Jack 12 horn problem

The Jack of All Trades pro-sound cabs.
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Chopthebass
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Jack 12 horn problem

#1 Post by Chopthebass » Sun Aug 27, 2017 12:53 pm

My Jack 12 has developed an odd problem. The driver is a 3012HO and horn is Eminence BGH-25 (I think thats the name).

When I play an E on my low B string the horn crackles and sound breaks up, but when I play an open E it is fine. I tried two basses and both the same. My other Jack 12 has piezos and no issues. Any ideas what I can check out?

Ian

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Bill Fitzmaurice
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Re: Jack 12 horn problem

#2 Post by Bill Fitzmaurice » Sun Aug 27, 2017 3:42 pm

A blown driver will be blown at every frequency, and besides, nothing below 1.5kHz or so can get past the crossover to the tweeter. Look for a mechanical vibration.

Chopthebass
Posts: 73
Joined: Fri Jun 10, 2016 12:28 pm

Re: Jack 12 horn problem

#3 Post by Chopthebass » Sun Aug 27, 2017 5:16 pm

Nothing is interfering with the HF horn. No loose stuff inside. I wonder if the problem is with the 12" driver? I tried my other cab with the piezos and although not as bad, the bass is breaking up. Never did that before. I must have damaged them both.

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Bill Fitzmaurice
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Re: Jack 12 horn problem

#4 Post by Bill Fitzmaurice » Sun Aug 27, 2017 5:33 pm

I'd try a different amp.

Bruce Weldy
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Re: Jack 12 horn problem

#5 Post by Bruce Weldy » Sun Aug 27, 2017 10:06 pm

Could be a bad crossover. Recently had a monitor I was repairing that I swore had a bad driver....got a new speaker, put it in .....and the same thing. Replaced the crossover, problem went away.

It's was acting up only on low bass notes, too.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Chopthebass
Posts: 73
Joined: Fri Jun 10, 2016 12:28 pm

Re: Jack 12 horn problem

#6 Post by Chopthebass » Tue Aug 29, 2017 10:28 am

Thanks Bruce.

Visually the crossover looks fine. Is there an off-the-shelf one I can buy that you can recommend?

Chopthebass
Posts: 73
Joined: Fri Jun 10, 2016 12:28 pm

Re: Jack 12 horn problem

#7 Post by Chopthebass » Tue Aug 29, 2017 10:34 am

I will post a close up photo of the crossover, and maybe the folks here can tell me if they see something wrong.

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Bill Fitzmaurice
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Re: Jack 12 horn problem

#8 Post by Bill Fitzmaurice » Tue Aug 29, 2017 11:17 am

Narrow it down methodically. Bypass the crossover, run woofer only to rule it out. Then add the low pass filter to rule it out.

Bruce Weldy
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Re: Jack 12 horn problem

#9 Post by Bruce Weldy » Tue Aug 29, 2017 11:26 am

Chopthebass wrote:Thanks Bruce.

Visually the crossover looks fine. Is there an off-the-shelf one I can buy that you can recommend?
I couldn't see anything wrong with the crossover either, but it was definitely the problem. Test each component by itself first as Bill said. If they check out alright, then swap the crossover.

What crossover is in it now? If it's the one from the plans, then why not just get the components and re-build it?

This is probably the closest off-the-shelf for it.....

http://www.eminence.com/speakers/crosso ... =PXB22k5cx

That horn you have needs to be crossed at 2.5k and that's what this crossover is....only 12db slope, but that should work fine.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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