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Uh oh! JBL 2118H Mid pfffft


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Hey all:

 

Set the system up after doing my son's graduation last week and one of the mids on my cabs is kaput. Doesn't move or crackle with the 9V battery test and the ohm meter doesn't move when I hook it up. No burnt smell, cone looks good, two copper wires are still connected, but I got nothin' out of it. :confused::cry:

 

Previous thread info re. the event stated that system was never pushed during the event. Amps never clipped, signal from board only went into the first yellow light. All clip limiters engaged. Took all necessary precautions. No feedback. No dropped mics. No pops, hell, I didn't drive the system hard at all.

 

What happened???? Any thoughts? How do I prevent this from happening in the future?

 

What next??? Suggestions?? How much is a recone? should I just buy another one?

 

Thanks in advance for your help!

 

Stix

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Andy,

 

99.9% sure it was working prior to the event. Additionally, the other cab is working fine. Use a mono signal into the DRPA split to the two main ins with four outs (H/Main & Sub) to the two amps - two to Main amp & two to sub amp. Stereo on both amps coming out (not biamped). If it was overpowering, wouldn't both 8" drivers have gone bad? Doesn't make sense.

 

What is a recone typically going to run me for this driver - in the thread RR referred to above, you indicate "expensive"... what's considered expensive? Would I be better off trying to grab one or a pair of fleabay? Currently two pairs are up... one pair has a bin for $150 and the other pair has 7-days to go with three bids up to about $100.

 

Thanks!

 

Stix

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Double-check your programming to be sure there's nothing unexpected. You are somewhat limited in what you can screw up in the DRPA (compared with say the 260) but there are possiblities. What are you using for subs? Exactly how is it configured? What amps?

 

Cost of a factory recone is going to run between $125 and $150 depending on where in the country you are. Buying used drivers is a complete crapshoot, you may be buying somebody else's problems and because of the fragile nature of this driver there's a lot of drivers in bad shape out there. They may make noise but may also be damaged internally and there's no way to tell.

 

Generally, the drivers will fail independantly, especially if one has different pre-existing damage. The power handling is not exact, each one will vary by maybe 10-15%.

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Here's what I've got going on...

 

Mixwiz mono out through the Rane channel A (no funky smiley face - pretty much flat). Rane out to the DRPA with a Y to the two DRPA ins. DRPA set up for a 2X4 crossover - 2 H outs and 2 Sub outs. H outs to PLX 3402 in stereo. Sub outs to PLX3002 in stereo. Mains are 4735's, subs are 4718's.

 

I believe it's crossed over at 100 and filtered at 40 on the low end. The roll-off curves are the ones you recommended back when I first got the system - don't recall them off hand.

 

What is the range an ohm meter should read on a 2118H - I think I read somewhere between 5.8 and 7.0? Does this sound right? What has your experience taught you?

 

As always, thanks for the info.

 

Stix

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Yeah, I'm sure that's possible. This really was the first time I actually "drove" the system with the JBL's (you recall I had the Carvins for a while). Se la vie, I guess I can chalk this up to "shiite happens." I'll get this one reconed and prolly grab one or two off the bay for back-up. Guess it couldn't hurt.

 

So I assume an ohm reading of 6.8 would be outside of the normal range and prolly indicates a pending problem down the road... one of the pairs on the bay has one reading of 6.1 and the other reading 6.8. The other pair has both at 5.8.

 

By the way, any problem with running the cab without the 8" in place? I've taped off the two leads so there won't be a risk of contact.

 

Stix

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Yeah, I'm sure that's possible. This really was the first time I actually "drove" the system with the JBL's (you recall I had the Carvins for a while). Se la vie, I guess I can chalk this up to "shiite happens." I'll get this one reconed and prolly grab one or two off the bay for back-up. Guess it couldn't hurt.


So I assume an ohm reading of 6.8 would be outside of the normal range and prolly indicates a pending problem down the road... one of the pairs on the bay has one reading of 6.1 and the other reading 6.8. The other pair has both at 5.8.


By the way, any problem with running the cab without the 8" in place? I've taped off the two leads so there won't be a risk of contact.


Stix

 

 

6.8 ohms is too high, incicates a potential problem or maybe an aftermarket recone which I do not recommend on this driver. The reason for the +/-10% is that meters are pretty far off at low ohms readings, a static error of +/-0.2 ohms is not uncommon by itself.

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Perhaps someone here would be kind enough to correct me ;) but my understanding of these speakers (and other 15" and 18" 3-ways) is that they were designed to to have good low end without subs and would be fine for that at their 600wrms (times 1.25-1.5) rated power. The SR4718 only goes 5Hz lower :freak:. When you use subs and a crossover with them you are now steering more of that power away from the LF driver to the mid and HF driver so should derate them - I'd guess the power handling drops about half so down to maybe 300w times 1.5 tops so maybe 450-500w? A GX5 would be a good match then.

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The one box oriented product atthis level is pretty good, the problemis that the midrange section is not all that efficient and the crossover slope between the low and the mid is pretty shallow (maybe 12dB/octave) so that if you need a lot of mid output it may not be the best choice. Sub or no sub.

 

That said, it's one of the best soundig boxes of the era, a nice small venue box.

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