Can someone explain Phase to me?

[gunz4me2 10+ year member]

I was wondering if someone could explain phase to me as it relates to car audio in layman's terms. Mainly, why can every speaker be wired in phase, but it some times takes wiring the subwoofer 180 degrees out of phase to avoid cancellation at or around 80 Hz? Then again, in other setups, wiring everything in phase works perfectly fine.

What gives? Does this have something to do with the positioning of the individual drivers relative to the position of the listener or is there more to it than that?

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[supermaxx123 10+ year member]

Yes, I've alson noticed that running one mid out of phase works too. I reversed my left mid and it seemed to help bring the bass to the left. I guess its just a trail and error type deal.

 

[gunz4me2 10+ year member]

A member on another forum was complaining that his bandpass setup was hardly producing any bass with the subwoofers facing each other with 4" of space in between them. I told him to wire one out of phase from the other, and he thanked me. Granted, that is easy to understand, just like if you wire a subwoofer inverted (ETA out of phase...).

But you are right, this is a whole trail and error thing. Sadly, in the past, I found myself giving up on a particular subwoofer setup rather than trying the different wiring options. In fact, changing amplifiers in my Mustang required a flip of the phase switch whereas the amplifier I was using prior to the swap was good to go in phase. Weird...

 

[audioarsonal 10+ year member]

A member on another forum was complaining that his bandpass setup was hardly producing any bass with the subwoofers facing each other with 4" of space in between them. I told him to wire one out of phase from the other, and he thanked me. Granted, that is easy to understand, just like if you wire a subwoofer inverted.
But you are right, this is a whole trail and error thing. Sadly, in the past, I found myself giving up on a particular subwoofer setup rather than trying the different wiring options. In fact, changing amplifiers in my Mustang required a flip of the phase switch whereas the amplifier I was using prior to the swap was good to go in phase. Weird...

What you described is called ISO BARIC.Basically taking 2 woofers and making them one.Used back in the day were space was limited and still used today.

 

[JimJ 5,000+ posts]

In fact, changing amplifiers in my Mustang required a flip of the phase switch whereas the amplifier I was using prior to the swap was good to go in phase. Weird...

Inverting/non-inverting amplifiers.

I've run into that with preamps, some will invert the phase, others won't...hopefully they'll tell you, otherwise it's a couple minutes of scratching your head until you realize why it sounds like *** //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Immacomputer 10+ year member]

Phase directly relates to at what amplitude the waveform is at at any given point in time relative to another driver or reference point and at a given frequency(like speaker A vs speaker B or from when time=0 ). The phase relationship between drivers is going to change over the frequency range and is most critical near the crossover point. Phase is determined by the travel distance from the speakers to your ear, your crossover network, and your enclosure. Different crossover points and slopes cause different phase relationships between drivers. The enclosure and crossover network are the primary driving points of why it sometimes sounds better to invert the phase and not really the distance although the distance changes phase slightly (not as much at low frequencies as it does at higher frequencies).

The reason some amps need to have their phase switched is based on the types of crossovers and their slopes. As you increase the order of the filter (6dB, 12dB, 18dB, 24dB), you change the phase by 90 degrees at the crossover frequency. A butterworth 6dB slope crossover will have a phase shift of 90 degrees at the crossover frequency (Fc). With a 12dB slope, the phase shift will be 180 degrees at Fc. If your mids are crossed over at a different frequency than your sub or if the filter is different, then the phase relationship between the two drivers is going to be off and flipping the sub 180 degrees out of phase could bring that difference down, it could make it worse, or it could change nothing (given a 90* phase shift to begin with as flipping it 180 degrees will still leave your drivers 90* out of phase at the crossover point).

Given an ideal situation where you have two drivers crossed over at the same frequency with the same filters (type and slope), both playing infinite baffle, and having relatively short distance difference between them to your ear, you should get poor results flipping the phase as the two drivers will be very close to in phase with each other at the crossover frequency. If the filters or crossover points are different, then your relative phase at Fc is going to be different and flipping the phase may help.

Also note that the enclosure is going to have a very large impact of the phase response of your subwoofer. Enclosures are filters and an enclosure not properly designed for the specific driver could have a wild and crazy phase response at the crossover frequency. Also note that the higher order enclosure you have, the more rapidly the phase will change.

I hope that clears things up.

 

[perfecxionX 10+ year member]

Phase directly relates to at what amplitude the waveform is at at any given point in time relative to another driver or reference point and at a given frequency(like speaker A vs speaker B or from when time=0 ). The phase relationship between drivers is going to change over the frequency range and is most critical near the crossover point. Phase is determined by the travel distance from the speakers to your ear, your crossover network, and your enclosure. Different crossover points and slopes cause different phase relationships between drivers. The enclosure and crossover network are the primary driving points of why it sometimes sounds better to invert the phase and not really the distance although the distance changes phase slightly (not as much at low frequencies as it does at higher frequencies).
The reason some amps need to have their phase switched is based on the types of crossovers and their slopes. As you increase the order of the filter (6dB, 12dB, 18dB, 24dB), you change the phase by 90 degrees at the crossover frequency. A butterworth 6dB slope crossover will have a phase shift of 90 degrees at the crossover frequency (Fc). With a 12dB slope, the phase shift will be 180 degrees at Fc. If your mids are crossed over at a different frequency than your sub or if the filter is different, then the phase relationship between the two drivers is going to be off and flipping the sub 180 degrees out of phase could bring that difference down, it could make it worse, or it could change nothing (given a 90* phase shift to begin with as flipping it 180 degrees will still leave your drivers 90* out of phase at the crossover point).

Given an ideal situation where you have two drivers crossed over at the same frequency with the same filters (type and slope), both playing infinite baffle, and having relatively short distance difference between them to your ear, you should get poor results flipping the phase as the two drivers will be very close to in phase with each other at the crossover frequency. If the filters or crossover points are different, then your relative phase at Fc is going to be different and flipping the phase may help.

Also note that the enclosure is going to have a very large impact of the phase response of your subwoofer. Enclosures are filters and an enclosure not properly designed for the specific driver could have a wild and crazy phase response at the crossover frequency. Also note that the higher order enclosure you have, the more rapidly the phase will change.

I hope that clears things up.

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[gunz4me2 10+ year member]

Thanks for the explanation. Now I know why one of my friends swears by his own 6db/octave crossovers that he makes himself. For years I have been following the "if it doesn't sound right, try reversing polarity" philosophy but it wasn't until last night when I wanted to know the "why".