Perhaps something of interest -- an entry from
Ashley J's blog --
On his blog Ash wrote:
I ... present measurements made of both an active ADM9.1 and a passive version driven by a low distortion Class A test amp.
Both speakers were measured at a nominal 86 dBa at 0.5 Metres. The Mike was a Bruel & Kjaer type 4165 measuring microphone and the source was the low distortion output of an HP339.
Both the active and passive version of the ADM9.1 first played a 100 Hz tone.
I had to adjust the verticals on the graphs because even though the scales were the same the Y-axis was stretched for the passive plot. I also colour-coded them (
red passive,
blue active) and superimposed the graphs best I could, so the comparison is easier.
The active plot is better, but apart from the peak at 300 Hz I'm not seeing a huge difference between them. The distortion components are mostly 50 db below the signal, which may not be audible in the average room.
Here are the superimposed plots for the active and passive ADM9.1, this time with a 3 kHz signal. As before, I've colour-coded the plots ââ'¬â€ red is passive and blue is active ââ'¬â€ and superimposed them.
Again, the passive plot (red) is worse, but the distortion components are mostly 50 db below the signal, apart from some peaks. However, I see that the signal is considerably higher for the passive ADM -- it's at ~+7 db vs 0 db for active one, so all distortion components for the passive version may be ~7db higher across the board. If you drop the signal by ~7db the plots probably are less different, but I would imagine that the active is still better.
The question is whether the reduced distortion translates into a real subjective difference.
I'd be interested in knowing what you make of the active and passive plots and the subjective difference that a listener might hear.
Joe