Rutcho's Audio Page dedicated to Hi-End Audio Systems Fullrange Speakers Tube Amplifiers

Ruitcho's page dedicated to hi-end audio Blackswift Audio Logo

Sonido SFR-175 Alnico

Pair of Sonido SFR-175 Alnico 7 inch Fullrange Drivers

After the successful presentation of its fullrange drivers on the market, Sonido introduced Alnico magnet line. I took a sample of SFR-175 AlNiCo thanks to my friend Peter Haralanov - an audiophile from Bulgaria.

Close view of Sonido SFR-175 terminals and cone

The Alnico series has the same paper as the ceramic drivers. We can see the manufacturer's stamp on the back

The surround is coated textile with accordion shape.

The driver has a wooden phase plug, fastened with a screw through the magnet system and can be easily removed.

This is the manufacturer's datasheet Link To Lorenz S-888 Manufacturer's Datasheet

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Die-cast aluminum alloy   Parameter Measured Datasheet
Membrane material Paper Fs 54.2Hz 54 Hz
Magnet System AlNiCo Re 6.9 Ω 7.2 Ω
Surround Impregnated Paper Qms 5.1 14.7
Voice Coil Diameter 28 mm Qes 0.43 0.35
Nominal Impedance 8 Ω Qts 0.42 0.34
Sensitivity 92.7 dB/W/m   Vas 21 ltr 27 ltr
Rated Power 24W Le 0.24 mH 0.25 mH

Sonido SFR-175 Alnico SPL Responce at 1m on axis and 15 30 deg off axis  Sonido SFR-175 Alnico 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
On the right - the frequency response with the phase plug removed.

Sonido SFR-175 Alnico  Second, Third and Fourth Harmonic in 18 ltr sealed box

The second, third and fourth harmonic curves measured at 2.83V input RMS.

Sonido SFR-175 Alnico Burst decay Responce at 1m in the Universal Horn

Burst decay response, measured at 1m on axis

Sonido SFR-175 Alnico impedance in 18 ltr seled box 

The impedance curve in 18 ltr sealed box


SFR-175 Alnico is full-bodied fullrange driver with calm and detailed performance. It is suitable for various enclosures as well as an open baffles.

Arrow up icon To The Top Arrow up icon