SUB and AMP wiring on import

[GordonT]

I was wondering if anybody knew how the Amp and sub is wired on an import MKIV (7 speaker system).
Ive just fitted a new head unit, but connected it using an ISO connector.
Does the amp under the passenger seat power the speakers and the sub????
Where is the sub wiring on the loom behind the dash???

Gordon T 93 MKIV.

[DArby]

Craig Martin would be your man for that..

I'll get a message to him, and hopefully he'll come on the BBS and help out

Dean..

[Paul Booth]

If it's anything like mine, it shipped with two complete wiring setups (no I couldn't believe it either); one circuit connects to the amp which drives all 7 speakers and the other is what you connect the ISO adapter to, and it only drives the 6 speakers direct (no sub-woofer which is driven from the amp only).

I spent a few hours with the wiring schematics and gave some thoughts to:
- using a replacement amp of the same approximate physical dimensions
- making a mounting kit to fit it into the same location as the stock unit under the passenger seat
- hybridising the wiring harness in the dash to accommodate the connections direct to the amp location from the ISO connectors.

None of it is a big deal and the Supra's wiring loom is pretty easy to deal with once you get passed the various intermediate relay/junction boards concealed behind such places as the kick panel, etc.

I had a practice by rewiring the SVA-required rear fog-light circuit to utilise the steering column switch as the enabling point (via a relay) instead of the nonsensensical head-light linked, 1kW red warning light, abortion it came with.
I found the general wiring layout and accessibility to be generally ok.

Of course, that was all before I decided to try to make my TT 'appear' showroom stock (within limits - who can stand that front number plate spoiling the leading edges?).

I'm not sure if my experiences can help but I'm happy to contribute scanned schematics with appropriate wiring hi-lighted.

[Alex]

Err... sorry to sound dim but what Sub in a jap spec MKIV? I thought I just had 2x tweeters 2x front component and 2x 6x9 rears.... Are you telling me I have a sub mounted somewhere. The amp has been removed. But the person who did it was kind enough to leave the wires so as I would have to go to the trouble of removing and replacing them.........


Alex H

[Paul Booth]

Certain models (apparently) have a speaker 7 mounted behind the centre of the rear seat; or towards the front of the car looking from the open tailgate.

It is only driven from the amp which powers the head unit when wired in circuit.

If you connect to the ISO blocks, power is fed at that point but you only get to drive the standard 6 speakers. If you connect to the amp, it provides the power up to the head and drives speaker 7 (if fitted).

If you go to www.MKIV.com and work your way through the wiring diagrams (remembering to transpose left/right locations), you can  see what I mean.

[matt]

Alex

The rear spkrs are only 6.5's.......... despite the huge cover......:-(

[Phil Wall]

I have the seven speaker system, but think it  is crap.

It is time for an upgrade.

Any ideas?

I dont want to loose boot space!

[Ash]

That's basically the same conclusion I came to shortly after buying my MKIV a few years ago.

My basic criteria was a system that would be as stock-looking as possible, i.e. boot space retained, rear seats in place and the stock interior mouldings. (I wasn't interested in winning any sound-offs, or anything like that.) The accent was on clarity, more than anything.

The system would have to produce good drum and bass (I do like D&B), yet I could still listen to my favourite Motzart and my wife could hear her favourite Celine Dion, et al. ^

I spent about a week looking at the whole thing in theory. The interior of the car was removed and the stock system was analysed to see if any part could be retained and used in the new system. However, as I say, I concluded that virtually the whole of the stock system would have to be junked. The only components retained were the stock in-dash tweeters. ^

I split the new installation into 3 basic units: amplifiers, speakers and head unit. I looked at each unit and closely analysed what type of component(s) would be necessary in order to fulfill my basic system criteria.

After looking at head-units of various makes, I settled on the Alpine 7944R. The only problem was the light silver front-panel surround that I felt didn't go with the charcoal grey finish of the dash. This issue was solved by purchasing the dark grey panel surround of the 7842R head unit which is a direct replacement.

So that was the head unit sorted.

Next came the speakers.

I felt that 4 good-quality component speakers, coupled with two 8" sub-bass speakers together with the stock tweeters would be sufficient to reproduce the kind of sound quality and volume I required.

After toying with various speakers, I eventually settled on the Clarion SRS1651's for the 4 component speakers (though I later played around comparing them to the equivalent Focals). The Clarions are rated at 100 Watts RMS and are very well made. They will reproduce just about anything you throw at them, as will the Focals. ^ ^

Two of the Clarions were located at the rear behind the speaker grill, either side of the rear seats. They were virtually a direct fit. The tweeter that went with each speeker was simply mounted alongside the main speaker, both of which were covered by the grill. The crossover unit was mounted in a suitable place behind the quarter panel (plenty of room). ^ ^

The doors are a little more tricky. What you have to do is junk the stock plastic soundbox. Then make a fibreglass panel that fills the space in the door (that is left when the soundbox is taken out) and provides a mounting face for the new, larger speaker. The mounting face has to be aligned with the speaker grill on the trim panel. Such that when the trim panel is replaced, the speaker is lying at the same angle as the speaker-grill, central with it, and just a few mm behind.

The tweeter was mounted on the trim panel about 11 o'clock to the speaker. The crossover box can be mounted towards the bottom right of the door as there is space here between the outer trim panel and the metal of the inner door.

The stock in-dash tweeters can simply be connected across the output of the amplifier. So fitment is simply a case of finding the wires and routing them to an appropriate connection point.

As regards the sub-base speakers, I finally settled on 2 8" JL Audio units. There is a space between the back of the seat and the spare-wheel well, that is about 8 inches across (front to rear). A tailor-made fibreglass enclosure was made to fit this space in order to provide a solid mounting for the two speakers. The speakers sit side by side and are flush with the boot carpet. Some minor cutting of the body was necessary to make room for the speaker magnets, but nothing that would remotely affect the integrity of the shell.

Next came the amplifiers.

Finding room for the 4-channel amp to drive the Clarions was a little tricky. After several days of sitting looking at the chosen amp (Alpine MRV-F505) and wondering. I worked out that it could be fitted at the rear left side.

The amplifier sits crossways (i.e. left to right) just under the boot carpet. I think I had to cut away a little of the metal where the fuel-pump ECU sits, in order to make room for the wiring. But I simply re-located the ECU a couple of inches further along. The amplifier is held in place by a tailor-made fibreglass enclosure that not only supports the amp. but takes the place of the whole stock polystyrene moulding that runs along the left of the spare wheel. ^

The amplifier to drive the JL's (MRV-T505) sits under the passenger seat.

The sound, as you can imagine, is streets ahead of the stock system and it all looked virtually stock as per my original criteria. The only difference, visually, were the sight of the 2 flush-mounted JL speakers behind the rear seats and the head unit.

I did worry a little about heat dissapation of the heatsink, on the rear-mounted amplifier, as the boot carpet was directly resting on it. But testing revealed that while it did run hotter, when the boot carpet was down, it was well within specification. So I just left it.

All in all, it turned out to be a great system. And I honestly feel it is about the best that is possible without changing things like interior panels and that kind of stuff. ^

Yours,
J ^

(Edited by Ash at 10:29 am on June 30, 2001)

[Phil Wall]

Thanks once again,

I have already junked the Toyota stock head unit, but will probably change that part of the system every couple of years.

I just want speakers that will deliver, not interested in SO systems.

I have looked around for something to fit in the silly 7th speaker slot but with out success, ditching the whole unit is a good idea.

I will go and have a listen to the speakers you mention, to see if they meet my criteria.

As regard to the rear and door enclosures did you use the standard units as a patterns for the Fiberglas replacements?

[Ash]

If you want speakers that will deliver then simply go for the Focal 165-K2. They are the best 6.5" component speaker available.

As regards your fiberglass question the answer is no. The two component speaker fitments, either side of the rear seats, virtually slot in. But the doors are tricky and so too is the tailor-made box to house the 2x8" subs.  

If you wish I can email some pictures that I'm sure will help you see what I'm trying to explain.

Yours,
J

[Phil Wall]

Thanks
Some pictures would be very much appreciated.

[GordonT]

Well in the end, I cant be bothered with this wiring any longer so ive removed the amp and sub... now all i need to do is decide what im going to replace them with... tell you what... that stock amp is BIG, what on earth is in it... feels like its cased in concrete...