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Old 19th July 2010, 06:25 AM   #1
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Default Am I crazy?

Would there be ANY advantage to adding an impedance equalizer to a TH [or any other sub] design for instance? to keep impedance peaks under control, I haven't seen them used in subwoofers
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Old 19th July 2010, 08:16 PM   #2
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I think I know why.

99% of the time, the subwoofer in a system is driven by a solid state amplifier. A decent one of those simply won't care about wierd impedance curves. So there really is no need.
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Old 19th July 2010, 10:14 PM   #3
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There's a good chance it would end up sounding worse. The thing that keeps impedance under control is the amp, or rather the damping factor, and like chris says anomalies in impedance curves are no problem to a decent amp.

I'd steer well clear.
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Old 19th July 2010, 11:40 PM   #4
soho54 is offline soho54  United States
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Originally Posted by TundraLTD View Post
Would there be ANY advantage to adding an impedance equalizer to a TH [or any other sub] design for instance? to keep impedance peaks under control, I haven't seen them used in subwoofers
Not in a horn. The horn over-rides the drivers normal loading with it's own acoustic loading.
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Old 22nd July 2010, 01:49 AM   #5
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Quote:
Originally Posted by TundraLTD View Post
Would there be ANY advantage to adding an impedance equalizer to a TH [or any other sub] design for instance? to keep impedance peaks under control, I haven't seen them used in subwoofers
What's an impedance equalizer used for? I'd be concerned not on the peaks, but the dips along with the phase angle as it determines how deeply you'll be abusing the amp. This is a good read: Stereophile: Heavy Load: How Loudspeakers Torture Amplifiers
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Old 22nd July 2010, 07:17 AM   #6
soho54 is offline soho54  United States
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What's an impedance equalizer used for?
They are used by some in passive xovers/EQ to flatten(straight line) a driver(s) impedance over a certain range to help with xover integration/overlap between drivers.
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Old 22nd July 2010, 07:42 AM   #7
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Fair enough, but you'd not need that for a subwoofer crossed over before the amplifier (the cost of crossing them post-amp would be horrific).

Chris
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Old 22nd July 2010, 07:53 PM   #8
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There's a pink elephant in this room, but no one has brought him up directly.

The performance you can achieve with a DSP based line level x-over far exceeds lossy passive components that disrupt damping factor and efficiency. Not only that, but the cost of doing it at speaker level [as chris says] might even be half the cost of a DBX DriveRackPA+ that has 1000x the control for tweaking and driver protection.

It's huge and pink!

Please don't screw-up your sub with passive x-over junk.
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Old 23rd July 2010, 03:09 AM   #9
soho54 is offline soho54  United States
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I never told him to use it. I just answered some questions.
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Old 23rd July 2010, 11:00 PM   #10
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I don't know that the original OP was intending to use passive crossovers on his sub. I hope not, since they just don't work.

I assume he was asking more "What's the use?" Presumably, the use would be to flatten the phase angle and present an easier load to the amplifier.

That is what Richard Small worked on at KEF at one point-conjugate networks to flatten the speakers' impedance and "make your amplifier more powerful" as the much-ridiculed marketing hype put it.

That assertion was probably true for many amps, especially lower priced designs. If you have some huge built-like-a-tank smartly designed amp, it may not matter.

But the missing piece of the puzzle is: do the fixed-impedance passive components really compensate well, when the driver impedance is changing with motion and self-heating due to input power?

In any case, conjugates at bass frequencies would be big and heavy and EXPENSIVE I should think, due to the large component sizes and need for high voltage handling. Probably cheaper to buy a bigger amp!
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