AVS Forum banner
Status
Not open for further replies.
1 - 9 of 9 Posts

·
Registered
Joined
·
438 Posts
Discussion Starter · #1 ·
I'm setting up a theater in a room that's 31' 5 1/2" x 16' 1/2" x 9' 1/2". Obviously, the length/width is very close to 2:1. I plan on using the room for both theater and music.


My adviser/dealer is telling me that's it's an acoustic nightmare (I know 2:1 is supposed to be bad). Supposedly I have a "very high amount of room modes". Don't really know what that means...


While it's possible for me to move walls, I'd certainly like to avoid it.


Any advice? How bad is this issue? Is there anything else short of moving wall (e.g., some acoustical treatment or putting some large items (e.g., popcorn stand, DVD racks) near the back to start the reflections early, etc.) that would help?


Any guidance would be appreciated. Thanks.
 

·
Registered
Joined
·
5,896 Posts
You could address the problem with numerous membrane/panel bass absorption devices.
 

·
Registered
Joined
·
438 Posts
Discussion Starter · #3 ·
Quote:
Originally posted by Bigus
You could address the problem with numerous membrane/panel bass absorption devices.
Thanks.


Anything more specific?


What's a good company to work with on this?
 

·
Registered
Joined
·
337 Posts
If you think that's bad.... my listening room has actually been built to a Japanese ration of lxwxh of 4x2x1....

And in reality I don't have a problem there at all.

With a small number of room treatments I am sure you will have no problem.

I would advise, and this is difficult without listening IN your room, a dead end live end approach with some bass traps in the corners.

Even the traps could wait till you hear the DELE effects.

If you can get some of that acoustic soundproofing material in Australia called, I think, Bumph (!!!!), which you can use as lining for curtains, then that would be very good.

Or HEAVY velvet lined curtains. It depends how much money you want to spend.

If you just want to try something, then as an experiment, see if you can borrow a BIG sheet of foam at least 100mm thick and drape it with a old blanket.

Prop it against the wall behind your seating and give it a listen.. It will look terrible but may give you some clues as to the effect of doing it properly.

SOme furniture makers and similar people use large sheets of foam to wrap things for delivery. As you only really want it for a few hours max, you may be able to borrow a sheet from someone....

If the room is "hard" with a lot ofreflections, then first reflection positions will also do well with absorbtion or defraction. Its worth trying the floor if its a hard surface as well at first points. Big old floor cuchions can work surprisingly well. Not as well as the real thing of course, but good enough for a test.

Jon Risch has some "quick and dirty" designs for bass traps and a lot, and I mean a lot, of information at his site.

I can't remember the address, but go to AudioAsylum and click on FAQs and use the links from there.

Its ok to spend money on this, but better to work out an approach first, which can be tricky.

I like to try out as many cheap tweaks first to make a reasonable guess as to what will work properly.

This doesn't have to cost a fortune.
 

·
Registered
Joined
·
711 Posts
It's not as bad as your dealer makes it out to be. Your room doesn't have any more modes (resonant frequencies) than any other rectangular room. The difference is that rooms that have the same dimensions in more than one direction, or have dimensions that are multiples of each other, will have more modes that overlap. Not just the primary modes but really the first through fourth order modes count.


The real world is never as bad as the calculations may imply. Real walls are not perfectly parallel at all points, nor are they perfectly rigid. The "flex" in the walls, ceilings and floors will help to absorb and smooth out some of resonances. The problem is that this is not very predictable. That's why rigid rooms with proper treatment work so well.


Your room dimensions really don't have much effect on early reflections and the temporal distortion they cause. Room modes really effect the low frequencies. Treatments focus on either broadband absorbtion, typically in the form of bass traps located in the corners or along the walls, or Helmholtz resonantors, which are more tuned absorbers. They can take the form of panel type absorbers, and box or tube resonantors.


Bottom line: Don't despair, the sound you get in your theater is much more dependant on how you build and treat it than the dimensions.
 

·
Registered
Joined
·
1,028 Posts
I agree with everything above.


If you want specific professional consultation, try Auralex acoustics or Echobusters. I think they both have consulting services where you fax them a layout of your room and they tell you what products you need to make it work.


I used to have a "room mode" calculator link where you put in the dimensions of your room and out come the room modes. I think there is something somewhere on Stereophile's website about this. If I get time to look and find it I'll post the link.


Be careful with too many room treatments. Dead rooms sound horrible. And if you get too many thin treatments with high-frequency absorption you will skew the tonal balance of your room.
 

·
Registered
Joined
·
438 Posts
Discussion Starter · #7 ·
Quote:
Originally posted by Bill Lummus
I agree with everything above.


If you want specific professional consultation, try Auralex acoustics or Echobusters. I think they both have consulting services where you fax them a layout of your room and they tell you what products you need to make it work.


I used to have a "room mode" calculator link where you put in the dimensions of your room and out come the room modes. I think there is something somewhere on Stereophile's website about this. If I get time to look and find it I'll post the link.


Be careful with too many room treatments. Dead rooms sound horrible. And if you get too many thin treatments with high-frequency absorption you will skew the tonal balance of your room.


Thanks, very helpful. What do you think of the full room treatments by Acoustic Innovations? They talk a lot about decreasing the loudness of the room. Would that qualify as too dead?
 

·
Registered
Joined
·
1,103 Posts
Grating,

Try putting in your carpet, furniture and other decorations first, then set up your system in, and see how the room sounds...apply treatment as needed afterwards. Predicting sound problems can be expensive and can leave you with a dead room that no one wants to spend time in for your money. If your system sounds great, no need for extra treatments. If you hear problems, get treatments for those specific areas.
 
1 - 9 of 9 Posts
Status
Not open for further replies.
Top