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Subs with reversed polarity (surprise!)
Subs with reversed polarity (surprise!)
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Old 15th June 2019, 08:46 PM   #31
CharlieLaub is offline CharlieLaub  United States
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For those who are following this thread, I would like to point out that Ben used two very different "subs" in each corner. See POST #1 for details.

If this was repeated with two identical my guess is that the results might not be the same...

The key is the phase response of the subs, which can be quite different for various types of enclosure (sealed box, vented, TL, etc) and they can have very different group delay (which is the same thing as phase rotation).

So, what the phase differences are, who knows? But this is likely not really two sources "in phase" and "180deg out of phase". At least I strongly suspect they are not. If the phase just happened to be 90 degrees different across the low frequencies, "reversing" the phase to one of them would have absolutely no effect at all. That wouldn't' be all that much of a "surprise", eh?

These kind of details need to be clearly established when doing this kind of "experiment" or you risk findings that are just rubbish.
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Last edited by CharlieLaub; 15th June 2019 at 09:00 PM.
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Old 15th June 2019, 08:59 PM   #32
jimmyjazz is offline jimmyjazz  United States
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Yes, CharlieLaub, I completely agree. It's not always easy to conceive experiments that generate results which are reliable. Lots of things matter. Everything must be accounted for. Your phase response example (even if amplitude response is identical) could throw all kinds of things out of whack. Thanks.
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Old 15th June 2019, 09:29 PM   #33
kgrlee is offline kgrlee
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Ben, please post a pic showing your room dimensions and where your speakers, chair & 'accidental position' are.

Posting curves where these are not specified isn't data ... especially if the subject is as in the title.

It's, "OMG, I threw the ball in the air and it landed in a pile of ****. Fortunately, I had loadsa toilet paper."

And yes. Charlie is right to point out your **** is certainly affected by the different piles of **** in each corner.

Last edited by kgrlee; 15th June 2019 at 09:34 PM.
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Old 15th June 2019, 10:32 PM   #34
bentoronto is offline bentoronto  Canada
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Subs with reversed polarity (surprise!)
It takes a whole 5 minutes for somebody to do the two runs and show that their left and right sub annihilate one another when they reverse the wires to one, assuming you are leaving the subs and all else in the system and in your room unchanged from before the test.

How about some data instead of endless jaw-jaw?

Yes of course there is substantial cancellation and modified FR when in reversed polarity. Let's see how much in the rooms of these critics.

B.
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Last edited by bentoronto; 15th June 2019 at 10:37 PM.
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Old 15th June 2019, 10:36 PM   #35
jimmyjazz is offline jimmyjazz  United States
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You're arguing a point that hasn't been made. Everything -- EVERYTHING -- depends on the details. No one test makes a definitive statement without a clear accounting for those details. You seem resistant to this idea. The very fact that your original test utilized 2 subs of radically different design makes it extraordinarily difficult to draw broad conclusions from your results.
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Old 15th June 2019, 10:56 PM   #36
ICG is offline ICG  Germany
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You are absolutely right, it's wasted time, energy and effort. Everyone then has to read up to the last post. Multiplied with all the users who tried to help so far, that's even more, a huge ammount of time wasted. I hate it if someone asks such questions, doesn't give informations and puts up unfounded conclusions and 'measured facts'.
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Old 15th June 2019, 11:35 PM   #37
rickmcinnis is offline rickmcinnis  United States
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I use two RYTHMIK 15 subs in the back of my room - 0nly place I could put them. Only from 20 to 50 hz.

There is no question I get greater output and a smoother phase plot with them out of phase.

One is about 9 feet up and the other side is on the floor. I have adjusted for delay for all but the woofer 9 feet up This makes a very big difference. Since the woofers are in the rear I have delayed the main speakers and the woofer on the floor sounded best not all the way in the back so I have delayed it, also

Using a xilica box and REW and thousands of measurements and adjustments. Still the best those drivers perform is when they are out of phase. Measurements taken at the listening chair at ear height.

Last edited by rickmcinnis; 15th June 2019 at 11:37 PM.
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Old 16th June 2019, 12:02 AM   #38
jimmyjazz is offline jimmyjazz  United States
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rickmcinnis, I have no problem believing that. I would ask, and no offense, but are they both wired with the same polarity? Does a 9V battery make both drivers move out (or both in)?

Regardless, two identical subs in different placements, one advanced in phase ahead of the mains, the other not . . . not surprising that flipping phase on the other makes a difference (one way better than the other).
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Old 16th June 2019, 01:15 AM   #39
bentoronto is offline bentoronto  Canada
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Subs with reversed polarity (surprise!)
Quote:
Originally Posted by rickmcinnis View Post
I use two RYTHMIK 15 subs in the back of my room - 0nly place I could put them. Only from 20 to 50 hz... Using a xilica box and REW and thousands of measurements and adjustments. Still the best those drivers perform is when they are out of phase. Measurements taken at the listening chair at ear height.
Well rickmcinnis, I guess it is just you and me, people with experience, versus the Theoreticians.

When I had a giant OB sub along a side wall, I just could never decide if I (and my many REW plots) preferred the orthogonal or the reversed polarity. For sure, I am not favouring generally reverse polarity. Just saying, systems need to be tested.

And if you are smart enough to have a DSP, you should wiggle the phase a bit. Below are shown two curves with my subs and my large ESL panels. In one of the plots one of the subs has a mere 45-degrees added (or subtracted, not sure).

I leave it to all the perceptive readers to guess which is the one that looks a whole lot better (OK, mostly in one dramatic place near the crossover point*). Let me add, after a long time of listening to my speakers, I certainly couldn't guess which curve I was listening to without looking at my Behringer DSP.

B.
* beats me how the heck anybody with a passive crossover could ever get their system right
Attached Images
File Type: jpg both w and wo 45.jpg (52.1 KB, 65 views)
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Last edited by bentoronto; 16th June 2019 at 01:22 AM.
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Old 16th June 2019, 01:21 AM   #40
nigelwright7557 is offline nigelwright7557  United Kingdom
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Unless the subs are right next to each other there will cancellation and addition all around the room.
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