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Author Topic: jumping terminals on jbl control 1st  (Read 5312 times)

greg molina

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jumping terminals on jbl control 1st
« on: November 12, 2010, 12:49:25 pm »

hello folks, any input is greatly appreciated. i'd like to bypass the built in transformer on this cab, but have no idea as to what terminals i need to jump to make it into a normal 8 ohm. anybody know how this is done? i've searched the jbl site, but with no luck.
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Charlie Zureki

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Re: jumping terminals on jbl control 1st
« Reply #1 on: November 12, 2010, 03:44:38 pm »

greg molina wrote on Fri, 12 November 2010 11:49

hello folks, any input is greatly appreciated. i'd like to bypass the built in transformer on this cab, but have no idea as to what terminals i need to jump to make it into a normal 8 ohm. anybody know how this is done? i've searched the jbl site, but with no luck.



  Hello Greg,

  Are these the Control 1 Pro.....model of speaker? If so, there is no transformer. The are rated at 4 ohms nominal.



  If they are an older version with a transformer....
  I believe you'd have to open it up and remove the wires from the transformer to the speaker and replace them with your run back to the amp.

  Cheers,
  Hammer
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greg molina

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Re: jumping terminals on jbl control 1st
« Reply #2 on: November 12, 2010, 04:48:06 pm »

Hello, these are part of the crown 180max pack. there's a transformer inside that's connected to the main xover with black, white, green and yellow wires.i took the wires out bypassing the transformer, but when i hooked up an amp, no sound is coming out.
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Charlie Zureki

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Re: jumping terminals on jbl control 1st
« Reply #3 on: November 12, 2010, 06:08:43 pm »

greg molina wrote on Fri, 12 November 2010 15:48

Hello, these are part of the crown 180max pack. there's a transformer inside that's connected to the main xover with black, white, green and yellow wires.i took the wires out bypassing the transformer, but when i hooked up an amp, no sound is coming out.



 Hello Greg,

 You say you bypassed the transformer?  But, no sound is coming out?

 What amplified source are you using? and are you sure it's providing an output?

  These speakers are only rated for 20 watts.

  I'm guessing that you'd need to use the Black & White wires.

 Hammer

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greg molina

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Re: jumping terminals on jbl control 1st
« Reply #4 on: November 12, 2010, 08:41:44 pm »

From mixer to crest amp to ctrl 1st. I have a jbl ctrl monitor on the r/channel which is producing sound. all wires disconnected at the main xover terminals. An ebayer that sells this says that you only have to jump 2 terminals after you've bypassed the transformer. That's the answer I'm looking for. Tnx
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Hal Bissinger/COMSYSTEC

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Re: jumping terminals on jbl control 1st
« Reply #5 on: November 13, 2010, 05:20:33 pm »

My advice is that you need to know what you are looking at. From your previous posts it seems you have asked about this a few times before.

Either that or stop buying off Ebay.

-Hal

greg molina

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Re: jumping terminals on jbl control 1st
« Reply #6 on: November 13, 2010, 08:57:30 pm »

Hello Hal, I'm doing this as a donation to our local non profit organization that holds bingo and seminars on weekends. I am by no means an expert on this field. I'm installing and buying the pa system, so pls. forgive me if i've wasted your time in answering my question. Also, i'm not that rich that i can just buy these at retail prices. Again, thank you for the advice, in the present time, i'm also researching this through other audio forums, so as soon as i get the correct answer, i'll let you guys know. I'm a Honda mechanic by trade, maybe i can lend you some good advice if you have a Honda.
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Charlie Zureki

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Re: jumping terminals on jbl control 1st
« Reply #7 on: November 14, 2010, 02:26:16 am »

greg molina wrote on Sat, 13 November 2010 19:57

Hello Hal, I'm doing this as a donation to our local non profit organization that holds bingo and seminars on weekends. I am by no means an expert on this field. I'm installing and buying the pa system, so pls. forgive me if i've wasted your time in answering my question. Also, i'm not that rich that i can just buy these at retail prices. Again, thank you for the advice, in the present time, i'm also researching this through other audio forums, so as soon as i get the correct answer, i'll let you guys know. I'm a Honda mechanic by trade, maybe i can lend you some good advice if you have a Honda.



   Hello Greg,

   The problem with getting helpful information to you,  is that we are not familiar with those speakers, the wiring color code of the Transformer/ crossover, and exactly what's in their circuit design.

   Having checked the model of the gear Package (because these speakers only come in a package deal with the tuner/amp) ....and then on to the specs and Operators manual, tells us nothing.

   There are no color codes listed, and no crossover circuit schematic.

   If you've connected  the black and white speaker wires and you're getting nothing, it could mean:

  a.) the crossover has some parts that need replacing

  b.) there's something you're doing wrong

  c.) the cable you're using from the amp is bad/wired wrong

  d.) the amp channel is bad (did you swap for a known good channel?)

 

 Using a crest amp may be a bad idea, even for checking them, because, these speakers handle only 20 watts. I'm not sure what this "ebay seller" is referring to in regards to two jumpers.

 I don't believe, for the low cost of this system, they would "design in" an impedance conversion circuit besides the transformer it already has.

 In my opinion, with these cheaper model of speakers, there is only one way to easily and certainly change these boxes from a 70v transformer input to a low impedance input....and that is to completely bypass the transformer. (TAKE IT ELECTRICALLY OUT OF THE CIRCUIT).

  Again...on one side of the transformer (input side) should  have 4 wires.....the other side of the transformer should only have two wires and those should be attached to the crossover. THOSE TWO wires are the ones you need to connect your 4 0r 8 ohm output from your receiver or amplifier.


  You will never make these speaker cabinets into 8 ohm speaker cabinets....they ARE 4 OHM!

  Lastly, WHY are you wanting/needing to change these speaker boxes to 8 ohms..?  (although they're 4 ohm)  Did you get the Receiver that originally came with the "package"?  If you did, why are you not using the receiver in the 70v mode?


 Hammer
   

 
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Hal Bissinger/COMSYSTEC

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Re: jumping terminals on jbl control 1st
« Reply #8 on: November 15, 2010, 01:11:18 pm »

A thought occurred to me- could the transformer be a PC mount soldered to the circuit board with leads to the wattage selector switch?

...why are you not using the receiver in the 70v mode?

My thoughts exactly. Really, I'm not trying to be mean but why are you banging your head into the wall over this and those others you asked about? Nobody knows what's inside them unless we look. Seems to me that it would be simpler to focus on how to use the speakers as they were designed. Coming up with a 70v output is no big deal and would make things easier by allowing you to use any number of speakers.

-Hal



Charlie Zureki

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Re: jumping terminals on jbl control 1st
« Reply #9 on: November 15, 2010, 01:45:01 pm »

Hal Bissinger/COMSYSTEC wrote on Mon, 15 November 2010 12:11

A thought occurred to me- could the transformer be a PC mount soldered to the circuit board with leads to the wattage selector switch?

-Hal




 Hello Hal et al,

 I was thinking the same thing, but, I'm not certain that Greg and I have been understanding each other.

 I would suggest that if Greg needs to have an inexpensive 8 ohm speaker, that he should look into the "Audio Source product line.  They have a really low cost ($20. Pr.) speaker that comes with a mounting bracket.

 Also, Greg mentioned that he was intending to install this gear as a PA., which is not really the intention of the design or the manufacturer. It was meant as a Music Background system. (read: low level music)

  According to the Manufacturer's specification, only one speaker should be used when operating this system with a 4 ohm load in the low impedance configuration.

  Although he hasn't given us any real intention on how he intends to "install" this gear, I believe he's headed in the wrong direction.

  Cheers,
  Hammer

 
 
 

 
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