My friend did quick and dirty preliminary impedance measurements of the KZ ZS5, KZ ZSR, and EDR2: plotted are frequency [KHz] vs. impedance [ohm].

The single-driver EDR2 shows a flat response.

The triple-driver ZSR has rather high impedance that drops above 3 KHz. This means that, if you increase the output impedance of your player, you get a drop in the treble on your frequency response curve.

The quad-driver ZS5 has a rather low impedance that starts climbing beyond 1 KHz. This means that, if you increase the output impedance of your player, you get increased mids and treble on your frequency response curve...that's what Coil always tried to tell me with his setup for the KZ ZS5.

My iPhone 5S has an output impedance of...hmmm...either 1 ohm or 2.3 ohm.

Putting my audioquest dragonfly in front of it yields an output impedance of 0.3 ohm.

I'll have to try both on my ZS5, but they are still with my friend.

IMPEDANCE FOR DUMMIES (including myself)

I really had problems understanding the read-ups, therefore here in simple terms...I hope it is understandable.

1. The output impedance of a player determines how much voltage arrives at the earphones.

2. A low output impedance is desired, which means a high voltage arrives at the earphones.

3. A single-driver earphone has a flat impedance across the frequency spectrum and the player's output impedance does not influence the frequency response curve.

4. Multi-driver earphones have funny impedance-frequency curves.

5. For any given output impedance: the higher the earphone's impedance at a certain frequency, the louder the signal will be at this frequency. If the source is 100 ohm, then the voltage (loudness) in the earphone will be higher at, let's say, 600 ohm on the curve than at 300 ohm.

6. If the output impedance of the player is increased, there is less juice entering the earphones and the voltage (loudness) drops, but less so at 600 ohm compared to 300 ohm.

7. Points 5 and 6 appear to not make any sense: if the earphone's impedance (resistance) is increased, this should result in a drop in voltage/loudness, but the opposite is the case...the trick is that the resistor is BEHIND the earphones' coil and not in front of it. The innerfidelity graphic below shows this quite well.

8. This can be compared to a bathtub. Water (voltage) comes under pressure out of the faucet (player). The plug in the bathtub that keeps the water in can be compared to the impedance in the earphone. The better the plug seals, the more water (voltage/loudness) there is in the earphone/bathtub. And all the fun is in the water...

Click to expand...