The SP4 can be used with any receiver capable of driving a 4-ohm load. The speaker is passive (non-amplified), ensuring no susceptibility to RFI in the present of a transmitted signal. The SP4’s custom-built, wide-range driver has excellent sensitivity and deep bass response.
The A/B switch on the front panel of the SP4 can be used to select one of two mono sources. Further, when used in conjunction with a second SP4 this switch can be used to select one of two stereo sources. The Elecraft K4 transceivers take full advantage of this feature, since both provide rich binaural audio effects (AFX), as well as user-adjustable left/right balance between main and subreceiver audio.
Rear-panel input jacks accept either mono or stereo cables, simplifying station wiring. An output jack is provided for connection to a second SP4. When two SP4s are used, the A/B switch on the first unit controls source selection for both.
High Performance Matching Speakers were designed by audio expert Dr. Bruce Edgar.