32Hz Ported Measurements ...
The first round of ported cabinet measurements are in and not what I expected. First here is the plot one more time for the legacy sealed (ie: classic Klipsch La Scala) cabinet. ...
Below are the results of the ported La SEOS cabinet. For this test the doghouse is closed on the bottom side and left open on it's top side. The upper cabinet (occupied by the crossover and upper range horn/ waveguide) has its' back closed off and two vents tuned to 32Hz. Those two vents measure 9.25 inch tall by 2 inches wide by 13 inches deep and extend along the sides of the cabinet (see the PICs in post #76)
At first you scratch your head and say, "By golly that looks just like the results for the legacy unported cabinet!", and you would be mostly right. However a closer examination shows a 3dB rise at 43Hz. Note the red circle in the PIC below. This is with 32Hz ports. I tried 40Hz ports as well. The difference was negligible.
The ports for the La SEOS are on the back of the cabinet and these measurements were taken one meter on axis in front. It could be argued that the benefits of the ports are simply not being measured because of that fact. So I slid the cabinet within 6 inches of a wall and moved the measurement mic to align with the edge of the cabinet and measured the results. When I did that the bump at 43Hz rose to 4dB, offering 1 more dB of gain.
That's a lot of work for a narrow 3 or 4dB bump at 43Hz. However studying the plot shows a couple more changes. The notch at 50Hz has been pulled up 3dB as well. But the most interesting change is not down low but up in the mid bass output of the short horn.
Note that the horn is now more controlled. The overall amplitude is flatter and that is something that I simply had not expected to happen. So the question that everybody wants to know the answer to is ..."Does the ported version sound any better than the unported version?"
The answer is a qualified, "Yes" but the difference won't set your knickers on fire. the change is subtle. The bass sounds marginally fuller and the midbass sounds less 'crashy' for lack of better words.
And finally, "Is it worth the effort to add the ports? "
Again I say, "Yes", not because the bass is extended but because the midbass cleans up. Perhaps that is the improvement that people are hearing when they add volume and ports to the Klipsch La Scala. Both the ported and unported versions need to be supplemented by a subwoofer.