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help me choose a supertweeter
help me choose a supertweeter
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Old 27th June 2006, 11:08 PM   #1
SPU_SPU is offline SPU_SPU  United States
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Default help me choose a supertweeter

I've been listening to a pair of Voigt Pipes w/ Lowther PM6A, and I've decided I want to try adding a horn superwteeter. The Lowther's are 15 ohms, and I use the 16 ohm taps on my SET amps.

Anway, I was wondering if someone could help me out with recommendations (in any price range), or at the very least teach me what impedance + efficiency I should be looking for in the tweeter... and perhaps how to determine which cap values to experiment with?

Thank you for any comments!
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Old 28th June 2006, 11:10 AM   #2
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK

the expensive option is one of Fostexs premium supertweeters :


However the more mundane FT17H at $70 a pair should be ideal.

Use a 2uF or less foil capacitor and an 8R L-pad.


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Old 30th June 2006, 08:43 AM   #3
Nuuk is offline Nuuk  United Kingdom
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Location: Somerset, SW England
However the more mundane FT17H at $70 a pair should be ideal.
Or, if you can find them, the Radio Shack bullet tweeters that are reported to be based on the Fostex F17H design, and are often seen on Ebay for peanuts.
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
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Old 3rd July 2006, 07:32 PM   #4
Jon Ver Halen is offline Jon Ver Halen  United States
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Location: Chicago area
Default Different thoughts

1st of all I have been very happy with the Fostex T90a and T900A. The T900A is a little bit nicer, but much more expensive. Either will work well.

In theory (that is to say, I have not tried it yet) a .56 mh coil in series with the PM6A combined with a zobel using a 1 uf cap and a 22.5 ohm resistor will cross you over around 11 kHz.

Use a 2 uf cap with a .2mh coil for the tweeter crossover (12 db, with the inductor in parrellel with the driver, and the cap between the amp and inductor). Then use an L pad to adjust the volume. Personally I would not worry about the fact this is 8 ohm driver as compared to the 15 ohm Lowther, but if you want to worry feel free to go to step 2.

If you enjoy the challenge you can convert these values to a 16 ohm crossover and then add an 8 ohm resistor in series with the driver, between the driver and the inductor. Then you have to develop a proper pad network to bring the efficiency down from 106 db of the tweeter to the 97 db of the Lowther. Keep in mind that the Lowther is 97 db @ 3.87 volt (as it is 15 ohm) whereas the Fostex is 106 db @ 2.83 volts. Math is not hard, and you should enjoy it.

All that being said, these mesh very well with Lowthers. Trying ribbons in the past found them lacking in dynamics, with a kind of boring sound as a result.
Jon Ver Halen
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