jbl m552 crossover , need help

[dezmond]

Hello, I just picked one of these up today to use on a pair of sr4731x speakers. I am having a problem with low/mid output, there is none on either channel . I opened the top panel to inspect the jumper config and everything seems in order. Am I missing something ?

[frank23]

You do not have a low/mid output on either the left or the right channel? That is very strange as the channels inside the M552 are fully separated. If this is a power supply issue, the whole M552 would not operate, so this also does not seem to be the case.

The problem lies not in the jumpers, these are only active in the highs. Maybe you have the rear "divide by 10" pushbutton activated (green led burns on the front) and your low/mid only outputs frequencies too low for your system to reproduce them?

[dezmond]

I am having a problem deciphering the manual regarding the jumpers . In the manual on page 23 is what I am talking about. The SW jumpers, the manual only show normal or reverse . I'm going to try changing those around and trial an error. If anyone knows these switches, please enlighten me.

https://www.jblpro.com/pub/obsolete/M552 Owners Manual.pdf

[dezmond]

This was from a church install, I am trying to contact the original owner to get info on what setup it was used for. I am thinking it was custom configured .

[frank23]

I am having a problem deciphering the manual regarding the jumpers . In the manual on page 23 is what I am talking about. The SW jumpers, the manual only show normal or reverse . I'm going to try changing those around and trial an error. If anyone knows these switches, please enlighten me.

https://www.jblpro.com/pub/obsolete/M552 Owners Manual.pdf

Yes, the manual shows the position for normal or reversed polarity. What is it that you cannot decipher about this? Maybe your low/mid jumpers are taken out and that is the reason you have no signal?

Why do trial and error? There are only two positions possible. Either connect the middle row to the upper row, or connect it to the lower row. You should have sound in both positions.

[dezmond]

On page 23 to the right of the screen where it says what SW12,SW10,SW5,SW3 , are those just for polarity or to actually activate them to ? I am starting to think that this crossover is malfunctioning. Thanks for your help, putting the dbx back in.

[frank23]

The signal goes through them, so if you remove them, there is no signal path. So you either route the signal upwards or downwards to different routes on the circuit, so choosing the polarity.

[Odd]

Maybe this will help

[dezmond]

I took it to the local guitar center and the tech found a missing jumper. I am home now about to hook it up .

[dezmond]

The good news , the mids and highs are both working and passing signal. The bad news, there is a loud hiss added to the highs.

[Mannermusic]

The good news , the mids and highs are both working and passing signal. The bad news, there is a loud hiss added to the highs.

Hi Dez. Been through similar problems with those old M series crossovers. 1) They are old / worn-out. 2) they don't sound so hot even when functioning. I'd move on - there is significantly better stuff out there these days (time marches on!). You can even end up blowing diaphragms or whatever (voice of experience). I gave mine to the local community college for electronics trouble shooting class. Mike

[dezmond]

Thanks for the tip, ya I am done wasting time with this pos. I will just add in a 31 band eq to the dbx 223 and do the cd eq manually.