PLease help with subwoofer issue

[Njboyd24]

Just updated my system with 2 Kicker comp SVC 12s that came together with a ported box and hooked them up to a JBL CS300.1 amp. The subs are rated at 150RMS @4ohms and I have them installed parallel. The amp pushes 300rms so I’m prettying sure my setup is fine. Turned it on and one of the subs out the box sounds very clearly blown. When I remove it from the box, the other sub sounds fine. I hooked my meter up to check the voice coil and it’s reading perfectly at 4 ohms. Inspected it visually and it looks and feel so brand new, no weird resistance from coil, no tears in cone or anything obvious. Hooked it all back up to make sure my connections were good and same result. Checked the impedance coming out the box to the amp and I get the correct 2 ohms. So what gives? What could be wrong with the one sub that makes it sound so distorted yet the voice coil is reading correctly?? Trying to decide if I should just purchase another sub or if it’s possibly an easy fix?? Thanks for any help!

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[RobGMN 5,000+ posts]

Just updated my system with 2 Kicker comp SVC 12s that came together with a ported box and hooked them up to a JBL CS300.1 amp. The subs are rated at 150RMS @4ohms and I have them installed parallel. The amp pushes 300rms so I’m prettying sure my setup is fine. Turned it on and one of the subs out the box sounds very clearly blown. When I remove it from the box, the other sub sounds fine. I hooked my meter up to check the voice coil and it’s reading perfectly at 4 ohms. Inspected it visually and it looks and feel so brand new, no weird resistance from coil, no tears in cone or anything obvious. Hooked it all back up to make sure my connections were good and same result. Checked the impedance coming out the box to the amp and I get the correct 2 ohms. So what gives? What could be wrong with the one sub that makes it sound so distorted yet the voice coil is reading correctly?? Trying to decide if I should just purchase another sub or if it’s possibly an easy fix?? Thanks for any help!

Did you test the bad sounding sub by itself, or just the good one?
Static resistance is not impedance.
You could simply have a defective sub where the voice coil interferes only when a dynamic tone (like music) is played through it, yet doesn't interfere with a simple "push test".

Try to isolate the suspected bad sub. Then do a return-exchange if it acts wonky.

As an aside, I had a very similar JBL amp that I bought to replace a vintage Rockford Punch. It was a "300" series. It had trouble running a single 12"/4Ohm sub in a sealed box. Would go into auto-protect with heavy bass passages.
I bought an equvalent Rockford Class D amp and am running two 12's in parallel and can play loud enough that my scalp itches and it doesn't break a sweat.

Moral of the story: Make sure your amp is not creating problems.

 

[1aespinoza 10+ year member]

possibly an easy fix?

Play the bad sub free air to see if it makes noise. It may be easier to isolate the issue by watching it play.