Wednesday, March 19, 2014

The Hard Rock Devil Made Me Do It.

A radio without speakers is about as useful as a dog without a tail. I mean, sure it'll fill in the hole in the dash and tell me the time, but how am I supposed to know when it's happy? Happy dogs wag their tails. Happy dogs rock out. Let's get happy.

I'm going to start off with a caveat. I know about as much about installing car stereos as I do about raising kids. I don't have kids. In fact, when somebody hands me a baby, I'm afraid I'm going to break it or give it some sort of complex. All I'm saying here is don't do what I do without consulting somebody smarter. After all, the last child rearing advice I gave was "Figure out which end to put the food in and call it good."

Power

The Retrosound radio has a reasonably powerful built in amplifier putting out 25 watts per channel. More than enough power to blow up old speakers and just enough for smaller speakers. It won't quite cut it for the stereo I have in mind. Additionally, underpowering speakers has the potential to damage them from clipping and distortion. Of course, you need to play really freaking loud to get to that point.

Amped, Bro.

Power is only a tiny part of the picture. Signal to noise ratio of the amplifier, sensitivity and position of the speakers, I could make up stuff I saw on a box all day long. Frankly, in a small space like a car, power hardly matters. But, you know, if we only did what makes sense, we'd all be driving beige Camries. What you see here is an Alpine MRV-F300 amplifier with 50 watts into four channels picked up for cheap on Amazon. It's inexpensive, small, and the power is a good match for my speakers which are rated for 50 and 60 watts of continuous power.

Wiring an audio amplifier is *almost* trivial. Long big wire goes to the battery (don't forget a fuse near the battery). Short big wire goes to the chassis ground. Little wire goes to the "power antenna" or "amp turn on" wire from the radio (it will be blue). RCA wires for your sound, and regular speaker wires to the speaker. A side note on those wires, I picked up an amp kit made by Scosche on the internets. It's not quite twice the price of the typical kits, but is a surprisingly high-quality set of wires. Wire snakeskin cover over the engine-bay end of the power wire. Real live copper wiring (rather than the more common aluminum). Excellent strain reliefs molded into the connectors. I'm very pleased with the quality and glad I didn't cheap out. Does this sound like a plug? I promise I wasn't paid for it.

Make Some Noise!

About those speakers, in the rear I have a pair of JL Audio TR690-TXi 6x9 speakers rated for 60 watts of continuous power. The large speaker is to eliminate the need for a subwoofer. Sure, they're full range speakers, but high frequencies are quite directional and won't travel quite so well from the rear to the front. Low frequencies though, those travel through everything. You've probably noticed this when you stopped next to that crappy old beige Camry at the stoplight. You know the one: teenage driver, license plate and trunk all rattling from the bump in the trunk. Kids these days...

Anyhow, enough talk, let's build something already.

Baffling
To start, I built a baffle board by tracing what was left of my rotted old parcel shelf onto a piece of 5/8ths MDF and jigsawed out the holes for the speakers.

The New Rats Nest

Underneath the baffle board and covering as much of the axle-hump as possible is more Thinsulate Acoustic. This serves dual purposes of cutting back sound coming through the metal of the hump and cutting back the sound emanating from the back-side of the speaker which tends to cancel out the sounds coming from the front. You can see the amp nestled in there. Don't worry, it has plenty of room to breathe and stay cool.

To fit the fairly deep speakers, I bent the original parcel shelf mounting brackets slightly and installed them upside-down. This gave me the extra inch or so needed for the speakers to clear the hump.

Boom Box

A piece of 1/4" ply shores shores up the front of the parcel shelf and completes the shelf. Thinsulate Acoustic is wedged behind the plywood and eventually got stuffed into the space under the rear seat.

Final Touches

The cheapo eBay carpet kit had a replacement piece for the shelf. Unfortunately it was cut for the original shelf which was noticeably shorter. The rear seat hinges should keep that decently covered. Also, cutting cheap carpet with a dull razor is tough work.

Job's Done!

Now we get to the real reason I bought these speakers over all the other options out there. Plain black grilles. I was after an upper-midrange speaker - perusing the interwebs for Polks and Bostons. Everything has one problem though: ridiculous gaudy speaker grilles. Like giant plastic teeth trying to eat my speaker. After nearly settling on a reasonably tame looking set from Infinity, I found the JLs getting blown out on Amazon that ticked every box on my requirements list.

So, how does it sound then? Better than I had imagined. Far beyond what I get out of my other cars - even the old Nissan with the 10" subwoofer. I'm pretty well convinced now that subwoofers are a marketing ploy - something for high schoolers to put in the trunk of their Camry.

 Sound only coming from the rear means there's no stereo imaging. I've got a vague idea of what to do about that, maybe I'll turn the idea into a plan in a week or two and tell you guys about it next month.

Until then, stay classy.

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