Custom Build · MAA Demo Bike
113.1 dB at the rider's head, from a system built to keep a factory-style look while stepping well beyond factory sound. This is the Motorcycle Audio Australia demo bike: our own 2021 Road Glide Special, built the OEM+ way.
OEM+ means a substantial performance upgrade that keeps a factory-style appearance, preserves the original Harley loom, and uses vehicle-specific or reversible integration wherever practical. On this build it also meant retaining the factory charging system and running with no auxiliary battery. If you want maximum SPL at any cost, this is not that build. If you want a Touring bike that stays close to factory in look and wiring and sounds excellent at highway speed, that is what OEM+ is for.
The Bike
The demo bike is a 2021 Road Glide Special running an S&S 132ci big bore and Rinehart True Duals, tied together with a custom OEM-style audio harness installed alongside the original Harley loom: factory-style routing, CANbus-safe integration and clean connectors, with no cuts or splices to the factory wiring. It is also fully kitted with lighting and comfort upgrades, but this article is about the audio. From the outside it looks close to stock; underneath it is properly engineered, and it gets ridden on real Queensland highways in real heat and humidity.
The Head Unit: SoundStream Reserve V2
The system starts with the SoundStream Reserve V2 (HDHU.V2), an 8.3-inch plug-and-play head unit built for 2014 to 2023 Harley Touring. Wireless Apple CarPlay and Android Auto, built-in GPS, Rally Mode group-ride broadcasting, and an IPX5-rated faceplate designed to resist the rain and water exposure of everyday riding. This unit has run reliably through the demo bike's Queensland use. Each one leaves our workshop with the latest firmware installed and Maestro preparation completed.
Amplification: Precision Power MAA4.400
Power for the main speakers comes from a single Precision Power MAA4.400, a compact 4-channel Class-D amplifier rated at up to 100W × 4 RMS at 4Ω, or 150W × 4 at 2Ω (600W total), under its specified test conditions. On this build it runs the 4Ω front and rear speakers, so up to 100W RMS per channel, around 400W across the four-channel stage. It has more channel capability than the 75W RMS front speakers require, so gain and high-pass filtering were set to suit the installed speakers rather than simply running the amp wide open. It is compact enough to install discreetly in a protected location, with a vibration-resistant, thermally stable design intended for motorcycle use. For this four-speaker configuration, one properly installed and tuned four-channel amplifier was sufficient.
Front Stage: Precision Power HD14.654
Up front, the factory speakers are replaced with Precision Power HD14.654 6.5-inch 4Ω fairing speakers with matching metal grilles: a direct-fit swap that removes the plastic factory grilles for a cleaner, more premium look, with strong mids that cut through engine and wind noise. SoundSkins Pro deadening in the speaker pods keeps the front stage tight and focused.
Rear Stage: Precision Power MAS.694
The rear stage runs Precision Power MAS.694 6×9 speakers, fitted into the factory saddlebag lids with the Precision Power HD14.SBS cut-in kit, which supplies the cutting template, mounting adapters, OEM-style grilles and waterproof quick-disconnect wiring needed to add 6×9 speakers to the original lids. The result is warm mid-bass and strong rear fill for rider and passenger. In a separate staged dB test on a 2021 Street Glide, adding MAS.694 rear speakers and the MAA4.400 to a good front setup produced the largest measured increase in that sequence, from 99 to 100 dB up to 112 dB at the rider's position.
The Dual Subs: Two Precision Power HD14.SBW
Low end comes from two Precision Power HD14.SBW powered saddlebag subwoofers, one in each bag (clutch-side SBWL and brake-side SBWR). Each is a self-contained unit: a down-firing subwoofer driver with a passive radiator and its own 300W built-in Class-D amplifier, in a rotomolded ABS enclosure that drops into the stretched OEM saddlebag without cutting the bag to fit the enclosure or any fibreglass fabrication. The bass pressure escapes through the included HD14.SBV acoustic vent kit, which does require drilling the bag floor: 15 hydrophobic-mesh vents per bag that let the low end out while keeping water and road debris out. At highway speed you feel the low end as much as you hear it. Each unit takes up most of a saddlebag, one per side, which is the honest trade-off for that full-time foundation.
Sound Deadening: SoundSkins Pro
SoundSkins Pro through the fairing and saddlebags reduces panel vibration and unwanted resonance, helping the system produce a cleaner, more controlled response. It is the invisible part of the build that makes the audible part sound better.
System at a Glance
| Component | Power / role |
|---|---|
| SoundStream Reserve V2 head unit | Source: wireless CarPlay and Android Auto, GPS, IPX5 faceplate |
| Precision Power MAA4.400 | 4-channel amp: rated 100W × 4 RMS at 4Ω, 150W × 4 at 2Ω (600W total) |
| HD14.654 front / MAS.694 rear | Main speaker stage: 6.5-inch fairing (75W RMS) and 6×9 saddlebag-lid (100W RMS) |
| 2× Precision Power HD14.SBW | Dual powered saddlebag subs: 300W built-in Class-D each |
| Total | About 400W across the main stage plus 600W of powered sub amplification |
All of it running from the stock Harley charging system, with no auxiliary battery.
How Loud Is It? 113.1 dB, Measured
We don't guess at loudness, we measure it. At the rider's head, with a calibrated miniDSP UMIK-1 microphone on the bike's centreline, set at the head height of a 182 cm rider and pointing forward (with the UMIK-1's own calibration file loaded, on-axis), engine off in our controlled workshop, this system read 113.1 dB, with 114.1 dB recorded by the app's maximum-hold, unweighted, Slow response on the SPL Pro meter. It is an indoor reference measurement: room reflections can influence the reading, so it is most useful compared with other tests done in the same room, at the same microphone position and with the same settings. The 113.1 dB figure is a short-duration, maximum-output reference test, not a recommended continuous listening level. On the road the system is normally run below that test level, and hearing protection is strongly recommended for sustained high-volume riding. See the full method, and how each upgrade stage adds measurable output, in our dB Reference write-up: How Loud Is Your Harley Audio Upgrade?
On the Road
This system has been tested across Queensland highways, in summer heat, through tropical storms, and on long days in the saddle. It stays balanced and usable at normal highway listening levels, with enough available output to cut through a lot of wind, engine and exhaust masking. The 113.1 dB reading under MAA's indoor reference method shows the system's short-duration capability, a high-output result for a factory-style touring build, rather than a level meant for continuous listening. The goal is not maximum SPL for its own sake, but a system that sounds genuinely good at the volumes you actually ride at, every ride.
Frequently Asked Questions
What does OEM+ mean?
An upgrade that keeps a factory-style appearance and preserves the original Harley loom, using vehicle-specific or reversible integration wherever practical, while delivering far more output and clarity than stock. On this build it also meant retaining the factory charging system and running with no auxiliary battery.
Does it really run on the stock charging system?
Yes. The whole system, the main amplifier and both powered subs, runs from the factory Harley charging system with no auxiliary battery, and it operated reliably that way during normal music use. That does not mean the charging system could sustain the main amplifier and both powered subs at full rated output continuously; the components were chosen and the gains set with that in mind.
How loud is 113.1 dB in practice?
A 10 dB increase is commonly perceived as roughly twice as loud under comparable conditions, so a system in the 113 dB range feels dramatically louder than a stock or head-unit-only setup. The figure should be compared with other MAA tests using the same room, microphone position and settings, not with readings taken outdoors or by another workshop, and it is a short-duration capability test, not a recommended continuous listening level. See our dB Reference testing for the full method.
Do the dual subs leave any luggage space?
Each HD14.SBW takes up most of one saddlebag, so with a sub in each bag, dedicated luggage space is limited. It is a deliberate trade-off for full-time low end; if you need more storage, a single sub or a slimmer bass option is worth discussing.
Want a System Like This?
Tell us your bike, how and where you ride, and your goals, and we'll map out an OEM+ build to suit, then measure the result the same way we measured this one.
Get in Touch →Shop this system
- SoundStream Reserve V2 (HDHU.V2) head unit
- Precision Power MAA4.400 4-channel amplifier
- Precision Power HD14.654 front fairing speakers
- Precision Power MAS.694 6×9 rear speakers with the HD14.SBS lid cut-in kit
- Precision Power HD14.SBW powered saddlebag subs (one per bag)
- SoundSkins Pro fairing and saddlebag deadening
Not sure what fits your bike? Contact Motorcycle Audio Australia with your year, model and goals and we'll confirm the right parts →
What's Next: The Cicada Rebuild
This SoundStream build is a complete, recommendable OEM+ system in its own right. The demo bike has since moved on to our next project, a full Cicada Audio rebuild with twin amplifiers, a DSP and 10-inch saddlebag mid-bass, built to push the numbers higher again. Follow it in Cicada Rebuild Stage 1 and Stage 2.
More reading: our 2015 to 2023 Road Glide audio upgrade guide, and the rest of our measured builds in System Tests.
Motorcycle Audio Australia. Sound That Rides.