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[Jeff Kantor]

I purchaced a stx 835 box 2 months ago.  I had used it in about 6 shows when i noticed that the h/f section was not working.  I opend the box and checked the diaphram and everything seemed normal.  I ran the box without the grill and realized that the h/f section was working but at a 30db or so cut.  I sent it to the jbl warrenty center since it seemed that the problem was in the network/crossover section.  JBL called me and said they would not warrenty the repair because of the amplifier I was running peak output was 400 watts over the PROGRAM rated power. Remember I didnt say PEAK, i said PROGRAM.  My responce was well if this was the case shouldnt it have taken out a driver, and not the crossover network? Sounds like JBL tries to get out of everything at the cost of the consumer.  The amplifier I was using was a plx 3602 which I still feel is a great match for the STX 835.  What are some other peoples thoughts about this, and yes I run limiters on all my gear.

[Vinny DAgostino]

How were you operating the box?
Full passive mode or Biamp?
Running the plx3602 bridged or stereo?

That HF section only has a contiinuous rating of 350 watts.

[Chuck Simon]

Something doesn't seem right about this story.  You said you opened the box and checked the diaphragm.  How exactly did you do that?  How did JBL know what amp you were using?  Where was the warranty center?  What did they say the repair would be?   Did you contact your dealer?  If you disassembled anything you could have voided your warranty.  Are you running one amp per cab?  If you want opinions here you will have to supply more info.

I have been using JBL for 30 years and have never used the warranty, but I hear they are pretty good about it.

[Jeff Kantor]

How were you operating the box?
Full passive mode or Biamp?
Running the plx3602 bridged or stereo?

That HF section only has a contiinuous rating of 350 watts.

Im running the box full passive and HP at 65hz and the plx3602 is strapped/bridged.

[Jeff Kantor]

Something doesn't seem right about this story.  You said you opened the box and checked the diaphragm.  How exactly did you do that?  How did JBL know what amp you were using?  Where was the warranty center?  What did they say the repair would be?   Did you contact your dealer?  If you disassembled anything you could have voided your warranty.  If you want opinions here you will have to supply more info.

I checked the resistance of the diaphram which was 4.1 ohms, that is the spec for that driver.  JBL contacted me and asked what type of amplification i was using.  Yes I contacted my dealer, and the warrenty center is near Atlanta. 

News update: JBL has agreed to repair but warns future faliers my not be covered due to me "OVER POWERING" the box.    Now im scared.

[Stu McDoniel]

I purchaced a stx 835 box 2 months ago.  I had used it in about 6 shows when i noticed that the h/f section was not working.  I opend the box and checked the diaphram and everything seemed normal.  I ran the box without the grill and realized that the h/f section was working but at a 30db or so cut.  I sent it to the jbl warrenty center since it seemed that the problem was in the network/crossover section.  JBL called me and said they would not warrenty the repair because of the amplifier I was running peak output was 400 watts over the PROGRAM rated power. Remember I didnt say PEAK, i said PROGRAM.  My responce was well if this was the case shouldnt it have taken out a driver, and not the crossover network? Sounds like JBL tries to get out of everything at the cost of the consumer.  The amplifier I was using was a plx 3602 which I still feel is a great match for the STX 835.  What are some other peoples thoughts about this, and yes I run limiters on all my gear.

The Qsc is rated at 3600watts RMS bridged @ 4ohms

The STX JBL cab you specified is rated at 1600watts RMS and this cab is a 4 ohm load in passive full range mode.

The recommended max power is 2x RMS of the loudspeaker. (3200 watts max)

1600watts X 2 = 3200watts rms (MAX) Power amp output

You are 400watts over what most companies I know recommend.

This is why the xover smoked.

[Jeff Kantor]

The Qsc is rated at 3600watts RMS bridged @ 4ohms

The STX JBL cab you specified is rated at 1600watts RMS and this cab is a 4 ohm load in passive full range mode.

The recommended max power is 2x RMS of the loudspeaker. (3200 watts max)

1600watts X 2 = 3200watts rms (MAX) Power amp output

You are 400watts over what most companies I know recommend.

This is why the xover smoked.

1600/3200/6400 is the rating.  You assume to much that just because I have the ability to push the program rating of the speaker that I did.  The max PEAK is 6400 watts so even a transient would have a hard time making that amp spike that high.  More people blow things up every day due to underpowering than overpowering. The only reason I made this post is to get some feedback on the situation, not informing me of componant ratings.  I never pushed that cab hard and been running my rig for 5 years with not one speaker falier.  I have more PA than i need and I like to have headroom so that its clean and not pushed.  I guess what your are saying is that if I had a plx 3102 that I wouldnt be talking to you now. I dissagree  <3

[Stu McDoniel]

1600/3200/6400 is the rating.  You assume to much that just because I have the ability to push the program rating of the speaker that I did.  The max PEAK is 6400 watts so even a transient would have a hard time making that amp spike that high.  More people blow things up every day due to underpowering than overpowering. The only reason I made this post is to get some feedback on the situation, not informing me of componant ratings.  I never pushed that cab hard and been running my rig for 5 years with not one speaker falier.  I have more PA than i need and I like to have headroom so that its clean and not pushed.  I guess what your are saying is that if I had a plx 3102 that I wouldnt be talking to you now. I dissagree  <3

Howdy Jeff.   I was just giving you the math JBL probably used.

Even at 2x rated RMS power one has to be real darn careful.

I do know very experienced pros in the biz who do A LOT of recones and
frown on the 2x rms ratings companies put out.

1.5x-1.8x might be quite a bit safer.

I am not contesting you in anyway here just giving you JBL's reason and
doing the math they are correct.   

[Jeff Kantor]

Howdy Jeff.   I was just giving you the math JBL probably used.

Even at 2x rated RMS power one has to be real darn careful.

I do know very experienced pros in the biz who do A LOT of recones and
frown on the 2x rms ratings companies put out.

1.5x-1.8x might be quite a bit safer.

I am not contesting you in anyway here just giving you JBL's reason and
doing the math they are correct.

I do agree that it makes more since if their numbers are wrong.  But I still would like to know why the falier would happen at the xover and not the actuall driver.  Is it that the xover jumps off the cliff and marters itself? LOL

[Vinny DAgostino]

But I still would like to know why the falier would happen at the xover and not the actuall driver.

HEAT...
The crossover network most likely can't take the excessive sustained heat it is most likely getting with that much power going into the cab.

Very common issue on the EAW LA325 series cabs, those crossovers used to smoke like crazy with to much power. You had to disconnect the cabs and let them to cool so they would work again!
You could get away with it a few times before parts would actually fail.

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