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Philips 9710M/01

Pair of Philips 9710M/01 8 inch Fullrange Drivers

With a special thanks to Atanas Milchev for submitting his nice pair of 9710M/01

Philips 9710M/01 is one of the most popular vintage fullrange loudspeakers. They were designed for studio monitoring equipment as well as for domestic hi-fi applications. It was used in many speaker systems form seventies like Philips Studio Monitor 8, Sonab V1, Sonab OA5.

Close view of Philips 9710M/01 cone

A close view of the cone shows a long-fiber paper. A manufacturer's number 2103 is stamped on the cone. The surround is "accordion" type without coating.

There is another version of this driver with a coated surround. The coating seems to keep its flexibility trough the passing decades and the T/S parameters of both versions are similar.

There is not separate dust cap - the cone has no opening at its center, which increases the rigidity of its construction.

The gasket is made of cork and sometimes is painted black.

Magnet system of Philips 9710M/01

The magnet system features AlNiCo magnet and a special shape center pole piece with a copper cap. 

Unlike the later ferrite magnet version, the 9710M/01 has underhung magnet system with 11mm thick front pole piece and 8mm voice coil, so the linear excursion is Xmax = ± 1.5mm.

The voice coil is copper ant it is wounded on a paper former.

The unit was assembled with three bolts made of non-magnetic material. 

The chassis is attached to the magnet system by three screws on its side and can be easily removed.

This is the manufacturer's brochure of the ferrite version 9710/M8 Link To Philips 9710M/01 Manufacturer's Datasheet

My Measurements

Driver Properties Thiele - Small Parameters
Chassis material Stamped Steel   Parameter Measured Datasheet
Membrane material Paper Fs 47 Hz 50 Hz
Magnet System AlNiCo Re 5.0 Ω 6.4 Ω
Surround  Paper Qms 2.4 N/A
Voice Coil Diameter 35 mm Qes 0.58 N/A
Nominal Impedance 8 Ω Qts 0.46 N/A
Sensitivity 94 dB/W/m   Vas 60 ltr N/A
Rated Power 10W Le 0.09 mH N/A

SPL Responce of Philips 9710M/01 at 1m on axis and 15 30 deg off axis  SPL Responce of Philips 9710M/01 at 1m on axis and 15 30 deg off axis 

On left - frequency response at 1m with 2.83 V input RED - on axis, BLUE - 15 º off axis, GREEN - 30 º off axis
On right - frequency response smoothed at 1/3 Oct at 0-90º of axis wit a step of 10º

Second, Third and Fourth Harmonic of Philips 9710M/01  in 18 ltr sealed box

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

Burst decay Responce of Philips 9710M/01 at 1m in the Universal Horn

Burst decay response, measured at 1m on axis

The impedance of Philips 9710M/01 in 18 ltr seled box 

The impedance curve in 18 ltr sealed box

Magnet system of Philips 9710M/01

I always feel timidity for any modifications of a vintage speakers, especially when  they were designed by talented engineers
However in the case with Philips 9710 an easy and non-disruptive improvement can be done. In the SPL graph, we can see a sequence of significant peaks and dips in the range of 3-6 kHz. The second harmonic increases in the same range, as is shown in the THD graph. For this behavior I suspected the mutual disposition between the basic and whizzer cones, which are, for my opinion, placed very close which causes an interference in the mentioned range.
The solution is very simple - a tape of open-cell foam material with 8X8mm cut, placed between two cones. The whizzer cone has an angled age, so no gluing is necessary. The result is shown below.

Second, Third and Fourth Harmonic of Philips 9710M/01  in 18 ltr sealed box Second, Third and Fourth Harmonic of Philips 9710M/01  in 18 ltr sealed box

The result of the cheap trick described above. The SPL between 3KHz and 6KHz was significantly improved, The second harmonic in the same region was decreased up to three times. And the most important - the listening tests show more clear and accurate sound image, specially in female vocals and string instruments, compared to the unmodified speaker.


The 9710M/01 was designed for bassreflex boxes. We can see it in various DIY constructions - open baffles, TL and even horn enclosures. Although the response falls abruptly after 17 kHz listeners don't notice a lack of trebles. Any attempts to equalize the response using passive crossover circuits cause a lack of detail and a dull overall performance.
I tried it with various amplifiers, but surprisingly the best result I got with a simple EL84 UL push-pull.  

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