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How do I test amplifier speaker output polarity?

Hacdrag

New Member
I know how to test speaker polarity. The problem is that I purchased an amp module, and the wiring diagram was wrong, as when I played a stereo separation test, the channels were transposed. I found another diagram online for the same device and got the channels right. The system sounds fine to me, but I'm still worried that maybe the second diagram was wrong, and something is wrong with polarity. So, the question is, how do I check the polarity of the amplifier's block terminal connectors that I put the speaker wires in?
 

crutschow

Well-Known Member
Most Helpful Member
There is no correct polarity, only that all the speaker polarities are the same.

If the speakers are out of phase, then there will be a hole in the middle (sound like separate speakers) and the bass will be less.
So just reverse the polarity on one speaker and see if it sounds better or worse.
 

ronsimpson

Well-Known Member
Most Helpful Member
Run the same signal through both speakers. (low frequency) I walk back and forth left--right looking for a dead spot in the middle. If you find a dead spot one of the speakers is reversed.
 

Hacdrag

New Member
There is no correct polarity, only that all the speaker polarities are the same.

If the speakers are out of phase, then there will be a hole in the middle (sound like separate speakers) and the bass will be less.
So just reverse the polarity on one speaker and see if it sounds better or worse.
 

Hacdrag

New Member
Run the same signal through both speakers. (low frequency) I walk back and forth left--right looking for a dead spot in the middle. If you find a dead spot one of the speakers is reversed.
Can't figure out how to multiquote, so crutschow as well:

Thanks guys, but I think I damaged my ears by listening to loud music all day, as I can't find anything wrong with the speakers, no matter how I wire the polarity. :) I did run some decibel tests:

60 HZ sine wave - right speaker with the original polarity 3 tests at 30 seconds:

58.9
59.8
59.2
_____________

Average - 59.3


Same test on right speaker with polarity reversed:

56.4
56.5
56.1
____________________

Average = 56.333

Same test on right speaker with original polarity with increased volume:

60.7
60.6
60.1
______

Average = 60.467

Same test on right speaker with polarity reversed:

59
57.4
59.5

_________________

Average = 58.633



Left speaker with the original polarity, keeping the increased volume:

59
57.4
59.5
____________

Average = 58.633

Left Speaker with reversed polarity:


56
59.2
58.8
__________

Average = 58

I was frustrated and surprised that the left speaker results were almost the same, but was getting too tired to run more tests.

So, with a little evidence, (are the decibel differences a valid measurement and are the differences enough?) plus the fact that the second diagram at least got the channels right, I'm keeping the original polarity.

The way I have this wired is - starting from the outside, opposite the volume control - right negative, right positive, left positive, left negative. Is this a normal order for amp modules, or can it be completely random?


Ty
 

Nigel Goodwin

Super Moderator
Most Helpful Member
You're VASTLY over complicating this - as already said, it doesn't matter which polarity they are, as long as all are the SAME polarity.

Connect the speakers up, play some nice bass heavy music (go heavy metal!! :D), and see if pictures are falling off the walls - now reverse ONE of the speakers, and play it again - you should either have vastly improved bass, or vastly reduced bass. With the polarities opposite the low frequencies cancel each other out.

Your pointless tests did nothing because you didn't run both speakers at the same time.

There's been fairly silly suggestions about 'holes in the stereo image' - but it's absolutely blindingly obvious, with the speakers in opposite polarities you get pretty well zero bass.
 

ronsimpson

Well-Known Member
Most Helpful Member
There's been fairly silly suggestions
In small rooms, I agree the low frequencies will be low with a phase reversal. There is so much of the sound bouncing off the walls I can see why finding the null in the middle is hard.
I set up speakers on large stages where the speaker separation is large, and walls are fare away and non-reflective.

Speakers are much the same as RF antennas. A phased array of antennas (or speakers) makes a directional radiator. At 60hz I can spot a reversed speaker very easy.

Math. Speed of sound 1000feet/second. 10feet/0.01sec There is 360 degree phase delay every 10 feet at 100hz. There is 180 phase reversal at 50hz in 10feet. Three way speakers can have holes in their frequency response because the distance from speaker to the ear is different for each speaker. It is common for a tweeter to be much closer than the base. 500hz 1 ft=180 degrees and 5khz 1 inch = phase cancelation.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
In small rooms, I agree the low frequencies will be low with a phase reversal. There is so much of the sound bouncing off the walls I can see why finding the null in the middle is hard.
I set up speakers on large stages where the speaker separation is large, and walls are fare away and non-reflective.

Just as easy, and just as obvious (if not more so, due toi the higher levels of bass), although I've only ever done fairly small stages - including one occasion where as well as either side of the stage been reversed, individual speakers in each stack were reversed as well - how???.

On that occasion I had to 'borrow' a 9V battery out of a guitar pedal to test the polarity of every speaker and lead.
 

crutschow

Well-Known Member
Most Helpful Member
There's here's been fairly silly suggestions about 'holes in the stereo image'
It may not be the best way to check speaker phasing, but it's not "silly".
There is a definite difference in the apparent sound halfway between the speakers depending on their relative phase.
 

crutschow

Well-Known Member
Most Helpful Member
If you want to easily change one speaker polarity, add a cross-wired DPDT switch (below) in series with the two speaker wires, to reverse the connection with a flip of the switch.
That will allow you to readily hear the difference.

1652556759898.png
 

Ramussons

Active Member
Connect the speakers.

If the amplifier is not a bridge output: One output is ground, the other "hot".
Input the same input to both channels.
Measure the voltage between Hot-Hot. If its much lower than with Hot-Gnd, the outputs are in Phase.

If its a bridge output,
Mark the speaker outputs as L1/L2 and R1/R2.
Feed the same input to both the channels.
Measure the voltage between L1-R1 and L1-R2 (or R1-L1 and R1-L2).
If the 1-2 output is higher than 1-1 (or 2-2), the output is in phase.
 

audioguru

Well-Known Member
Most Helpful Member
When the stereo speakers are close together then reversed phase of one speaker causes an obvious reduction in bass sounds.

A good phase test for bookcase speakers is to have them facing each other close together. Correct phase= loud bass, wrong phase= no bass.
 

augustinetez

Active Member
I used to have a 45 rpm licuorice frisbee that contained several tests for setting up stereo systems, one being "the hole in the middle" test for correct speaker phasing (another track was a steam train moving right to left).
 

augustinetez

Active Member
or is it left to right?
Definitely right to left, there's a more modern version (1966 :) ) on Youtube that has all the tests but using a diesel engine and carriages
(and it also has a test for speaker polarity as well as phasing).

Mine was a little earlier, 1963 I think, similar to the linked one, may have possibly come with an electronics magazine of the time - I got it from my old man when he stopped building stereo systems for himself.
 

Hacdrag

New Member
I can't trust anything about the last YouTube link, because the channels are wrong, and one of the commentators stated that the phasing was wrong as well. I solved the issue by testing the speakers with this video:


There is more bass during the "In Phase" segment, than the "Out of Phase" segment, so my wiring from the second diagram I found online was correct.

I'm playing around with a 10 Watt per channel amp board, and using some small loudspeakers in MDF enclosures, not using a full-size amplifier or bookshelf speakers. So, as I'm not getting the highest quality sound or best bass response to begin with, I wasn't unable to tell the difference in bass response between correct wiring and wiring that caused the speakers to be out of phase. I had to change the wiring between tests, and the difference in bass response wasn't noticeable enough for me to tell the difference. The YouTube test I linked to let me test the system without changing the wiring and when I was standing in front and in-between the speakers, I could hear the difference.

Thanks for all the replies. The problem is solved!
 

audioguru

Well-Known Member
Most Helpful Member
Your new recording is correct. The out-of-phase parts made me feel weird.
Some modern little speakers produce bass. I saw one on sale at Costco and I could not find their hidden subwoofer because the little speaker was doing it. It gave me goose bumps to hear the bass produced by the little speaker. It was expensive.
 

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