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An explanation on the MOST MMI system and why Nav MMI is different than non-Nav MMI for sound..

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An explanation on the MOST MMI system and why Nav MMI is different than non-Nav MMI for sound..

 
Old 12-25-2008, 09:16 AM
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Default An explanation on the MOST MMI system and why Nav MMI is different than non-Nav MMI for sound..

In a recent, previous thread it was asked why having the Nav pkg would have any effect on sound quality, i.e the B&O audio system found in the Prestige trim.

The "full" Audi MOST system uses all digital signal processing via a central control box in the trunk and fiber optics signal processing in the car for all MMI functions including audio. The NAV system uses the digital processing which requires the use of the full MOST design. Those w/o the NAV system, do not have fiber optics and the MMI processes are in the head unit instead of a trunk mounted central control module. The non-fiber optics (non-Nav) cars process the audio in analog while the full MOST systems w/fiber optics, process all signal including audio in digital.

This why there is:
a) the MMI location difference with and w/o Nav (console vs dash) and
b) why there is a different AMI iPod cable for those with and w/o Nav. (see recent forum discussions on AMI cables)
The AMI cable for those w/o Nav use analog output pins from the iPod vs the digital output pins for those with Nav.
(Actually, the non/Nav version AMI does get the other data digitally, i.e. iPod menu options, etc).

B&O's DSP has nothing to do with Nav or no Nav other than how the signal is processed from the source in the car. All amplifiers will process the final output signal in analog so the speakers can process the sound. It's the rest of the signal path that that can be analog or digital. For example, there's various digital processing that takes place with the B&O surround. It's the back and forth transposition that cuts down on the quality. The fewer the conversions, the better. A full MOST system has at least one less analog to digital and back again)conversion to make.

Digital will always have the edge on audio processing - the more the audio signal path is digital (and the fewer conversions), the better the dynamic range, signal to noise level, frequency response and overall "tightness". (CD vs analog tape, records, etc., to oversimplify).

The difference in an A4, non-Nav, analog B&O system without digital processing is nominal but can be noticeable with the digital source like an iPod or CD that we use today, particularly with demanding material, i.e. bass response. I'm an audio nut (and in the biz) and compared Prestige B&O systems, with and without Nav. I can hear it. Not everyone can or will care.
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Old 12-25-2008, 11:22 AM
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Default What "processing" are you talking about?

All audio compact disc players have internal digital-to-analog conversion. The 1's and 0's recorded on the CD are digital but stereo amplifiers and loudspeakers are analog, hence the necessity for conversion. The most common brand of converter used in the manufacture of the typical mass-produced Japanese CD player is Burr-Brown. That is all you need for basic stereo audio from a CD source.

High end CD players typically have two sets of outputs: one set is analog from the player's internal digital-to-analog converters as stated above, i.e., the analog outputs are connected directly to the inputs of a stereo amplifier which drives stereo speakers. The second set outputs the digital stream of 1's and 0's from the CD via a digital cable without conversion. You would prefer the digital output if you are an audiophile and you own a separate high end digital-to-audio converter unit with much more computer power than the typical CD player's internal converters.

A third type of "processing" has developed with the popularity of DVD movies and home theater. A DVD movie is embedded with vastly more digital information than an audio CD including video and multiple channels of audio. Again, most home DVD players have two sets of outputs: analog, which enables you to watch the movie (or play an audio CD) in stereo; or digital. You would use the digital output with a separate digital signal processor unit to enjoy the multiple channels of audio (from a like number of analog amplifier channels/speakers) in various available surround formats ranging from Dolby Pro Logic to true 5.1 and 7.1 surround. Such a separate digital signal processor unit typically contains the ability to tailor the audio to accommodate individual tastes with catchy "effects" selections like "jazz", "concert hall", etc.

I have no clue how all of that fits in with the Bang & Olufsen audio-only system in a B8 Audi. To me, car audio is a stereo thing. I want the finest quality stereo amplifiers and speakers I can get but I have no interest in surround, "jazz", "concert hall", etc. effects. It appears to me that the non-navigation Prestige package would suit my audio needs just fine but I am open to suggestions.
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Old 12-25-2008, 12:36 PM
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Default iPods, flash drives, HDs all use pure digital files for output - no conversion has yet taken place

like a CD. (Not sure how a CD is handles with a Nav pkg A4). That's one less conversion to take place in all the electronics prior to the amps and spkrs which convert to analog.

The non-Nav (non-full MOST) has to convert to analog right from the source and process the audio as analog all the way to the spkrs. If you have the B&O, there is additional conversion back and forth through the DSP circuits if no Nav vs direct in digital to the DSP w/Nav. DSP is unavoidable w/B&O and unrelated directly to the MOST digital system.

B&O w/o or w/Nav still will be processed by the DSP circuits. (The DSP is optimized for the A4 and is designed so you can center the stereo to the driver, front seats or total car for all passengers. It also uses DSP to mitigate noise in the car i.e. road noise, etc. While there is a surround component, it's fully adjustable for surround delay or can be reduced to none - there are no home theater type settings as you described as such).

The B&O sounds incredible and is by far the best factory audio system I have ever experienced. Others who have it agree. Having Nav w/full MOST digital processing (I'm not talking about DSP here) allows for the very best sound from source to speakers, building on already a terrific system.
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Old 12-25-2008, 01:59 PM
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Default Can't say I agree with that

I have two iPod docks at home. One is connected to an integrated stereo amp and the other to a stereo preamp--both via analog cables. The only digital-to-analog conversion is internal within the iPod itself.

There is also no external D/A conversion when the whole world listens to their iPods via headphones.
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Old 12-25-2008, 02:28 PM
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Default Re: Can't say I agree completely with you either...

My understanding is the iPod has two outputs within the Apple iPod connector. Both analog and digital.
Your computer uses the digital output (and input). As does the MMI via the AMI cable (on full MOST systems w/Nav).
Most playback devices use the analog outputs which have already been converted in the iPod as you state. The headphone jack has ALWAYS been analog only.
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