design completely, to have the room facing a blank wall, and the door in the middle of the rear wall. I would go for a rather more conventional design, not an experimental one, using traditional bass trapping to get your modal issues under control, absorption panels behind the speakers (which must be tight up against the front wall) as well as on the first reflection points, and elsewhere on the walls where needed, diffusion on the rear wall, a cloud over the mix position, and other treatment to tune the room as needed. I would also soffit-mount (flush mount) the speakers, and since you want a single room, I would make all of the side wall panels variable, as well as variable reflective covering over the bass traps, and probably some "flip over" panels hanging from the ceiling towards the rear of the room.

Of course, that's just me, and what I would do for my room. You might not want to follow the conventions at all, and perhaps you are able to mix in a non-neutral environment with extremely long and uneven RT-60 times, and non-flat acoustic response. I suppose some people can do that, but I can't. I find that my mixes sound terrible when I try to do them any place that isn't reasonably neutral. Which is why I would set up my room conventionally, with conventional layout and treatment.

- Stuart -

Thanks for your very thorough response Soundman2020!

You've convinced me to try and rework the space with a separate control and live room! I looked at the ITU-1116-3 information. Very helpful! It suggests the square footage of a control room to be 20 m2 - 60 m2. If I use 20 m2 for the control room, it looks like I'll have enough space left over for a good size live room. It would be nice not to have to worry about the adjustable acoustics. Is there information from ITU about live room design? That would be a good reference in my new design process. Also is there a recommended minimum size for a quality sounding live room? Places I've read recommend 4000 cubic feet minimum. Also, I suppose I'm confused about the role of diffusion in a live room? Seems like for a control room, you just need it on the rear wall. So in designing the live room, it seems that I need to spread out absorption to get my preferred RT60. After that, what role should diffusors play in the live room? I was under the impression that the more diffusors, the more reverbant sound field you have, the better your room will sound. I also was using diffusors over the majority of the surface area to handle flutter echo.

Also these (http://ethanwiner.com/basstrap.html) are the designs I was referencing for the bass trap.

I'll hopefully post my new plans soon!

Thanks again for all of the help!

You've convinced me to try and rework the space with a separate control and live room!

I use 20 m2 for the control room, it looks like I'll have enough space left over for a good size live room.

Right. You can go a bit less than 20m2 if you want and still have good acoustics. 20m2 is the minimum recommended, but that doesn't mean that it will be terrible if you only have 19.5m2

Is there information from ITU about live room design?

Not really.... live rooms are supposed to have "character" and "life" or "warmth", or be "bright" or "airy" or "subdued", which are subjective terms, and can't really be quantified. The idea is that your live room needs to be the way YOU want it to be, for the type of music YOU will be making. There are general guidelines, yes, in terms of overall decay times and overall sound quality, but even those are broad ranges, and depend on what it is you want for your room. It's one thing to have a room that sounds good for recording the intimate vocals for a soft romantic ballad, or for jazz or blues, and quite another thing to have good acoustics for recording a concert grand piano symphony, or a Barogue quartet, or the drums for Phil Collins song, or the electric guitar on a Carlos Santana number, or .... etc. The live room needs to be designed for what you want to do with it, unlike the control room which must be designed to be totally neutral, always.

Also is there a recommended minimum size for a quality sounding live room?

For most pro studios, it's in relation to the control room. You want the LR to be large enough with respect to the control room that you are able to fully hear all the subtleties of the LR acoustics when you listen on the CR speakers. If the decay time of the CR is LONGER than that of the LR, or at a higher level, then you won't be able to hear the LR "signature" in the CR: it will be masked by the CR's own acoustic response. Which is not a good thing, as you will not be able to hear the subtle stuff that otheres WILL be able to hear, when they listen in places with very short decay times, such as in their car or on ear buds... So the idea is that the LR should be larger (more volume) than the CR. The usual recommendation is that the LR room volume should be at least 3 to 5 times the volume of the CR, and the decay times should be at least twice to three times as long, but not so long as to be problematic for tracking. In other words, if the decay time in your CR is 250 ms, then the decay time in your LR should probably be around 500 to 750, but certainly mot less than about 400, or more than about 1000 (unless the room is really large...).

Places I've read recommend 4000 cubic feet minimum.

That's fine if the CR is around 1500 ft3 or so, but would be tool small if the CR is around 2500 ft3.

Also, I suppose I'm confused about the role of diffusion in a live room? Seems like for a control room, you just need it on the rear wall.

Only if the CR is big enough! There are rules of thumb about how close you can have your ears to a diffuser, if you are doing critical listening. For a small room, it is not possible to use numeric-based diffusion, because it is physically impossible to get your ears far enough away to avoid being in the "lobing" area, where there are still audible artifacts from the diffuser in terms of phase shift, level shift, timing shift, etc.

For a live room, you would need diffusion if the room is too specular and resonant or reverberant in some frequencies, for the type of tracking you do, but you don't want to reduce the total energy: you just want to spread it around, to avoid unpleasant reflections and artifacts.

So in designing the live room, it seems that I need to spread out absorption to get my preferred RT60

That's one approach, yes. But in a reasonably large room, you might want to make one end a bit more "dead" and the other end a bit more "live", so you can choose a good location at some point in the room for any scenario: instruments that need a "brighter" sound could be recorded more towards the live side, and things that need a more close, dry, deader sound could be tracked at the absorptive end of the room. You might or might not want the distant "ambience" coming back from the live end in that case, in which case you could use gobos to get the the effect you want.

I was under the impression that the more diffusors, the more reverbant sound field you have, the better your room will sound. I also was using diffusors over the majority of the surface area to handle flutter echo.

Diffusers don't make a room sound "reverberant". The room itself will be reverberant to the extent that the walls are not absorptive. Diffusion simply spreads around the energy in a diffuse manner, rather than an "echoey" manner. They keep the room sounding bright and airy, without sounding unpleasant. The interior of a large concrete sewer pipe is very reverberant, but not a good place to record!

I'll hopefully post my new plans soon!

Looking forward to it!

- Stuart -