The goal for this BMW 5 Series was to achieve the best sound possible, show off the equipment installed, whilst ensuring day-to-day use of the vehicle wasn't compromised.

Starting upfront, we installed the Hertz Mille Legend tweeters into a custom made tweeter housing. This was so we were able to have them on display, but more importantly, so we had the ability to aim the tweeters in a desired position/ angle to produce the response we wanted. The BMW midranges were replaced with the matching Hertz Mille Legend midrange speakers. To mount these properly we designed 3D printed speaker adapters which matched the mounting holes and fixtures of the BMW speakers to ensure we had a clean bolt-in bolt-out solution. For the underseat woofers, we stuck with using the Audison Prima BMW 8" woofers found in our BMW sound pack upgrades, these underseat woofers are the best for their application and mounting any other speaker on custom adapters would have given negligible increase in performance and require a lot more work. Sufficient sound treatment was added to the front door skins, along with treating the areas surround the underseat woofers for a natural increase in performance and reduction of road noise. We also used to the Audison BMW wiring harness to extract our audio input signal to the DSP and amplifier, using this wiring harness ensures no cutting of wires and makes for a clean installation.

We installed a Hertz H8 DSP (digital signal processor) which is hidden in the left hand quarter in the boot. If sound quality is the goal, as it was in this 5 Series, then there's no question that a DSP should be a part of the system, as it offers extensive tuning capabilities which is the key to any sound quality system. In our BMW sound pack upgrade options, Levels 2 and 3 both feature an amplifier with a built-in DSP, however, in this case as more demanding speakers are installed, we wanted to push more power into them so a higher powered amplifier was required. We chose to use a Hertz Mille Power 5 channel amplifier which powers the front tweeters, midrage speakers and the underseat woofers (in mono).

As we needed to ensure the boot was left with usable space, we chose to create a small boot installation which has the amplifier on display with varying levels and edge-lit acrylic. We created a completely new boot floor which has a removable panel to expose the amplifier, this panel has neodymium magnets on the underside, so when it is removed it can be stored on the boot's 'ceiling' as it magnets straight to the metal work out of sight, a handy feature so the panel isn't floating around the boot and looks tidy when removed. The new floor was trimmed in a matching carpet and the amplifier installation was trimmed in Alcantara.

This system sounded fantastic, the Hertz Mille Legend components are a truly capable set for providing definition and a natural sound and the Audison BMW underseat woofers powered off of the Hertz Mille Power amplifier arguably excuse the need to add an additional subwoofer in the boot.

We have been fortunate enough to have been allowed access to this vehicle upon request for demonstrations, so if a system of this level is something that you're interested in, please get in touch and we'd be more than happy to discuss options for an upgrade and book a free demonstration is desired.


  • Full digital audio system
  • Hertz Mille Legend tweeters
  • Hertz Mille Legend midrange speakers
  • Audison BMW underseat woofers
  • Hertz Mille Power 5 amplifier
  • Hertz H8 DSP
  • Custom tweeter housings
  • 3D printed speaker adapters
  • Audison BMW integration wiring
  • Custom boot installation
  • Sound treatment
  • Full system tune
  • Free 2 year warranty