E60: Unbearable rattle with new Alpine install + shonky fix.

No sooner have I got the Alpine install sounding heavy in the E60, it shakes some trim loose and begins to cause the world's most annoying rattle. At first it was barely audible and only at high volume. Now it's all the time and louder than ever, all music and even low volume. 

It turned about to be the plastic trim-panel behind the centre arm-rest. I've stuck some foam-sponge into the gaps around it for now and hopefully this will help, but it will need something more like Dynamat at some point.

The low-end rumble produced by the E60s stock-subs, amplified again through the Alpines is shaking panels loose on a very well built car. There is a 22mm thick carpeted MDF panel behind the rear-seats that forms the back of the boot and the front-facing subs are driving straight into it, which already muffles the bass considerably and gives vibration in the cabin. I have read posts where large holes are cut into the MDF in front of each sub to get the bass through, but I can't see that helping vibration and and am reluctant to cut the panel yet. Turning the subs to face away from the rear-seats might help the vibration but I doubt it'll make the bass sound any cleaner and am loathe to expose the sub-cones to loose luggage and lose space by bringing the amp / x-over out onto the boot floor. Again, some sort of sound-matting such as Dynamat will need fitting around the boot and between the rear-seats and parcel-shelf to iron out the remaining hum. As for getting more bass through, the best quick advice would be to open or remove the 'ski-hatch' if your E60 has one, sadly mine does not.

The optimal settings I've got so far since taking RCA-feed from the stock-subs is to have the iDrive bass set to +3 or 4 and the X-over on less than a quarter gain, as the low-end frequencies are just so loud on the Alpines. The low-mid frequencies don't really get to the subs at all though and this where the stock-system needs to take over, but turning the bass over halfway on the iDrive is over-driving the subs and there's no choice but to keep turning down the x-over gain. Hopefully I can turn the x-over back up a bit again now the rattle is sorted.

E60 Audio: TSK TD-22 Speaker Level Converter (X-Over) - How to fit.

If you're running an external amp using the audio feed from your rear speakers then you will be getting the full range of frequencies through your subs. An after-market head-unit with an RCA output, or some amps, will have a x-over built in that can be set to only allow bass frequencies through. If your amp doesn't have one and you don't want the subs to sound awful with your BMW's stock system, an external x-over block is what you need.

In my case, the Alpine V12 1kW amp I'm now using has no Gain (volume) control either, so the addition of a x-over means I can turn down the booming subs without affecting bass going to the stock speakers. The cheaper Toxic 1kW amp I was using in the E39 had both gain control and a built-in x-over, so I could run the subs in balance with my system. Sadly, the 4-chan Toxic amp was never loud enough and any attempt to turn it up would cause the car's whole sound system to trip-out, which I cover in this post, and this really doesn't work in an E60 so it's high time I got around to sorting the matched Alpine amp.

X-over blocks used to be large, expensive things used only by pro's and had more controls than the head-unit itself. Now however, there are loads of smaller blocks available, many designed just to convert a speaker-feed into low-freq RCA. I went for the most popular unit amongst the BMW forum guys, a T.S.K TD-22. Not sure if they're all made by one supplier, but these same looking kits can be bought almost anywhere - I got mine off eBay of course, a snip at £5.95 delivered. 

The instructions are a little vague to say the least and mainly in Chinese and broken English, I have written them out in THIS POST on Panabloga, but here is a better version:

Red: 12v Switched - The x-over needs its own power that turns off with the ignition.

Blue: Remote on/off - Tells the x-over to turn on only when the amp is powered up.

Black: Ground - Connect to earth.

Grey: Right speaker + wire.

Grey / Black: Right speaker - wire.

White: Left speaker + wire.

White / Black: Left speaker - wire.

I joined the red and blue wires together and crimped them both into the amp remote wire coming from the cigar lighter, which is 12v anyway. I cover fitting that in THIS POST. I extended the Ground wire and earthed it to the same place on the body as the amp, rather than into the GND socket on the amp itself as suggested. The speaker wires are pretty short and the only place a +/- audio-feed can be drawn from is where the wires go to the speakers themselves at either side of the parcel-shelf, so I extended both of these into the boot and mounted the x-over block next to the amp on the sub-box.