BMW 1 Series: Digital Audio

Digital Audio: BMW 1 Series


Back in the day.. used to be so easy if we wanted a better sound in our car. Change the factory fitted radio, upgrade the speakers and maybe add an amplifier and sub. I can’t remember how many of these Audi A3s I’ve done over the years, it must be hundreds. But what about the modern version?



This car infotainment system has satellite navigation and integration with the vehicle systems; not to mention a full fibre optic audio path with multi-channel amplification and 11 speakers. The specification is very impressive but unfortunately the audio performance is less than satisfactory. The Bose and B&O ‘upgrades’ are particularly poor with weak bass and a flat sounding front end.


The same applies to BMW, Mercedes, Porsche, Mini, Jaguar and others. It is just not possible to change the front end systems and all these manufacturers use a sophisticated fibre optic system or MOST ring for audio. This system is not compatible with aftermarket amplifiers so what do we do to improve the audio in these cars?



Let’s take the BMW 1 Series with Harman Kardon audio as an example.

The BMW 1 Series is a great car, but in my opinion has one of the worst sounding audio systems out there. Naturally we can replace the speakers with the likes of Eton, Audison or XFire; that will make it sound better but we haven’t addressed the real problem of the HK amplifier. This amplifier has been designed for a specific purpose; to make the stock BMW speakers sound OK while protecting them from overzealous use of the bass control. You may have noticed that when you try to turn up the bass the sound gets muddy sounding. This is because the amplifier is not turning up the bass, but instead is turning down the treble.


No, if we want a great sounding audio system this amplifier has to go. But what about the MOST ring and all the chimes, tones and announcements generated by the car, won’t we lose them? What we need is a device that can read the signals on the MOST ring and interpret the different information streams separating out the audio from the vehicle data. This device must be able to play the different vehicle announcements exactly as the makers intended while providing a clean digital audio signal. Ideally it should be programmable so that updates and even different vehicle configurations can be accommodated without the need to change the interface. It should also be capable of being invisible to diagnostic tools to prevent device errors.

So all in all we need a pretty sophisticated device; step forward the Audison Bit DMI.

This unassuming little box is our saviour as it converts the MOST signal to standard digital optical. The really clever part is that it can be reprogrammed indefinitely. The clever engineers at Audison have cracked the code for different car manufacturers which means that we can connect this and be confident that all the original systems will be played perfectly.


Now we have a digital optical signal that contains the audio signal as well as all the chimes and announcements from the vehicle park assist, satellite navigation and bluetooth modules. Now we can start adding the amplifiers that will complement the upgraded speakers confident that they can perform as intended.

In fact this is one of my most common system packages for the BMW 1 and 3 series. The Bit DMI replaces the factory amplifier and converts the MOST signal. The optical stream is then fed to the Audison AP8.9 Bit amplifier. This amp features up to 8 channels of high power output as well as a full spectrum digital audio processor allowing total control over every speaker. I configure it as a 6 channel to drive the door and under seat speakers as a fully active component set. My favourite choice of speaker is the Eton Upgrade system. These German built speakers are fabulous and offer a performance level well above anything else on the market currently. The AP 1D slave amplifier is to run the Audison APBX8 slim sub enclosure in the boot.


The Results

The difference between the BMW ‘upgrade’ audio and the Audison/Eton one is incredible. The bass has far better definition while the front sound stage is clear and totally immersive. Gone are the harsh high frequencies of the Harman Kardon speakers to be replaced with a smooth and sensitive full range sound. Of course a lot of it is down to how I tune the car but that just means that every customer can get exactly what they want.

The same or similar systems can be applied to Porsche, Audi, Aston Martin, Mercedes and others; with just a change of speakers to suit the car. That is not to say that we have a ‘one size fits all’ approach. On the contrary, we look at each installation individually to make sure that each customer gets a bespoke solution. After all, everyone is different; that is where my tuning skills come into play to make sure every car is optimised for the biggest smile!

If you would like to know more about how we can upgrade your car audio system then please give us a call on 01625 432707. Better still, pop into the shop on Sunderland Street in Macclesfield for a chat, you’ll be glad you did.


  1. Hi I’m thinking about purchasing a BMW M135, but would need a decent system, can you give me an estimated price please.
    Cheers wayne
    I currently have the bowers and Wilkins 440w in my jag, this is still not loud enough though.

  2. I have an F87 BMW M2 with advanced BMW sound which is pretty poor, can you quote me for an upgrade please

  3. Hi got a BMW 1 series 2013 need a Good system would you be able to recommend me one and give me quote
    Plz thank you

  4. Hi, I have a 2019 BMW 1series 5 door Shadow model (118i petrol) with the Harman Kardon sound system.

    Can you supply a quote please for the Audison/Eton upgrade described above.


  5. Hi, i have a 2013 1 series 5dr M Sport (120d). How much would it cost to upgrade to what you’ve described above. Cheers!

  6. HI,

    Do you have any suggestions for 118d Msport coupe 2010? Idealy I`d like to switch the Radio too to something App driven.

    1. There are lots of options to make your car sound better and yes I can upgrade your head unit to a screen with the facilities you want. Please call me on 01625 432707 to chat about what we can do.

  7. Hi

    I believe not all Harman Kardon 1 series cars have the MOST ring. A late 2014 car that I have seen has an active sound module and HK amplifier but they are connected via twisted pair analogue. Any info on this appreciated as I want to use the Bit DMi (rebranded Mobridge).


      1. Hi Dave,
        There are so many options. A full system like my blog could be up to £3500 but of course I have many combinations to suit all tastes and budgets. Ideally I like to discuss each install with my customer to make sure I am offering exactly what they want. Please feel free to call me on 01625 432707 to discuss your needs.
        Thank you

      1. Hi Alan, thanks for getting in touch. I have an excellent pack for that car that should fit the bill for £1500 but of course there are many other options. Please give me a call on 07971 928881 or 01625 432707 for a chat about what is best for you.

  8. Hi Tim
    Could you suggest a good sound system upgrade for a BMW 120 I SPORT COUPE Year: 2009
    Much Appreciated

  9. I have a 2014 BMW 1 series Msport – with the worst audio system on the planet, how much would this cost for the above kit.

    Please could you email me.

  10. Hi, I have a BMW Grand Coupe 440i, would like to upgrade the stereo from the base system. Have you done any previous upgrades to this model? Be very interested to know what options are available. Thanks.

  11. About to purchase, after lockdown, a 2009 125i convertible with Professional head unit, but would be looking to upgrade this to something with a screen that could sit on top of the dash, where there’s a storage bin currently. Would also be interested in upgrading the speakers. Is this something you are able to do at all and could you possibly email me with some ideas and costings? Many thanks

    1. Hi Clive, thanks for getting in touch.
      There are a lot of options to discuss, please call me on 01625 432707 so I can design the best system for you.

  12. Hi,

    I recently purchased a 114i Sport 2012 and the sound is rubbish! Haha.

    Could you give me a quote to upgrade the system please?

    Much appreciated.

    1. Hi Alison, thanks for getting in touch.
      We have upgrades for your car from as little as £300 up to any level you wish. Please call me on 01625 432707 so we can chat about options.
      Thank you

  13. How much would you charge to fit this to a 1 series bmw 2012. And how long would it take for you to do it. Thanks

    1. Hi, thanks for getting in touch.
      A typical install is between £1000 and £2500 as it depends on the level of performance you would like and also what systems are already installed to your car. Please feel free to call me on 01625 432707 or 07971 928881 if you would like to discuss what we can do for you.

  14. I have a bmw m140i 2017 with the standard audio fitted. Could you provide me a quote fitted please.

    1. Hi Michael, thanks for getting in touch.
      A typical install is between £1000 and £2500 as it depends on the level of performance you would like. Please feel free to call me on 01625 432707 or 07971 928881 for a chat so I can find out exactly what you would like and I will design a specific system for you

  15. hi
    i have a 116i with harman kardon system ( but no fiber optic cable i think)
    i install a aftermarket android screen (avin usa model) it send sound by the aux
    when i use the original cd player the sound is good ( great for my use) but when i play it directly from the android screen it sound really poor like its not amplified by the harman kardon system… have you a solution for me ?

    1. Hi Jeremy.
      I don’t know that unit you mention so can’t really comment. It would be best if I can see the car and hear the problem. Please feel free to call me to make an appointment on 01625 432707.

    1. Hi Mike, thanks for getting in touch.
      The kit shown would come to just under £2500, installation cost would depend on how you wanted it doing but we would normally want the car for two days and that would be a little over £1000. Of course you might not need the DMI if your system is not MOST connected which would reduce the cost.
      I always like to talk to my customers about exactly what they want so I can design the perfect system for them. Please feel free to call me on 01625 432707 so we can help you get the sound you want.

      1. Hi, I have got BMW 1 series 2013 118d M sport. Please could you email me with the price to upgrade as described above? Or any other sugestions. Thanks

        1. Hi Marek,
          The system shown would be around £3500 but of course there are many options. I have emailed you directly but please feel free to call me on 01625 432707 for a chat.
          My workshop is open by appointment but I could get you in fairly soon.
          Thank you

    1. Hi Shane,
      It all depends on what system you want and what is currently installed to the vehicle. I recently put a complete system into an F31 which is similar in terms of speakers sets. This system cost £2500 fully installed. The results were astonishing with big, punchy bass and incredible detail at the front. The car had the original Harman Kardon system and my system easily outperformed that.
      Of course there are many variations and options available so please give me a call on 01625 432707 to discuss these.
      Thank you

  16. Hi mate, I’ve got a 2014 bmw 1 series 125d fitted with the standard factory speakers (not even Harman Kardon) can you let me know the options and prices for an upgrade cheers

    1. Hi,
      I would definitely change the front speakers for Audison components at a cost of £379. You will also need the tweeter covers from BMW.
      After that we could look at adding an amplifier to really improve the sound. This starts at around £450.
      I often install subwoofers to the car to enhance the bass if your music needs it and this can be done from around £450 also.
      If you would like to discuss options or to get booked in please call me on 01625 432707.

  17. Hi there i have got a bmw 1 series 118d 2013. I have got a shit sound system which is not even harmon n kardon i want to upgrade my sound sustem can u recommend me one and give me the price aswell please.
    I am fron Reading if m happy with the price then will pop down there.

  18. I have a BMW 1 Series 2006 with the pre installed 8 speaker system, ergo, 2 tweeters front doors, 2 mids on the front doors, 2 subs under the seats and 2 speakers in the back on the parcel shelf, it has the BMW Professional HU and I assume an amp.

    Can you send me a full list to replace the amp and all the speakers and the amp please?

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