Sure there are CLIO and AP etc, all $$$$+. However: Cheap soundcard and some junk bin contents. Important features are two separate inputs and when possible, low impedance line out / hp out (for this unit I bridged the hp out 100 ohm resistor internally with a 1 or 2 ohm resistor), or external amp that can supply some more current for speaker stuff. And REW with a computer. That's it. One can now measure impedance (and phase) of transducers.