Navigation: DIY Audio Projects / Hi-Fi Audio Speaker Drivers (Transducers) / Radio Shack 40-1271 Fullrange Speaker Driver

Radio Shack 40-1271 Fullrange Speaker Driver


Radio Shack 40-1271 Fullrange Speaker Driver

Note - this driver has been discontinued and is no longer being produced. The Radio Shack 40-1271 is an 8" fullrange driver with a dual cone (whizzer). It features an accordian style surround and the cone is curvilinear. The frame is stamped steel and the motor (magnet) is rather small considering the size of the driver. Photograph 01 below shows a front view of the speaker.

Radio Shack 40-1271 Fullrange Speaker
Photograph 01: Radio Shack 40-1271 Full Range Driver - Front View

The specifications listed on the Radio Shack box of the driver are: Impedance 8 ohms, Magnet Weight 81 g, Freq. Response 75 - 20,000 Hz, Sensitivity (SPL) 88 dB, Power Handling (RMS) 5 W, Power Handling (MAX) 10 W, Cone Material Paper

T/S Measurements - Radio Shack 40-1271

Table 01 below shows an average of the driver parameters as measured from fellow DIY'ers.  The driver data has been collected from the Fullrangedriver archives.

Table 1: Average T/S Parameters - Radio Shack 40-1271 Fullrange Speaker

Fs 82.9 Hz
Vas 1.16 cu. ft.
Qts 2.43
Qes 3.3
Qms 9.45
Re 7.9 Ohms
Le 2.1 mH
Mms 7.5 grams
SPL 89.5 dB

This driver will work best on an open baffle or possibly an aperiodic enclosure combined with a low frequency driver or subwoofer to fill in the bottom end. The ultra high Q causes a considerable peak in the frequency response between about 60 and 160 Hz. In an open baffle configuration, the 40-1271 driver needs a baffle width of about 34" in order to flatten the frequency response to about +/-3 dB up to 2 kHz. Above about 2 kHz, the driver begins to beam.


Driver Tweaks - Radio Shack 40-1271

The Radio Shack 40-1271 will need the usual cheap driver tweaks for best performance.  Damping the basket, gluing the motor to the frame and the $0.98 whizzer tweak.

Radio Shack 40-1271 Full-range Driver

Photograph 02: Radio Shack 40-1271 Full Range Driver - Rear View

The frame is made using stamped steel and is relatively light so there will benefits to adding mass (dampening) to reduce the potential of having the chassis "ring". Also, since the motor is not attached very well to the frame, fill the gap with ducseal or better yet with an epoxy. It is also a good idea to cover refelctive surfaces with a sound absorbent material (like upholstery felt). For details and photos see the Fostex FE206E / FE206En driver modifications and tweaks page for some ideas.

The whizzer resonates at about 2 kHz and creates what many refer to as upper mid-frequency "shout". You can try listening to the speakers off axis (about 15 to 20 degrees) from your listening position. Also, there is Marc Wauters 98 cent whizzer tweak. This tweak consists of placing a lightweight piece of foam between the outer edge of the whizzer and the main cone. This tweak help reduce the resonance peak of the whizzer. Unfortunately, Marc has removed this tweak from his site.