silvergray951

I should say right off the bat that I'm not much of an audiophile so I don't need an amplifier with the name 'dominator' in the title
But I do want to install a modern head unit in my '04 C4S and have selected a Pioneer MVHX560BT Digital Media Receiver. This means I need to replace my Bose Amp which in my C4S is mounted in the bottom if the frunk to the right of the spare wheel. I have ordered the AutoLeads harness adapter from the UK. What I would really appreciate is a recommendation for a (modest?) amplifier small enough to be mounted in the stock location and which would allow me to drive the same speakers that the Bose currently does. I'd rather not mess around with cross-overs etc ... and am willing to sacrifice a little fidelity in order to achieve a more straightforward installation. Any recommendations?

fpb111

Sorry I can't help.
But that is the first time I have heard the words "MOST" and "Easy Replacement" used together.

silvergray951

Agreed - but on the face of it, this should be simple. If I get a small amp that mimics the functionality of the Bose, then I can connect the appropriate speaker wire pairs to the new amplifier using the Autoleads adapter. Connecting the new head unit to the Amp will be simple ... I really think the only marginally complex issue here is getting an Amp most (excuse the pun) similar, functionally and dimensionally to the Bose amp.

chamilun

I bypassed the MOST system, and wired into the speaker connector as well.

on my pre-MOST Boxster, using the factory amp, the sound was actually better. So go figure

bal

Are you using the factory speakers? If so, the Bose amplifier is specifically adapted to process audio for the factory speakers. Replace the factory speakers and I expect you will be in for a pleasant surprise.

nymart

I think you are still going to have a problem due to the impedence of the BOSE speakers. Specifically the SUB which is really 2 speakers at 1 ohm per. So unless you can find an amp that is stable down to 1 ohm, and fits into the frunk space, you are still going to have to rewire the SUB. It's an easy thing to do but just know that you are likely going to have to do it. The dash, doors and rears are all 2 ohm each so as long as your amp is stable at 2 ohms, which almost all are, then you will be fine with those speakers. Also, note that you are going to have to find at minimum a 5 channel amp and getting one as small as the BOSE amp might be a challenge. Even with 5 channels, you will either lose the rear speakers or have to rewire them to run off the head unit, which is likely only stable down to 4 ohms...Hence the reason MOST and easy are not usually used in the same sentence. For the record, I used an Alpine 5 channel amp when I did my 04 C4S but moved it to the "shelf" on the passenger side of the frunk.

6ta1

there is a wiring adapter from auto leads to bypass the amp.

you have to buy it from amazon Uk

do a search, or go to my build thread for more info.

silvergray951

Thanks all for the advice - I'm beginning to understand the complexities :-)
I like nymart's approach - summarized as:

- Select a 5 channel AMP (like an Alpine MRX-V70, perhaps I can find a more compact one...).
- rewire the sub box speakers in series to get the assembly up to 2 ohm impedance which the AMP can drive off its Subwoofer channel. This leaves 4 channels.
- Rear side trim panel speakers are 2 ohm, run off the Amp.
- Front door speakers are 2 ohm, run off the Amp.
- Rewire each pair of dash speakers in series to bump the impedance to 4 ohm and use the head unit to drive them.

ditto

If you are going to remove the dash speakers, you might consider replacing the speakers altogether. If the grills are the same as my '99, the speakers from a pair of Polk 4x6" plate speakers fit with a bit of work. The tweeters almost drop in as an exchange but a Dremel and some epoxy is needed for the midrange. Cost is $55 for a pair. Getting the screws out of the grills is a pain - the windshield is really close to two of them so you need a special screwdriver setup. A bit clamped in vise grips works but is tedious.

Class D amps are really small and super efficient. They aren't cheap though.

silvergray951

Would I need to remove the dash speakers to rewire them in series? I am planning to reuse the original speakers, for a while at least to keep this project manageable. I assumed I would be able to rewire the dash speakers in series at the point the wires currently connect to the Bose Amp? Come to think of it, can I do the same thing for the the Sub Speakers?

FLY996

Is the rewiring of the Bose Sub is done internally within the box? The reason I ask is I have a Bose sub box which is screwed and glued together with a high-strength epoxy...I can remove the screws but cannot open the box due to the adhesive....

ditto

Good question. My system was the HiFi not Bose despite what I wrote in my signature so I am not sure. However, I doubt each speaker is individually wired to the frunk amp. When stock mine had a pair of wires (signal and ground) to each location and crossovers (a resistor) between the tweeter and midranges.

pfbz

Even though you have two components, that is still considered one 'speaker'. It has a passive crossover (simple capacitor to block low frequencies from going to the tweeter and a resistor to 'turn down' the tweeter a bit). Only when doing very high-end multi-amp systems with active crossovers would you ever wire a tweeter directly to an amp...

By 'wiring in series', where you asking about wiring the stock bose 2 ohm front speakers in series, like left in series with right, to create a four-ohm speaker? No, you don't want to do that...

Here's another Polk plate speaker hacked on to the stock Porsche dash speaker grille

silvergray951

I rather expected them to be 2 separate speakers, each with a set of wires running to the amp - but that looks to be incorrect . So it looks like I'll also need to swap out at least the instrument panel speakers to allow them to be 4 ohm and this driven from the HU.

I have attached a schematic of the Bose (680 option code) sound layout I thought was helpful - can someone point to a wiring diagram for the AMP?

Amended plan:
- Select a 5 channel AMP (like an Alpine MRX-V70, perhaps I can find a more compact one...)
- Replace both dash panel speakers with something like Polk Audio DB461P (4 ohm) and use the head unit to drive them.
- Rewire the sub box speakers in series to get the assembly up to 2 ohm impedance which the AMP can drive off its Subwoofer channel.
- Rear side trim panel speakers (actually a combination of midrange and tweeters) are 2 ohm, run off the Amp.
- Front door speakers are 2 ohm, run off the Amp.

silvergray951

This schematic seems to be most often quoted and points to all '12 speakers' Porsche quotes. IMO this should be seen as 8 speakers, 4 with integrated tweeters...