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Mark Audio CHS 70A

Pair of Mark Audio CHS 70A Fullrange Drivers

The CHS-70 is another fullrange driver from Mark Audio - a manufacturer, well known to many DIY-ers. It is mechanically similar to the CHR-70 series drivers, but its major design features are more advanced chassis construction, improved suspension and new shape of the dust cap.

This is the manufacturer's brochure for the nearest CHR-70A model  Link To Tang Band W4-1320 Manufacturer's Datasheet

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Glass fiber injected plastic   Parameter Measured Datasheet
Membrane material Aluminum Alloy Fs 70.5Hz 67.9Hz
Magnet System Ferrite Re 7.0 Ω 7.2 Ω
Surround Rubber Qms 2.07 2.40
Voice Coil Diameter 20 mm Qes 0.65 0.69
Nominal Impedance 8 Ω Qts 0.50 0.54
Sensitivity 85.4 dB/W/m   Vas 4.7 ltr 5.5 ltr
Rated Power 20W Le 0.05 mH 0.035 mH

Mark Audio CHS 70A SPL Responce at 1m on axis and 15 30 deg off axis

Frequency response at 1m with 2.83 V input RED - on axis, BLUE - 15 º off axis, GREEN - 30 º off axis 

Mark Audio CHS 70A Second, Third and Fourth Harmonic in 18 ltr sealed box

The second, third and fourth harmonic curves measured at 2.83V input RMS. There a noticeable peak of distortion at about 1500Hz.
We can see corresponding impedance and phase bumps at the graphics below.

Mark Audio CHS 70A Burst decay Responce at 1m in 18 ltr sealed box

Burst decay response, measured at 1m on axis

Mark Audio CHS 70A impedance in 18 ltr seled box

The impedance curve in 18 ltr sealed box


The CHS-70 sounds really smooth, with very good micro dynamics and without a trend for irritating overtones, some metallic-cone drivers have. This fullrange speaker will perform well with a properly designed open baffle or a compact TWQT construction.

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