Reference Series · Head Units
Upgraded Your Harley Head Unit? Choose the Right Amp and Speakers Next
Quick answer: A new head unit upgrades the source (CarPlay, a better screen, and dedicated RCA pre-outs), but the amplifier and speakers determine how the system performs at speed. What happens next depends on your bike: is the radio driving the speakers through its own internal amplifier, or feeding a factory amplifier? Adding a dedicated aftermarket amplifier fed from the RCA outputs is what removes the power ceiling, and there is more than one valid order to do it in. On 2024+ Skyline bikes there is no aftermarket head unit, and adding amplification uses an A2B interface.
A new aftermarket head unit is a genuine upgrade for most 2014-2023 Harley-Davidson Touring bikes: wireless Apple CarPlay, a brighter touchscreen, cleaner Bluetooth, and dedicated RCA pre-outs. But many riders find the bike does not sound dramatically better a few weeks in. That is not a defect in the head unit; it is a system question, and once you understand it the next step is clear.
What a New Head Unit Actually Changes (and What It Doesn't)
An aftermarket head unit such as the SoundStream Reserve range gives you two ways out: speaker-level outputs (direct to speakers, limited power) and dedicated RCA pre-outs designed to feed an external amplifier. The RCA pre-out is the important one, but for the right reason:
- Its advantage is not that it is "higher voltage than the factory radio." A factory speaker-level output is amplified and can actually carry more voltage. The benefit of an RCA pre-out is that it is a dedicated, low-level, predictable source for an amplifier's input, with a clean gain structure, rather than a signal derived from an amplified speaker output.
- An RCA pre-out is not automatically "flat and unprocessed" either. An aftermarket radio can still apply its own EQ, loudness, crossovers or source processing. The RCA path avoids factory speaker-level conversion and gives a more predictable amplifier input, provided the head unit's EQ and processing are configured correctly.
The catch is that if you have not added an aftermarket amplifier, the pre-out is not doing anything yet. What limits the system depends on how your bike is wired.
First, Which Setup Do You Have?
Do not assume every 2014-2023 bike has a separate factory amplifier. Many standard Touring configurations run the radio's internal amplifier straight to the speakers, unless the bike left the factory with an amplified audio package. The next step differs between the two:
- Radio driving the speakers directly (internal amp). This is a valid, basic system: it works, but the head unit's internal amplification limits the available clean power, so it runs out of headroom at highway speed. Adding an external amplifier from the RCA outputs is what lifts that ceiling.
- Radio feeding a factory amplifier (amplified package). Here the factory amplifier is the constraint: it is modest by aftermarket standards and applies its own EQ and limiting tuned for stock speakers, which works against an upgraded system. Replacing it with an aftermarket amplifier fed from the RCA outputs is the fix.
If you are not sure which you have, that is exactly the kind of thing to confirm before buying, since it changes the wiring and the parts. See Stock Harley Radio vs Aftermarket Head Units.
What Adding an Aftermarket Amplifier Does
A Cicada Audio amplifier connected to the head unit's RCA outputs does what the factory amplification cannot:
- Delivers real power. Enough headroom to drive upgraded speakers cleanly at highway speed without clipping or compression.
- Works from a dedicated low-level source. Connected to the RCA outputs, the amp receives a predictable line-level input rather than a signal derived from an amplified speaker output.
- Gives you control. Gain structure, crossover points and channel assignment can be set correctly. Note the distinction: gain and basic crossover controls exist on conventional amplifiers, but parametric EQ, time alignment and advanced per-channel processing belong to a DSP-equipped amplifier (the Cicada FLX700.4PRO or FLX1400.4PRO) or a separate DSP.
For how Cicada amplifiers are specified and what the ratings mean in a Harley install, see the Cicada Motorcycle Amplifiers Guide, and for matching amp output to speakers, How to Match Speakers and Amplifiers.
Where Speakers Fit
Factory Harley speakers are built to a specific impedance, sensitivity and response, optimised for factory power and EQ. Once an aftermarket amplifier is driving the system, Cicada speakers are designed for that environment: high-sensitivity drivers for the fairing and saddlebag positions with the power handling to be driven properly. In practice that means fairing speakers that project clearly at speed, 6x9-inch saddlebag speakers for rear fill, and horn-loaded CHX options for genuine highway projection. See the Cicada Motorcycle Speakers Guide.
There Is More Than One Valid Order
The head unit, amplifier and speakers all matter, but the sequence is not fixed. Depending on what you already have and your goal, valid paths include:
- Head unit only (a source and connectivity upgrade)
- Head unit plus correctly matched speakers
- Head unit plus an amplifier
- Head unit, amplifier and speakers together
- Head unit plus a DSP amplifier
- Existing speakers retained temporarily while amplification is added, then upgraded later
If you have the head unit done and want the amplifier and speakers matched in one go, Cicada complete kits pair an amplifier and speakers pre-matched for impedance and power handling, with harness and mounting hardware. Confirm the kit contents for your exact bike and audio package before ordering.
A SoundStream Advantage: Direct Harness Integration
One practical differentiator for SoundStream builds: for SoundStream head units paired with Precision Power, Cicada or Hertz amplifiers, MAA can modify or build the relevant harness so the radio connects directly to the amplifier without cutting the bike's factory wiring. That keeps the install clean and reversible and gets the RCA signal to the amplifier the right way for your exact combination.
A Note on 2024+ Skyline OS Models
The above applies to 2014-2023 bikes running a Boom! Box or an aftermarket head unit. The 2024+ Skyline OS platform is different: there is no aftermarket head unit replacement, because the system uses a digital A2B audio bus. A confirmed speaker-only swap that keeps the factory amplification does not need an interface. To add or replace amplification, the signal is taken from the A2B bus using a compatible A2B interface (such as the NAV-TV ZEN-H or the Volunteer Audio / SeirenHD HD-A2B, each with the correct Cicada harness), which replaces the factory amplifier and supplies predictable analogue outputs while retaining supported factory controls. Confirm compatibility for the exact model and audio package. See Why 2023.5+ Harley Audio Upgrades Need an A2B Interface.
Quick Decision Guide
To plan the next step, work through: what speakers are on the bike now; whether there is a factory amplifier or the radio drives the speakers directly; whether the head unit has usable RCA outputs; how fast you ride; how many speaker positions you want to run; and whether you need DSP. Those answers point to the right amplifier, speaker and (on Skyline) interface choice.
Frequently Asked Questions
Why doesn't my Harley sound much better after the head unit upgrade?
A new head unit improves the source and adds connectivity, but if the system is still limited by the radio's internal amplifier or a factory amplifier, that remains the constraint. The RCA pre-outs need an external amplifier to make a meaningful difference at speed.
Can I use the new head unit without adding an external amplifier?
Yes. Driving the speakers directly from the head unit is a valid basic system, it just provides less clean headroom than a dedicated external amplifier. The RCA pre-outs are what enable a proper external amplifier when you are ready.
What order should I do the upgrades in after the head unit?
There is no single correct order. An amplifier usually unlocks the most performance from a new source, but a matched speaker upgrade, a DSP amplifier, or doing amplifier and speakers together are all valid depending on your bike and goal.
Do Cicada complete kits work with an aftermarket head unit?
Yes. Cicada complete kits connect to the RCA outputs of an aftermarket head unit; the harness is designed for the amplifier connection. Confirm the kit contents and fitment for your bike before ordering.
Got a new head unit and want to complete the upgrade?
Tell us what you've installed and whether the bike has a factory amplifier, and we'll help you plan the amplifier and speaker stage.
Get in Touch →Summary
A new head unit is a strong first move on a 2014-2023 Harley: it improves the source, adds connectivity and creates the RCA pre-out that makes a proper amplifier install possible. But it does not replace the amplification. Whether the constraint is the radio's internal amp or a factory amplifier, a dedicated aftermarket amplifier fed from the RCA outputs, driving speakers built for that power, is what takes Harley audio from "better than stock" to genuinely good at highway speed. On 2024+ Skyline bikes, that same amplification step is done through an A2B interface.
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