Non polarized Caps

[Ilianh]

well the thing is a 200 uF NP cap is around 10$, a polarized 400uF one is around 50 cents (even less) here.

for a 5 speakers system where you use second or third order Xo's... that might save you a nice 80$ or so, wich btw is alot of money...
considering I could make a whole subwoofer with that money.

[fdegrove]

Hi,

Not that I want to discourage you from running experiments but IME it does not yield good results in a X-over.

Also I'm surprised at the cost ratio between the two of 1:10 which may hold true for a 200 mF but for smaller values?

Re:

Any ideas on this one?

In a X-over these diodes aren't going to do anything useful since no DC is present.

Cheers,

[Ilianh]

In a X-over these diodes aren't going to do anything useful since no DC is present.

I use them here as half wave rectifiers... diodes are not only used where dc is present

Also I'm surprised at the cost ratio between the two of 1:10 which may hold true for a 200 mF but for smaller values?

basicly the ratio is about the same,
On a 10 uF one, wich is aorund 3$ for a NP, its aorund 5 cents for a polarized one..

Btw,

which may hold true for a 200 mF but for smaller values?

how low would you make a cut with 200mF?
200mF would make a nice 10hz highpass filter
but ouch on the price of a NP 200 mF cap..

[fdegrove]

Hi,

A bit tongue in cheek:

I use them here as half wave rectifiers... diodes are not only used where dc is present

Don't forget diodes aren't linear in behaviour.

how low would you make a cut with 200mF?

I look at what I need for a complete project and than try to figure out a way to buy n *n value and // those values where appropriate so I get a volume discount.

It may not be applicable to your project though.

Ciao,

[Bobken]

Originally posted by Ilianh
well the thing is a 200 uF NP cap is around 10$, a polarized 400uF one is around 50 cents (even less) here.

for a 5 speakers system where you use second or third order Xo's... that might save you a nice 80$ or so, wich btw is alot of money...
considering I could make a whole subwoofer with that money.

Hi,

There seems to be a huge and quite disproportionate difference in the price of these different types of caps, in your country.

Especially (as Dhaen & Frank have suggested) as the non-polar caps are (mostly) simply two polarised ones in the same can.

I say mostly, since I am not sure without looking it up whether this is precisely how the very special non-polar Black Gates are made.

I can get 200uf - 50 Volt non-polars for £1.10 each (considerably less than $2 US) in the UK, especially designed for xovers, but I would never use electrolytics in a speaker anyway.

If you wish to end up with a speaker that sounds even half decent, I would steer clear of any polarised electrolytics which merely cost a matter of a few cents, as they are most unlikely to give you a good sound, unless they are being sold at very much below cost!

You have been warned!!!!

Regards,

[Ilianh]

Ive been checking all day, and the cheapest NP 200 uF cap I found was 6$ cdn.

not that bad...
anyone knows how much they cost at solen? its kindof near where I live

[Nelson Pass]

Originally posted by Bobken
Almost all, if not all, polarised caps appear to perform their function better when they have a distinct 'bias', or DC voltage differential across their two leads.

If you have connected the caps two positive leads together, you need to apply a (relatively) positive DC voltage to the junction, and similarly, If you have connected the two negatives of the caps together, apply a negative DC voltage here.

I don't necessarily agree with the thesis that bias improves
electrolytics, but for what it's worth, you can achieve a bias
by placing diodes in parallel with each cap, creating a bias
rather quickly when the amplifier drives the back-to-back
caps. You perhaps would argue that this might create some
distortion while the caps are biasing up, but playing a little
head banger music while warming your system up should
take care of that.

[vuki]

It seems that Nelson is right again - in an article recently published in british Electronics World magazine (already mentioned elswhere) distorsion figures for electrolytic caps were much better without bias. High quality film caps exhibited same performance regardless of bias. Back to back polarized electrolytics were worse than non-polar lytics, and very good results were achieved with non-polar lytics in unusuall (for this type of cap) back to back configuration.
Anyway, I wouldn't use electrolytics of any type for xover.

Vuki

[diyman]

I find that Solen do carry a reasonable wide range of film caps up to about 300uf. Their prices are "fairly decent" in hifi terms costing about $20 to $30 for a 240uf 250V polyprop. The sonic improvement over electros I feel is quite justified.
I've also tried "motor starter" caps(by Plessey) which are non polar caps rated at 110V ac and found their sound quite good too!

ckt

[Ilianh]

hehe, the crossover will cost more than the whole 3 way speaker, including drivers and materials.