Are you then simply dismissing KEF's claim of much greater internal compliance enhancement using activated charcoal than by purely absorptive materials? Keep in mind that KEF is using their ACE techology in several speaker lines, including their flagship line where they are featuring ACE right up there with Uni-Q.
If I find KEF republishes their white paper, I'll try to let you know.
Somebody thoughtfully saved and reposted the KEF ACE white paper.
http://francis.audio2.pagesperso-orange.fr/acewp.pdf
http://francis.audio2.pagesperso-orange.fr/acewp.pdf
Thanks for the paper. Written for marketing, not for AES. It has just enough hint that they may have something there. For what I read, it has a little problem passing the sniff test, but not like all the "science" of wonder speaker cables. Nobody carries Kef around here any more to go listen to. From the last ones I heard, I know why.
I am all for innovation. 50% reduction in Vb sure could be handy over the 15% max one can get from fiber. Fs is only one parameter. What does it do to Qts or internal reflection control? A granular material may have higher friction between grains which would correlate with my findings that slippery fibers don't work anywhere near as well as rough fibers. If it was just about pore size, I would have expected more improvement using 4 Lb foam over 2 Lb in my tests.
If anyone has a source for this material, I will gladly test it compared to the best fibers. If it worked, I am sure someone like Madisound or Parts Express would gladly carry it.
I am all for innovation. 50% reduction in Vb sure could be handy over the 15% max one can get from fiber. Fs is only one parameter. What does it do to Qts or internal reflection control? A granular material may have higher friction between grains which would correlate with my findings that slippery fibers don't work anywhere near as well as rough fibers. If it was just about pore size, I would have expected more improvement using 4 Lb foam over 2 Lb in my tests.
If anyone has a source for this material, I will gladly test it compared to the best fibers. If it worked, I am sure someone like Madisound or Parts Express would gladly carry it.
I was thinking just using a fleece blanket behind the driver. I worry about dust getting into the motor. So far, I have only found manufactures for coconut grains and the pet stores do not say what their filter media is made of. After my coffee I will go pick a driver off the shelf, build a test box and repeat the fiber tests while I look for the carbon. The box and driver I used last time is happy in use so I am not playing with it. I have several 5's and 6's that should work for testing just fine.
Can't hit the stores today as the weather has set the area into a state of emergency so they don't want anyone going anywhere.
Can't hit the stores today as the weather has set the area into a state of emergency so they don't want anyone going anywhere.
BULK Granular Activated Charcoal for Air & Vapor Filters
Hundred bucks for a pail. Seems high so I'll keep looking.
Hundred bucks for a pail. Seems high so I'll keep looking.
Btw, in my last project particularly, I have included a means to replace the molecular sieve whenever its capacity to adsorb water vapor is depleted. This requires removing one or two drivers (it is a line array with 9) to access the molecular sieve reservoir, then the old molecular sieve needs to be shaken out, collected and discarded, then the speaker needs to be stood upside down while the new molecular sieve is added and the reservoir capped off.
With this approach, the activated carbon should last indefinitely, although it too can be replaced if necessary (a much messier proposition due to the much larger quantity used, intensely black color and tendency to produce clouds of carbon dust when it is transferred).
Both the molecular sieve and the charcoal are nonpoisonous materials, but one would not want to handle either more than necessary (as much to avoid contaminating the molecular sieve as anything), get in their eyes, eat, etc. For at least some molecular sieves, adding water can create a pronounced exothermic reaction. Also, leaving either in an open atmosphere for more than a few hours will significantly degrade its performance or at least capacity due to their adsorption of water vapor and any organic molecules they might be exposed to.
With this approach, the activated carbon should last indefinitely, although it too can be replaced if necessary (a much messier proposition due to the much larger quantity used, intensely black color and tendency to produce clouds of carbon dust when it is transferred).
Both the molecular sieve and the charcoal are nonpoisonous materials, but one would not want to handle either more than necessary (as much to avoid contaminating the molecular sieve as anything), get in their eyes, eat, etc. For at least some molecular sieves, adding water can create a pronounced exothermic reaction. Also, leaving either in an open atmosphere for more than a few hours will significantly degrade its performance or at least capacity due to their adsorption of water vapor and any organic molecules they might be exposed to.
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A 1cu ft SW with 4 10 inch drivers would seem practicable, especially with dual VC drivers, if used with activated charcoal. The molecular sieve replacement, if this approach is used, could be much less involved than what I described above, with a simple access cap at the bottom of the cabinet.
I did a brief survey of 10" subwoofer drivers available at Parts Express and saw some with a Vas as low as 0.35 cu ft, although the majority were 1cu ft or higher. IAC, with a compliance enhancement of up to 3 times using activated charcoal, this might be an interesting project and I am considering building something like this myself for my HT setup on a slightly larger scale with 4 12" per SW in a 2-3 cu ft cabinet.
I did a brief survey of 10" subwoofer drivers available at Parts Express and saw some with a Vas as low as 0.35 cu ft, although the majority were 1cu ft or higher. IAC, with a compliance enhancement of up to 3 times using activated charcoal, this might be an interesting project and I am considering building something like this myself for my HT setup on a slightly larger scale with 4 12" per SW in a 2-3 cu ft cabinet.
Back on subject, in contact with the factory which produce the sub unit; concerned about sensitivity so specifically asked for an accurate 1W/1M reading and was sent up to date specs rather than written answer, guess I'll need to test it myself to be sure
it states 86dB (IEC baffle near-field, SPL shown for 2.83 V / 1M) View attachment 10 SW26DAC76-4-1.pdf
it states 86dB (IEC baffle near-field, SPL shown for 2.83 V / 1M) View attachment 10 SW26DAC76-4-1.pdf
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Considering that there have been other threads on this exact subject both in DiyAudio and in the internet generally, the answer would appear to be 'yes'.
I felt the KEF White Paper on their ACE technology was reasonably accessible (link provided earlier in this thread), and this technique is hardly too difficult for many DIY'ers to implement.
It's a natural particularly for anybody who wants to build a leading edge performance compact subwoofer. For instance, in a system with double the cone area for a given tuning in a given cabinet volume, it would allow an acoustic suspension subwoofer to equal or exceed the maximum output and efficiency of a BR version, with the greatly improved transient performance and much less steep 12db/octave rolloff of the acoustic suspension approach.
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Bill,
Yea, local source could be significant in cost for shipping. Woofers are heavy. I still fall back on the need to prototype before investment in exotic cabinetry. I see more problematic issues with your main design than just a too small sub box. I am afraid you will have some serious eq issues to work out with the round mains. Your ripple from edge diffraction could be 4 or 5 dB and the baffle step up in the critical 2 to 4K range.
thor,
The KEF paper you linked is what we call a "slick sheet" which is an advertising supplement with a few technical details to add support to the main advertisement. They are useful and I am not suggesting this or any other is incorrect. They are advertising, not technical papers. You might read some AEC or IEEE papers to see what a real white paper looks like.
Everyone should remember, just because something has a patent does not mean it works. It means it is unique in idea or unique in application, and is not perpetual motion. That is all.
Yea, local source could be significant in cost for shipping. Woofers are heavy. I still fall back on the need to prototype before investment in exotic cabinetry. I see more problematic issues with your main design than just a too small sub box. I am afraid you will have some serious eq issues to work out with the round mains. Your ripple from edge diffraction could be 4 or 5 dB and the baffle step up in the critical 2 to 4K range.
thor,
The KEF paper you linked is what we call a "slick sheet" which is an advertising supplement with a few technical details to add support to the main advertisement. They are useful and I am not suggesting this or any other is incorrect. They are advertising, not technical papers. You might read some AEC or IEEE papers to see what a real white paper looks like.
Everyone should remember, just because something has a patent does not mean it works. It means it is unique in idea or unique in application, and is not perpetual motion. That is all.
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