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 Post subject: EPI 70C x-over upgrade
PostPosted: Fri Oct 13, 2017 11:53 am 
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Location: Toronto, ON, CA
Recently picked-up a pair of EPI 70C's from the original owner in 9.5/10 condition except for the woofer surrounds which will soon be replaced.

From the website <<www.humanspeakers.com>> I see that the x-over is simply a 5-ohm resistor and 10uF capacitor in series with the tweeter...

So question is what is appropriate as an upgrade for both components as I understand the originals were cheap/low-quality?

Also, what is relevance of the VDC rating on a 10uF cap' with respect to use in a x-over? Is a higher rating better, or...?

Thanks to all respondents.


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PostPosted: Fri Oct 13, 2017 1:15 pm 
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I believe Solen has 250V caps that should work well. Voltage rating has nothing to do with quality.


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PostPosted: Fri Oct 13, 2017 2:14 pm 
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VDC of 70 and above is good for what you want. Don't forget as you go up in VDC, the cap will also be bigger, so 250VDC should really be the top you want to look at. As mentioned above, VDC does not equal quality.

Keep the same resistor, and if you want to replace the cap, electrolytic is good enough. If you want film cap (polypropylene) it will be more expensive, and will not be better overall (sound quality), although it will last longer than the electrolytic. Electrolytic are good for 20 years +

Here's a few you might want to look at...

Electrolytic

Elna
10uf 100VDC +/-10% size is: 8mmD X 11.5mmL Price around 1.85$ CDN each

Mundorf
10uf 70VDC +/-5% size: ? Price: 3.00$

Film Caps

Axon Polypropylene
They don't come in 10uf size but you can have these sizes mounted in parralel.
2.4uf 250VDC +/-5% Size: 13.9mmD X 25mmL 1.75$ each
7.5uf 250VDC +/-5% Size: 20.2mmD X 33mmL 2.60$

Clarity PX series
10uf 250VDC +/-5% Size: 36mmD X 26mmL 9.80$

Multicap (Metalysed)
10uf 200VDC +/- 10% Size: 1.0"w X 1.2"h X 2.1"l Price: 32.00$

Mundorf MKP series
10uf 250VDC +/-5% size: 24mmD X 33mmL 9.20$

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PostPosted: Fri Oct 13, 2017 2:40 pm 
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Thanks larrym... Parts Connexion has Solen 10uF 400v (vs. 250V) caps at US5.21 each so that's an immediate option.

Thanks moinau... But where did you get pricing for these various caps so I can look into ordering online?

-- 13 Oct 2017 22:42 --

Also, what are your thoughts on the relevance to sound-quality of adding a small-value (like 0.1uF) parallel/bypass cap?


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PostPosted: Fri Oct 13, 2017 3:27 pm 
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I rebuilt my Technics SB6000a crossovers using good electrolytic caps and bypassed them with Mundorf MKP1837s and they were some of the best speakers i owned, and regret selling them. I feel that the cost of a small bypass is worth trying and can garner good results when used with a decent electrolytic cap. Whether or not the bypass cap was the cause, for the $7 per speaker, it was a no brainer to try. Would do it again.

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PostPosted: Fri Oct 13, 2017 4:25 pm 
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Thanks mortron, but I cannot find a reference/pricing to Mundorf MKP1837 caps, only Vishay MKP1837 and they seem to be 1uF whereas my understanding (ignorance?) is typically bypass caps are 0.1uF. Looking forward to learning more! Thanks.


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PostPosted: Fri Oct 13, 2017 8:31 pm 
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AuralXTC wrote:
Thanks larrym... Parts Connexion has Solen 10uF 400v (vs. 250V) caps at US5.21 each so that's an immediate option.

Thanks moinau... But where did you get pricing for these various caps so I can look into ordering online?

-- 13 Oct 2017 22:42 --

Also, what are your thoughts on the relevance to sound-quality of adding a small-value (like 0.1uF) parallel/bypass cap?


The reference are from Parts Connexion. I just converted the US currency in CDN currency.

As for bypassing using a small value film cap while using electrolytic main caps, I don't find any difference in sound quality, and this is not to say that other people are wrong when they do so. You can try it if you want in one of the speaker while leaving the other without it. If you find a difference, do the other one, if not, nothing loss.

If you want to try this approach, I found a few reasonably priced, although with a high of 630/650VDC size might a factor.

CLARITY-75927 SA Series
0.1µF / 630VDC, +/-5% Size: 30mm D x 20mm L,
5.46$US, 6.75$CDN

MUNDORF-70600 M-Cap ZN
0.1µF / 630V, +/-3% Size: 10mm W x 32mm L, Each
$9.59USD 11.85$CDN

MUNDORF-70358 MKP Series
0.1µF / 630V, +/-3% Size:10mm W x 19mm L, Each
$3.90 USD 4.80$CDN

MUNDORF-76385 EVO Series
0.1µF / 650V, +/-3% Size: 18mm W x 12mm L, Each
$3.59USD 4.45$CDN


You might find a difference using this approach in an amp or pre-amp.

If using 400VDC main type capacitors, just make sure they will fit on the board. As I mentioned earlier, the higher the voltage, the bigger the caps, and the more expensive they become.

You will not gain anything with a 400VDC versus, 70, 100, 200, or 250VDC.

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PostPosted: Tue Oct 17, 2017 7:49 am 
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Location: Toronto, ON, CA
Thanks you all for your responses.

Update is that I have ordered 10uf 250v Clarity film caps from Parts Connexion.

Now looking at upgrading to Cardas pure copper binding posts -- even though they cost almost as much as the speakers did!

Will also upgrade the internal wiring from looks like 24g to something a like 18g Litz.

Any thoughts on replacing/upgrading the fiberglass internal damping?

Your comments and input are appreciated!


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