You guys saying that the polarity/phase controls affect the SPL or the cone movement of the subwoofer are clearly misunderstanding the polarity/phase control, and what affects cone movement of the subwoofer driver.The *only* thing that affects how much cone movement the subwoofer driver goes through, and the concomitant amount of SPL it produces, is the amount of amplifier power applied to it. More amplifier power -> more cone movement -> more SPL. Simple as that.
The polarity control is *only* a positive/negative phase reversal switch. IOW, inverting the polarity switch starts the wave with a negative deflection, (inward movement) of the driver, instead of with a positive deflection, (outward movement), of the driver. This has *no* impact on how far the driver moves, either forward or backward.
A variable phase control *only* changes the point in time that the subwoofer moves. IOW, it adds a slight delay to the subwoofer's firing. If it is set to "0", the sub fires immediately when it receives the signal. If it is set to a positive number, the sub fires slightly later in time, all the way up to 180 degrees were it is firing with the exact opposite polarity, (the positive side of the wave is now the negative side of the wave). (IOW, setting a variable phase control from "0" to "180" is exactly the same as flipping the polarity switch.) Neither the polarity control or a variable phase control have any impact on how far the cone moves, or on the SPL output of the subwoofer driver.
However, if you're playing the sub along with your speakers, the *combined* SPL of the speakers and the subwoofer can be higher. That is because, if you time the subwoofer wave to be "in-phase" with the speaker wave at and near the crossover point, you will get constructive reinforcement, and a concomitant increase in SPL. However, this is *NOT* because the SPL of the subwoofer is higher.
Earlier in the thread, someone said that having the sub and speakers in-phase means having them firing at the same time. This is not quite correct. You want them firing so that they combine
at the same point in the wave. For example, if the sub is 14 ft. from the listening position, and the speakers are 9 ft. from the LP, you want the sub to fire slightly *before* the speakers, so it's positive wave arrives at the speakers just as they fire their positive wave. Then, they'll combine and be "in-phase" as they go forward from there. OTOH, in this same situation, with the sub further away than the speakers, if the sub fires at the same time
as the speakers, it's wave will be "behind" the speaker's wave and you'll get less constructive reinforcement. At some point you'll actually get destructive interference, and the subwoofer wave will cancel the speaker wave. Then, you'll have *less* SPL from the combined output of the two drivers.
The only frequencies the sub and the speakers share
are the frequencies around the crossover point. So those frequencies are the only ones you care about when setting the phase control.
To the guy "measuring" his phase with his fingertips... I don't even know what to say to that. Do you listen to your system with your fingertips? I don't know, maybe you stick your fingers in your ears when you listen?
I'm sorry, but that is just plain silly! You "measure" your subwoofer's output with an SPL meter, (or better yet an RTA or spectrum analyzer. Personally, I use this:http://www.xtz.se/index.php?&eng=true
It results in this:
Note not only the flatness of the overall curve, but the flatness around the crossover point, 80 Hz. (Above that, you are primarily seeing the speakers' interaction with the room.)