Quad ESL-63 Gradient SW-63

Elektrostatic speakers with woofers.

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Quad

This speaker consists of two fixed electrodes and a diaphragm placed between them.
When a high voltage is applied to the vibrating membrane to generate static electricity and an audio signal is sent to the fixed electrode, a Coulomb force acts between the vibrating membrane and the fixed electrode to move the vibrating membrane and produce sound.
This method does not require any strength because the diaphragm moves uniformly over the entire surface. It can be set to a very light diaphragm and can be driven with very little energy. It also has advantages such as good impedance matching with air and no need for a cabinet.
The ESL-63 has succeeded in generating all frequencies at one point based on this system.

Since a general electrostatic speaker is plane driven and tends to be plane wave, the listening position was limited.
To solve this problem, in the ESL-63, the fixed electrode is divided into seven concentric rings and a delay circuit is set for each of them. By generating a signal delay of approximately 24 usec per stage from the inner circumference to the outer circumference, for a total of approximately 168 sec, we have succeeded in generating a spherical wave from a flat vibrating membrane. By this, the sound source is located approximately 30 cm behind the vibrating membrane and can freely respond to changes in directivity caused by changes in frequency.

Gradient

Gradient is a Finnish brand. It is a pair of sub each with two speakers configured for dipole inserted in a cabinet designed to mate perfectly to the Quad 63 also reaching the important purpose of bringing the Quads to a more correct height from the ground. The set is very nice and seems to have in front of a single speaker.

WARNING the system is equipped with electronic crossover, therefore it requires a second stereo power amplifier for driving the sub woofer, moreover settable configuarzione in series or parallel and then with an impedance of 16 ohms or 4

The cut is fixed at 115 Hz and the frequency response is estasa up to 28 Hz (-3dB)