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Is this electrolytic? Seems like it should be but it doesn't have markings for Polarity, unless the single line is that.

twelvepoint wrote: Tue Feb 03, 2026 2:00 pm I had a pair of Community PA speakers that used lamps as fuses. Why did they not use fuses as fuses? I do not know.

I used to do sound at a terrible club that had those speakers. There was one advantage to using light bulbs as fuses, when the speakers started to glow you knew you needed to back off on the volume.

Kniferide wrote: Tue Feb 03, 2026 5:59 pm

Is this electrolytic? Seems like it should be but it doesn't have markings for Polarity, unless the single line is that.

Nope, just a standard film cap. And the single line is a marking for the outer foil layer of the cap, which can be used as a sort of shield, though its not a major impact. Most modern film caps dont even bother with this marking.

Dr Tony Balls wrote: Tue Feb 03, 2026 7:11 pm

Kniferide wrote: Tue Feb 03, 2026 5:59 pm

Is this electrolytic? Seems like it should be but it doesn't have markings for Polarity, unless the single line is that.

Nope, just a standard film cap. And the single line is a marking for the outer foil layer of the cap, which can be used as a sort of shield, though its not a major impact. Most modern film caps don't even bother with this marking.

Thanks!

adavidmackinnon wrote: Tue Feb 03, 2026 7:04 pm

twelvepoint wrote: Tue Feb 03, 2026 2:00 pm I had a pair of Community PA speakers that used lamps as fuses. Why did they not use fuses as fuses? I do not know.

I used to do sound at a terrible club that had those speakers. There was one advantage to using light bulbs as fuses, when the speakers started to glow you knew you needed to back off on the volume.

My understanding is that the lamps' impedance change as they heat up, which keeps current in check for the actual speakers, so it's not just an all or nothing protection scenario, it prevents the sound changing when it gets too high, but not high enough to blow. Like an olde school 100W bulb as a current limiter. I think Gerald Webber described how that works in one of his olde amp repair vids, I'm sure there's plenty of info on it out there if ye really wanna dig into it. Eminence crossovers still use lamps.

I got the proper replacement bulb and the damn thing still didn't work so I just returned it. I was never going to make it better than it was, and it wasn't worth any more effort from me.

All right, let's talk speakers/cabs.

I need to replace a single 15" speaker in a cab, and my goal is to pop in a KappaLITE 3015 in there. Done, easy.

That said, most of the amps I have run at 4 ohms (Ampeg SVT, Traynor YBA-3.) Am I going to damage anything with the amps having them be mis-matched? My assumption is no, though they may be less efficient.

Can someone confirm I'm correct on this?

four_oclocker_2.2 wrote: Thu Feb 12, 2026 4:42 pm All right, let's talk speakers/cabs.

I need to replace a single 15" speaker in a cab, and my goal is to pop in a KappaLITE 3015 in there. Done, easy.

That said, most of the amps I have run at 4 ohms (Ampeg SVT, Traynor YBA-3.) Am I going to damage anything with the amps having them be mis-matched? My assumption is no, though they may be less efficient.

Can someone confirm I'm correct on this?

Weird, my YBA3 custome (may it RIP) was always 8ohms.

Anyhow the impedance message I always heard was more resistance from the cab is fine, it's just less powerful, but running a cabinet with a lower impedance than the amp is rated at can draw too much and blow tubes or transformers.

Then again I feel like last time this was brought up the true wizards on here had slightly different guidelines.

I've run my 4 ohm Bassman into 8 ohm cabs with both bass and guitar and never had any issues, even when it was on for an entire day in the studio.

The rhyme I heard, which of course could be totally wrong, to remember impedance mistmaching:

"4 into 8, totally great/8 into 4, pay a whole lot more"

This is exactly the groupthink I need - thank you!