[ScottMayo]

I'm in a position to build a room for a home theater/audiophile 2 channel system. Under the premise that nothing sounds good in a bad room, I'm trying to head off acoustical problems before they start.

The only constraints are, the room can't be over 16' wide (or the addition could get to close to a property line), and, I want the room to be buildable by perfectly normal contractors (which probably means I need a *good* reason not to have surfaces at right angles.) Ceiling height, and room length, are adjustable, though a room over 20 feet long could raise issues. Ceiling height can probably go up to 13'. The resulting room has one more constraint: when the music is off, it has to comfortably hold up to 10 people in a fashion that lets them see and talk to each other. So I'll be using couches that can be easily moved by 2 people.

The room won't have windows, and will only have one exit, which is currently spec'd as an open archway, 4' wide and up to 10' high in the center. Wall materials can be whatever I can afford and makes reasonable sense: if someone convinces me that I should just stick 6" thick sheets of foam between the 2x4's, and skip the drywall, that's possible. Building a true anechoic chamber is probably not in the cards in my price range, though.

So what makes sense? I've read that adding angled walls doesn't really help matters; however, every live theatre I've been in has flaring walls. I've been running mode calculators, and Len=18.5 Wid=15.5 Hei=10 doesn't look too bad, but I have no idea what a 4' opening 5' down one wall is going to do. What about wilder possibilities, like having the ceiling in back come down at a 45 degree angle, to channel all rear wall reflections through a whole in the floor and into a big pile of foam in the basement? Do "tricks" like that ever work?

Suggestions very welcome. If your suggestion involves buying something you just happen to sell, be up-front and say so.

[Ethan Winer]

Scott,

> I want the room to be buildable by perfectly normal contractors <

My home recording studio has angled walls and an angled ceiling, and it was no big deal for the contractor. He did curse a bit at having to compute how to join the angled wall and angled ceiling where they meet, but there was no extra charge or anything like that. That said, you can get perfectly good results in a rectangular room.

> if someone convinces me that I should just stick 6" thick sheets of foam between the 2x4's, and skip the drywall, that's possible.  Building a true anechoic chamber is probably not in the cards in my price range, though. <

You don't want an anechoic chamber, and you certainly don't want any foam in your walls!

It's a given that you want good sound inside the room. But how important is isolation to keep the music in and other sounds out? These are opposing goals, and increasing isolation means you need more bass trapping inside the room.

> I've read that adding angled walls doesn't really help matters; however, every live theatre I've been in has flaring walls <

Angled walls, and a ceiling that rises from front to rear, are both good acoustically. But the goal is not to slavishly immitate a commercial theater. The walls flare in a theater partly so they can fit more people in and still keep the screen visible in the back.

> I have no idea what a 4' opening 5' down one wall is going to do <

If the opening is in the center of the rear wall, considering the room to be 18.5 feet long, it will not be a problem. A big opening in a side wall is less desirable because it will affect symmetry for at least some of the listeners.

> channel all rear wall reflections through a whole in the floor and into a big pile of foam in the basement? <

Not a good idea. Bass waves cannot be directed that way. An angled ceiling is good, but if anything it should start low at the front and rise continually toward the rear. With your 13 foot height limit, that allows a nice amount of angle.

> If your suggestion involves buying something you just happen to sell, be up-front and say so. <

I manufacture and sell acoustic treatment, but so far your questions have all focused on design issues. And it's good that you're thinking about that stuff now!

Do you have a proposed floor plan? That would help a lot, especially if it shows where you plan to put the speakers, the seating, the wall opening, etc.

--Ethan

[ScottMayo]

Do you have a proposed floor plan? That would help a lot, especially if it shows where you plan to put the speakers, the seating, the wall opening, etc.

I did until yesterday, then I realised that I want the room to comfortably seat ten people when it is NOT being used for audio reproduction, and that these ten people should be able to see each other. As a result, the furniture layout becomes bulkier, the room is getting bigger and I don't have a floorplan yet.

I *do* want an anechoic chamber; I just can't have one. I want the sound to stream past me and never come back. Echoes lead to standing waves, smudge and squashed soundstages. There can be tolerable echoes that don't hurt too much, but there can never be good ones.

That said, I can't afford such a room, so now I want a room that will at least minimize the problems and enable me to buy less of your products. Actually, that's not the right way to say it: what I want is to find the price tradeoffs: if it's more expensive to build a wall with great acoustic properties, than it is to slap up drywall and then add a few more bass traps, then you can expect to make more money.

and you certainly don't want any foam in your walls!

At least one of the walls will be exterior and is going to have to have insulation, if for no other reason than Massachusetts winters are more or less what you'd expect. There's going to be something in the walls. Ideally that something will also help with the sound.

Instinctively, it seems to me that it should be possible to build walls such that they cause fewer problems than a reflective sheet of drywall. As far as I'm concerned, the only given for wall construction is 2x4's or 2x8's, vertical, parallel and 16" apart. If I thought that putting up layers of fiberglass and air gaps betwen the studs, and covering it all over with cloth, instead of drywall, would be the way to go, I'd do it.

Soundproofing is a goal. My wife has aquariums all over the place; there are water pumps everywhere. I live life at 60Hz, most of the time. I hope to have this one room free of that; I also don't want to hear my kids' Playstation when I'm cueing up Vivaldi. I mean, there's no point in a flat room if my kids are leaking noise at 400-2000Hz into it, in the form of annoying gamesystems. So, where possible, I'm surrounding the room with other spaces that are quiet and sound-deadening: closets, bookshelves, etc. But I'm prepared to spend something for a better solution; I can't get them to accept that headphones were *made* for Playstations... just the way sledgehammers were.  

[Ethan Winer]

Scott,

> I *do* want an anechoic chamber ... I want the sound to stream past me and never come back. Echoes lead to standing waves, smudge and squashed soundstages. <

For music reproduction you really do not want to make the space totally dead. I agree that you cannot have too much absorption at low frequencies, but you can definitely make a room too dead sounding at mid and high frequencies. A better goal is to design the room so it's proportioned to have a good sound. That makes treating it easier too.

> At least one of the walls will be exterior and is going to have to have insulation <

Yes, of course. What you want inside the walls is standard fiberglass insulation, not foam. That's all I meant.

> it should be possible to build walls such that they cause fewer problems than a reflective sheet of drywall. <

Yes and no. At some point the wall has to be massive/rigid enough to block sound from getting in and out, and to keep the heat in and the cold winter out. The problem is the more rigid the wall, the more it reflects low frequencies inside the room.

> If I thought that putting up layers of fiberglass and air gaps betwen the studs, and covering it all over with cloth, instead of drywall, would be the way to go, I'd do it. <

You really do need both the inside and outside barriers. So the best plan is to build normal walls as usual, then apply appropriate treatment on the inside, within the room.

> I'm surrounding the room with other spaces that are quiet and sound-deadening: closets, bookshelves, etc. <

Excellent. I woudn't worry do much about the game noises, because what travels through the walls the most is very low frequencies.

--Ethan

[ScottMayo]

You really do need both the inside and outside barriers. So the best plan is to build normal walls as usual, then apply appropriate treatment on the inside, within the room...

I don't really doubt Ethan's right, but he also sells a product that works best with traditional wall structures. So I'm looking for second opinions.    Anyone have experiences with special wall construction, to head off problems instead of fixing them after the fact? I still have some trouble believing that drywall, a material designed to be cheap and easy to install and paint, and with no other redeeming characteristcs, is really the ideal for an audio room. I mean, there's not much in nature that really blesses the cheapest possible solution; why would drywall be an exception?    

[Ethan Winer]

Scott,

> I'm looking for second opinions <

I'm not offended at all. But your goal is my goal, and I'm not here to sell stuff. I tell people regularly that if they have a drop ceiling they should pack as much fluffy fiberglass up there as will fit. That reduces the amount of on-wall treatment they need to buy. I even make that point in the MiniTraps video on our web site.

> > there's not much in nature that really blesses the cheapest possible solution; why would drywall be an exception? <

Good one. Seriously, you can get a little extra bass absorption from drywall that's hung on resilient channel. But the absorption is fairly narrow band, and follows the natural resonance of the materials. You can build wood panel bass traps into the walls, and that's not a bad idea. But it's a lot of extra work and, again, the absorption is fairly narrow.

If anyone else has some good ideas about this, I'd love to hear them too.

--Ethan

[Marbles]

Here is what PS Audio did when faced with building a listening room...

http://www.psaudio.com/articles/listening_room_1.asp

The room was pre-built a bit larger than yours and has cement on 5 walls (flloor, ceiling and 3 walls).

They do have some interesting techniques to make it sound pretty good that you might be able to use.

[Marbles]

See also some of these products:

http://www.owenscorning.com/around/sound/products/index2.asp

[pjchappy]

This product:  http://www.owenscorning.com/around/sound/products/solserene.asp
would be a great idea to cover a wall that has acoustic treatments, especially people using the LEDE concept.  Would look MUCH better.

p

[brj]

Since you are starting from scratch with a new room, you might want to take a look at some of these options:

   - Owens Corning Acoustic Systems
   - Quiet Solution Engineered Panels

I don't know anything about them other than what I've read on their sites, but they both seem to offer larger scale solutions suitable for installation during construction.  Look at both the residential and commercial sections for each web site.

If anyone has any first hand experience with any of these products, I'd be curious to hear your thoughts.

[ScottMayo]

This product:  http://www.owenscorning.com/around/sound/products/solserene.asp
would be a great idea to cover a wall that has acoustic treatments, especially people using the LEDE concept.  Would look MUCH better.

This idea might be a keeper for ceilings. On walls... I wonder. You go from washing dust off of walls, to vaccuming them - and hoping you don't push too hard, deforming the cloth. This would make me nervous. And when your friend's three year old trips and tears about 6' of wall down...

...No. The more I think about this, the more it sounds like Not The World I live In.

[pjchappy]

I wonder how the material is. . .if it is tough and could be washed.

I guess my suggestion wasn't specifically for you, but for those w/ foam all over the walls.  THAT usually looks ugly IMO and covering it all w/ a layer so it looks like a wall would be a decent looking solution.

p