JBL GT5-A402 Install & Review, sorta

When I bought my Miata back in June, the audio situation in the car was pretty dire. An aftermarket Pioneer head unit with possibly the worst front interface I have ever seen was rattling around in the DIN slot. The previous owner asserted without much confidence that it was indeed in working order. I turned it on, it sounded like it was shorting across the speaker outputs, so I turned it off and never turned it on again. Honestly, the stereo system is really at the bottom of my priorities when buying a used vehicle. The number of clean aftermarket installations are sadly outnumbered by various levels of clusterfuckery ranging from simply cheap components often inferior to stock (which it seemed I had encountered) to hacked up harnesses complete with a rats nest of unlabeled and severed wires.

So I paid no attention to it, and after I discovered that the head unit was held in place by nothing more than the force of gravity, I yanked it out. It was just so much dead weight, anyway.

I toyed with the idea of removing the remainder of the stereo. I didn't want to dedicate a huge amount of resources or accrue a large weight penalty by putting a monster stereo in the car. Besides, that goes against everything the Miata stands for. On the other hand, I wasn't sure I could get adequate performance from simply a head unit and door speakers. It's not quiet in the Miata cockpit.

So, rather than a head unit and an amp, I decided to skip the head unit completely and just use one of the many MP3 players I have lying around. Hey, head units are heavy. I decided on the JBL GT5-A402 for the amp because it was a) two-channel and b) cheap. But, importantly, not ridiculously, awfully cheap. There aren't any absurd and unrealistic wattage ratings on the casing and it comes from a big (very big) and reputable manufacturer, Harman International. In this case branding means it won't be completely crap.

Honestly, the hardest part of this install was getting wires figured out. Yes, the harness had been mutilated. Once that was done the rest of it was surprisingly easy.



There's a tunnel that runs from the trunk to the passenger compartment, and since the battery is mounted in the trunk, the install is almost trivial. No drilling in the firewall.



The amp went behind the passenger seat. Note that if you have a post-1994 NA, the ECU is mounted here. I think. Someone correct me. Either way, make sure what you're drilling into.



I was expecting to find stock speakers in the doors, but it looks like someone put in these poly cone Pioneer units when they installed the head unit. If they're installed with the same level of skill as the head unit, there are wires twisted around the speaker terminals and wrapped in electrical tape back there. At the moment I'm just going to leave them. They don't actually sound too bad, and I haven't figured out exactly what I want to put in the door yet.



I know this install is neither unique nor revolutionary, especially in the Miata world, but I am still pretty happy with it. It fits the Miata ethos. Functional, minimally complex, and light. The amp is very slightly heavier than the head unit that got binned, but I excised about three feet of tangled up wiring and three (yes, three!) inline fuse holders. At the very least, I've reduced the risk of my car burning to the ground in an electrical fire.


As for the amp itself? I didn't tear it down to check out the quality of the components or the packaging. I don't have reference quality speakers to listen to it critically. I can say it has way, way more power than those particular speakers need. It's not supposed to be a flagship amp - I paid $80 for mine - but I'm confident it'll deliver its rated output with a minimal amount of distortion. I've been impressed at how much detail I'm hearing even with the poor speakers and the large amount of cockpit noise. The screw terminal block could be wider and beefier but it's not exactly flimsy. The included mounting screws are the perfect length to mount through about half an inch of insulation and carpet. They aren't self-tapping. The amp has a nice soft turn on feature, but that's hardly ground-breaking or upmarket these days.


So, for a total of right around $100, including the mounting kit, I've added two 60 watt channels. Is it going to win any competitions? Well, I hope not. Does it go louder and cleaner than any head unit? Absolutely. Combined with an almost infinite playlist, the fact that I don't have to carry expensive and obnoxious media, and the fact that it looks like my stereo has already been stolen - this is an unbeatable upgrade for the working Miata.