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what is phase shift?


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digdug18 
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Posted: August 21, 2007 at 4:12 PM / IP Logged  

What is phase shift, and how how it make my car audio sound better?

DYohn 
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Joined: April 22, 2003
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Posted: August 21, 2007 at 10:39 PM / IP Logged  
Phase shift means many things.  In what context do you mean?
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dboomer 
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Posted: August 22, 2007 at 12:40 PM / IP Logged  
When speakers are out of phase it means that when one is moving out, the other is moving in. They cancel each other out. When you have 2 sets of subs or 1 set of subs and 1 set of mids you must make sure they are moving in and out together. Some electronic crossovers have the feature to change the sub phase.
haemphyst 
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Posted: August 22, 2007 at 1:48 PM / IP Logged  
dboomer wrote:
When speakers are out of phase it means that when one is moving out, the other is moving in. They cancel each other out. When you have 2 sets of subs or 1 set of subs and 1 set of mids you must make sure they are moving in and out together. Some electronic crossovers have the feature to change the sub phase.
That is a FANTASTICALLY DRASTIC oversimplification, and that is not remotely complete. DYohn is far more correct in trying to get more information... You are simply describing an in-phase/out-of-phase (or 0° or 180°) situation - not "phase shift". There is SO much more to it than that. And while in-phase/out-of-phase is TECHNICALLY phase shift, that's not all there is to it.
Phase shift can be anywhere from 1 degree to 360 degrees out, or shifted, (with 180 degrees being a complete cancellation) but in a complex signal, like audio, with a device such as a loudspeaker - a device with a finite response time, not all frequencies will have the same phase shift. Ideally you would adjust your phase angle ONLY at the crossover point, so the drivers are properly phased AT THAT FREQUENCY. This is not easy to prevent or fix, involving very expensive components, (my UCSPros were 800 dollars each) and very time-consuming tuning (my tuning took about 2 weeks to make me happy with it) of the system. I know, as I have done it in my own car.
See here:
what is phase shift? -- posted image.
Fixing phase shift involves time delay. This makes the diaphragms in the system (again, at the crossover frequency) make the same frequency at exactly the same time, removing the phase shift at the "center frequency", and minimizing the destructive interference (damage) both above and below that "center frequency".
When the phase shift is removed or minimized, this is how you acheive a "perfect" frequency response. The sound power of the system becomes as flat as possible, preventing holes or peaks in the overall response of the system, and I think this is the answer to the OPs "better" question. REMOVING shift (i.e. delay) by ADDING delay (i.e. shift)... It doesn't seem right or sound logical, but that's exactly what is happening.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
dboomer 
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Posted: August 23, 2007 at 10:09 AM / IP Logged  

haemphyst wrote:
dboomer wrote:
When speakers are out of phase it means that when one is moving out, the other is moving in. They cancel each other out. When you have 2 sets of subs or 1 set of subs and 1 set of mids you must make sure they are moving in and out together. Some electronic crossovers have the feature to change the sub phase.
That is a FANTASTICALLY DRASTIC oversimplification, and that is not remotely complete. DYohn is far more correct in trying to get more information... You are simply describing an in-phase/out-of-phase (or 0° or 180°) situation - not "phase shift". There is SO much more to it than that. And while in-phase/out-of-phase is TECHNICALLY phase shift, that's not all there is to it.

WOW...did I strike a nerve???

sarcomax 
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Posted: August 23, 2007 at 12:07 PM / IP Logged  
Probably not. Haemphyst is just extremely thorough about everything, and has been doing this stuff longer than most of the "rookies" have been able to eat without help from mommy's teet. If you would have quoted the rest of his post you would have seen that. We still don't know what the OP has going on, so until then we will not know if Haemphyst's typhoon of knowledge or your spring shower (not meant as an insult to your very valid information, just as a comparison of words to rain...) helped the OP more.
dboomer 
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Posted: August 23, 2007 at 1:10 PM / IP Logged  
Haemphyst's post was very informative and accurate. The referrence to my post was childish. Why not add knowledge without bashing others input. I joined this forum to help and get helped...not compete to see who knows more.
sarcomax 
Copper - Posts: 276
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Posted: August 23, 2007 at 3:15 PM / IP Logged  
Society in general is WAY too uptight. If you are offended by something said by someone that you don't know, that doesn't know you, and that you will probably never meet, then there are much bigger issues at hand. You offered information. You helped. You even helped first. Your information might have helped so much the the OP read it and it solved all of his problems. He may never need to reference this site again. Everybody that is registered here is looking to share information. I for one read every post, offer up what I can when I can, and have had my ideas shot down, ignored, and ridiculed. I have had entire posts deleted. (Come to think of it, this one probably won't see much daylight...)Somebody came along and offered more information, and referenced that your info was not complete. BIG DEAL. If that was the first time that your ego has been challenged, let me welcome you to the first day of kindergarden, because believe me, it will get worse. So what if Haemphyst is childish...I hear his system sounds awesome.
steezs 
Copper - Posts: 172
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Posted: August 23, 2007 at 5:15 PM / IP Logged  
Are you guys talking about phase shift on amplifier subs? If so i was reading the manual of a hifonics amp and it said basically to put it quick and simple if your subs are in the trunk , behind you or  farthest speaker from you leave the setting at zero. If the subs are in the door panels or closer to you than the other speakers you can adjust it to your liking with or without expensive equipment.
the duce
DYohn 
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Moderator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
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Posted: August 23, 2007 at 7:36 PM / IP Logged  
dboomer, stick around for a while and you will learn about all of our quirky personalities.
 
haemphyst is, as usual, 100% correct, your example is a dramatic over-simplification of a very complex topic.  Speaker phase is part of a science called psychoacoustics...
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