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Multi-Way Conventional loudspeakers with crossovers

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Old 11th September 2007, 11:25 AM   #1931
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Default Re: Other drivers worth considering?

Quote:
Originally posted by mikey_audiogeek
Hi Lynn, have you considered Triangle drivers? Bit low on efficiency, but otherwise...

Triangle drivers

Best,
Mike
Um, I listened the Triangle speakers, and they didn't leave a strong impression. But they're hardly alone - the current fad for audiophile qualities like "fast" and "slam" has led not to lower distortion and more efficiency (which sure would have been nice), but drivers with poorer self-damping, only slightly more efficiency, and ever-more-harsh sound with very rough response at the upper edge of the band.

It seems that modern designers are reacting to these problematic drivers in two ways: the "minimalists" are going for lots of excitement and thrills, using the rock-bottom simplest crossovers possible (but with very expensive parts), and letting the peaks sail right through. Unsophisticated listeners - and worse, reviewers - interpret the peaks and harshness as "speed" and "accuracy".

There's a lower-profile school that believes in extensive computer simulation and using crossovers of almost unlimited complexity. This "objective" school of designers tend to discount esoterica like audibility of capacitor coloration - or even believe it doesn't exist - so has no problem with complex op-amp circuits, multiple transistor amps, or high-parts-count crossovers with extensive notch filters and shaping networks.

I'm not in either school. I don't want to use drivers with problematic responses - too much work for too little return. I still remember the bad old days of KEF and Audax Bextrene drivers, with their characteristic qualities of lumpy midrange, and dreadfully low efficiencies (85 dB/metre typical). Now, audiophile efficiencies have crept up to 90~93 dB/metre (with a tailwind), but the drivers have gotten really peaky, and in ways that are very hard to correct - the worst peaks are typically directional, making a crossover correction useless.
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Old 11th September 2007, 11:53 AM   #1932
soongsc is offline soongsc  Taiwan
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I quite agree it's hard to find excellent drivers these days. The development process is very complicated. With a little tweaking, or slight mod in design, the Jordans probably can become even better than they are today. These are one class of drivers that have great potential.
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Old 11th September 2007, 12:01 PM   #1933
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Quote:
Originally posted by john k...

As for extracting phase form amplitude data, at least of a single driver, minimum phase reconstruction work very well if you have good amplitude data. Maybe pro sound driver manufactures don't supply sufficiently accurate amplitude data, most reprtable hifi driver manufactures do (SEAS, Vifa Peerless, ScanSpeak, etc). While I haven't looked at large panel (like Martin Logan ELS) of horns, I have yet to measure a conventional driver, cone, dome or small ribbon, that doesn't reduce to minimum phase on axis over its useful operating range. So what that leaves is what is the driver offset, a problem which is still of concern using impulse response techniques. Of course, I wouldn't consider 1/3 octave RTA a legitimate measurement of a driver's anechoic response.
I think one difference between us is that I'm no longer interested in SEAS, Vifa Peerless, ScanSpeak, etc. They've had 15 years to respond to the vacuum-tube subculture and the constantly-expressed demand for substantially higher efficiency, and have done their best to ignore it and hope it would go away. Well, it hasn't, there's only been a trivial 1~2 dB change in efficiency in more than a decade, and to me, the mainstream audiophile drivers sound worse than what they were making 15 years ago. That's why I'm looking at different vendors than the usual mainstream candidates.

I'm surprised that you haven't seen drivers depart from minimum phase. This is one of the most direct indicators of cone breakup, and it's gotten much worse with the popularity of very rigid Kevlar, carbon-fiber, composite, ceramic, and metal cones. When a cone no longer moves as unit and enters the breakup region, there are multiple, asynchronous centers of radiation all over the cone. This is a clear indication of a "no-go" zone, and indirectly shows a requirement for an aggressive high-slope crossover to avoid gross coloration.

The drivers that are most interesting - to me - are the ones that don't require aggressive equalization to avoid harsh sound, and are characterized by smooth, well-controlled rolloff regions that retain their minimum-phase character to very high frequencies. Since the prosound manufacturers can't be bothered to supply either impulse or complete FR/phase data information, I'll be finding this out the hard ($$$) way - I'm not expecting any free loans from 18Sound, JBL, or Fertin.
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Old 11th September 2007, 12:38 PM   #1934
jzagaja is offline jzagaja  Poland
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soongsc

Do you know any other drivers than Jordan/Bandor/Goerlich that shares similar concept of using variable thickness and stiffness? For example with all-PP composites it is possible to vary local mechanical properties in in a wide range.
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Old 11th September 2007, 01:13 PM   #1935
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Quote:
Originally posted by Lynn Olson
I'm not expecting any free loans from 18Sound, JBL, or Fertin.
Maybe this is not true for 18Sound. Their headquarter is in Italy and I've seen Giacomo Previ answering kindly to an italian diy forum member. The company is 8 years old, I think a link to this thread would be enough for a loan request.
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Old 11th September 2007, 01:49 PM   #1936
Rudolf is offline Rudolf  Germany
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Quote:
Originally posted by Lynn Olson
... At 1.6 kHz, wool felt (and other damping materials) are starting work pretty well. Gary Pimm is using Bonded Logic "Ultratouch" fiber to fill his open-backed dipole woofers with great success - this recycled cotton fiber has high absorptive properties, and Pimm's system has the best, most crisp, and tonally realistic bass I've heard so far.
Ultratouch seems to have a very linear absorption capacity over a wide frequency range. I would rather imagine absorption rising with frequency, so that at 1.6 kHz the WR would be "dead" in the back. Something like 41 mm thick Basotect might achieve this:

Click the image to open in full size.
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Old 11th September 2007, 02:48 PM   #1937
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by jzagaja
soongsc

Do you know any other drivers than Jordan/Bandor/Goerlich that shares similar concept of using variable thickness and stiffness? For example with all-PP composites it is possible to vary local mechanical properties in in a wide range.
Above 300Hz or so, I have not come across any as good. Bear in mind that certain material characteristics are just not documented, unless one has dedication as Ted did, it is very difficult to find the right formula without massive trial and error. The one I'm tweaking does better in the lower frequencies, but is not as good in the higher frequencies. The region from 15KHz~30KHz is the most difficult region to tweak in small metal drivers and very critical. I remember that Ted mentioned it just extented to 30KHz by chance, I wish I had that kind of luck. I understand that some people are trying some alloy with lithium that seeminly has better damping characteristics, but have not seen any on the market yet.
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