[chaswyck1]

I think I finally got this straightened out so here's an update. My audio guy has spent countless hours on this project (most on his own dime) because he viewed it as a learning experience and for that I thank him profusely. Yes, the active sound apparently does work differently on the 2 Series than other series.
Set up one: We orignially left the OEM amp in place and put a line converter (Audio Control model Lc6i) between the OEM amp and the aftermarket four channel amp (ARC Audio XDi 600.4). Front speakers were Focal IFBMW-S component speakers). Stock rear speakers and center channel were left in place but unamplified. The four channels of the ARC amp amplifed the front speakers and each of the underseat subs. This produced much improved sound and very good bass but, for me at least, it was too "front loaded". Active sound was louder than stock, but actually pleasantly so.
Set Up 2: The 4 channel amp was replaced with a 6 channel (ARC Audio XDi 1200.6) and Alpine SDS-410 speakers were installed in the rear. All speakers and the subs were amplified with the six channels. OEM amp and line converter remained in place. Center channel remained in place but unamplified. This produced more balanced sound, still very good bass but the problem was that the active sound was booming, especially in Sport mode. Unacceptably and unpleasantly loud.
Set Up 3: This morning we made some significant changes. The center channel speaker was disconnected. The Audio Control line converter was removed and the OEM amp was bypassed altogether (Thank you, Technic for the harness. It worked well and made the job a snap. Highly recommended!). These changes produced cleaner sound but interestingly, the active sound was even louder than before! Before these changes I was convinced that the active sound volume problem was because we were taking an already amplifed sound from the OEM amp and amplifying it again with the after market amp, but this appears not to have been the case since removing OEM amp resulted in it being even louder and significantly so. We adjusted the gains on the aftermarket amp down (pretty significantly) and this greatly reduced the volume of the active sound. It is still louder than OEM, but acceptable. It may also seem louder because now because it is a much cleaner sound being played through much, much better speakers. The amplification of the rear speakers also had an effect on the volume of the AS. If you're listening, BMW, it would be a very nice touch to include a volume control for the Active Sound or even a three position, low, medium and high switch on the module that produces the sound.
Bottom line: I'm very happy with the sound and the volume level of the AS now. It is a night and day improvement over the stock Hi-Fi system and that is a big understatement. I will do a separate review of the Focal IFBMW-S speaker system in another thread, but suffice it to say here that they are excellent speakers, but require some break in. I hope this information is helpful. It was a long and difficult process to get to this point. I would estimate that there was something in the neighborhood of 18 labor hours put into this project, very little of which I actually paid for because my audio guy was determined to get it right no matter how much effort or long it took. That's an unusual quality in this day and age.

[akuan99]

It appears that AS comes out mainly from rear speakers.
Change in gain between front and rear amplification will have effect on AS loudness.
If gain on rear amplication is higher then the perceived AS loudness is louder.
Also removing center channel decreases sound level of signal without AS so this will contribute to louder AS.
Try setting fader control so that front speakers are active and see if this reduces effect of AS.

[akuan99]

Originally Posted by akuan99

It appears that AS comes out mainly from rear speakers.
Change in gain between front and rear amplification will have effect on AS loudness.
If gain on rear amplication is higher then the perceived AS loudness is louder.
Also removing center channel decreases sound level of signal without AS so this will contribute to louder AS.
Try setting fader control so that front speakers are active and see if this reduces effect of AS.

I just realized that fader control may not have effect on AS so it may make it sound louder since you are reducing music signal on the rear speakers.
Nevertheless it will be still a good source of information to see if the fader control has any effect on AS level.

[chaswyck1]

The AS is unaffected by any audio controls, fader, balance, or volume. You may very well be right though about it coming mainly from the rear speakers because the problem didn't surface until we switched from a four channel to a six channel amp and amplified the rears.

[Viffermike]

Very, very interesting, chaswyck. Kudos to your sound guy; anyone in chaswyck's area, use this dude!

The more I hear about this, the more I want to simply eliminate the problem and have the AS coded off. I'm going to wait a week or two before installing my Hertz 100.5 coaxials (front and rear) so the weather warms up and there's less potential plastic-clip breakage. I chose the Hertzs primarily because they're more sensitive than either the Focal ISCs or the Morel Maximos that've been used by others, so the potential for achieving acceptable sound without having to upgrade the amp is highest.

What's interesting to me about this issue is that the factory HiFi setup favors the front speakers significantly, in that the volume output is much higher from the fronts than the rears, even when the fader is used to bring up the rears. The stock speakers are exactly the same in both locations, but it appears that the stock amp limits either the gain or the power output to the rears by at least 3-5db, and volume changes at the head unit don't affect volume output in the rears nearly as much as the fronts.

Now that we know that the AS is primarily dependent on the rears, this limiting makes total sense -- and that a fix with an aftermarket amp is to reduce the gain to the rear channels is absolute proof of it. That's a real shame for those of us who favor clean sound.

I really wish BMW had gone VW/Audi's route by designing an AS system that operates separate from the stereo. With that system, all you need to do is disconnect the transducer under the hood to turn it off.

[hyperzulu]

Have you looked into coding? I know you said you didn't want to remove AS altogether since you liked having it, just not so loud. But while there are no volume options in the values available, there are different settings under Audio Level. For me it shows as Hifi, I believe, but there are Top Hifi, Stereo, Branded Hifi and High End, if I'm not mistaken. Setting to Top Hifi may lower the volume since logically it would be used on a car with the HK option, which has a more powerful amp.