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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Reply to your specific questions posted by Jon Risch on October 16, 2009 at 17:43:29:
Hi Jon,
A saw a link (see below) provided on a post by mkuller on a different Tweaker’s Asylum thread where J. Peter Moncrieff states:
“The second harmonics of the room's fundamental bass resonances might need further quelling, even after the fundamental has been controlled to your satisfaction (whatever degree that happens to be). There are several reasons for this. The harmonics are in the upper bass region, which is far more audible to human hearing than lower bass, thus making even a slight remaining resonant boom more objectionable. Also, most music and most loudspeakers put out far more energy in the upper bass than the lower bass, thus triggering even a slight remaining upper bass room resonance mode more frequently and more severely.â€
My (very recent and limited) experience in building flat panel traps using 4†thick 24†wide OC 705 leads me to believe that these acoustical treatments have a very positive effect in this way. I did extensive measurements before and after installing these panels, and, while there was no measureable impact to the frequency response in the sub-80hz region, I do hear drastic improvements in mid-bass and midrange linearity, detail, imaging, and overall musicality (perhaps the panels are indeed having a positive impact by shortening the decay time of the bass frequencies). Simply said, the sound is much less thick and ponderous.
Moncrieff goes on to assert that it is the rear (behind the listener) wall-to-wall and wall-to-ceiling intersections that should be treated first by bass traps in order to achieve effective low-bass attenuation. Out of curiosity, tonight I moved my flat panels from the front to the rear corners. Very disappointing. The gains that were achieved with the panels in the front corners were lost. This further leads me to believe that my panels are not significantly affecting the low-bass, but are doing a good bit in the mid-bass and midrange frequencies (in the front corners). I plan to continue to use these in the front corners as they do have a good effect and I have too much time and money invested in them to scrap them. Perhaps I will try to seal them as you recommend to see if I can improve their impact on lower bass frequencies, at least the third harmonic (in my room) of 70 hz.
So, I am now ready to accept that a different solution (tube traps) is indeed needed in the rear corners and horizontally at the rear wall-ceiling intersection to (hopefully) impact the first low-bass fundamental in my room (14.5’ X 23.5' X 10’, so the fundamental is 550/23.5 = 23.4 hz) and, more likely, the second and third harmonics (47 hz and 70 hz). I am thinking of building seven 48†tall 16†diameter traps (stacking two in each rear corner and placing three horizontally between them at the ceiling). I have seen your instructions on building DIY tube traps (not the quick and dirties) and was wondering about the difference in effectiveness when using OC semi-rigid fiberglass panels like ASC uses vs. the batting type you recommend. A while back, a helpful AA member sent me full instructions on how he built tube traps using the semi-rigid fiberglass, but Bill Gates deleted it for me. I do know that OC offers such a product. Do you know what the OC model number is for this type of fiberglass (can be bent uniformly around the chicken wire structure)? How does its performance compare to the batting type? What type of improvement can I expect with the seven 16†tube traps configured as specified above?
For those like me that already have panel-type treatments, perhaps my idea to use them in the corners behind the speakers and real tube-traps in the rear room corners/ceiling is a good solution. I think rather than argue the merits/superiority of each approach, it might be more beneficial for the users just to accept what each does well and work from there.
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Follow Ups
- RE: Reply to your specific questions - crossram2x4@aol.com 00:50:42 10/20/09 (0)
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