Critical subwoofer tip

I have a question for people who have phase controls for their subs. How do these work?

see ieLogical SubterraneanHomesickBlues

Most Phase controls are All Pass filters. They don't affect all frequencies equally. see http://www.ielogical.com/assets/SubTerrBlues/PhaseControl.png

To properly integrate a 'generic' sub controls for Level, Phase, Polarity, Crossover Hz & Order are required. Delay is icing on the cake. Bespoke subs mating to a specific set of mains may get by with fewer controls.

MC's response is nonsense. But I repeat myself.

I found a better result in my system by playing a repetitive kick drum and trying to match the beat sharper than softer.

It depends on how the kick drum was eq'd. For some music, there is no low end at all and other's next to no point. Additionally, we often flipped the foot phase on pop recordings.

My favorite piece by ear is a pipe band recorded out of doors. When the phase is correct, focus dials in just like a camera.

Not unless the slope of the cutoffs for both are the same.

Not true. One can achieve near perfect integration with a main 1st and 3rd order sub with polarity inverted.

Slopes must be adjustable. Ideally on both the main and the sub. They do not have to match.

Subwoofer phase adjustments are simply (very small) timing delays applied to ONE of two speakers attempting to producing the SAME frequencies.

Not unless phase adjustment is done with a delay or by physically moving the speaker.

Lastly, one cannot "invert the phase." This makes no sense. Adjusting the phase 90 degrees, 180 or 270 of a subwoofer is adding a small delay in the timing of the sound wave. There is no way to do the opposite and speed the sound wave up, hence no such thing as, "inverted phase."

A typical phase control does not add delay. It shifts the phase relationship in the speaker range. If one inverts polarity, the phase shifts. The timing remains the same.

Delay is to achieve the same impulse arrival time at the listening position. 10ms is about 11.25 feet. Delays around 1ms are more common.

An All-Pass Phase control does not affect all frequencies equally. It is used to get the best integration between the non-linear sub and main phase responses. see  PhaseControl.png (868×506) (ielogical.com) for an example

Any recording with a prominent Kick drum will reveal proper polarity.

The kick is a poor arbiter. One might have a preference, but unless one knows the material first hand, it's just a preference.

Since polarity can change from track to track on some more highly produced recordings made at different locations it would be most useful if every modern preamp was equipped with a remote control polarity switch since its more discernible at the listening position

Polarity can vary from instrument to instrument in one track!

Back in the day, the east coast & Europe was mostly pin 2 +ve, while the left coast was pin 3. Some studios varied in both locations. Microphones could be either depending on their history.

Pop overdubs were often done all over town. Sometimes on both coasts or overseas. Not all engineers checked polarity. Hence the drums could be +phase, lead vocals -, percussion +, backgrounds ?, etc.

Some more twisted engineer types carried their own mics, pre's, EQ, amps, speakers & cables. 0:) That way you could get the room without worrying about polarity.

Enter MC's room  Raummoden Rechner - Trikustik to view nodes.

View MC's system Millercarbon's System - Virtual Systems (audiogon.com)

A combination of ported and unported subs with 20Hz capable mains are going to produce impressive, but never accurate low end.

Tekton MOAB have 17 distinct arrival time per channel. With 8 widely spaced LF [main woofers to 300Hz 1st order, down only 6db @ 600Hz] drivers [4 main and 4 sub] there will be lots of indistinct bottom.

MC once advised: " Here in Washington we have some sweet green bud that will get you there in one step: inhale."  in The 5 stages of making a bad audio purchase

I like my music as I heard it in the studio and the control room: Neat.

That is achieved by time and phase alignment of the sub, LF, mid and HF drivers. Full Stop.

Consider a kick drum on an open field where there are no reflections. The higher frequencies of the beater hitting the head arrive before the full amplitude of the head deflection, yet you still identify it as a kick.
 You can see a kick waveform here
http://192.168.1.160/assets/CblSnkOil/Signal_vs_ACLine.png

Putting the same kick drum in a room does not change your identification as a kick, but you are fully aware it is now a kick in a room

In a multi driver speaker the frequencies which make up a kick are reproduced by different drivers. The sound begins when the electrical signal starts and in the voice coil plane. The ≈50Hz fundamental starts propagating from the woofer at the same time as the [say] ≈2250Hz beater whack does from the mid. If the voice coil of the woofer is 3 inches back from the mid, the whack is ≈180° out of phase by the time the fundamental starts to reach your ear.

Time aligning attempts to minimize these displacement artifacts. Nothing is ever perfect and there are crossover affects to consider as well, but properly aligned systems have a coherence missing in others. Our brain can correct for frequency variation but cannot shift time. 

Compared to live acoustic sound, all playback sucks. But as Nietzsche opined "Without music, life would be a mistake." So we put up with it.