Deadline Has Been Set (and Re-Set...) Theater Build - Page 6

Time just flies on these things, even if you do a little every day. I'm coming up on 8 months on my project soon and I doubt I'll have a usable pre-version ready by this time next year. My deadline is set for mid-2017 (to have time to save up for proper screen and proper projector - have temporary ones to run on before then).

Interesting - why did you go with 2x8s for the span? Are you bracing them in anyway? Are you going to do the same for your riser?

Keeping the spanners less than the full height allows you to use the riser as a bass trap, I would put a mid span support to avoid any bounce.

I used two layers of 2x6 crossed for my riser/basstrap.

Definitely no bounce:D

if it has a paper backing you can staple to the top edge. If seen some say it doesn't matter if it falls, I'm not sure of the science one way or another.

Acoustically, it doesn't matter if it falls. Cavity resonance is reduced whether the insulation is low, middle or high in the cavity.

EDIT: This is true for transmission loss, however when a cavity is being optimized as an absorber I'd ask Dennis.
Edited by Ted White - 10/28/12 at 6:25pm

I'm not concerned about the effect on cavity resonance it is the impact on the effectiveness as a bass trap. My gut says it is not an issue, but I've seen professional plans with an air gap at the bottom connecting all joist bays.

Shouldn't the cavity be completely filled with insulation?

Never assume the pros know what they are doing. It should be completely filled. The density if the insulation used is the key, though. And it's different desities for glasswool and rockwool, to complicate it further...

I have to say, we see our fair share of isolation designs by a host of pros, and sadly many are just flatly poor designs. So I think it's good to get some background education on these things so as to be better able to sniff snake oil.

The Pro I cited was our resident Guru.

So your plan calls for the bottom 4" of your riser to be free of insulation? Is this designed as a pressure absorber with holes cut out of the platform near the rear wall corners?

Pro does not mean expert - pro means they do it for a living. Expert is another matter. Just like amateur does not mean bad, it means 'doing it out of love' instead of making your living on it.
There are plenty of amateurs around that knows things a lot better than many pros... forums like this one is the definite proof of that.

Counter intuitive? Of course, that's part of the sale for sure. Assuming that since you're paying for it - it will be better (or faster) than you would yourself.

But if you don't know yourself - how can you judge? Some pro might have you install a LEDE kind of room and may be quite good at building LEDE rooms, but it could still be the case that for your particular room, it might not be close to the optimum acoustic build. But as long as it gets better than what you had, the pro behaving like he knows his stuff and it costs sufficiently enough - you'll have plenty of placebo effect in enjoying the room for sure.

For comparison - how many pros do we have out there designing loudspeakers - and how many of them is actually close to ok? And how many are sold on looks and price tag?

A lot of acoustic pros have their own style which they try to adapt to whatever room they get... sticking to the same products to use etc. But it would be different to as a number of them and compare their
suggestions - I'm sure you'd get quite different suggestions. You might still be happy with any of the resulting rooms, though. But it does lead to the question whether they really knew the outcome beforehand or it's more a matter of "it worked of this time too". Not claiming this applies to your particular set of experts, of course - how would I know? This is just a general statement.

Myself, I brought in the guy who designed the loudspeakers I will be using and I have seen a number of his room designs before and they are quite varied. Had I done the room myself after having looked around at previous designs, I would have done some things I now didn't have to after he crunched the numbers and tested the stiffness of existing walls&ceiling. So he actually saved his own fee in just stopping me from doing some acoustic fixes! And he definitely knows where his speakers benefits from having absorption and/or diffusion put up relative to the listening position(s).

I've never seen any bass-absorbers with a free passage in them anywhere before, so while I don't claim it can't work - I very much would like an explanation of what would be the benefit in physical terms.
It intuitively feels as if someone though it was needed for the sound to make it all the way in there... (sorry!)

Audio in particular doesn't seem to obey those rules, nor that you should be able to prove your claims. But I wish you had been correct.

Well, to start with there's probably more people to choose amongst in Los Angeles alone than in my entire country, that yields some differences.

Besides that... I rather pick the words "healthy scepticism"

If they weren't ok, I'd be going for B&W 800/802s, they are the closest in performance I could find around here. More money going into looks on those, though.

Well, I'm more used to rooms made for 2-channel performance, so that's the kind of rooms I have explored elsewhere.

So would I be if I had the money for a 140" Clearpix2 screen and a 4K-projector, but I'm saving for those and that will take a few years if the prices don't drop. I did start my temporary projector for the first time yesterday to figure out where in the back wall it has to go.

Not sure if you were looking for more suggestions to keep the insulation off the ground, but I used insulation support wire (made for supporting flex duct and insulation in overhead joist space). It worked very well.

Here is a like to the HD product...
http://www.homedepot.com/buy/building-materials/accessories/simpson-strong-tie-16-in-oc-insulation-supports-100-pack--is16-r100.html#.UI7FZ8XA8Yk

Thanks, I hope so. It's not going to be as designed as a lot of people here have. We don't build houses the same way here, so there's not carpenters around that can do the kind of woodwork I see in the threads here. At least not that's available at normal rates. And I'm not skilled and patient enough myself. And honestly, I don't care if a board is slightly chipped or slightly off level - I want to use my room for film, music and games, not to adore my ceiling.

Also, most people seems to be building rooms from scratch and can keep them empty, I have to constamtly shift the chairs, electronics and things going into the machinist's room in the end around, so it does not make good pictures.... So I think I'll avoid getting bashed by not making a thread.

Room is 14.67'x18.67' with a floating floor and will have three seats in an arch in front and two separate in the back on a 12" riser/basstrap. Back wall will be acoustically 'transparent' 19" thick stuffed with insulation as an additional basstrap. Front wall is partially dampened and the sidewalls feature diffusion up to ear level of front row. From there on we will not decide until it's done and any remaining flutter echo has been measured. Outer walls of the theater room+the machinist room are masoned light concrete blocks with a single layer gypsum board (dual layer would put the resonance frequency wrong and I'm not soundproofing as it's a standalone building). So not a single drop of green glue.
Edited by Nightlord - 10/29/12 at 12:43pm

I'll consider it. Yes, enough off-topic in your thread now.

Nice! I ordered a Jamestown screen with the Seymour XD material (130" wide 2.35:1) as well. Did you go 16:9 or scope? Ordered mine back on the 10th with the hopes that I get it in plenty of time to have it up by Thanksgiving. I think he told me 15-20 business days when I ordered. If that's true it should show up sometime next week.