Anyone used a SEAS COAXIAL T18RE/XTVFC ? - diyAudio
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Old 27th November 2004, 01:32 AM   #1
synergy is offline synergy  United Kingdom
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Default Anyone used a SEAS COAXIAL T18RE/XTVFC ?

thinking of putting a couple in some T-Lines

the initial sims seem to be pretty good (F3 at about 35Hz i think only my electric just went out so i've got to start a fresh )

before i do and more importantly before i spend any money on a pair has anyone got any thoughts?

dave
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Old 27th November 2004, 03:47 AM   #2
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Tony Gee put one in a ported box and seems to think pretty highly of the result.

http://home.hetnet.nl/~geenius/USB.html

I don't know if that's of any help, but it's nice to know a respected designer has used them successfully. And there are lots of measurements and a complete crossover that may be helpful.
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Old 27th November 2004, 01:23 PM   #3
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I'm very tempted to try one of these coaxials, too, but I would use it in a true 3-way. Because of the coaxial tweeter position I would expect that there will be much IM distortion with big woofer movement - i.e. if to try to produce real bass. I suppose this is the reason why most people who tried them weren't too satisfied.
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Old 27th November 2004, 11:04 PM   #4
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Quote:
Originally posted by Hertzschmerz
I'm very tempted to try one of these coaxials, too, but I would use it in a true 3-way. Because of the coaxial tweeter position I would expect that there will be much IM distortion with big woofer movement - i.e. if to try to produce real bass. I suppose this is the reason why most people who tried them weren't too satisfied.
Agreed.
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Old 28th November 2004, 04:54 PM   #5
Pallas is offline Pallas  Pakistan
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Quote:
Originally posted by Hertzschmerz
I'm very tempted to try one of these coaxials, too, but I would use it in a true 3-way. Because of the coaxial tweeter position I would expect that there will be much IM distortion with big woofer movement - i.e. if to try to produce real bass. I suppose this is the reason why most people who tried them weren't too satisfied.
You know, I was just thinking that a Seas coax combined with one or two Adire Extremis 6's would be a killer compact and shielded monitor for audio or HT, and not much (if at all) more expensive than many of the boring and sterile Seas Excel or ScanSpeak 7" 2-ways that seem to be cropping up like high priced locusts. With a T18/Extremis combination, you'd get the coherency of a dual-concentric from the Seas and the Extremis would be there to keep the Seas woofer from moving too much while providing a solid bridge between mains and sub.

It's not something I'll probably ever do, at least not at this point, because I'm more into bigger dual concentrics. But for someone who needs a smaller/thinner speaker and still craves some measure of coherency, it could work out very well.
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Old 28th November 2004, 05:41 PM   #6
rdf is offline rdf  Canada
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Quote:
Originally posted by Hertzschmerz
Because of the coaxial tweeter position I would expect that there will be much IM distortion with big woofer movement - i.e. if to try to produce real bass.
How so? Is this different than a regular two-way? IM is usually a concern when the high frequency radiator is subject to woofer cone's motion, a common complaint against full range drivers. If I'm not mistaken this Seas tweeter is fixed.
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Old 28th November 2004, 06:47 PM   #7
Wodgy is offline Wodgy  United States
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For what it's worth, here's a design for the T18RE/XTVFC by one of the engineers at Seas:
http://www.madisound.com/Seas%20H114...nd%20Xover.pdf
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Old 28th November 2004, 08:52 PM   #8
synergy is offline synergy  United Kingdom
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thanks for the responses

these will be used as DJ monitors built into the deck stand i'm going to build

they'll end up being about a meter or so away from my head and placed against a wall in a small room (9' x 11')

because they'll be nearfield i need a point source design and did think about a full range driver but for the music i play it would be a tough job for a single driver to cope with both lows and highs

i was looking originally at the beyma 8BX but whilst i'll have no trouble with any length of line (they'll become the legs of the stand) the 8" diameter means the cross-section may cause problems

the other problem with the 8BX is the Fs being 52Hz whilst room lift is going to help the overall response it wont naturally play down as low as i need

does anyone have any thoughts about another driver that might be suitable?

the music i play has a lot of content around 30-45Hz but i don't want a sub and satelite design as i need to be able to hear the bass first hand not filtered up to ear level when standing

cheers
dave
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Old 29th November 2004, 12:46 AM   #9
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Quote:
Originally posted by rdf


How so? Is this different than a regular two-way? IM is usually a concern when the high frequency radiator is subject to woofer cone's motion, a common complaint against full range drivers. If I'm not mistaken this Seas tweeter is fixed.
Good question. Yes this tweeter is fixed. I see it this way: The woofer cone in this design acts as a kind of waveguide for the tweeter. The listener in front of the loudspeaker hears the sound of the waveguide rather than the sound of the tweeter itself. Now this waveguide is not static but moving...

If I understood correctly, this is the reason why the studio monitor manufacturer ME Geithain put the tweeter in the Nearfield models on a plate in front of their woofers which covers most of the woofer cone.

Click the image to open in full size.
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Old 29th November 2004, 02:18 AM   #10
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Quote:
Originally posted by Hertzschmerz


Good question. Yes this tweeter is fixed. I see it this way: The woofer cone in this design acts as a kind of waveguide for the tweeter. The listener in front of the loudspeaker hears the sound of the waveguide rather than the sound of the tweeter itself. Now this waveguide is not static but moving...

If I understood correctly, this is the reason why the studio monitor manufacturer ME Geithain put the tweeter in the Nearfield models on a plate in front of their woofers which covers most of the woofer cone.

Click the image to open in full size.
Almost all of Tannoy's coaxial drivers use the woofer as the waveguide, I think.
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