Dipole woofer how high

[johnb]

I might build a pair of dipole subs to complement a pair of Fostex Fe207 in small cabinets. My question is how high is it recomendable for a pair of dipole subs to work. Will they for example work up to 150 hz.
This might be a very dumb question as there are many variations on dipole subs and drivers used. But I got the impression that dipoles dont like to go over 100hz or am I completley wrong?

[ScottG]

Originally posted by johnb
I might build a pair of dipole subs to complement a pair of Fostex Fe207 in small cabinets. My question is how high is it recomendable for a pair of dipole subs to work. Will they for example work up to 150 hz.
This might be a very dumb question as there are many variations on dipole subs and drivers used. But I got the impression that dipoles dont like to go over 100hz or am I completley wrong?

This depends on the driver you are using and the baffle. Dipole operation is actually best utilized from around 300 Hz down to as much as 40 Hz (typically 300 or 250 to 65 or 60 is excellent) - with a baffle that does NOT present a resonance problem in this region..

In otherwords this is NOT a subwoofer. For a real subwoofer look at other designs with a focus on low distortion at low freq.s and an extension down to 18 Hz or more (..I'm partial to about 13 Hz).

[reins]

Originally posted by johnb
I might build a pair of dipole subs to complement a pair of Fostex Fe207 in small cabinets. My question is how high is it recomendable for a pair of dipole subs to work. Will they for example work up to 150 hz.
This might be a very dumb question as there are many variations on dipole subs and drivers used. But I got the impression that dipoles dont like to go over 100hz or am I completley wrong?

The upper crossover frequence of a dipole woofer depends on the quality of the driver for that region and on placement issues. For higher crossover, the midrange and the woofer have to be placed near each other. In the sub area it is mainly a question of volume displacement capabilities of the woofers. People utilizing many 15" woofers to get that. But again then you might get a problem with placement of woofers and midrange.

stephan

[Rudolf]

Johnb,

the upper limit of a dipole is usually determined by the cavity resonance of the cabinet.
So for a driver in an OB there is no upper limit. Just the performance of the driver itself.

For a H-frame the resonance frequency is typically about twice that of a W-frame built for the same size driver.
I just built a W-frame for a 15" driver and got the resonance peak at 220 Hz. So 150 Hz xover would be a bit too high for that. Any smaller driver (12" or 10") or a H-frame should work nicely up to 150 Hz.

I assume in every case that you equalize the resonance peak sufficiently and that the xover is at least 18 dB/oct.
My H-frames with 10" drivers work that way smoothly up to 250 Hz.

Rudolf