Bad cross-over ?

[hotgas]

My Polk Audio central speaker CS-150 suddently dies on me. I open it up and see a very simple cross-over. How can I test and what the culprit most likely is? Is it the cap?

 

[dgwojo]

Don,
Did you check the speakers impedance at the drivers input terminals?? If good, I'd check the source by attaching a known working speaker to the amplifiers center channels output wires, if that doesn't work I'd suspect the source, not the speakers. It's pretty rare to burn up a crossover especially what looks like nothing more than a bass blocker in this case. Unless of course the input signal clips real bad. Let us know what you find, I find that most surround system failures originate in the amplifier circuits, usually loose solder connections. Good luck!!

 

[Thatch_Ear]

Whether or not the xover is the culprit I would put better parts in that xover on general principal. A ferrite core choke a non directional electrolitic cap? At least change the cap out.

 

[hotgas]

dgwojo


I checked speaker impedence and it is open.

Thatch,

Good suggestion. I will replace the cap 1st then the ferrite core.

 

[Thatch_Ear]

Open as in no reading?

 

[dgwojo]

Can we assume open at the speaker driver terminals (bypassing the crossover)?? If so, it sounds like the driver is toast.

 

[hotgas]

Open means infinity reading. I measured resistance across x-over's input terminals of a good speaker and got readings like 5 ohms. But with this speaker there is no reading (or infinity reading) as in an open circuit.

 

[Thatch_Ear]

What kind of driver(s) as in size and function are in it? I could only find out that it would handle 10 to 100 watts and not even if it was 100 watts contious. That and the fact it isn't made any longer. The xover looks like it might be only 6 db sloped high and low passes. If you know what the drivers impedence used to be you can use a xover calculator and the value of the choke to figure out the range of the driver and maybe replace it with an Eminence or Tang Bang from Parts Express if you want to try and salvage it. A low transient might have blown that thing out with a spike larger than the driver could handle.

 

[dgwojo]

Originally posted by hotgas
Open means infinity reading. I measured resistance across x-over's input terminals of a good speaker and got readings like 5 ohms. But with this speaker there is no reading (or infinity reading) as in an open circuit.

I would read it across the speaker terminals, not the crossover input terminals, most caps read open after charging. Check that and report back, thanks!!

 

[hotgas]

wojo, Thatch_Ear

I measured the speakers' terminals and :dammit: both tweeter and midrange's resistance are open. So it seems they both are toast

 

[dgwojo]

You cooked them!! We only asked for more info becuase you said you measured them at the crossover input. At any rate, do you have pics, sensitivity specs, driver sizes to help locate some replacements? You might poke around www.madisound.com for so nice replacements, I buy my Solen, and Bennic brand crossover caps from them, I never bought drivers there as I only collect Altec, and EV speakers. Let's see some pics!!