Shaded Arrays vs Unshaded Arrays
Here’s an APL_TDA plot of the frequency shaded arrays after a bit of cleaning up with EQ. The bottom end is cleaned up too, the phase is edited to follow minimum phase over it’s entire bandwidth:
Keep in mind that this plot includes all the balancing that is going on between the arrays and the sub-woofers to end up with this in-room result.
The Haas limit
My primary attention goes to the first ~20 ms after the pulse. After that period of time, our ears will largely be past the Haas limit for most frequencies. Our mind will process those sounds separately from the direct sound (making them sound more like an echo or reverberation). When comparing the same data from the unshaded array we see some differences. It becomes clear that the effect of the floor/ceiling reflection of the side-lobes was higher in level back when i was running the arrays unshaded (a more clear light blue peak at the 30 Hz line):
Looking more closely at these plots, we can see that the top end of the shaded arrays drops quite quickly after the main pulse. The unshaded array still keeps it lingering at a higher level before dropping down completely. I’ve seen that in another type of measurement too. Here’s the differences between the unshaded arrays and frequency shaded arrays when looking at their Energy Time Curve:
Animating the change going from unshaded array with the Vifa/Peerless TC9/FD18-08 (without subwoofer support in our room pré renovation) to the current shaded array using the Scan Speak 10F/8414G10 (with subwoofer support in our freshly renovated room):
A comparison between Februari 2016 and Februari 2024
Improving the vertical directivity
A lot of little things have changed in this period. Overall the speaker changes (going from unshaded arrays to frequency shaded arrays) have had the most effect on the vertical directivity. That does shows up as reduction of in-room energy in the top end of this graph (4K and up). See the influence of the driver change itself on this page.
Horizontal directivity has remained the same, the changes in our renovated room being responsible for the largest differences here.
The added sub-woofers did clean up the in-room result of the bass below ~200 Hz. The shared load at low frequencies further reduced the influence of room effects.