Help me make a final decision... angled walls or extra space

I've been back and forth on this for a while and i'm having trouble finalizing my decision.... please help!! This is for a one room deal. I don't plan on recording many full bands... it's not going to be a business....so the space is not a concern for having room... Just the most ideal acoustics. There are 2 ways I can do this, angle the walls or not. The finished inner walls (including all layers of drywall) will be 18' 6" X 12' 2" X 7' 6" if I DON'T angle the walls. This is a total of 1688 cubic feet. If I do angle the 2 long walls, I will go with the ideal of 7.5 degrees. This lowers it to a total of 1353 cubic feet. Acoustically speaking, is it worth losing 335 cubic feet of space by angling the 2 long walls?? Either way the room will be rather small. I will need a lot of absorption....but of course don't want it too dead. So maybe the angled walls would allow me to use less absorption. Since this is a live room/control room in one deal, I think it's much more important to make it an ideal control room. Or would the absorption required either way, get rid of flutter echo and as many peaks and nulls as possible and make the angled walls a waste of space??? I've considered angling half of the walls as a combination of both... but I don't see the benefit in that since I'm not concerned with having room, but only about having the best acoustics possible. :roll: One must be better than the other.. :?

Is this a performance or monitoring room? At that volume, there is not much a room reverb regardless and absorption will be hefty in either application. Why not splay the walls in a diamond type or sawtooth pattern? Andre

AVare wrote:

Is this a performance or monitoring room? At that volume, there is not much a room reverb regardless and absorption will be hefty in either application. Why not splay the walls in a diamond type or sawtooth pattern? Andre

It's a performance AND monitoring room (not at the same time of course). What would the diamond or sawtooth pattern offer me over the regular angled walls? more reverb?

What would the diamond or sawtooth pattern offer me over the regular angled walls?

More usable flloor area. As being a monitoring room at times, symmetry will be important. BTW 7.5 degrees is not any magic angle. You have to do a ray tracing determine the wall angles to prevent early reflections in the listening area. Good luck! Andre

Andre's right about angles; in less than optimum space, it's not practical to splay more than 6 degrees each side; with that, you'll not have to worry about flutter between sidewalls so you can use less absorption than would be necessary with straight parallel walls. You'd still need to create your (sorta) RFZ with patches of absorption, same as with a parallel pair of walls. You'd also still need to put at least a cloud, and sidewall first reflection points, and either a fixed or movable deep rear trap for a tight mix position. 1 foot splay for every 10 feet of wall length is the simplest way to get your 6 degrees per side. If you already feel you're cramped for space, you can use Andre's suggestion of "sawtooth" walls - you'd need to do at least 4 foot long sections or it will tend to "average out" and won't do as good a job on flutter. IT's also a PITA to build, and if you build the walls normal and add the "teeth" later you will get some 3-leaf effects on your isolation - Also, the splayed wall thing will leave slightly more width between walls at the rear of the room where you're likely to have more people - it's a tough choice when space is limited, but I would do the splay if it were my space; I don't like deadening an entire room to fix things that can be fixed while still leaving options (like degree of liveness) - remember, you'll also have parallel floor/ceiling to treat so that'll be more absorption as well. In your case, you also need to find a way to kill that boomy stuff from your floor - that will also color the sound of the room. If you don't have something like ETF, there is a freebie that can help you figure out what's going on in your room as is; http://homepage.ntlworld.com/john.mulcahy/roomeq/ One thing I'd do is to "shoot" your room as is, check out all the lower frequency peaks, then drill about a 5/8" hole in one of the boomier places and force as much of this (the 29 oz tubes, not the squeeze tube) http://www.quikrete.com/catalog/GrayConcreteRepair.html into the hole (don't stop til it squeezes back out the hole, then strike it off with a trowel or putty knife) You should first tap the spot with a rubber or plastic hammer and see how loud it is; then re-check AFTER the hole is filled and treatment has cured. Then re-shoot the room and see what's happened to the peaks; most will still be there, because they're room modes - you'll probably only see one peak that changes before and after. I've not used this stuff nor have I had to do the type of repair you need, that's why I'm telling you what I would TRY, and only one spot til you find out if it helps. You might try PM'ing Rod Gervais to see if he's got any better ideas... Steve

OK, then it's settled, I will keep the plan to angle the long walls in order to reduce flutter and keep space open at the back of the room. The RFZ zone I'll accomplish with traps... the traps in the back of the room might be removable so that I can re-move them while tracking and then put them back for mixing. When tracking the main concern is probably flutter echo...so if I can minimize that and make my room sort of lively, that's probably the best situation for me. I'll probably have a cloud over the mix position and a cloud over the drum set to take care of ceiling/floor reflections. Then I'll bring in more traps accross the back and corners for mixing. The first reflection points on the long walls I may make removable as well. As far as the concrete, I'm afraid that it might be similar to Andy Eade's thread... http://www.johnlsayers.com/phpBB2/viewt ... &start=195 In my sump pump pit there are 3 plastic pipes coming into the pit. I think they might be causing the ringing sound...and I don't think there's anything I can do about that. Since I will be angling my walls, the worst part of the wall on one side of the room will not be in the room. But there still will be areas that ring in the room. I guess it can't hurt to drill through the concrete and see if I can see what's going on down there? I'm waiting for a response from the builder about it...but so far, nothing.

You're right, if your booms are because of drainage pipes it prob'ly wouldn't be a good plan to fill the pipes with mortar :? Here's a fairly inexpensive idea, which I have NO IDEA if it'll work - my newest electronic stud finder has a "deep scan" mode; I know it'll find studs through 3/4 plywood and 1/2" gypsum, maybe you could see if one would find your "holes" well enough to "map out" where they are, and if it ends up looking like some straight lines then it's likely pipes and not random voids. I know a "normal" stud finder won't do this, the model I have is the Zircon Contractor, Multiscanner Pro - it also detects AC wiring (not in conduit), and metal. If you don't already have one and intend to cut into any walls, it'd be a good idea to get one whether or not it'll scan your concrete deep enough to tell anything. Meantime, if you wait til your builder calls you back it'll be a long wait in most cases - I'd keep calling til he either returns your call or answers the phone... Steve

knightfly wrote:

You're right, if your booms are because of drainage pipes it prob'ly wouldn't be a good plan to fill the pipes with mortar :? Here's a fairly inexpensive idea, which I have NO IDEA if it'll work - my newest electronic stud finder has a "deep scan" mode; I know it'll find studs through 3/4 plywood and 1/2" gypsum, maybe you could see if one would find your "holes" well enough to "map out" where they are, and if it ends up looking like some straight lines then it's likely pipes and not random voids. I know a "normal" stud finder won't do this, the model I have is the Zircon Contractor, Multiscanner Pro - it also detects AC wiring (not in conduit), and metal. If you don't already have one and intend to cut into any walls, it'd be a good idea to get one whether or not it'll scan your concrete deep enough to tell anything. Meantime, if you wait til your builder calls you back it'll be a long wait in most cases - I'd keep calling til he either returns your call or answers the phone... Steve

Unfortunatley, I don't have a phone number to the builder...only to a salesperson... I can't find a phone number to anyone but sales.. They are supposed to be helping.. but so far, nothing. I'll keep harrassing them though :lol: The stud finder is a good idea... I was gonna buy one anyway and I found one at lowes that said it could go through a couple inches... Actually this one says it can go three inches to find pipes.. http://www.lowes.com/lowes/lkn?action=p ... lpage=none

Careful; it says METAL pipes. May not be so with plastic ones. That looks like one model down from mine, and deep scan sounds about the same. Seems like mine was a few $$ more, like mid-30's, don't recall for sure... Steve

Well... the latest message from the salesguy who was to contact the builders has told me... sorry, but there's nothing they can do for me. They can't give me the building plans or tell me what's going on underneath the slab? It's only 7 years old.

This seems to be the perfect thread to add some info and ask some questions of my own of… adding splayed side wall, varied depth broad band slot resonator (Helmoltz Resonator) to the topic AND considering different size slot resonators on either side wall. Or should I just say purposefully, “high jacking” the thread. I admit I may be overly concerned the choices, that is obsessively thinking about it as I fall asleep. Since I’m applying for a building permit SOON I need to come to peace with which “road of acoustic treatment” I will walk. I’ve not dropped slot resonator yet from my options but am really thinking about dropping the idea, I've read how effective they can be and the also look really cool. 8) My room will be basically the same as Toms, the all in one room. But my room will be slightly smaller than Tom’s… 14 ½’ L, 8 ½’ W and 7 ½’ H (or so) which is under 1000 cubic feet…depending if or not I incorporate an “L” shape into the room. I did a lot of “hunting” for info on this topic a few months ago and came up with several answers to my own question, mostly from posts of John. Please feel free to further discuss the following, as previously I only discussed this with myself. :oops: 1. What’s the best degree of splay for side walls? I can’t find a link to the post where John (and others) talked about this but: 12 degrees minimum, 15 is better; increases of 1 or 2 degrees has little effect, increases by 3 (so 18 degrees would be next) has an effect AND if you can afford the floor space, 30 degrees is best (and max?) for splayed side walls. But most of us do not have floor space so best is 12 degrees splayed, 6 degrees each side wall. 2. In a varied depth broad band slot resonator what’s the minimum depth the deepest section should have? 8” is effective; 12” seems to be most common and go as deep as you can if you have the space. Of course this depends on the desired frequency range. 3. What effect does having a varied depth slot resonator on only one side wall OR having 2 different size slot resonators or absorbers on the 2 side walls have on the acoustic symmetry of the room? This question I could not find an answer for. I’ve seen quite a few designs and rooms only having side wall slot resonator OR different size slot resonators on either side wall. This really makes me question whether these rooms would be acoustically symmetrical because different frequencies on either side of the room would be getting sucked out. 5. How far back in the room should the splayed walls go? Ideally walls should be splayed to the back of the room BUT minimum they should be splayed to just behind the mix position (38% of length of room is mix position plus ??% say 50% or more) and then parallel out. This would be saving square footage to the room. Recapping Tom’s options and adding some. *Note Panel absorbers listed below could be replaced with other acoustic treatment but this seems to be the best DIY treatment option. 1. Build the room out rectangle and treat with panel absorbers. This is obviously not the best choice. 2. Build splay walls (however far back), the drywall is the finish; add panel absorbers for absorption and to help create the RFZ. 3. Build room rectangle then use side wall varied depth broad bad slot resonators to splay how ever far back in the room (this could use inside out walls, but I’m not choosing that) 4. “Tilt” the room off by 6 degrees… one inner side wall is parallel to outer wall, other inner side wall is off by 12 degrees to outer wall… front wall of by 6 degrees from outer wall. And say this all has drywall finish and room has panel absorbers. 5. Same tilt as #4 BUT there would be a varied depth slot resonator for the 12 degree off wall… the inner wall here would be parallel to the outer wall and the slots would make the angle, of course slot wall will lesson isolation of room 6. In addition to #3 or #5 put different size slot resonator(s) on other side wall to accommodate shape of room, windows, doors or other obstacles. So I’m left asking myself: Is there that big a difference? Can I get and equally smooth sounding room from either panels or slots within a splayed room? Even though I really like the idea and look of slots is it worth the extra time, effort and money? How good of a chance could I screw up a slot resonator? Should I just take a chill pill? :roll: Looking forward to any response as I previously posted somewhere else with no response to this topic or type of questions. :cry: Hope it all makes sense enough to comment, Marc :twisted:

Marc: Ouch! I am busy at the moment but wait for corrections. Either from me or someelse on the forum. Major redirects needed. Andre

Ouch! I am busy at the moment but wait for corrections. Either from me or someelse on the forum. Major redirects needed.

No problem Avare, I can wait. Even though I will soon be applying for building permit (maybe Friday), the permit will only cover my "outer walls" and with any slight changes in what I actually build, my architect assured me would not be a problem (I hope). Summarizing what my delima is about : whether to use splayed slot resonator walls (and how even or unevely sized each side wall could or should not be) OR just splay the walls and use DIY panel absorbers. If I have time tonight I'll work on some diagrams of my specific room options... or atleast what I think are options. Marc.

Okay here goes:

1. What’s the best degree of splay for side walls?

There is no genereic "best angle." Walls splayed to prevent flutter echo t 6 degrees minimum. That is only universal accurate constant. Angles for creating RFZs are determined by ray tracing, on a specific room by room basis. The numbers you see for these angles are "typical averages." Think of the "typical human" with one ovary and one testicle.

2. In a varied depth broad band slot resonator what’s the minimum depth the deepest section should have?

There is no minimum depth, other thatn 0. The depth is determined by the desired absorption frequency range.

3. What effect does having a varied depth slot resonator on only one side wall OR having 2 different size slot resonators or absorbers on the 2 side walls have on the acoustic symmetry of the room?

It reduces it. How much depends on how the different the two sides are, the frequencies involved etc.

5. How far back in the room should the splayed walls go?

As in one, it depends ON THE PURPOSE of the splays. If flutter echo reduction then it is reasonable to splay yhe entire wall. IF for RFZ creation, then as determinde by ray tracing.

Summarizing what my delima is about : whether to use splayed slot resonator walls (and how even or unevely sized each side wall could or should not be) OR just splay the walls and use DIY panel absorbers.

With the room size you have, and not seeing the detailed plans (if you are good), or chicken scratches (if you are like me), I would: splay the side walls between the monitors and the listening position; put lf absorbers behind the listening postion and below the monitors; after making initial room performance calculations for required absorption. You did not mention it, but to make it explicit, with a room that size, diffusion is not appropriate. I don't know what my schedule is like in the next few days, so don't hold your breath waiting for my responses. Good luck! Andre

Andre, 1st thanks for responding with me on this subject.

You did not mention it, but to make it explicit, with a room that size, diffusion is not appropriate.

Thanks :D :D I may have read a statement like that before, but I did not retain it :oops: That gives one less reason to use slot resonator side walls :roll: I started another thread to deal with this here: Marc's Patio & Garage Studio: Acoustics Marc