Phase degree adjust - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 17 Old 02-14-2020, 06:12 AM - Thread Starter
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Phase degree adjust

I heard if your sub isn't horizontally in line with the front speakers and kept forward, more closer to your LP than the fronts, there is some phase degree adjust needed higher than 0 degrees (which is the factory default position of the phase knob). The phase knob on my sub can be dialed from 0-270 degrees. Is there a way to correctly ascertain what phase adjustment in degrees do i need or do i do this by trial and error listening to bass heavy songs and see with which setting bass blends better?
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post #2 of 17 Old 02-14-2020, 06:40 AM
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Phase is more or less a delay so if you use an AVR with auto setup that does distances the AVR should sort it out.


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post #3 of 17 Old 02-14-2020, 07:34 AM - Thread Starter
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The phase degree adjust is effectively adding a time delay. But i have read articles that say it requires adjusting even if you have set the distances on your AV processor through a distance measurer or the AV processor's automated process, if the sub is quite ahead of the fronts. And im not talking polarity (which is different and is just a 0 or 180 degree switch.)

This article in one of its segments talks about adjusting phase through a filtered pink noise test but im not quite following it

http://www.audiodrom.net/en/as-we-se...up-a-subwoofer

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The sub should always be on a line with or slightly in front of the satellite. With the woofer a moderate amount in front of the satellites, the phase will generally need to be set something greater than 0 degrees. Return the sub(s) to the correct polarity. Play the same frequency of filtered noise and increase the amount of "phase" until you hear the dominant pitch rise. Back it off slightly, recheck your setting, and that's it.
can anyone explain this?

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post #4 of 17 Old 02-14-2020, 08:02 AM
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The slightly forward is because big woofers are deeper and so the sound “originates” further back compared to shallower midrange or tweeters. This is the main reason for some speakers “leaning back” a bit.
This can be compensated for by accurate timing delays. Auto setups are usually very good at this because they measure time not physical distance.(but the measurements must be done correctly, and not saying they are always right or sound the best to everyones liking, but overall)


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post #5 of 17 Old 02-14-2020, 08:10 AM - Thread Starter
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I use a laser distance measurer, when you input distances yourself on an AV processor read from the laser measurer, the AV processor internally calculates the time delay on the basis of it. But im not convinced that's the only adjustment needed, but the phase too, the sub would be 1.5-2 ft. in front of the speakers, the above article mentions a way to calculate the phase degree but im not getting the method and need an explanation.
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post #6 of 17 Old 02-14-2020, 08:20 AM
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Quote:
Originally Posted by Rysa_105 View Post
I use a laser distance measurer, when you input distances yourself on an AV processor read from the laser measurer, the AV processor internally calculates the time delay on the basis of it. But im not convinced that's the only adjustment needed, but the phase too, the sub would be 1.5-2 ft. in front of the speakers, the above article mentions a way to calculate the phase degree but im not getting the method and need an explanation.


Didnt read the article so cant help you with an explanation on that. Check if your sub has some delay from DSP because a lot of newer subs do and a physical distance measurement will be wrong.
Which AV processor and sub do you have?
Its very difficult to do a better distance measurement than the auto setup because its not really the front plate of a speaker you should measure to, its from where the sound wave starts.(if you want/need to be absolutly precise and you probably dont really need that degree of accuracy)


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post #7 of 17 Old 02-14-2020, 08:29 AM - Thread Starter
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i measure using laser measurer at ear pointing the laser to the center of the tweeter of the speakers (woofer in case of sub). the sub will be a couple of feet ahead of speakers, my question is about phase, so if i only ran the auto process according to you the phase knob doesnt need to be touched? well not according to some articles like the one above, or according to the sub's manual..sub is a JL E112.
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post #8 of 17 Old 02-14-2020, 08:40 AM
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Phase degree adjust

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Originally Posted by Rysa_105 View Post
i measure using laser measurer at ear pointing the laser to the center of the tweeter of the speakers (woofer in case of sub). the sub will be a couple of feet ahead of speakers, my question is about phase, so if i only ran the auto process according to you the phase knob doesnt need to be touched? well not according to some articles like the one above, or according to the sub's manual..sub is a JL E112.


I dont know for sure so maybe someone who does will answer.
I do know there are some phase tweaks some use after auto setup, but not sure if those are for accuracy or preference.

Are you unhappy with the sound after auto setup, havent tried it or just want to see if you can get it even more optimized?

Remember that a sub cant always be placed where its convenient or fits with distance to other speakers to get the best and most even bass. (Its great when it does though)
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post #9 of 17 Old 02-14-2020, 10:26 AM
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Quote:
Originally Posted by Rysa_105 View Post
i measure using laser measurer at ear pointing the laser to the center of the tweeter of the speakers (woofer in case of sub). the sub will be a couple of feet ahead of speakers, my question is about phase, so if i only ran the auto process according to you the phase knob doesnt need to be touched? well not according to some articles like the one above, or according to the sub's manual..sub is a JL E112.
What AVR or AVP are you using?

Using a laser pointer and setting the distance setting to the actual physical distance of the subwoofer is flawed methodology. Most subwoofers have DSP built into their amplifiers, this DSP introduces delay into the signal path. This is why when you run the auto-setup on your AVR/AVP the subwoofer distance is usually set a few feet further than the physical distance...it is accounting for that delay in the sub amp.

If you only have a single sub, and you have an AVR/AVP that will correctly set the distance setting for the sub, it does not matter where you set the phase control before calibration as the AVR/AVP will account for it in the distance setting. There is no need to touch the phase control post-calibration.

However, adjusting the distance setting post-calibration is encouraged because most AVRs/AVPs do not have the ability to measure both subs and mains together, so they do not get these two "in-phase". When the subs and mains are not in-phase it will result in a dip around the crossover. This procedure is known as the Sub Distance Tweak and I have outlined a simple method below on how to go about it.

Hope this helps!


_______________________________________________


If you don't have measuring equipment, the distance tweak can be done with an SPL meter (or SPL app on a smartphone) and test tones downloadable from the internet, available on YouTube, from a test disc or with REW (free download). The reason to invert phase in step 3 is because it is sometimes easier to measure the dip than it is the peak when using an SPL meter.

  • For the Center Channel, set your AVR to the Dolby PLII surround mode (Dolby Surround on Atmos AVRs), you should be getting output from the CC + sub(s) only
  • For the FL/FR channels, set your AVR to the Stereo surround mode, you should be getting output from the FL/FR + sub(s) only
  • Invert phase on your subwoofer(s)
  • Play a sine wave that corresponds to your crossover frequency (e.g. 80hz) and measure the output with the SPL meter about a foot in front of your face at the MLP
  • Gradually increase the sub distance setting in the AVR in 1' increments (both subs equally if you have independent control) (on some AVRs you must make sure to back out of the distance setting menu before the new setting will take effect)
  • The sub distance setting that gives you the lowest SPL reading is the setting you want (you can tweak further in smaller increments if you want to, but I have found that 1' increments is usually sufficient)
  • Invert the phase on your sub again and you are done
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post #10 of 17 Old 02-14-2020, 11:41 AM - Thread Starter
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I dont use the automated process on my pre pro , i have a laser measurer and spl meter and enter distance settings and trim manually. I know with powered subs, it's not the exact distance to the woofer but a little higher to be entered to account for the dsp/amp of the subwoofer. But again, my question about how much phase degree adjust i need is not answered. I dont know what the guy above means by invert the phase, are are you talking polarity? phase adjust is a knob that can be dialed from 0 to 270 degrees on the sub, polarity is a switch that can be 0 or 180 degrees, phase and polarity are not the same.
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post #11 of 17 Old 02-14-2020, 11:55 AM
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Quote:
Originally Posted by Rysa_105 View Post
I dont use the automated process on my pre pro , i have a laser measurer and spl meter and enter distance settings and trim manually. I know with powered subs, it's not the exact distance to the woofer but a little higher to be entered to account for the dsp/amp of the subwoofer. But again, my question about how much phase degree adjust i need is not answered. I dont know what the guy above means by invert the phase, are are you talking polarity? phase adjust is a knob that can be dialed from 0 to 270 degrees on the sub, polarity is a switch that can be 0 or 180 degrees, phase and polarity are not the same.


For setting up as described by @Alan P setting the phase to 180 degrees should amount to the same thing as polarity 180.
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post #12 of 17 Old 02-14-2020, 12:05 PM - Thread Starter
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A bit confusing as to what he said, but i guess by 'invert the phase' he meant polarity. Some subs such as mine clearly differentiate phase and polarity and have different setting knobs for it.
My sub manual says
...The “Polarity” switch allows the user to select between normal (0 deg) and
reversed (180 deg) signal polarity. The “Polarity” switch will primarily affect the
small frequency range around the crossover point between your subwoofer and
satellite speakers.
Unlike the “phase (deg.)” control, which effectively adds time delay, the
“Polarity” switch produces an instantaneous reversal of the signal’s amplitude
peaks......
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post #13 of 17 Old 02-14-2020, 12:06 PM
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Quote:
Originally Posted by Rysa_105 View Post
I dont use the automated process on my pre pro , i have a laser measurer and spl meter and enter distance settings and trim manually. I know with powered subs, it's not the exact distance to the woofer but a little higher to be entered to account for the dsp/amp of the subwoofer.
So, how are you correcting for the delay induced by the sub amp? Guessing?? You would be much better served by running the auto-setup on your AVP to get the proper sub distance (and acoustic speaker distances) along with proper trim levels. Most auto-setup routines will get the distances and trims spot-on for you. Feel free to turn off the room correction afterwards.


Quote:
But again, my question about how much phase degree adjust i need is not answered.
I will quote from my previous reply: "If you only have a single sub, and you have an AVR/AVP that will correctly set the distance setting for the sub, it does not matter where you set the phase control before calibration as the AVR/AVP will account for it in the distance setting. There is no need to touch the phase control post-calibration."


Quote:
I dont know what the guy above means by invert the phase, are are you talking polarity? phase adjust is a knob that can be dialed from 0 to 270 degrees on the sub, polarity is a switch that can be 0 or 180 degrees, phase and polarity are not the same.
Those directions are fairly generic. Most subs do NOT have a polarity switch, so inverting the phase (180 degrees) was the simplest way to explain it. In your case, yes, flipping the polarity switch would accomplish the same thing.
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post #14 of 17 Old 02-14-2020, 12:21 PM - Thread Starter
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Most JL Audio subs have polarity switch and phase degree knob as separate controls. My previous sunfire also had them separate, so dont know where you come up with 'most subs dont have a polarity switch'. Some people casually label polarity as phase when what they mean is the former (the terms dont mean the same). But i get what you implied by 'invert the phase', that is effectively the same as the polarity switch being flipped to 180 degrees when taking SPL measurements and then back to 0 degree after done taking the measurements.
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post #15 of 17 Old 02-14-2020, 12:30 PM
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Adjustable phase is not the same as polarity, however changing the phase by 180 degrees is exactly the same as flipping polarity. Both will shift all frequencies 180 degrees.
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post #16 of 17 Old 02-14-2020, 01:10 PM
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Why don't you measure the response and dial in the settings to have smoothest transition at the crossover.

Building the room, speakers, and subs.
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post #17 of 17 Old 02-15-2020, 03:18 PM
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Have a look at Nyall Mellors (Acoustic Frontiers) "Hometheatre Calibration 101 levels, distance, phase" blog, explains things. He is a well known acoustican. He talks about phase, polarity to clarify.
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