Hi All,

New to Audi -- Just got an 2013 S4. Wow.

Coming over from a 335 where I had a pretty strong audio set up (JL/700/5 driving morel dotecks in the doors -- channels 1-2, 8inch audio systems under the seats (set up as true woofers -- passed them signal from 80-200Hz) -- channels 3-4 and a JL 10w3V3-4 in a custom sealed enclosure driven by the sub channel.

I have the B/O system and it is pretty good. Actually, the imaging and the mid bass and up is actually better than the above system --- pretty sure it has to do with the amount of signal that I was driving up from the floor. That said (and I have seen it in this forum before) the low end is not too strong. Thus, I will be adding my current amp and possibly the sub (if I can get Wicked CAS to make a right side enclosure to hold it) or one of the JL audio microboxes.

The above is all background to my specific question: what should I do with the B/O sub?

One option is to just delete it. This would have it function (I'm guessing) as a passive resonator indirectly driven by the sub in the trunk into the cabin.

Another is to drive it the B/O sub bridged with channels 3/4 of my amp. I have seen in one thread that the B/O amp drives 150 watts into the 8ohm woofer. The JL drives 75rms/channel-- 150 bridged but this is into a 4 ohm load. Is this going to fry that woofer?

Still another is to let the B/O amp drive the B/O sub and just tap the signal and drive the new sub with my amp. My fear here is that I may get phase differences but I'm pretty sure that I'm overthinking this issue.

Neither of these are particularly complicated as long as I turn off the filtering in channel 3/4 -- it has the option of being high pass or band pass. But suppose I get fancy and turn on filtering....

Another choice is to repurpose the B/O sub to be a true woofer and pass it from 80 to 200 or so. If I do this I can use either the B/O amp sub outputs for the input into this channel or I could look for a full range signal -- just not sure which wires to tap.

By my count there are about 10 different questions above. Any advice on any of them greatly appreciated.

 

I have never been a fan of doing partial system upgrades. Every car I've owned since I was 16 years old has had a complete aftermarket system. I would be concerned about using an aftermarket amp on a factory speaker. Factory audio components are normally junk, regardless the prices charged for them. Who knows whether or not the speaker can handle the increased wattage, or whether it might be a wacky impedance? Bose is notorious for weird impedance speakers.
I would probably just leave the factory components alone and add a subwoofer if you feel more bass is needed.

If you encounter phase differences while running an additional subwoofer, there should be a phase switch on the amplifier or you can simply wire the sub deliberately out of phase. I don't think this should be a huge concern.