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Multi-Way Conventional loudspeakers with crossovers

improvements parallel cap construction for crossover network
improvements parallel cap construction for crossover network
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Old 13th November 2017, 12:24 PM   #11
Kay Pirinha is offline Kay Pirinha  Germany
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In my opinion the only reason for paralleling capacitors is if you need a certain value that you don't have, instead decide to replace them by capacitors that are laying around somewhere in your stashes. I did this in order to replace the 25 µF bipolar electrolytics that I've found in my 1970ies Wega speakers by a combination of 15 µF + 4µ7 + 4µ7 foil capacitors. I've shown pictures here: Restoration
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Old 13th November 2017, 03:50 PM   #12
eriksquires is offline eriksquires  United States
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You can get measurably lower ESR by paralleling a cap, as well as inductance.

However, most film caps have really really low ESR to begin with. The days when low ESR was considered more transparent are long gone, but it does contribute to the crossover balance.

My advice to anyone playing around with bypass caps: Try an Audyn True Copper cap in the 0.1uF range. I have found it helps warm up larger caps ( > 5uF) and they're not unreasonably priced.

Best,

E
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Old 13th November 2017, 09:54 PM   #13
georgehifi is offline georgehifi  Australia
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I've always found that using high quality bypass caps across larger medium/low quality larger caps works a treat so long as they are not in series with the signal.

With caps that are in series with the signal, I found just one cap of the highest quality you can use is the best way to go, any bypass caps on these seem to smear the sound at frequencies where the two overlap.

Cheers George
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Old 13th November 2017, 10:04 PM   #14
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by georgehifi View Post
any bypass caps on these seem to smear the sound at frequencies where the two overlap.
How do you mean "overlap"?
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Old 13th November 2017, 10:23 PM   #15
wolf_teeth is offline wolf_teeth  United States
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I've heard this too, but have not used a measurement method that shows the difference yet. I don't know how to test for it, even though someone said an impulse would show it, it did not, and the sound was very obvious.
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Old 13th November 2017, 11:10 PM   #16
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by scottjoplin View Post
How do you mean "overlap"?
Where the smaller "bypass" one starts to roll off and the bigger main one is still doing it's job.

Cheers George
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Old 13th November 2017, 11:15 PM   #17
scottjoplin is offline scottjoplin  Wales
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Two capacitors in parallel don't work like that, or am I misunderstanding? You mean two filters?
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Old 13th November 2017, 11:30 PM   #18
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by scottjoplin View Post
Two capacitors in parallel don't work like that, or am I misunderstanding? You mean two filters?
I talking about series caps, or coupling caps that have the audio signal going through them.

A series bypass signal cap (coupling) which is too small by itself may LF roll off at say 2khz, the main cap that it's bypassing will go down to below 20hz and go above to over 20khz.
The over lap of two caps with totally different construction and sounds qualities will be overlapped from 2khz to 20khz, giving two different characteristics which to me smear the sound rather than making it better. As I said best to use one very high quality cap in these series (coupling) positions.

Cheers George
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Last edited by georgehifi; 13th November 2017 at 11:33 PM.
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Old 13th November 2017, 11:44 PM   #19
Conrad Hoffman is offline Conrad Hoffman  United States
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There's nothing wrong with paralleling caps, and at very high frequencies there are some benefits. By very high I don't mean audio frequencies. Those benefits happen more when bypassing high speed logic and wide bandwidth opamps.

There's also no benefit in dissipation factor (or esr). Why? Let's say the target is 3 uF. Imagine a 3 uF cap stretched out as a big square of dielectric with metallization on both sides. The losses, DF or esr as you please, are whatever they are. Now, get out your scissors and cut the cap in half. Each half now measures 1.5 uF because it's half the area. The DF remains unchanged because it's a ratio with capacitance. The esr, however, doubles because it's not a ratio but an absolute number. IMO, a good reason not to use esr unless you're a switching supply designer, but I digress.

So, you've got these two 1.5 uF sheet capacitors. You get two pieces of wire and connect the top and bottom electrodes of the caps together. You've paralleled them, more or less the same as before you cut them in half. You now have the original 3 uF, with the same DF and esr you started with.

The lesson is if you use the same materials, say Mylar or polypropylene, there's little gain or penalty for paralleling capacitors.

Thing get more complicated if one capacitor is of poorer quality than the other, but we try not to use poor quality capacitors! Hint- it's impossible to improve a poor quality capacitor (by that I mean high losses, DF or esr, as you please) by putting some smaller capacitor in parallel with it, so if you want good, use a single good cap, as has been said. No penalty for using a couple good caps, if you need to hit a value.
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Last edited by Conrad Hoffman; 13th November 2017 at 11:48 PM.
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Old 14th November 2017, 12:03 AM   #20
georgehifi is offline georgehifi  Australia
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That's fine if the series bypass cap is so small (pf) that it's only bypassing above the audio band, then it's doing nothing to the sound.

A 10uf "mid" quality series coupling cap looking at a load of 10kohm has a LF frequency response of -3db at 1.5hz to 100's of khz.

A typical high quality bypass cap say .1uf has a frequency response into that same 10kom load of -3db at 160hz to 100's of khz.

The over lap of the two very different caps from 160hz up can be a problem because they are both working at those frequencies both with totally different characteristics.

Best to use one only, very good quality 10uf cap in the first place, and forget about the bypass cap.

Cheers George
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Last edited by georgehifi; 14th November 2017 at 12:14 AM.
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