Page 46 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits
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Magnetic Crystal
FIGURE 3-9 Earphones.
Most magnetic earphones or headphones have impedances from 8 V to 32 V
(ohms). However, for lower-power radios, it is recommended to use impedances of
500 V or more. For a very low-powered radio, the crystal earphone or headphone is
the best choice. It has an impedance in the thousands of ohms and is suitable for
crystal radios as well.
Speakers
There will be some radios in this book that are not as low powered and can drive
,loud speakers. A speaker with mounting holes is desired for assembling on a
chassis or board via spacers and bolts. Figure 3-10 shows 3-inch and 4-inch
speakers.
FIGURE 3-10 Loudspeakers.
