What Changed on 2023.5+ Harley Touring Models?
From the 2023.5 production split onward, Harley-Davidson fundamentally changed how audio is routed through its Touring platform.
With the introduction of Skyline OS, the audio signal between the head unit and amplifier moved onto a digital A2B (Automotive Audio Bus) network. Instead of a conventional analogue signal travelling through speaker wires, audio and control data are transmitted digitally across a managed communication bus.
This change is the reason traditional amplifier integration methods used on 2014–early 2023 models no longer work correctly on Skyline-equipped bikes.
Why Traditional Integration Methods No Longer Work
On pre-Skyline bikes, integrators could access usable analogue signals from the factory system and build from there.
On 2023.5+ models, the factory DSP and signal management occur inside the digital network. By the time any analogue signal exists downstream, it has already been processed and dynamically shaped for the OEM speakers.
If you attempt to "tap" into the system without a proper digital interface, you are not working with a clean, flat, full-range source. You are extracting a signal that has already been:
- Equalised for factory speakers
- Dynamically limited to protect OEM components
- Managed by factory-level volume scaling
This typically results in reduced headroom, unstable tonal balance at higher volumes, and a system that cannot be tuned correctly.
In short: the signal foundation is compromised before you even begin.
What Is an A2B Interface?
An A2B interface is a purpose-built module designed to communicate directly with the Harley digital audio network.
It performs three essential roles:
- Communicates correctly with the factory A2B system
- Extracts the original digital audio stream
- Converts that signal into clean, full-range analogue RCA outputs
This gives you a predictable, high-quality signal source for aftermarket amplifiers and DSP systems — without disrupting factory functionality.
On Skyline bikes, this is not an optional accessory. It is the foundation of the upgrade.
Our A2B Interface Options: ZEN-H and ZEN-H PRO
At Motorcycle Audio Australia, we supply two NAV-TV A2B interface solutions for 2023.5+ Harley Touring models:
- ZEN-H — A2B interface with 8-channel RCA outputs
- ZEN-H PRO — A2B interface with integrated 8-channel DSP
ZEN-H: Clean Digital-to-Analogue Integration
The ZEN-H extracts the factory digital signal and converts it into high-quality analogue RCA outputs suitable for aftermarket amplification.
- Digital A2B → Analogue conversion
- 8-channel RCA output
- Designed for correct OEM system integration
Ideal if you are running a standalone DSP or a DSP-equipped amplifier where signal processing happens downstream.
ZEN-H PRO: Integrated Interface + DSP
The ZEN-H PRO includes the same A2B interface functionality with a built-in 8-channel DSP.
This provides:
- Time alignment control
- Crossover configuration
- Phase adjustment
- PC-based tuning interface
This option reduces the need for a separate DSP module and can simplify installation on bikes with limited fairing space.
Which One Should You Choose?
Choose ZEN-H if:
- You already have (or plan to use) a standalone DSP or DSP-equipped amplifier
- You want the A2B interface acting purely as a clean signal hand-off
Choose ZEN-H PRO if:
- You want DSP capability built into the interface
- You prefer fewer modules and less wiring inside the bike
Which Bikes Require an A2B Interface?
This applies to 2023.5+ Harley-Davidson Touring models equipped with Skyline OS.
If your bike is 2014–early 2023 (pre-Skyline), integration follows a different strategy and generally does not require an A2B interface.
What Comes After the Interface?
Once you have a clean analogue signal from a proper A2B interface, system design becomes predictable.
Your next decisions involve:
- Amplifier selection — matching real output power to riding conditions
- Gain structure — maximising clean output without clipping
- Speaker selection — choosing components that suit both the bike and the rider's expectations
- DSP strategy — managing crossover points, staging and tonal balance
The interface itself does not make the system louder. It makes everything that follows accurate and controllable.
Signal First. Everything Else Second.
On Skyline bikes, the A2B interface is the first and most important decision in the upgrade process.
Get the signal path right, and the rest of the system can be engineered correctly.
If you want to explore how amplifier selection, gain structure and DSP tuning connect to this foundation, continue through the Motorcycle Audio Tuning Series, where we break down how to build clean, reliable, high-performance motorcycle audio systems from the signal out.