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Old 3rd June 2011, 10:48 PM   #21
gootee is offline gootee  United States
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More about using foil air core, related to a link above about Magnepan's recommendation:

The question should read - MikeCh - Planar Speaker Asylum
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Old 3rd June 2011, 11:32 PM   #22
andyr is offline andyr  Australia
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Quote:
Originally Posted by gootee View Post
More about using foil air core, related to a link above about Magnepan's recommendation:

The question should read - MikeCh - Planar Speaker Asylum
Very interesting post (thanks, Tom) - I agree with everything he says!

Can I suggest it's a waste of time to just replace the caps, and not the coils as well. IMO, replacing the caps gives you top end beauty ... installing 12g ribbon coils gives you better bass. One without the other will not be satisfying - you'll soon decide to bite the bullet and do the other half!

Now the stock MG-12 is 2nd order on the bass & 1st order on the treble. If you wanted to save 1 component (the 50uF cap in the bass filter), to make the new XO a bit cheaper (so you can afford a good 12g ribbon coil! ), you could use Peter Gunn's (on the Planar Asylum) 6dB series XO - I'm sure he will send you the schematic.

Good luck with the mod,

Andy
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Old 4th June 2011, 12:01 AM   #23
a.wayne is offline a.wayne  United States
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The odd order x over is a necessity imo ....
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Old 4th June 2011, 12:07 AM   #24
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Tom ,

I have Peter Gunn's MG12 crossover and will sent ii to you. OK?

Best,

Wayne
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Old 4th June 2011, 12:33 AM   #25
andyr is offline andyr  Australia
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Quote:
Originally Posted by a.wayne View Post
The odd order x over is a necessity imo ....
I'd be interested to know why you think that ... given Magnepan has used all-6dB XOs in their latest models, the 1.7 & 3.7.

Regards,

Andy
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Old 4th June 2011, 12:38 AM   #26
gootee is offline gootee  United States
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Quote:
Originally Posted by waynebosz View Post
Tom ,

I have Peter Gunn's MG12 crossover and will sent ii to you. OK?

Best,

Wayne
Thanks for the offer, Wayne, but he sent it to me already!
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Old 4th June 2011, 12:43 AM   #27
gootee is offline gootee  United States
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Quote:
Originally Posted by andyr View Post
Very interesting post (thanks, Tom) - I agree with everything he says!

Can I suggest it's a waste of time to just replace the caps, and not the coils as well. IMO, replacing the caps gives you top end beauty ... installing 12g ribbon coils gives you better bass. One without the other will not be satisfying - you'll soon decide to bite the bullet and do the other half!

Now the stock MG-12 is 2nd order on the bass & 1st order on the treble. If you wanted to save 1 component (the 50uF cap in the bass filter), to make the new XO a bit cheaper (so you can afford a good 12g ribbon coil! ), you could use Peter Gunn's (on the Planar Asylum) 6dB series XO - I'm sure he will send you the schematic.

Good luck with the mod,

Andy
Thanks, Andy, but I didn't mean that I would NEVER do the coils. I do plan on replacing them, too. I was actually just expressing my frustration with the three different "out of stock" situations for the steel core coils.

After doing some more reading I think I'll bite the bullet and order some lower-DCR foil air cores. But first I want to measure the actual DCR of the stock MG12 coils, because it looks like I want to make sure to replace them with coils that have a somewhat-lower DCR than the original ones have.

Tom
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Old 4th June 2011, 07:22 PM   #28
Davey is offline Davey  United States
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Quote:
Originally Posted by andyr View Post
I'd be interested to know why you think that ... given Magnepan has used all-6dB XOs in their latest models, the 1.7 & 3.7.

Regards,

Andy
A 6db crossover is an odd (1st) order crossover, is it not?

Dave.
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Old 4th June 2011, 10:51 PM   #29
andyr is offline andyr  Australia
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Quote:
Originally Posted by Davey View Post
A 6db crossover is an odd (1st) order crossover, is it not?

Dave.
You know that very well, Dave.

And so ...?

Regards,

Andy
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Old 5th June 2011, 11:23 PM   #30
gootee is offline gootee  United States
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I finally realized, after looking at the MG12 crossover schematic again, that I could measure the apoproximate DCR (DC Resistance) of the stock inductor/coil without removing it from the circuit, just by disconnecting the speaker from the amplifier and removing the tweeter jumper.

I already had the sock off of one of my MG-12/QR speakers. So I was able to measure the resistance between a) the junction where the coil's wire and the 50 uF electrolytic capacitor's lead are both soldered and b) the junction where the coil's other wire and the black lead from the "negative" speaker input are both soldered.

I did also remember to short the Tektronix DMM916 multimeter's leads together, before and after, and subtract the non-zero displayed value from the resistance displayed during the measurement. And I repeated the measurement several times.

The measured coil resistance was 0.36 Ohms.

Cheers,

Tom
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