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Multi-Way Conventional loudspeakers with crossovers

Help crossover Boston A20
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Old 12th September 2019, 11:14 AM   #1
moldwine is offline moldwine  Argentina
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Default Help crossover Boston A20

Hi,

I bought this Bostons A20 and the sound pretty good, but i want them to upgrade the caps...as the speakers looks like they are from the 80 i think (couldnt find any info online)

Im not really sure what to get, Any recomendations for caps? They are betwen 20-100 mfd bipolar 50 vw

Would make any difference to get a more high end cap for this crossover/speaker?

Cheers!
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Old 13th September 2019, 05:52 AM   #2
eriksquires is offline eriksquires  United States
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If you want inexpensive, smooth, dark, Mundorf MKPs are something you can try. Let them break in for 2-4 days of playing.



Clarity CSA after that.



I would do them in ascending order. That usually means, the tweeter, then the mid, and finally anything on the woofer portion.



Keep your prices small, and treat this like a learning experience and this way you'll have fun and start to figure out what you are doing.



You may want to get XSim to help you draw out your crossover before you begin.


Best,


E
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Old 16th September 2019, 11:59 AM   #3
moldwine is offline moldwine  Argentina
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Thanks for the reply,

You think i can change the old cap 20 mfd 50WV,

with a Z cap 22 uF 400 Vdc?

Or is that a lot of difference?

Thanks
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Old 16th September 2019, 11:04 PM   #4
Galu is offline Galu  Scotland
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Quote:
Originally Posted by moldwine View Post
Or is that a lot of difference?
The difference is in the order of 10% which may be just outside the bounds of acceptability.

Instead, you could connect two 10uF Z caps in parallel to achieve the exact value of 20uF.

http://www.jantzen-audio.com/wp-cont...rior-Z-Cap.pdf
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Old 17th September 2019, 07:26 AM   #5
Lojzek is offline Lojzek  Croatia
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moldwine,

why don't you invest some time and funds in a measurement rig so you can actually learn something instead of mindless parts exchanging?
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Old 17th September 2019, 02:43 PM   #6
adason is offline adason  United States
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Quote:
Originally Posted by Lojzek View Post
moldwine,

why don't you invest some time and funds in a measurement rig so you can actually learn something instead of mindless parts exchanging?
great advice!
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Old 17th September 2019, 03:31 PM   #7
chrisng is offline chrisng  United States
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Great advise from Lojzek!


OTOH, the bi-polar electrolytic capacitors are close to 40 years old, maybe it's time for re-cap.
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Old 17th September 2019, 08:55 PM   #8
6A3sUMMER is offline 6A3sUMMER  United States
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A picture is worth 1000 words.
Look again.
I believe the 2 left most caps, and the 1 right most cap are Bipolar.
I believe the 2 middle caps are Not Bipolar.

But I do notice another possible issue.
The largest inductor has an Iron or Steel Core.
I would consider replacing it with an Air Core inductor (it will be Much larger, and will need to have Much larger wire). That way you can get the same inductance, and the same DCR.

I am not opposed to keeping the original inductor . . .
But I would like some others to give there comments about non-air core inductors.
They are generally for woofers, and so they have the largest signal currents.
I think the only thing that reduces the harmonic distortion of non-air core inductors is the low pass capacitor that is connected across the woofer (but the attenuation of those harmonics is not a sharp cut off).
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Old 17th September 2019, 08:55 PM   #9
6A3sUMMER is offline 6A3sUMMER  United States
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Join Date: Jun 2016
A picture is worth 1000 words.
Look again.
I believe the 2 left most caps, and the 1 right most cap are Bipolar.
I believe the 2 middle caps are Not Bipolar.

But I do notice another possible issue.
The largest inductor has an Iron or Steel Core.
I would consider replacing it with an Air Core inductor (it will be Much larger, and will need to have Much larger wire). That way you can get the same inductance, and the same DCR.

I am not opposed to keeping the original inductor . . .
But I would like some others to give their comments about non-air core inductors.
They are generally for woofers, and so they have the largest signal currents.
I think the only thing that reduces the harmonic distortion of non-air core inductors is the low pass capacitor that is connected across the woofer (but the attenuation of those harmonics is not a sharp cut off).
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Old 17th September 2019, 09:25 PM   #10
Galu is offline Galu  Scotland
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Quote:
Originally Posted by 6A3sUMMER View Post
I believe the 2 left most caps, and the 1 right most cap are Bipolar.
I believe the 2 middle caps are Not Bipolar.
I think you mean that the 2 left most caps, and the 1 right hand cap appear to be NP electrolytic types.

The 2 middle caps would appear to be NP film types.

Normally, it is only worth changing old, out of spec, electrolytic capacitors for new ones. Film caps do not age and can be left alone.

P.S. The steel or ferrite cored inductor is OK for low bass duties where a small amount of distortion is tolerable.

Last edited by Galu; 17th September 2019 at 09:31 PM.
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