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STX825 HF driver blowing continuosly.


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#1 Sidhu

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Posted 30 March 2013 - 12:56 PM

Hello!

I have been hearing a lot of local reports of the HF driver with the 825 blowing themselves out even on moderate level operation. I always tend not to pay much heed to such reports.

We were contracted to provide SR and engineering services for a small festival in the hills, and I really liked how the 825 sounded when i demoed them, so decided to spec the same for the festival. We don't have any 835's around, and I have an eye on them. The venue does not really more a pair in all, we sent in a pair a side, to be safe.

I made presets for the ITech amplifiers, copied eq setting off the XTI, tansfer compared them with the HD presets, and it sounded great!

To be cautious, I setup a system architect custom panel to monitor all inputs and outputs, and GR meters. the RMS and Peak limiters are set to 1/3 of continuous power, and 3/4th of program power respectively.

My partner is now in the hills engineering, last night, midway, he was very impressed with te rig. Loud and hi-fi, without him hitting a single clip or getting the GR into action. However,
During the last act, he reports one HF driver has gone down.

As of midway today, 2nd and last day, he has lost two more HF drivers, and is now happily running the show of just 1 HF, loud enough to cover the small area. He hopefully will manage though the last act. We have taken some 712's off monitor duty as an SOS.

System :

4 x STX825
2 x ITech 4000
4 x SRX728
2 x ITech 6000

Any ideas ?

Thank you for the time.

Regards,
Sidhu

#2 Sidhu

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Posted 30 March 2013 - 01:39 PM

For those interested, the Device file. ITech amplification, 4K. Preset number 9.

Thanks again!

https://docs.google....dit?usp=sharing

#3 dakos

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Posted 01 April 2013 - 09:48 PM

Dear Sidhu,
Very sorry to hear about that...

As you know speakers break from over excursion or over heating, either way that means you must have somehow they got too much power, I still don't know how that happened but for starters can you write all the presets that you put in including any EQing you had going on, all limiter settings?

Were the limiters engaged at any point?
Avi

#4 Sidhu

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Posted 02 April 2013 - 01:53 AM

HeyDakos!

Very interesting thread going on at PSW. The device file for the preset is linked to the 2nd post in this thread and over at PSW also.

http://forums.prosou...c,143157.0.html

Thanks as always!
Sidhu


#5 dakos

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Posted 02 April 2013 - 03:30 AM

Dear Sidhu,
Since you're working passive I think analyzing the presets is important, more for sound quality rather then reliability. I think the first thing to do is upload pictures of the drivers insides, is the voice coil in one piece? If it's problematic for you to open the drivers then may be pull the drivers out and measure their resistance to start?

What are the complete limiter settings, threshold, release times? Is there a compressor in the signal chain? EQ? Anything other then the X32 and the amps?

BTW the 9th preset in your uploaded device file is for 4880 subs... You would have noticed that...
Avi

#6 dakos

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Posted 03 April 2013 - 04:29 PM

Dear Sidhu,
Looks like Art nailed it as far as analyzing the failures and what to do about them all.

Also you should be on you're way back to the service center.

I wanted to clarify something about the itechs limiters, the IT4000 is rated at 2000W per channel but it has a considerably higher wattage for short bursts of 3000W so even 100V limiter is essential even if it looks at first glance as less then what the amp can output.

Also that 6dB HF boost, I know you copied it and that it sounded good but combine that with a passive configuration, a limiter that protects the LF driver and pretty much useless for the HF driver (don't know why I didn't see it the second you wrote about it) and such a powerful amp and it's kind'a aski'n for trouble.

I sure hope you can prove the JBL service center wrong otherwise it's mucho dinero :(

I guess from now on you'll be biamping your rigs...

Good luck
Avi