John Sayers' Recording Studio Design Forum Archive

Hi. I have been reading your forum with great interest. It's already a godsend to me. I have found many answers I can use, but thought I'd clarify a few things on wall contruction/soundproofing just to make sure I've got things straight.

I'm considering renting space to start a mid-scale commercial studio.

The space would have a live room of roughly 14x 20 (rectangular now, but the two end walls would be angled), and a control room of roughly 17x25 (with splayed walls). I'd love to reverse the use of the two spaces, but I have neighbors next to the proposed control room, so I'm thinking of building a concrete and gypsum room with in a room for the CR, hoping to be a good neighbor via a concrete bunker and low SPL's (most of the time, and certainly during daylight hours when the neighbors are more likely to be in their offices).

There would be other rooms (office, lounge, etc) separating the noisy rooms (live and CR), which I do not propose to sound proof; hopefully the rooms themselves will provide some isolation. All ceilings are 13 Ft, so new ceilings will be needed. It's single story construction, built on a slab, so I have no upstairs or downstairs neighbors to consider.

The building is located roughly 150 yards from a passenger (no freight) railroad and call it 250 yards from I -95 (busy highway) . Overall, the background noise is noticeable and constant when standing outside. It's also pretty strong inside, albeit the old windows in this industrial building are basically open given all the cracks and single pane design, so it's really hard to predict how quiet I can get it with, say, glass blocks as replacement windows, and carefully plugging up all perferations in the building shell, which is 8" concrete block. I'm thinking I could work in this space if I can knock the basic noise down some, and build a good tracking booth for total isolation of some things when needed. As I said above, I'm also thinking of building the control room as a room-within-a-room (concrete on the outside, acoustically finaished within), too.

My basic question is can I safely use the concrete exterior walls (Live Room) and/or the concrete bunker walls (Control Room) as one leaf in a two leaf system, where I would basically build a freestanding stud layer, say, 6-8" inside the blocks to create an air gap, insulate that space, then cover with 2-3 layers of wall board? Does that count as a two leaf system? If so, does the use of block help in meeting your target of two different systems/treatments on each leaf?

What do you think of glass block as replacement windows (knowing they won't be opened)? I love the look, and crave the light, but have no idea whether they'll help control sound. They would seem massive, and I would think it might be good to put a layer of neoprene around them to cut transmissions from the block walls upon which they'd rest, but that's about as far as I've gotten.

Any thoughts would be greatly appreciated.

I'm in my "dracula" phase at the moment (12-hour night shifts) so I'll share some links that are pertinent, let you study them a bit, and in a couple days I can cover a lot more for you - basically, though, it sounds as if you've got a pretty good handle on the basics.

You may find that concrete between you and the neighbor isn't needed, if that wall is strong enough to add 3 more layers of wallboard to - then your air/insulation space and new frame/wallboard.

Ceilings can surprise you with flanking problems too, but those can be circumvented with a fully floated inner room.

Here's a few pertinent links, I'll have time for more in a day or two -

http://www.glassbrickcompany.com.au/pag ... nical.html

http://irc.nrc-cnrc.gc.ca/practice/noi1_E.html

http://irc.nrc-cnrc.gc.ca/ie/acoustics/projects.html

http://irc.nrc-cnrc.gc.ca/practice/noi2_E.html

http://irc.nrc-cnrc.gc.ca/cbd/cbd239e.html

http://irc.nrc-cnrc.gc.ca/cbd/cbd240e.html


These will probably answer a few of your questions, and likely raise a few dozen more - meantime, the more you can find out about your TOTAL building construction as it is now, the easier it will be to develop a plan of attack... Steve

Sooo, any thoughts? Have you had a chance to check out your existing construction details yet? Steve

I'm in shock for the moment; freaking out over the likely cost of soundproofing this space, and considering whether I can at least start out with making the existing main room (which is 8" block to the roof) double as a tracking/live room and control room. That way, I'd only have to finish the one room, at least until the studio gets legs and I can afford to finish off more space.

I'm wondering how I could measure the existing noise conditions. Can I rent equipment that tells me what the outside noice level is? If so, does it follow that, say, I have a background level of 40 db and a construction component (say, glass block) with a same or higher STC (40 or better), that I will obain silence (at least vis a vis that component)? I know that different frequencies act differently, and you can't capture the whole thing in one measure, but say the noise is 20. Then might I be safe in aiming for a perimeter rating of 40, on the teory of building in a large margin for error? I could double layer parts, and do glass block, air, and glass block. Maybe I'm at 80 then, and likely to be totally safe????


As to construction, here's what I know: The main room: 8" block walls to about 10 ft high, then 2 feet of windows (to be relaced with something transparent, probably glass block), then another 2 ft of 8" block. The ceiling is actually concrete, seemingly 6-8" thick, covered by tar. The floor is concrete, though with various hatches and perforation, that would presumably need to be filled, so they don't resonate. As to flanking issues, this room's walls go to the roof; there are no windows or doors (but I want to put in a double slider). There are various pipes that perforate the wall, but they can be cut out and the holes sealed.

I'm going to focus on this room for now, at least for the go-no-go decision on renting. My plan would be to operate in the main room most of the time. I'll build a really good tracking booth at one end (away from the external walls). I'm pretty confident I can get good isolation there.

The rest of the room would be for a desk (SAY, CONTROL 24). I think I'll put it on casters, so I can move it aside or to a neighboring room when tracking live. Thinking through whether the connecting/unconnecting will kill me; guess it depends what I put on the caster rig...

As to the main room, the total room is 32x16x 14 unfinished. First step would be to build a new gypsum perimeter at 6" off the wall; assuming air of 6" and gypsum of 3", that takes 1.5 ft, reducing the space to 30.5x14.5. (Please react to any of these diminsions as you see fit).

I'm thinking the drum booth should be at one end, say 14.5x 9 interior? That leaves the main space at 20.5x14.5x14 (assuming one foot for the drum room wall). From there, I would allow further loss of width to splayed side walls; I might have 14.5 ft at the rear, but only 12.5 ft at the narrow end. Is this getting too small to work in? I'm thinking small rock bands with headphones and a drummer in the booth, a violinist with a grand piano, maybe an accapella group (up to 16). Am I smoking dope? Can I ge the isolation and floor space I need?

If this one room is to double as both a control room and a live room, are there different ceiling dictates? I notice many control rooms have low and/or slanting ceilings, whereas most live rooms have high ceilings. I know I'll be dropping the ceiling somewhat to maintain dimensions of roughly 1x1.6x2.33. (I'm assuming you use average dimensions when splaying walls?) By the way, if I use these relative dimensions, my ceiling is down to 8.5 ft. Yikes! Where's all my space going?


Also, what's the case for turning the control room side ways? On the one hand, a wide room would seem good for minimizing relections off the side walls. On the other hand, it's nice to have a producer's position behind the engineer. Practically speaking, how close to a rear wall can the secondary mix postion be, assuming the wall is properly diffused. (Of course, depending how I orient the room, this is where I might want a big glass window looking out from the drum room. Urghhhh!)

But seriously, maybe I should orient the mix position side to side, take advantage of the width (glass windows on a booth shouldn't disturb as much if they're farther away, right?). Splaying the end walls is no big deal, since I have more room. But again, is it realistic to think that I and a client can be comfortable in a room with a front to back dimension of, say 13 ft (the previous 14.5 ft further reduced by RPGs and front wall treatment). Last question, how close to the front wall can my speakers realistically sit? That also impacts the side-to-side choice. I'd buy some new near fields in either case.

All thoughts genuinely appreciated.

If so, does it follow that, say, I have a background level of 40 db and a construction component (say, glass block) with a same or higher STC (40 or better), that I will obain silence (at least vis a vis that component)? I know that different frequencies act differently, and you can't capture the whole thing in one measure, but say the noise is 20. Then might I be safe in aiming for a perimeter rating of 40, on the teory of building in a large margin for error? I could double layer parts, and do glass block, air, and glass block. Maybe I'm at 80 then, and likely to be totally safe????

No. It is dependent on the noise and transmision loss at each frequency. Have a look at this thread for some idea.


Notice how the STC varies almost 30 but the loss at 50 HZ is worse for some walls that a person would think would be better. http://www.johnlsayers.com/phpBB2/viewt ... highlight=

Here's a short chart of comparative sound pressure levels to get a better idea of what's what -

http://www.americansaferoom.com/Common% ... cibels.HTM

BTW, two 40 dB barriers do NOT = 80 dB (wish they did) - more like 46 dB plus a small increase for air gap. Also, since the dB is a ratio, reducing 40 dB SPL by 40 dB will NOT = zero.

There are inexpensive sound level meters available, such as the Radio Shack ones ($40-$60) - unfortunately, these don't go low enough in level to check if a room is quiet enough, although they have enough OTHER useful functions for me to recommend the purchase of one by ALL who plan to mix/record music - For a site noise study, though, rental may be the only practical option. Whether your local area is large enough to have such gear available for rent is the next question.

It sounds to me like your building could be made usable with reasonable cost (I didn't say "cheap") - I think the blocks will be fine for an outer leaf - if you put a couple coats of heavy paint on them before doing the insulated space/drywall inner leaf it will help by a couple dB - the ceilings might be the tricky part.

With the train tracks that close, a floating room seems the best way to go - you could float the floor and use shims between pads and joists to accomplish leveling - see the "sticky" thread here on floating floors.

Doing that, if you were to float your walls AND ceiling on the already floated floor, you'd have all the isolation you need. Another way would be to use Kinetics RIM system for floor, building walls/ceiling frames on top of that. For that way, you would need to level the existing floor first though - here's a link to their pages -

http://www.kineticsnoise.com/

There are less expensive ways to do things, but those pages have some useful info for DIY approach if you do a bit of "xerox engineering"

Building your ceiling on top of inner floated walls will be the simplest, but may eat too much headroom in combination with a floating floor - if so, we may need to check on suspension devices from the existing concrete... Steve

Thanks for the references. Very useful.

Any thoughts on the question of side-to-side vs. front to back orientation for a control room. Also, any good threads you could suggest on ceiling design for CR and/or Live room?

Just went back and skimmed all your comments - in no particular order;

1:1.6"2.33 isn't the only good room ratio - there are several choices that will keep modal balance without using so much headroom, here's a spreadsheet I've found really helpful in that area -

http://www.studiotips.com/tools/MODESv2p.zip

The first page has some instructions on best use, and it also does Bonello distribution (which I'll explain later if you need it)

Your question about length vs width positioning - some of the larger studio designers favor facing the short way, but their reasoning (from what I remember) was mostly to cut down on the level of side reflections (inverse square law) at the mix position, which would be un-noticeable in a smaller CR - the rooms they're talking about are like 25 x 40 or so...

You mentioned using 3" of gypsum for your inner walls - that is 5 layers of 5/8 wallboard. Anything beyond 3 would be a waste of time/money, because other factors (like flanking, people breathing, door seals, etc) would have more effect. If your blocks are hollow, you might get better use of those two extra layers by gluing them against the blocks solidly before building the new frames inside.

For the CR, losing that much ceiling height could work to your advantage - if you do a ceiling that slopes up to the rear, it works for RFZ design - also, that large cavity (with sound proofing taken care of first) could be a serious bass trap - you would vent into the cavity by using 703 or rockwool around the perimeter of the ceiling, and using bass hangers above the inner, sloped ceiling (try a search on "hangers") (here, NOT on google )

Yes, the only non-computerized (extra-cost software) way to calculate for splayed walls/ceilings is to average - you can also (and should) do a point measurement in all three dimensions for speaker placement/head location -

Here is another useful spreadsheet from Harmon for modal calcs - it puts out a SPL graph at the first 4 harmonics of L,W, & H so you can see where peaks and nulls will occur (and stay away from either) -

http://www.harman.com/wp/index.jsp?articleId=131

(Check out the sidebar for more interesting stuff)

Your comment about moving the desk around made me a bit nervous - once I find a combination that works for speaker/head/gear position, I find it too time-consuming to get everything back exactly where it was to want to move it at all. Some dimensions are critical to fractions of an inch when you're trying to avoid modal problems. I think the idea of doing a CR first is the best one, since the majority of your time/work can be done there (except for the actual tracking of acoustic parts)

Ideally, you should look at (and work on) the space from outside in, but THINK of it from the inside out - by that, I mean that you first need to sound proof - this takes the two mass layers with air/insulation principle, and needs to be considered 360 degrees in every plane. Then, the "walls" you see from the inside would provide your acoustic environment and should be modally correct but NOT soundproof (that would only lessen your isolation anyway, by violating the 2-leaf principle) - since there is no "free lunch", any trapping/absorption you do will (somewhat) reduce your isolation (the stuff has to go SOMEWHERE) so for that reason, and because isolation is NEVER as good in the field as it is in calculators) your initial soundproofing envelope should be figured for at least 6-10 dB more than you think you need, that way the final result should be as good as you really DO need.

Speakers - if you're not afraid of building splayed walls, why not plan on soffiting your speakers? Even nearfields (most of them) benefit from "half space" radiation, this clears up a lot of extraneous sound field "mud" (and looks really cool for clients ) Plus, if you've not already bought your speakers you can look for ones that are adaptable to soffiting easier (no rear ports or passive radiators, no wierd shaped cabinets ) - Barefoot has some good ideas over on the Speakers forum, and John has diagrams of layout over on the SAE site - click the logo at the top right of this page, then click on The Recording Manual, then click on Construction, and finally click on the tab Speakers -

Your question, "Practically speaking, how close to a rear wall can the secondary mix postion be, assuming the wall is properly diffused" -

preferably several feet. Diffusion can be a dangerous thing - it makes things sound nice and spacious and live, but can muddy imaging to the point where your mix sounds good in the CR but crappy in the typical (deader) living room - most diffusors don't produce a really diffuse field within maybe 6-10 feet of the diffusor, so most small CR's would be better served with a "black hole" rear wall - This takes about 3 feet of space to accomplish, and it's been argued (by someone I respect) that you lose the ability to judge bass content when you do the "black hole" thing - however, both Tom Hidley and Phillip Newell recommend this for their "non-environment" rooms - the downside is, it's fairly complex to build the way they do it. John has done similar things with broadband absorbers over a large cavity with bass hangers inside to good effect.

I've probably missed a few dozen of your concerns, but "honey-dew" calls - remind me after reading this and we can do the next installment... Steve

Thanks so much for your last.

I think I'll try to center the control room on the short wall, since I dont seem to have enough overall width to do the 3ft of absorbtion behind the mix position that you suggest were I to orient "sideways".

I hear you on not using diffusion of the back wall. Where can I learn more about the black hole idea? Say I oriented the control room facing away from my vocal booth. If the booth had a pair of sliders, could I "vent" into the booth to create a black hole, or does that just cause bass build up? I guess to make that work, I'd have to recess the door leaves when they were open to prevent reflections.

Alternatively. I could face toward the booth, which has sightline advantages. However, that would put reflective glass doors in front of me (that used to be a no-no when LEDEs were the rage). Net ,net using RFZ concepts, I think I understand the following: If I build soffits for the speakers, and angle them more "shallowly", I will force the 60 degree sweet spot deeper into the center of the room, thus moving my mix position farther from the front wall, thus hopefully reducing the negative reflections were I to use glass sliders between the speakers, Does that sound right? How many feet off that glass slider front wall should I aim for?)

i haven't tried the mode work sheet yet, since my computer has security problems with the macros. I'll fix that. But I did see the Harmon one with the "humps". That seems like the second sheet to use. You use the first to set your dimensions, then Harmon to position your equipment. Or is it more iterative than that? Also, I assume you position yourself where none of the curves are too low, and ideally, where all four are relatively strong. Am I interpreting that right?

Forget the thing about 3" of Gypsum; that was the total of 1-1/2" per wall (i.e. a North plus a South, or an east plus a west); My gypsum depths would be a) 2X5/8 or B) 3/8 plus 1/2. Any preference? I see conflicting thoughts on differing thicknesses being good, but others that advocate max weight. Remember the other leaf will be (thickly painted) cement block.

I like the idea of the slanted ceiling for RFZ, but am intrigued by the idea of bass trapping, but wonder what it would do to my isolation needs. I've been thinking of suspending a ceiling on top of floated walls. I think the venting would negate the iso, right? Of course I build the CR as a cubic room within a room and suspend a slanted false ceiling below, but that sort of adds a layer and cost. Maybe angled and stepped clouds...

Forget moving the desk around. I'll rent the neighboring room for eventual live work, and just not spend on it at first.

Tell me more about your outside in/inside out thought. Are you saying sound proof the entire area (cement-air-gypsum) and then construct inner walls (as a third layer)? I really cant afford that. I'm counting on sealing the cement, and building the gypsum walls to be both sound proof and angled appropriately for inner treatment, the byproduct being to create air spaces of varying thickness.

Need to run. Please add what you can.

"Where can I learn more about the black hole idea?" –

Picked it up reading Philip Newell's Recording Studio Design, about $85 at Amazon, haven't seen it anywhere else. He and Tom Hidley use that approach - It's probably out of your price range, there's a lot of material and multiple baffles/layers, etc, involved – John's normal bass trap rear walls are next best thing and much cheaper – check out the studios under construction pages by clicking on the logo at the upper right of the main page -

"reflective glass doors in front of me (that used to be a no-no when LEDEs were the rage)" –

Still is – you might consider a portable gobo with absorptive side toward your desk, placed there only when NOT using the vox booth – (more correctly, placed there when mixing)

"If I build soffits for the speakers, and angle them more "shallowly", I will force the 60 degree sweet spot deeper into the center of the room, thus moving my mix position farther from the front wall, thus hopefully reducing the negative reflections were I to use glass sliders between the speakers, Does that sound right? How many feet off that glass slider front wall should I aim for?)" –

60 degrees is still 60 degrees - only way to move the third point of the triangle back is to make the front WIDER. I wouldn't change from a nearly equilateral triangle for speakers/head – John has mixed on 90 degree systems, but that would put you even CLOSER to the glass. My suggestion in the previous paragraph is probably more practical. See Barefoot's Wall Bounce Calculator in the Acoustics forum, try poaying with absorption coefficients as well as distance from wall...

"You use the first to set your dimensions, then Harmon to position your equipment. Or is it more iterative than that? Also, I assume you position yourself where none of the curves are too low, and ideally, where all four are relatively strong. Am I interpreting that right?" –

You're close on the first part – on the second, you do NOT want to be at either peaks OR nulls, but somewhere in middle ground both for speakers and head, and in all three planes. I typically copy the graph part to paint, then pick different colored lines and draw in possible locations that are in between the humps and dips in each axis, then draw this to scale on the room plan.

"My gypsum depths would be a) 2X5/8 or B) 3/8 plus 1/2. Any preference? I see conflicting thoughts on differing thicknesses being good, but others that advocate max weight. Remember the other leaf will be (thickly painted) cement block." –

A lot of the "conflict" has been discussed in phone conversations since that was written – I agree that mass is important, and that using all one thickness makes things simpler to build – however, I still think that different thicknesses improves the coincidence dip enough to consider accomplishing the same TOTAL thickness but with thinner/thicker wallboard. If I were having this built by contractor (instead of doing it myself), I'd go 100% with the "one size fits all" approach, so there's less room for error.

"I think the venting would negate the iso, right?" –

Right, that's why I talked about separate false ceiling and walls.

"Of course I build the CR as a cubic room within a room and suspend a slanted false ceiling below, but that sort of adds a layer and cost. Maybe angled and stepped clouds..." –

clouds will do nothing for mid or low bass, they stop around 400 hZ or so depending on spacing away from the barrier.

"Tell me more about your outside in/inside out thought. Are you saying sound proof the entire area (cement-air-gypsum) and then construct inner walls (as a third layer)? I really cant afford that. I'm counting on sealing the cement, and building the gypsum walls to be both sound proof and angled appropriately for inner treatment, the byproduct being to create air spaces of varying thickness." –

Yes, I am talking about a third layer - You can of course do it your way, but when you use the inner leaf of a sound isolation system as acoustic treatment, anything you "let through" to help acoustics is that much less that is blocked by the system as a whole. (Same goes for outside noise getting in) – Think of it this way – a panel bass trap (such as is created with a layer of wallboard over studs) works by allowing the bass to pass through, resonating the panel (releasing heat energy) – then, the panel converts part of the bass energy to moving air, which tries to get through the inner insulation (releasing MORE heat), part of it bounces back through the insulation, etc – but what penetrates the entire inner leaf then has only the outer leaf to stop it. Using two leaves of high mass with air/insulation space controls isolation, then you attack acoustics with lighter, splayed construction and more absorption behind (or in front depending on liveness required)

One way might be to construct your sound isolation envelope, then use the room with minimal acoustic treatment (absorbent, mirror trick, front gobo when mixing) and with the speakers used nearfield – then, when budget allows do the inner, RFZ envelope/soffits/ceiling bass trap – the rear bass trap wall would be included as part of the first round so the room wouldn't sound like a hip-hop party gone berserk... Steve

When we have spoken of a 6 inch air gap between surfaces, is it possible for the studs to stand within the 6", or does one mean a totally free six inches, then 4" stud, then the sheathing?

I have b een using your sticky spreadsheet called Room tune. I'll try to attach a recent saved version to see if I'm using it right. Basically I'm trying to get adjacent red lines to have gaps no smaller than 5 hz apart and no greater than 25hz apart. Do I remember correctly that it is more critical to get these constraints to balance at low frequencies and less important at high frequencies, or should I obsess until I get them to work across the entire graph?

The air gap can (and usually does) include framing members, although arguably you might see a small amount of improvement in field performance if the studs were on the outside instead of within the air space - just gut feel, I doubt it would amount to more than 1-2 dB, but I have absolutely zero fact to back that up -

I converted your Roomtune sheet graph to jpg so those without Excel on their computers can see the chart too -

Overall, with the exception I've circled, the axial modes look pretty good(all that Roomtune checks, I did it almost 20 years ago, and about the time I decided to upgrade it I found Jeff Szymanski's excellent MODESv2p sheet at studiotips.com, so decided against re-inventing the wheel)

However, I ran your dimensions through MODESv2 and when you include tangential and oblique modes, there is a slight lack of modal density at around 80 hZ with those dimensions -

If you want to play with that calculator, you can find it here -

http://www.studiotips.com/

Once there, click on Calculation Tools - Jeff's excellent sheet is the top one on the page.

Your understanding of what's important is correct; normally modes are dense enough by the time you get up to around 300 hZ that they don't cause much in the way of coloration in room response - an exception might be flutter echoes caused by parallel walls/floor/ceiling, but those are better tamed with either splayed surfaces or patches of absorption strategically placed.

Also, since writing that about the >5<20 hZ (a comment from Everest) I've learned that this is mainly for lower frequencies, and tighter tolerances are needed as frequency rises - usually not a problem, because the higher the frequency in a given room, the closer spaced the modes become anyway...

Anyway, here's your chart for a quick peek... Steve

Steve and Boiler 1,

When you recommended the Newell book to me, I went to the local book store in town and had them order it for me. Only took about 5 days and was $65 with tax and shipping! It's well worth the money.

Tom
First Bass Audio

Since my last, the guy who would be renting decided to keep that space, so I'm onto the next. This one is actually larger, but is on the second floor of a building on a main street. Two uber questions:

First, I need to isolate away from potential street noise. I can build a wall along the entire front of the space. Is there a benefit to leaving a 15 foot gap as opposed to a one foot gap on the street side of a well constructed wall? IOW, are there diminishing returns to gap size selection? I could sacrifice the street oriented space to office and hang-out space, so i'ts not a huge sacrifice. I'm wondering if it will help me with isolation to orient that way. If not, I might put the control room near the street and work like crazy to seal off the back walls.

Second, can I float a floor over the existing wood floor and expect good results? The floors are wood strips across large joists (look like 1-1/2x10 at least), themselves supported by a sizable steel frame. If the floated floor were neoprene, then 2x4s stuffed with wool, then 2 layers of 3/4 plywood, then carpet/wood, do you think I would be okay? We're talking drums, grand piano, and amps at the loudest. Below is a Japanese restaurant. Neither of us wants to know the other is there.

Or should I keep looking?