[Jay S]

I did a simulated RTA analysis of my room using this calculator...

http://www.saecollege.de/reference_material/pages/Reverberation%20Time%20Calculator.htm

... and found that I had a bit too much reverb in the 125 Hz and 250 Hz.  I have noticed some boominess on occasion, though it is much less when there are more people in the listening area (people are great bass absorbers!).

Does anyone have any creative ideas for absorbing <250 Hz frequencies but which will blend in nicely into a small living room?  Large bass traps will not fit in, unfortunately!  

You can see pictures of my room here:

http://www.audiocircle.com/index.php?action=gallery;area=browse;album=6

Thanks!

[audiojerry]

I don't know if I have any solutions, but life appears to be good in HK Nice abode, Jay.

I think the windows with blinds might be a problem. Would it be acceptable to install heavy fabric drapery that you can close when listening, but left open when not?  Also, since you can't really move the sofa closer, can you install a larger diffuser/absorber on the wall behind it?

[Brad V]

I did a simulated RTA analysis of my room using this calculator...

http://www.saecollege.de/reference_material/pages/Reverberation%20Time%20Calculator.htm

... and found that I had a bit too much reverb in the 125 Hz and 250 Hz.  I have noticed some boominess on occasion, though it is much less when there are more people in the listening area (people are great bass absorbers!).

Does anyone have any creative ideas for absorbing <250 Hz frequencies but which will blend in nicely into a  ...

Hi Jay,

How about Owens Corning 705 panels. You could put 2 to 4 of them together. From what I understand, if you take 2 of them, which equal 4 inches in depth and place them at least 4 inches from the wall, they have the ability to absorb down to 100hz or a little less. I just finished making some of these panels and put them on stands, so that I can move them around for best results or out of the room, if my wife wants them out of the room for company.

I believe Jon Risch talks about the absorption on his website. These panels are 2 feet x 4 feet and are 2 inches thick.

Hope that helps,

Brad

[audiojerry]

Though this may not help your room node, it might improve imaging and soundstage if you made a cover of thick fabric to place over your TV. I'll bet your large tv screen is reflecting upper midrange and higher frequencies from the speakers that could be causing some easily discernable smearing.

[Marbles]

Jay,

Do a search for "Helmholtz Resonator"  These can be tuned to "attenuate" specific frequencies.

I have seen pics of them only.  The one I saw was made from 3 PVC pipes standing vertically on a 2" x 4" board.  The pvc was covered or painted.  This is a portable device, so it can go into a closet when Shy's friends are over, and it can come out when yours are....

[Brad V]

Though this may not help your room node, it might improve imaging and soundstage if you made a cover of thick fabric to place over your TV. I'll bet your large tv screen is reflecting upper midrange and higher frequencies from the speakers that could be causing some easily discernable smearing.

Hi Jerry,

That's taken care of. I have a big piece of foam, that is put over my TV, when doing serious listening. I also finished a panel that goes over the coffee table.

Thanks for the suggestion,

Brad

[Brad V]

Jay,

Do a search for "Helmholtz Resonator"  These can be tuned to "attenuate" specific frequencies.

I have seen pics of them only.  The one I saw was made from 3 PVC pipes standing vertically on a 2" x 4" board.  The pvc was covered or painted.  This is a portable device, so it can go into a closet when Shy's friends are over, and it can come out when yours are....

Hi Marbles.

I believe I saw a DIY of that on Jon Risch's site.

There is also a DIY on the Shakti Hallographs.

Have a great day,

Brad

[Pez]

Jay,
   It sounds like your problem isn't the 250 hz range it is the 125.  The 250 hz range mode you are getting is most likely because of the 125 hz hump.  The reason is 125 is the fundemental of 250, as a matter of fact I would not be suprised if the real problem is ~60 hz (62.5 hz by my calculations).  If you tame your 60 hz hump (which is probably a lot easier to tame than 125 or 250)  and your 125 hz hump the 250 should disappear.

[Jay S]

Hi guys,

Thanks for the inputs.  

I do think the big TV screen hurts the sound.  When I am listening seriously (and certainly when the HAM is over!) I put a blanket over it, which really does help imaging, soundstaging and treble smoothness.  My longer term plan is to get a 42" plasma TV when prices fall below $2k (a good Samsung is now $2.8k), so that at least the screen will be 14"-18" further behind the speakers.  

I really wish my room were deeper.  Unfortunately, there's only 10.5' from front wall to back wall.  I had read the Jon Risch DIY articles but decided that I could not really afford to space thick acoustic panels several inches from the wall.  The compromise there was that absorption would fall off below around 400 Hz, which has been confirmed by the simulated RTA.... I don't think the Owens Corning panels will quite work right now as they may overdamp the higher frequencies.  What I need are narrow band absorbers.  

Jason/Pez makes a good point re fundamental frequencies.  The simulated RTA shows there is slightly more reverb at 250 Hz than 125 Hz, with some extra reinforcement perhaps coming from lower frequency fundamentals.  

A Helmholtz Resonator may work pretty well.  There may be ways to disguise 3 tubes so that they look like a nice decorative divider.... what I need to do is get a hold of a real spectrum analyzer so that I can figure out exactly which frequencies need to be absorbed.  Or maybe I'll read the articles, buy some pipes and putz around!  

I have been wondering of the impact my side window (the width of the entire wall and about 6' high) was having.  Large expanses of glass are not good.  I do have wood blinds which I keep drawn at a 45-60 degree angle to mostly block the glass.  I have been considering putting some small felt dots on the glass - not really visible to the eye but if I recall they may have a similar effect as Marigo dots.  

What would be great is to find something decorative that would absorb low bass.  I have moved my coffee table slightly to the side and now have large overstuffed pillows in the middle of the carpet between my couch and speakers.  I recall Klaus is big on plants... not sure if they do anything to low bass.  I may be able to hide a couple of small bass traps.  May need to buy them as DIY is kind of a pain in HK.  

Finally, Jerry, thanks for the kind words on my abode.  I enjoy having friends over.  I'm glad that the HAM has been over a few times.  It would be great if some of you guys from the U.S. could drop by sometime.  As inducement, I'll take a picture of my bar and wine fridge and post it in my gallery!  

Do keep the great ideas coming.

Cheers!  

- Jay

[Sedona Sky Sound]

Hello Jay,
I must admit that when I lived in Taiwan I never did get my room totally correct. You may also find that trying to locate the things necessary to build a tube trap (or anything else for that matter) is significantly more difficult. I drove my girlfriend (now my wife) absolutely nuts trying to find things that I would normally just go to Home Depot to get here in the US   .

As far as I can tell, what Marbles is talking about is actually not a true Helmholtz Resonator even though that is what most people on the forums call it. Most of the Room Lens type devices actually seem to use canceling reflective waves instead of low pressure compression. Here is one of my favorite articles talking about canceling waves:

http://web.archive.org/web/20000816145216/www.headphone.com/EditorialHeadroom/RoomTubes.asp    

Based upon what you indicated in this post and in DRPHOTO's, you may be able to use something like an ASC Quarter-Round Tube Trap but ask for a slightly more reflective inner material. From what I could tell from your photos, something like this would blend in nicely where the ceiling meets the walls. This is also an area where bass is heaviest so it would work well. Being in Hong Kong, I am sure you can find someone to make one up for you at an attractive price   .

Pez, what way are you using to kill a 60Hz hump? I always found that the 60Hz-80Hz range was the hardest to control for me (a Tube Trap would have to be too big and it is somewhat hard to tune a Helmholtz Resonator in this range).

Julian
www.sedonaskysound.com