OTOMON Laboratory　(音門ラボ)/Product details page

Legend 70s year special order made Lo-D (Hitachi) H-70HD horn tweeter x 2. This is special order made horn tweeter of Hitachi, brand name Lo-D, model H-70HD.

Frequency band 2kHz to 20kHz 104db sensitive. Best matching for tube amplifier and can be combine with full range speaker.

Specification:

H-70HD was produced by carving one by one from an aluminum round bar.
As a result, a two-degree-of-freedom system with a special acoustic circuit can be adopted for the relationship between the diaphragm, horn, and air chamber, and a flat characteristic with a deviation width of 6.5 dB up to 20 kHz is realized.

In horn speakers, non-linear distortion occurs due to the asymmetry of the diaphragm clamp and the non-linearity of the air due to the excessive sound pressure at the horn throat.
In H-70HD, the machining accuracy is improved in order to improve the asymmetry of the diaphragm clamp. Furthermore, in order to make the clamp strong and stable, a special resin plate is used at the bottom of the diaphragm, and a duralumin spacer is used to secure a gap of 0.3 mm in the air chamber.
For non-linearity of air due to excessive sound pressure in the horn throat, the ratio of the area of ​​the horn throat to the area of ​​the diaphragm, the distortion factor in the case of resistance control and mass control, the length of the horn, etc. are output. At a sound pressure level of 100 dB (input 0.1 W), the distortion factor due to overload is designed to be 1% or less at twice the cutoff frequency or more.

High-purity Mylar is used for the diaphragm in consideration of its lightness and durability against high temperature and humidity.
The diameter of the diaphragm dome is 14 mmφ, and the weight of the vibration system is reduced by using a special lightweight wire for the voice coil.

With a horn speaker, the directivity becomes sharp. To improve this, the H-70HD is equipped with an acoustic lens in the shape of a V. This acoustic lens has an excellent diffusion effect by designing the lens with a ratio of entrance to exit of 10: 7 and a thickness of 15 mm.
When the acoustic lens is attached, the directivity improvement of 6dB is realized at 10kHz.

Outer diameter 7.3 cm
Opening diameter 6.9 cm
7.0cm (listed in another catalog)
Baffle hole 7.4cm
Voice coil diameter 1.4cm
Rated input 20W (with designated network)
Output sound pressure level 104dB / W / m
Voice coil impedance 8Ω
Playback frequency band 2kHz to 20kHz
Cutoff frequency 1.5kHz
fo 2.3kHz
Crossover frequency 3kHz or higher
Total magnetic flux 101,000 maxwell
Magnetic flux density 11,300 gauss
Depth 15.9 cm (17 cm with acoustic lens)
Weight 1.7kg (2.1kg with acoustic lens mounting frame)