Identify blown bulb/fuse from Electro Voice speakers

March 3, 2006 7:08 PM

What exactly is this? It is out of an Electro-Voice Eliminator speaker cabinet (1x15 shown here.)

We blew this thing (stupid mistake was made) and now I can't find replacement info for the life of me. It's about an inch and a half long, 3/8's in diameter. It was mounted in a pair on the crossover in the back of the speaker.
I know that it's a light bulb, and I've picked up lookalike bulbs (with a slightly thinner filament) from the local hardware store, but for the life of me I can't google up any specs on the replacement bulbs for this thing.
Will installing the 12v bulbs that I purchased be a problem?
Any sound engineers deal with replacing these things on a regular basis?

posted by davey_darling to technology (10 comments total)

d'oh

here it is

(admins plz fix link in original post)
posted by davey_darling at 7:10 PM on March 3, 2006

It actually looks more like a vacuum tube....
posted by fvox13 at 7:17 PM on March 3, 2006

It's a fuse.

In particular, it's a blown fuse.
posted by eriko at 7:24 PM on March 3, 2006

Looking at EV's site, they don't have the manual online. (Silly people.) They do have a support request form, though, here.
posted by eriko at 7:30 PM on March 3, 2006

Thanks for the answers so far. I should have been a bit more specific, my apologies.

I know that it is a blown "fuse", which happens to be a lightbulb. This is common in loudspeakers.

I am looking to find out the exact replacement value of bulb I should be looking for. There were no markings on the bulb or the crossover it was out of. As eriko pointed out, there is no manual on EV's site. I extensively googled this topid and came up bupkus.

I can't call or really get any support until Monday, I was hoping someone on mefi would have experience with this sort of this to tide me over till then.
posted by davey_darling at 7:40 PM on March 3, 2006

It's a fuse, not a lightbulb. Despite being a wire inside a glass tube, it does not produce any light at all during normal operation, except possibly for a very brief instant. :)

Let's see, from the data sheet - power, 350 Watts. Impedance, 8 ohms. That means you need about 6.6Amp fuse to max it out. So look for a 6 Amp fuse or so, of a similar size to the blown one. Don't get a slow-blow fuse.

Audio store (I'm guessing would be the easiest place to find these; otherwise try Radio Shack or hardware store). 6 Amp fast-blow fuse, same size as the one you have. In fact, get a couple, tape the extras to the back of the speaker cabinet, for next time.

If the ones you got from the hardware store - with thinner filaments - fit the socket, you can use them. If they have a rating of less than 6 Amps, like say 4 Amps or 2 Amps, what will happen is you'll be able to blow those 4Amp or 2Amp fuses by turning your speaker volume up to, say, 7 or 8 on the dial. If you mostly listen to music with the dial turned to 1 or 2, that's not a problem.
posted by jellicle at 8:06 PM on March 3, 2006

That filament's far too thick to produce any light. It's a fancy fuse.
posted by cillit bang at 8:15 PM on March 3, 2006

Loudspeakers sometimes have fuses that are designed to light up as if they were a light bulb. With certain brands of speakers you can see the inside of the enclosure light up as you are pushing the limits of the power. The brighter the light you see the closer to blowing it you are. It's a form of visual feedback for the person running the mixer.
posted by monsta coty scott at 8:18 PM on March 3, 2006

Assuming it's a fuse, guessing the current rating will depend on where in the crossover it is. The 15" driver needs very little protection but the tweeter may well do if it's not piezoelectric. So if the fuse is in series only with the tweeter, the current rating will be quite different.

Also, if the load is highly reactive (ie non-real, either capacitive or inductive), the current will be a lot higher than what you would calculate from the simple P=VI=I²R formula that really only applies for resistive loads.

My guess is that its presence there is NOT as a fuse but rather as a resistor. Carefully designed crossover networks (where they care about relative phase of output from the drivers to prevent nasty notches in the response) often contain resistors as well as capacitors and inductors. My guess is that they're using the lightbulb for that purpose.

Find another bulb (from your other speaker), measure the resistance, find a globe that has a very similar resistance and try it out.
posted by polyglot at 8:49 PM on March 3, 2006

[fixed FPP link]
posted by jessamyn at 6:41 AM on March 4, 2006