TAD TD-4001


The TD-4001 successfully achieves all the design objectives we set forth: very high efficiency, wide and perfectly flat response from 600Hz to 20kHz, and low distortion.



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 (1W,1m), 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 2.28×10-3Wb, with flux density of 2.00T, 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.


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.


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


TD-4001 Specification

Rated Impedance: 16 Ω
Frequency Range: 600-20,000 Hz
Rated Input Power: 30 W
Maximum Input Power: 60 W
Sound Pressure Level: 110 dB (1W1m)
Total Magnetic Flux: 2.28 x10-3 Wb
Magnetic Flux Density: 2.00 T
Lowest Recommended Crossover: 600 Hz
Voice Coil Diameter: 101 mm
Phasing Plug: 5-slit rear type
Hole Size for Throat Connection: 49.2 mm
Mounting Dimensions: 101.6 mm (4 holes)
Weight: 12.6 kg
Dimensions (diameter x depth): 178 x 155.5 mm

Diaphragm repair parts

Brochure & Manual

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