Limited to high frequencies in all liklihood but dependent on the specific panel, of course.
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Elizabeth - I don't think that is true, because:
1) You can go to the manufacturer's page and view tables of the amount of absorption per frequency over a range of frequencies
2) The limitations of absorption pattern will not be any different for commercial products that are made of the same fiberglass
That said, I agree that the compressed fiberglass panels do have a sonic signature, and they do not absorb evenly across the whole spectrum. Do you have other suggestions for better absorption patterns?
I'm building twelve 4x8 panels using 2" rigid Johns Manville 817 panels:
Look at the table showing sound absorption coefficient at 125Hz for 1" and 2" thickness. You can see that 1" panel is useless at lower frequencies in spite of 817 material being twice dense (and 2x more expensive) than standard 814 (more common). Ideal would be the panel made of two 817s (without backing) - total 4" in thickness but unfortunately there is also WAF.
Corning also sells this stuff and is more common in some areas.
Check my system updates. I recently added a few very inexpensive Auralex SonoLite 2 x 2 x 1 Inches Panels on my sidewalls that work as advertised. Just over $50 for 3 on sale on Amazon. They also sell wall mount bass trap panels and other isolation devices that I would readily try as well if needed.
Going from hard reflective to soft absorbent surface at prime wall reflection points is bound to have an effect on the sound, probably noticeable in most/many cases. Office partitions as well. Perhaps not to the same extent per square foot as other materials that are designed for the job. Could be a good or bad thing. As usual, it all depends...
KIjanki, by chance, I have similar bare insulation material from house construction covering the concrete wall behind my old OHM Ls in my basement unfinished area. Works to good effect there.
Mapman, I wonder if placing 2" panels on opposite walls works the same way as 4" panels on one wall? It should.
Kr4, I have a lot of reverberation between tall walls (cathedral ceiling). It would be ideal to space panels away from the back wall but I cannot do it being forced (by layout) to set my speakers and sofa on long walls. I can always control amount of reverberation by removing or adding panels.
"Mapman, I wonder if placing 2" panels on opposite walls works the same way as 4" panels on one wall? It should."
I don't think so in that these are for controlling flutter echo and slap back, which are artifacts of more directional higher frequencies, as I understand it.
I have these placed at primary reflection points for my two main listening positions (my OHMs are omnidirectional and I listen from multiple locations normally). There are two such points on one side wall and 1 on the other (an open area extends out on that side in my L shaped room where I would add a similar second panel on that side if it were needed otherwise).
As I mentioned above, Aurelex has a similar 24X24X3 inch (same width and height, but thicker)bass trap panel product. Added thickness makes these more effective in attenuating longer wavelengths of low frequencies, as I understand it. These (for bass) might work equally well or maybe even better perhaps with greater thickness near one side corner rather than less on two side corners.
Here is some useful information -
Here are some of my thoughts for your consideration -
Most dedicated audio rooms I see are overdamped. The outcome is people have chosen brighter sounding equipment, and play at too loud levels to overcome the "dead" room. The overall sound becomes oppressive and compressed.
Most audio writers and manufacturers recommend placing speakers in dead spots - antinodes. Examples of these types of speakers placement are the rules of thrids, rules of fifth's etc.
I do the opposite - I start by placing the speakers in the most resonant part of the room, and then moving the speakers off the resonant node just enough to balance the sound. This way the speaker is balalnced, but not "fighting" against a dead spot. You will find a full description of this methodology as espoused by the designer Joahcim Gerhard in the Stereophile review of the Audio Physic Virgo's.
"In fine-tuning the room for both frequency response and imaging, Gerhard first divides the room into two grids. One is even divisionshalves, quarters, sixteenths, which represent reinforcement nodes; the other is oddthirds, sixths, ninths, which represent cancellation nodes. These measurements should be done to the inch with a tape measure and not be guesstimates. Ideally, you'd draw out each grid in a different color and overlay the two.
If your room is such that you can put your speakers at the halfway point in the room with the speakers against the side walls, the next move would be to move them laterally closer together to the quarter point on each side. That would be your ideal starting point for maximizing bass pressurization and creating a credible soundstage.
Now begins the battle of optimizing imaging and frequency response. If bass is too strong, you could go to an anti-node that could either be forward or back or side to side to one of the "third" points. While the trend is toward more bass as you move the speaker closer to the back or side walls, there are cancellation points as you go toward the walls."
I used to be a high end importer many years ago, and have a wide range of experience with speakers such as Martin Logans, Apogees, Duntech's, Proac's etc and in every instance following this methodology has improved the system and given the most natural and transparent view of the soundstage and spectral balance. I strongly suggest you have a read of this review and think about it.
I want to point out that (1) 3" is not sufficient for a bass trap, depending on the construction/materials, (I use 6" OC705 and tuned traps) and (2) the plastic foam used by Auralex is less efficient than is packed mineral wool (fiberglas, OC 703, OC 705, etc.) and, therefore, needs to be even thicker for low mids.
One reason for so many rooms to be overdamped is that the user is installing more and more wideband panels in an effort to deal with sub-Schroeder frequencies and, in the process, is overdamping the mids and highs. Note that some suppliers, e.g., RealTraps, offers the option of a reflective "skin" on their traps to avoid this problem.
The Audio Physic and Sumiko Master Set speaker set up guides have been very useful to me. In fact, as I have become more familiar with their processes and using one or a combination of both of these methods to first set up and adjust the speakers, I have gradually reduced my need for room treatments. At this point I use a bare minimum number of bass traps/panels behind the speakers due to sliding glass doors. While I agree room treatments can be very beneficial, I think we sometimes use that as a crutch and underestimate the benefits of really good speaker placement.
Marqmike, here are a couple of links. These differ slightly but the concept is very similar. You can actually hire someone trained in this process as well to do the set up for you. I just followed the methods described in the forum posts. You will note one recommends two people be involved, but you can do it yourself too as I do.
As you can see the set up involves removing any room treatments. Then when completed, adding back room treatments as required to finish the job. I have found this to be quite effective and now find I need to dump some of my excess room treatments.
Another effective method to avoid using or overusing room treatments is the diagonal set up. Then of course there is near field listening. I have tried all these methods with very good results in a variety of less than friendly rooms. Although all this can be intimidating, it's really not so hard to figure out. It does take an extreme amount of patience though and if you are not single, a compassionate significant other.