Series mid capacitor: how important? - diyAudio
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Old 9th October 2012, 03:12 PM   #1
zmyrna is offline zmyrna  United Kingdom
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Location: London
Default Series mid capacitor: how important?

I am working on a 3 way OB crossover and will be ordering some capacitors for the mid driver.
I was thinking Intertechnik/Elko electrolytics should be fine in parallel.
However I have been reading confusing views on the effects of series capacitors.

Lukasz Fikus (Lukasz Fikus Lampizator) says:
"In 99 % of cases a 100 uF MKP cap works great. Any non-electrolytic is good. There are for example good MKP caps for passive power compensation in home appliances. If I listen to a programme via such cap and without (material is vocal without bass content) I hear absolutely no sound degradation due to this cap. It is transparent to the midrange content. I cant detect when this cap is shorted in bypass. It is completely transparent. DONT EVER SPEND $$$ on the exotic caps here !! Please !"

Troels Gravesen says:
"There is one serious issue here: The quality of the 88 uF to the midrange. Initially I ran 82 uF* standard polyprop caps bypassed by 1 uF Superior Z-cap. After several hours of listening I pooled all my Superior Z-caps to make 84 uF and replaced the standard caps. Sorry to say, it's night and day. Any standard polyprop sounds compressed compared to the Superior Z combo. Eight times 22 uF quality caps don't come for nothing, but once we've heard the super caps vs. standard polyprops, it's very clear there's no free lunch here." (that is over $600 worth of caps btw)

What do you think? Does bypassing a large electrolytic by a small polypropylene help? Is it recommended?
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Old 9th October 2012, 03:48 PM   #2
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I use film types in series with mids in a 3-way. Also, when recapping, I replace NPE's with film type whenever possible.
What value series mid cap do you have?

Just remember, Troels is a cost-no-object DIY'r in most cases. He uses high quality drivers and makes VERY high quality cabinetry - both which justify spending the $$ on maximizing the sonic quality of his projects; at least to his ears.
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Last edited by speakerdoctor; 9th October 2012 at 03:55 PM.
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Old 9th October 2012, 03:49 PM   #3
tvrgeek is offline tvrgeek  United States
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My experience: Any poly sounds better than any electro. I can't say that in a crossover a poly bypassing the electro makes as big a difference as it does in a low level active stage. Poly-pro meats mylar, but not as much as the jump from the electro. Would $600 worth of caps sound better than better drivers? Better than a finer tuned crossover? The only true answer is "it's your ears."

What do I use? Basic Dayton's
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Old 9th October 2012, 06:33 PM   #4
xjr100 is offline xjr100  Europe
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Quote:
Originally Posted by zmyrna View Post
I am working on a 3 way OB crossover and will be ordering some capacitors for the mid driver.
I was thinking Intertechnik/Elko electrolytics should be fine in parallel.
However I have been reading confusing views on the effects of series capacitors.

What do you think? Does bypassing a large electrolytic by a small polypropylene help? Is it recommended?
It depends on what kind of drivers you use and what is the construction and response of speaker.
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Old 10th October 2012, 01:42 AM   #5
Bare is offline Bare  Canada
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Ditto on above.. Electros Do need replacing.
But I've heard darned little (if any?) differences in Cap quality beyond decent poly film types in a passive Crossover.
Regardless of what I had to pay for the Audio Weenie approved types.
But it's your $$ and your dreams.
Ideally, long experience engenders wisdom .. sometimes :_)
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Old 10th October 2012, 10:08 AM   #6
zmyrna is offline zmyrna  United Kingdom
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Drivers are all vintage Seas alnicos from early 1970s.
Midrange is a high eff. 8" papercone: Seas 21 TV-GW
I was initially thinking a 1st order filter on both ends of the midranger.
Bass and tweeter will be 2nd order.
This is what lampizator uses in his open baffle designs.
With the natural roll-off of the midrange driver, 1st order filter behaves 2nd order sonically.
So at a minimum, I should be using the entry level PP caps from Jantzen (Cross Cap).
I can save some money by moving to a 2nd order on the mids too.
This would reduce the series cap from 100 to about 40.
But then I need a coil in parallel.
So what do you think about the parallel coil in the midrange? Air or aronite cored?
JANTZEN-1781 - Jantzen Wire air coil 10,000mH 4,230Ohm 0,70mm - Europe Audio
JANTZEN-5310 - Jantzen Wire non-ferrite cored coil 10,000mH 1,290Ohm 0,70mm - Europe Audio
Does the solid core introduce any ill effects when used in parallel?
Does the DCR of the coil effect the efficiency of the driver when used in parallel?
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