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Supertweeters? [message #81335] Thu, 21 May 2015 14:17 Go to next message
rkeman is currently offline  rkeman
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The compression drivers used in most of the Pi Speakers offerings have rapidly falling output above 17kHz or so. Has anyone ever used a supertweeter (e.g. Fostex T90A) to extend the response to above 30kHz?
Re: Supertweeters? [message #81338 is a reply to message #81335] Fri, 22 May 2015 11:10 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

I have done that, and it does add "sparkle." But I don't like the fact that there's no-way to get summing right through the 90°x40° pattern. The wavelengths are too small and the distances between sound sources too great. So the top octave is a mess.

That said, it's dense interference up there. It's not like it forms discrete modes large enough to detect. They're all tiny little pockets of energy modes, with the direct sound being just like the reverberent field. So it's not like the interference is audible.

Still, I'd prefer to use a compression driver that reaches higher into the top octave than to use a supertweeter. There are some drivers with beryllium diaphragms that reach above 20kHz.

Re: Supertweeters? [message #81345 is a reply to message #81338] Sat, 23 May 2015 19:08 Go to previous messageGo to next message
rkeman is currently offline  rkeman
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Are there any drop-in beryllium compression drivers that you would consider for the 3Pi and 6Pi.?
Re: Supertweeters? [message #81348 is a reply to message #81345] Mon, 25 May 2015 09:19 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

I've used the TAD TD-2001 and would recommend it. It's a drop-in replacement for the DE-250.

I've never tested the 2002 but it looks nice too. It would probably need different R1/R2 values for a little more attenuation.

Re: Supertweeters? [message #81350 is a reply to message #81348] Mon, 25 May 2015 21:02 Go to previous messageGo to next message
rkeman is currently offline  rkeman
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The TAD compression drivers list at about $1800 and are limited in availability. Perhaps the Radian 450BePB?
Re: Supertweeters? [message #81351 is a reply to message #81350] Tue, 26 May 2015 08:37 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

I've not tried the Radian 450BEPB-8. If you do, please let us know! I'd love to see some measurements.

Re: Supertweeters? [message #81356 is a reply to message #81351] Tue, 26 May 2015 20:51 Go to previous messageGo to next message
rkeman is currently offline  rkeman
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The Radian 450BEPB-8 is certainly a consideration, but still runs about $500. Looking solely at the specifications, do you believe it has a reasonable shot at being compatible with the 3Pi/6Pi crossovers without substantial modification? The aluminum diaphragm Radian also looks linear to over 20kHz and costs only about $190.
Re: Supertweeters? [message #81358 is a reply to message #81356] Wed, 27 May 2015 10:25 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

In most cases, compression drivers are pretty similar, with breakup and HF rolloff being the two things to watch for. So for the most part, you can swap 'em around by just matching voltage sensitivity with R1/R2 values. But as always, the devil is in the details. You just can't really know for sure 'til you bolt it on and measure it.

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