zobel networks and imoedence reduction?

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Nanook

Nanook

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Joined 2004
#1
It seems to me that the bass output of full range drivers is seriously affected by the rising impedence as the driver reaches fs.

What can be done to reduce this rising impedence? A Zobel? Will this increase the output at or near fs? Has this been used in horns or other single driver, high efficiency speakers?

What are the other alternatives?

Any and all help appreciated as always.

stew
 
#2
A "Zobel" will not generally increase the bass coming out of a
speaker. A current source or other high impedance amplifier
will increase the bottom end - if that's what you're looking for,
and in that case a resistor can be used to trim the damping of
the system.

Check out the article on www.firstwatt.com
 
#3
Assuming it's really a problem for the amp, the hard road is to add a tuned series LCR string in parallel with the woofer to flatten the peak. This is probably practical only for a driver/cabinet system with a single impedance rise. The double hump impedance curve of a bass relflex would make for some challenging optimization.
However, there's a much easier way to determine if it's worth pursuing: parallel the woofer with a resistor. 100 ohms in // will drop 8 ohms to 7.5 (miniscule) and a 50 ohm rise to 33 ohms (significant). Or, for full effect, test it using 12-15 ohms, which will drop the typical ~6 ohm mid-band impedance of a full range to 4 ohms and give it a whirl on the 4 ohm secondary taps. From the results decide if the full meal deal's worth the trouble.
 
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