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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
imhififan's avatar
imhififan
2,180 posts
 
Tell you what,you guys have put so much time and effort into this,this weekend i am going to clean everything up and start again,i will take variuos readings on crossovers,re-assemble the whole two speakers and do it all again and then i will come back with a list of readings,it seems thats all i can do,
Something to consider:

Put the LF xover ( the 3.5mH inductor and 51uF capacitor ) on a separate circuit board to eliminate shorts from HF/MF crossover components.
Better yet, upgrade to air core inductor!

https://images-na.ssl-images-amazon.com/images/I/71pf0GZOI1L._AC_SL1500_.jpg

fiesta75
1,378 posts
 
imhififan - I agree on both suggestions. I just recently learned that iron core inductors are suppose to be better than air core for the bass driver due to the lower dc resistance in many cases. Tannoy  is one that uses iron core on some speakers, I'm still learning... He wouldn't even need to make a PCB, he can just use point to point wiring for those 2 components and that would also reduce the dcr.
erik_squires
16,046 posts
 
imhififan - I agree on both suggestions. I just recently learned that iron core inductors are suppose to be better than air core for the bass driver due to the lower dc resistance in many cases.

Yeah, they have lower DCR, but sometimes that DCR is quite useful as part of the baffle step compensation, and in even ordered parts of a high pass filter that DCR is again quite handy.  Still, if you want massive power handling, and a very low frequency cutoff, iron core is hard to beat.

Best,

E
imhififan's avatar
imhififan
2,180 posts
 
I just recently learned that iron core inductors are suppose to be better than air core for the bass driver due to the lower dc resistance in many cases.
@fiesta75
If replace a cored inductor with air core, I think it is important to use the same inductance air core inductor with very close DCR to the cored inductor, it will be bigger, heavier and cost more.
I’m still learning...
I'm as well, learning is a lifelong process.
He wouldn’t even need to make a PCB, he can just use point to point wiring for those 2 components
Agree 100%

fiesta75
1,378 posts
 
Lower than expected dcr for 0.22uH inductor; from what I can tell, a nominal dc resistance for that inductor is about 0.21 ohms. Think that is one area that needs some additional testing.
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