SP-50×4 - 4CHANNEL PLUG AND PLAY (PRICE UNIT)
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SUPER POWER AUDIODESIGNED IN ITALY
MMXXVI
SP-50×4 — a real amplifier on the factory harness
Four channels, 4 × 50 W RMS at 4 Ω per channel, six analogue tone trims and a full pass-through: the head unit plugs into TO HEAD UNIT, the car’s own harness plugs into TO AUTOMOTIVE, and every factory feature keeps working exactly as before. No RCA cabling, no separate power block, no gain calibration. 151 × 103 × 45 mm, 0.6 kg.
What the four channels actually deliver
4 × 50 W RMS at 4 Ω per channel — continuous power, confirmed by SP Audio, not a burst figure. This is what the four channels hold all day into a factory speaker set, which is exactly the load the amplifier is built around: 4 Ω is the minimum per channel. Everything else on this page comes from the SP-50×4 professional user manual, Rev. 1.0, September 2026.
Why plug and play changes the job
Power, turn-on and all four speaker-level signal pairs travel through a single 16-pin harness cable. No RCA runs down the sills, no separate power block at the battery, no gain calibration procedure. A typical install is measured in tens of minutes, not in an afternoon.
The car’s original connector goes into TO HEAD UNIT; the vehicle harness goes into TO AUTOMOTIVE. Display, chimes, steering-wheel controls, reverse-gear and illumination lines pass straight through. The amplifier sits invisibly in the middle.
FRONT and REAR each get HIGH, MID and LOW. Front and rear speakers sit at different distances and behind different trim panels, so they never sound identical out of the box — two independent trim sets let you keep the front stage dominant and correct the rear.
A pair of RCA pre-amp outputs feeds a separate subwoofer amplifier or an active subwoofer, so the system can gain a sub later without touching the factory wiring again.
These are continuously-variable analogue tone trims, not a parametric DSP: no adjustable crossover points, no delay, no EQ curve you can draw. They will balance a factory speaker set noticeably better than leaving everything flat — they will not replace a dedicated processor.
151 × 103 × 45 mm and 0.6 kg: under a seat, behind a dash panel, in the boot side panel — wherever the factory harness connector is easiest to reach. Two mounting points, aluminium fins for cooling.
Every control, panel by panel
7 TO HEAD UNIT (16-pin, from the factory head unit) · 8 TO AUTOMOTIVE (16-pin, on to the car)
3 HI/ACC — slide switch: high-level auto turn-on or ignition (ACC) turn-on
Safety, the full 16-pin pinout with wire colours, mounting, the tuning procedure, the troubleshooting table and the factory specification sheet. Read it before the first cable is cut.
⇩ Download the SP-50×4 manual (PDF)PDF · 1.0 MB · English · Rev. 1.0, September 2026
What is in the box
The SP-50×4 ships ready to slot between a factory head unit and the car’s original speaker harness. Check the carton on unboxing: no dents on the fins, both bumpers intact, both 16-pin ports clear of debris, and both connector shells clicking firmly with no bent pins.
Included: SP-50×4 amplifier ×1 · 16-pin harness cable ×1 · mounting screws Ø4×16 mm ×2 · user manual ×1
Not included: the vehicle-side harness adapter if your factory connector differs, speaker cable extensions and any subwoofer cable — these are installation materials and depend on the car.
Technical specifications
| POWER OUTPUT | |
|---|---|
| RMS power output | 4 × 50 W RMS at 4 Ω per channel |
| Total harmonic distortion | < 0.1% THD |
| Minimum load per channel | 4 Ω |
| AUDIO | |
| Channels | 4 |
| Frequency response | 20 Hz – 20 kHz |
| Signal-to-noise ratio | ≥ 88 dB |
| Input sensitivity | 0.2 – 6 V |
| Input type | High-level (speaker-level), 16-pin harness |
| Pre-amp sub output | RCA FL-OUT / FR-OUT |
| CONNECTIONS & CONTROL | |
| Harness ports | TO HEAD UNIT (in) · TO AUTOMOTIVE (pass-through out) |
| Turn-on selector | HI / ACC slide switch |
| Tone trims | 6 × continuously-variable analogue trims (FRONT and REAR × HIGH / MID / LOW) |
| Electrical system | 12 V negative ground only — not for 24 V vehicles |
| MECHANICAL | |
| Dimensions (L × H × W) | 151 × 103 × 45 mm |
| Net weight | 0.6 kg |
| Mounting points | 2 |
| Chassis | Aluminium, finned, black with orange SP AUDIO mark |
| IN THE BOX | |
| Included cable | 16-pin harness cable |
| Mounting hardware | Mounting screw Ø4×16 mm ×2 |
| Documentation | Professional user manual, 21 pages |
Power is 4 × 50 W RMS at 4 Ω per channel, continuous, as confirmed by SP Audio. Every other figure on this page comes from the SP-50×4 professional user manual, Rev. 1.0, September 2026. One note: the amplifier class is not formally published in the factory documentation, so we do not state one here rather than guess. Specifications may change without notice.
The 16-pin harness, pin by pin
| PIN | SIGNAL | WIRE COLOUR & FUNCTION |
|---|---|---|
| 1 | BATT+ | Yellow — +12 V power |
| 2 | GND | Black — ground |
| 3 | ILL | Orange — illumination detection line |
| 4 | ACC | Red — ignition (accessory) wire |
| 5 | KEY2 | Brown — steering-wheel control line 2 |
| 6 | “BLACK” | Pink — reverse-gear detection line. Printed by the factory as “BLACK”: it is not a ground. Confirm it on a multimeter before wiring. |
| 7 | ANT | Blue — automatic antenna power supply |
| 8 | KEY1 | Orange/Black — steering-wheel control line 1 |
| 9 | RL− | Green/Black — rear-left speaker − |
| 10 | RL+ | Green — rear-left speaker + |
| 11 | FR− | Grey/Black — front-right speaker − |
| 12 | FR+ | Grey — front-right speaker + |
| 13 | RR+ | Purple — rear-right speaker + |
| 14 | RR− | Purple/Black — rear-right speaker − |
| 15 | FL− | White/Black — front-left speaker − |
| 16 | FL+ | White — front-left speaker + |
Colours are as printed by the manufacturer for the supplied harness cable. The vehicle-side factory harness may use completely different colours for the same function: match by pin position and function, verified with a multimeter, never by colour alone. The four speaker pairs carry the head unit’s amplified speaker output, not a low-level RCA signal — this is what lets the SP-50×4 work with no RCA cabling at all.
Build the rest of the system
Read this before you install
- Disconnect the battery first. Remove the negative terminal before touching any factory harness plug, and reconnect it last.
- 4 Ω minimum per channel. Lower impedances can trigger protection and, repeated, damage the output stage.
- 12 V negative-ground vehicles only. Never on a 24 V truck, never on mains power.
- The fins are the cooling system. Free air all round: never under thick carpet, never inside a sealed cavity or a subwoofer box, never near the exhaust or heater ducts.
- Never bypass or upgrade the on-board fuses. Use identical replacement ratings.
- Connect the right way round. Factory head unit → TO HEAD UNIT; vehicle harness → TO AUTOMOTIVE. Reversing them does not damage the amplifier, but the pass-through features will not work.
- Secure both mounting points. A loose amplifier is a projectile in a collision.
- Do not open the chassis. There are no user-serviceable parts inside and opening it voids the warranty.
- Professional installation. Damage caused by improper installation is not covered by warranty.
Questions we actually get asked
spaudio@spaudio.it · +39 340 807 8778
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SP AUDIO · Audiocar Import & Export SRLS — Official SP AUDIO Distributor for Europe · Piazza IV Novembre 4, 20124 Milano (MI), Italy · VAT IT13085510967. All technical data on this page is the manufacturer’s declared data from the SP-50×4 professional user manual Rev. 1.0 (September 2026) and may change without notice.