Acoustic Zen Crescendo speaker crossover capacitors ... who makes them?

Granny,

Why not bias the electrolytic caps in the woofer cross over all you need it two  (4 for the set) more 1000uF capacitors which Madisound sells,  put them in series with the existing capacitors then bias the mid point with a number of 9V batteries in series, four should probably do for 36V. Positive goes to the midpoint via a 1M Ohm resistor negative goes to ground.  JBL use this technique in their flagship speakers 

Alternatively buy 40 100uF metabolized polypropylene capacitors - with that quantity you should be able to get a discount :-) 


Best of luck


Peter

Granny,

Yes I ave used this technique and it defiantly improves the SQ of a Bipolar Electrolytic Capacitor.   All capacitors in a Speaker Crossover should be Bipolar as this is an AC circuit.   If you google this there are many diagrams on how to connect the circuit, and you are describing it correctly,  you must however use a separate feed from the battery to each set of capacitors - luckily 1M Ohm resistors are very inexpensive.

One small correction to above post - since you are connecting the capacitors in series each should have a value of 2000uF, a series connection of capacitors results in half the value of each - i.e 2000uF in series with 2000uF = 1000uF

https://www.google.com/patents/US7443990

Best of luck

Peter  

Mapman and Granny,

The type of capacitor used depends on where in the crossover it is used, in some cases the only reasonable solution is to use a Electrolytic capacitor.

http://pbnaudio.com/speakers/speaker-kits/scanspeak-b741

Use the above speaker design as an example, in the bandpass for the midrange driver there are two series capacitors and two shunt capacitors, the two series capacitors certainly in a speaker this quality needs to be metalized poly propylene 100uF is a standard value and the 180uF is made up by paralleling 2 each 90uF capacitors, the two shunt capacitors both are 27uF, since this is a relatively small size it only makes sense to use polypropylene here too and luckily 27uF is a standard size too with a pretty tight tolerance too as compared to an Electrolytic capacitor. Now for the Impedance correction network in parallel with the midrange driver, here a 820 uF capacitor is needed - the only reasonable choice is an electrolytic capacitor, in this case to get the 820uF, 320uF uF is paralleled with 500uF and then I typically use a small value polypropylene to bypass with, something like 3uF

Good Listening


Peter

Looking at your schematic, you have a impedance correction network across the positive and negative, not knowing the value of he inductor is impossible to tell, you where it corrects, you could disconnect it measure the impedance and see where you get a raise in the impedance.  Changing the caps or bias them in this circuit will not do much to SQ but you could certainly try.

The woofers are connected to a standard 18dB/Oct electrical filter consisting of two coils in series and a 200uF capacitor as a shunt via a 12 Ohm resistor between them, pretty standard stuff. However parts seems to be a extraordinarily high quality. 

Best

Peter