How to dampen room for specific frequency?

[Colin]

Hope someone sees this here, because here is where a room question belongs -

when Ray listed his room dampening equipment, (Owens Corning 700 series Fiberglass semi-rigid panels, wrapped in heavy black felt mounted on front wall of music room to deaden slap echo and midrange blare, Michael Green Echo Tunes, Corner Tunes and Room Tunes) I thought of my situation -

How do I dampen a bump in the 5 to6 kHz range of about 20 dB louder than a 1 kHz tone?

I live with big old Klipsch Cornwalls Is with horizontal K-51-V metal mid-range horn and K-77-M metal tweeter horns. They have the B-2 crossover w/o the p-trap fix. They are bright and can be harsh sounding. But even the little Infinity cones that I measured recently showed this same bump in the same area - so I am thinking that it may also be the room.

My seating spot is 99" feet away, in a carpeted 14 by 17 living room with popcorn painted 8 ceilings. It opens to the kitchen behind and to an enclosed porch with two sliding glass doors on the right wall (238 square feet).

If I re-arrange my office and move a tall and a short bookshelf to each side wall about half way down, will that do the trick?

There are two windows in the front wall, so I can watch a squirrel ruin my bird feeder, do they have to be covered - is this causing the bump?

------------------

Cornwalls & Klipsch subs; leather couch & feet up; lights out & tubes glowing!

This message has been edited by Colin on 10-26-2001 at 10:23 AM

[Klipschguy]

Colin,

A room tweak will likely be impractical/impossible. You're best bet will likely be an excellent quality, very low noise equalizer to make prudent, conservative room response adjustments. Equalizers can be quite useful, but are commonly overused, hence their bad rep. Andy

[fini]

It's the squirrel. Get rid of the squirrel.

fini

edit: Remember Ray's problem with "Furry Vibrating LaScalas?" Well, that may have been caused by squirrels, too. Possibly chipmunks.

This message has been edited by fini on 10-27-2001 at 10:00 AM

[Colin]

I do have an EQ button on my pre-amp, so that is an option, though I do not remember being so favorably impressed with the little Audio Control unit, and moving bookshelves is a lot cheaper -

I was hanging out with the squirrels today and decided to grease the wires for the bird feeder with vasoline - let's see if that improves the sound ...

------------------

Cornwalls & Klipsch subs; leather couch & feet up; lights out & tubes glowing!

[jdm56]

Colin,

I would not suspect the front walls' windows to be the culprit in the frequency range you mentioned. Maybe some contribution from ceiling or side walls combining

in phase with the direct sound to create the boost, but at that high up in the spectrum the problem should be confined to a very small area if that were the case. The wavelength at 5khz is just a little over 2.7 inches long, after all.

Just wondering: Have you ever checked the output of the sqwawker and tweeter horns in the nearfield? At least that might tell you if the problem is the speaker or the room. Or maybe a little of both, since the Infinity also exhibited the same characteristic to some extent.

------------------

JDMcCall

[soundog]

You will have to experiment with absorption and diffusion material. The point of first reflection usually benefits from a diffusion treatment. Drapes over windows can help minimize reflections off glass. I'd try hanging some quilts (or similar material)around the room to test out absorption treatments ... old egg cartons stapled (bottom up) to a thin piece of plywood or thick piece of cardboard can provide some make-shift diffusion. Also does redirecting (repositioning) the speakers make any difference? This could give you some hints about whats wrong. Of course all this stuff would have to be replaced with commercial (better looking) acoustical material. (Try parts express) However, none of it is usually acceptable in the living room from a decorator standpoint, in which case, you'll have to get creative with curtains, wall tapestries, etc. Bookcases with different size books often provide a good diffusion effect.

[WMcD]

My guess on this is that it a matter of hard flat surfaces overall. Maybe rearranging the book cases will help a bit.

PWK is a fan of cylindrical reflectors. There is a Dope from Hope on the subject.

I made up some reflectors for my office using foam core covered with large reproductions of Monet's.

I've not tried making any measurements.

If you're interested, I could get together some pictures.

One interesting experiment is to determine whether you've got a "slap echo." In a room with hard surfaces, walls, all facing each other this is a remarkable effect.

So, go to the middle of the room and clap your hands sharply as you can tolerate. Just once, more finger to palm than palm to palm. There is technical merit to this because you're creating a impulse, and listening to the impulse response.

In a bad case and large room, you'll hear a "b-o-o-i-n-n-g" type of echo. In a less bad case, you'll perceive a slight high pitched echo, which could be your bump in response. Move around the room and see what you hear.

The echo is a sign of problem which can be treated with reflectors or absortive drapes on the walls.

Gil

This message has been edited by William F. Gil McDermott on 10-29-2001 at 09:24 PM

[Colin]

I did try the slap test and there was a small echo when the room was empty, guess I didn't think it was much compared to the catherdal ceilings in the gret room where the horns where, I will try the bookshelves at the mid-point, but that means moving 1/2 of two rooms around ...

------------------

Cornwalls & Klipsch subs; leather couch & feet up; lights out & tubes glowing!