Chevy & GMC Vans

hello fellow astrofari owners! I have a 1998 Astro LS, with the factory "subs" in the dutch doors. they were crackling and vibrating, so I unplugged them, used the factory speaker leads and hooked them into a 450 watt amp, pushing a pair of 300 watt 8 inch subs in truck boxes. they worked just fine, sounded great. I got a deal on a new 12", 700 watt, Planet Accoustik sub. after installing it, if the volume was turned up, the sub would cut out. I was thinking it was my puny little amp, so I hit the pawn shop and bought a Pyle bridgeable amp. it's just a little amp, only puts out 1800 watts x 2.. lol
anyway, the problem wasn't the old amp, but I do think it's the factory amp. when the sub cuts out all the rest of the speakers are still working just fine..
what I would like to do is use the factory wiring for the rear subs. I'd like to bypass the factory amp/low band crossover so I'm getting the real signal from the stereo.
what does that amp control, just the rear speakers, or does it power the lower front door speakers as well?
if it's just the rear door speakers, what wires are for what? I'm not concerned about the power, I already ran monster cable from the front, but I'd like to be able to use the remote wire if there is one..
anyone familiar with the wiring scheme GM used?
thanks!
Mike
aka niagaradood

the factory amp for the rear speakers is located behind the kick panel on the left side of the second row seat (have to remove seat to get it out). I got mine out with no tools. I would disconnect the rear speaker amp (route the speaker lines around it). the amp just powers the rear speakers. the front speakers get power directly from the HU. IIRC, the rear subs (6 1/2" door speakers) and tweeters (the 4x6's) have capacitors on them that limited the range of sound. there was no crossover, per say. the wires run through the factory amp (if equipped) then to the rear door speakers then to the 4x6 tweeters.
also, are you using the line in on your amp or the speaker level inputs? using the line ins would cause clipping at least, since the factory HU has a built in amp for the rear channels (the external factory amp is just a booster)

I found the wiring diagram for the rear speakers online, so I went ahead and bypassed the factory amp. I have a passive EQ with the line line outs going to the amp. everything sounds great, with the exception of a loud buzz when I turn the power on, and there is a background hum when the engine is running. the hum isn't engine noise, it doesn't fluctuate with engine speed. I can live with the buzz when I turn the power on, but I'd be happy to get rid of the hum..

Check all the wiring, especially the ground wire. A not too good grounding will cause the amps to buzz like that. Running the speaker wires and power wires along the same path can also cause it. Some amps, though, no matter what you do, will always get that noise. I have a Power Acoustik 240watt that does it no matter where or how I wire it up.
There may be some other things that can cause the problem, but, 9 times out of 10, it's the ground wire. (from my 20+ years experience)

Make sure you ground to the floor pan and not anything else.

For car audio, I recommend this comprehensive website.

http://www.bcae1.com/
(be prepared to do a lot of reading and learning)

The chapters that deal specifically with noise are:
- Ground Loop Isolators
- Vehicle chassis ground
- Audio Reference Isolation

Performing thread necromancy here because I want to confirm this info and ask more questions:

So the speaker in the rear pillar trim (D-pillars?) are "tweeters" (or at least mid-uppers) only (though apparently only crudely "high-pass" filtered with caps) and the door speakers are "woofers"?

I'm asking because with my rear bed platform that extends from the middle row right up to the back doors, the door speakers are fairly well blocked. If they're true subs, some of that bass sound is probably coming through, but I'm wondering if it's worth it to keep them or if I should just remove those speakers when I go to pull the cards and gut the doors for extra storage.

I'm also thinking I'd be better off to replace the pillar speakers with something full-range and just bypass (and remove) the factory amp. As it is, I've had to relocate it somewhat away from it's usual spot since I pulled the middle trim panel out to make room for my fridge, etc. Doing a little hacking to remove it entirely wouldn't break my heart.

Are the pillar speakers really 4x6s? or 4" round? I see some people here say 4x6, but Crutchfield only shows 4" rounds as compatible...

I've replaced the OEM head unit with a JVC Arsenal head unit that should be "sufficient" for our needs, with regards to amp power.

Thoughts?

Thanks!

Herbie wrote:So the speaker in the rear pillar trim (D-pillars?) are "tweeters" (or at least mid-uppers) only (though apparently only crudely "high-pass" filtered with caps) and the door speakers are "woofers"?

Yes, the door speakers are definitely subwoofers, not sure what range the speakers in the pillars are.

Herbie wrote: I'm asking because with my rear bed platform that extends from the middle row right up to the back doors, the door speakers are fairly well blocked. If they're true subs, some of that bass sound is probably coming through, but I'm wondering if it's worth it to keep them or if I should just remove those speakers when I go to pull the cards and gut the doors for extra storage.

I think that's a personal preference, it does make the system sound better, but on a camping rig, I would prefer the extra storage.

Herbie wrote: I'm also thinking I'd be better off to replace the pillar speakers with something full-range and just bypass (and remove) the factory amp. As it is, I've had to relocate it somewhat away from it's usual spot since I pulled the middle trim panel out to make room for my fridge, etc. Doing a little hacking to remove it entirely wouldn't break my heart.

I had some older pioneers laying around from my S-10 days and replaced the blown speakers. I didn't remove my amp/rear door speakers, however, the amp only powers the subwoofers and not the rear pillar speakers. I threw up the wiring diagram https://sites.google.com/site/astrosafa ... ereotapecd if you don't have the GM Techline eSI.

Herbie wrote: Are the pillar speakers really 4x6s? or 4" round? I see some people here say 4x6, but Crutchfield only shows 4" rounds as compatible...

They are definitely 4x6, or at least that is what I put in mine.

I pulled the speakers in my rear door as soon as I started the camper conversion, I figure when parked I relax/setup camp out of the sliding door side under the awning anyway, so they would have been worthless for me. I crammed that space with a bunch of misc crap that I probably didn't need, but any extra space is a good thing in my mind, my vote is to toss them, then make a nice clean storage area for me to copy, cause I left it jagged metal and all .

Sorry to revive an old Thread, but y'all gave me an idea for a different retrofit from previous consideration (see "Safari SLE upgrade speaker question")! I've already planned on Dynamatting the Dutch doors in my M11006, and the aftermarket has more durable multichannel amplifiers available than came stock as part of RPO UM6; I basically want to retrofit a modest improvement on RPO UL0 (using a 1 Factory Radio 638.01007C). The Lanzar® MX462 three-ways are still on the shortlist, and some of the available multichannel amps should have suitably steep crossovers to blend the new subs into the MX462s' bass roll-off.