Type/value/source for comp protection capacitor?.

[cooky1257]

Hi all,

Basic question I know but the range and prices you can pay for large value caps has me completely confused as to the best/correct type..help!What do members use?
Comp crossed over at about 750hz.

Thanks

Cooky

[grumpy]

active crossover, direct-connected amplifier?

I'd start with something two octaves below crossover, based on the driver impedance
at that frequency. If there's a large thump or surge, either get a different amp, or move
the capacitor to a smaller value, understanding that it may affect the crossover response
enough that a change in crossover setting(s) may be required (e.g., make the cap response
part of the overall crossover that includes the electronic crossover ... possibly reducing the
slope of the high-pass function to accommodate the effect of the passive part).

Also, if excess gain is available, a resistive attenuator can also provide some protection.

[cooky1257]

active crossover, direct-connected amplifier?

I'd start with something two octaves below crossover, based on the driver impedance
at that frequency. If there's a large thump or surge, either get a different amp, or move
the capacitor to a smaller value, understanding that it may affect the crossover response
enough that a change in crossover setting(s) may be required (e.g., make the cap response
part of the overall crossover that includes the electronic crossover ... possibly reducing the
slope of the high-pass function to accommodate the effect of the passive part).

Also, if excess gain is available, a resistive attenuator can also provide some protection.

This is good info thanks. So if I'm just looking at 100uF/250v on an 8 ohm 2452/Be I'd be far enough away from the active xover freq(750-800). My next question is do I use standard (solen say)passive component-this isn't exactly cheap?

Thanks

[fpitas]

Take a look at motor-run capacitors. At least here in the States they're polypropylene film caps, and are available in values up to 100uF. Often you can find them on eBay for bargain prices.

[macaroonie]

JBL chart

[cooky1257]

Thanks guys,
I've gone for 80uF metalised film polypropylene ones.

Frank