Vintage HiFi Audio Forum

The Home Theater Corner => Home Theater Audio => Topic started by: OldiesButGoodies on February 25, 2016, 09:11:12 PM

Title: Bass Trap Fail
Post by: OldiesButGoodies on February 25, 2016, 09:11:12 PM
So I have this room mode in the basement around 50-70hz that is giving me a headache.  I thought I would use an old sofa as a bass trap by filling it with cotton batting.  Fun exercise,  did not change things (green is corrected graph):

(https://farm2.staticflickr.com/1630/24897287519_5e047746d1_b.jpg) (https://flic.kr/p/DW67aV)2016-02-25_20-26-13_before_after (https://flic.kr/p/DW67aV) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

The batting exercise involved filling every known cavity of a sofa with extra batting to tame the errant standing waves.  I think  the wood frame around the sofa serving as perpendicular barriers to the waves kind of ruined the effect:

Before -

(https://farm2.staticflickr.com/1699/25147016232_57a8f5c3c1_z.jpg) (https://flic.kr/p/Eja2Po)IMG_1677-2.jpg (https://flic.kr/p/Eja2Po) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

After -

(https://farm2.staticflickr.com/1472/25265284035_1be221c3de_z.jpg) (https://flic.kr/p/EuBbHr)IMG_1678-2.jpg (https://flic.kr/p/EuBbHr) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

Bulging with batting:

(https://farm2.staticflickr.com/1492/24638488433_b665d306a5_z.jpg) (https://flic.kr/p/DxdGdH)IMG_1679-2.jpg (https://flic.kr/p/DxdGdH) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

Next - remove the crap load of batting I put inside the sofa and use it to build proper bass traps using wood frames and fabric. 

Here's the Dirac process (nine of these to get a full set of measurements) - fyi:

http://www.youtube.com/watch?v=VB8ClIR97Yk (http://www.youtube.com/watch?v=VB8ClIR97Yk)

Now on to listen to some music...

OBG
Title: Re: Bass Trap Fail
Post by: MacGeek on February 25, 2016, 09:32:39 PM
OBG-Are you working on the suck-outs or the humps?  Suck outs are tough; do you have any room to try repositioning the speakers?
Title: Re: Bass Trap Fail
Post by: scorpio333 on February 25, 2016, 09:50:55 PM
I forget where I read it, but it seems to work for me. Raised my sub up about 2' off the floor. I think it's 25% of the room height. It's free, can't hurt.
Title: Re: Bass Trap Fail
Post by: papabearjew on February 25, 2016, 10:29:53 PM
OBG. You need help!
Title: Re: Bass Trap Fail
Post by: F1nut on February 26, 2016, 01:36:43 AM
OBG. You need help!

 :laugh: :laugh: :laugh:
Title: Re: Bass Trap Fail
Post by: Kingman on February 26, 2016, 06:00:43 AM
OBG. You need help!
  :laugh: :laugh: :laugh: x2!
Title: Re: Bass Trap Fail
Post by: Jim Pittsburgh on February 26, 2016, 07:58:05 AM
I like the idea of raising the height. Elevated and slightly up angled the sub in the garage  a few inches and it smoothed out the response quite a bit. Might be time for a sub crawl party!  Symmetry is pretty but not always the best for sound.

Had a discussion once with someone from Velodyne back in the day. His analogy of placement, especially for low frequency sound, was to think of sound similar to a river with tributaries and your seating position as where the river empties into the ocean.... nothing is perpendicular or straight line without producing an area congested by eddies,  currents and sand bars.
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on February 26, 2016, 08:21:22 AM
Eh, the node I am fighting is with the main speakers set to large.  The graph you see is for the mains - the subs are off during that measurement, so raising the sub will not affect that - looking to improve the mains dip in the 50-70 hz area.   

Need to continue moving the speakers and adding treatments, IMO.  Or move to a room that does not have crappy audio proportions.
Title: Re: Bass Trap Fail
Post by: schwarcw on February 26, 2016, 08:57:23 AM
Get some different software that shows you the low frequency drop outs have disappeared.   :laugh:  O0  :(|)  >:D
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on February 26, 2016, 11:02:12 AM
great idea - thanks!   

  :-\

TGIF!
Title: Re: Bass Trap Fail
Post by: bmwr75 on February 26, 2016, 12:33:31 PM
Did you try leaning it up in the corner of the room?
Title: Re: Bass Trap Fail
Post by: geoffr on February 26, 2016, 05:06:04 PM
He'd have to duct tape the cushions to stay on.
Title: Re: Bass Trap Fail
Post by: papabearjew on February 26, 2016, 06:24:30 PM
You should try some Carver Amazing Loudspeakers Plats! Oh never mind, that ship has sailed...
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on February 26, 2016, 10:23:06 PM
the Plats had the same dip (no need to be a brain surgeon to predict that),   and did not perform at all setup for HT.  >:D
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on March 12, 2016, 08:06:43 PM
Things sounding clearer with these proper traps I slapped together today. Two 12" x 12"x 85"  towers with fiber fluff inside, placed in the corners of the back wall.  I called Tom to ask him what kind of fiberglass to use and he suggested I look for a formula in the web to tailor the design to the frequencial issues my basement was having.  Of course,  I went straight to Ace,  formula be damned,  and bought a few sticks of wood and some generic R12 fiberglass (and a shed load of paint stirring sticks - they gave those to me in recognition of me being a frequent visitor).  So now I am stoked about room treatment.  Maybe I should look for that formula after all.  Why 12" x 12"?  because that is what I could do with the spare plywood I had. 

(https://farm2.staticflickr.com/1607/25739905265_4b4e2ab6fb_b.jpg) (https://flic.kr/p/FdxK56)IMG_1216.jpg (https://flic.kr/p/FdxK56) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

(https://farm2.staticflickr.com/1480/25109478004_6409bde49e_b.jpg) (https://flic.kr/p/EfQD1y)IMG_1217.jpg (https://flic.kr/p/EfQD1y) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

(https://farm2.staticflickr.com/1566/25644837251_9dd3243e30_b.jpg) (https://flic.kr/p/F59uEp)IMG_1218.jpg (https://flic.kr/p/F59uEp) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

(https://farm2.staticflickr.com/1453/25618903392_353a4118b8_b.jpg) (https://flic.kr/p/F2RzqU)IMG_1221.jpg (https://flic.kr/p/F2RzqU) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

(https://farm2.staticflickr.com/1537/25739911655_d9f0ceb75d_b.jpg) (https://flic.kr/p/FdxLYg)IMG_1223.jpg (https://flic.kr/p/FdxLYg) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr

(https://farm2.staticflickr.com/1554/25439173510_09fa8b6954_b.jpg) (https://flic.kr/p/EKYpZQ)IMG_1225.jpg (https://flic.kr/p/EKYpZQ) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr
Title: Re: Bass Trap Fail
Post by: vstarkwell on March 12, 2016, 08:33:24 PM
Gotta love the passion Pepe, I hope they do the trick.
Title: Re: Bass Trap Fail
Post by: schwarcw on March 13, 2016, 01:36:28 PM
OBG, the material that you are using to absorb sound simply doesn't work.  These materials will:  http://www.gikacoustics.com/product-category/diy-acoustic-panel-bass-traps-supplies/ (http://www.gikacoustics.com/product-category/diy-acoustic-panel-bass-traps-supplies/)

Please read this link: http://www.gikacoustics.com/diy-acoustic-panel-frames/ (http://www.gikacoustics.com/diy-acoustic-panel-frames/)

They offer DIY materials and call tell you which Owens Corning material to buy.  They even can build you a finished product for a very reasonable cost, no "audiophile pricing"!  Or, guide you on how to do it yourself.  Send them a room sketch and they will offer potential solutions. 

They have a wealth of education materials and advice on their site.  GIK is the world leader in professional and residential room treatments.  I have bought their products and they are great people to work with.  Please contact them, you will thank me later.

Call me if you want to discuss.
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on March 13, 2016, 02:27:57 PM
'does not work at all' are strong words given my empirical observation Carl!  Things tightened up quit a bit  (but this room was so bad before that pretty much anything would have helped in the corners,  even a rolled up carpet).  Will confirm impact by running an FFT waterfall later today.  Part of the fun to this,  I suspect,  may be switching materials,  like tube rolling.   Both towers are now dressed up in dark brown acoustic fabric and have "service areas"  accessible through one side of each for future filling with other material.  Time to clean up the mess in the garage before wife kills me.  But first,  some fish beer.

(https://farm2.staticflickr.com/1696/25460748560_45a0cac88a_b.jpg) (https://flic.kr/p/EMSZvs)IMG_1227.jpg (https://flic.kr/p/EMSZvs) by Jose Sifontes (https://www.flickr.com/photos/jsifontes/), on Flickr
Title: Re: Bass Trap Fail
Post by: schwarcw on March 13, 2016, 08:36:38 PM
I agree OBG.  What I am saying is that material you are using is great for thermal insulation but it is not the material that is designed for sound insulation.  Roll, roll, roll materials!

Your traps look pretty good.  You could get some cloth to match the blue walls.  The GIK has a variety of colored cloth.

Have another fish on me!  ;)
Title: Re: Bass Trap Fail
Post by: bmwr75 on March 13, 2016, 09:42:50 PM
OBG,

What are the dimensions of this room?  The mains look much to close to the front wall to me.   Isn't 1/3 of the way into the room optimum (but never possible in all my practical experience)?

Can you put the Hsu sub on a side wall?

Scott
Title: Re: Bass Trap Fail
Post by: OldiesButGoodies on March 13, 2016, 11:29:15 PM
These speakers are a bit weird that way.   The get better closer to the wall,  though I have never tried them 1/3 out.  Maybe that is a 'later-this-week' experiment. 

I have had the sub on the side but I got better decay in the waterfall (faster) in that  position.  Still pending trying  the sub behind the listening area.

Room dimensions are roughly 24 x 27 with stairs and others door towards the back.

Thanks,

OBG

Title: Re: Bass Trap Fail
Post by: bmwr75 on March 14, 2016, 05:33:23 PM
A nearly square room is not optimal.
Title: Re: Bass Trap Fail
Post by: bmwr75 on March 14, 2016, 09:41:38 PM
You probably need some of these OBG.

http://www.shakti-innovations.com/hallograph.htm (http://www.shakti-innovations.com/hallograph.htm)

 :laugh: