20 Most Recent JBL MR-4 AM / FM / CD 180 Watts Marine Receiver - Page 2 Questions & Answers

Bad or shorted voice coil on sub maybe. If you have two subs try them one at a time to see if it goes into protect mode. Whatever sub does it is bad.

It is very dependent on your vehicle and whether you are using the built-in amp of the head unit or a separate amp. Ideally, I would recommend a good 6.5" component set.

Having them wired in series. Should only be a ground issue.

Lester, probably has a remote.

You need to calculate the amount of amps being driven through that fuse + the amount you need to feed the amplifier. In my Volvo S40 and V70 I had no problems driving an amplifier of the rear power connector, but on my Honda S2000 however I had to create a different connection all the way to the battery line for a smaller amp (connection as in cables, condensers/filters and fuses).

single channel about 1kW output power. About $250 when new. Specs here http://www.crutchfield.com/S-dVhyYWWFkBd/p_115GTO1201/JBL-Grand-Touring-Series-GTO1201-1-II.html

Use a C or D size battery. Get two pieces of wire. Strip each end. Wire one end of each to the sub. The other ends you will place one on the top of the battery and, one on the bottom of the battery. If the cone moves outward, you have the correct polarity. If the cone moves inward(toward the back of the speaker) then you have the polarity backwards

try checking your speakers and/or speaker wires for grounds or shorts. If they check out fine, you have an internal problem with the amp, more than likely blown transistor(s).