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Bad room for sound?

I'm starting to address the room acoustic issue with my listening room. I just measured my listening room and the dimensions of 237" by 157" are an almost exact 3:2 ratio. Is this ratio bad for sound? I would expect bass re-enforcement at some frequency.

How can I calculate that frequency? Am i correct that the lowest resonant frequency would be one full wave length across the room (which would also be one and a half full wave lengths down the length of the room)? I think that the speed of sound is about 1140 ft/sec. The room width is about 13 ft. So 1140 ft/sec divided by 13 ft/cycle equals about 88 Hz?

Also, I have hardwood floors that are old and are fairly "springy". I can feel bass vibrations in some parts of the floor but not in others. Should I add support under the floor?

Lastly, I have a Radio Shack SPL meter and I've ordered the first three Stereophile test CD's. Will I be able to measure any bass 'hump' with these tools?

I know that some of these topics have been covered in the past. Sorry if I'm repeating dead issues. Thanks all...
pmi_guy
foreverhifi
229 posts
 
Went to the San Francisco HE expo a few weeks back, and Rives Audio was in 6 or 7 rooms...BY FAR THE BEST SOUNDING SMALL ROOMS AT THE SHOW!!!!).
I would consure about checking out what they have to say.
Good luck
bobgates
535 posts
 
Your room dimensions sound like they would be great for a listening room; wish my room was that big. From what I hear it's a perfectly square room that doesn't sound that good.
rives
953 posts
 
Your dimensions aren't terrible. You are going to get a bump at 86 Hz, that is the 2 and 3rd axial modes (because of the 3:2 ratio). Depending on your ceiling height you could have some other areas of concern, but you accurately predicted the first problem (we use 1130 ft/sec--but that's at 1 atmosphere pressure so these measurements are relative). There are things you can do to deal with the issue from passive acoustical systems that can be designed (depending on how far you want to go) or you can deal with the bass hump problem utilizing a device such as our PARC.

The other resource I would point you to would be our room simulator. It allows you to plug in your room dimensions and move the speakers and listener around and see what it does to the peaks and nulls in the bass frequencies.
pmi_guy OP
72 posts
 
Thanks for the responses so far. My ceiling is vaulted from 9' to 11' and so I don't see any problem there. I guess my main concern is that I'm looking at upgrading to some speakers that have significant bass and I don't want to end up too heavy on the bass. Also, I like clean bass, without any "boominess".

I also heard that the Rives solution was very effective at the show. I've already set my speaker position according the the Rives website. The sound has opened up and the imaging has really improved. I'll run the room simulator next. Good work Rives!!!!
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