E46 M3 nav+ Hk .. Where to get input for the sub ? Remote/ground in trunk?

Basically I'm not all that familiar with what's under the carpet and panels in the trunk on my m3 and thought if ask before I go in blind to setup my amp/sub.

I know the battery is in the back so I'm hoping ill be able to wire everything within the trunk. Where would be a good location for the amp? Is there room under the panel on the floor in the trunk? Is there a good ground bolt anywhere obvious like a shock mount bolt maybe? Or should I wire the ground on the drivers side where the factory electronics are grounded? My car has the BMW TV option so there is a alpine unit on the tray above the battery.. Possible source for a remote Etc?

The big question is what should I use for the amp input? I have the line converter that turns into rcas into the amp but I don't know if I should use a speaker input from the factory subs pre or after amp Etc or rear speakers?

Tia

You can do a search for "how to put a subwoofer in a BMW 3 series" It will give several links on where to put everything.

Originally Posted by emm3speed

Basically I'm not all that familiar with what's under the carpet and panels in the trunk on my m3 and thought if ask before I go in blind to setup my amp/sub.

I know the battery is in the back so I'm hoping ill be able to wire everything within the trunk. Where would be a good location for the amp? Is there room under the panel on the floor in the trunk? Is there a good ground bolt anywhere obvious like a shock mount bolt maybe? Or should I wire the ground on the drivers side where the factory electronics are grounded? My car has the BMW TV option so there is a alpine unit on the tray above the battery.. Possible source for a remote Etc?

The big question is what should I use for the amp input? I have the line converter that turns into rcas into the amp but I don't know if I should use a speaker input from the factory subs pre or after amp Etc or rear speakers?

Tia

If you're keeping the factory HK system and you're only adding an amp for a sub, then just tap into the harness before it enters the main HK amp on the driver's side for the input signal as well as the remote.

I just used the factory ground location on the driver's side as well. Just give the connector and the metal on the body a little sanding to make sure it gets good metal-to-metal contact.

Where you mount it is really entirely up to you and kind of depends on the size of the amp as well as the box setup for your sub. You can mount it to the back of a seat, to the box itself, to the floor, under the floorboard carpet, etc.

Check out the bsw install instructions. Should tell you everything you need.