Albert: I don't know the specifics of your speakers, but if their resonance point is noticeably above 12 Hz, and i suspect it is, introducing gain below that point will actually increase distortion, reduce transient response and lower the max spl ( dynamic range ) of the system.

In such a case, one might be better off limiting the bandwidth of the woofer section and lowering the gain at a higher frequency. This in turn reduces power draw from the amps, lowers the operating temperature of the woofers due to a reduction in power dissipation and increases the performance capacity of the system above the actively equalized cut-off frequency.

This is a common trick used by intelligent designers of vented speakers that are bandwidth limited i.e. using active equalization and a high-pass filter to both increase extension while lowering distortion. Bobby Palkovic of Merlin uses such an approach in his "BAM" module. Electro-Voice also used this approach in their "Interface" series of speakers back in the 1970's, which were the first vented designs based on Thiele-Small parameters.

As a side note, this type of circuitry is more effective with sealed designs as sealed designs have a shallower roll-off below resonance. In effect, they can get away with less active boost below resonance, therefore reducing power draw and thermal dissipation. On top of that, sealed designs maintain consistent damping characteristic below resonance, whereas vented designs lose any damping characteristics that the cabinet itself may have contributed. The lack of damping increases excursion and distortion as the driver is now "unloaded". This is where the high-pass filter comes in, limiting the lower frequencies and letting in the higher frequencies that won't cause as much excursion and distortion. Sean
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sean January 02, 2005 18:08

Zaikesman: I never studied the patent on this design, so i can't tell you exactly how & why. All i know is that it works.

As to the bandwidth of a square wave, it wouldn't be a square wave if it required infinite response at high frequencies. That's because "everything" suffers from some type of bandwidth limiting. 10x the bandwidth of the primary signal will get you very slight but visible rounding of the leading edge and 15x will look "perfect" to the naked eye. If you really wanted to get technical, you might need wider bandwidth than 15x, but you're way more than splitting hairs by that point. Sean
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sean December 31, 2004 23:17

El: I don't want to sidetrack this thread, but even the Ohm Walsh drivers will fall on their face with a square wave above a certain frequency. In order to produce a "reasonable" facsimile of a square wave, the circuit or driver has to have at least 10x the bandwidth of the center frequency used to generate the square wave. Given the limited high frequency extension and speed of this large cone, one would have to use a signal centered below 2 KHz ( at the utmost extreme ) in order to achieve a "decent" looking square wave. As one went down in frequency, the more articulate and square the wave would look using this driver. Given that most drivers can't do this at all at any given frequency, that says a lot about the potential of such a design.

This is one of the main reasons that this design approach has such a natural harmonic structure. Combine this with the very airy and ambient omni radiation pattern and you've got a one of a kind presentation. Now factor in that all of this eminates from a point source and you've got bass response that can shake the house and one might be able to understand why i like this design so much. Sean
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PS... a "perfect" square wave requires a bandwidth that is at least 15x higher than that of the center frequency of the test signal. At 10x the bandwidth, it still looks quite good with a slight amount of rounding of the leading edge.

sean December 31, 2004 16:51

I was just going to drop you a line and see how things were going. This post saved me the trouble and probably answered a few other questions too. Thanks for the update : )

I hope that you have a safe and enjoyable trip. I'd really like to wander off to some of these various events, but unfortunatly that four lettered word called "work" gets in the way. The fact that i'm already taking off most of Christmas week and the entire week between Christmas and New Year's would make it hard to disappear again right after that. I'm glad that we've got someone like you there to snag images for us. The only request that i'll put in is that you should try and find some more of "Santa's Helpers" or the "Elves" that you took photo's of before. I thought that some of the equipment "stacked up" quite nicely against the competition : ) Sean
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sean December 20, 2004 01:05

I had Tele's in the front and a quartet of Electro-Harmonix in the back of my Marantz 8 and was quite happy with the combo. Then again, different circuits produce different sonics, so.... That amp went the way of the wind though as i traded it for a few thousand dollars worth of test equipment. There's just something about irreplaceable all original vintage pieces of hand built tube gear in mint condition that is 40+ years old that drives the value up : ) Sean
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sean April 23, 2004 20:34

Albert, those pictures look all blurry. As a photographer, i would have thought that you would have stopped using a Kodak Insta-Matic years ago : )

All i can say is that i am in awe. Given how your room re-design came about and what we discussed privately, i can't wait for something bad to happen to my house : )

Honestly though, i bet that Arnie has already contacted you about doing a small spread on A-gon. If he hasn't, you need to contact him and start talking turkey. After all, you did mention Thanksgiving : )

With the quality of work that was done and your top-notch photo's documenting it step by step, it would make for one helluva interesting and educational reading experience. I'm sure that anyone and everyone that visits these forums would like to see something like this. Hell, it would've made a GREAT series on one of those home improvement shows on tv !!! Sean
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PS... When can we buy the videotape ??? : )

sean May 31, 2002 23:23

We all know that a carpenter's roof leaks and a shoemaker's kids go barefoot. So why would Albert, who is a photographer by trade, be any different ? Asking him to take a "quick photo" would be like asking a mechanic to do a "5 minute tune-up" on his own car : )

Having said that, even the photo of Albert's "old" room looks much like i had imagined it from his posts i.e. truly tasteful, elegant and functional all at the same time. If the new room is that much more functional, acoustically correct and nicer looking, we might have to start billing Albert's advice as coming from a "better homes and gardens acoustician" : )

Kudo's on a job well done to one of the truly nicest guys on these forums. I aspire to have both a house and system as beautiful as what you've shown us. Sean
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sean May 30, 2002 02:13