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Created: 14 Oct 2010

Last Updated: 15 Oct 2014

This article describes the various audio systems found in the W211 E Class and the W219 CLS Class.  The information applies to the R171 SLK class also, however a few of the links to the retrofit kits are only for the E and CLS Class.

These models have audio "technology" called NTG1 ("NexT Generation 1") which uses a fibre optic network called MOST to interconnect the components.  This was then update with NTG2.5 in mid 2008 for Model Year 2009. The systems are very different.

NTG1 Systems.

NTG1 systems consist of  a head unit (in the dash board), an Audio Gateway (known as AGW), and various optional components such as CD changer, Phone systems, TV tuner and Navigation Processor.

The head unit is the control/display for the system, and the AGW is the amplifier, radio-tuner, diagnostic gateway and the MOST network controller.

In the case of the Audio-50-APS the Navigation processor is built into the unit, in the case of COMAND-APS it is in the boot of the vehicle.

There are various types of AGW, one with a single radio tuner, one with a dual radio tuner and one with enhanced amplifer and dual radio tuner for cars with Harmon Kardon sound system.

In the W211 E class initially 3 Audio systems were available.  The Audio-20-Cassette, The Audio-50-APS - a black and white navigation system, and COMAND-APS the full colour navigation system.

By the time the CLS and the SLK were released the Audio-20-Cassette had been replaced by a much simplified system called the Audio-20-CD. The Audio-20-CD has the AGW built in, so almost all of the wiring now comes to the Audio-20-CD instead of to the AGW.

For NTG1 vehicles without the Audio-20-CD the Audio gateway is in the boot (trunk) tucked up on the left hand side of the car behind the fusebox between the inner and outer wings.

Picture of W211/W219 Audio-20-CD

W211 Audio-20 CD picture

Picture of W211/W219 Audio-50-APS

W211 Audio 50 APS picture

Picture of W211/W219 Comand APS


NTG2.5 Systems

In mid 2008 for Model Year 2009 the system was completely updated with the NTG2.5 system. NTG2.5 systems have the amplifier built into the head unit like the Audio-20-CD - although cars with HK Sound system have additional amplifiers.

NTG2.5 systems all contain Bluetooth telephone systems within the head unit.

Again, there are 3 systems available, The Audio-20, The Audio-50-APS and COMAND-APS.  In this range the Audio-50-APS is a colour navigation system, it is just not as good/flexible as the COMAND-APS system.

These systems (in Europe) can be identified because the telephone buttons are red and green whereas NTG1 has white buttons in Europe. (NB. North American NTG1 vehicles also have coloured phone buttons).

The wiring for NTG2.5 systems is similar to the NTG1 Audio-20-CD system in that all the wiring connects to the head unit - however it is not identical in critical areas such as power wiring.

CD changers or DVD changers are now built into the head unit, and the phone systems work completely differently.

Picture of W211 / W219 NTG2.5 Comand APS

W211 NTG2.5 Comand APS Head Unit

Picture of R171 SLK NTG2.5 Comand APS

R171 SLK NTG2.5 Comand APS

Upgrading the audio system.

Cars with NTG1 Audio-20-CD  (and no Harmon Kardon)

If your vehicle has the NTG1 Audio-20-CD, then it is far simplest to install the new COMAND NTG2.5 (or a NTG2.5 Audio-20 if all you are after is a phone system) then to put in the NTG1 COMAND system.  This is because the speaker wiring is in the wrong place.

These coversion 2 kits sold by Comand Online Ltd (one for cars with existing phone system as the microphone is re-used, and one without) are useful to change over from Audio-20-CD to NTG2.5 systems.  You will also need a head unit and GPS antenna if installing a head unit with navigation.

 Comand Online NTG2.5 Retrofit kit for Cars with Audio-20-CD with existing Phone
 Comand Online NTG2.5 Retrofit kit for Cars with Audio-20-CD without Phone

Under no circumstances plug a NTG2.5 head unit into the NTG1 Audio-20-CD wiring in a E/CLS/SLK as the power pins are in different places and you could (probably will) damage your new NTG2.5 head unit.

If you really must install NTG1 COMAND or Audio-50-APS into a E or CLS with Audio-20-CD then you need to install an AGW and re-route the wiring from front to back of car.

 Comand Online AGW retrofit kit for E and CLS
 Dual Tuner AGW

If installing a navigation processor (i.e for COMAND) then you need the wiring for that:

 Navigation processor wiring kit for E and CLS.

I always suggest using a genuine Mercedes GPS antenna rather than a cheap aftermarket one.

  Genuine Mercedes GPS antenna.

Cars with NTG1 Audio-20-CD and Harmon Kardon.

I have not found such a car, please let me know if it exists and I will try and work out what is possible.

Cars with NTG1 Audio-20-Cassette or Audio-50-APS

If your car has NTG1 Audio-50-APS, then you can change the head unit to a NTG1 COMAND unit (plug and play) and install the navigation processor using the above wiring kit.

If your car has NTG1 Audio-20-Cassette and you are installing Audio-50-APS or COMAND-APS then you should change the AGW from the single tuner version to the dual tuner version so that RDS TMC (traffic redirection) works:

  Dual Tuner AGW 

NTG1 COMAND APS will work without the navigation processor (clearly you will have no navigation functions), and changing the Audio-20-Cassette for a COMAND APS head unit its a 20 minute upgrade, looks very nice, and gives you a CD/DVD player. Changing to an Audio-50-APS is also equally straight forward and gives you Navigation.

If you want to change to NTG2.5 that is possible, but you need to run a large adapter loom from the AGW to the front of the car and remove the AGW.

Assuming your car has no Harmon Kardon then you need one of these wiring loom kits: -

 W211/W219 NTG1 to NTG2.5, cars without HK with Phone
 W211/W219 NTG1 to NTG2.5 cars without HK without Phone
 R171 NTG1 to NTG2.5, cars without HK with Phone
 R171 NTG1 to NTG2.5 cars without HK without Phone

If your car has HK, it is possible to convert it, but you will need a new HK amplifier, a subwoofer amplifer and a complicated wiring loom.  The wiring loom is available by following the link below, you will need to purchase a microphone if your car does not have telephone, which can be obtained from the same supplier:

 W211/W219 NT1 to NTG2.5 cars with HK retrofit kit.

GPS Antenna:

If you need a GPS antenna, we always suggest using a Mercedes GPS antenna. This one can be mounted under the rear parcel shelf on saloon/coupe (above the metal) but also has a long enough wire to run to the front of the car from the back on the Estate.

  Genuine Mercedes GPS antenna.


If installing NTG2.5 COMAND, it is worth considering installing the Voice Recognition (linguatronic) functions. Installation should be undertaken by a professional since it involves removing the steering wheel.

 NTG2.5 Linguatronic kit for E/CLS/SLK.


It is worth having a manual for your retrofitted COMAND system.

Some links to downloadable manuals are available HERE.

You can purchase the NTG1 COMAND manual HERE and the NTG2.5 manual HERE.


V1.2 14th October 2010

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