Here’s a really useful device from our friends at Whirlwind USA. The Cab Driver is a compact (4.75 W x 4.5 D x 2.5 H inches) device that can be used to test the operation of speaker components within a loudspeaker. An onboard pink noise generator with a small power amplifier can be routed to an assortment of speaker connectors including Speakon NL8 and NL4, ¼-inch TS, and banana jacks. The pink noise output can be adjusted to levels appropriate for driving subwoofers, midrange speakers and compression drivers or tweeters. An XLR line output is provided for feeding the pink noise signal to self-powered speakers.
Four pushbutton switches can be used to perform a DC Ohms Test function to measure the DC resistance of the connected circuit. Three LEDs indicate approximate ranges of 4, 8 or 16 Ohms, and help identify blown drivers in cabinets where the cones cannot be readily observed or in cabinets with multiple drivers in series-parallel configurations. The switches also send 5 VDC to pairs of speaker terminals, enabling the user to observe cone movement for speaker identification and cabling polarity errors.
The Cab Driver can be run via four AA batteries or from an external 6 VDC power supply (not included). Street price of the Cab Driver is around $200 and it comes in (what else?) taxicab yellow!
More info here.