Loudspeaker Designs and Articles for the DIY Enthusiast
Curt: Part of my design regimen is to measure the HD of every driver in hopes of minimizing the effects of driver distortion by careful selection of crossover
points. With the RS225, SB15, and 22TFF there were simply no significant distortion artifacts to consider. The Anthologies exhibited THD in the low tenths
of a percent, which is quite good. The top plot is at 2.8 volts. The lower one roughly 10 dB higher at 8 volts.
On the 8 volt plot shown below, you can see the 2nd harmonic rising with the main response in the tweeter, and the woofer below 100 Hz. While this does
look ominous, the relative level compared to the main response only increases slightly at the frequency extremes. Tweeter 2nd harmonic does continue to
increase above 5K to about 1%, but this 2nd harmonic distortion is relatively innocuous and will provide a sense of 'air' to the higher frequencies.
Lastly, a horizontal response plot derived from measurements made every 15 degrees up to 90 degrees, showing excellent directivity up to the point where
the tweeter starts beaming. This is actually the same information shown in the curve family chart above, just displayed differently.
Statement II performance
in a smaller, more cost
You be the judge...
Below is the measured horizontal curve family from 0 to 90 degrees off axis. Note there is very little change in the response off axis up to 60 degrees off axis
and even at 90 degrees off axis the response is relatively flat and only 7 dB below the nominal level. This suggests the design will have excellent power
response. Note how well the 22TFF holds up off axis in the top octave. This is excellent off axis dispersion.