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[Robert Chafe]

Alright here's an odd situation.  Recently installed a pair of JBL MRX 515’s in a small bar for live music as well as dj.  The pair is powered by a single XTi2000 in bridge mode - IE 2000W @ 4 ohm.  To start things off one the original cabs had an open horn right out of the box. I wrote it off as a 1 in a million fluke, swapped that box for another at the local dealer and installed the pair.  No issues during EQing that during the install, worked perfect the following night for the band & DJ.  On the second night both horns went out in both boxes in quick succession – at almost the exact same time. 

I’m scratching my head on this one.  Could it just be a bad run of horns?!?
Obviously I can swap these boxes out for another pair no problem, but I’m a little gun shy now. Is it a bad run of horns and if I swap this pair out will I have this same issue again?  Or do I just switch to a completely different box?  But at that price point only the EV TR1152 or Peavey SP2 are comparable. 

Thoughts please?!?

[Bob Leonard]

Heavy and sustained clipping will take out the drivers. I suggest you start by running those speakers in stereo mode and stop stepping on the gass when the amp starts to clip.

[duane massey]

+1 on Bob's post. The drivers in the MRX series are pretty wimpy, and I would use extreme caution in overpowering them.

[Robert Chafe]

The cabs are rated @ 800W program & 1600W peak.  XTi2000 @ 4 ohms is 2000W for a pair or 1000W peak per cab.  Which is why I matched a XTi2000 with the MRX515 cabs - roughly double the continuous power rating. And the internal limiter of the XTi2000 is set @ -6 db as well.  In general, input gain and channel levels are at unity and master output negative 10-15 db.  IE the amp wasn't close to clipping.

I've heard some complaints about the quality of those horns but common that is ridiculous!!

[Tim Perry]

Alright here's an odd situation.  Recently installed a pair of JBL MRX 515’s in a small bar for live music as well as dj.  The pair is powered by a single XTi2000 in bridge mode - IE 2000W @ 4 ohm.  To start things off one the original cabs had an open horn right out of the box. I wrote it off as a 1 in a million fluke, swapped that box for another at the local dealer and installed the pair.  No issues during EQing that during the install, worked perfect the following night for the band & DJ.  On the second night both horns went out in both boxes in quick succession – at almost the exact same time. 

I’m scratching my head on this one.  Could it just be a bad run of horns?!?
Obviously I can swap these boxes out for another pair no problem, but I’m a little gun shy now. Is it a bad run of horns and if I swap this pair out will I have this same issue again?  Or do I just switch to a completely different box?  But at that price point only the EV TR1152 or Peavey SP2 are comparable. 

Thoughts please?!?

Well... when you have "DJ" in the equation it greatly adds to the difficulty in keeping speakers functional. There simply is nothing to stop them from pushing the limits beyond what any sane person could tolerate.

You have two 400 watt rms  @ 8 ohm speakers. You have chosen to supply a max of  1,000 watts each to them.

Some of your choices might include:

1: switch to active speakers with separate appropriate sized amps with build in limiting.

2: modify the MRX for bi-amp operation and use a smal amp for the HF plus a limiter or driverack like speaker processor.

3: add series light bulbs to the HF section and ignore whatever small effect it has  in the crossover function.

4: add more speakers

5: stand over the DJ's with a SPL meter in on hand and a club in the other.


As an aside I did a hard rock show last night with MRX525 that was screaming loud. no problems, no clipping. the top amp was plx 1804 (900W @4 ohm /ch)

[Brad Weber]

The cabs are rated @ 800W program & 1600W peak.  XTi2000 @ 4 ohms is 2000W for a pair or 1000W peak per cab.  Which is why I matched a XTi2000 with the MRX515 cabs - roughly double the continuous power rating. And the internal limiter of the XTi2000 is set @ -6 db as well.  In general, input gain and channel levels are at unity and master output negative 10-15 db.  IE the amp wasn't close to clipping.

• The speakers are rated at 400W/800W/1600W for a 2 hour test, the 100 hour rating is 350W/700W/1400W.
• The speakers are nominal 8 Ohm rated, but the actual minimum impedance is going to vary with frequency and the minimum impedance is most likely lower.
• Clipping is not limited to the amp, clipping anywhere in the signal chain, say right at the start by the DJ, means the signal has been clipped.
• Sensitivity on the XTi2000 is about +5.14dBu.  For many mixers, -10 to -15 on the output meters represents a level greater than that.  Are you attenuating at the amp input?

[Robert Chafe]

Well, I'm assuming the DJ wasn't clipping the input but unfortunately that something I just can't control. 

Sounds like the safeest bet would be to redesign the system a bit.  I don't want to cut into the MRX cabs and rewire or change anything - especially since I'm not sure we're going to keep them.  How about switching the XTi2000 to stereo mode so it will be a peak of 475W @ 8 ohms per speaker?

Looking at comparitivly priced cabs from other manufactures...the only thing on paper that looks like it may be a more robust choice is the Peavey SP2.  Thoughts??

Thanks again for everyone's input!! 

[Chuck Simon]

My experience is that the MRX cabs are pretty robust, if properly managed, but nothing will stand up to abuse, and I think that is your problem.

[duane massey]

EAW VR51
http://www.eaw.com/products/vr51.html

[Chuck Simon]

EAW VR51
http://www.eaw.com/products/vr51.html

Yeah, you could let the DJ destroy a more expensive speaker!

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