Super High Frequency Loudspeaker



The ET-703a is one of the world‘s most efficient and broadband reproduction loudspeakers for super high frequencies. TAD has fine-tuned the ET-703, known as a true rear compression type horn tweeter with this triple-slit fading plug. The 35mm beryllium diaphragm is extremely lightweight at only 0.07gr, and in synergy with the aluminum edge-wound voice coil insulated with an anodized aluminum coating film, combines outstanding response with a wide frequency bandwidth and high input power. The phasing plug is triple-slit type with slit spacing of approx. 5 mm, enabling reproduction up to 45 kHz. The magnetic circuit is provided by samarium-cobalt magnet that can ensure stable output even in high-temperature operation, and the magnetic flux density can reach 2 Tesla. The ET-703a will further revolutionize the world of digital sound monitoring.

Diaphragm with integrated surround made of pure beryllium

Using our unique vacuum evaporation technique, we have succeeded in integrating the surround and diaphragm with beryllium.
By designing the resonance frequency of the surround higher than 50 kHz, the negative effects on the audible frequency band are eliminated. Furthermore, despite the large 35 mm diaphragm, the diaphragm is ultra-lightweight at 0.07 g, and the high resonance frequency is as high as 45 kHz. As a result, a wider reproduction bandwidth, excellent transient characteristics, and outstanding resolution are achieved.

Rear compression type horn tweeter

A rear compression type horn tweeter is produced by hollowing out the inside of the pole yoke to create a sound path and mounting the diaphragm from the rear. This method ensures ideal phase equalization up to the ultra-high frequency areas. The effect of surround vibration is minimized, resulting in a highly transparent sound and smooth extension of high-frequency.

Triple-slit ultra-precise phasing plug

A triple-slit phasing plug, which was precisely designed using a computer based on acoustic theory, is installed. The good equalization characteristics provide smooth frequency response characteristics up to above 30 kHz, reproducing sensitive ultrahigh frequencies with high resolution.
The surfaces of the phasing plugs are finished by high-precision machining with a tolerance of 20 μm to ensure high reliability.

Voice coil of pure aluminum edge-wound wire

A voice coil of edge-wound wire made of anodized pure aluminum is used. The conductor occupancy in the magnetic circuit is increased to the utmost limit to achieve high efficiency. In addition, heat-resistant materials are used for the voice coil bobbin and adhesives to ensure stability to withstand large input power of 30 W.

Rare-earth Samarium-cobalt magnet magnetic circuit

Rare earth samarium-cobalt magnets with high magnetic energy are built into the limited volume of the super tweeter. Its powerful magnetic characteristics, combined with the electromagnetic soft iron showing extra low carbon and low impurity used for the pole yoke and plate, constitute an ultra-strong magnetic circuit with a magnetic flux density of 2 Tesla and a total flux of 40x10-4 Wb.

ET-703a Specification

Rated impedance: 8 ohms
Frequency Response: 5,000 to 45,000 Hz
Voice coil diameter: 35 mm (1 3/8 in.)
Equalization system: Triple-slit rear compression type
Mounting Information:
Mounting on the baffle
Baffle opening diameter: 81 mm (3 3/16 in.)
Mounting pitch: 98 mm (3 55/64 in.) (for 4-hex socket head cap screws)
On to the enclosure: 25 mm (63/64 in.) (for 2-wood screws)
Rated input power: 15 W for crossover frequency at 5 kHz -12 dB/oct
Maximum input power: 30 W for crossover frequency at 5 kHz -12 dB/oct
Sound pressure level: 107 dB at 1 W, 1 m (anechoic conditions)
Crossover frequency: 5000 Hz or higher (-12 dB/oct or higher)
Total magnetic flux: 4.0 x 10-4 Wb
Magnetic flux density: 2.0 Tesla
External dimension: φ80 mm x 74 mm (Depth)
(φ3 5/32 in.×2 29/32 in. (Depth))
Weight: 1.1 kg (2 lb 7 oz)
Accessories: Mounting flange (1), Mounting packing (1),
 Hex socket head cap screws (4), Washer (4),
Cross-recessed head wood screw (2),
Hex wrench (1), Instruction manual (1)




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 2.28x10-3Wb, 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



This 1" Throat driver is also based upon the very successful Model TD-2001, which has been the mainstay in the professional sound industry for this size driver. 

Among the significant improvements designed by the TAD Engineers is the redesigned Aluminum 3 slit phasing plug. As with the TD-4003, we have made subtle improvements to the shape and material which has contributed to the improved frequency response. Our use of Alnico5 has achieved an increased magnetic flux density of up to 1.95T.  As with the TD-4003, we have applied the Direct Power Coupling technology which allows direct connection from the speaker wire to the Beryllium Diaphragm thereby reducing unwanted resonance caused by AC current interference. 

Overall, TD-2002 delivers excellent performance and durability with improved clarity and linear response over a wider frequency range at an SPL of 111dB (1W,1m).

TD-2002 Specification

Rated Impedance: 8Ω
Frequency Range: 800-20,000 Hz
Rated Input Power: 10 W
Maximum Input Power: 40 W
Sound Pressure Level: 111 dB (1W,1m)
Total Magnetic Flux: 7.42 x10-4 Wb
Magnetic Flux Density: 1.95 T
Lowest Recommended Crossover: 800 Hz
Voice Coil Diameter: 48 mm
Phasing Plug: 3-slit rear type
Hole Size for Throat Connection: 25.4 mm
Mounting Dimensions: 57.2 mm (3 holes), 76.2 mm (4 holes)
Weight: 6.9 kg
Dimensions (diameter x depth): 141 x 137 mm

Diaphragm repair parts