Hertz ST25KNEO-2 1.8" Compression Tweeter Kit

The Hertz ST25KNEO-2 is a compact 44 mm (1.8-inch) high-efficiency compression tweeter kit designed to add focused high-frequency output to a car audio system. It is intended for systems that need dedicated treble reproduction above the midrange range. With a 4-ohm nominal impedance and 107 dB sensitivity rating, it is suited to high-output speaker installations.

This kit is a practical option for enthusiasts building or upgrading an SPL-oriented system with separate midrange drivers. Its aluminium dome and horn-loaded design are engineered to reproduce upper-frequency detail from 3 kHz to 20 kHz. The compact neodymium motor helps keep the assembly lighter and more space-conscious than conventional large-magnet compression tweeters.

The ST25KNEO-2 uses a 25 mm CCAR copper-clad aluminium ribbon voice coil and an extra-light aluminium membrane. Hertz also specifies a FEM-optimized phase plug and loading horn, intended to support controlled high-frequency output. Its 100-watt peak power-handling specification applies with a 5 kHz high-pass filter at 12 dB per octave.

As the kit version of Hertz's ST 25 Neo platform, the ST25KNEO-2 includes metal mesh grilles and inline crossover filters. These included filters help support high-pass use when integrating the tweeters with compatible midrange speakers. High-current screw terminals provide a secure connection point for speaker wiring.

The tweeters fit naturally into multi-driver front-stage, door-panel, custom-pod, and show-style audio upgrades where placement and aiming can be planned carefully. Their waterproofed, anti-UV-treated body is designed for exposure to outdoor conditions without discoloration over time. Confirm mounting clearance, amplifier setup, crossover point, and polarity before installation.

Key Features

• 44 mm Compression Tweeter: Compact horn-loaded design for dedicated high-frequency reproduction.
• 100 W Peak Handling: Rated with a 5 kHz, 12 dB/octave high-pass filter.
• 107 dB Sensitivity: Supports strong output with modest amplifier power.
• Neodymium Motor: Keeps the tweeter compact and lightweight.
• Aluminium Dome: Extra-light membrane supports upper-frequency response to 20 kHz.
• Kit Accessories: Includes inline crossover filters and metal mesh grilles.

Design & Installation

The ST25KNEO-2 combines a neodymium N38 H motor, aluminium dome, CCAR voice coil, and FEM-optimized phase plug and loading horn. Hertz specifies body waterproofing and anti-UV treatment for durability in exposed installations. Each tweeter weighs 0.39 kg and uses high-current screw terminals.

Use these tweeters in a properly filtered multi-speaker system rather than as full-range speakers. Hertz specifies the 100 W peak rating with a 5 kHz high-pass filter at 12 dB per octave, and the included inline crossover filters should be installed according to their supplied instructions. Check the 57 mm overall diameter and 29.7 mm mounting-depth dimension before choosing a mounting location.