Speaker Phase

[Dr-Joned]

[/quote]
I don't know if that is possible. How could you make the strings sync up coming from different sources (players)? I don't think you can tell that two players are out of phase from each other they would have to be in perfect unison. Think of the nightmares! Fender pickups flipped phase every 5 years or so. Not many amps are in phase in to out and most flip the phase with effects loops or gain channels. How could you even diagnose you and he were out of phase? I would think you would need to pull metal away from the guitar pickup pole piece and see which way the cone moves.[/quote]

I think everyone is over-analyzing the simplistic. The effect of bass cancellation is very noticible.

As far as my example of 2 guitarist, it was noticible when hitting an open E chord. The sound was simply "hollow", until I changed the phase of my amp.

I have installed and repaired professional sound for many years and have seen first-hand the issues that phase can cause. It normally stems from a crossed pair of wires within the system. It is so weird, the sound that can come from cross cancellation of fullrange drivers as well. I remember a particular system that utilized Bose speakers. The first cardinal sin is close proximity of like speakers. It is OK to stack the 802 units, as they were designed for that.

I'm sure that some of the recording engineers can attest to switching phase in the studio.

[Reeltarded]

I'm sure that some of the recording engineers can attest to switching phase in the studio.[/quote]


It's paramount.

[Richie]

As far as speaker movement goes, there is no cone pushing out or cone sucking in. If you hit an open A, the cone moves at 110 cycles per second. It may start by pushing out first, but will retract on the downsweep of the cycle.

I disagree with this. Do the battery test and see which direction the speakers move. They will move in the direction they are wired. When you hit a note, watch the speaker see the "direction" it moves. It does make a difference as noted by others. And depends on the cab and direction the speakers are wired.

[Structo]

We can argue theory and hypothesis all day long.

The best thing to do is try it for yourself.

You can either make a speaker cable that reverses the polarity or just switch the clip leads on the speakers.

I will be the first to agree that with one amp/ speaker in a smaller room the result is subtle but it is there.
I can only imagine on a larger scale what the difference would be.

[Lynxtrap]

I have installed and repaired professional sound for many years and have seen first-hand the issues that phase can cause. It normally stems from a crossed pair of wires within the system. It is so weird, the sound that can come from cross cancellation of fullrange drivers as well. I remember a particular system that utilized Bose speakers. The first cardinal sin is close proximity of like speakers. It is OK to stack the 802 units, as they were designed for that.

I'm sure that some of the recording engineers can attest to switching phase in the studio.

Nobody is denying that phase cancellation exists. All kinds of issues with phase occur all the time when dealing with audio. The question here, the way I understood it, was phase cancellation with one input source and one output source.
That would be like a recording engineer switching phase when recording with one mic in mono.
I think Martin summed up this discussion pretty well

[timford]

Lots of confusing stuff flying around here.

My understanding is that the initial point was that some people appear to be able to hear the difference between the speaker cone's initial excursion being either out or in.

Bit that confuses me is where does the guitar phase come into it? If hitting a note up or down changed the speaker cones initial excursion then left handed guitarists would need their pickups wired differently to sound the same as right handed guitarists(and finger pickers and reggae?). When the AC signal travels through the tubes the phase is most often changed. Different frequencies have their phases influenced by capacitors and inductors. A push pull amp has the phase inverter that then splits the signal into a negative and positive for the pairs of tubes. Isn't the signal that goes to the speaker a culmination of this, as the amp pushes and pulls, tube on and off?

It seems to me that a test would be best done with a single (probably low) frequency tone from a generator, through the amplifier to a speaker (so as not to confuse the listener with various frequencies and harmonics from the guitar, even though the tubes and electronics will provide some of these itself), and then test it to see which direction it moves initially. Try the other speaker phase (easy on a matchless c30 due to the phase switch) and see if there is a difference in your opinion. Then get somebody else to switch phases for you in a blind test.

My guess from what you guys have said, is that it would be more likely to be apparent in a closed back cabinet where speaker movement is affected by limited volume of air (maybe more so if it is damped with foam). In an open back cabinet? A bit more difficult with slight acoustic phase cancellations, but sounds like there is a difference with the fender amps. I thinking, no wonder I can't make anything sound good..... What happens with a SE amp? And PP closer to class A?

I've got no idea but will try it for myself. I ain't got dog ears. The dog howls.

If I'm out of line just tell me to shut up and get back in my box. I've still got my learner plates on.

[timford]

Forget half of that. The primary tone is the one that everything else rides upon. One tube does most of one phase, the other does the opposite phase. Doesn't matter about class A and SE. Just where the primary note phase sits at the end of it's journey through the amp, and which way it initially kicks the speaker cone.

Does the pickup magnet work on distance from the magnet of the string and then fluctuations in the magnetic field due to string vibration? Is it initially "up and down" in the direction of the strike and then into 3 dimensions. But it's the winding of the pickup that makes it a positive or negative signal, yes? Presume the neck pickup would give the best signal with least smaller order harmonics, but does the pickup of choice depend on the string being played open versus up high on the neck? Would the phase then be affected by where the pick is striking relative to the nodes (if a node falls between the strike and the pickup)?




I might be best off deleting my posts and leaving this to the bigger and brighter and more learn-ed minds of the world.

[timford]

I'll have to edit this out for you tomorrow. I'm running late.

[LeftyStrat]

I might be best off deleting my posts and starting again when I've had time to think about it.

No, I think we're all thinking out loud here a bit. I do plan to keep an open mind and experiment with this. I'm especially intrigued about John's statements, and what Martin describes as the second case, one in which the speaker in a combo interacts with the circuitry.

I'm cooking turkey right now, but plan on doing a listening test tomorrow to see if I can reproduce this.

[Firestorm]

Here's a little unscientific scientific data:

The fixed field from the back of a P12R begins to deflect the needle of a compass when it is 15 inches away (I thought that was a surprisingly large distance, btw). When a 9V battery is connected to the speaker terminals, the amount of deflection increases or decreases depending on the battery's polarity. (Note to home experimenters: do not connect a speaker to a battery for more than a second or so; speakers do not like DC).

So what does this tell us? The induced magnetic field of the voice coil is able to modulate the fixed field of the speaker's permanent magnet. The effect seems most pronounced close to the voice coil's Z-axis (pointing out straight out the back and front) where the coil's field strength is strongest.

With an AC signal, the voice coil's field will vary with frequency and it will have a phase. So if an electron tube is suspended within the field behind the speaker, there should be some critical distance where this modulated field enhances or detracts from tube performance depending on the phase of the signal. This is probably most pronounced in a beam tetrode or a pentode (in fact it may not even happen in a triode), because they rely on a semi-delicately balanced space charge called the "virtual cathode" which is likely easier to affect than high-velocity electrons themselves.

At any rate, this suggests that there may something real and physical to claims that speaker phase is important to the tone of certain amps.

[Lynxtrap]

I'm cooking turkey right now, but plan on doing a listening test tomorrow to see if I can reproduce this.

Please report how the turkey was
When doing a test, it would be best to do one with the guitar in the same room as the speaker, another with the speaker in another room, and a third with a combo in another room. That way we could test all the theories here.

[martin manning]

The fixed field from the back of a P12R begins to deflect the needle of a compass when it is 15 inches away... When a 9V battery is connected to the speaker terminals, the amount of deflection increases or decreases depending on the battery's polarity. ... this suggests that there may something real and physical to claims that speaker phase is important to the tone of certain amps.

Excellent! I'd say this suggests that there is another real and physical effect to speaker phase (that I had discounted). I guess not only the proximity but also the orientation of tubes placed close to the speaker would be important, then.

[Reeltarded]

It's not just imagination. It really matters.

Head on or off the cabinet makes a huge difference for most any amp, and phase of the wavefront matters when bashing a detector.

[LeftyStrat]

Okay, count me in as a believer for phase affecting a combo amp. I haven't tried the other cases yet, but I took a small combo that is loosely based on a Matchless Spitfire, with a Weber AlNiCo Signature 10S.

I was going to get all scientific and build a switch and have someone else flip it, but decided I'd just play a little and then switch the speaker wires, then go further depending on the results.

The difference was very apparent. With the phase reversed, I lost midrange and lower bass, and sort of an odd funky comb filter effect was obvious.

It seemed to emphasize all the wrong frequencies, tinny but with boost in mid-bass that made it seem honky or ratty.

It didn't seem to matter how close or far I was from the amp.

So there is definitely some kind of coupling going on between the speaker and electronics. It remains to be discovered whether this is electromagnetic or mechanical or both.

Now I didn't bother to check that the one I liked was speaker pushing out vs speaker pulling in. So all this proves is that changing the phase of the speaker in a combo will affect the tone.

What would be interesting to see is a spectrum analyzer plot comparing the two.

[ampdoc1]

I remember YEARS ago that Audio Magazine tested for determining ABSOLUTE phase using high end (for the time) solid state amplifiers. Their conclusion was that it was not gererally discernable.

I think one factor here has not been discussed! While the absolute phase changes as the signal goes thru the amp stages, the actual phase changes somewhat thru each capacitor in line. Depending on the caps and their placement there can be a lot pf phsase shift from the first to final stages.

My guess would be that amplifiers that "just happen" to have closely matching input and output phases would be more likely to have more sustains,..etc. That being said, probably the best idea would be to have a phase shift switch on the speaker cab to see what works well in a given enviroment.

a'doc1