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Author Topic: Reversing polarity on Speakers  (Read 7466 times)

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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Stop confusing the issue with facts and logic!

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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