[RyanGphoto]

I've read through nearly all the threads but most are for coupes or m2s. Anyone have specifics on hifi (not hk) audio upgrades in the vertical?

I know you have to remove the rear seats also to get to the rear speakers. So what did you guys replace the stock rears with?

Anyone do an aftermarket sub in trunk somewhere?

Anyone use the underseat space for other subs?

Would a 6.5" fit under there and sound good?

Thanks everyone.

Ryan G

[jv92red]

In our cars the the HK is what other chassis codes call HIFI. So for our cars there is either HK(HIFI) or the standard base system. And for our cars the main difference is that with the HK there are separate tweeters in the sails and a tweeter in the center and separate tweeters in the rear panel.

First off, disconnect the center altogether, both the tweeter and mid. This "center channel" as BMW calls it is just a summed L+R mono signal and certainly not how a center channel is done properly. Because it's a mono signal it will just pull your Left/Right imaging off. You're better off with it unplugged which will create a phantom center. Done right the center channel should be ONLY be fed center information in the music (left and right only information filtered out) so this requires a DSP to process this and feed that pure center information to the center channel. Not to mention depending on the freq response you may want to dial in some time alignment with it as well.

Rear speakers is much more of a personal thing. Some people want rear speakers to fill in the sound and/or for the enjoyment of the people in the back seat. My opinion is that without using DSP to dial in the time delay and level properly, you'll risk pulling the front image back. Ideally, you'll want to locate the sound stage as much in front of you as possible. You're better off using these two channels to power a sub in the back.

So that brings up the under seat subs. They're 8" and not that good at being subs and are ok at being mid's. Stock amp feeds everything below what it gives the 4" door speaker to the underseat subs. Ideally, the underseat subs should be band passed using a crossover so that they handle right where a rear sub is low passed up to where you high pass the 4" door speaker making the underseat subs now dedicated mids creating a 3-way front stage.

Depending on the amp or amp and DSP solution, to start if you're just doing a 6-channel amp I would dedicate the front 2 channels to the front (front two channels are split using a passive x-over so you can have separate tweeters), 2 mid channels to the under seat woofers (band-passed) and then the last two channels bridged mono (if possible) to a 10" sub. There are pre-fabbed corner fiberglass sub boxes you can get that will accommodate a 10" and even a 12" sub I believe. There are plenty of members who have done sub boxes in the back or corner-loaded fiberglass units. Check out Musicar in Portland Oregon or even a ebay seller out of the UK: "Visual.Ice" for those corner-loaded solutions.