Amateur Speaker fixing hour

[Lisa Lane-Collins]

Had a crack at fixing a mate's DB opera Live 405 today. Unfortunately, my skills begin and end with resoldering loose joins and I couldn't find any.

The speaker's problem:

Last gig it did, someone plugged their own mixing console in and blew everything up, as soon as the patched in, just bam, gone, took out both tops and the sub, in fact, this happened twice. The first time someone in the audience knew how to get everything running again and fixed it up, by the end of the night this 'tech' had managed to blow everything up Again! The sub and one top were just a matter of resoldering the signal wires back on but this speaker has more obscure problems. It carries signal, very intermittently, when it Does carry signal, that signal is sometimes overdriven, but not always, it also sounds kinda mid-ey but that could be a simple as a blown compression driver, without steady signal it's hard to tell. I'm admitting defeat and handing the problem over to a pro but I'm still curious for future reference. Any one have any ideas?

 

[Ivan Beaver]

Re: Amateur Speaker fixing hour

Had a crack at fixing a mate's DB opera Live 405 today. Unfortunately, my skills begin and end with resoldering loose joins and I couldn't find any.

The speaker's problem:

Last gig it did, someone plugged their own mixing console in and blew everything up, as soon as the patched in, just bam, gone, took out both tops and the sub, in fact, this happened twice. The first time someone in the audience knew how to get everything running again and fixed it up, by the end of the night this 'tech' had managed to blow everything up Again! The sub and one top were just a matter of resoldering the signal wires back on but this speaker has more obscure problems. It carries signal, very intermittently, when it Does carry signal, that signal is sometimes overdriven, but not always, it also sounds kinda mid-ey but that could be a simple as a blown compression driver, without steady signal it's hard to tell. I'm admitting defeat and handing the problem over to a pro but I'm still curious for future reference. Any one have any ideas?

When you say "speaker" are you talking about a speaker cabinet (that has multiple drivers) or a single driver?

The FIRST thing to do is to narrow down whether it is a single driver or the entire cabinet.

If it is a multiple driver cabinet-the problem could be in the wiring-or the crossover or the driver itself.

The first rule of troubleshooting is to divide and conquer. So narrowing it down to a specific area is the first step.

 

[Craig Hauber]

Re: Amateur Speaker fixing hour

Are they self-powered speakers? (there is an amplifier built into the back of the speaker cabinets themselves as opposed to a separate rackmount type unit)

If so would there be a chance that the mixer had it's own power-amp built into it and not just the normal line-level outputs (i.e. a "powered mixer" -there are many that look like actual consoles instead of the box type we've all seen before)

If that was the case, then plugging a speaker-level power amplifier type output into a line-level input self powered speaker would cause the very quick death of the speakers like you described!

I have witnessed this many times with speaker systems installed in bars and pubs. I've even seen 1/4" to XLR adapters used to accomplish it!

 

[Lisa Lane-Collins]

Re: Amateur Speaker fixing hour

Well ill be, the deadly mixer turned out to be a mackie onyx.

The speaker is a powered 2 way top box. Sounds to me like the problem lies within the amp/processing part of the signal path. It makes no noise at all, then intermittent noise when i twist the volume pot, that sounds distorted and crap.

 

[Ivan Beaver]

Re: Amateur Speaker fixing hour

Well ill be, the deadly mixer turned out to be a mackie onyx.

The speaker is a powered 2 way top box. Sounds to me like the problem lies within the amp/processing part of the signal path. It makes no noise at all, then intermittent noise when i twist the volume pot, that sounds distorted and crap.

When you say it makes "no noise" what does that mean. Does it mean that it does not pass any audio-or that the audio is fine but there is no ADDITIONAL noise?

It also sounds like a dirty volume control pot or a possible cracked connection on the pot/circuit board connection.

If it is dirty-the "simple" thing to do is to twist it back and forth really fast and try to "kick" the dirt out. If possible I like to run a finger across an edge of the pot-not grab and turn like normal.

You may need some contact cleaner to help wash the gunk out. This requires disassembly to the point you can get to the "access" hole in the back of the pot.

Spray and twist as before.

 

[Lisa Lane-Collins]

Re: Amateur Speaker fixing hour

No noise as in no signal, and when it does come through its sometimes distorted. Ill give the pot thing a go. Did think maybe the connection to the circuit board. Looks good just eyeballing, need to get a multimetre on it really.

What else is likely to be in the signal path between input and speaker? Amp, crossover (active? Passive? Would they put dsp in a budget powered box like that?)

 

[Ivan Beaver]

Re: Amateur Speaker fixing hour

No noise as in no signal, and when it does come through its sometimes distorted. Ill give the pot thing a go. Did think maybe the connection to the circuit board. Looks good just eyeballing, need to get a multimetre on it really.

What else is likely to be in the signal path between input and speaker? Amp, crossover (active? Passive? Would they put dsp in a budget powered box like that?)

I would pull the amp out-and bypass it. Hook a know working amp to the loudspeaker drivers and see if they work OK. If they do-then the problem is in the electronics. If they don't then the problem is in the drivers themselves.

Divide and conquer. The more "guess work" you take out of the situation-the closer you will be to finding the real problem. Narrow the problem down.