[TMP]

     Featured on BIMMERPOST.com

It's strange the M135i project manager didn't mention this in his interview, but like the M5 with its Active Sound Design technology, the cabin noise in my M135i is indeed generated as well

I unplugged the sound symposer device (see part below) and the results are astonishing.

First off, the radio sound doesn't work with (same thing happened for the M5 owner who disabled his M5 Active Sound). Car exhaust sounds normal (as you would expect) thank goodness!!

But that low bassy six cylinder thrum, all the way up to the banshee howl is gone from the cabin. Instead, there is a faint choked turbo six with the dump valve being the loudest thing. It's not nice and the car loses that character noise. Really noticeable from 2500 rpm. But really no reason to unplug the symposer device as it disables the car's audio system. This was done just for testing purposes.

Took a video today as hearing is believing!

Symposer Unplugged - I got up to 6-7k revs

Compared to the 'normal' sound...

I plugged it back I as soon as I could and woohoo - had my car back again! Also put the windows down and enjoyed the exhaust note in sport.

Never ever ever unplug this box (on the top shelf, above the audio amplifier)

[GBR1]

Originally Posted by TMP

I unplugged the Symposer device (below) and the results are astonishing.

First off the radio sound doesn't work with it unplugged. Car exhaust sounds normal (as you would expect) thank goodness!!

So random question, does the sound change with what stereo option you have fitted??

[logiclee]

Might be why the M135i got a free business speaker upgrade.

Cheers
Lee

[TMP]

Originally Posted by logiclee

Might be why the M135i got a free business speaker upgrade.

Cheers
Lee

Good point - but the ones on sale now dont? I wonder if it does sound worse with the standard stereo then...maybe like a 5pot

[hwelvaar]

Personally I don't mind, and I wonder if a HK system would even impove the 'sound' ...

[donaldt]

this is hilarious guys
anyway
I have the HK and the car doesnt sound all that great

I am looking to change the exhaust system to get more noise

[ozinaldo]

This is so interesting! I was finding the stock M135i so much more accomplished compared to 1M, even posted somewhere that it doesn't really need an upgrade like the 1M. So there was a twist to that.

[BM635]

So will improving the speakers be as important as upgrading the exhaust?

[TMP]

Guys remember this is the engine noise inside the car - not the exhaust sound being replicated. The car seems well insulated, so a louder exhaust will not make much difference inside the car IMO.

If the drive with the windows down, the exhaust sounds fab - so everybody outside benefits!

[logiclee]

From the information available for the M5 it seems the Turbo cuts out both low and high frequencies in the exhaust note and again the induction noise is altered so you don't get as much growl. On top of that the interior cabin is very well insulated to prevent wind and road noise and again the low and high frequencies are what are lost first.

So what you hear in the car without the symposer is just the mid section of what a normally aspirated six would sound like with the windows down.

The sound symposer adds back the frequencies that the M department considers are lost by adding a Turbo and lots of sound insulation. A bit like Simon Cowell using autotune.

Cheers
Lee

[donaldt]

thanks for the video,
actually my car sounds more like yours unplugged...
how could I check if mine is not working?

[donaldt]

I think I have located the box, does it sound different at standstill? gonna try revving later

[bimmerjph]

Thats really disappointing that the M135i has it. Why can't they use the generators like in the old Z4 3.0? That way it is actually the sound that YOUR engine is producing.

[WeekendDriver]

I think I read somewhere with a BMW official saying the sound is 90% real and that 10% is to make up for the turbo. Now it definitely sounds like more than 10% is fake. Also why don't they install an induction pipe or something to transmit the sound from the engine compartment instead of generating it digitally?

[bimmerjph]

Originally Posted by WeekendDriver

I think I read somewhere with a BMW official saying the sound is 90% real and that 10% is to make up for the turbo. Now it definitely sounds like more than 10% is fake. Also why don't they install an induction pipe or something to transmit the sound from the engine compartment instead of generating it digitally?

The induction pipe is actuallywhat I was talking about. I don't know why they didn't do that. Space is one possibility I can think of, but its not like the z4 3.0 had oodles of engine bay room either. The most likely reason is cost. Its a lot lot cheaper to program than it is to produce and install a physical part.


One thing I noticed vs the M5 on vs off video is that in addition to making it louder than the M5 it also changes the sound, whereas the M5 does not seem to do this.

Personally I say they should remove some of the sound proofing. Then you eliminate the problem.

[donaldt]

I have just tried unplugging
in fact it doesnt sound all that different on my car (unlike the video posted)
ok the low end growl is cut by about 70%, but thats about it, its slightly not as loud revving up but its not THAT obvious
or do I have a fault unit?
is it possible to volume up the unit or something?

[donaldt]

yea I missed how they did it on my Z4 3.0, I simply removed some foams in the duct and the car was growling
however I think the problem is that on the Z4, there was some nice engine noise just not enough of it
as for on the M135 there was nothing nice about the engine noise so they had to generate some
but I would expect BMW engineering to come up with a smarter solution than this

[TMP]

Originally Posted by donaldt

I have just tried unplugging
in fact it doesnt sound all that different on my car (unlike the video posted)
ok the low end growl is cut by about 70%, but thats about it, its slightly not as loud revving up but its not THAT obvious
or do I have a fault unit?
is it possible to volume up the unit or something?

What stereo option do you have?

(You cant adjust the symposer)

[donaldt]

HK

[donaldt]

could there be a fault with the HK system?
I tried again and there really doesnt seem to be much of a difference with and without the unit, only very slightly

[TMP]

Originally Posted by donaldt

could there be a fault with the HK system?
I tried again and there really doesnt seem to be much of a difference with and without the unit, only very slightly

Perhaps you could try another local m135i?
Maybe they are tuned differently for different markets....

I have the business upgrade stereo that was free on UK cars upto Dec

[Karazy]

Sure hope this does not end up on the future M4.