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Old 11-17-2008, 10:35 AM   #1
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Factory Stereo/Amp/Speaker question - rear speakers

my car is a 2000 base.

it came with a "hifi" stereo option, but did NOT come with rear speakers. the prior owner added a rear speaker kit, but I don't think it was the porsche kit - it looks like a custom job.

My car appears to have speakers up on top of the dash and in the doors. I have the factory CDR-220 head unit. There is what appears to be an amplifier in the front trunk up against the firewall just behind the spare tire.

when I turn up the volume on the stereo - I feel like the sound quality is great. it goes plenty loud for my needs. sound quality if great too. I really don't have any complaints.

i do, however, notice that I never really can tell that the rear speakers are even there. I started playing with the fader/balance controls and have shut off the front speakers and run the car SOLELY throught eh rear speakers.

the sound volume coming out of these rear speakers must be 1/4 of what comes from the fronts. it sounds like they are not getting much power. is this a sign of blown speakers? even if I flip the seats forward, so there is absolutely nothing obstructing the sound - they don't sound very loud at all. if I turn up the strereo volume as far as I can - it gets louder - but the sound quality is not that good. it almost sounds like the sound is muffled....

I do NOT know how these cars were wired from teh factory - but I do know that my front speakers are all "tied' together. in that the door speakers and the dash speakers fade/balance together - so they are all coming from the same source. if I fade to front left - both the front left door AND dash speaker play. I can't isolate them.

I wondered if it was possible that the amp in the trunk is running all the front speakers (door and dash) but that the rears are running only off the deck and getting not enough power??

i have no idea how the factory amp is wired/setup - so I don't even know if that is possible or not.

i also don't know how I could check for this - without taking it to a stereo shop and having them look at it...

for those of you who have added the rear speaker kits - do you run the rears off the factory amp? just the deck? do you feel the rear sound volume to be a LOT less than the fronts?

on my car isn't not even close - the fronts speakes are so much louder than the rear shelf speakers - that to make the rears loud enough to really hear - the fronts wind up so loud that they start distorting... so basically, to make the stereo sound "right" you have to keep the volume at a point that you can't even really hear the rear speakerrs at all...i'm sure they are making sound, but it's so low that they might as well not even be there.

any suggestions on how to rewire my system or fix this?

w/out getting an "expert" to look at it - i figure it could jsut be how it was wired? it could be that the rears need to be amplfied? or they are not wired up right - maybe they are not getting any power from tyhe amp?

i figurd since I have an OEM headunit and amp - those of you famliar with those setups would be able to figure out the most likely way these speakers were added - and it might speed up the diagnosis...

my honest gut is that the amp is running the fronts AND the rears and maybe my rears blew out? i honestly don't know the symptoms of blown speakers - so maybe that's not it?

thanks for any pointers...

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Old 11-17-2008, 11:35 AM   #2
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The rear speakers are really just for "fill" like in a home ent system. They won't blow you away, they just help "pull" the sound stage back towards you. Otherwise, it's front heavy and focused just under/behind the windshield.

Regarding the rear speakers, it sounds like the PO just wire them off the h/u. You can double check this by looking at the larger of the 2 connections on the amp. I'll bet there are 4 pin slots empty (5, 15, 6, and 16).

Your amp, in the front trunk from the factory is a 4ch by 40W (4x40). It puts out 40W max, the head unit has built in amp with 18W max. Thus why the system sounds unbalanced. Plus the rears are only 3" or 3.5" (OEM rear speaker kits were 3", some aftermkt providers made 3.5" rears). You can transplant a 6x40W amp from a 996 into your system to power the rears. This would require getting an amp w/ the same architecture as yours (either M490 or M680 - sticker on amp or option sitcker under front hood will tell you which you have - plus the M680 has a DSP controller just above the batwing in the center console). Then you'd have to pull the h/u and disconnect the rears and run an extension to the front trunk amp. PNP, an aftermkt rear speaker kit provider, sells/has the extensions.

Regarding the fading, etc., the Dash speakers are considered the front channels, the rear speakers are rear channel. The door speakers are driven by combining the front and rear channels. Thus, if you fade either all the way front, they almost completely cut-out, same for rear. Door speakers are only mid (semi-low) as there's a filter built into the amplifier.

Speakers by locations:
dash - components (4" and a .75" tweeter) - 4 Ohm
door - 5.25" woofer (using the term loosely) - 2Ohm
rear - either 3" or 3.25" - one pair per side should be wired in parallel 4 Ohm. If wired in series, you can get a little more out of them by switching to parallel.

A lot of people, me included, have upgraded the speakers in the car. Although you are happy w/ them thus far, you'll find they really lack clarity and ooophm. Lots of details are in the DIY section here. Also, it can be difficult to procure a 6x40W amp. There are lots for sale, but IMHO, anything over $50-75 you'll be better off just going aftermkt w/ an amp that fits your needs.

Hope I answered all your questions. If not, plenty of info in the DIY section - just search on speakers or amp ugrade, etc. Good luck
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Old 11-17-2008, 12:16 PM   #3
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I have a 2000 Boxster. I added the rear speaker kit and I am very pleased with the sound. I brought it to an auto store and had them install the speakers and attached all to the factory amp. I know they had to purchase some type of attachments so that everything would work together. I took out the porsche stereo and added an after market pioneer.

I wish I could be more technical, but I am not very mechanical. Just wanted you to know that it can be done.

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Old 11-17-2008, 02:40 PM   #4
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thanks for the info.

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