Has anyone blown their speakers by having mains cable near speaker cables

[MikeHunt79]

I've got a bit of a strange setup for my computer speakers, it's some Event TR-8 speakers, and I've rewired them to run bi-amped from a 4-channel homebrew tripath amp. My crossover is a DCX2496, which isn't ideal but fine for now.

Today I turned my amp on for the speakers for the first time in around 2 weeks, and I heard a strange screech/pop type sound thru the right hand speaker...

It turns out the mains cable for my amp is really close to the speaker cable for the right hand speaker, and I'm thinking the pop-screech couldhave been caused by the inrush current from the mains cable?

It now seems my right speaker tweeter no longer works, and the right woofer sounds really distorted at low volumes, I suspect a fried/shorting voicecoil.

Has anyone else had this happen to them or could to been my amp just dumped a load of DC into 2 out of 4 of it's outputs?

The amp is a 41Hz.com amp 9 basic, and it's being powered by a meanwell 250W 24v SMPS...

 

[Caged]

If the mains cable induced enough of a current in your speaker cables to fry it (and make a screeching sound at a frequency that isn't 50Hz) then I'm amazed your house didn't blow up at the same time. It's far more likely that your amp fried it.

Give the woofer a push, does it make a nice scraping noise?

 

[SkodaMart]

A mains cable shouldn't induce any current as both live and neutral are run together, they will cancel each other out.

 

[MikeHunt79]

If the mains cable induced enough of a current in your speaker cables to fry it (and make a screeching sound at a frequency that isn't 50Hz) then I'm amazed your house didn't blow up at the same time. It's far more likely that your amp fried it.

The screech was really short, and way above 50Hz, but I was using an IEC cable for the amp, and the fuse did not blow in the IEC cable, so I'm guessing that this may not be mains cable related after all.

The amp was set to mute when I turned on the SMPS for the amp, yet there was still a short screech sound, so I'm thinking the SMPS could have caused the screech, as it is supposed switch at above 100KHz, but if it switches at a lower frequency when starting up, then I imagine this would give audible sounds as I have the SMPS and amp PCB mounted a single chassis.

Give the woofer a push, does it make a nice scraping noise?

It does not make a scraping noise, the suspension feels the same as the other working woofer so I'm hoping the voicecoil may be ok after all. Tomorrow I'm going to try different sources and amps, and also order some sort of relay based speaker protection kit...

Do you know if it is good or bad practice to use a Multimeter set to measure resistance to determine if a voicecoil is OK?

A mains cable shouldn't induce any current as both live and neutral are run together, they will cancel each other out.

Well, older amps use a Linear power supply, and things are pretty simple and there should be equal current draw from both live and neutral.

This amp is a little different in the fact I'm using a SMPS, which operates in a similar way to a PC PSU, and things are a little more complex, and I think this is what caused the screeching thru my speakers... When I get some more time tomorrow, I'm going to try and run the amp from a 24v battery, and with any luck there should be no screeching... If the amp is still working that is...

 

[Engram]

Whatever the problem is, it will have nothing to do with proximity to the mains cable.

 

[MikeHunt79]

Whatever the problem is, it will have nothing to do with proximity to the mains cable.

Well, it turns out my speakers are fine, I've finally got around to testing them with another amp and they sound great, so I guess I've got a problem with either my amp or crossover, I'm thinking it maybe my DCX2496 may have started it's infamous egg frying!

Luckily I have a spare, so I'll try swapping it out and hopefully I should have some working computer speakers!