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Howard Ferstler's main AV system

Howard Ferstler

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I recently made some changes to the AV system in my main room. This rig had previously been used as my reference set up when doing various product reviews, including level-matched A/B speaker comparisons.

The changes involve downsizing instead of the usual "more is better" upgrades, primarily because my wife and I are both on a "less is more" kick, and, well, I am out of the audio-writing business and do not need an elaborate system any more. The second subwoofer (previously, a big SV unit that had been in the right-front corner) has been removed and now all of the bass is shunted to the Velodyne F1800RII in the left-front corner. (I think this has honestly made the low-bass performance a bit better.) The equipment rack has also been downsized, with several processors, a laserdisc player, second DVD player, and a Carver M500 that had been used to power the IC-20s (with a Yamaha RX-Z1 receiver then powering the other channels) removed. The cabinet has been cut down, and now all it holds is a DVD player (a decent older Panasonic model), the RX-Z1 receiver, and a Rane THX-44 equalizer that EQs the three front speakers and the subwoofer. The system uses an older, ceiling-mounted Sharp video projector that will hopefully one of these days be replaced with an HDTV version.

The satellite speakers remain the same: IC-20 mains, a custom center speaker made by me (an MTTM vertical array, with Allison M and T drivers and an IC-20 woofer, and a crossover that is a combination of Model One and Model 9 elements), four Model Four units used as surround speakers (two can be seen as front "effects" speakers in the photo; the other two are further back and out of the picture), and a pair of out of the photo small back-surround systems I built using NHT and Radio Shack drivers.

Believe it or not, the downsized package sounds as good as the previous one, mainly because speakers determine things mostly in audio. The reduction in power (to half what it had been) has had no impact at all.

The photos show the front wall (my backyard woodworking shop can be seen through the window) and the center speaker with its grill (a cut-down IC-20 grill) removed. The room is 22 feet wide, a bit more than 18 feet deep, and with the ceiling being 8.5 feet high. The space is lined fairly heavy with bookshelves full of books and discs.

Comments on this system are always appreciated. Note that I have a second system in another part of the house that has a new 56-inch TV monitor and some speakers I built using a mix of other brand and Allison drivers. We use that one for most of our video work, with the system discussed here mostly for music.

Howard Ferstler


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  • 3 weeks later...
Guest BartJY

I have a pair of Allison Three’s so I thought I knew about Allison speakers. But, after looking at your picture of the IC-20s, I see that there is still more to learn. Question: What am I looking at for the base driver? It looks like the backside of a woofer. Is that correct? How does that work? Tell me about it.



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Several later-generation dual-woofer Allison speakers had this arrangement, known as "push-pull" woofers.

The idea is to mount one woofer in-firing and one woofer out-firing, wire them electrically out-of-phase, so that they're acoustically in-phase. The intended benefit is this: If you have truly excellent manufacturing uniformity from woofer to woofer, then having the woofers fire in opposite directions will allow them to cancel out each others' mechanical non-linearities, thereby reducing even-order harmonic distortion.

Again, this assumes that each individual woofer has virtually the exact same mechanical characteristics as the next one. You really need very close manufacturing tolerances for this to work.

And since it only cancels even-order distortion, it's of somewhat limited value, since odd-order distortion is more audibly-objectionable. In any event, the human ear is remarkably non-sensitive to deep bass harmonic distortion under 5-10%, as long as there is no really obvious mechanical distress noise (VCR, port chuffing, etc.) accompanying the distortion itself.

But Allison's push-pull woofers were a lot like your grandmother's chicken soup: "It couldn't hurt!" And besides, it also provided Allison a nice marketing story that reinforced their engineering reputation.

Steve F.

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