The Impedance mode is provided for general speaker or passive crossover measurements. This gives a 31 point response curve for the impedance characteristics of a transducer or component. The data is given in ohms. Since an RTA has only 31 bands, the resolution of the impedance curve is limited to 31 points. Moreover the test signal is noise averaged in 1/3 octave bands.

This is not enough resolution for producing speaker parameters, which require extremely high detail and accuracy. A swept sine wave analyzer such as LMS is ideal for this purpose. However, even the ability to measure rough impedance curves can be very useful if no other means is available. This enables transducers or passive crossovers to be checked for shorts, opens, or other major defects very quickly. These problems may show up under AC testing, but may not be visible under DC testing with a DMM.