Hertz HMP 4D — Compact 4-Channel Amplifier for Everyday Harley Audio Upgrades
The Hertz HMP 4D is a compact, weather-resistant 4-channel amplifier designed for riders who want a clean, reliable power upgrade without stepping into high-output SPL territory. With an IP64-rated chassis, flexible crossovers, and efficient Class-D power, it pairs perfectly with high-sensitivity speakers and budget-conscious Harley Touring builds.
Key Features
- 50 W x 4 RMS @ 4 Ω — ideal for efficient coaxials and midranges.
- 65 W x 4 RMS @ 2 Ω for added headroom when needed.
- Bridged Output: 130 W x 2 for 2-channel systems.
- IP64 weatherproof chassis protects against rain, washdowns, and dust.
- Ultra-compact size (184 × 102 × 43.6 mm) ideal for tight Harley fairings.
- Selectable crossovers for HPF, LPF, or full-range operation.
- High and low level inputs for compatibility with OEM and aftermarket radios.
Why It Works on Harleys
- Perfect match for high-efficiency speakers (95–100 dB sensitivity).
- Compact chassis fits easily into Street Glide and Road Glide fairings.
- Weather-resistant build ideal for open-air motorcycle use.
- Efficient power draw works well with stock charging systems.
Recommended System Use
- Front + Rear Speakers: Drive all four speakers with moderate power.
- Entry-Level Front Stage: Clean upgrade over factory amp or radio power.
- Bridge Mode: Power a pair of coaxials or midranges with 130 W x 2 for added authority.
Fitment
- Designed for Harley-Davidson Touring motorcycles
- Fits most amp trays, fairings, and under-OEM radio cavities
- Works with factory head units and aftermarket radios
Specifications
| Channels | 4 |
| RMS Power @ 4 Ω | 50 W × 4 |
| RMS Power @ 2 Ω | 65 W × 4 |
| RMS Power (Bridged @ 4 Ω) | 130 W × 2 |
| Frequency Response | 10–45,000 Hz |
| Crossovers | HPF / LPF / Full-Range |
| Input Sensitivity | 0.2–5 V |
| S/N Ratio | > 85 dB |
| Dimensions | 184 × 102 × 43.6 mm |
| IP Rating | IP64 |
Need Help Choosing?
If you're building a clean, budget-friendly Harley system with high-efficiency speakers, the HMP 4D is a perfect fit. We can help you match it with the right speaker and wiring configuration.
Shipping
Australia Shipping:
- Under $500 → $19.95
- $500–$2,500 → $14.95
- Over $2,500 → FREE
- Bulky items → +$24.95 surcharge (waived over $2,500)
Fast dispatch from Brisbane. Same-day shipping on in-stock orders before 1pm AEST.
Return policy
Change-of-mind returns: We accept returns within 7 days of delivery on unused, unopened products in original sealed packaging. Restocking fees apply (20–30%). Return shipping is the customer’s responsibility.
No returns on opened audio gear, installed items, custom orders, or special-order products. Please check fitment carefully before installing.
Faulty or incorrect items: If you experience an issue, contact us with photos/video and your order number. We’ll assess the claim and arrange repair, replacement, or refund for verified faults under the Australian Consumer Law.
Fitment assistance: If you’re unsure about compatibility, reach out before ordering—we’re happy to help.