Infinity P162 Crossover Problem?

T

the drizzle

Audiophyte
Hi all. I have owned a 3.1 system based around Infinity P362s and C350 for around 10 years. I recently moved and wanted to add rears so I picked up some P162s on ebay. As soon as I hooked them up to test them I noticed they sounded very muddy.

I checked the resistance on both tweeters and found they were both blown and was able to get a refund. The tweeters were discontinued, but infinity told the the tweeters from the C350 center channel were close enough so I ordered a 2 of them. The housings were different but after some grinding I got the tweeters installed.

One of the speakers sounds good, but the other still has almost no highs above 3000hz. I used REW to generate test tones and I am barely getting anything out one of the speakers above 3k. I tried swapping the tweeters but the problem remained in the same speaker so I think I can rule out a DOA tweeter. That leaves the crossover and the woofer. I assume a bad woofer wouldn't cause these symptoms. So that leaves the crossover. I pulled the board out and there was nothing obvious like a visually leaking capacitor.

Any advise on where to go from here? Is there anything else to check before I either try to replace or rebuild the board? The capacitors are radial which I can't seem to find with the right specs so it will be a little messy if I have to replace them all with axial caps.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Hi all. I have owned a 3.1 system based around Infinity P362s and C350 for around 10 years. I recently moved and wanted to add rears so I picked up some P162s on ebay. As soon as I hooked them up to test them I noticed they sounded very muddy.

I checked the resistance on both tweeters and found they were both blown and was able to get a refund. The tweeters were discontinued, but infinity told the the tweeters from the C350 center channel were close enough so I ordered a 2 of them. The housings were different but after some grinding I got the tweeters installed.

One of the speakers sounds good, but the other still has almost no highs above 3000hz. I used REW to generate test tones and I am barely getting anything out one of the speakers above 3k. I tried swapping the tweeters but the problem remained in the same speaker so I think I can rule out a DOA tweeter. That leaves the crossover and the woofer. I assume a bad woofer wouldn't cause these symptoms. So that leaves the crossover. I pulled the board out and there was nothing obvious like a visually leaking capacitor.

Any advise on where to go from here? Is there anything else to check before I either try to replace or rebuild the board? The capacitors are radial which I can't seem to find with the right specs so it will be a little messy if I have to replace them all with axial caps.
Do you have a multimeter? Do you have access to a signal generator. There are signal generators on the NET that will turn a computer into a signal generator.

Can you draw out the circuit and post it here?

Since the guy blew the tweeters he has probably blown a cap or resistor in the crossover.

Now the problem could be in the low pass or high pass sections.

The first thing to do is to check the value of the L-pad resistors with the multimeter. The most likely failure is in the series cap in the high pass section.

If it is a first or second order crossover there will be one series cap. If it is third order, two and if fourth order three. Most likely there will be on series cap.

So if the resistors check out, you might just want to replace the cap or caps in the high pass section. Otherwise you can use a signal generator to check the output voltage of the high pass section at frequencies above 3KHz with your multimeter on the AC setting. You need to do this with a resistor connected as the same value as the impedance of the tweeter, with the tweeter disconnected so you don't blow it. If the high pass checks out, then you will have to look at the low pass. However that would mean the low pass cap is shorted, which is very unlikely., and the woofer would not work properly.
 
T

the drizzle

Audiophyte
Thank you. I do have a basic multimeter. I downloaded a PC-based signal generator earlier to confirm the issues.

I believe the circuit has 5 total capacitors, 4 inductors, and 3 resistors. I am traveling for the next 2 days to visit family, but I can try to draw the circuit when I get back.
 
T

the drizzle

Audiophyte
I had some time tonight after the wife went to sleep. R3 and R2 read close to their listed values. R1 reads zero resistance but it is in parallel an inductor so that doesn't mean much. Upon closer inspection C5 is bulging so that is probably it.
 

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TLS Guy

TLS Guy

Audioholic Slumlord
I had some time tonight after the wife went to sleep. R3 and R2 read close to their listed values. R1 reads zero resistance but it is in parallel an inductor so that doesn't mean much. Upon closer inspection C5 is bulging so that is probably it.
I would go ahead an replace C4 and C5.
 
T

the drizzle

Audiophyte
OK. If I am going to replace both I think I will need to stick to electrolytic caps to make everything fit on the board. Do you have recommendations for 4.7uf and 24uf caps?
 
TLS Guy

TLS Guy

Audioholic Slumlord
OK. If I am going to replace both I think I will need to stick to electrolytic caps to make everything fit on the board. Do you have recommendations for 4.7uf and 24uf caps?
I would go on the Madisound website, or Parts Express. The electrolytic cap needs to be a NON polarizing type. Most electrolytic caps are polarized, they are no good.
Check back with me before you order.
 
T

the drizzle

Audiophyte
I ended up the capacitors above. After replacing C4, the speaker tested fine so I stopped there. Thanks for the help.
 
TLS Guy

TLS Guy

Audioholic Slumlord
I ended up the capacitors above. After replacing C4, the speaker tested fine so I stopped there. Thanks for the help.
Thanks for the feedback. Since both caps were both in the line of fire so to speak, I would have replaced both. However you can do that later if you have more problems.
 

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