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Pioneer PIM-8L

Pair of Pioneer PIM-8L  8 inch Fullrange Drivers

Pioneer PIM-8L/PIM20A is a product of Fukuin Electric Ltd and can also be found under brands Hamlins and Lafayette. This driver is in production from the late fifties. Some audiophiles call this driver "The poor-mans Altec 755A" or even "The Japanese answer to 755A". However the construction of the PIM-8L and its performance are completely different from 755A. Actually PIM8L is a dual cone driver. The upper frequency range cone has firmly connection to the voice coil in its center and flexible connection to the LF cone at its periphery. That's why the manufacturer called the construction "Mechanical 2-way". The LF cone was perforated at the back as a way to avoid sealing an air volume between two membranes. The surround is a part of the cone and it has a lubrication, that seems to be hardened by ages. That's why the resonance frequency is higher than specified by manufacturer.

This is the only manufacturer's brochure that include PIM-8L I found.Link To Pioneer PIM-8L Manufacturer's Datasheet

The Factory SPL of Pioneer PIM20 PIM8L

This a manufacturer's SPL graphics of PIM-20A

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Stamped Steel    Parameter Measured Datasheet
Membrane material Paper Fs 87Hz 55-70Hz
Magnet System AlNiCo  Re 12.4 Ω N/A
Surround Impregnated Paper Qms 8.4 N/A
Voice Coil Diameter 29 mm Qes 0.86 N/A
Nominal Impedance 8 Ω/16Ω Qts 0.78 N/A
Sensitivity 94 dB/W/m   Vas 17 ltr N/A
Rated Power 6W Le 0.61 mH N/A

SPL Responce of Pioneer PIM-8L 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.

Second, Third and Fourth Harmonic of Pioneer PIM-8L in18ltr sealed box 

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

Burst decay Responce of Pioneer PIM-8A at 1m in the Universal Horn

Burst decay response, measured at 1m on axis

The impedance of Pioneer PIM-8A in 18 ltr seled box

The impedance curve in 18 ltr sealed box


Maybe due to its age this driver needs support in the lower frequency. It has clear and detailed middles and a notable lack of trebles. The best application to my opinion is as a wide midrange in high-efficiency multy-way system.

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