rroobbcc

So I took the day off on Monday in order to finally get around to upgrading my stereo. Now before anyone says anything... YES I already have a sport exhaust (Gemballa)... and YES it really sings a great song, BUT... sometimes I want to listen to music, and I want it to sound good.

The equipment list is as follows (including price paid):

Alpine CDA-9857 Receiver ($299)
JBL GTO755.6 II Amplifier ($299)
JBL GTO804 Subwoofers (2 x $59.99)

and a few other bits and pieces...

JL Audio Amplifier Power Wiring ($109)
3/4" MDF for Subwoofer Box ($20)
Monster Cable Speaker Wire ($50)
Black Carpet ($10)
Misc. stuff - screws, glue sticks, etc. ($20)

I think that covers it. So the total is approx. $930.

After suffering through the stock "hi-fi" stereo since buying my car last June, this has been a much anticipated upgrade. While I was looking for a significant improvement in sound quality, I didn't want to break the bank to achieve it. So most of the equipment would probably be considered midrange.

I am still using the stock hi-fi speakers, including the door-mounted woofers. I am driving these in a somewhat unconventional manner with the JBL amp's front and rear channels. I wired the front and rear tweeter/mid units in series and drive them from the amp's front channels. The door-mounted woofers are driven one each from the amp's rear channels. The amp's crossover and level controls are used to properly blend the output for a balanced coherent sound. Simply getting the stock speakers off of the crappy stock amp and receiver made a dramatic improvement in the sound quality.

To fill in the deep bass I went with two 8" JBL woofers. I built the box for the woofers from 3/4" MDF. The raw box was purposely built a tad too big, and was then "sculpted" with a sander until it fit perfectly in the area directly behind the rear seats. So some sections are probably now only 1/2" thick. This allowed me to maximize the internal dimensions, providing the air volume required by the subwoofers.

I spent a lot of time thinking about the right CD receiver, and in the end I never found it. Don't get me wrong, I really like this Alpine unit, but it just doesn't have the right looks for the Porsche interior. In fact, NOTHING does. Ultimately I chose the Alpine for the quality of its features, and the solid feel of the main volume control (some units were just down right flimsy). I will have to learn to live with the looks.

The amp is mounted in the front trunk. As can be seen in the pictures, I still need to finish the false floor under which it will reside. I also need to finish the cover for the rear subwoofers, as well as reroute the amp's power wire and permanently mount its fuse block. I will post additional pics after I get that stuff done.

nycebo

Nice write-up Rob. But tell us: how does it sound?

pchak

Really well done! I think the head unit looks like it belongs.

rroobbcc

Uhhh... good point. Although I did say it was a "dramatic improvement in the sound quality".

But seriously, I didn't expect I would get the stock speakers to sound as good as they do. That said, I will still probably swap them out somewhere down the road. When the time comes I will most likely go the JL Audio route (XR Series, 3-way in front, 2 way in back).

While the subs really help fill out the low end, they are just 8's. Don't get me wrong, they do produce a nice deep bass in the sealed enclosure, but if I was to crank it up really loud they would probably be at their limit. This is not a real issue for me, as I generally listen at a level that would be considered moderately loud at best. However, my serious listening at home is from a pair of Infinity 9 Kappa (yep, they are 15 years old now), which have a total of four 12" woofers handling frequencies below 80Hz. So I know the difference between a pair of 8's and four 12's.

delirium

rroobbcc, nice set up!

How difficult was it to upgrade the Head Unit? I thought cars wit the MOST system was very difficult or impossible to updgrage without revamping the entire system?

rroobbcc

I think people really stress about replacing one of the MOST head units because there is no simple adapter to reuse any of the factory wiring. The head unit itself really only requires four connections from the car. Permanent 12v, Ignition Switched 12v, Ground, and the Antenna. For Permanent 12v I ran a wire (fused of course) out to my power distribution at the battery. I attached my ground wire to the chassis. You could tap off of the factory harness for this as well. For ignition switched 12v I tapped off a switched circuit at the fuse block. For the antenna you need an adapter.

If powering speakers directly off the head unit you would also have to run new speaker wire far enough to tap into the factory wiring, or just rewire all the way to the speakers (the latter of which would be a BIG job, but probably the best). Since I was using an external amp, I ran wire from the new amp and spliced it into the factory wiring after it was disconnected from the factory amp. I plan to actually cut off the factory amp connector a few inches back and add an additional connector, which allows me to plug in the wires from the new amp, or reconnect the factory connector.

To complete the amp and subwoofer connections, I had to run speaker wire from the front trunk all the way back to the sub box, and of course a remote turn-on and RCAs from the head unit to the amp.

I hope that all made sense.

delirium

wow, good info... so if i wanted to power the speakers directly off of the HU, how far do I have to run these wires in order to tap into the factory wiring? Shouldnt those wires also be right up there at the factory HU location & I cann just send signal to the factory amp & then to the factory speakers?

rroobbcc

Not too far. You have to get them as far as the factory amp in the front trunk.
No, the connection from the factory HU to the factory amp is a digital signal, i.e. MOST bus. Speaker wires start from the factory amp.

HTH

joes c4 cab

Nice write up! Looks like 2 10's would have fit in your box in the rear? Was there not enough air space? Thanks for clearing up that MOST mystery - sounds pretty simple now that you explain it.

I too had Ininifi Kappa 9's at my last house - man were those thinks loud and the bass was DEEP. Didn't need a separate sub when running those. Ahhh, how I miss them - new house just didn't have room and we had to go in-wall.

Porsche_Smile

love the system....your alpine looks great! switch out the 8's to 10's......much better

nycebo

Thanks again Rob. I've been thinking of stepping into it piecemeal like you, or just slamming in new speakers all around and have hemmed and hawed for a year now. But, I'm really itching to up the low frequency response (I don't have the Bose sub as it wasn't available in my year) and stronger midrange. As you surely know, the stock equipment really has a sort of hollow and muffled sound. It's not terrible as car stereos go, particularly as I have the DSP upgrade, but it could still be vastly improved. I'm glad you're pleased with your progress so far.

lanny

I never considered using the factory speakers. I am sure with the rest of the system having been upgraded that they sound pretty good. I went with a Nakamichi at first and thought that it looked great in the dash but I had problems with it and ended up with Alpine and it doesnt look as stock but still ok. I went with Focals up front and 10" in the back and it sounds extremely better- the factory systems are just terrible- love your car by the way.

newport996

You have a cab......I did new Focal Speakers, Audison Amp, Footwell sub, and Kenwood double din head unit in my C4 Cab....it sounds AMAZING.
AI Design in New York makes the footwell sub with a JL Audio 8" driver in a custom enclosure.