What is the Phase Switch for behind my Sub? - AVS Forum
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post #1 of 13 Old 01-05-2008, 12:45 PM - Thread Starter
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Sorry for the dumb question guys, but what is it? I have the JBL Sub10 subwoofer and it has a Phase switch in the back and has it at 0 degrees on one side, and 180 degrees on the other. Whats does that mean? Does it change the way the bass sounds? I will try it when I get home Monday but I'm hoping I can just get a quick answer. Thanks for your help.
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post #2 of 13 Old 01-05-2008, 01:12 PM
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You want all your speakers moving in the same direction. If you have your speaker wires backwards (out of phase), you can flip the switch instead of putting your wires the correct way.
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post #3 of 13 Old 01-05-2008, 01:31 PM - Thread Starter
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Quote:
Originally Posted by TX_Tech View Post

You want all your speakers moving in the same direction. If you have your speaker wires backwards (out of phase), you can flip the switch instead of putting your wires the correct way.

Hmm, thanks for the response but not sure I quite understand. Who would put in the speaker wires backwards? So it does not change the sound of the bass then right?
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post #4 of 13 Old 01-05-2008, 02:33 PM
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Quote:
Originally Posted by Nics1246 View Post

Hmm, thanks for the response but not sure I quite understand. Who would put in the speaker wires backwards? So it does not change the sound of the bass then right?

If one of your front speakers was wired backwards relative to the other, they would be 'out of phase' with one another. Very basically, what this causes is that when one speaker's woofer is 'vibrating' forward, the other is 'vibrating' backwards. The result is that the woofers' output 'cancels' one another and results in reduced perceived output (which in the case of woofers, is bass).

In much that same way, the subwoofer can be 'out of phase' with the front speakers. And the result is the same; reduced bass. Since your sub is most likely wired with an RCA cord, flipping or reversing the wires is not possible without rebuilding the cable. So, your sub has a switch which will do the exact same thing. Without getting too technical about it, what you want to use is the setting that provides the most bass output, all other settings aside, at your 'sweet spot' (where you normally or most often sit). So, put on some music that you are familiar with that has a steady bass beat, set the volume at an average level, sit in your 'sweet spot', and have someone switch your phase switch back and forth for you. You may want to try this with a few CDs. If you can't tell a difference, then use either setting. Otherwise, use the setting that provides the most bass output. But be careful. If your subwoofer's output is set too high, you may find the setting that's out ot phase to sound "better" to your ears. Still, what you want is the setting that provides the most bass output. So find that setting, THEN readjust the sub's output to your liking.

If you have an SPL meter and you want to get more technical about setting the subwoofer's phase properly, what you want to do is figure out which setting provides the most output at your receiver's crossover setting. So, if your receiver's crossover is set to 80Hz, what you first need is a pure 80Hz tone on a CD (or DVD). Place the meter at your 'sweet spot' or where you normally place it when you calibrate your system with the meter. Playback the tone that corresponds to your receiver's crossover setting. The tone will be played back by both the subwoofer and your front speakers. Measure the tone's output level with both your phase settings (0° or 180°). The setting that produces the most output is the correct setting.

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post #5 of 13 Old 01-05-2008, 03:03 PM
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Quote:
Originally Posted by sivadselim View Post

If you have an SPL meter and you want to get more technical about setting the subwoofer's phase properly, what you want to do is figure out which setting provides the most output at your receiver's crossover setting. So, if your receiver's crossover is set to 80Hz, what you first need is a pure 80Hz tone on a CD (or DVD). Place the meter at your 'sweet spot' or where you normally place it when you calibrate your system with the meter. Playback the tone that corresponds to your receiver's crossover setting. The tone will be played back by both the subwoofer and your front speakers. Measure the tone's output level with both your phase settings (0° or 180°). The setting that produces the most output is the correct setting.

Suppose that 0° gives the most output at the crossover. Is it possible that 180° will give a flatter overall response? If so, then which setting is preferable?
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post #6 of 13 Old 01-05-2008, 03:50 PM
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Originally Posted by tkc View Post

Suppose that 0° gives the most output at the crossover. Is it possible that 180° will give a flatter overall response? If so, then which setting is preferable?

Well, you're getting a bit more advanced. If the sub is 'in phase', the perceived output will be greater at the receiver's set crossover point. But, yes, the opposite setting could produce a flatter overall room response. But this is not be directly related to the sub's phase, per se, but is related to the sub's interactions with the room. Which phase setting, 0° or 180°, should be considered "correct" in this case is arguable, I suppose. I would prefer to say that setting the sub to be 'out of phase' produced the flattest room response.

Perhaps we should recommend to the OP that he set the phase to the setting that he prefers, understanding full-well that he may prefer the sound of a flat response or that he may prefer the sound of a bass-boosted response. He (nor we) will never know which setting is more "correct" and all that will matter is that he is happy. However, instead of responding that way (which MAY have, actually, been best) I was trying to give him an understanding of what 'phase' is through his reading of my response.
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post #7 of 13 Old 01-05-2008, 03:52 PM
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I'll take a crack at explaining this in simple terms

Your speakers move in and out. When a sound starts to come out of the speaker, it moves in first or out first. So the phase switch determines whether it moves in first or out first. This affects the "phase" of the sound wave. You want to set the phase so that the sounds coming out of your sub don't cancel out the sound coming out of your other speakers. So you want to set the switch so that the bass sounds stronger. Get a friend to flip the switch and you listen where you normally sit, and see which switch position (0 or 180) sounds better. It's pretty hard to hear but one switch setting is often better than the other position of the switch. Usually you can see the difference if you have measuring equipment.

Strictly speaking, a switch that has two settings (0 OR 180) is a polarity switch, whereas a knob (0 all the way to 180) is variable phase setting. With a polarity switch, you can get the same effect by switching the + and - wires.

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post #8 of 13 Old 01-05-2008, 03:55 PM
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Quote:
Originally Posted by warpdrive View Post

I'll take a crack at explaining this in simple terms.

Was my explanation too complicated?

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post #9 of 13 Old 01-05-2008, 06:10 PM - Thread Starter
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Thanks for your responses everyone. I will have my wife switch between the 0 and 180 settings for me when I get a chance. Again, thanks for all of the explanations, I think I get it now.
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post #10 of 13 Old 01-05-2008, 08:33 PM
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Quote:
Originally Posted by sivadselim View Post

Was my explanation too complicated?

no, don't take it that way. I just thought that I could try to clarify the issue in case it was still confusing to the OP

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post #11 of 13 Old 01-06-2008, 10:44 AM
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Quote:
Originally Posted by sivadselim View Post

Was my explanation too complicated?

Yes. IMO if you are asking about phase for a sub. Now if you were on your 3rd sub no it's easy to understand.
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post #12 of 13 Old 01-07-2008, 04:26 PM
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post #13 of 13 Old 01-07-2008, 04:37 PM
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So how do you like the Sub 10 and what speakers are you using with it?
Thanks,
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