[Rpell]

I'm wondering if anyone knows what source impedance the ER-4P/4S were designed to be driven from, and how significantly their sound may vary "from advertised" at different source impedances? I'm asking because output (source) impedance varies among amplifiers, from near zero ohms (many dedicated amplifiers) to the "standard" 120 ohms (many headphone-out jacks)--a variation greater than the 75-ohm difference between the ER-4P and ER-4S.

In other words, if adding 75 ohms to the 4P makes it sound like the 4S, how is changing from a zero-ohm-output amplifier to a 120-ohm-output amplifier going to affect its sound? And what output impedance should be used as a reference?

 

[Budgie]

It would only affect the tone if there is a capacitive element in the circuit. Otherwise it is only a question of efficency. There may be a slight change in bass quality due to the difference in dampning factors, (but that is a subject of debate). I dont know the ety's personnely, though. Did you try an e-mail to Etymotic?