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Old 30th December 2007, 09:16 PM   #2961
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Default Re: Multiple tweeters

Quote:
Originally posted by dobias
Gentlemen,
Would someone either point me to a thread about multiple tweeters or provide an answer as to why I don't see more speaker systems with mutiple tweeters.
With the beaming of tweeters as a problem, I wonder why Bozak's solution hasn't been used more. The least he used was a pair of tweeters on about a 15 degree spread to either side of center. I always considered his bank of tweeters assembled in a hemispherical array as a grand, if not grandiose, solution.
I find that a second tweeter facing away from the listener
(bipolar?) helps to fill in the upper register.
With the availability of low cost piezo tweeters, would an array be worth trying or would the sound quality suffer?
dobias

The Dynaudio Confidence C4 uses 2 tweeters in a vertical configuration. I notice that they are spread about 2-3 inches apart. I assume to reduce the comb filtering effect. Generally most piezo tweeters sound bad. Also tweeters are usually more efficient that other non pro drivers so you don't need any extra ones when using dome tweeters as they have wide dispersion.

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Old 31st December 2007, 03:05 AM   #2962
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A long time ago, the second speaker I designed for Audionics used a pair of Peerless HFC-225 cone tweeters in a short vertical array. Normally, tweeter arrays are a Bad Thing, but the fairly large cone area of the HFC-225 made it behave a little more like a single vertical strip. Vertical dispersion was pretty narrow, as I recall - maybe a foot high at the listening position. Pointing the speaker right at the listening area was a good idea, otherwise it sounded kind of muffled.

I still have a soft spot for cone tweeters compared to domes; they have a gentler, more natural sound, and are free of the spit, sizzle, and upper-midrange "chrome-plated" effect of many domes. Looking back, I suspect the Peerless HFC-225's were based on the Bozak predecessor, with a 2" paper cone with a 1/2" nearly-flat aluminum dustcap in the center. Very nice sound indeed, limited only by rather modest power-handling and low efficiency (something like 84 dB/metre), thus the requirement to use them in pairs. In my experience, multiple dome tweeters sound kind of nasty - the annoying dome upper-mid colorations are still there, combined with a new, blurry, out-of-focus coloration (which I didn't hear with the Peerless cone-tweeter arrays).

The big problem with any array of drivers is non-coincident arrival times. This is not so important in the bass region, where wavelengths are long and floor and wall reflections merge with the direct-arrival wave. But at higher frequencies (say above 500 Hz) coincident arrival becomes more important, and becomes very important above 3 kHz, where multiple arrivals (multipath) have effects similar to severe diffaction. In subjective terms, image quality is diffused, front-to-back depth is shortened or eliminated altogether, and "phasey" colorations become audible with vocals and massed choirs. Chasing this coloration out of the MTM Ariel was a very tedious business, requiring offset drivers, large-radius corners, and a lot of phase-trimming in the crossover.

A quick way to test for coherence is listen to clicks and pink-noise, and compare by direct switching to a single-driver loudspeaker (quality of the single driver is not important for this test). If you hear blurred clicks or "phasey" pink-noise, the multi-driver system has problems with non-coincident arrival times. This is a very common defect, especially in audiophile boutique systems with large arrays of drivers and price ranges in the Porsche and Ferrari region.

Getting good treble with large dynamics and good (coherent) time response is not trivial.
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Old 31st December 2007, 01:00 PM   #2963
dobias is offline dobias  United States
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Default Multiple tweeters

Gentlemen,
Thank you, one & all, for the education.
Happy New Year,
dobias
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Old 7th January 2008, 09:03 PM   #2964
mige0 is offline mige0  Austria
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Location: Austria, at a beautiful place right in the heart of the Alps.
There fell a deep silence....




- and its only 27 postings to # 3000
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Old 7th January 2008, 09:29 PM   #2965
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Default 26

Can't wait to see some movement on this myself...

It will probably be bigger than domestically acceptable (to me) but certainly worth a listen once completed.

C
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Old 7th January 2008, 09:34 PM   #2966
agent.5 is offline agent.5  United States
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Default Re: 26

25

Like a wise man once said, it's not the size that matter mate

Quote:
It will probably be bigger than domestically acceptable (to me) but certainly worth a listen once completed.

C [/B]
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Old 7th January 2008, 10:57 PM   #2967
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All of the comments I want to make will be "moderated".

Best,

C
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Old 7th January 2008, 11:31 PM   #2968
AJinFLA is offline AJinFLA  United States
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23

Lynn's probably busy shopping at HD or Lowes. So he can finally build the fricative thing.

cheers,

AJ
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Old 7th January 2008, 11:54 PM   #2969
Retsel is offline Retsel  United States
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Default Other baffle designs

Since there is not too much action with this thread, I will direct people to another thread. JohninCR posted some time ago that he has been experimenting with different baffle designs. This thread summarizes some of his work and some initial impressions. If you remember, one of his very inovatiive designs was a waveguide baffle with rounded edges to deal with edge diffraction. If you have time to burn read this:

http://www.audiocircle.com/circles/i...?topic=36862.0

Retsel
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Old 8th January 2008, 03:08 AM   #2970
dogbert is offline dogbert  United States
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Default Gradient Helsinki 1.5

Here is a new design from Gradient
http://www.gradient.fi/helsinki15/

Not very much information has been posted yet. While they don't have a manual posted yet, I'm wondering how it is supposed to be placed in the room for the side mounted woofer to function as a dipole. Could it be that it is supposed to be placed at a 45 degree angle to the rear wall?

It looks like a waveguide mounted SEAS metal dome tweeter, a side-mounted 15" woofer, and a 6.5-8" midrange mounted in some type of diffuser. I'd like to hear more about it if anyone sees it at CES 2008.
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