alpine mrx 70, ch.4 overheating speaker

Hello Everyone,

I'm looking for some advice, help on diagnosing an issue I'm having after just installing an Alpine MRX-70 amp in my 2012 F150.

Issue:
Channel 4 going to rear right door speaker (Infinity Kappa 682.9cf) with after 20/25 minutes of continuous use, the tweeter on that speaker begins to heat up and eventually produces a burning smell.

My troubleshooting has led me to think there is an issue specifically on that 4th channel as the issue follows the channel not say the speaker/wiring.

Setup and Testing:
Gain for channel 3 and 4 is set to 0 (at 0 it just takes longer to heat up) if I up the gain to say 10% it just heats up faster only on that channel 4. Channel 3 being controlled by the same gain setting shows no issue.

Test 1, I swapped the speakers; the kappa connected to channel 3 and working normally I plugged into channel 4 and that speaker began to heat up.

Test 2, I removal all truck speaker wiring from the scheme and ran a new 16gauge wire directly from the speaker to channel 4 and the speaker again heated up

Test 3, I took that just heated speaker with the new wire, connected it to channel 3 and the temps dropped and no issue was shown, even when increasing the gain to 25%

I haven't put a multimeter to it yet, it has disappeared in my garage :O, but I suspect that channel may be sending voltage down the wire to the speaker and cooking it.

Is it possible to have a bad channel in this way? Before I go down the path of replacing it, I'd like to know why it's doing this?

thanks for taking a look and any help you can provide, please ask any question needed:)

Assuming the Kappa crossovers are connected properly and that the tweeter is correctly connected to the tweeter output, then I'd say your amplifier is producing a lot of high frequency distortion on channel 4.

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thanks for responding,

the crossovers are part of the speakers wiring, so unless they are manufactured wrong I don't think the issue lies there. And also since one of the kappas doesn't have the issue and the other does only on the channel 4, that helps me think the speakers are ok.

I did double check my wiring and all was accurate.

using a multimeter today to check for impedence/voltage variances....channel 3 was pushing out roughly 30/40 microvolts while channel 4 was pushing 500+. Just confirming there is a difference between the 2 channels.

I am assuming you are talking millivolts. 500 millivolts is going to cause your speaker to heat up. Your amplifier has a DC offset problem. Do not play that channel unless you get it repaired.

thanks yes millivolts:) not sure where the micro came from lol

I'm calling alpine tomorrow to set up the repair work. thanks again!