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      03-28-2013, 03:14 AM   #1
makkan00
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Drives: F36
Join Date: Dec 2011
Location: Essex

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Technical details on Alpine retrofit Kit

There is not a lot of information on the Alpine kit on the internet and no one is sure about the specifications of it.

Lately, some forums members asked me if the drivers / speakers of Alpine kit are any better than L7 mids? I could not answer it as I did not install any alpine kit yet.
I was waiting for the alpine kit coming my way for installation and getting a chance to test the amp. And finally one forum member contacted me to install the alpine kit with the L7 under seat drivers.
Here are quick photos of installation:






L7 underseat driver




OEM connection where signal splits to underseat and front speakers



Comparison of hi-fi tweeter (blue tags) to alpine kit tweeter (white tags)

Comparison of hi-fi rear speaker (blue tags) to base rear speakers (white tags)



Here are few things learnt;
1- Alpine retrofit manual suggest 2.5 hours of installation. If two BMW technicians are working on your car, then it is possible, otherwise 2.5 hours are not enough for a clean installation. You could do installation in 2.5 hours but quality will compromise. When connecting new wirings, seats have to come out otherwise you may not be able to connect the cables properly. Leave 4 hours (minimum) for yourself and if you are installing L7 under seats, then 5 hours. It took me 5 hours to complete the job including coding and that is without a break.
2- I have said it multiple time that coding is must. It takes out the DSP/ equaliser settings for base HU and expands the upper and lower frequencies. To a layman person, sound improves instantly.
3- Mids and tweeters are connected in SERIES and not parallel. Most of us think that BMW may have connected them in parallel to reduce the final impedance to have more overall sound. But its the opposite. They have connected mid and tweeters in series which reduces the sound output from mids and tweeters, and sub get comparatively more power to have balance in the sound.
4- During installation and testing, sub channel produced 39.6W clip free sound (50Hz), and speaker channel produced 25W (1000Hz) but at 6 ohm final impudence since mids and tweeters are in series (and their coil resistance was 6 ohms when measured). So, its 4 channel amp with 40W@4ohms each.
5- I’ve installed it on pre-LCI car with professional HU. On that HU, clip free sound is two clicks less than max volume and soft clipping is 1 click less than max volume. This is pre-LCI headunit + Alpine kit’s clip free abilities tested with O-Scope.
6- BMW has used 6db xovers (passive) for mid – tweeter splitting and 12db xovers for mid – sub xover (in the amp). From the little experimentation, xover point b/w underseats and mid is 150Hz, whereas xover b/w mid and tweeter is 3-4.5 Khz. It is not easy to test these and hence I gave a range for mid –tweeter xovers.
7- After reviewing all this, Alpine kit is like a hi-fi sound system (except rears and under seats). Power rating of drivers is similar to hi-fi. That makes it clear that drivers / spakers of L7 are superior.
8- In this particular car, we have also added hi-fi rear speakers to have balance in the sound and they worked well.
9- On pre-LCI headunit installed with Alpine kit + L7 underseats + hi-fi coding, sound seemed balanced when treble was at +4 and bass at +2. (its subjective)

Overall, it is an improvement over the base HU. This kit is worth of every penny you pay. Sound quality is 9.5/10 if installed with L7 underseats. Sound is so balanced and you can hear bass, mid bass, mid clearly. The only weak point is treble / upper end. And that is more to do with Pr-LCI professional HU. I strongly believe that in LCI Headunits, they have improved the upper end spectrum and treble is a lot better (speaking from personal experience and I retrofitted LCI headunit in pre-LCI car).
So, if you do not know a lot about the sound systems and do not want to spend fortune on your sound system, then this should be starting point. For an average person who likes to listen quality music, this kit should do the job. Remember L7 and hi-fi coding is MUST to imply my findings.
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