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Multi-Way Conventional loudspeakers with crossovers

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Old 18th July 2001, 10:34 PM   #1
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I am working on building a quadraphonic speaker system involving 4 10" Pioneer poly cone woofers and 4 Motorola horn tweeters. I'd like a crossover right in the middle of the two ranges (26Hz-2.5Khz and 1.8KHz-30KHz, so 2.15KHz would probably be ideal). But as soon as I got the calculator out, I hit problems. The major problem is that the tweeters are rated at "high impedance at low frequencies" and the woofer is 6 ohm. I have no idea what sort of crossover network I need to use!
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Old 19th July 2001, 02:14 AM   #2
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These tweeters are capacitave devices which is why the impedance increases as the frequency decreases.

Just put an 8 ohm 10-20 watt resistor across the tweeter and consider it an 8 ohm driver.

I don't think you will happy with these drivers.
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Old 19th July 2001, 02:52 AM   #3
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What about FADD64-58F 3/4" textile dome tweeters
with A25FU30-51D 10" foam surround poly cone 6 ohm woofers?

I'm on a budget here. I can't really afford to spend more than $80 CDN per speaker on the drivers. I don't need perfect sound, I just want good sound with powerful bass.
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Old 19th July 2001, 03:04 AM   #4
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I don't know about those particular tweeters but I see I've steered you in a reasonable direction.
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Old 19th July 2001, 07:59 PM   #5
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Ignite,
Beware of foam surround drivers, as the foam tends to rot out after, say, 5-10 years. Rubber surrounds are a better long-term bet, reliability wise.

Grey
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Old 20th July 2001, 02:37 PM   #6
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Ignite,

If you are talking about the Motorolla Piezo Model KSN1025s you will end up with the kind of sound that you are describing. These tweeters are pretty good, as compared with the rest of the Motorolla Piezo clones and certainly better than all of the other cheaper far-east brands.

Use the normal kind of crossover for the woofers, second or fourth order or whatever else you prefer. Use a metallised plastic film capacitor of 4.7uF 250V or higher for the tweeter. If you find that the SPL of the tweeter is more then that of the woofer, you may use suitable low value, high wattage resistors to equalise the sound. Since these tweeters present a high impedance to low frequencies, higher order crossovers are not required; you may change the value of the capacitor within limits.

Crossing over the woofer also at 6db per octave is a good choice. Following my suggestions may not be theoretically precise but you will be more than surprised with the results. I have used such configurations in the past with great success.

In fact, I use an active crossover network crossed over at about 2KHz for the highs, (and 400 Hz for Low/Mid) for outdoor performances, and the results obtained with the above mentioned tweeter model have been more than just satisfying. Check out the passive filter first since it is not expensive before widening your choices.

Cheers.
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