Looking for help on room acoustics

[artto]

BASS TRAPS.

My apologies to everyone who has already posted on this subject and got it wrong, or partly wrong.

Bass Trap. It's not really a bass "trap". It's actually a bass "augmentor".

Bass traps can be made any size as needed to "trap" the required frequencies. In other words, they are NOT effective ONLY down to "175Hz". The Krannert Center for the Performing Arts Great Hall at Uof I in Urbana, IL has a ceiling area above the concert hall ~ a bass trap ~ six stories tall.

What a bass "trap" does, if large enough, is absorb all frequencies fairly equally. What does this do? It stops reflected low frequency waves from returning and mixing with the next wave produced by the speaker or reflected by the room. This essentially has the effect of "cancelling the cancellations" of certain low frequencies, which are determined by the room geometry.

You can affect lower and lower frequencies by adding longer and/or deeper sections of bass traps. For instance, a 16' length of Auralex LENRD (8 two foot sections) along the wall/ceiling intersection will be effective to a lower cut-off frequency than one 2' section in that same location.

Once the room becomes large enough the modes become so numerous and close at all frequencies it doesn't matter anymore.

[Chris A]

My apologies to everyone who has already posted on this subject

Apologies accepted...

http://www.ethanwiner.com/acoustics.html#fiberglass%20traps

http://www.readyacoustics.com/index.php?main_page=index&cPath=26_7_5

Ethan Winer: "When you add bass trapping, you are making the walls
less reflective at low frequencies, so sound that hits a wall or ceiling will be absorbed
instead of reflected. The net result is exactly the same as if the wall was not there at
all - or as if the wall was very far away - whatever does come back is greatly attenuated
due to distance and, therefore, not loud enough to cause as much cancellation.

FIBERGLASS BASS
TRAPS - There are a number of ways to create a bass trap. The simplest and
least expensive is to install a large amount of thick rigid fiberglass, spacing it well
away from the wall or ceiling. As noted earlier, 705-FRK that is four inches thick and
spaced 16 inches away from the wall can be quite effective to frequencies below 125 Hz."

Note that I was using my bass traps as temporary barriers, not as bass traps. The problem statement was related to a lack of bass at the listening position - I think that it would be wise to go to another (new thread) to argue bass trapping.

Respectfully,

Chris

[sootshe]

Have you tried the pair in the corners 90 degrees to the left, to give fuller corners to both? Intuitively, I prefer the speakers facing, overall, from the main room toward the offshoots, and would be concerned about the right one being next to the hallway entrance and facing in the opposite direction. IMO, you should try to face the pair somewhat in that direction, not 180 degrees away from it. My suggested location still faces the dining room somewhat, and I suspect the Las are non-directional enough for that position not to be that much of a problem.

My $0.02, of course, & YMMV.

Larry

Larry,

Yes, tried them in that location & the result was identical.....still greatly reduced bass at the listening position. The best result I've had so far is with Chris's idea of a partial wall behind the listening position to effectively split the room up.

Thanks to all for your helpful comments & the interesting info on the bass traps....much appreciated.

[bliss53]

I had a room issue as well and made some traps and panels. These helped but the big video screen was the big culprit. I moved my two channel gear to another room and I am much happier. See the pics of the panels and the bass tubes.

[bliss53]

Trim painted black and hanging. The tubes have heresey rear channels sitting on them.

[Just_Strummin]

You might also want to use a parametric EQ with built in software and a mic to help you calibrate your room's acoustics after you get the room treatments set up.

You'll want to use a Test CD with 1/2 tone increments to get the room dialed in. Or use an amp like the Velodyne SC-1250 that will do it in about 5 minutes. It has its shortcomings though b/c it doesn't go below 20Hz without a steep rolloff.

[Mr. RF62]

What J.S. said.

[colterphoto1]

ok, cut it out you two [:^)][8-)]

[sootshe]

You might also want to use a parametric EQ with built in software and a mic to help you calibrate your room's acoustics after you get the room treatments set up.

You'll want to use a Test CD with 1/2 tone increments to get the room dialed in. Or use an amp like the Velodyne SC-1250 that will do it in about 5 minutes. It has its shortcomings though b/c it doesn't go below 20Hz without a steep rolloff.

Yes, good idea.

I'm actually doing some more mods on my LS. I have a pair of Tractrix horns & Universal crossovers coming from ALK. Will listen to this first & then decide if I will proceed with the bass reflex cabinet underneath the LS to extend the bottom end. Pic attached.

[billbrammer]

Hi John, not sure where you landed on this. I just joined the forum to get help with where to find some Klipsch presence speakers to go with my KSB 3.1, etc, etc....

I have spent a lot of time on acoustics for my room because is is 15 X15 X 7.5 feet. A bad dimension, which creates a large bass standing wave. I discovered that bass traping is a huge deal and will clear up many other parts of the music if you get it done. I see you are in Australia, so not sure who the suppliers would be there, but I am building a giant bass trap and buying some corner bass traps from suppliers here in the US. NOt sure what the policy is on sharing those suppliers, so won't put it in here. If you search for "bass trap" you'll find tons of stuff. Don't give up on the room. You can do a lot with acoustic treatment.

[sootshe]

Hi John, not sure where you landed on this. I just joined the forum to get help with where to find some Klipsch presence speakers to go with my KSB 3.1, etc, etc....

I have spent a lot of time on acoustics for my room because is is 15 X15 X 7.5 feet. A bad dimension, which creates a large bass standing wave. I discovered that bass traping is a huge deal and will clear up many other parts of the music if you get it done. I see you are in Australia, so not sure who the suppliers would be there, but I am building a giant bass trap and buying some corner bass traps from suppliers here in the US. NOt sure what the policy is on sharing those suppliers, so won't put it in here. If you search for "bass trap" you'll find tons of stuff. Don't give up on the room. You can do a lot with acoustic treatment.

Bill,

Thanks for the advice.....since I put the bass reflex cabinet underneath my LS the problem has gone. Bass is now fully extended & sounds awesome from the listening position...can't quite figure that one out. Have also added the ALK crossovers, which made a huge difference over the Crites A4500's.

Still to add the ALK Trachorns.