needing help with a protection circuit in my floor monitors

[tyson82]

Hi all,

I built a set of floor monitors using a Dayton xo2w-2k crossover on an old Cerwin Vega woofer and a Selenium D220Ti horn driver.
I blew the diaphragms in the Seleniums. I am adding a100w L-pad to the horn side to prevent this from happening again. Is there anything else I should add as a protection circuit?

Thanks

[Paul O]

Re: needing help with a protection circuit in my floor monitors

That must have sounded awful without an L-pad.

At the power levels this will see one of those adjustable L-pads won't last very long, what you need to do is build a 6-8db(depends upon the sensitivity difference between the drivers) non adjustable L-pad with power resistors and wire that in between the Hi-out of the crossover and the compression driver. Here is a tool to calculate the values and it shows you how to wire them in.. http://www.diyaudioandvideo.com/Calculator/LPad/

[tyson82]

Re: needing help with a protection circuit in my floor monitors

Thanks for the info Paul.
Someone had mentioned to me at one time to also put in a bulb for extra protection. Is that something I should still think about?

Sorry for my ignorance, this is not my area of expertise!

[billfitzmaurice]

Re: needing help with a protection circuit in my floor monitors

The only protection circuit that absolutely positively works is a limiter. That said, a 2nd order crossover isn't going to make it for pro-sound. 3rd order is the minimum acceptable, and for a compression driver high-pass 4th order is the standard.

[kblackmore]

Re: needing help with a protection circuit in my floor monitors

I wouldn't use the bulb in a passive crossover. To all that are wiser, please correct me. My thought is when the bulb heats up, the resistance changes with it. This would cause problems with unpredictability under volume due to shift the crossover frequency. If you run an active crossover, the bulb is cheap insurance. I would be remiss though not to mention Bill is 100% correct, if you have a limiter available.

[billfitzmaurice]

Re: needing help with a protection circuit in my floor monitors

when the bulb heats up, the resistance changes with it. This would cause problems with unpredictability under volume due to shift the crossover frequency.

Not when the bulb is pre-filter. That can cause a lot of current to be dropped in the bulb, as the signal to it is only rolled off first order. That's why bulbs are typically used only in relatively low power applications with tweeters crossed over at 3.5kHz or higher.