TT-S4

I'm still getting familiar with my S4 and discovering things about it.

I like the B&O in my S4, but there are some aspects I don't like.
In particular the sub woofer in the B&O is poorly designed.
The sub can not be turned up too much.
When I do turn it up the read deck vibrates and rattles crazily and ruins the audio quality.

The sub in the B&O system is anchored to the rear deck, and that's an awful location for a sub driver.
By design a sub creates low frequencies that can easily vibrate panels around it, and can vibrate things connected directly to where the sub is anchored.

Today I experienced a problem with the sub, it didn't work after sitting in the parking at work all day, and it was working in the morning when I drove to work.
So, it's possible that there is something wrong with the sub in my S4, more on that in a bit.

The rear deck vibration and rattle is so bad that I have to question what the audio engineer/s were thinking when they signed off on the placement of the sub.
It's pointless to have such higher power available for the sub and system when it's not possible to turn up the sub without completely destroying the overall audio quality.
The vibration created by the sub being attached to the rear deck panel transfers to the cabin, which results in the rear view mirror vibrating making the image blurry.
The same happens to the outside rear view mirrors as well. I can see the side mirrors vibrating to sub bass tones. Not good.

I have an excellent car audio 12" Infinity sub in an old-school box that I may try.
I need to get some specs first, but I should be able to just disconnect the rear deck sub wiring and run it to the Infinity sub.

When I first picked up my S4, on the drive home, I tried to turn up the audio to a semi loud volume to hear the quality of the system,
and the sub created so much rear deck rattle that it's hard to tell if all that vibration and rattle is just the sub location and design, or a sub going bad.
I need to get in the back seat and listen to some sub bass tone generations.

As I wrote above it's possible there is something wrong with the audio system or the sub.
On the drive to work this morning the system was sounding in working order.
When I left this evening the audio didn't so so good. The sub didn't come on with the rest of the system.
I adjusted the audio settings to confirm, and the sub was not working.

I was going to call the local Audi dealer and make an appointment, but I remembered someone discussing how to reset the MMI system.
Knowing that modern car systems are controlled by computer I wondered if maybe something odd happened and the system turned the sub off for some reason.
So I did an MMI reset and there it now was, the sub came back to life.
Very odd.

This doesn't mean I found the actual problem though. I simply found that an MMI reset brought the sub back to life.
But the question remains, why did the sub go out in the first place?
What made the sub stop working?
If I had been playing the system at high volume for a long time I could suspect that there could have been a thermal protection circuit that kicked and shut the sub amplifier off to protect either the sub and/or the amp. But that as the case. My S4 was sitting in the parking lot all day and when I started up the cold system the sub was not working.

I'll update this post when or if I find the problem.

will13k7

probably a software glitch if you reset mmi and it started working normally again. it might not happen again, or not for months at a time. I wouldn't worry about it unless it starts happening frequently.

putting a high powered sub in a box in the trunk will also vibrate your mirrors and everything else if you are really concerned about that.

this sub is way better than what they put in the last generation s4 at least. Its a "shallow mount" dual coil sub versus a traditional single coil sub with a tiny magnet.

TT-S4

Let me preface my post by saying sorry that my response is so freaking long.
Still, I want to be clear about where I'm coming from.
And maybe some of this may help another S4 owner.

It happened again. I've had to reset the MMI 5 times now to get the sub working.
After the last reset yesterday, so far the sub is working.
I can now hear a fuller bass tone, along with a rattling rear deck if I dare turn up the volume with the sub level greater than the 1 o'clock position.
Time will tell though if the computer decides that I don't need any sub bass tones

I just did some reading on how B&O and Audi created and designed this audio system, and I'm not that thrilled with what they've done and how they implemented it.
The whole system seems over thought, and if this is the final result that I'm hearing in my S4, then I am even more pissed that is sounds so lackluster.
16 speakers and over 700 watts of power and I still have to turn the treble up to maximum to get acceptable clarity, and still there's a sub that rattles the rear deck so badly such that the rattling is as loud as the vocals.
Yeah, that's not such a good design.
I've had significantly better audio in systems in other cars, that I put in with just 5 speakers; 2 sets of mid/bass + tweets and 1 sub, each set driven by separate amps and the sub getting it's own.
These days I pay extra for the supposed "high end' audio so that I don't have to tear apart doors, A pillars, carpeting, trunk, and run all the wiring. I've become too old and not so flexible to do all that, so I'm willing to pay for better OEM audio.

As for a sub in a box in the trunk, if there is enough amplifier power and one turns the sub level way up, then yes, of course it can rattle the rear view mirror, panels, and even exterior trim bits.
But to get there that sub has to be cranking at very high SPL, and at that point most people wouldn't want to be sitting in the car.
The sub/box I have would do that when I also had 800 real watts driving it and I cranked the volume level up.

Where a sub is attached matters in regards to vibrations in the car.
Yes, even a sub mounted in a box in the trunk can vibrate things in a car, if one cranks up the power and the sub volume is extreme.
But at low and moderate listening levels, such as enough to overcome road and tire noise at 80mph, there should be no rattling, and no sustained mirror vibration.
The issue with the OEM sub is that even at low and moderate volume levels there is a good amount of vibration in the rear view mirror, and the rear deck will rattle like crazy even easier.
There is NO excuse for how poorly the sub was executed in this system.

I work in video and audio production. I've personally done audio systems in my previous cars. I'm a musician, and I've run audio systems for live bands, and studio recording of bands.
I state that to simply show that I'm not just bitching and complaining for no reason and no basis.

Also, directly compared to how HK does the subs in the 3 series, the difference is obvious. In the BMW, HK mounts the subs under the seats, and they sit inside a well anchored box in the floor.
I even upgraded the OEM subs to get a bit more clarity and punch.
With that system, even with the stock subs, you hear the bass/sub-bass and can feel it's presence from low to moderate to semi loud volumes.
In my S4 I have to keep the sub level down even at moderate volume to keep the rear deck for rattling so badly.
This B&O system does have superior quality tweeter though. To my ears they sound more like silk-dome tweeters, pleasant and not fatiguing.
HK uses titanium domes, and they have the capability to create a high level of high frequencies, but the tone can be brittle in quality and you have to keep the tweeter frequencies controlled or it can get harsh on the years when listening over a longer period.
The tweeters in the B&O sound nice, but there is little control over their level.
I have to set the treble to maximum to get the clarity I want over the road noise. It would be nice to have a bit more to add for certain types of music, but it's at max now and we don't get an "11" setting.

I'm not a bass-head, so I don't crank the sub. I prefer a solid and tight mid-bass.
Sub bass frequencies should enhance the overall sound and not become the most prominent aspect of the overall sound.
I know a lot of generally younger people love to crank up the sub and get that massive pounding, but that only works for certain types of music.
So, for reference, I'm not cranking the sub so that I can feel it hitting me in the chest and compressing my skull.
And in a car like an Audi most drivers aren't looking for that kind of thing.

As I said, maybe there is something wrong with the system in my S4.
For me having a decent sounding audio system is as important as the comfort of the seats. It's more important to have comfortable seats and good audio then what the headlights design looks like.
Yes, I'm harping on the B&O audio system, but as of now I am disappointed with it.
And, I'm not too enthused about having an Audi tech check the system, because they are not audio specialists.
If they can hear something, and their diagnostic computer doesn't tell them there is an issue, then it's fine to them, "No problem found."
I am suspecting that there may be something wrong with the sub in my S4.
A simple test of hooking up my boxed sub might reveal something, or nothing.

will13k7

Wow, yeah, I'd get that rattle and sub checked out by Audi, my bass and sub are both at 5'clock and don't get rattle or distortion until I'm blasting the music, then I just back off a little and its ok.

mplsbrian

If you can find a way to reliably reproduce this issue then the problem will be covered under warranty by Audi. It is possible you have a bad amp, bad sub, bad wiring, etc.

So I would focus your efforts on that, and once you are at a place where you can demonstrate the issue for a service writer/technician, just let the dealer handle it while you drive around an A6 loaner for a few days while they conduct their diagnosis.

TT-S4

Ah. Interesting.
Thanks for that information.

My sub level is set to one notch higher than "noon".
My regular bass is set around 3 notches higher than noon.
The overall bass is fine even if I crank it up.

If I set my sub level to a 5 o'clock level, then even at moderate volume the deck will rattle and buzz and yeah it sucks.
If I crank the volume with that sub level it's just pathetic.

Ok. So it' pointing to a potential problem with something in the system and/or the sub, especially when adding in the complete shut down of the sub for no reason.

When I first heard the B&O audio system it was in a 2012 S3.
I really liked it even at speed. It easily compared to the HK in my, then, 2012 335i Msport.
Overall I thought the B&O was a bit better.
When I did my recent car shopping I test drove some S3s, as I was going to get that model.
The B&O didn't sound as good, but I don't know why.
Then I heard the B&O in an S5 and S4, and both were distinctly better than the S3.
So when I got my S4 I had expectations that my system would be very nice, and then this.

Thanks for letting me know about your own audio experience, it's very helpful.
It's pointing to a problem somewhere in the system, and hopefully Audi mechanical techs can sort it out.
ARGH!

TT-S4

Oh yes, I can easily reproduce the rattling and buzzing. As for the dead sub, at this point it happens when it/MMI decides.

At this point I have to let the techs see what they can find. My hopes are low however, as my experience with modern technicians is that they rely too much on their diagnostic computer to tell the what's wrong.
Intermittent and/or quality of operation in a system often requires an experienced technician who can look beyond the computer's "yes/no" algorithms.

Thanks for the support and suggestions.
I'll update when I find something new.

Versprechen

There's definitely something wrong with your amps or DSP or whatever because no way you should have to crank the treble up for clarity like that. If anything the system tends to be overly bright. And the subwoofer bass IMO is very tight in my A4 and only rattles the back shelf if I crank it past 4 pm and it never rattles the rear view mirror at my current setting of around 3 (with bass around 2). All that rebooting is your red flag here.

TT-S4

I agree.

My recollection of the B&O in the older S3 and other A4 and S4's is that I really like it.
I'm thinking the system's processor is acting up.
I can hear it altering tonal settings while driving, which apparently it's supposed to do.
The overall tone sounds different when I'm sitting still at idle compared to higher speed at say 60mph.
The system information does say that the processors "listens" via built in mics in the cabin and that it will alter the overall tone and settings due to variations in what the mic/s hear in the cabin.

Personally, I would rather be able to turn that "feature" OFF.
I want to control my tone rather the computer deciding to turn the treble, mid, or bass up and down when it thinks it should.
If I could set the tonal preferences I want and then the computer can adjust things due to changes in tire roar, external noise, wind, etc., then that may be ok.
However, to my ears there is some reference the processor is listening for and I can't stand what it does to the overall tone.

Quite often I will be listening to music that I am familiar with, and I know how the EQ should be.
I adjust the limited bass, treble, and sub levels to where it's acceptable and then drive off.
Very soon as I get up at higher speeds the tone gets very mid-range heavy and the tonal quality becomes "wooden", not vibrant but very dull and lacking crispness.
It's very annoying.

I hope it's the processor acting up and it can be fixed.
However, if this is how the system is designed, then it sucks for me, as I didn't know that this system was designed to alter tonal qualities automatically as it's telling me what I should like, as it's based on what the programmer of the system likes, and it seems we don't agree.
That's great for people who don't either don't know about audio or don't care.
For me it's very annoying, so I'm hoping there is something wrong.

I need to get into a couple more A4/S4s and do an audio test drive.
As a person who has worked he whole professional life in technology and video and audio production, I'm still of the mind that technology for technology sake is not a good thing.
Any new tech needs to perform better than what it replaces. Doing "more" doesn't mean it's doing better. Being fanciful "ooh and aahhh" is not always a good thing.
So far, I'm not impressed.

Markster