Does sensitivity have anything to do with the lack of fidelity at low volume, I'm sure they had a better amp than my 10 year old Yamaha integrated stereo 100 wpc. or is it Power supply??/
Ottguit
The answer is "it depends on the speaker's overall frequency response".
Sensitivity is usually measured at one frequency, 1000 Hz, but not always. It tells you nothing about sound at frequencies higher or lower than that. Sometimes sensitivity is an "averaged" value arrived at by measurements at different frequencies. It is only one number, and almost always tells you little about sounds, such as cymbals, that involve different frequencies.
A better way of answering your question comes from looking at a graph of the frequency responses measured across the full audio range – a frequency response curve. The vertical axis is loudness or sound pressure level (SPL) in decibel units (dB), measured with a microphone 1 meter away from the speaker, with the amplifier delivering 2.83 volts (1 watt if the speakers impedance is 8 ohms). The horizontal axis is frequency in Hz and is shown in a log scale to squeeze the full audio range into a reasonable size.
Below is the frequency response curve for the B&W CM1 (
http://www.soundstagenetwork.com/measurements/speakers/bw_cm1/). It has 3 traces on the graph, where the measuring microphone was directly in front of the speakers (on-axis) as well as 15° and 30° off-axis. If you go to this web page, you can see other graphs measured at 45°, 60° and 75° off-axis angles. These speaker measurements published online by SoundStage Network (
http://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=16&Itemid=18) done by Canadian National Research Council, are considered the best available measurements of speakers.
The CM1's response curve is far from the ideal flat curve. In fact, there is a prominent dip in the range from about 1.3 kHz to 5 kHz. Across that range, the CM1 speaker is much less sensitive than B&W's stated 84 dB. That may be the answer to your question.
I found a different curve for the CM6 (
http://www.soundandvision.com/content/bowers-wilkins-cm6-s2-speaker-system-test-bench ). See the purple trace below. It can be hard to compare frequency response curve done by different people, but for comparison, the red trace is the CM1 s2 speaker. I'd sooner believe the SoundStage curve.
I couldn't find a frequency response curve for the original Dynaco A-25, but I did find a curve for the Madisound's modern "clone" of the A-25, the A-26 Kit. Frequency response (on-axis) is the red curve, and speaker impedance is the blue curve. I don't know if the A-26 is representative of your A-25s, but this curve is clearly flatter across the mid range than either of the B&W CM speakers.
