Why is there an 180 degree out-of-phase switch on some subs?

[Antoneo]

I have been looking at some subs and noticed that usually the mid range - higher range subs have a switch that I guess outputs sound 180 degrees out-of-phase. Why would anybody want that? Wouldn't there be destructive interence depending on your setup (ie. you have floorstanders and you set them as "large" in the receiver menu)?

 

[LiQiCE]

My only guess would be incase you wired it backwards, you could fix it by just pressing a button? I'm not an audiophile so I really dont know why else you'd want your speakers out of phase.

 

[spanky]

at first, i thought u were talking about a sub.. as in the sandwich. then i thought u were talking about a sub.. as in a submarine from the navy. then i finally figured out u were talking about a sub.... as in subwoofer

 

[Squisher]

No, actually for every 12db/octave slope for your crossover network you invert the phase. A 24db/octave would put it back in phase.

This would only come into play if you were combining crossovered speakers with others of differing slopes or with no crossovers.

Because I have 12db/oct. passive crossovers on both sets of fronts in my Dakota I have to inverse the speaker leads to my back(stock) speakers.

 

[308nato]

My CerwinVega! sub manual says to set it to 180 degree out of phase if you place the sub x-distance from the main speakers. My sub is behind where I sit and the mains in front of me. There is 22 feet between them. This times the bass from the sub to reach your knoggin' at the same time as that from your mains if I understand the manual correctly. Personally, I can't tell the difference.