Acoustic treatment


I want to build my own bass traps and was wondering if there are any other alternatives to fiberglass and rokwool. Foam is not a consideration as I don't believe it has the necessary qualities for absorption. I have heard of cotton batting, does anyone have experience with this material. The idea of fiberglass makes me itch just thinking about it, but I'm resigned to using it or rokwool if that's all I have.  Please make suggestions and let me know your experiences.

Thanks
Mike
zardozmike
mijostyn:
" Tim, I think you should find a job as a used car salesman, excuse me salesperson.
Actually summed bass below 100 Hz is an advantage in most acoustic situations you would have in the typical home."

Hello mijostyn,

     No thanks, I enjoy being semi-retired and performing only the occasional brain surgery.
     All 4 of the subs in my system are run as mono and I have no current issues with summed bass below 100 Hz, although those wanting or expecting stereo deep bass from their systems will likely be disappointed.

  mijostyn:
" Back to Tim, The term "room control" is a misnomer. You are not controlling the room. You are controlling the speaker to correct response abnormalities of the speaker/room system, to make both sides have exactly the same response and correct timing so that the sound from each driver hits the listening position at exactly the same time."

     I don't recall ever using the term "room control".  However, I do understand the 4-sub DBA concept works so well due to creating numerous well dispersed additional bass room modes (bass peaks and dips) at various frequencies in the room.  And I understand the psycho acoustics identified principle of our brains processing these numerous varied bass room modes by averaging them out which results in the perception of the bass as accurate, detailed, fast, smooth and natural. But I agree with you that this is properly described as controlling the speakers to correct abnormalities of the speaker/room system, not as "room control".
     The time domain aspect, or the timing of bass sound waves reaching the listening position, is of much less importance for deep bass frequencies than it is for mid-range and treble frequencies.   We're actually not very sensitive to arrival time in the bass region.  It's been proven that we don't even hear a deep bass frequency until the full duty cycle of the frequency sound wave has been released into the room.  In other words, we cannot detect the presence of bass from less than one full wavelength.  We also need to hear multiple full wavelengths before we can detect pitch.   A 56 foot 20 Hz sound wave released into a normal sized room means it is going to bounce or reflect at least once before the entire duty cycle is detected and be able to be heard at the listening position.  We also need to detect multiple cycles at the listening position to determine pitch. 
      This implies that relatively small timing differences - 'small' relative to the wavelengths in the bass region - are not going to make an audible difference in and of themselves.
     I think you're stating there's a requirement for the "correct timing so that the sound from each driver hits the listening position at exactly the same time"  seems unreasonable and unlikely given the reality of our bass sound wave perception capabilities.  

Tim
jon_5912:
"The reason I ask about adding smaller subs to a big one is that I, like a lot of people I'm sure, already have one big expensive sub. I would never buy three more like it. I measured the response with the Behringer ultracurve and measurement mic, and equalized out the worst of the problems. I'm not unhappy with it how it is but if I could add a few smaller, cheaper subs and get a dramatic improvement I might consider it."  

Hello jon_5912,
     I think you may have missed my response to your question earlier in this thread. Here it is again:

Hello jon,
    Very good question. I've never tried this myself but I don't believe there's any reason this wouldn't provide accurate, detailed, smooth and natural bass with deep bass extension down to 20 Hz. I suspect, however, having only one sub extending down to 20 Hz might limit the power and impact heard and felt at that deep bass frequency. But It may be possible to compensate by having the volume set higher on the sub that goes to 20 Hz or you could always use two and still be saving money, just a bit less.  
    You should also probably go look and hear some subs, 30 Hz sounds and feels quite deep and may be sufficient for some.

Tim

Geoffkait I would like to understand the bowl resonator you mentioned. I don’t mean to derail this discussion but if you could post a link to what you refer to I would investigate further. Are they examples I can research? Thanks-
mike. 
You can research the original Franck Tchang Acoustic Resonators. Here is one of the excellent reviews in 6 Moons,

https://6moons.com/audioreviews/francktchang/resonators_2.html