| Woofer-tweeter [message #39863] |
Sun, 12 January 2003 12:08  |
Mike Centracchio
Messages: 18
Registered: May 2009
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Chancellor |
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Could use help,
I came across a woofer and a tweeter cheap, so I bought them.
The woofer is a Selenium 8pw2, 8 inch, 8 ohm, 70-8000 Hz, 94 dB SPL.
The tweeter is a KSN1036A 3000-40000 Hz SPL, 90 dB
Selenium suggests a .66 cu/ft ported box (3 inch dia x 2 inch lg)
I took a look at (basic piezo x-o) found on a link in this forum.
I guess I could use these cap, and inductor figures for a cross
at 3500 or so. Also had the idea to model it after 1Pi, using just a woofer inductor.
My main question is how to compensate for the difference in the dB SPL between the woofer and tweeter.
Any help is appreciated
Thanks Mike
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| Re: Woofer-tweeter [message #39864 is a reply to message #39863] |
Sun, 12 January 2003 12:52  |
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Wayne Parham
Messages: 18683
Registered: January 2001
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Illuminati (33rd Degree) |
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To attenuate a piezoelectric tweeter, use a capacitor in series. Since the tweeter is primarily capacitive, a series capacitor forms a voltage divider rather than a frequency splitter. There is no filter function when components having the same reactive properties are connected together. So a capacitor/capacitor network forms a simple voltage divider, much like a resistor/resistor network does. For a KSN-1038, you can expect attenuation in the following amounts: 1.0uF 1dB
0.5uF 2dB
0.33uF 3dB
0.22uF 4dB
0.1uF 7dB These values are what you'll get if you connect a capacitor in series with the tweeter, and do not use any other components. That gives broad-band attenuation only, and does not act as a crossover. See the post called "Pi implementations of quartz piezoelectric tweeters"
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| Re: Woofer-tweeter [message #39874 is a reply to message #39863] |
Mon, 13 January 2003 06:36 |
JLapaire
Messages: 156
Registered: May 2009
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Master |
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Hi Mike,
Your post came at a good time, as I'm playing with a piezo driver too. Wayne has posted links to piezo implementations in the past, and I think you're looking for a 70v matching transformer to step up the voltage to your tweeter. Kind of takes the fun out of buying a really cheap tweeter if you have spend $6 more for a transformer, but there isn't any other way to boost them.
On the other hand, the KSN 1038 that Wayne uses is also very cheap, has the "good" motor, and matches a 97 db driver. You'd only need a small cap in front of it to match yours.
I'm trying to slap some manners into a KSN 1188 compression driver and a paper mache 400 hz tractrix horn - great fun indeed.
Most of the piezos sound (to me) kind of tizzy and harsh, the 1038 does not.Now to paint some nice black roofing compound on the outside of the paper horn without destroying my clothes... John
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| Re: Woofer-tweeter [message #39883 is a reply to message #39876] |
Tue, 14 January 2003 03:20 |
JLapaire
Messages: 156
Registered: May 2009
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Master |
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Hi Dave,
If I can squeeze a little more HF out of them (it) I might bring it with a Karlson box or a 2-12" BR box I've been fooling with. The lower sensitivity of the BR allows more room for passive EQ, but that big piezo driver is kind of a strange beast to work with. I'll try a Zoebel on the transformer tonight.
Might wind up just bringing some bottles (liquid refreshment type) and my ears.John
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