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Old 14th June 2006, 06:11 AM   #1
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Default What about resonant frequency?

In multi-way designs, it is recommended that each driver only be used above its fs. In crossoverless full-range designs, the fs may be around 35-40 Hz, which is within the full-range signal sent to the driver. Does that present any problems, as it might with a midrange or a tweeter for example?

The Visaton TL16H horn tweeter has fs around 6 kHz and the recommended crossover is 7 kHz. But, as shown below, the response looks useable (to my uneducated eye) all the way down to 3 kHz, and the impedance peak is hardly noticeable at fs (again, to my uneducated eye).

What do you think would happen if I used the TL16H with a 3 kHz, 24 dB/octave crossover?
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Old 14th June 2006, 07:13 AM   #2
Nanook is offline Nanook  Canada
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Default can I use this tweeter..?

usually the rule is 1.5 - 2 octaves above for a shallow crossover on a driver..it "appears" that from 5k down to 1.8k the natural roll off is about 6 dB per octave, below that it looks like 15 dB or so. If the resonant frequency is say 7k, I'd go at least one full octave above or 14k! , 1.5 would be better @ 18.2K

This Visaton is listed as a super tweeter , and that is what it would indicate. Visaton even recommends a Xover frequency of 7.5k on their site.
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Old 14th June 2006, 07:14 AM   #3
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You avoid resonant frequency with multi-way designs because when making a passive crossover it's really difficult to take into account the big impedance and response changes, which will likely be just at the crossover frequency which makes things even harder.
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Old 14th June 2006, 09:43 PM   #4
Dumbass is offline Dumbass  British Antarctic Territory
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Quote:
Originally posted by Javachip
the impedance peak is hardly noticeable at fs
That's because the vertical scale goes up to 50 ohms. Hardly ideal for viewing the impedance curve.

I doubt it was done to be deliberately misleading.
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Old 14th June 2006, 10:28 PM   #5
lndm is offline lndm  Australia
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There are phase differences caused by the tweeters rolloff that you need to incorporate into a design. (Crossing close above fs and) reducing your crossovers slope at fs can fix this but power handling will suffer.

You want the slope to be smooth below the crossover frequency for an octave or two as well as above. Once you get down to below 2kHz, this becomes impractical.
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Old 15th June 2006, 05:32 AM   #6
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Thanks for the helpful comments. My other question is, why aren't DIY'ers concerned with fs in a full-range single driver system like they are with a multi-way system? With full range, a 20-20,000 Hz signal is sent to a single crossoverless driver whose fs lies within the signal band. Does that produce any problems?
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Old 15th June 2006, 06:12 AM   #7
lndm is offline lndm  Australia
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Woofers are designed to take excursions, a woofers rolloff is not in the sensitive region the way a tweeters is, we don't need to cross them over, we don't need to match their lower rolloff to another driver.

Even still, DIY'ers are concerned with this. I for one am yet to find the perfect enclosure
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