DIAPHRAGM. The TD-4001 employs a pure beryllium diaphragm 3-15/16 inches (100mm) across. Beryllium is a light but very rigid material that features very high-speed sound propagation. The weight of the dome section has been reduced to a mere 1g contributing to the very high efficiency (110dB/W) of this driver.

VOICE COIL. The TD-4001 employs an aluminum ribbon voice coil, insulated by alumite film and wound edgewise on the bobbin. The voice coil has a small mass yet offers a high conversion efficiency. The bobbin is formed of polyimide film, displaying excellent heat resistance to temperatures as high as 752ºF (400ºC).

MAGNETIC CIRCUIT. Total magnetic flux is 228,000Mx, with flux density of 20,000G, thanks to the use of a very heavy (6 lbs. 10 oz./3kg) alnico 5DG magnet. An oxygen-free copper shorting ring prevents impedance rise, resulting in low distortion.

DESIGN. The TD-4001 is of the rear compression design, which eliminates the resonance and phase distortion produced by a surround. It also eliminates cavity resonance interference, achieving very flat frequency response, extremely natural sound and superb definition. A phasing plug helps smooth the response of extra high frequencies.

CROSSOVER. We recommend the use of a crossover frequency of 600Hz or higher, and a cutoff slope of 12dB/oct. or sharper.

TD-4001 SPECIFICATIONS Voice coil impedance: 16 ohms. Voice coil diameter: 4 inches/l0lmm. Equalizing system: 5-slit type. Frequency range: 600 - 20,000Hz. Maximum input power: 60 watts (600Hz -12dB/oct.). Sound pressure level: 110dB/W (1m). Crossover frequency: over 600 Hz (-12dB/oct.). Total magnetic flux: 228,000 maxwells. Magnetic flux density: 20,000 gauss. Hole size for throat connection: 1-15/16 inches/49.4mm. Mounting dimensions: 4 inches/l0l.6mm (4 holes). Weight: 29 lbs. 12 oz./13.5kg. Outer dimensions (diameter x depth): 7 x 6-1/8 inches/178 x 155.5mm.