Upgrading crossover components, any advices?

[Ageve]

My plan is to replace the cheap components with Mundorf Mcap's in a pair of old JBL L300 clones.

Is there anything to consider when doing this? Is it OK to replace the electrolytic low-voltage capacitors with 400V rated Mundorfs?

Is there any way of measuring the rebuilt crossovers to make sure everything is ok before connecting an amplifier?

I'm asking because this is the first time I'm replacing crossover components.

This is what the old crossovers look like:

[dantwomey]

Opinions would probably vary greatly on what you might gain. Two good articles on high-end capcitors are:

Capacitor Test


Capacitor Shootout

Regards,
Dan

[SY]

I don't know this particular speaker, but I've experienced readily audible degradation of the sound when supposedly upgrading caps in a speaker where the designer knew what he was doing. For example, replacing the electrolytics in my old Magneplanar MG1s with the same value film caps tipped up the treble into the ear-laser region. So be careful and have some new non-polar electrolytics of the proper value on hand, just in case.

[R-Carpenter]

I would say, fancy capacitors are less unimportant on the tweeter circuit. I don't think degradation is possible if the replaced capacitor is of a correct value but the benefits are very quest enable as well.
If you hell bent on changing parts, start with more budget staff like Solen. Clarity caps are cool looking and not insanely priced. If there's anything at all to be gain, those will do it.

I think in case of MG1 capacitor replacement, there was a back fire. Your MG1 was old and it could be that the electrolytic was simply on it's last legs. Degradation didn't happen over night and you simply got use to the tuned down top end. Once the capacitor was replaced it brought the sound back to normal and made it sound bright. Could that be the case?

[SY]

No, the speakers were less than a year old. Replacing the cap with a similar value of electrolytic restored the sound.

I believe that the reason for this was that the electrolytic's DF and ESR were taken into account in the design (remember my qualifier about a competent designer). Replace it with a good film cap of the same value, and the tweeter level and response changes.

[rcavictim]

New polypropylene, foil and oil motor run caps are very good in audio power applications and are affordable. That would be my first choice for the large values in a passive crossover. Sprague Vitamin-Q (foil + kraft paper in oil) are also good here in the smaller values with tweeters/mids but any I find and use are often 50+ years old. Age doesn't seem to hurt these however.

You won't find me throwing hard to find money away on boutique capacitors.