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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
fiesta75
1,378 posts
 
likklegerry - Thanks for your test data, looks like everything except the Lo and Hi bi-wire connections are in line with what I expected. Just to be clear, with the amplifier and other electronics off, an ohm meter test between the HF+ and LF+ terminals should be 0.0 ohms. Same should be true of the HF- and LF- terminals. This can be measure at the speaker or amplifier terminals.
The diode mode tests at the HF and LF connectors also show what I was expecting.
The dc resistance measurements with the drivers disconnected are in line of what is expected too. Don't worry if it's mH or not, trust us, it is mH.
Which capacitors (value) is showing shorted in the diode mode? The caps themselves should be tested in the ohm mode. I will continue reading an ask questions or make comments as needed.
Please do the resistance test between the HF and LF terminals as described above. This is in the bi-wire configuration with all wires connected to one amplifier.
pragmasi
212 posts
 
between the HF+ and LF+ terminals should be 0.0 ohms
do you mean open circuit?.. Not being snarky, just checking :-).

You have made me think of something though... if you forgot to take the shorting plate/wires off the loudspeaker posts when switching to a bi-amp config you could get enough current flowing between the two amplifiers to blow one of them.
fiesta75
1,378 posts
 
pragmasi - I assume your post above was meant for me? I guess I really didn't need an answer to the last 2 sentences of my above post because I'm sure the answer is really yes, and maybe confusing to some.
You are absolutely correct about forgetting the jumpers when switching from bi-wiring to bi-amping. That could easily blow one or both amps used in a bi-amp configuration.
erik_squires
16,389 posts
 
Dude, you should have followed my advice and you'd be done by now. :)
pragmasi
212 posts
 
@erik_squires 
Dude, you should have followed my advice and you'd be done by now. :)

The best way I know of to test a crossover is to generate an impedance graph. You can use DATS V2 (or is it now up to V3) or you can build a jig and use Room EQ Wizard’s app for this.

How is that advice?.. it's not going to help anyone who doesn't already know what they're doing.
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