Would an audio signal be degraded by adding a 0.45 ohm resistor?
The DC resistance you measure with a multimeter has little to do with the impedance and/or frequency response across the full audio range. If you want to diagnose this properly, you need to hook them up to a network analyzer.

Just putting a resistor in series with the lead will increase the apparent output impedance of your amplifier, which will likely have a serious effect on frequency response. (I.e., the "damping factor" will go way down.) I wouldn't recommend it.