Zapco Z-150.4 II Review: Class AB Sound Quality With Crossovers Built In
Updated: Oct 6
The Zapco Z-150.4 II is a four-channel Class AB sound-quality amplifier that keeps the controls Zapco's purist AP models leave out. It is rated at 4 x 165 W into 4 Ω, 4 x 275 W into 2 Ω or 2 x 550 W bridged into 4 Ω, and it carries variable high-pass and low-pass crossovers plus a 0–12 dB bass boost. At ₹1,19,990 MRP in the 2026 Indian catalogue, it sits below the six-channel Z-150.6 II and ₹80,000 below the four-channel Z-150.4 AP. It suits buyers who want Class AB amplification for a component front stage plus rear speakers or a subwoofer, with or without a DSP. Current pricing is on our Z-150.4 II product page.
Key points
Four Class AB channels: 165 W each at 4 Ω, 275 W at 2 Ω, or two bridged channels at 550 W into 4 Ω.
Front high-pass and rear high- and low-pass filters with range multipliers, variable bass boost and a 2/4-channel input switch.
A 0.5–8 V input range accepts low-voltage head-unit pre-outs as well as processor outputs.
We found no owner or magazine review of this model to report as of October 2026.
Zapco Z-150.4 II specifications
Specification | Zapco Z-150.4 II |
|---|---|
Type | 4-channel Class AB sound-quality amplifier |
Power, 4 Ω stereo | 4 x 165 W |
Power, 2 Ω stereo | 4 x 275 W |
Power, 4 Ω bridged | 2 x 550 W |
Minimum load | 2 Ω stereo, 4 Ω bridged |
THD at rated power | Less than 0.05% (product page); less than 0.1% (manual) |
Signal-to-noise ratio | More than 100 dB |
Frequency response | 10 Hz – 30 kHz (±1 dB) |
Input sensitivity | 0.5 – 8 V |
Inputs and outputs | 4 x RCA in, 2 x RCA pass-through out |
Crossover | Variable full-range, low-pass or high-pass |
Bass boost | 0 – 12 dB, variable |
Dimensions | 444 x 190 x 62 mm (479 mm overall length) |
India MRP | ₹1,19,990 |
Specifications are from Zapco's Z-150.4 II page and the 2026 Indian catalogue. Zapco's own documents disagree on two points: the product page quotes THD below 0.05% and a 10 Hz – 30 kHz (±1 dB) response, while the Z-II owner's manual gives below 0.1% and 15 Hz – 30 kHz, as does the catalogue for response. We show both THD figures rather than pick one.
Z-II versus Z-AP: what actually differs
Zapco launched its Z-Series sound-quality amplifiers in 2012, and its series page describes the Z-II as an evolution of that line, with audiophile-grade capacitors from its LX and SP amplifiers, TI low-noise op-amps, detented metal pots and switches, a bigger power-supply reserve and extra MOSFETs. The catalogue adds that many non-critical parts from the AP and SP amps carried over. Those are manufacturer claims; here is what the published specifications show beside the Z-150.4 AP.
Controls: the Z-II has crossovers, bass boost, an input mode switch and a remote port; the AP has gain only.
Power: 165 W against 150 W per channel at 4 Ω; both make 275 W at 2 Ω and 550 W per bridged pair. Only the AP lists 1 Ω and 2 Ω bridged ratings, for music signal only.
Noise and distortion: the AP quotes a signal-to-noise ratio above 110 dB, the Z-II above 100 dB; the Z-II's product page quotes lower THD (below 0.05% against 0.1%), though its manual says below 0.1%.
Input range: 0.5–8 V on the Z-II against 1–9 V on the AP, so the Z-II reaches full output from a weaker source.
Construction: Zapco lists a differential balanced input stage, LME49720 op-amps, WIMA capacitors and patented RCA sockets for the AP, and TI op-amps, panel-mount RCAs, a PWM MOSFET supply and 4-way protection for the Z-II; the lists are not like-for-like.
Price and size: ₹1,19,990 against ₹1,99,990, in a near-identical 190 mm-wide chassis (479 mm overall against 468 mm).
Running it with or without a DSP
Without a processor, the Z-150.4 II can run a complete system by itself. According to the owner's manual, the front pair has its own gain and a high-pass filter with a range multiplier, the rear pair has gain plus high-pass and low-pass filters, and switches select each pair's crossover mode. A typical layout puts a component set on the front channels, high-passed to keep deep bass out of the doors, and rear speakers or a bridged subwoofer on the rear pair. The 2Ch/4Ch switch lets a head unit with one pair of pre-outs drive all four channels.
Treat the bass boost carefully. Every 3 dB of boost doubles the power needed at that frequency, so the full 12 dB asks for sixteen times as much, which is how subwoofers and amplifiers get hurt. An optional dash-mount remote adjusts bass level from the driver's seat.
With a DSP in the system, the approach flips. Set the crossover switches to full range and the bass boost to zero, then let the processor handle filtering, time alignment and EQ, so two sets of filters don't stack. A processor such as Zapco's DSP-Z8 IV AT or the more ambitious HDSP-Z16 V AD-8A pairs naturally, and our article on the need for DSP in car audio systems explains what you gain.
What owners and reviewers say about the Zapco Z-150.4 II
Independent reviews of this exact model are scarce: when we checked in October 2026, we found no owner, forum or magazine review of the Z-150.4 II that we could verify.
What is verifiable is Zapco's own description of the series, summarised above, and that should be read as manufacturer claims rather than independent findings. If you own a Z-150.4 II, we would be glad to hear how it has worked in your car.
How it compares with the Z-150.6 II and REF 150.4
If you need more channels, the Zapco Z-150.6 II (₹1,49,990) adds a third pair at the same 165 W and 275 W ratings, with subsonic and low-pass controls on channels five and six and an input mode selector for two-, four- or six-channel sources. For ₹30,000 more it can run front, rear and a bridged subwoofer from one chassis, though it grows to 614 mm overall.
The Zapco REF 150.4 (₹1,89,990) goes the other way: no controls, 4 x 150 W at 4 Ω and 4 x 230 W at 2 Ω, but lower rated distortion (under 0.02%), a 10 Hz – 40 kHz response, socketed op-amps and an independent bench test that found it beat its power ratings. It belongs in a DSP system, whereas the Z-II is the more flexible amplifier if you might run without one. The purist Zapco Z-150.4 AP buys a quieter rated noise floor and 1 Ω capability.
Who it suits, and who should look elsewhere
It suits a buyer moving from head-unit power to a proper component front stage who wants Class AB amplification and the option of a DSP later. Its onboard filters also let a system sound right on day one, before the processor budget arrives.
Look elsewhere if the car will have a full active system from the start, where the control-free REF 150.4 (lower rated distortion) or Z-150.4 AP (higher rated signal-to-noise) may make more sense, or if heat and space are tight, since a Class D four-channel runs cooler and smaller.
Installation notes for Indian cars
Many new Indian cars come with a factory touchscreen, and the Z-II's published specifications list RCA inputs only, with no speaker-level input. Connecting it to a factory unit therefore needs a line output converter or a processor with high-level inputs; the DSP-Z8 IV AT accepts speaker-level signals and adds tuning on top.
The chassis is 444 x 190 x 62 mm, or 479 mm overall, so plan a board in the boot or behind the rear seat with clear air over the fins. Class AB output stages draw current even at idle and run warm, and an Indian summer means every drive starts hot. Keep the amplifier out of sealed compartments, and check terminal tightness after a few weeks on broken roads.
Zapco rates power at 14.4 V, so expect a little less with the engine idling and the AC on. The fuse rating isn't in the specifications we have, so use the owner's manual to size the power cable and main fuse. VA3 Car Studio in Ghaziabad installs and sets up Zapco amplifiers, including crossover and gain adjustment.
Price and where to buy
The Z-150.4 II has an MRP of ₹1,19,990 in the 2026 Indian catalogue. VA3 Car Studio often sells it for less; check the current price on our Zapco Z-150.4 II store page. We supply genuine Zapco amplifiers through the brand's Indian distributor, Supreme Audiotek Pvt. Ltd., New Delhi.
The bottom line
The Z-150.4 II is the practical member of Zapco's Class AB family: four channels rated at 165 W each, a full set of filters, bass boost and a remote option, for ₹80,000 less than the AP. It gives up some rated signal-to-noise and the AP's low-impedance ratings, and there is no independent review to lean on yet. If you want Class AB amplification in a system that works with or without a processor, it is the sensible Zapco four-channel to start with.
Zapco Z-150.4 II FAQ
Can the Zapco Z-150.4 II work without a DSP?
Yes. Its front channels have a high-pass filter and its rear channels have high-pass and low-pass filters, so it can run a component set and rear speakers or a bridged subwoofer on its own. A DSP adds time alignment and EQ, but it isn't required.
What is the difference between the Z-150.4 II and the Z-150.4 AP?
The Z-II adds crossovers, bass boost and an optional remote, makes 165 W rather than 150 W per channel at 4 Ω, and costs ₹80,000 less. The AP has gain only, quotes a higher signal-to-noise ratio (above 110 dB against above 100 dB) and adds 1 Ω ratings for music signal.
Can the Z-150.4 II drive a subwoofer?
Yes. Bridge the rear pair into a 4 Ω subwoofer, where Zapco rates it at 550 W, and use the rear low-pass filter. Zapco lists it as stable into 4 Ω bridged or 2 Ω stereo, so don't bridge it into a 2 Ω load.
Buy the Zapco Z-150.4 II in India
Check the Zapco Z-150.4 II price in India, browse more Zapco amplifiers or compare all car amplifiers in India. Want it fitted properly? Book amplifier installation at our Ghaziabad studio.
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