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Couple of weeks ago, I posted a long message about how I upgraded the stereo in my V70 AWD, using and AudioControl EQX graphic equalizer and a JBL 4 x 50 watt power amplifier. A few people requested more installation info, so here goes...
INTERFACING THE AMP TO THE SPEAKERS
The SC-816 has two multi-pin connectors plugged into it from the wiring harness. These connectors supply switched and unswitched power to the radio, dimmer info, a turn-on signal, as well as speaker connections for all four speaker pairs.
I got my dealer to supply me with photocopies of the wiring diagram for the stereo. It was very difficult to decipher. Then I found out that Crutchfield (800-955-3000) sells wiring harness adaptors made to interface their aftermarket head units into the Volvo wiring harness. They cost $10.00 and they are well worth it. I ordered an interface (Crutchfield part number 120 70-9220 for the 70 series cars) The adaptor comes with an easier to understand wiring diagram, but that's not the best part. The adaptor itself consists of the connectors that mate to the wiring harness. Coming out of the connectors are all of the wires needed for a stereo installation individually labeled as to their function. While I did't use the adaptor in the installation, it provided a great guide for how to hook things up.
My original plan was to do the installation without cutting any Volvo wires. Instead, I wanted to make a harness that would plug into the SC-816 and the car's wiring harness, that would tap off the turn-on signal, power and speaker connections. I searched in vain the connectors that mate to radio, but was unable to find them with wires already attached. You can buy the connector shells and the pins from your dealer, but they are expensive and you need a special crimping tool to put them together. I ended up having to cut and splice the car's wiring harness.
HOOKING UP THE EQUALIZER
Unlike many car equalizers, the Audiocontrol EQX does not have a front/rear fader control. This could have been a serious problem, but there is an easy workaround. The EQX has a built-in cross-over for biamping purposes, with individual level controls and outputs for a full range signal, a high-pass signal and a low-pass signal. I used the full-range output to drive the front speakers and the high-pass output to drive the rear speakers. The default crossover frequency in the EQX is 80 hz, which would have robbed all of the deep bass from the rear speakers. The good news is that the crossover frequency is easily changed, by replacing a plug-in chip in the equalizer, available for ten bucks at decent car audio dealers. I installed the lowest frequency chip available, 30hz. This made the high-pass output almost full-range (you're not going to find many car speakers that go below 30 hz anyway).
The EQX mounts perfectly against the left wall of the glove compartment. There is just enough room behind the device to plug in input and output connectors. You need to make a 6-pin DIN to RCA cable to connect the SC-816 to the equalizer. To avoid noise-pick up, keep this cable as short as possible and use a very high-quality, fully shielded cable. I used Belden 8451, which is the same audio cable used to wire recording studios and broadcast stations.
BALANCING THE SYSTEM
The front speakers in the V70 have a completely different tonal balance from the rear speakers. (Check it out with your fader control). Before equalizing the system, you need to get the front/rear balance set properly to your ear. I tried to make it sound like equal levels were coming from front and rear. Once this balance is performed, then you can equalize the overall sound from all the speakers. See my previous message for the actual frequency curve that sounds great in a V70.
It is best to crank up the input and output gains of the equalizer as high as possible, to feed a very hot signal to the rear-mounted power amp. Then you can turn the input gains on the amplifier down pretty low. This is what makes the system noise-free.
DC POWER
As with any high-powered car stereo, the amp and the EQ should get their power directly from the battery (with its own fuse) , with very large wire (10-gauge is good for up to 200 watts). The ground connection should be made with equally large wire, directly to the something metal on the car.
Hope this helps. I've had my system in for about a month now, and it has made driving the brick a much more enjoyable experience.
--Phil Mastman
1998 V70 AWD
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