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Author Topic: sub polarity  (Read 1641 times)

Kevin Conlon

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sub polarity
« on: January 02, 2017, 11:34:03 pm »

Some one here can settle this for me. When a speaker is mounted in a cabinet of horn or manifold design, where you see the magnet not the cone,  some people have said the speaker should move "in" with the battery test. Meaning reverse polarity. I have a hard time swallowing this. Are not subs built to push air and not try to suck it through the ports? I have heard this more than once. My old mtl2b EVs push air into the cab (the way i use them) ports do the work and it comes out the the rectangles as well as the center of the cab. I have more to ad to this but want some more info before i finish my question.  Thanks,      Kevin.
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Tim McCulloch

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Re: sub polarity
« Reply #1 on: January 02, 2017, 11:42:30 pm »

Some one here can settle this for me. When a speaker is mounted in a cabinet of horn or manifold design, where you see the magnet not the cone,  some people have said the speaker should move "in" with the battery test. Meaning reverse polarity. I have a hard time swallowing this. Are not subs built to push air and not try to suck it through the ports? I have heard this more than once. My old mtl2b EVs push air into the cab (the way i use them) ports do the work and it comes out the the rectangles as well as the center of the cab. I have more to ad to this but want some more info before i finish my question.  Thanks,      Kevin.

Waves go above and below the baseline so at some point in the waveform it will "suck" and then "blow" and repeat until the signal is no longer present.

Note that physical orientation of the driver may not be indicative of the acoustic output polarity.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Len Zenith Jr

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Re: sub polarity
« Reply #2 on: January 02, 2017, 11:45:37 pm »

Are not subs built to push air and not try to suck it through the ports?

They do both, anywhere from 20 - 150 times per second. All your drivers do is vibrate the air back and forth at the frequency they are playing. The important part is to make sure that the phase of your subs line up with the phase of your tops over the x-over frequency over as much of the audience area as possible.
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Kevin Conlon

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Re: sub polarity
« Reply #3 on: January 03, 2017, 01:09:53 am »

Waves go above and below the baseline so at some point in the waveform it will "suck" and then "blow" and repeat until the signal is no longer present.

Note that physical orientation of the driver may not be indicative of the acoustic output polarity.
Is this something i need to test for? I have tested this to some degree, but it seems the speaker should push into the cab on a positivs pulse. i know it blows both ways but my real question is where should the pulse start + or -  ? I think if it works with the tops its good. My rest of the question is a friend i work with turned the speakers around in his ev subs to make them " front loaded ". This is my real question. Did his reversal change the way his cabs work? We will do some side by side comparison before we take these out for use, combing, etc. what did he change with the reverse oriantation?  Sorry if i am sounding dumb, i am tring to learn and you people are good at teaching.     Kevin
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Len Zenith Jr

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Re: sub polarity
« Reply #4 on: January 03, 2017, 01:22:37 am »

. i know it blows both ways but my real question is where should the pulse start + or -  ?
Some people will say that the initial vibration in the chest should be a positive (compression) pulse for maximum impact. I think that is all in their head at the air pressure changes from + to - so fast that the only ones who can hear the difference are the ones aware of the subs setting (placebo effect).

what did he change with the reverse oriantation?

The volume of the cabinet, the polarity too unless he reversed the hook up wires.
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Jeff Bankston

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Re: sub polarity
« Reply #5 on: January 03, 2017, 01:56:42 am »

If you have banana plugs just reverse on end and see it hear or feel any difference. A folded horn cabinet is still pushing the air toward you if thats what you have.
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Keith Broughton

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Re: sub polarity
« Reply #6 on: January 03, 2017, 07:23:48 am »

The idea that you will feel more "impact" when a speaker "pushes" air towards you is a bit misplaced.
As you can clearly feel, when you apply a battery to a driver and it moves, you don't feel any real pressure even though the driver might be moving quite a bit.
The "impact" you hear (feel) of is a group of waves propagated into the air over a specific time period with a fast rise time.
Positive or negative polarity will sound the same with a kick drum hit.
If you are keen to use a battery test, it is really only good to make sure the same type of speaker exhibits similar polarity so if you have a bunch of the same cabinet, you can confirm they are working together.
However, just because the drivers are all moving "forward" you cannot assume that means different types of cabinets will be working "in phase (polarity) in actual use.
The real issue with sub polarity in system integration, as indicated previously, is the get phase correlation at the crossover freq.
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Ivan Beaver

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Re: sub polarity
« Reply #7 on: January 03, 2017, 08:11:22 am »

Phase and polarity are very different things-although (sadly) they are misused and interchanged often within our industry.

What is correct for YOUR system?

It depends on the particular cabinets, the crossover points, delay times used etc.

The CORRECT answer is one that has the smoothest/flattest PHASE response around crossover.

So that could be IN or OUT of polarity.  Nobody knows without actually measuring YOUR system.

THERE IS NO correct answer that fits all situations.

But in terms of polarity, you have a 50/50 chance :)

And simply flipping the polarity and listening for the "loudest bass" DOES NOT mean it is correct.

It "could" be correct for the notes in the song you are listening to, but in a different song (in a different key) you may be cancellation at those notes.

MEASUREMENT (NOT RTA) is the best way to find the proper answer.
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Ivan Beaver
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Keith Broughton

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Re: sub polarity
« Reply #8 on: January 03, 2017, 02:46:40 pm »



But in terms of polarity, you have a 50/50 chance :)


I'll take those odds Ivan  ;D ;D
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Paul G. OBrien

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Re: sub polarity
« Reply #9 on: January 03, 2017, 03:21:27 pm »

Is this something i need to test for? I think if it works with the tops its good.
Yes if it works it's generally good but optimizing time alignment between cabs or is something everybody should test for IMO.


My rest of the question is a friend i work with turned the speakers around in his ev subs to make them " front loaded ". This is my real question. Did his reversal change the way his cabs work?
No but it would change the frequency response some and combining these with identical cabs with conventionally mounted drivers would likely produce very poor results.
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Ivan Beaver

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Re: sub polarity
« Reply #10 on: January 03, 2017, 04:09:15 pm »



 No but it would change the frequency response some and combining these with identical cabs with conventionally mounted drivers would likely produce very poor results.
Actually it DID change the performance-for the worse.

When the drivers were turned around, the internal cubic volume of the cabinet was less-so they would not go as low.

The difference between having them front loaded and flipped around is TWICE the air volume occupied by the driver.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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Tim McCulloch

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Re: sub polarity
« Reply #11 on: January 03, 2017, 07:15:53 pm »

My rest of the question is a friend i work with turned the speakers around in his ev subs to make them " front loaded ". This is my real question. Did his reversal change the way his cabs work? We will do some side by side comparison before we take these out for use, combing, etc. what did he change with the reverse oriantation?  Sorry if i am sounding dumb, i am tring to learn and you people are good at teaching.     Kevin

Do you have a pair of unmodified units to compare with?

Without a comparison there will be a very strong "confirmation bias" at work and a whole lot of denial about the Emperor's nakedness.

He didn't improve anything and almost certainly made it worse.  Ivan's response is spot on.  The change in air volume will fundamentally change the acoustic output of the loudspeaker.

{cynicism alert}
The confirmation will come when, while attempting to make them sound like they used to, he blows them up.... <very evil laugh> {/cynicism alert}

Tim "hey buddy, you want fries with that?" Mc
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Ivan Beaver

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Re: sub polarity
« Reply #12 on: January 03, 2017, 07:35:04 pm »

My rest of the question is a friend i work with turned the speakers around in his ev subs to make them " front loaded ". This is my real question. Did his reversal change the way his cabs work? We will do some side by side comparison before we take these out for use, combing, etc. what did he change with the reverse oriantation? 
The problem is that many people "think" that just because they changed something that was DESIGNED A SPECIFIC WAY, that "somehow magically" it is "better".

In many cases changing it makes it worse-but since it is "custom modified", somehow that makes it "better".

There is a lot of effort that goes into the design.

There is a REASON the driver was mounted the way it was.  NOT just an accident waiting for somebody to "discover".

Or often it "may" get better in some aspect, but gets worse in others..

This is NOT saying that all things cannot be improved.  Very often they can.  But this comes from figuring out what the actual issue is, then addressing that issue.

In my opinion, to prove if the change works or not, is to have before and after measurement.
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Ivan Beaver
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Kevin Conlon

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Re: sub polarity
« Reply #13 on: January 04, 2017, 08:39:11 pm »

Do you have a pair of unmodified units to compare with?

Without a comparison there will be a very strong "confirmation bias" at work and a whole lot of denial about the Emperor's nakedness.

He didn't improve anything and almost certainly made it worse.  Ivan's response is spot on.  The change in air volume will fundamentally change the acoustic output of the loudspeaker.

{cynicism alert}
The confirmation will come when, while attempting to make them sound like they used to, he blows them up.... <very evil laugh> {/cynicism alert}

Tim "hey buddy, you want fries with that?" Mc
  Yes he has 4. I think he won't have a problem Playing with them. Ivan is very right in changing the volume (how can you not take his advice). We have not used his gear and mine  together yet. We may need to in the spring as we could have 8 18's a side with both of our stuff. Thanks to all who helped.  About the confirmation, for some reason he is good at reconing speakers.   Thanks to all    Kevin
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Tim McCulloch

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Re: sub polarity
« Reply #14 on: January 04, 2017, 08:57:59 pm »

  Yes he has 4. I think he won't have a problem Playing with them. Ivan is very right in changing the volume (how can you not take his advice). We have not used his gear and mine  together yet. We may need to in the spring as we could have 8 18's a side with both of our stuff. Thanks to all who helped.  About the confirmation, for some reason he is good at reconing speakers.   Thanks to all    Kevin

That's good.  Not being sarcastic, because if you learn why something performed in a way that was not anticipated the cost putting in a cone kit or 2 is relatively cheap tuition at Yee Olde Skool of Harde Knox®.

It gets a bit silly if all you learn is "well, we won't do THAT again" over and over and over....

While it's generally pleasing to see folks explore their curiosity with experimentation I think that having some predicted, specific outcome to test for is important.  Does it go lower?  With how much output?  Does it get louder?  Where in the operational pass band does that happen?  Does it have superior or inferior power handling, etc?  A subjective "well, it sounds better to me" is another incident of new clothes for the Emperor.

I made a fair bit of sawdust back in the day (over 30 years ago).  Part of that was educational, part of that was perceived thrift, part based on enough dangerous "knowledge" about loudspeaker systems to blow up some transducers and amps.  The latter was regrettable at the time but provided valuable experience upon which to build.

Blowing up a few things is only about money or any damage to your reputation if it happens on a gig, rather than under test.  Experiment on.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Kevin Conlon

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Re: sub polarity
« Reply #15 on: January 04, 2017, 09:04:42 pm »

The problem is that many people "think" that just because they changed something that was DESIGNED A SPECIFIC WAY, that "somehow magically" it is "better".

In many cases changing it makes it worse-but since it is "custom modified", somehow that makes it "better".

There is a lot of effort that goes into the design.

There is a REASON the driver was mounted the way it was.  NOT just an accident waiting for somebody to "discover".

Or often it "may" get better in some aspect, but gets worse in others..

This is NOT saying that all things cannot be improved.  Very often they can.  But this comes from figuring out what the actual issue is, then addressing that issue.

In my opinion, to prove if the change works or not, is to have before and after measurement.
I think somewhere somone told him to do it, but i don't know. I always bitch about Honda and Yamaha about over doing things. These guys should work on there stuff after it's been in the feild for 10 years. Tell the customer you have to remove the engine to do a valve adjustment and it will be 800.00 and try to tell them it's by design, some don't get it, some do. That speaker was put that way for a reason. I get that. Others say " it sounds better" it is mostly mental. I wish i had real gear to test with but i don't. To the motorcycle reference, these designers, most of the time know there shit and did it for a reason. The same reason you should buy a system that was made to work together by the people who know. One day i may have that but right now i am trying to make the best of what we have. Thank you    Kevin.
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Ivan Beaver

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Re: sub polarity
« Reply #16 on: January 04, 2017, 09:56:29 pm »


While it's generally pleasing to see folks explore their curiosity with experimentation I think that having some predicted, specific outcome to test for is important.  Does it go lower?  With how much output?  Does it get louder?  Where in the operational pass band does that happen?  Does it have superior or inferior power handling, etc?  A subjective "well, it sounds better to me" is another incident of new clothes for the Emperor.

I made a fair bit of sawdust back in the day (over 30 years ago).  Part of that was educational, part of that was perceived thrift, part based on enough dangerous "knowledge" about loudspeaker systems to blow up some transducers and amps.  The latter was regrettable at the time but provided valuable experience upon which to build.

Blowing up a few things is only about money or any damage to your reputation if it happens on a gig, rather than under test.  Experiment on.
One of the things that "should" be done is at least some simple basic measurements.

That way you can help to qualify the results.  If you don't, it is "simply opinion" and different people listen for different things.
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Ivan Beaver
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Craig Hauber

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Re: sub polarity
« Reply #17 on: January 04, 2017, 11:01:52 pm »

The problem is that many people "think" that just because they changed something that was DESIGNED A SPECIFIC WAY, that "somehow magically" it is "better".

In many cases changing it makes it worse-but since it is "custom modified", somehow that makes it "better".

There is a lot of effort that goes into the design.

There is a REASON the driver was mounted the way it was.  NOT just an accident waiting for somebody to "discover".

Or often it "may" get better in some aspect, but gets worse in others..

This is NOT saying that all things cannot be improved.  Very often they can.  But this comes from figuring out what the actual issue is, then addressing that issue.

In my opinion, to prove if the change works or not, is to have before and after measurement.
If they are that single-18 "subscoop" type cabinet (SH1810L, T18, or whatever other model numbers it was sold under) Then EV themselves sold front-loaded earlier versions before flipping the driver for later versions of the same box -they did change to a higher power driver, perhaps it was their way to accommodate that without re-tooling the box?
Anyways having the motor structure outside the box has got to benefit cooling and onset of power compression even if by just a little bit
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Craig Hauber
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Raul Suarez

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Re: sub polarity
« Reply #18 on: January 05, 2017, 05:21:26 pm »

It was Dr. Don that argued that the correct polarity for subs was positive voltage moves cone away from magnet.  His rational was that the attack was the loudest and that the Xtotal of a woofer was greater in an outward direction.  Moving toward the magnet could cause bottoming out.

Of course this rational does not question how much greater the first half cycle is than the second half cycle.  ;-)

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Don T. Williams

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Re: sub polarity
« Reply #19 on: January 05, 2017, 06:03:16 pm »

It was Dr. Don that argued that the correct polarity for subs was positive voltage moves cone away from magnet.  His rational was that the attack was the loudest and that the Xtotal of a woofer was greater in an outward direction.  Moving toward the magnet could cause bottoming out.

This would assume that every subwoofer driver has unequal movement depending on the polarity of the input signal.  I believe most modern manufacturers try very hard to make their drivers linear, and thus lower in distortion.  They may not always achieve that goal.  I have also seen plenty of woofers where the voice coil jumped out of the gap moving forward.  They moved far past the Xmax.

This also assumes that the cone of the driver is the primary source of the audio output.  At some frequencies, the primary output from a vented box loudspeaker system will be from the loudspeaker enclosures' vent, with almost no cone movement.  For bandpass enclosures with both sides of the cone loaded by an enclosure with a vent, all audio comes from the vents.  There are a lot of different types of bandpass systems including these EV types.
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Kevin Conlon

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Re: sub polarity
« Reply #20 on: January 05, 2017, 09:51:38 pm »

If they are that single-18 "subscoop" type cabinet (SH1810L, T18, or whatever other model numbers it was sold under) Then EV themselves sold front-loaded earlier versions before flipping the driver for later versions of the same box -they did change to a higher power driver, perhaps it was their way to accommodate that without re-tooling the box?
Anyways having the motor structure outside the box has got to benefit cooling and onset of power compression even if by just a little bit
  They are a single 18, not to heavy. I have moved them a hundred times and seen the number, but i have shit for memory. The SH is the one, i think. I will read what i can find about them when i have time and see what EV says the difference is (spec sheets are always right) in them. Looking forward to messing with them when it warms up outside.
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