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In Reply to: RE: Multiple, smaller tube traps...? posted by tvr2500m on June 11, 2007 at 15:43:39
Use of the steam pipe tubes is sub-optimal, see:
The problems with steam pipe insulation for bass traps:
http://www.AudioAsylum.com/audio/tweaks/messages/57035.html
http://www.AudioAsylum.com/audio/tweaks/messages/6425.html
AND
http://www.AudioAsylum.com/audio/tweaks/messages/13535.html
AND
http://www.AudioAsylum.com/audio/tweaks/messages/3771.html
You might as well go for the SUper Quick & Dirty traps, as in:
the original post where I reveal the latest Super Quick & Dirty easy bass traps recipe:
http://www.audioasylum.com/audio/tweaks/messages/15737.html
and petew's post where he goes into detail on what he did.
http://www.AudioAsylum.com/audio/general/messages/70817.html
Less costly than the steam pipe tubes, and more effective in most cases.
For a true pressure differential bass trap, ala the ASC type devices, and my original DIY bass trap (See: http://www.geocities.com/jonrisch/a1.htm),
the larger sizes absorb lower bass frequencies that smaller traps do not, but when we are talking about the sheer brute force of the SQ&D type, there is no direct correlation with size, as density comes into play, as does overall size.
If you get the steam pipe tubes, do not bother to stuff the centers, it will do next to nothing, instead, line the outside with hi-loft polyester bating, so they will at least absorb some mids and highs.
Jon Risch
Follow Ups:
Jon, very helpful. Thanks. These various solutions were exactly the ones I'd been looking at/considering. I hadn't seen the follow up regarding the pipe insulation traps. Lazy is good. Your wire traps would be nifty, but just grabbing a bunch of rolls of fiber glass is just silly easy. I would like to dress them up a bit - maybe a frame, maybe wrapping them some grill cloth, etc.
So, leave the plastic bags on the rolls of fiberglass? Wouldn't the bag cause reflection problems?
Thanks.
- SJ
If you intend to use the rolls of fiberglass strictly as bass traps, just dressing them up is all that is absolutel;y necessary, but I recommend a layer of the 3/4" thick high-loft polyester batting for an outer layer that is wrapped around the bags, this will then help with the upper mids (somewhat)and the highs. Use two layers of polyester batting for more absorption down into the midrange.
Jon Risch
Got it, Jon. Too easy. I was thinking about that - whether I want/need them to do more than just handle bass. I dunno. Wrapping some polyester batting around them would also be easy.
Any thoughts about non-corner bass traps, such as traps tuned for bass applied to walls or ceilings?
I was also reviewing the Owens Corning literature about the 700 Series rigid fiber glass products and saw listed a 707 material, described as for acoustic use. But the document didn't provide any detail about the product, and I haven't found any mention of applying this on the web.
My original game plan had been to apply traps in the corners primarily intended for bass absorbtion, and panels, made of something like Owens Corning 705, on the walls and ceilings for broader band absorbtion. I'm sure these panels work better at some frequencies than others. I suppose some broad band absorbtion in the corners could possibly be helpful. How much of which frequency band to absorb? I don't have equipment to measure all of this, I was just going to go by ear.
- SJ
For the wall panels, if you are going to go the semi-rigid panel route (OC 700 series),consider one of two things:
Either use two 2" 703 grade panels for extra thickness, or use a 3"-4" total thickness 705 wrapped on the outside with polyester batting.
The 705 density tends to reflect the HF's at any angle but head on. The absorption data typically published do not really show this, but I have made my own measurements in an anechoic chamber. The 703 panels are not nearly as bad, and while they can also benefit from a layer of polyester batting, the difference is not nearly as much as the 705 grade.
If you try to use one 1" thick panel, it just won't absorb enough lower frequencies, and will tend to make the room sound dull and boomy if too many panels are used to compensate.
Keeping a nice thick set of first relfection panels, and some corner or behind the speaker panels will do the job without overdamping the room.
BTW, unless you use WAY too many thin panels, or merely too many thick panels (which is very hard to do), it is hard to 'overtreat' a room acoustically. See my DIY Acoustics note near the end
( http://www.geocities.com/jonrisch/a1.htm )
I provide a quick list of the recomended treatments:
4 bass traps, one in each corner OR two in each front corner (depends on room and rest of treatment)
Wall Panels at the L & R 1st reflection point (mirror point)
Wall Panels behind each speaker on the front wall
Total of Wall Panels so far = 4 (Note that these are nominally a size of 30" by 48" by 4" min. depth), so two of the 24" by 48" would not be too much at each location)
and one wall panel each in the rear upper corners IF the bass traps are all up front. If you later decide that one (or more) bass trap in each corner works bestter, then these rear corner panels can be used elsewhere, such as the center of the rear and/or front walls (centered top to bottom, and side to side).
Diffusion usually works best on the center of the rear wall, BUT, you have to have a room large enough to do this properly.
The total amount of recommended acoustic treatment in that note WILL NOT overdamp a room, or be too much for 99% of systems. SOME systems are so dark and dull, that almost ANY acoustic treatment could remove too much of what little sparkle and life is left, and so, those cases can be a problem, but re-balancing the tonal balance of such a system after room treatment has been put in play will almost always end up with a HUGE overall improvement, because the IMAGING and SOUNDSTAGE are now more present and defined, and with less bass boom, more apparent bass (yes, ADDING bass absorption usually ends up providing more apparent, deeper and tighter bass), the increase in actual treble output from the system is now much more welcome.
Go for as much of the recommended treatments as you can, I think you will be amazed and pleased at the end results.
Jon Risch
Bass traps are placed in corners because they are the location in which all bass modes are present. You get more effect from a bass trap in a corner location than anywhere else in the room.
Say the fundamental standing wave for a room dimension is 20 Hz. That room axis will also support standing waves at 40, 60, 80, 100 Hz and so on at 20 Hz intervals. All of those modes will have peaks in the corner and the bass trap will work to reduce all of those peaks if placed there. The corners are the only places where all of those modes are present in the one spot. Yes, you can find peaks for each of those modes elsewhere along the walls, and also in the centre of the room, but only some of those modes will be present at any location where there is a peak, not all of them. They aren't all distributed around the room in the same way. You can treat every location where there is a peak along a wall, but you'll end up with traps at 4 or 5 or more locations along the wall as well as in the corners, and none of those traps outside the corners will be as effective as the traps in the corners.
If you want more bass absorption, go floor to ceiling in every corner and make the traps bigger in every corner. You'll get more effect for fewer traps by treating the 4 locations where every room mode peaks in the one spot rather than treating a multitude of peak locations elsewhere in the room.
David Aiken
David Aiken
Jon:
Just a quick thanks for the DIY recipe. I have now built 7/4ft tall 18" diameter traps.(ASC type-wood,hogwire, insulation, batting, burlap) What a difference across the whole spectrum and image/soundstage improvement! I sent an email but you probably didn't get it. After putting in the inner hogwire my friend and I developed a method wereby we "rolled" the insulation and outer hogwire together like a cigarette. We had the outer hogwire on the floor with the insulation on top. It ended up being a nice timesaver, we pre-sprayed the joining edges of the insulation and ended the "roll" where the insulation and outer hogwire met. We had no problem making a good seal that you said was all important. It takes two people though. One on each end making sure that seal maintained its integrity while rolling.
ET
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