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Keep blowing up compression drivers?!
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Old Croc
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Points: 4257 		Post Options Post Options   Thanks (0) Thanks(0)   Quote 4D Quote  Post ReplyReply Direct Link To This Post Posted: 08 March 2017 at 7:07pm

I would suggest that to keep using the amp after losing drivers could be considered a tad optimistic.

You could bite the bullet and take the amp to a competent repair shop for a service

Or post some pics of offending voice coils for more informed diagnosis

Essentially on visual inspection all dark brown coil is a overheating issue or a coil that looks like it was hit by lightning, isolated burn marks, holes blasted in the former etc is indicative of amp failure.

 

Or say fuggit & swop channels over and see if anything else fails
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Points: 547 		Post Options Post Options   Thanks (0) Thanks(0)   Quote rish Quote  Post ReplyReply Direct Link To This Post Posted: 08 March 2017 at 7:20pm
Is the settings on the lms fine for that channel. Could also be that your lms is faulty on that channel.

Rish
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Also place a 10dB attenuator on the input to the hf channels on the amp, that amp can put out close to 120Vrms.
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Points: 1799 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 08 March 2017 at 7:49pm
Originally posted by fatfreddiescat fatfreddiescat wrote:

Also place a 10dB attenuator on the input to the hf channels on the amp, that amp can put out close to 120Vrms.

Yeah and the typical lms can put out over +14dbu so what does that solve?
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Originally posted by Teunos Teunos wrote:

Originally posted by fatfreddiescat fatfreddiescat wrote:

Also place a 10dB attenuator on the input to the hf channels on the amp, that amp can put out close to 120Vrms.

Yeah and the typical lms can put out over +14dbu so what does that solve?

Any crap signal upstream of the amp gets attenauted by 10dB, DCX for instance tend to have issues with ribbon cables etc.
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My main concern would be that for a single 1" compression driver to keep up with a pair of 12" midrange drivers, especially at a very low crossover point for a 1" is a big ask. I think it's a simple over driving issue.

Raise the crossover point and/or upgrade to a larger diaphragm compression driver.
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Nothing I'm afraid, to answer your questions:

No the Beyma is not over driven by the amp, because channel 4 works just fine.
And as I already said, this combination worked fine for over a year.

It's the past 3 months that I started blowing CD drivers,  and it's kind of Russian roulette when things go wrong, it does not seem power related, as I've blown drivers with moderate power levels.

This exact setup was powered by 15 years old mx3000 and mx1500 amps for 3 years without a problem whatsoever.

So I'm 95% sure the amp is faulty, but I'm afraid Thomann will not find anything wrong with it when I send it back for repair/replacement, as the problem is not apparent every time.
How's the warranty handling from Thomann anyway?

But the capacitor safety measure is a very good idea, any thoughts on quality brands?
Nichicon/panasonic?
  
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Originally posted by ceharden ceharden wrote:

My main concern would be that for a single 1" compression driver to keep up with a pair of 12" midrange drivers, especially at a very low crossover point for a 1" is a big ask. I think it's a simple over driving issue.

Raise the crossover point and/or upgrade to a larger diaphragm compression driver.
 

 Beat me to it! This was my first thought too. Also, what sort of material are you playing through the system? When I was doing techno/hardcore/hardstyle nights which was always very compressed source material and shouty MC's I was crossing my 2" comps at 1.5k, any lower and I think they would have been toast. A 1" at 1.5k is going to be pushed very hard above 2x12's IMO.
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Originally posted by jerronimo jerronimo wrote:

Nothing I'm afraid, to answer your questions:

No the Beyma is not over driven by the amp, because channel 4 works just fine.
And as I already said, this combination worked fine for over a year.

It's the past 3 months that I started blowing CD drivers,  and it's kind of Russian roulette when things go wrong, it does not seem power related, as I've blown drivers with moderate power levels.

This exact setup was powered by 15 years old mx3000 and mx1500 amps for 3 years without a problem whatsoever.

So I'm 95% sure the amp is faulty, but I'm afraid Thomann will not find anything wrong with it when I send it back for repair/replacement, as the problem is not apparent every time.
How's the warranty handling from Thomann anyway?

But the capacitor safety measure is a very good idea, any thoughts on quality brands?
Nichicon/panasonic?
  
     

 It could just be coincidence that the drivers that have died have been connected to channel 3, also, if the drivers have previously been overpowered to the point of almost failing they then may fail at a moderate volume when next used. As said earlier, inspecting the blown diaphragms would probably give the answer to the issue. 
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Points: 438 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jerronimo Quote  Post ReplyReply Direct Link To This Post Posted: 08 March 2017 at 8:42pm
The system is still in the lock-up, will have a look this weekend to see what the damage on the voice coils is.
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Points: 1083 		Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 08 March 2017 at 8:47pm
Double check your lms settings just in case. Consider using channel 3 for one of the 12's in the short term if you must use it. Thomann tend to be quite good re warranty repairs, maybe worth giving them a bell and see what they say, it may be a known issue with their repairs dept. I would also try and get a scope on it to look for hf oscillation and if you can get a volt meter that has a hold function, set it to read dc when amp is in use and look to see what it reads, check the screen connections on the patch cable. It does seem like either an lms output issue or the amp has a problem.
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madboffin View Drop Down
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Nichicon and Panasonic capacitors are polarised electrolytic types which are not suitable for this application.

You need to use plastic film capacitors, preferably rated at 250VDC.

Polypropylene types are the best, and are used by most of the professional manufacturers. Not cheap, but worth it.

Don't use the "nonpolarised electrolytic" capacitors used in some cheap hi-fi crosovers - they are poor quality and have a short service life.

--------

Compression drivers should always have some kind of protection filter. It's not just for DC, but also to block 50Hz hum that might occur due to a bad connection.
And it protects against the effects of inadvertently plugging the HF unit into the low or mid amplifiers when setting up the system...




Edited by madboffin - 08 March 2017 at 11:52pm
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