Bypassing -- Al K, Leo, anyone

[Deang]

Ran across this statement: "Capacitors used in crossovers MUST BE NON-POLARIZED and for best sound must have low self-inductance. High-quality 100-200 volt rated, foil wound Mylar capacitors should be used and should be individually paralleled by 0.01 microfarad polypropylene or polystyrene capacitors to short out the high-frequency self-inductance of coil formed by the many layers of foil winding inside.

Does this apply to polypropylene and film and foils as well?

[tpg]

Ok, I admit I do not know as much as most here, but as for me, any xover work I do... I plan for metallized polypropylene paralleled with a plain polypropylene. But, I am a cheap DIYer... so I use Solen, Dayton, and Orange Drops.

[Al Klappenberger]

Dear,

Most of those statements are ture, but I think they are too enphatic! As to mylar caps, foie! Use Polypropylene wherever you can. They left out the most important thing though, the inductors! Use #14 wire or larger solid below about 2000 Hz and "Litz" wire above that.

Al K.

[Deang]

"Dear"

Well, it took a while -- but I can finally see I won your heart.

Certainly the use of litz wire in the HF circuit would be ideal, however, I still have concerns that driving the DCR that low with the RF-7's would upset the balance between the horn and woofers. Alpha Core doesn't sell anything smaller than 20 gauge. I did make an attempt to buy my own 23 AWG litz to roll my own inductors -- but all of the vendors that I contacted only sold in bulk. I really didn't need a skid of that stuff.

[Randy Bey]

Sweetheart,

I wasn't aware that capacitors were polarized. The physical representation is two big sheets of metal with a thin layer of something inbetween.

Some consider the outside layer (when the sheet is rolled into a cylinder) to be the negative side; something about shielding.

[leok]

Randy Bey,

Electrolytics are polarized .. I think that's the reference.

Dean,

Al's response contains most of what I would say. A few observations:

The 100V rating "requirement" is high. 21V peaks will provide about 28 Watts into 8 Ohms. So I would think a 25 or 50 Volt cap would be fine. 50V is probably a better bet except I would never come close with my 8 Watt monsters.

Details are presented to horn speakers in terms of tenths and hundredths of a volt .. generally occuring around 0V. This is a big opportunity for repolarization losses in cap electrolytics and losses due to inductance. Bypassing, especially metalized-film caps, with smaller, very high quality film-pio or film-foil polyprop. may be worth it. I haven't tried, but the signals in my speakers are higher current, but lower voltage than those inside my amps, so it might make a big difference.

leok

[horonzak]

DEAR? SWEETHEART? Your all so loving today.

[Hardhead]

Dean--

Parts Express sells Alpha Core inductors down to 16 gauge from .11 mH to 4.7 mH. Part Nos. 266-652 through 266-690 (even numbers only, for some reason).

[Deang]

Thanks, yes I know -- but I was speaking of Litz wire.

[Al Klappenberger]

Hi guys,

I'm pretty sure the only "polorized" caps are electrolytics. There are non-polar electrlytics. These are ok in the woofer filter. Klipsch uses them (in the AB-3 network for ther Belle for example).

The voltage that develops across caps in a filter will depend on where it is in the filter and what the impedance is at that point. A filter can, and often will, transform the impedance up and down at verious points. This is not likely in a highpass or lowpass filter though. In a bandpass filter it is done intentially to equalize part values (Norton transforms).

Love,

Al K.