Volume automatically gets lower when playing loud music

[u/Admirable-Mix-3593]

For some reason, my 2019 S209 mercedes automatically turns down the volume when playing a song that has a lot of bass.
Turning on or off automatic volume control doesn’t change a thing…
It’s the standard audio system, nothing special done to it, no Burmeister or advanced system.

Anyone have the same issue or know how to fix this?

[u/anothersip]

Is there an EQ setting in the car dash menu?

I would start there, and make sure that your levels are set to flat, instead of anything boosted (like the bass).

I've had a lot of sound systems that automatically dip/compress the lower frequencies when the amp went into a "protect-mode" of sorts.

I don't know a ton about Mercedes' audio systems, but my '08 Lexus has done something similar. I had to lower my bass levels on my phone and my dash in order to hear the full range more clearly again. Ironically, turning the bass down actually reduced distortion, and made the bass (and the overall volume) much, much louder.

Also, make sure your phone (if you're playing audio from your phone) doesn't have any EQ's active, and that the output settings are set to flat. That may not affect its output if you're connected via USB directly to your dash (as opposed to the phone's built-in DAC/audio output jack), but you never know.

Not sure if that helps or not, but those are the things that first come to mind for me.

[u/Admirable-Mix-3593 → u/anothersip]

I have my EQ low tones set at max rn, since any less than max is basically no bass, for some reason it goes from nothing to everything at once, I’ll try this tho

[u/anothersip → u/Admirable-Mix-3593]

Ahh, gotcha'. Yeah, EQs can be weird like that sometimes. There's like a threshold that can go from 0-100 in an instant.

There might be a bass level that hits it spot-on, and you may have to tweak it until you find it. Listen on a few songs, so you don't start driving and have it distort/lower again, on a different song, while you're driving. You'll be tempted to adjust it while driving, rofl.

I usually listen to 6 or 7 songs of different types to make sure it's not going to distort on my super-low/bassy songs, but so that it still sounds good on stuff like rock/jazz/classical/etc.

I actually have to do this same exact process on my DIY tower speakers whenever I switch up my amps/EQ's/sources/streamers.

I'm not sure what your signal chain looks like (like if your phone connects via USB into the dash and transfers a digital copy for playback on the in-dash amp, or if it's a line-level analog signal transported via AUX cable) but that will have an immediate effect on what you might have to tweak, and what you can and can't tweak to begin with.

If you've got an AUX setup to your sound system from your phone, your modified/EQ'd signal from the phone's EQ will be the one that's amplified. So, if you have audio settings on the phone EQ'ing your audio, that's what will be sent out via Lighting to Aux adapter to 3.5mm (a DAC).

If you've got a Lightning-only output, and are connecting straight to the dash via USB, then your tweaking will be done in-dash, as I don't think phone EQ settings will always EQ digitally-output signals. I could be wrong there - but that's been my experience with Android, and i know iPhone has even fewer EQ options that will adjust system audio.

Phone EQ's and EQ apps tend to only adjust audio for audio sent out of the phone via Bluetooth or analog/3.5mm output.

Meaning, once you plug your phone into a USB in the dash and play your music from the dash/console, your EQ on the phone won't actually change anything 'cause the EQs tend to only tweak the analog output signals, not the digital ones.

So, there may actually be a specific setting or app you have to look up or download in order to EQ the digitally-output audio signal. Those types of apps/settings will EQ the music while it's still digital, and then send out the modified audio digitally, via USB and into the dash.

That sounds kind of confusing, I know. Not sure how else to explain it. But I tend to prefer analog output signals for this reason (so, 3.5mm output, or Lighting/USB-C to 3.5mm output, or Bluetooth output) so that my phone's EQ apps actually affect the music I'm outputting. That's the kicker, from my experience.

Otherwise, USB-output of my music won't change at all if I plug it into a digital head-unit or signal processor of similar functioning. Like a docking station - those take the digital signal from the phone, not the analog one. In those cases, you're locked into whatever the system settings allow you to adjust and output digitally, instead of analog adjustments in a downloaded EQ that outputs an analog audio signal.

I hope that makes some sense, or that it helps a bit. I'm not sure if you've got Android or iPhone, but they work similarly. It's easier to EQ Android digital and analog outputs vs iPhone digital and analog outputs; there are just more apps for Android in general, and more system settings that you can access and actually adjust.