Speakers (e.g. “loudspeakers”) from different manufactures may have differing characteristics. In order to improve audio performance, an audio system may customize audio settings based on characteristics of an attached speaker. Described is a technique for determining speaker characteristics by sending a signal through a filter of the attached speaker. The signal may be a probing signal that produces no audible effect from the speaker. The signal may progress through one or more frequency ranges and an impedance signature may be measured. When the signal progresses through a frequency range, the impedance may be measured and a speaker model type and/or characteristics or condition of the speaker may be determined based on the measured impedance.