Bjw444

i am not happy with the bass that the b&o sound system is putting out. It is lacking the depth and punch. I was going to add a second dedicated amp/subwoofer combo and have it in the trunk. Can someone please post pictures and a wiring diagram of what wires were used for inputs into the sub.. i would like to keep it as factory as possible.

gguy

I was about to do the same thing for the same reason. Went to several stereo shops and talked to them. Putting a sub in the trunk would have worked fine. They wanted it to have its own amp and every shop agreed that was the only way to go. Trying to wire it into the factory amp was not a good idea. They would have used the factory amp as a signal only, not for power. Anyway, just before I was going to I decided to play with the MMI settings for the sound system and see if I could improve it. For me at least, a couple of changes made a significant improvement. I don’t remember all of them. I set the sub volume to the 3/4 mark. I turned down the 3d effect. I changed the effect (I don’t recall the exact name of this setting) from the “Rear” to the “front”. Those are the ones I remember anyway. Like I said it made a huge difference in the bass in my car and i no longer am going to put a bass in the trunk.

Nostromo

Why don't you just pull the wires that actually feed the sub? Splice them, put a hot swap connector in so you can make it factory again if needed, then tap off that?

While you're at it if you could take pictures of the B&O sub and measure the hole and mounting points for us??? There's a few of us who want to swap the factory sub with a 3rd party sub but haven't gotten around to taking things apart. In my B8.5 I swapped in an 8ohm 10" Pioneer Champion directly in the hole where the B&O was. The B&O amp drove it just fine. Sound was *significantly* improved. Didn't lose trunk space.

gguy

there was another thread on this just recently that may give you some more information. I’m sure not an expert, just the opposite in fact. But I went to several stereo shops including a couple very high end, technology aware and customer oriented shops. Everyone of them, yes every one, (including Crutchfield) warned me very strongly against using factory amp. They all also said, in partial agreement with you, that an amp in the trunk would work well and sound good, just with it’s own amp. They even said a 10 inch single amp in an enclosure would be a big upgrade and would take up little room. My estimates for that being done ran from 500 to 700 bucks, which isn’t bad at all. As I said though, just before having it done I played with the MMI settings and now I am very pleased with the bass in the B&O system. I was pretty frustrated with it before that.

munsabin

Is it not possible to simply use the factory amp and swap out the factory sub with a better quality sub that runs under the same amperage or power as the current one? This seems so logical to me - it's something I was considering looking into. I have the standard sound system and while I'm not happy with it... I'm not losing my sh*t over it

Nostromo

Well sure, they don't want you spending $80 when they could charge you $700 If you ask in the B8 forums this mod hasn't blown a single B&O amp. I had mine installed for almost all 3 years. As long as you're matching the ohms, then it's not going to pull too hard on the amp.

Nostromo

Here's the thread that started in 2013 and is still live: https://www.audiworld.com/forums/s4-...d-diy-2822346/

But yes, it's for the B8.

Bjw444

Thanks guys! I am going to look into replacing the factory sub. I know that I’m able to do the technical work but I would like to know how it should be wired. It seems like from what i have read the factory sub has dual 8ohm voice coils and u can’t find replacement subs like that. Does anyone know if the amp is 4ohm stable? If so i could just get a dual 4ohm 10” sub to replace it with. I do not want to risk damage to the factory steep or any electronics.

Thanks.

Nostromo

I'm suspicious of dual 8ohms. ... they do make subs like that, but they're not common. Really someone just needs to get the factory sub out and look. B8 had a sticker on it: 8ohms. Or you can use a multimeter.

But yeah, a dual 4ohm subwoofer can easily be wired as 8ohms. There'll be instruction in the box. I WOULDN'T run it as 4ohms. Remember the lower the number the more power the sub will suck and overheat your amp.

spinneraf

Hello, I have a 2017 A4 with the B&O and also wanted to replace the sub. I found all the old DIY pages and jumped into it. I opted for the trustworthy pioneer 10" dvc 4ohm, and wanted to use the stock amp. After tearing apart the rear deck, I discovered the new A4s no longer offer a direct sub remove & replace...because it's now a square hole. When I placed the sub in the hole, there was about an inch between the sub and the deck. I suppose you could buy/fab a spacer for it, but this was beyond my desire level, so I put everything back together.

Also, does anybody know what each of the wire colors are on the sub working harness? I'll do some more digging in the forums, but figured I'd ask. I know I found a post saying one of the wires might be an optical wire tied into the MMI and if you cut it you destroy the loop. I need to find that post again to reverify, since it doesn't make alot of sense as to why the sub connection has an optical line. Hope this helps, as I couldn't find ANY posts for 2017+ A4 B&O direct sub replacements.