Speaker Wiring

[Colossal]

OK, wait. Consider phase vs polarity. In the above example, talking about the physical length of sound waves, a PHASE switch would be helpful. I have such a switch on my subwoofer for my studio monitors. But for guitar cabs, we're talking about a POLARITY switch, which will not affect the physical position of nodes and antinodes in a room.

Check out additive and subtractive polarity of a single phase transformer and its effect on phase angle.

[xtian]

Thanks, Dave, this is a new concept for me. You’re saying the polarity of the speaker affects the signal phase?

[Colossal]

Thanks, Dave, this is a new concept for me. You’re saying the polarity of the speaker affects the signal phase?

Yes. Consider the primary and secondary windings for a single ended, step down transformer. Let's call the start of the high voltage primary H1 and the end, H2. The start of the low voltage secondary will be X1 and the end, X2. Additive and subtractive polarity refer to the relative position of the high voltage primaries with respect to the low voltage secondaries. H1 is always shown on a diagram as the upper left side of the transformer and usually denoted with a dot.

In the subtractive position (step down), H1 "mirrors" X1, and H2 mirrors X2. Flux "flows" in one direction in the core and we got ourselves a transformer. In this position, if you apply a voltage across the primary and measure the voltage measured from X1 to H1, Vsub = Vprim - Vsec and is less than the voltage applied to the primary. In the additive position, and in the case where we flip the so-called phase switch (really polarity) on the cabinet, now H1 is "directly across from" X2 and H2 now faces X1; the secondary is now flipped with respect to the primary, Vadd = Vprim + Vsec and the phase angle of the voltage waveform is flipped 180 degrees. The voltage measured from X1 to X2 is still the same in either position, however, now X1 is "positive", but the speaker sees (-) because X1 is now flipped.

In the subtractive position, the windings orient in the same way (both either counterclockwise or clockwise, depending on how they were wound). In the additive position, the direction of current in one is counterclockwise and the other is clockwise. If the windings were exactly equal, in the additive position, there would be no flux in the core; it would cancel completely. But since the primary has much higher turns than the secondary(ies), only a portion of the magnetic field is canceled.

[romberg]

OK, wait. Consider phase vs polarity. In the above example, talking about the physical length of sound waves, a PHASE switch would be helpful. I have such a switch on my subwoofer for my studio monitors. But for guitar cabs, we're talking about a POLARITY switch, which will not affect the physical position of nodes and antinodes in a room.

Yea. I don't think that flipping the polarity of the speakers would change much about standing waves in a room. However, It does make sense to me that flipping the polarity would make a difference in the relationship between the vibrating string and the speaker. Given a fixed position of the guitar string and speaker some notes on the guitar would be in phase when the sound wave from the speaker hits the string (increasing sustain/feedback) and some would be out of phase. In other words when the string and pickup are producing a positive signal then the air pressure from the speaker is either reinforcing or damping this. This is independent of the standing waves in any given room.

So, flipping the phase could have a noticeable effect if the guitar and speaker are in the same room. I would guess it would have no effect otherwise (or I'm missing something .

Mike

[xtian]

I understand @Colossal, above, to be saying that speaker polarity can affect the reflected impedance on the OT...is that right? I still can't grasp the difference an amp sees if a single speaker coil is wired one way or the other.

[Scumback Speakers]

I understand @Colossal, above, to be saying that speaker polarity can affect the reflected impedance on the OT...is that right? I still can't grasp the difference an amp sees if a single speaker coil is wired one way or the other.

Oversimplified answer: You want the phase to be correct so that the speaker moves forward when you pluck the stings. If it moves backward it's got less energy, less volume and it sounds different. At this point you need to know which way sounds better with your output tranny, if you don't know what the phase orientation is (i.e. the Dumble reverse phase thing or standard).

With a 1x12 cab, wired one way it will sound better, stronger and louder, wired the other way will be a little less volume, thinner and weaker. At least that's the way it worked with my single ended amps, which HAD himself told me to test to see which way I liked the sound in my 1x12 combos better.

Not very technical, I know, but Dumble practically spoke in tongues and ethereal phrased sometimes about electrical tone responses that left me going "Howard, KISS! Keep It Simple Stupid!"

He didn't appreciate some of my lay person logic questions at times. That was one of them. LOL

[norburybrook]

I understand @Colossal, above, to be saying that speaker polarity can affect the reflected impedance on the OT...is that right? I still can't grasp the difference an amp sees if a single speaker coil is wired one way or the other.

Oversimplified answer: You want the phase to be correct so that the speaker moves forward when you pluck the stings. If it moves backward it's got less energy, less volume and it sounds different. At this point you need to know which way sounds better with your output tranny, if you don't know what the phase orientation is (i.e. the Dumble reverse phase thing or standard).

With a 1x12 cab, wired one way it will sound better, stronger and louder, wired the other way will be a little less volume, thinner and weaker. At least that's the way it worked with my single ended amps, which HAD himself told me to test to see which way I liked the sound in my 1x12 combos better.

Not very technical, I know, but Dumble practically spoke in tongues and ethereal phrased sometimes about electrical tone responses that left me going "Howard, KISS! Keep It Simple Stupid!"

He didn't appreciate some of my lay person logic questions at times. That was one of them. LOL

exactly JIm, and a point I made earlier in the thread. That's why when you stand in front of a 4x12 with a loud tube amp you get a push of air in the back oh your pants when you hit a damped low note, you've got a sealed cab and 4 speaker pushing a lot of air at you.

I'll reiterate though; if you've a classic fender 2x12 very open backed combo then having the sound come out the back first isn't a bad thing, but on a sealed cab I think it has to be in absolute phase with the guitar string pluck.

M

[pdf64]

Considering the vast array and almost infinite variety of fx pedals available these days, and the random nature of any particular rigs polarity, surely if overall signal / system polarity made any audibly discernible difference, then a polarity flip pedal would be a common thing?

It seems pretty clunky to me dealing with absolute signal polarity at speaker level. Or have I got this wrong, is the issue (for some reason) is purely regarding amp - speaker polarity? (In which case every 2 channel BF Fender's reverb channel is wonky).
If absolute signal polarity matters then build a polarity reverse pedal and flip it to best effect; may even make $$$ selling it to others.
As every rig configuration may differ at a system level, eg depending on the guitar / pickup used, what pedal is engaged, what channel selected, whether an fx loop is engaged etc.
ie there's a random number of polarity flips before the signal gets to the speaker.

Would a polarity flip pedal pass EVH's 'Is it on?' test though?

Why this obsessing with absolute polarity solely at the OT secondary circuit, when it's a system thing?

When viewed on a scope, some of my guitars seem to generate a larger negative going peak when a string is picked; if they are to be regarded as polarity wonky then getting the rest of the system 'right' isn't going to achieve the desired goal. And only a polarity flip pedal would reveal that 'issue'.

What's 'correct' here anyway? For a regular listener, does an acoustic guitar create a compression or rarefaction initial attack pressure wave when a string is plucked? How about when a snare drum is hit? Shouldn't a drummer think his kick drum sounds sucky when he plays it? And is any of that relevant to discussion regarding electric guitar?

[sluckey]

When viewed on a scope, some of my guitars seem to generate a larger negative going peak when a string is picked; if they are to be regarded as polarity wonky then getting the rest of the system 'right' isn't going to achieve the desired goal. And only a polarity flip pedal would reveal that 'issue'.

The scope display is totally dependent on how the triggering is configured. Trigger on a positive slope and the displayed waveform will swing positive first. Trigger on the negative slope and the displayed waveform will swing negative first.

[Scumback Speakers]

exactly JIm, and a point I made earlier in the thread. That's why when you stand in front of a 4x12 with a loud tube amp you get a push of air in the back oh your pants when you hit a damped low note, you've got a sealed cab and 4 speaker pushing a lot of air at you.

I'll reiterate though; if you've a classic fender 2x12 very open backed combo then having the sound come out the back first isn't a bad thing, but on a sealed cab I think it has to be in absolute phase with the guitar string pluck.

M

When the speakers are wired incorrectly, you'll notice that difference if you compare back to back to a correctly wired "in phase" cab. That pant legs flapping in the 4x12 breeze is a real thing.