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Author Topic: Reversing polarity on Speakers  (Read 7468 times)

Armando Ramos

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Reversing polarity on Speakers
« on: December 01, 2015, 02:09:34 pm »

I bought a new Crown Audio XLI3500 amp for my two 12 in. EAW FR129z speakers. I noticed the the on the amp, the wiring shows the following:

PIN 1+, 1-

On the speaker it shows:

PIN1-...-
PIN1+...+

Does this mean the polarity needs to be reversed? I have attached screen shots of the back of the amp and speaker.
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Steve M Smith

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Re: Reversing polarity on Speakers
« Reply #1 on: December 01, 2015, 02:30:08 pm »

No.  Positive speaker connection is on pin 1+ and negative connection is on pin 1- on both amp and speakers.


Steve.
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Armando Ramos

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Re: Reversing polarity on Speakers
« Reply #2 on: December 01, 2015, 03:19:32 pm »

No.  Positive speaker connection is on pin 1+ and negative connection is on pin 1- on both amp and speakers.


Steve.

Thanks for you reply, Steve.

The reason I asked the question is after I hooked everything up, I turned on the PA system, calibrated the speakers using an analyzer mic and software that came with my sound mixer (Presonus Studiolive AI), and noticed there was too much bass and low mids. I reversed the polarity of the right speaker and it cleared up the sound. It was a drastic change. This lead me to believe that perhaps the polarity was off.

I switched the polarity back and I tried eqing the bass and mid-lows out but it helped a little.

My setup is as follows:
Presonus Studiolive AI Mixer -> Behringer Super-X Pro CX3400 Crossover -> Crown Audio XLI3500 amp ->EAW FR129z speakers
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Steve M Smith

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Re: Reversing polarity on Speakers
« Reply #3 on: December 01, 2015, 03:47:14 pm »

Reversing the polarity will cause all sorts of cancellations, possibly more apparent at lower frequencies.

Play a CD you know well and walk around the room to see how it changes with the polarity the same on both speakers then with one reversed.

I will say that if it did not sound great after calibration, then perhaps the calibration tool is not too good.  I would set everything flat then listen to see if anything needs adjusting.


Steve.
« Last Edit: December 01, 2015, 03:49:46 pm by Steve M Smith »
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Armando Ramos

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Re: Reversing polarity on Speakers
« Reply #4 on: December 01, 2015, 04:45:02 pm »

Thanks again, Steve! I'm going to re-calibrate the mains by getting all the frequency as flat as possible.
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Scott Carneval

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Reversing polarity on Speakers
« Reply #5 on: December 01, 2015, 07:12:43 pm »

It's pretty common for bass frequencies to cancel when the polarity is reversed on one speaker.  The 'muddiness' you're referring to might just be a characteristic of the room or of the speaker, or it's just not what you're used to. 

What tool are you using to flatten the response? If you're using a simple RTA it's not giving you very accurate info. If you're using a dual-channel FFT you would be able to tell that the polarity was wrong when you compared the measurements of each speaker.
« Last Edit: December 01, 2015, 08:30:23 pm by Scott Carneval »
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Luke Geis

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Re: Reversing polarity on Speakers
« Reply #6 on: December 02, 2015, 01:22:39 am »

I would say this. For subs at least, it is not a big deal if they are out of polarity, as long as all the subs are in the same polarity. Chances are pretty good that the 180 deg phase shift from the subs being out of polarity will bring it closer in phase to the tops? A 2 pole ( second order ) crossover will shift the phase 180 deg. Assuming the subs and the tops were in nearly exact alignment, the inversion of polarity on the subs would actually work out better. The tops are what are actually ahead in time, inverting the polarity of the subs doesn't address the exact time issue, but at least makes it so that the pulses are going in the same direction. Now this is in a perfect world of course where everything is in perfect alignment...... Not the case so we have to resort to other measures.

The low down and dirty way to determine if the subs are in the best polarity, is to simply invert it while listening to music. The direction that provides the most bass in the desired listening area is the polarity you want.

The next best way to determine bass polarity and alignment is to send an 80hz sine wave to one half of the PA ( one top and the sub for either left or right ). If the polarity is correct there will be no cancellations and you will clearly hear the 80hz tone. Flip the polarity on the subs and the tone should go NULL ( cancel out ) and not be heard as much if at all. Now you can address the time domain. You know that the sub is out in relation to the top. So now if you delay the output to the tops, the null should shift in and out. Your looking for the highest null with the lowest delay time. When this has been achieved you place the subs back into the correct polarity ( again in relation to the tops ) and you should have a pretty well aligned system. The one thing I will point out as a flaw with this technique is that room nodes and reflections will effect the results. You are looking for the best result you can in the desired listening position. If you move around while listening to the null, it will change due to signal path lengths and reflections.
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Steve M Smith

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Re: Reversing polarity on Speakers
« Reply #7 on: December 02, 2015, 02:56:02 am »

I would say this. For subs at least, it is not a big deal if they are out of polarity, as long as all the subs are in the same polarity

I initially thoght this was a crossover frequency with subs issue, but looking at Armando's equipment list, he only mentions two EAW FR129z speakers.

Even if his misunderstanding of the speaker and amp labelling was correct, he should have reversed both speakers which would have ended up with both having the  same polarity.

Instead he has trhe left speaker with the opposite polarity to the right speaker.  That's never going to be good!


Steve.
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Ivan Beaver

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Re: Reversing polarity on Speakers
« Reply #8 on: December 02, 2015, 07:15:19 am »

Regarding the wiring-they are saying the same thing-it is just printed different.

There is no simple answer as to whether or not to reverse the polarity of the subs.

There are a lot of "it depends" and without knowing the answer to those questions, a guess has not merit at all.

In some cases you need to flip the POLARITY (NOT phase) of the adjacent freq band. 

In others cases you don't.

It depends on the particular design/layout of BOTH the full range cabinet and the sub, the physical location of both cabinets, the delay used on either on (if any), the actual crossover freq and type used on each cabinet.

Change any one of these and you may (or may not) have to change the polarity back.

What you are looking for is a good PHASE response between the sub and top.

If you get it right, you will get a nice addition and if the crossover is set properly (this OFTEN means NOT at the same freq), the response will be nice and smooth between the cabinets.

If it is not set right, you will end up with a hole in the response.

Without actual measurements, there is no way to begin to guess at what is correct.
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Steve M Smith

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Re: Reversing polarity on Speakers
« Reply #9 on: December 02, 2015, 07:17:14 am »

What you are looking for is a good PHASE response between the sub and top.
The OP doesn't have subs.  It's just two full range cabinets (unless I'm reading it wrong).


Steve.
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Re: Reversing polarity on Speakers
« Reply #9 on: December 02, 2015, 07:17:14 am »


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