[GtiGyver]

For fun I was trying to figure out how well the system in my M3 could handle various codecs, from a USB stick connected via a COMBOX and from the DISK in the CIC imported from the same stick.

Seems they are not the same.

Music playback from the USB stick supports:

• MP3 CBR/VBR
• AAC LC (HE not supported)
• WMA 9
• WMA Pro Lossless

Music playback after importing to the Disk-based music library supports:

• MP3 CBR/VBR
• AAC LC (HE not supported)
• WMA 9

What is more interesting however is that when using the COMBOX playing directly off a USB stick, the MP3 codec seems to have a 16kHz cutoff frequency regardless of the bitrate. I checked and the source file did have content up to 20kHz and was encoded at 320kbps.
All the other CODECS would play up to 20kHz unfiltered.



In the music library, same files imported, all files were played back with the full 20kHz bandwitdth, even that same Lame-encoded 320kbps CBR MP3.

[david in germany]

Can you run the same test from cd audio? By the way, THANK YOU!, for taking the time to do this.

[GtiGyver]

Originally Posted by david in germany

Can you run the same test from cd audio? By the way, THANK YOU!, for taking the time to do this.

Good idea. I'll try.

Also note that I did the test using my phone butted up against the left door tweeter.
My car is equipped with the Dirac Individual audio system, E90.

[david in germany]

Mine also has the same system. I have a full TermLab audio suite with RTA, maybe I should run a full sweep as you did. Did you have all the EQ setting set to flat and surround set to off? White noise at 0db gain?

[GtiGyver]

Originally Posted by david in germany

Mine also has the same system. I have a full TermLab audio suite with RTA, maybe I should run a full sweep as you did. Did you have all the EQ setting set to flat and surround set to off? White noise at 0db gain?

The EQ was not flat, and I believe surround was ON.
I was not looking to test equalization though, just absolute frequency response.

Given that all things being equal, I was getting different results in different CODECs at high/lossless bitrates was a surprise though. More specifically that MP3s decoded in the radio had a relatively agressive lowpass filter applied to them reguardless of bitrate whereas other CODECs did not, and on the COMBOX, no lowpass filters were ever applied reguardless of CODEC at high/max bitrates.

[david in germany]

Correct, same setting with different results.
On a side note, I really do not like the surround setting icon the Dirac, logic 7 surround does sound nice but the Dirac is so much more pure sounding with it off.

[GtiGyver]

I checked using audio CDs and Bluetooth SBC and both do reproduce frequencies up to ~20kHz (playback of pure white noise in both cases).

I agree about the surround sound setting. In fact, I stopped using it last week for music.

Unlike the L7 surround modes, on the individual audio system the surround mode is specifically Dolby Pro Logic. This means it really only sounds good for movies/media specifically encoded in Dolby Pro Logic.

[david in germany]

Originally Posted by GtiGyver

Unlike the L7 surround modes, on the individual audio system the surround mode is specifically Dolby Pro Logic. This means it really only sounds good for movies/media specifically encoded in Dolby Pro Logic.

That explains a lot!

[GtiGyver]

Originally Posted by david in germany

That explains a lot!

I tested using some specific Dolby Pro Logic material, and without the surround sound mode enabled, the rear channels were not driven properly.
With it enabled, you can get near perfect LEFT, RIGHT, CENTER and REAR channel isolation assuming the correct material is played.
Of course, there isn't much these days encoded in Pro Logic anymore.
DVDs are typically DD 5.1 which would work (haven't tested) without using surround mode, and as you said David, music sounds quite bad in Pro Logic.