Philips AD 1256/M8
AD 1256/M8 is the largest fullrange loudspeaker, manufactured by Philips. It was introduced in 1969 as the successor to the AD 5200M.
A close view of the cone shows a long-fiber paper. This is
the version with the specific brown color of the Philips cones. The surround
is "accordion" type without coating.
There is another later version with black colored cone.
Audiophiles who compared both versions rematk the superior sonic
performance of the brown one.
There dist cap is made of acoustically transparent textile.
The gasket is made of cork.
The magnet system
features AlNiCo magnet and a special shape center pole piece
with a copper cap.
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.
Unfortunaly I couldn't find any manufacturer's datasheet for this driver.
My Measurements
| Driver Properties | Thiele - Small Parameters | ||||
|---|---|---|---|---|---|
| Chassis material | Stamped Aluminium | Parameter | Measured | Datasheet | |
| Membrane material | Paper | Fs | 48 Hz | N/A | |
| Magnet System | AlNiCo | Re | 8.1 Ω | N/A | |
| Surround | Paper | Qms | 6.3 | N/A | |
| Voice Coil Diameter | 35 mm | Qes | 0.63 | N/A | |
| Nominal Impedance | 8 Ω | Qts | 0.58 | N/A | |
| Sensitivity | 98 dB/W/m | Vas | 96 ltr | N/A | |
| Rated Power | 30W | Le | 0.16 mH | N/A | |
Frequency response at 1m with 2.83 V input RED - on axis, BLUE - 15 º off axis, GREEN - 30 º off axis
The second, third and fourth harmonic curves measured at 2.83V input RMS.
Burst decay response, measured at 1m on axis
The impedance curve in 36 ltr sealed box
This is the SPL graph at 1m of both tested units - one very close matched pair.
Conclusion
The best application of Philips AD 1256/M8 are open baffle constructions. A large transmission line is also possible. The driver delivers consistent and well-focused sound. A supertweeter support is recommended.
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