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1000% Jake
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Discussion Starter #1
Well, I was just reading n2x4's thread about a headunit free stereo install, here: http://clubroadster.net/vb_forum/showthread.php?t=29676

I did something similar a while ago and wrote it up... but didn't post it here. So I'm just going to copy and paste straight from my blog. Whee!
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When I bought my car 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 cockpit with the top down, and I needed whatever I put in to play pretty loud.

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.

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Yeah, I need a blanking plate, I guess. It doesn't bother me. Anyway, there it is.
 
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Looks good! I've been thinking about just relocating my headunit to under the seat or something. No t so much because I'm worried about theft (although it is a plus), but mostly because my headunit throws off the classic vibe I'm going for in my interior.
 

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Premium Member
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I see you're not using a line out from your MP3 player, so is it safe to assume you set the gain on the amp and use the MP3 player itself for volume control?

The headunit-less setup is what I've been yearning for since getting my MX-5, but whenever I look for amps with a remote gain knob (I use a line out from my audio player of choice) it's $800 JL amps. That's too much money to waste on audio for a lightweight, cheap roadster imo.
 

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looks good wonder how the sound compares to a setup with a good quality headunit with the same speakers?

I see you're not using a line out from your MP3 player, so is it safe to assume you set the gain on the amp and use the MP3 player itself for volume control?

The headunit-less setup is what I've been yearning for since getting my MX-5, but whenever I look for amps with a remote gain knob (I use a line out from my audio player of choice) it's $800 JL amps. That's too much money to waste on audio for a lightweight, cheap roadster imo.
you almost definitely shouldnt have to spend that much for a remote gain knob ability
 

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1000% Jake
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Discussion Starter #7
I see you're not using a line out from your MP3 player, so is it safe to assume you set the gain on the amp and use the MP3 player itself for volume control?
The amp has a gain screw, from no attenuation to infinite. You can pretty much use any level input, and yes I use the software volume control on the MP3 player.

Basically turn up your device to full, then slowly wind up the gain on the amp until the speakers are just starting to distort. Then you know you can't accidentally set the volume too high.

Even this basic amp has gain and a variable crossover with a switched bypass. Also has a bass boost circuit which isn't actually bad. It has to have these features to integrate into a larger system - which is what it was designed for, after all. It's only a two channel amp.

I should take a picture of the controls when it's light out. I can't imagine similar amps not having these features. No, you should not have to buy a megabuck JL!
 

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1000% Jake
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Discussion Starter #8
looks good wonder how the sound compares to a setup with a good quality headunit with the same speakers?
Well, the head unit I pulled was not 'good quality' in my book. I can tell you right now that given that my amp weighs slightly more than an entire head unit, it's going to be able to play louder and with significantly less distortion. You simply can't pack 60 watts RMS per channel into a head unit, not with any reasonable distortion characteristics.

Besides, what do you think that weight is? Heatsink, for sure, but also big hefty capacitors and beefy ICs that will keep distortion reasonable at the power levels you need in a open-topped vehicle.

I should really take the cover off, but eh. Harman makes good stuff for the most part, and really the weak link would be the speakers. They are pretty much crap tbh. I'd have to significantly upgrade them to even be able to hear distortion in the amp. Remember that my source material is lossy compressed... I have honestly been very impressed with the detail I get with this setup. For the money it's way better than a similarly priced HU.

I wouldn't say the same about the tiny chinese amp. I haven't heard it, but it's almost certainly just a single IC bolted to the inside of the case with the bare minimum of supporting componentry to drive it. It'll sound reasonable enough I suppose. I would honestly like to hear it, but it's unlikely I will buy something like that.
 

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i love my setup i can take it to about 17-20 on the alpine HU volume scale (out of 30) before i get "distortion" though it really isnt distortion its the door cards rattling from the speakers... though adding dynamat around the speakers helped tremendously. this is but a minor nag compared to w/o the dynamat.

On a side note ive been thinking about completely redoing the door cards to get rid of the rattle from them, anyone have any suggestions on a more rigid material and how much work is involved in completely redoing them instead of the usual recover.
 

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SuperMOD
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I've been wanting to do this since I got my Miata only I'll probably put the amp in the trunk.
 

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I should take a picture of the controls when it's light out. I can't imagine similar amps not having these features. No, you should not have to buy a megabuck JL!
Well I know any amp will have a gain control, but what I'm talking about is remote gain control --a volume knob attached via a long cable if you will. With my line out, the software volume control does nothing.
 

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Very nice! I plan on upgrading my amp to a similar unit at some point. I'll probably end up installing it on the passenger footwell next to the ECU.
 

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1000% Jake
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Discussion Starter #14
Thanks!

I considered the trunk, but there's so little room back there already. At some point I'd like to install subs in the tunnels running to the passenger compartment, so I didn't want to use that space either.

Running power from the trunk to behind one of the seats is easier than you think. Ridiculously easy, compared to a traditional battery location in front of the firewall. Then, the center console comes out with like four screws and running wires up underneath it is trivial.

The only drawback is that the passenger seat can no longer travel to the back of the slider when the seatback is tilted back at a specific angle. Usually the seat is tilted back farther than this, so it's not an issue. I'll have to update this when I install race seats. Might be a bit more of an problem depending on the shape of the seats.

I was also interested in getting the weight of the amp as low in the car as possible. There isn't room under the seats, or I'd go there.

Gotta say I'm happy with it. Easier than many head unit installs I have done. Now, all I need to find is a super cheap MP3 player that I don't feel paranoid leaving in the car...
 

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Nice set up. I did something similar on my car but i get this whining noise on the speakers that goes to a higher pitch when i accelerate and then disappears at a certain rpm. I think it has to do with the power or ground, but idk..any suggestions? Oh and its a pioneer 800w 4 way hooked to rca splitters/3.5mm Y to rca/ipod
 

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Sounds like a ground loop.

You can re-route your grounds, or you can get a cheap ground loop isolator (assuming that you used RCA cables for signal to the amplifier).
 

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SuperMOD
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Sounds like a ground loop.

You can re-route your grounds, or you can get a cheap ground loop isolator (assuming that you used RCA cables for signal to the amplifier).

Anywhere I can find more info on this? I have the same problem on my other car.
 

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I'm running an aux from my cell that splits into an RCA, into a RF p450.4 amp that goes to two Polk db651 in the doors and a Polk db1240 in the trunk. Sounds great. I got a top slashed to get to a worthless cd receiver so I went headunitless.
 
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