lightbulb fuses

[Girl Toes]

We have a pair of CGM speakers at work that have 2 lightbulb/fuses each in the crossovers. They drive the horns, and with out them, we have no highs. It took me a while to find them, and I guess technically they are an auto part. Now they are installed, and when noise hits a certain level, light emits out of the speakers.

My question is what is the point of that??? I mean, how does a feature like lightbulb/fuses going to do??? They are obviously going to go out, and need to be replaced, so why use something so hard to find??? Are there actual benefits????

[bradb]

dude, the point is that it looks cool as hell!!!

I would expect that in typical use they'd blow before burning out... and auto parts stores are all over the place.. at least outside of NYC..

[RodC]

Do a search I think its been discussed here before, Basicly it works a bit like a limiter. As the Filiment heats up the resistance goes up protecting even when it isnt burnt out.

[leigh]

Do a search I think its been discussed here before, Basicly it works a bit like a limiter. As the Filiment heats up the resistance goes up protecting even when it isnt burnt out.

Lightbulbs are current limiters. Placed in series with the load as a protective measure (here, in speakers, or used with the power cords on tube amps on the fixin' bench), even if the rest of the circuit shorts, the lightbulbs only allow a certain amount of current through.

Here's an easy way to picture it: suppose you're working on a tube amp, and unknown to you, there's a short circuit. For example, a capacitor from the power line to ground has shorted out. Now, if you just plug this right into the wall, it'll blow the fuse in the amp, or trip the circuit breaker in your house, maybe before anything else gets fried or maybe not.

However, what happens if you have a lightbulb in series with a short-circuited amp? Nothing, except the lightbulb glows brighter! Because every lightbulb in your house is meant to be in series with an otherwise "short circuit" (e.g. a lightswitch "shorting" full wall voltage across the lightbulb). So, in this case, you don't blow a fuse, but the lightbulb is glowing really brightly, so you know you've got an issue with the amp.

Using lightbulbs as series current-limiters in speakers doesn't seem like the best idea for studio monitors, as it would seem to introduce a non-linear response. It might make a cool compressor, if that non-linearity was exploited in a design, but for studio monitors, probably not a good thing. I don't know, I'm no expert.

Leigh

[joel hamilton]

There IS a compressor that uses an incandescent bulb as a light source, in an optical arrangement: The NY2A.

It is SO freaky and weird and totally non linear, and lots of fun.

[leigh]

There IS a compressor that uses an incandescent bulb as a light source, in an optical arrangement: The NY2A.

It is SO freaky and weird and totally non linear, and lots of fun.

Yeah, sounds fun. I was actually thinking of a design where the signal would run through the lightbulb, rather than (as in the NY2A) an optical circuit where the lightbulb is in the sidechain, affecting a light-senstitive element which carries the signal. I haven't thought through how that would work, though, and the best thing to do is just try it.

Leigh

[joel hamilton]

There IS a compressor that uses an incandescent bulb as a light source, in an optical arrangement: The NY2A.

It is SO freaky and weird and totally non linear, and lots of fun.

Yeah, sounds fun. I was actually thinking of a design where the signal would run through the lightbulb, rather than (as in the NY2A) an optical circuit where the lightbulb is in the sidechain, affecting a light-senstitive element which carries the signal. I haven't thought through how that would work, though, and the best thing to do is just try it.

Leigh

I knew what you meant. That could be totally fun! I have always wondered about bumping up audio to the point of actual serious voltage, then back down again after a trip through some odd devices, like a light bulb. Other ideas have been more physical, like odd verb sounds of a piece of copper or something, excited to the point of slight oscilation by some audio source, but with some massive voltage driving the copper strip wound into a big coil... like a spring I guess, but moree mutant.

I would also love to find out if there is any bi-metallic strip (like a thermostat) that would actually warp and change shape depending on frequency... like charging the high side differently than the low, and use a giant piece of this metal, so the sound of the plate verb morphs with frequency... Something like that... I dunno.

I just like the idea of physical morphing dependent on frequency, and capturing the change in resonance across the transformation as a verb type effect...

[vvv]

Geek-Op.

[thunderboy]

I only use old stock Sylvanias. The new GE stuff sounds like shit. "Warm White" my ass!

jt