Accuphase F-25 (1994–1998)
Four-way active crossover with modular design, switchable slopes, and precision level controls
Overview
The Accuphase F-25 is a transistorized electronic frequency dividing network designed for high-end active speaker systems. Manufactured by Accuphase Laboratory, Inc. (originally Kensonic Laboratory, Inc.), it supports configurations from two to four ways using optional amplifier and filter units. The basic setup includes one filter amplifier and two line amplifiers, with expansion possible by adding DN-25 and LA-25 series units. Input and output are fully balanced, and the unit features a phase switch for each band, independent left/right level controls, and a subwoofer mix selector on the rear panel.
Specifications
| Maximum Input Level | Balanced: 7.0V, Unbalanced: 7.0V (20 Hz–20 kHz, ≤0.01% THD) |
| Total Harmonic Distortion | 0.003% (20 Hz–20 kHz, 2.0 V output) |
| Frequency Response | 20 Hz–20 kHz ±0.2 dB; 4 Hz–180 kHz ±3.0 dB |
| Gain | 0 dB |
| Crossover Slope | –12 dB/oct, –18 dB/oct, –24 dB/oct (switchable) |
| Input Impedance | Balanced: 40 kΩ, Unbalanced: 20 kΩ |
| Output Impedance | Balanced: 50 Ω, Unbalanced: 50 Ω |
| Minimum Load Impedance | 600 Ω (Balanced and Unbalanced) |
| S/N Ratio | 100 dB (0.5 V output, IHF-A weighted) |
| Attenuator | 0 dB / 10 dB (via ATT switch on line amplifier) |
| Level Adjustment | 0 to –8 dB (0.5 dB steps), –8 to –20 dB (1 dB steps), –∞ |
| Crossover Frequencies | 21 points: 70, 100, 130, 180, 250, 290, 300, 350, 500, 650, 800, 1,000, 1,200, 1,800, 2,500, 3,500, 5,000, 7,000, 8,000, 10,000, 12,500 Hz (via optional boards) |
| Power Supply | 100 VAC, 50/60 Hz |
| Power Consumption | 32 W |
| Dimensions | 475 mm (W) × 170 mm (H) × 394 mm (D) |
| Weight | 15.4 kg |
Design
The F-25 uses a GIC (Generalized Immittance Converter) filter circuit with Gaussian curve design for optimal phase and impulse response. It employs an s-Gretta current feedback amplifier for high-frequency stability. Crossover characteristics are set via interchangeable frequency boards, and the unit features a modular construction: the F-25V version has detachable filter and line amplifier units (DN-25V and LA-25V), while the input board is directly soldered to XLR terminals—a design noted as difficult to service. The LA-25 and DN-25 units are compatible across F-25 and F-25V models.
Context
The F-25VM, released in February 2001, is a dedicated variant for bi-amping the JBL M9500 and Project K2S 9500/S 7500 speakers, using fixed 18 dB/oct slopes and the DN-25VM amplifier with FB-25M frequency board. The F-20 is a two-way version of the F-25; three- or four-way operation requires stacking. The F-15L is a less flexible three-way alternative offering only 12 and 18 dB/oct slopes.
Market
The F-25V originally sold for ¥390,000; the F-25VM for ¥440,000. Optional LA-25V and DN-25V units were priced at ¥60,000 each, frequency boards at ¥15,000. As of 2026, used units list for $3,500 on US Audio Mart and ¥178,000 on Audio Union. Frequency modules are hard to find, with some selling for over $500; custom boards are now made by third parties. A known issue is persistent crackling in one channel, traced to FETs, op-amps, or capacitors. Repairs require replacement of electrolytics and op-amps. Units have been sold with manuals and rate 8/10 in cosmetic condition.
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