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Hertz SP4.500 — Advanced 4-Channel Class-D Motorcycle Amplifier (600W RMS / 150W x4 @ 2Ω)
$800.00 AUD
SKU: SP4500
| Channels | 4 Channel |
| Power | 4x90W RMS |
| Year Range | 1998-2013, 2014-2023, 2024+ |
Hertz SP 4.500 — Compact 4-Channel Amplifier for High-Efficiency Harley Audio Builds
The Hertz SP 4.500 is a compact, efficient 4-channel Class-D amplifier tailored for motorcycle audio systems that run high-sensitivity speakers and need clean power without the complexity of oversized amps. With an IP55 weather-resistant rating and a low-profile chassis, it fits easily into Harley Touring fairings while delivering reliable performance at volume.
Key Features
- 90 W × 4 RMS @ 4 Ω (@ 14.4 VDC, 1% THD) — ideal for powering high-efficiency SPL speakers.
- 150 W × 4 RMS @ 2 Ω (@ 14.4 VDC, 1% THD) — additional headroom for demanding systems.
- Bridged Mode: 300 W × 2 RMS @ 4 Ω (@ 14.4 VDC, 1% THD) when running 2-channel configurations.
- 3-Channel Mode: 80 W × 2 @ 4 Ω + 330 W × 1 @ 4 Ω, or 145 W × 2 @ 2 Ω + 300 W × 1 @ 4 Ω (@ 14.4 VDC, 1% THD) — run a front stage and a subwoofer from a single amplifier.
- Up to 87% efficient ADC (Advanced D-Class) output stage with a 27 A maximum musical current draw.
- IP55 weather resistance protects against water, dust, and road grime.
- Ultra-compact chassis (192.7 × 130 × 49 mm) fits tight Harley fairings.
- Pre-level and speaker-level inputs (0.6–6 V and 2.2–22 V) for flexible system integration.
- Selectable crossovers for high-pass, low-pass, or full-range operation, adjustable 50 Hz to 5 kHz @ 12 dB/octave on both channel pairs.
Why It Works on Harleys
- Perfect match for high-efficiency speakers like Hertz SX and SV series.
- Compact size allows clean installation in Street Glide and Road Glide fairings.
- Weather-ready design handles open-air motorcycle environments.
- Efficient power draw suits bikes running stock or mildly upgraded charging systems, once fused power and ground wiring are correctly sized.
Recommended System Use
- Front Stage: Powers 6.5″ coaxials or SPL midranges with ease.
- Full Bike System: Run front + rear speakers on one amplifier.
- Front Stage + Subwoofer: 3-channel mode drives a pair of speakers plus a subwoofer from the one amplifier — the simplest way to add low-end without a second amp.
- Active Setups: Use two channels for mids and two for tweeters when DSP-controlled.
Fitment
- Designed for Harley-Davidson Touring motorcycles
- Suitable for Street Glide, Road Glide, Ultra Limited and CVO models
- Fits factory fairings, amp trays, or aftermarket amp plates
Specifications
| Channels | 4 |
| RMS Power @ 4 Ω | 90 W × 4 @ 14.4 VDC, 1% THD |
| RMS Power @ 2 Ω | 150 W × 4 @ 14.4 VDC, 1% THD |
| RMS Power (Bridged @ 4 Ω) | 300 W × 2 @ 14.4 VDC, 1% THD |
| RMS Power (3-Channel Mode) | 80 W × 2 @ 4 Ω + 330 W × 1 @ 4 Ω, or 145 W × 2 @ 2 Ω + 300 W × 1 @ 4 Ω (@ 14.4 VDC, 1% THD) |
| Total RMS Power | 600 W @ 14.4 VDC, 1% THD |
| CEA-2006 Power | 75 W × 4 @ 4 Ω |
| Minimum Load Impedance | 2 Ω (4-channel), 2 + 2 + 4 Ω (3-channel), 4 Ω (bridged) |
| THD | < 0.02% @ 1 kHz, 4 Ω, 70% rated power |
| Efficiency | Up to 87% |
| Max Musical Current Draw | 27 A |
| Bandwidth (−3 dB) | 10–35,000 Hz |
| Signal-to-Noise Ratio | 100 dBA |
| Damping Factor | > 150 |
| Pre-In Sensitivity | 0.6–6 V |
| Speaker-In Sensitivity | 2.2–22 V |
| Crossovers | HPF / LPF / Full-Range — 50 Hz to 5 kHz @ 12 dB/octave, high-pass and low-pass, on both channel pairs |
| Dimensions | 192.7 × 130 × 49 mm |
| Weight | 2.15 kg |
| IP Rating | IP55 |
Specifications per Hertz published technical documentation.
Need System Design Help?
The SP 4.500 is ideal for efficient SPL setups. We can help you match speakers, crossovers, and DSP settings to create a clean, balanced system for your Harley.
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.
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.