1989 Audio Upgrade
Iím in the middle of a sound system upgrade in my 89' 5-Speed. I have gutted the old system out of my old car (good quality stuff that I paid a little more for when new but that I don't have to replace now) and am going to transplant it into my 928. Not sure how extensive of a system youíre planning on going for or if you have much radio/electronic experience so I'll just describe my system to give you some ideas. If this is old news to you or others out there than please disregard. I know I learned a lot when I built this system from the ground up the first time and thought I would pass on what I learned to those who have yet to go through it. The system set-up Iím installing is designed to be clean both in appearance and in sound. I'm not going for big booming bass or a lot of flash but instead sound accuracy and stealth which has the ability to really crack if the mood calls for it. I'm sure a lot of the list members know a lot more than I do on the subject of car stereos so if you see a different rout to go please don't flame me for what Iíve wrote and/or suggested. I am after all a mechanical engineer and not electrical.
1. Start with a quality head unit with 2 SETS of pre-out's and the features you want. I use a Alpine TDM-7534 tape deck with integrated CD changer controls and a 6 disk Alpine changer. About 2-3 years old but still a good deck. I would have gone with a Blau for a nice clean factory look but think I'll have to wait until I get wheels/tires and so on. Do not waste money on a head deck that brags about the amount of Watts it puts out on its own. The internal high distortion amps in head decks will not be needed for a clean sounding system install. Besides, that Wattage listed on head decks is usually listed as peak power and not RMS.
2. 1 set of MB QUART 215 for the doors. This includes two 4" woofers and two 1" tweeters and comes with crossovers.
3. 1 set of MB QUART 325 for the back. This includes two 5 1/4" woofers, two 4" midrange, two 3/4" tweeters, and comes with crossovers.
4. Optional is 1 modest yet high quality sub-woofer. I use a Soundstream reference series 10". It helps a lot to fill the sound out with out being thumpy or obnoxious.
5. A good quality electronic cross-over. Audio Control makes some nice stuff. The use of a cross-over allows for a lot more control of your sound system and serves as a great protector of your expensive speakers by blocking harmful highs and lows from getting to speakers which werenít designed to take them. For example the cross-over will only give low frequencies to the sub and block out any high ones that the sub can't use. It does the same for tweeters and midrange separates that can't use nor handle and real low frequencies. The end result is clean amplified signals to the speakers for superior sound with minimal distortion. After all, its not the volume that destroys/blows speakers its distortion and/or inappropriate frequencies. As a final note about cross-overs, many quality amps now come with built in cross-overs.
6. Get a very good quality amplifier. I prefer Precision Power. Try to buy from a specialty stereo shop and avoid the Circuit City and Crutchfield amps if you can.
A 2-channel amp will work OK, will allow nice clean (loud) sound to all 10 speakers but will not allow for the use of your fade control or a sub-woofer. This would work by running both front and back MB QUART left leads into the left side of the amp, for a combined load of 2 Ohms, and repeating for the right side.
A 4-channel amp will work nicely, it will allow for a nice clean (and loud) sound to all 10 speakers and will allow for the use of a sub-woofer but will not allow fade control if a sub is used. If no sub is used than fade control can be maintained by running the 4 MB QUART leads into the 4 channels of the amp for a recognized load of 4 Ohms per channel. This is a nice distortion free set up. You could also run the 10 MB QUART on the front half (front 2-channels) of the amp as described in the 2-channel amp configuration above and run a sub-woofer mono off the back half (rear 2 channels) of the amp for a 11 speaker system off of a 4-channel amp.
A 6-channel amp (or a 4-channel/2-channel combination) will allow for a very nice clean distortion free sound with available fade control with use on a sub-woofer. Hook up each individual MB QUART lead into its own channel on the amp and run the sub mono off of a 2-channel amp.
I run the 2 sets of pre-outs form the back of the head deck to the cross-over though high-grade and highly-shielded RCA cables (these are not the same ones found on the back of your home stereo, these are specially designed to block the electrical interference generated by cars, they cost a bit of money but wonít act as the weak link in your nice set up). The cross-over breaks down the signals into different high, mid-range, low, and sub frequencies and sends them to the appropriate amplifier inputs via another set of RCA cables. The amp amplifies the incoming signals and sends them to the appropriate MB QUART cross-overs and sub. To house the amps, cross-overs, and CD changer I designed and am in the process of building a new custom box that screws down to the floor board behind the rear seats. The box is going to be very stealthy in appearance and when color-carpet-matched should look like a factory part to the unassuming observer. For substantial weight reduction, I've designed the box to be easily removed for A-X and drivers-eds (but hopefully not for would be thieves...I hope!...guess thatís why I pay all that insurance...) When I'm finished I'll have to post to the list to let everyone know how it turned out. I'll have to provide pictures and design specs on the system to those interested.
I've left out a lot of detail and I see I am rambling on and on. Just wanted to give a quick over-view. If you enjoy working on your car I strongly suggest that you build your own system. The experience is very educational and when you do it yourself you know its done correct and you learn a lot in the process. When that 19 year old kid is installing your system between joy rides heís most likely doing a sub-standards job. I may be off base on this one, and was 19 myself once, but I have yet to see a stereo shop do really nice work on an install on any thing but their own cars. Sorry to any of the good stereo shops owners/workers/19-year-old list members out there that I may offended. I also worry that when they see a 928 drive up the install cost will mysteriously go up dramatically. If you do it yourself, make sure to use quality wires and parts. Make sure to solder all connections, heat shrink them, and follow up with electrical tape. Make sure to use a good heavy gauge power and ground cables for the amp(s) that are properly fused and located close to the positive lead of the battery. I also probably wouldnít try to just add new speakers to the existing factory amp/wires. This would not be good for the new speakers nor the old amp. Finally, make sure to shop around and buy quality stuff. You can find a great deal on last years stuff if you look around enough.
Sorry for the length and I hope this helps some people out there.
89í 5-speed w/ 53K on the clock and getting higher every day. I canít stop driving this car! Everywhere and in every condition!
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