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Radio Shack 40-1197 (FE103) Speaker Driver

Radio Shack 40-1197 Speaker Driver

Note - this driver has been discontinued and is no longer being produced. There has been a lot of controversy in the past surrounding this driver. Some people claim it to be a Fostex FE-103 made for Radio Shack, while others say that the drivers only share a few similarities. It is clearly not identical to a FE-103. It appears that the cone material and frame are different but that the motor is the very similar. The FE-103 is reported to have a touch less bass than the 40-1197, while the FE-103 is more extended and better in the high end. Measurements have shown this to be true. The 40-1197 has a higer Q than the FE-103 which results in more bass response, while frequency measurements show that the FE-103 has a smoother and more extended response. Regardless, the 40-1197 is a very well regarded driver that has been used in a wide variety of DIY speakers projects with a great deal of success. Unfortunately, the Radio Shack driver is no longer available new, but it can occasionally be found forsale on audio forums or eBay. The pictures show two of the many boxes that the 40-1197 driver has been packaged in over the long period that the driver was produced.

Radio Shack 40-1197 Blue Box

Radio Shack 40-1197 Purple Box

Measurements - Radio Shack 40-1197

The measured frequency response of a 40-1197 driver is shown in the plot below. I don't know what version of driver these measurements were taken on. The Single Driver Website indicates that the measurments were taken by Steve Sedmak at a distance of 1m, on an infinite baffle at 0, 15, 30, 45, and 60 degrees with no smoothing applied. The measurement system was CLIO.

40-1197 Frequency Response Curve

The table below shows the Thiele/Small Parameters for two different 40-1197 drivers. The first of the two parameters is an average of early 40-1197 drivers, while the second number is average of later drivers. It is unclear where these parameters originated from.

Fs 86 Hz 79 Hz
Vas 0.1982 ft3 0.2207 ft3
Qts 0.4282 0.3521
Qes 0.4921 0.3882
Qms 3.309 3.2024
Le 0.1295 mH 0.1407 mH
Re 8.088 Ohms 7.958 Ohms
Mms 1.81 grams 1.9 grams
SPL 90.5 dB 90.6 dB

Driver Tweaks - Radio Shack 40-1197

Radio Shack 40-1197 Driver

Adding Ductseal the basket of the 40-1197 helps imrpove the sound. Ductseal is inexpensive (about $5) and available at most lumber yards (such as Home Depot), typically found in the electrical section. The picture above shows a stock driver and below is the driver after ductseal has been applied to the frame and between the magnet and the frame. See the modifications and tweaks for the Fostex FE103En fullrange speaker driver for more examples.

Duct Seal on 40-1197 Frame

Project Links and Enclosure Plans - Radio Shack 40-1197