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testing a crossover

hi guys and girls i have a
problem with my 3 way  wilmslow-audio mirrage speakers , I am hoping you can help me with the problem,.
Lately my power amp went pop and i sent it away for repair,when i
received it back {repaired} it went pop again,on sending it back to
the repair technician ,he has come back to me ,and asked me to take
some ohms readings on the speakers, on testing the speakers , i run
these speakers using 2 power amps{Arcam Alpha 10s,using one for low
pass{bass} and the other for MID/HIGH,this is the amp which keeps
blowing,on the high /mid,on testing the terminal the bass{low pass}
read {left speaker]7.9 ohms ,right speaker bass 6.8ohms, But on the
left and right speakers hi/mid ,both read 0.0 ohms,{which we all know
is wrong}
BUT the strange thing is,when the blown amp was away,i only used one
power amp to run both speakers in bi wire config,and they worked
ok,all being a bit lack of bass and tightness,but still sound great.
So i stripped both speakers and checked the drivers,all 6 drivers
where good no shorts reading approx correct ohms for age,{Speakers
disconnected from x over}.can any one help with this,i would be so much in debt.
kind regards Mark
likklegerry
pragmasi
212 posts
 
Pragmasi-im really sorry,but there are no open circuits
Absolutely nothing to be sorry about at all... would just be good if we could help you fix this.
shorting links on speaker binding post havent ever been used,to go from bi-wire to normal two wire
Shame... thought I was onto something there... how do you connect the terminals when running from one amplifier?

It'd be useful if you could describe where you're measuring the short circuits using the references you've added to the PCB with a sharpie.

Would be great if we could all help you get to the bottom of this.
likklegerry OP
30 posts
 
pragmasi- 1) Original test with everything assembled showed 0Ω resistance across the MF/HF +/- terminals on the back of the speaker.
2) Those terminals connect directly to IP+ and IP- on the crossover PCB.
3) With the crossover disconnected the DC resistance between IP+ and IP- was open circuit.
If points 1-3 are correct and you’ve put it back together and measured 0Ω across the loudspeaker terminals then there’s a short somewhere between the terminals and where the wires connect to IP+ and IP-.

totally correct

4) With everything disconnected from the crossover you measured the resistance across the copper you have marked M+ and M- and got 0Ω.
                                   -not sure where i said that-
                                       No it reads 2.7ohms
hope that helps.
Mk
fiesta75
1,378 posts
 
likklegerry - Just forget that question, I already understand. Providing your crossover passed the test using the diode mode at the mid/high bi-amp inputs, which it appears to have. I think you are good to go. Just perform that same test with the drivers connected. I'll get back in touch later today.
likklegerry OP
30 posts
 
i had a good play about with them both today,x-overs,couldnt find a problem ,maybe i should just strip them down,or one,check all parts then reasemble,not sure how to test the inductors though,as i can see i dont know enough, I can test parts but all this equations for test with a multi meter only,idont evem know what mH is !!??.Didnt think this would be that hard, obviously im wrong again.
cheers guys for all your help
pragmasi
212 posts
 
1) Original test with everything assembled showed 0Ω resistance across the MF/HF +/- terminals on the back of the speaker.
2) Those terminals connect directly to IP+ and IP- on the crossover PCB.
3) With the crossover disconnected the DC resistance between IP+ and IP- was open circuit.
If points 1-3 are correct and you’ve put it back together and measured 0Ω across the loudspeaker terminals then there’s a short somewhere between the terminals and where the wires connect to IP+ and IP-.
totally correct

Okay, that should narrow it down a bit and you can stop worrying about the crossover. If you only get the short when the loudspeaker is reassembled then you're looking for something between the crossover PCB and the loudspeaker inputs. If you disconnect the crossover you should be able to track it down... what are the binding posts on the loudspeaker mounted to, plastic or could it be anodized aluminium?
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