|The FaitalPRO STH100 aluminum horn throat is an elliptical, tractrix design. It has a coverage angle of 80° x 70° and best of all, measures only 7″ wide and 4.7″ high. With these dimensions, 8″ and 10″ woofers would be just about the right size.
For convenience, I’m using a 7″ Dayton RS180S to accompany the STH100. Bolted to the back is a Selenium D220Ti compression driver.
Fig 1 shows the RS180S and the STH100/D220Ti crossed at 1.5kHz (24dB/oct).
The STH100 is remarkably flat all the way to 10kHz. Beyond that, it rolls off linearly to 20kHz (-10dB).
The Red trace is the summed response of the RS180S and the STH100/D220Ti. Interestingly, there are no cancellations on either side of the crossover.
|Actual Acoustic Crossover Frequency
The Red trace in Fig 2 is with the D220Ti wired in reversed polarity.
The tip of the notch is quite close to the point where the RS180S and the D220Ti cross. This indicates that there’s minimal offset in their acoustic centers.
|Time Aligning the drivers
With the D220Ti still wired in reversed polarity, a delay is added to the RS180S.
The Violet trace in Fig 3 is when the two drivers are aligned.
|Time Aligned Summing
In Fig 4, the Violet trace is of the D220Ti re-wired back to normal polarity.
|Drivers Physical Alignment
Comparing Fig 1 and 4, we can see there’s not much difference in the summing. That’s due to the acoustic centers of the D220Ti and the RS180S being almost in line. Because of the close proximity, there are no cancellations on either side of the crossover frequency.
This combination is ideal for a passive crossover. If one truly wants perfect time alignment, it can easily be accomplished by shimming one of the drivers, probably the STH100.
All measurements were made with the microphone at 1 meter, on tweeter axis. Gating is at 5 msec and No Smoothing applied.
November 4, 2016PRO DRIVERS