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Author Topic: Reversing polarity on Speakers  (Read 7469 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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Armando Ramos

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Re: Reversing polarity on Speakers
« Reply #10 on: December 02, 2015, 09:02:50 am »

Thank you all for the helping me with this!

 I do have a sub and its EAW SB48zP.  It sits under the stage and its 2 feet ahead of the mains. I'm new to this.

 I'm using the PRM mic that came with my Presonus studiolive AI sound mixer. I downloaded and installed the software that came with mixer on my laptop. It's a SMAART wizard and it had me point the PRM mic on axis with the left speaker and then the software does the rest.

Any recommendations on measurement tools that would help me configure my system?
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Scott Carneval

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Re: Reversing polarity on Speakers
« Reply #11 on: December 02, 2015, 09:55:09 am »

Thank you all for the helping me with this!

 I do have a sub and its EAW SB48zP.  It sits under the stage and its 2 feet ahead of the mains. I'm new to this.

 I'm using the PRM mic that came with my Presonus studiolive AI sound mixer. I downloaded and installed the software that came with mixer on my laptop. It's a SMAART wizard and it had me point the PRM mic on axis with the left speaker and then the software does the rest.

Any recommendations on measurement tools that would help me configure my system?

Armando,

The fact that you're using subs changes everything.  In your second post you said:

Quote
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.

This leads me to believe that you ran an 'auto EQ', and it probably added a whole bunch of boosts and cuts to the low end to try to correct for mis-aligned speakers.  With your sub two feet out in front of the mains, there will be a different time arrival from each speaker, and this will result in phase cancellation at frequencies where the subs and mains overlap.  Further, you're probably experiencing some cancellation from the two FR129z's because they overlap throughout the entire passband.  To get an 'accurate' reading from the measurement mic you need to turn off whichever side you're not currently measuring.  I use 'accurate' very loosely here because there is really nothing accurate about an Auto EQ.

I'm afraid the sub you're using is woefully inadequate versus your mains. Typically you want to have subs that are cable of 10+ db more than the mains, not the other way around.  Also, I'm assuming here that you only have one sub, as you referred to it singularly.  You can pretty much ignore what I said above about phase aligning the sub to the mains, as there is no practical way to align two outward mounted mains to a center mounted sub.  This isn't the end of the world, and these configurations are used successfully all the time, but you won't have proper alignment through your crossover region. 

I think your biggest problem here is that the auto EQ tried to fill in all of the nulls. Or maybe you did this yourself manually to try to get a 'flat' graph on the screen. The most important thing when measuring or aligning a system is to distinguish what you CANNOT fix from what you can fix.  If you're serious about working with sound, I strongly recommend attending a SMAART training class by Rational Acoustics.  They spend about 20% of the class explaining the software and the other 80% of the class explaining all sorts things about sound and acoustics.  It's sort of like drinking from a firehose, but it puts a new perspective on things.


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Armando Ramos

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Re: Reversing polarity on Speakers
« Reply #12 on: December 02, 2015, 11:58:54 am »

Thanks Scott for your feedback. I manually adjusted the EQ based on the analysis form the PRM mic this morning and tired to get the frequencies as flat as possible. I've attached a screen shot of this. The mains are sounding much better.

I'm definitely going to look into SMAART training class by Rational Acoustics.

Thanks again you all for your help!
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Scott Carneval

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Re: Reversing polarity on Speakers
« Reply #13 on: December 02, 2015, 12:04:08 pm »

Thanks Scott for your feedback. I manually adjusted the EQ based on the analysis form the PRM mic this morning and tired to get the frequencies as flat as possible. I've attached a screen shot of this. The mains are sounding much better.

I'm definitely going to look into SMAART training class by Rational Acoustics.

Thanks again you all for your help!

Where do you have the crossover set? You should have a high-pass filter for the mains and a low-pass filter for the sub.  Something seems wrong if you have to cut that much and that wide at 100hz.  Is there another EQ either on the board or somewhere in the system that is adding a boost at 100hz? Otherwise I think your crossover is not set properly.
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Jonathan Johnson

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Re: Reversing polarity on Speakers
« Reply #14 on: December 02, 2015, 05:16:35 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.

The Speakon connector has four terminals designated 1+, 1-, 2+, and 2-. The labeling on the amp is simply indicating which amplifier channel each designated pin connects to. Because it does not indicate differently, we can safely assume that the "+" pins are indeed positive and the "-" pins are indeed negative polarity.

It is not so important that the polarity be correct; but it must be consistent among all speakers (drivers) in the same plane. Any delay fills must also have consistent polarity.

If you have fill speakers in a different plane without proper delay, polarity becomes somewhat irrelevant, as you will have time-shift interference either way.
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Armando Ramos

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Re: Reversing polarity on Speakers
« Reply #15 on: December 03, 2015, 02:03:34 am »

Where do you have the crossover set? You should have a high-pass filter for the mains and a low-pass filter for the sub.  Something seems wrong if you have to cut that much and that wide at 100hz.  Is there another EQ either on the board or somewhere in the system that is adding a boost at 100hz? Otherwise I think your crossover is not set properly.

I have the crossover set at 90hz. I have attached photos of my crossover settings.

Could the extra bass be caused by having my mains to close to walls? I have attached a photo with the locations of my speakers.
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Re: Reversing polarity on Speakers
« Reply #15 on: December 03, 2015, 02:03:34 am »


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