Acoustical Treatments Master Thread - Page 225

hi everyone, i would like some opinions on my setup and if additional bass trapping will fix the issues im having. my room is 19' long x 15' wide x 8' high. i built everything myself, double drywall, greenglue, oc703 all around the room (42" high), front wall has it floor to ceiling and ceiling. my sub is located in the front right corner. i'm using anthem ARC room correction eq which sounds very good. my question though is in regards to adding corner bass traps to my front wall (superchunk method). basically, the sub sounds amazing when im sitting in the second row of my theater at the rear left corner. that is where i usually sit so everything sounds perfect. but if i move to the rear right side, bass is no where near as powerful. same goes for the primary LP which is closer to the screen. so it seems that bass energy is a lot more powerful at the rear of my theater near the walls, but also in the opposite side of sub placement. will corner bass traps to the front of the room help in any way? unfortunately i can't add anything to the rear of the room.

any suggestions/help?

thanks!

Better than a few, worse than many. Definitely stay away from anything that is not fire retardant rated and purpose built for acoustics. And you can probably get more impact for the same $$$ using more efficient materials like fiberglass.

Lots of great info in this thread. And for the raw numbers technical comparison: http://www.bobgolds.com/AbsorptionCoefficients.htm

Probably. Will it be enough that you feel like the situation is solved? It's hard to predict now much it will help without knowing more about the room in a scientific way. If you want to know how much more trapping will help, you'd need to do detailed measurements, and then some math.

Another solution is to consider moving the sub to where it interacts with the room better -- but physics being what they are, that's not likely to be a full solution (single sub, long waves, small room = limited options).

Other ideas:

1. Buy a second sub (or third or even fourth). This evens out the bass response in the room when positioned correctly.

2. I'm not familiar with ARC -- does it correct for a multi-seat area, or for one position? If the latter, you may consider a device like Audyssey, that strives to correct for a multi-seat area instead of for a single location. You don't need to get rid of your current gear to do that. Audyssey via SVS makes an outboard sub EQ system that you can place in line with your current setup.

Foam is much less efficient than either fiberglas or rockwool.

See www.realtraps.com for comparisons or http://forum.studiotips.com/index.ph...4d625053ee43f6 for lots of data.

thanks for the reply. i had audyssey xt (denon 4310 avr), then got an svs as-eq1 and finally sold them and settled on ARC. ARC does do multi-position measurements just like audyssey and i find it better (atleast in my room with my gear) than audyssey xt and subeq. im already thinking about adding more subs, but since i can only add them to the front soundstage (limited placement), i know there is only so much i can do. that is why im wondering if bass traps will help me.

It's difficult to have too many corner bass traps.

+1

The problem with most foam bass traps is they're not large enough to work very well.

--Ethan

okay, then if that is the case, would i mess up any sonics if i have it only on one side of the room? i only have the room to do it on one side of the front wall but could also do the ceiling.

and as an alternative to the superchunk method, could i simply put a 2" thick piece of 0c703 on an angle in the corners or must it be be totally full to the corner?

Put them wherever you can. Floor/wall counts as a corner, too.


Yes, though filled are more effective. Some comparative testing here. Do what you can and you will be ahead of the majority.

In a room with seating up against the rear wall, is making the whole back wall absorbing the best way to go about it?

Well, for a few reasons seating against a wall is not recommended, but if that's what you need to do, then FOUR INCHES of OC 703 (or equivalent) should be placed on the wall behind the seating.

Jeff

Thanks for the reply. I know it's not ideal. It's the only way to have a second row with out the viewing distances causing motion sickness though. The only other way is going smaller with the screen. Would moving the back row off the wall like 4 inches be beneficial or does small increments like that not even make a difference?

I'd go with a smaller screen. "Motion sickness" tells me it's too close if you don't move it back. So why not make is smaller rather than move it back? It's all about the angle of view, not the absolute size, anyway. "Motion sickness" tells me the angle of view is too large.

I think you'd need a few FEET to minimize the problems of being too close to a wall. From your description, you're probably limited to a 4" spacing to allow for the absorption. Unless you do away with the second row, or decrease screen size.

Question for ya ... you mean viewing distances being a problem if the second row pushes the first row too close, right?

Jeff

Well the theater is still in it's beginning stages so I'm not sure if the screen would be too big yet.


I'd rather get rid of the second row than go with a smaller screen . And yeah, sorry about not clarifying, that's exactly what I meant.

Make sure to consider alternative "equivalent" insulation options if cost is the big concern - for example, I checked locally, the best I can do for OC 703 2" is $1.18/sf; I can get Roxul AFB 3" for $0.71. Using alternative materials, you might be able to build SuperChunks for the cost of the "span the corner" method. For spanning the corner, you'd want at least 4" (or so I've read).

Sharing the dimensions of the room -- screen size, and distance to first row and second row, especially -- will help us recommend possible solutions.

But here is the solution I came up with: I said "The second row is for non critical viewing, listening and for other people" so I'll make it decent, but never sit there. Works well, and that second row is still better than what most of my guests are used to.

In my room, too, it was either a second row too close to the wall, or no second row at all.

You hit the nail on the head. My theater is looking like 11' x 16.5' with a false wall AT screen making the length 15'. Here's the catch though, after sheetrock and carpet the ceiling height is going to be 6'1". Those are as close dimensions as I can get since framing hasn't begun yet. I'll attach pictures of it too. The seating isn't in the right position because I just threw them in there to see how the look would be. Same goes for the paneling.

Also, the left corner (facing the screen) behind the screen will have a corner bass trap. Any ideas on how to treat the nook in the front right corner?


EDIT: That's a 100" 16:9 screen I put in the drawing with extensions on the left and right for 2.35:1 if I want to go with CIH.

That's a tight fit. My room is approximately 12 by 17 by 7ft tall, and two rows feels on the edge of crowded, and definitely left no room for recliners in row 2. With your height, row 2 may feel very close to the ceiling.

I started with a 10ft wide 2.35:1 screen which was on the edge of too big for the first row. Due to wanting speakers in the room of a certain height and location and type, I have reduced the screen a bit and it still engulfs well, especially in the front row.

So I think you can make that room work but there will be a few tradeoffs.

I'll let others comment on your other questions.

But here's the big question: how critical is row 2? Occasional overflow or always in use because of how many people are typically watching?

By the way, if you haven't already, i'd start a build thread in the construction area since we are getting way off topic for this bread and I think you'll get more construction conversations there.

Howdy folks...lots of info here that it is quite overwhelming. I am a relative noob to construction and accoustics. I am building a dedicated HT in the basement (16'x9'x8').

I have an SVS 12" sub and a basic 5.1 setup with mid level Onkyo AVR. The room will be in the corner of the basement (under my kitchen and laundry room) with the walls along the front and side. Two walls (right and rear) will be standard 2x4 framed.

I was going to go berber carpet, standard drywall and drop ceiling. I don't have an unlimited budget but any minor suggestions to help trap bass or sound in the room? Right now, the outer walls are framed and that is about it.

Looking for basic thoughts around: Ceiling tile selection, anything to add behind the drywall?, etc.

THANKS in advance for any tips. I have been looking around the forums and it is hard to come to a consensus for some easy basic do's and don'ts.

PS. If this thread is off topic or better suited for another area, I can delete and repost elsewhere.

Nathan,

What is your eyeball to screen viewing distance for your front row?

I am also considering a 10ft wide 2.35 screen for my 12 ft wide room with a single row viewing distance of 11.5 to 12 feet!

I could also maybe go down to a 9 ft wide screen if necessary!

Your overall impressions please!


...Glenn

I'm not Nathan, but I have a 10 foot wide screen. 2.35 movies work for me from 10' back (1x sw!) but 16:9 is a little overwhelming from there. So I view those from the second row at 16' back.

Neighbors prefer the front row for 2.35 movies.

Agreed. 1x can work for 235 material. Too big for 16:9. But we are cluttering this topic with non acoustics. So i'll stay quiet going forward.

If one can only "straddle" the bottom half (2' x 4') of the corners (Floor to half way to ceiling) of the room with a 4" bass trap does the top of the trap have to be sealed? The bottom will be due to it touching the floor.

What would be an alternative to bass trapping if one cannot do a full corner (Floor to ceiling).

Lastly, since subwoofers are usually located on the floor, does bass collect evenly in the lower corners of a room as the upper corners?

Thanks

Bass doesn't "collect" anywhere. It doesn't seek out corners to go hide in. Bass traps don't "trap" anything. Bass "traps" are absorbers like any other absorber except bigger do deal with the wave lengths of the lower frequencies (at 80Hz the wave length is 14'). Bass absorbers can be installed anywhere you have the depth. Very few bass "traps" or corner "traps" (ever trap and catch a corner?) have much effect below 100 Hz...or at least their performance drops off rapidly below 100 Hz. For low frequencies, diaphragmatic type absorbers work best when near wall boundaries. For example a velocity type (diaphramatic are pressure type absorbers), you'd need a depth ranging from 1.5 to 3' for 80 Hz when mounted on a wall.

No.

What are my options for adhering unfaced rigid fiberglass panels to the wall behind my screen? I've seen rotofast (too pricey), spray adhesive (may try that), what else have you guys had success with?

This thread is focused on the use of materials within the room to treat frequency response and reverberation. From the question above, it sounds like you may be thinking more about isolation - controlling the amount of sound in the room from being heard outside, and vice versa. For the latter, try posting in the Green Glue thread, or create your own build thread to get advice specific to your build (on any topic).

(then again maybe I misinterpreted your question?)

Behind the screen you can use a collared nail. Usually the collars are orange and you'll need to blast each of 'em with some black spray paint.