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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Deliberate or not. posted by klausDK on April 3, 2008 at 01:44:35:
KlausDK wrote:
<< The lessons to be learned are to take something for granted and learn to think outside the box. Charles Hansen deliberately did so when he gave the Avalon Eclipse a crossover frequency at a stunningly low 1080 Hz. I salute him for that, GREAT!! >>
Thank you for the kind words. When that speaker was designed (roughly 20 years ago), it was almost certainly the first two-way speaker to provide pure pistonic action throughout the full frequency range. (The actual crossover point was 1000 Hz, both because I like nice round number and because the characteristics of the tweeter allowed the crossover to be simpler at that frequency.)
We kept the idea secret as it was so obvious (at least in hindsight) that we were afraid it would be copied. Yet 20 years later there are still only a handful of speakers that offer truly pistonic operation, freeing the music from the strong colorations of resonating diaphragms.
Donald North wrote:
<< Every time you lower the crossover point of a tweeter by 1 octave (3000 to 1500 Hz for example), you increase the tweeter's excursion by 4x to maintain a constant SPL. 4x the excursion significantly increases the distortion from the tweeter due to nonlinearity in the tweeters suspension and magnet structure >>
Absolutely true.
All speaker designs consist of a long series of compromises and tradeoffs. In this case, the tradeoffs were well worth it. The advantages of pure pistonic action plus the ability to have a smooth polar pattern (dispersion) throughout the crossover region were (and are) significant. Regarding the distortion, this is a trivial matter. Every day speaker designers figure out the maximum output level versus distortion for woofers.
But for some reason almost nobody seems to do the same thing for tweeters. I guess it's that old "box" conundrum. Back then I didn't have the resources to make custom drivers, so the midrange distortion levels were merely average in that design. But look at what Jim Thiel has done. He has a 1" metal dome tweeter with an underhung voice coil and an Xmax of 3 mm. Go ahead and figure out the maximum SPL from that at 1 kHz. I think you'll find it is more than adequate for normal home playback levels. And I'm sure that the distortion is exceedingly low on that design now that tools like magnetic FEA are widely available.
What I don't understand are all the people that keep putting the same old recipe in a new package. The last thing the world needs is another 6-1/2" two-way with a crossover at 3 kHz. There must be thousands of designs using that recipe. The definition of insanity is repeating the same actions and expecting different results. I guess most speaker designers fall into that category. Personally, I'd rather do something new and exciting and different that expands the envelope of what is possible. If I can't do that, then I don't bother to bring a design to production. YMMV.
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Follow Ups
- Reply to multiple posts - Charles Hansen 09:04:59 04/04/08 (0)
- RE: Reply to multiple posts - caspian@peak.org 08:41:10 04/24/09 (0)
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