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Old 8th May 2009, 04:22 PM   #501
GM is offline GM  United States
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Quote:
Originally posted by fb

Is one likely to notice the back-EMF/damping issue in this case? I'm not sure how to simulate it - it's not the impedance graph in Hornresp is it? The article suggests that the issue varies between drivers and crossover implementations.


Tapped horns already do this acoustically don't they? I had assumed that audibility of this in the sub frequencies was less important....

Thanks for your assistance.
You're welcome!

Of course! It's what smooths out the TH's response and limits its HF BW. You can see its effect on the SPL, impedance, and impulse plots.

Right, true, but you asked what the deal was with inductors, so this is all part & parcel of it whether or not it's applicable to LF BW apps........

GM
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Old 9th May 2009, 09:50 AM   #502
iand is offline iand  United Kingdom
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Quote:
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Now can someone please tell me what the deal is with inductors? This box needs a roughly 5mH inductor in series.

What are the downsides to using a design with added inductance? Reduced power handling?


Would the 500WRMS Erse Inductors at Parts Express be alright for the 600W amp I plan to use?




Ta
The problem with most high-power ferrite/metal core inductors is that they're not really linear, they start to saturate at high currents.

The only sure way round this is to use big air core inductors, but these are pretty expensive for subs because you need high inductance and low series resistance to avoid power loss.

If you mean the Erse 14g air core inductors like these

http://www.parts-express.com/erse-14...-inductors.cfm

then these are very good so long as the resistance isn't too high (which depends on what value you need) -- the 12g ones are lower resistance, and are 50% off at Erse at the moment

http://www.erseaudio.com/Products/XQCoils12Gauge

Ian
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Old 9th May 2009, 06:12 PM   #503
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This is going to sound incredibly dumb, but it's something I've wondered for a long time.

If you wire two speakers in series, wouldn't the first speaker act like an inductor for *second* speaker?

I mean, a speaker has inductance right? The voice coil acts as an inductor.

Due to that, wouldn't the series inductance completely alter the thiele-small parameters for the other speaker? The inductance and series resistance should raise QTS for the other one, shouldn't it?
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Old 9th May 2009, 09:00 PM   #504
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Well, Le doubles with two drivers in series and halves if in parallel, but since you're coupling two ~identical impedances they each get ~half the voltage, so no change in Qts.

GM
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Old 9th May 2009, 09:29 PM   #505
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Default Speakers in Series

This may have the information you are looking for:

http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf

Regards,
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Old 10th May 2009, 03:07 AM   #506
JLH is offline JLH  United States
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Quote:
Originally posted by GM
Well, Le doubles with two drivers in series and halves if in parallel, but since you're coupling two ~identical impedances they each get ~half the voltage, so no change in Qts.

GM

Le does not halve when wired in parallel. It just appears as the same inductor value, but with half the DCR. You are correct that Le does double when they are wired in series.

Rgs, JLH
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Old 10th May 2009, 04:48 AM   #507
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Sorry, you can't have it both ways. You're right in that the driver's Le value doesn't change any more than its Qts, so this is true in both cases, not just in parallel, but unlike Qts, their effective values do.

Edit: "...... the effective Le doubles with two drivers in series and halves if in parallel.......".

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Old 10th May 2009, 03:05 PM   #508
JLH is offline JLH  United States
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Quote:
Originally posted by GM
Sorry, you can't have it both ways. You're right in that the driver's Le value doesn't change any more than its Qts, so this is true in both cases, not just in parallel, but unlike Qts, their effective values do.

Edit: "...... the effective Le doubles with two drivers in series and halves if in parallel.......".

GM

By definition inductance is the amount of voltage dropped across an inductor for a given rate of current change through it. Since power amplifiers are voltage sources, the voltage across each inductor remains the same for parallel inductances. The current through each inductor is the same as if were alone. The power amplifiers just supplies more current for the parallel load. Therefore, their effective inductance does not change where they are paralleled. The only times this would not be true is if the inductors share a common core; i.e. common core feedback and if you happen to own one of Nelson Pass' current source amplifiers. Since the loudspeakers donít share the same pole piece, it is impossible for the effective inductance to be less than a lone single inductor.
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Old 10th May 2009, 04:14 PM   #509
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OK, thanks, so you're saying that paralleled drivers which measure only half the ohms rise for a given frequency has the same effective inductance as a single driver?

GM
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Old 10th May 2009, 04:18 PM   #510
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Quote:
Originally posted by GM
OK, thanks, so you're saying that paralleled drivers which measure only half the ohms rise for a given frequency has the same effective inductance as a single driver?

GM
Nope, half the inductance -- also half the resistance, so the frequency response is the same.

Two drivers in series, double the resistance and inductance, same response.
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