Zapco M-AT1 — Measurement Microphone for DSP-IV AT Auto-Tuning

Zapco M-AT1 — Measurement Microphone for DSP-IV AT Auto-Tuning

The M-AT1 is the omnidirectional measurement microphone Zapco supplies for the Auto-Tuning function on the DSP-IV AT processors. It covers 20 Hz to 20 kHz, connects to the processor's dedicated microphone input, and comes on a 3-metre cable.

It is not a general-purpose recording microphone. It exists to let the processor measure the vehicle.

What Auto-Tuning Actually Measures

With the M-AT1 placed at the listening position, the processor plays test signals through the system and measures what arrives. From that it sets equalization, time delay, and phase automatically.

Those three things are the measurable part of a car tune. Path lengths from each driver to the listener differ by feet, not inches, and the cabin's own reflections and resonances shape the response before it reaches an ear. A microphone at the seat captures both effects directly — there is no way to calculate them from a driver's specifications.

Omnidirectional, and Why That Matters

The M-AT1 is omnidirectional, meaning it responds equally to sound arriving from any direction. For measurement in a car that is the correct pattern: the objective is to capture the total sound field at the seat, including reflections off glass, dash, and pillars, because that is what the listener hears.

A directional microphone would reject much of the reflected energy and produce a measurement of something the listener is not actually experiencing.

System Application

Required for Auto-Tuning on the Zapco DSP-Z8 IV AT and ADSP-Z8 IV-6AT. Those are the two processors in the range that carry the Auto-Tune function, and both provide a dedicated microphone input for it.

The processors tune manually without it. The microphone is what makes the automatic calibration available.

Installation Considerations

Position matters more than anything else about using it. Place the microphone where the listener's head actually sits, at seated height, with the vehicle in the state it will be driven in — doors closed, windows up, HVAC off.

The 3-metre cable is generally enough to reach from a processor mounted under a seat or in a rear compartment to the front listening position. Measure the run before assuming it.

The microphone operates on 4.5 V DC supplied by the processor and draws 0.5 mA. It is rated from −40°C to +70°C, so it tolerates being left in a vehicle, though there is no reason to.

Specifications

• Type: measurement microphone for DSP-IV AT auto-calibration
• Directivity: omnidirectional
• Frequency response: 20Hz – 20kHz
• Sensitivity (1kHz, 0dB = 1V/1Pa): −44 dB
• S/N (A-weighted, 1kHz): 60 dBA
• Output impedance: 1 kΩ
• Operating voltage: 4.5V DC (10V max)
• Current consumption: 0.5 mA
• Operating temperature: −40°C to +70°C
• Cable length: 3 m
• Dimensions: 190 × 21 × 12.5 mm

HF Audio Perspective

Auto-Tuning handles the geometry. It does not handle taste.

What the M-AT1 and the processor do together is solve the measurable problems — arrival times that differ from left to right, cabin modes that put a peak where there should not be one, phase relationships at the crossover points. That work is tedious by hand and the measurement is more accurate than an ear is.

What comes out is a correct starting point, not a finished tune. The target curve, the balance between stage width and centre focus, how much energy the top end should carry — those are decisions, and a microphone does not make them. Builders who treat the auto-tune as the beginning of the process get good results from it. Builders who treat it as the end usually wonder why the system measures well and does not sound the way they wanted.