Originally Posted by gmoney9438
hey guys, I know this is a bit off topic and it doesn't affect orthos, but how does the 8x ohm rule affect a dynamic headphone? I have a Dacport (10ohm output impedance) and i'm using it with both my Mad Dogs and my W1000x's. Is there a significant difference if I change to a lower output impedance device?
For solid state or transformer coupled tube amplifiers, tThe effect of high output impedance is most noticeable with headphones whose impedance changes significantly with frequency, such as many Sennheisers and Beyerdynamics. Typically (not not always), this interaction results in a boost in the midbass around 100-120Hz. For many people, this is actually a nice sound. One of the more common comments by people who do the dacport/dacmini mod is that sound becomes more "clinical" sounding, which is usually the result of a shift towards treble presence or the lessening of bass/midbass.
Headphones with a flat impedance curve will not have much frequency change. Instead, the effect of output impedance here is on damping itself which is how much control the amplifier has over the driver. This may affect transient/impulse response and settling times. For the most part, the effect of output impedance here is very difficult to detect even for a trained listener.
For OTL (output transformerless) tube amps, the output impedance interaction is a little more complex. Here, the damping factor may not be as important as impedance matching, which in the simplest terms is what maximizes power transfer from amp to headphone.