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Speaker Cabinet polarity ... makes a difference?

Zingeroo

Member
Messages
4,348
My buddy and I both have a Marshall 1965a 4x10 cabinet, both loaded with 8 ohm Celestion 10" Greenbacks.
We were A/B'ing them, because I thought mine wasn't sounding as good as I thought it should.
Same amp, plugged into each cabinet, his was noticeably fatter and more aggressive sounding.
Opened up my cab and checked the wiring. Standard series/parallel, all speakers in phase, all speakers working.
I noticed that the speaker positive was connected to the barrel connection on the jack. Seemed like it should have been on the tip, so I switched it and tested.
Wham! My speaker cab sounded just like his. Fat, tight, aggressive, punchy. Everything it was lacking.

Now I heard that this does not matter, that it only matters when you have another speaker cabinet connected, for phase reasons.

And I know this wasn't a double-blind test, but two guys heard the same thing, and we did have a "control" so it was somewhat scientific.

Anyone want to comment?
 

Silent Sound

Member
Messages
5,243
Could be any number of factors. First guess is the connection you switched out wasn't making good contact before the switch.

What amp were you using? There's a good possibility that the amp's output is reversing the phase. Lots of amps do and no one ever seems to complain or notice. You never hear people complain that the 5e3 flips the phase, but it does. They only seem to care when it's at the speaker.
 

IM4Tone

Member
Messages
3,769
There's lots of Cognitive Dissonance among TPG'ers.
Ever read the one about the 'best/ultimate' power cord that improved the amp's tone?
 

Zingeroo

Member
Messages
4,348
There's lots of Cognitive Dissonance among TPG'ers.
Ever read the one about the 'best/ultimate' power cord that improved the amp's tone?
I did consider that. But as I said, we had a "control" cab that we got to compare against. We both heard it.
 

Zingeroo

Member
Messages
4,348
Could be any number of factors. First guess is the connection you switched out wasn't making good contact before the switch.

What amp were you using? There's a good possibility that the amp's output is reversing the phase. Lots of amps do and no one ever seems to complain or notice. You never hear people complain that the 5e3 flips the phase, but it does. They only seem to care when it's at the speaker.
Using a 2204 clone I built.
As far as a 5e3, since it's an open back amp, maybe it matters less?
 

Corinthian

Member
Messages
1,884
In isolation polarity shouldn't have any affect on the sound. However, assuming you're near enough to the amp and it's loud enough it can affect the way the sound from the speaker interacts with the strings on the guitar. I haven't experimented with this myself but I don't think it's a dramatic effect.
 

Richard Guy

Member
Messages
1,181
Even if a cab has one speaker, polarity does make a tonal difference. Forward firing (speaker cone moves forward with the beginning of the plucked string) or rearward firing (moves backwards on the first pluck) are very different.
 

FFTT

Member
Messages
28,356
When you apply the 9 volt battery test, the speaker cones should all move forward together if they are all in phase with each other.
 

lgehrig4

Member
Messages
6,149
It should make some difference since the cone's first move is outward instead of backwards. Some amps have a switch to do just this only the phase chase happens in the amp
 

huw

Member
Messages
1,262
If you search TGP for 'speaker polarity', username 'Kimock', you'll get a lot of reading on the subject.

:)
 

kimock

Member
Messages
12,520
My buddy and I both have a Marshall 1965a 4x10 cabinet, both loaded with 8 ohm Celestion 10" Greenbacks.
We were A/B'ing them, because I thought mine wasn't sounding as good as I thought it should.
Same amp, plugged into each cabinet, his was noticeably fatter and more aggressive sounding.
Opened up my cab and checked the wiring. Standard series/parallel, all speakers in phase, all speakers working.
I noticed that the speaker positive was connected to the barrel connection on the jack. Seemed like it should have been on the tip, so I switched it and tested.
Wham! My speaker cab sounded just like his. Fat, tight, aggressive, punchy. Everything it was lacking.

Now I heard that this does not matter, that it only matters when you have another speaker cabinet connected, for phase reasons.

And I know this wasn't a double-blind test, but two guys heard the same thing, and we did have a "control" so it was somewhat scientific.

Anyone want to comment?
Yeah, you heard it right.
It's acoustical coupling between the guitar and amp, positive feedback below the threshold of runaway oscillation as opposed to damping.

The string and the speaker are both sound sources. So just like two speakers out of phase, you're going to get cancellation at certain frequencies.
That's negative feedback.

That's what you were hearing with your old cab wiring, you were driving the response of the guitar down with the sound from the speakers. Damping the string vibration.

When you flipped it you were reinforcing the string's vibration, adding energy.
That's the ONLY place in the system you can get positive feedback, get more out than you put in, between the speaker and the string, acoustically.

So yeah, you hear that, although I'd say the biggest benefit is to the touch response of the guitar which helps you play better which always sounds better anyway.
It's still a loop!

The punch line, which you probably missed, is that broad, loose, acoustical coupling doesn't just depend solely on speaker polarity, it also depends on the string's polarity which is a function of where the string is being sensed.
So you're "flipping the loop" with your pickup selector, inverting the positive and negative loop characteristics when you switch between neck and bridge pickups.

Right?
Think of the wave going down the string when you pick it, or look up some vibrating string physics stuff for a graphic but basically the string starts out with a "kink" in it.
That's your pick attack.
The kink travels down the string to the bridge and is reflected, inverted, at the string termination.
It's in the opposite phase now.

So for any division of the vibrating string smaller than the distance between the pickups, the string's motion is reversed in direction over the neck and bridge pickups.

The polarity at the amp will favor one pickup over the other because the string reverses its phase when it's motion is reflected at the bridge.

Blah, blah, blah. .

Yeah, that's a good one tho.
Getting that feeling of the guitar coming alive in your hands because the amp's adding energy to the string instead of pushing it down.

Hittin' or quittin' is how we say it in my neck of the woods.
 

aflynt

Member
Messages
1,742
I've found it has a big effect on how the amp responds but little to no effect on overall timbre. As others have said, it doesn't have to be controlled at the speaker. You could flip it in front of the amp or in the loop and achieve a similar effect. I set up my cabs with two parallel inputs. One normal and one reverse with an isolated jack.

-Aaron
 

Silent Sound

Member
Messages
5,243
Yeah, you heard it right.
It's acoustical coupling between the guitar and amp, positive feedback below the threshold of runaway oscillation as opposed to damping.

The string and the speaker are both sound sources. So just like two speakers out of phase, you're going to get cancellation at certain frequencies.
That's negative feedback.

That's what you were hearing with your old cab wiring, you were driving the response of the guitar down with the sound from the speakers. Damping the string vibration.

When you flipped it you were reinforcing the string's vibration, adding energy.
That's the ONLY place in the system you can get positive feedback, get more out than you put in, between the speaker and the string, acoustically.

So yeah, you hear that, although I'd say the biggest benefit is to the touch response of the guitar which helps you play better which always sounds better anyway.
It's still a loop!

The punch line, which you probably missed, is that broad, loose, acoustical coupling doesn't just depend solely on speaker polarity, it also depends on the string's polarity which is a function of where the string is being sensed.
So you're "flipping the loop" with your pickup selector, inverting the positive and negative loop characteristics when you switch between neck and bridge pickups.

Right?
Think of the wave going down the string when you pick it, or look up some vibrating string physics stuff for a graphic but basically the string starts out with a "kink" in it.
That's your pick attack.
The kink travels down the string to the bridge and is reflected, inverted, at the string termination.
It's in the opposite phase now.

So for any division of the vibrating string smaller than the distance between the pickups, the string's motion is reversed in direction over the neck and bridge pickups.

The polarity at the amp will favor one pickup over the other because the string reverses its phase when it's motion is reflected at the bridge.

Blah, blah, blah. .

Yeah, that's a good one tho.
Getting that feeling of the guitar coming alive in your hands because the amp's adding energy to the string instead of pushing it down.

Hittin' or quittin' is how we say it in my neck of the woods.
That's a mighty big can of worms that you're opening up there. Remember that sound and electricity travel at much different velocities, so acoustic feedback induced by the speaker on the guitar will vary resonance frequencies due to distance. It takes a lot more time for sound to travel through air than it does through wires. In other words, you're always going to be adding some frequencies together and subtracting other frequencies, regardless of the phase at the output of the speaker. At certain distances from the amp, it might sound better in phase, while at others, it might sound better out of phase. Also, room nodes can effect the relationship between these, as can the circuit design of the amp itself since capacitors will shift the phase of the signal within an amp. Due to all of these variations causing different shifts and buildups of frequencies, it will be impossible to have the feedback look you mentioned occur at all frequencies at either 0º or 180º. So the answer isn't going to be as simple as positive or negative feedback, because both will be happening at the same time.

Now with this in mind, I can't think that this acoustic coupling could have that big of an impact on the sound. How many times have you heard someone say that there guitar only sounds good at certain distances from their amp? I think the more likely scenario is confirmation bias. It's easy to expect to hear a difference and believe that you're hearing one, when in fact you are not, when conducting an experiment on yourself. In fact, just yesterday I was mixing a song and turning a bunch of knobs on an EQ for about 2 minutes before I realized the EQ wasn't engaged. I could have sworn I was hearing the effects of the knobs I was turning, but it was just my mind playing tricks on me.
 

kimock

Member
Messages
12,520
That's a mighty big can of worms that you're opening up there. Remember that sound and electricity travel at much different velocities, so acoustic feedback induced by the speaker on the guitar will vary resonance frequencies due to distance. It takes a lot more time for sound to travel through air than it does through wires. In other words, you're always going to be adding some frequencies together and subtracting other frequencies, regardless of the phase at the output of the speaker. At certain distances from the amp, it might sound better in phase, while at others, it might sound better out of phase. Also, room nodes can effect the relationship between these, as can the circuit design of the amp itself since capacitors will shift the phase of the signal within an amp. Due to all of these variations causing different shifts and buildups of frequencies, it will be impossible to have the feedback look you mentioned occur at all frequencies at either 0º or 180º. So the answer isn't going to be as simple as positive or negative feedback, because both will be happening at the same time.

Now with this in mind, I can't think that this acoustic coupling could have that big of an impact on the sound. How many times have you heard someone say that there guitar only sounds good at certain distances from their amp? I think the more likely scenario is confirmation bias. It's easy to expect to hear a difference and believe that you're hearing one, when in fact you are not, when conducting an experiment on yourself. In fact, just yesterday I was mixing a song and turning a bunch of knobs on an EQ for about 2 minutes before I realized the EQ wasn't engaged. I could have sworn I was hearing the effects of the knobs I was turning, but it was just my mind playing tricks on me.
Nah, it's just feedback.
 

Otto Tune

Member
Messages
3,848
Even if a cab has one speaker, polarity does make a tonal difference. Forward firing (speaker cone moves forward with the beginning of the plucked string) or rearward firing (moves backwards on the first pluck) are very different.
It's called ultimate phase, and I'm not sure it's a real thing.
I worked with a client who was particular about phase, and they brought a CD with tone at 1 K. The bottom of the sine wave was chopped off. On a scope, it was just the positive side. Then we played the CD through the signal chain and looked at the output on a scope again. If the signal was now upside down, it was out of ultimate phase. Clever trick, but why? We found equipment that was out of ultimate phase internally. So what?
Now, let's look at the speaker. The speaker cone should move forward as the microphone diaphragm moves backwards, right? But as you move around the room, aren't your ears hearing a different part of the pressure wave? At 10' you might be in phase, but at 15" you may not be. My eyes glazed over.
 

smolder

Platinum Supporting Member
Messages
14,395
So if I have this right... Pickups, magnet orientation, guitar circuit, pedals, the amps gain stages, and the speaker polarity can all effect the phase of the signal as it turns to a physical wave form. If the same signal passes through two different paths (spit to different boards/amps) they can be out of phase, thus canceling out some frequencies and is obviously not optimal.
 

J M Fahey

Member
Messages
2,665
Even if a cab has one speaker, polarity does make a tonal difference. Forward firing (speaker cone moves forward with the beginning of the plucked string) or rearward firing (moves backwards on the first pluck) are very different.
And how would you know?
In fact, how would the speaker know?

There's lots of opportunities in the long path from string to speaker cone to plain lose track of actual string phase, including (what most don't consider), the pickup itself.

To be more precise: guitar signals are unsymmetrical, for various reasons, including which way is the pick moving which is changing all the time, and also the magnetic field strength varies with string to pickup distance , signal won't have the same peak amplitude when moving 1 mm "up" than when moving 1mm "down" , even if acoustically is the same, BUT a properly made speaker will have its voice coil centered with respect to the top plate width, so "same current will make it move the same distance" in a symmetrical way, so peak movement will be the same, no matter what the signal phase is.

And, being a piston, same movement in air means same pressure wave variation, no matter where that particular peak is moving inwards or outwards.

Specially considering that wave peaks from the guitar will arrive in varying at random fashion, as said before simply because of random picking.

EDIT: also
you were driving the response of the guitar down with the sound from the speakers. Damping the string vibration.

When you flipped it you were reinforcing the string's vibration, adding energy.
Sorry but it simply does not work that way.

Phase is changing all the time, its different because:

a) you are using many frequencies mixed (even if you play a single string, it still has lots of harmonics which are different frequencies mixed in) so

b) wavelengths are not the same so

c) when you are in phase at on frequency, you will be out of phase at another one, and all are coming together because

d) you are playing a musical instrument, not feeding 1kHz sinewave from a generator or some other fixed frequency and to boot,

e) the moment you move 1" (or 1mm) from where you were, phase changes because you are reaching different sections of said waveforms (you are varying distance from instrument to speaker) .

So you can't assume that with a certain speaker wiring phase signals are reaching you out of phase and cancelling all the time, all of them (which is what you are stating) and by flipping speaker wiring phase now all, all the time, all over the room (including close to the speaker) they will be in phase and increase feedback (which is what you are stating).

Nothing personal nor dissing anybody, just plain Physics.
 
Last edited:

Richard Guy

Member
Messages
1,181
Flip the speaker leads on a single combo. You Will hear a difference. It's all about forward firing or rearward firing voice coils on the initial pick attack. Give it a try.
 

Silent Sound

Member
Messages
5,243
Flip the speaker leads on a single combo. You Will hear a difference. It's all about forward firing or rearward firing voice coils on the initial pick attack. Give it a try.
Have a friend set the speaker leads for you and listen to it and tell that friend if it's in phase or out of phase. Make sure your fiend has no way of knowing which is positive and which is negative. Do this several times switching the leads at random and have your friend keep a log of the lead orientation and your impressions of the phase. Afterwards, measure the actual phase and compare the actual results with your perception. This is what's called a double blind study and is the only accurate way to make an assessment like this. The test you described is far to easy to be corrupted by confirmation bias to be useful. So give that a try instead.
 

Geetarpicker

Member
Messages
2,958
I use quite a bit controlled feedback in my playing. My favorite rig for this being my original Trainwreck Express into a Marshall 4x12. That said I often change my playing position, angle, and distance from the cab for this technique. I have a special speaker cable I made that reverses the polarity on one end, and the barrel on that end is insulated for safety. I rarely use this cable but sometimes, if I'm having difficulty grabbing the right notes into control the phase reverse cable does wonders. Personally I haven't noticed any tonal changes with changing the phase on a one speaker setup, but controlled feedback is another matter. With all the variables it comes down to experimentation!
 




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