Do Crossovers Get Hot?

[Baby Huey]

Hi,

A newbie question:

Almost completed a loudspeaker with the crossover temporarily on the outside attached to the back of the cabinet.

Would it be OK to wire up the crossover parts on a small plastic tray (it has small holes all throughout it) or would there be a risk of it melting if the capacitors, resistors and inductors got too hot?

Thank you.

[Taran]

Re: Do Crossovers Get Hot?

They can and do get hot. Why not just use some scrap wood?

[dthomas]

Re: Do Crossovers Get Hot?

They shouldn't get too hot. Resistors used to pad drivers can get a bit hot and should be positioned so they have air flow around them. But if the crossover is properly designed and not being overpowered then no they shouldn't get hot in terms of melting plastic.

So your crossover is mounted to the back of the speaker after some playing time did it get hot?

[Baby Huey]

Re: Do Crossovers Get Hot?

Hasn't got hot yet because I haven't completed it. It should be ready next week for a full workout.

And thank you.

[joeybutts]

Re: Do Crossovers Get Hot?

You have to be absolutely BEATING on it for it to get dangerously hot I think. Only crossover I ever saw get ridiculously hot was the one I built for the school weightroom. The kids absolutely beat the crap out of that system. Wood was blackened from the resistors.

[john trials]

Re: Do Crossovers Get Hot?

You could always mount the resistors elevated up off the crossover board if you are concerned about too much heat. Inductors and capacitors shouldn't be a problem.

[PEB]

Re: Do Crossovers Get Hot?

Here is a rough rule of thumb. Generally, the closer a resistor is to the amp in the circuit, and/or the lower its value, and/or the lower in frequency it sees, the greater the chance for it running hot.

There are a couple spots in some of my topologies that I know to spec a 25W resistor. 125F is no problem, but 175F implies changing to 25W.

For example a 40ohm resistor across the woofer's series inductor is no problem. It is A) close to the amp, and B) sees low frequency, but C) is a high value.

A 1ohm resistor in series with the first cap in a tweeter circuit is A) close to the amp, B) sees low(ish) frequency, and C) is low resistance. So it is a problem.

[Pete Schumacher]

Re: Do Crossovers Get Hot?

Ask Dave Pellegrene about that . . . :eek:

Where in the crossover is important as well.

Music is not like white noise with equal energy across the spectrum.

It's more like pink noise, or brown noise, with diminishing energy as you move up in frequency.

If you break up the spectrum into three decades, 20-200, 200-2000, 2000-20000, you'll have about half the total energy in the first decade, and about 2/3 of what's left in the middle decade.

If your amp is 100W, and you're running it without clipping, you can deliver about 30WRMS long term under music conditions; 15W to the woofer, 10W to the mid and 5W to the tweeter. In a two way, you'll have 75% or more going to the woofer.

[davepellegrene]

Re: Do Crossovers Get Hot?

My claim to fame!
The resistor Pete is referring to was a 4 ohm parallel resistor on the mid of the Mini Statements. It was a 10 watt resistor that I had buried in the damping material and was pushing the speakers with a 300 watt pro amp. Once I melted the damping material, burn't a hole through the crossover board and almost caught the speaker on fire I replaced it with 4 Parallel 16 ohm 10 watt resistors and all is good. I also put the crossover out on top of the damping material and lifted the resistors off the board. Jim Holtz called it the perfect storm.
I've gotten other resistors hot during testing crossovers and it always seems to be in the mid that does it. Never got one hot in a two way.

Dave

[martyh]

Re: Do Crossovers Get Hot?

My claim to fame!
The resistor Pete is referring to was a 4 ohm parallel resistor on the mid of the Mini Statements. It was a 10 watt resistor that I had buried in the damping material and was pushing the speakers with a 300 watt pro amp. Once I melted the damping material, burn't a hole through the crossover board and almost caught the speaker on fire I replaced it with 4 Parallel 16 ohm 10 watt resistors and all is good. I also put the crossover out on top of the damping material and lifted the resistors off the board. Jim Holtz called it the perfect storm.
I've gotten other resistors hot during testing crossovers and it always seems to be in the mid that does it. Never got one hot in a two way.

Dave

It was a beautiful thing!

[Flacjunky]

Re: Do Crossovers Get Hot?

I think about that every time I watch Queen in Montreal. :eek:

[Soundslike]

Re: Do Crossovers Get Hot?

I have a set of speakers that were thought to be leading edge in their price range back in the late 70's, that belonged to my neighbor. He managed to run into them with a golf cart, splitting one of the cabinets so he gave them to me. He had three boys when the speakers were new and later in life they admitted to playing them as loud as they could get them for hours at a time. When I took the speakers apart this is what I found. It's a crappy looking crossover I know, but the lesson is that resistors can and do get hot. Hot enough to toast wood. I'd be reluctant to use plastic.

[davepellegrene]

Re: Do Crossovers Get Hot?

Ok, since I've been provoked.

This was the first crossover I had ever built and went a little nuts with the hot glue as well.



Dave

[theLinks]

Re: Do Crossovers Get Hot?

Queen was rocking the whole neighborhood! :D Sorry Dave, lol

Ok, since I've been provoked.



This was the first crossover I had ever built and went a little nuts with the hot glue as well.



Dave

[greywarden]

Re: Do Crossovers Get Hot?

That's [email protected]@SS Dave