Glass Fuse/bulb Protection

They are designed to work as "dynamic resistors", that is to say they show one resistance cold and a much higher one when hot. The problem comes when the "hot" resistance still isn't enough to overcome an overload, using 2 or more in series will help assuming that the hf still sounds ok with the effect of the "cold" resistance.
Some systems use proper light bulbs, these would typically be 12v 22w brake light bulbs or 20w halogens, a 24v 22w would offer higher resistance whereas a 12v 50w halogen would offer lower resistance without decreasing the lamp life.

tweeter box wrote: so if one wanted to put a fuse/bulb just before a comp to act as protection which fuse would be used? would there be different fuses for diff watt intake?

The value of a fuse/lamp/bulb is dependent on the impedance curve and power rating of the driver used, crossover frequency and design,  and is only going to provide about a 3 dB reduction in power when lit.

If the "fuse" handles too little voltage, it will pop on peaks that the driver could handle.
If it handles too much voltage,  the result is like the OP's picture.

The OP's driver shattered the diaphragm before the voice coil burnt up.
It would have started to sound terrible at a much lower volume than needed to cause the destruction.




Edited by Art Welter - 16 December 2011 at 3:07am

At the end of the day a bulb limiter is better than nothing, if it's sized such that it doesn't cause a nuisance anyway! I had a pair of nearly-new HiSys2 brought to me by a very glum chap who said they'd set up at a gig and the mics on stage had been allowed to squeal for 2 seconds during the sound check and the horns had popped before they could dive for the mixer. I examined them and the horns were fine, it was the lamps blown. 2 lamps later and he was a happy chappy.

i f i remember correct didnt peavey used to use a 2 way x over with a lamp type limiter fitted in them. sure they used to fit the same in the rcf/mackie pro touring rigs to.

http://forum.speakerplans.com/light-bulb-in-mid-tops-cabs_topic57133.html

I've blown my lamps in my Wharfedale Lix Monitors a few times while ringing the system out. VERY annoying but atleast its only the lamp that blows!!! I now make sure I have plenty of lamps and my soldering iron at the ready.....hasn't happened for some time now but happened this summer at two consequitive gigs and had to adapt (bodge) some lamps out of the van.