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      07-10-2012, 05:45 PM   #5
Major General

Drives: 340i M-sport AT
Join Date: Mar 2006
Location: Chicago

iTrader: (1)

Originally Posted by VP Electricity View Post
It's somewhat of a specious way to rate it. It's all the individual channels added up, and some of those channels are for the Logic 7 "surround-ish" channels which never get driven anywhere close to full power. Those are some of the speakers which got left off of the vert, thus totalling a lower number. It's entirely possible that the per-speaker ratings are the same in the vert. It's unlikely, but possible that the vert uses a different, analog-input amp (like the "harman/kardon" system in the Mini Countryman, which is really a reprogrammed HiFi amp from BMW

The old Premium Sound amps were using deck-power IC amps for the outputs. The new ones are using Class D from what I hear - so they should have more power, certainly.

You're not going to find an 8.5 driver from anyone. What you're going to need is a different adapter ring (if the speaker did actually change, that is). We have a post out for local F30 owners now, and we hope to be offering validated F30 kits within 30 days.
The rating thing you just wrote is spot on.
That's exactly the problem with these ratings, they don't say how much power is driving what.

But remember, coupes, touring, verts, sedans all get Logic 7 with 7.1 channels.
Look at the specs on that link, and you see that the sedan gets mids and tweets for each channel.
The other variants use only get mids for certain channels and no tweets.
Yes, over all power use will change as there are fewer channels.

Seems surround mode will sound different in different types of 3 series.
But, stereo mode is likely that same or very similar among them.

Here's a guess. Tell me what you think.
Let's take 7.1 for total power. There are 7 non sub channels, and 1 sub channel. But, there are dual subs. So I'll use 9 channels, 7 + 2 subs.
Subs will need more power than any other channel.

If each non sub channel had 50 watts, that's 50 x 7 = 350 watts.
150 watts for each sub = 300 watts.
350 + 300 = 625 watts total.
Hmmm...that's pretty close, and gives the subs good power to work with.

In 7.1 there are 9 channels, and each channel has a tweet and mid. Per channel power is then split between tweet and mid at X-over.
Subs are single, the ".1".

7 tweet/mid channels for a total of 14 speakers + 2 subs = 16 speakers.

In standard stereo mode for music, with no surround processing, there will only be Left front and Right front, Left rear and Right rear, and subs.
50LF + 50RF + 50LR + 50RR + 300Subs = 500 watts for stereo use.
That's not too bad if it does break down that way.

In my last 325i setup I had 125watts rms to each front L & R.
Sub in trunk was fed 425watts rms.
The above channel to sub ratio isn't bad.

Yeah, it would be nice to have adapters. I wonder if my 8" Earthquakes are actually better than what BMW is using. I would tend to think, YES, but I don't know for sure.
8.5" sub is an odd size, but BMW has to source them from somewhere.
If these are one offs just for BMW, then BMW is paying too much to have them custom made.
Why not just stick with 8" or 10"?
Or, maybe the 8.5" is misleading, and it really is 8".