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Multi-Way Conventional loudspeakers with crossovers

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Old 21st November 2007, 04:42 AM   #2721
CLS is offline CLS  Taiwan
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Is this the one?

http://db.audioasylum.com/cgi/m.mpl?...nequest&n=5167
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Old 21st November 2007, 05:24 AM   #2722
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Quote:
Originally posted by CLS
Is this the one?

http://db.audioasylum.com/cgi/m.mpl?...nequest&n=5167
It was the one I enquired about, but no schematic.
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Old 21st November 2007, 06:17 AM   #2723
CLS is offline CLS  Taiwan
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Isn't this?

Click the image to open in full size.
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Old 21st November 2007, 05:43 PM   #2724
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Quote:
Originally posted by john k...


This is incorrect. The damping is controled by the reverse current generated by the back EMF of the drivers. The reverse current is given by Ib = Vback/(Re + Rg) where Rg is the amplifier's output (Ro)imepdance and any other series impedance. When connected in series Rg = Ro + Rg of the second driver so Ib = Vback/(2Re + Ro). At first glance this looks bad but then you must considet that for two driver in series Vback also doubles. So Ib = 2Vback/(2Rg + Ro) . If Ro is small Qts will not change significantly. If the amp's output impedance is high the series connection will actually move Qts back towards the short circuited voice coil value.

The problem with series connections is that unless both driver are identical the back EMF of one driver can modulate the second driver and vice versa. There is also the problem of nonlinear distortion from on driver modulating the other as well. Series connections can be problematic in this regard.
Sorry,, I have to fix this. Too many typos.


"When connected in series Rg = Ro + Rg of the second driver..."

should have been, "When connected in series Rg = Ro + Re of the second driver..."

(where Re = voice coil resistance).

Also,

"So Ib = 2Vback/(2Rg + Ro) ."

should have been: "So Ib = 2Vback/(2Re + Ro) .
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Old 21st November 2007, 06:34 PM   #2725
mige0 is offline mige0  Austria
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Hi

Quote:
Originally posted by john k...


This is incorrect. The damping is controled by the reverse current generated by the back EMF of the drivers. The reverse current is given by Ib = Vback/(Re + Rg) where Rg is the amplifier's output (Ro)imepdance and any other series impedance. When connected in series Rg = Ro + Rg of the second driver so Ib = Vback/(2Re + Ro). At first glance this looks bad but then you must considet that for two driver in series Vback also doubles. So Ib = 2Vback/(2Rg + Ro) . If Ro is small Qts will not change significantly. If the amp's output impedance is high the series connection will actually move Qts back towards the short circuited voice coil value.

The problem with series connections is that unless both driver are identical the back EMF of one driver can modulate the second driver and vice versa. There is also the problem of nonlinear distortion from on driver modulating the other as well. Series connections can be problematic in this regard.

JohnK, thanks for your correction and for illuminating the background.

Greetings
Michael
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Old 21st November 2007, 07:12 PM   #2726
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Default Re: John Swenson transconductance amp

Quote:
Originally posted by mikey_audiogeek
Hi Brett, sorry can't help, you could ping John on the Magnequest forum and get him to repost. Otherwise the post in the attached link gives all the info, and Gary's webpages are back online.

Cheers,
Mike

John Swenson transconductance amp post
I generally think that JS is one of the smarter guys around, so I frequently save schematics and such that he posts. I believe he has significatly revisited the PS for the amp, but to the best of my knowledge the Signal section is unchanged.

Regards,
John
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Old 22nd November 2007, 05:28 PM   #2727
dobias is offline dobias  United States
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Default Volume

John K,
Re: Your post #2721
(Since I can't think of a more intelligent way of asking)
At the same volume setting, will series connected speakers have the same SPL as parallel connected speakers?
dobias
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Old 22nd November 2007, 08:48 PM   #2728
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http://www.linkwitzlab.com/faq.htm

Q-21, gives a decent explanation.

Cheers .......... Graham.
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Old 22nd November 2007, 10:09 PM   #2729
dobias is offline dobias  United States
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Default Series-Parallel

Graham,
If I read that explanation correctly, the volume control would need to be increased to maintain the SPL of series connected speakers to that of parallel connected speakers.
But then, I could be misinterpreting it.
dobias
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Old 23rd November 2007, 02:08 AM   #2730
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No. At the same volume setting the parallel connection will be 6dB louder than a singel driver. With a series connection the SPL will be at the same level as a single driver. This is because the voltage across each driver with be reduced to 1/2 the total. But recognize that with the parallel connection the total power into both driver will be twice that of the single driver. With the series connection the total power will be 1/2 that into a single driver.

Again, these differences are the differences between voltage sensitivity and efficiency. The parallel connection yields a +6dB increase in voltage sensitivity while the series connection yield the same voltage sensitivity as a single driver. But both configurations result is a 3dB increase in efficiency.
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