Diagnosing and repairing JBL front speakers: 2018 Limited

I recently acquired a 2018 Limited with the JBL audio package. More than one front speaker sounds blown, so I am wondering if it could be the amp that is bad. Rear speakers sound fine, and I could just live with that, but the Hands-free phone system uses the front speakers exclusively and they sound really bad no matter how I configure the speaker output. Would really like to fix it without rebuilding or replacing the whole system.
Is this a common problem?
Is there a trustworthy place to take it for diagnosis?
I don't want to try to fix it myself; can anyone share experiences and costs for similar repairs?

 

Here’s the score:

you can check speakers with a meter quickly. You can check the amp by looking for dc voltage (you should have MINIMAL, like less than 50milli when warmed up, 20milli at startup). If you have an oscilloscope you can look at the wave for clipping at low volume. Keep in mind that if one speaker kicks it the adjoining speaker will not play as the circuit is now broken.

blown speakers usually make some (horrible) noise still. Totally dead is after elongated abuse, the suspensions typically let go before the leads blow up (in a properly sized system). This can help you triage.

Best bet is eBay for a used replacement. Replacing the system is a fool’s pursuit, you’ll spend big bucks for a proper build, and anything less will feel like wasted money.

 

Err speakers are AC voltage.

I'd honestly just find a good working on and move it to one that sounds like crap and see what it sounds like. I'm not sure if the rears are the same ohms as the fronts.

Or a good reason to upgrade.

 

Correct, which is why when there is an excess of dc voltage it is a telltale of issues (dc fed). This is the actual method to check channel integrity alongside a scope test.

amplifiers are quite simple devices

 

Update?