Reverse Polarity Speaker Cabinet Wiring

[George Redmon]

I just purchsed a new Two-Rock Studio Signature Head.

https://www.humbuckermusic.com/collecti ... silverface

They say it's wired "Out Of Phase" apparently? I'm building a speaker cable for my new Two~Rock head, and was wondering if i'm suppose to be building the cable out of phase? Apparently Two ~Rock sells a speaker cable out of phase. I didn't know Fender reverb amps were also built this way apparsntly? Nothing to worry about here right gang? Something more to confuse us with. So just build a standard phase speaker cable? Any input is so appreciated.

Here is their article about it?

https://shop.two-rock.com/products/two- ... 8001206369

[Jeff Highland]

It has the potential to reduce acoustic feedback in the lower frequencies(which is why you see a Phase switch on acoustic preamps) That would have a small effect on volume of low frequencies.

[Jim Kennedy]

Wiring for speakers is polarity sensitive, and is normally wired positive to positive, negative to negative. A quarter inch speaker cable is normally wired as tip is positive, and sleeve is negative. From end to to end it is normally wired tip to tip, and sleeve to sleeve. If you want to reverse the polarity, simply wire one end of the cable opposite to the other. Tip of one end to the sleeve of the other end. This will "reverse the polarity" of one of your speakers, putting them "out of phase." The difference in sound will be noticeable. On my amp there is a noticeable thinness to the sound. This will only happen if you use both speakers with your amp. It will make no difference when using only one speaker. I read the articles you posted. It appears the cable is used to revers polarity, and the head is not wired that way, so you need a "reverse polarity cable" to get the reverse polarity effect. Hope this helps.

[Jeff Highland]

Yes if you have more than one speaker, phase becomes important. Two rock seems to be suggesting a small difference with one speaker

[George Biner]

Sounds like they are saying that in reverb amps, the extra reverb stage commonly results in a polarity inversion for that path (because the extra gain stage inverts the signal) -- so this cable gives you a way to correct the phase at the output -- if you are only using one amp in isolation, I don't think it matters -- but if you ever use two simultaneously, they would be out of phase with each other and the low end will suffer. Or say you are playing the amp and miking it at the same time. Plus there is maybe something to be said for keeping all gear on the correct polarity and knowing what it is.

Note: "polarity" is a phase shift of 180 degrees (or an inverting of the signal) and should not be called just "phase".

[ajm]

The Two Rock write up is confusing and seems to be lacking some detail, or needs to be re-worded for clarification.
I really struggle trying to figure out what they're trying to say.
They may also be trying to cover more than one topic without clearly differentiating between them.

However, I'll take a stab at it.

Some of their amps are in phase, input to output. Some of them are not. This is understandable.
If you use one of each, and the cabinets/speakers are wired up "normal" (+ to +, - to -), your overall tone will be thinner/weaker.
If you reversed the wiring on one cabinet only, the problem should be solved.
This is easy to do on combo amps if the speaker(s) is connected with lugs on the terminals. Just pull them off and reverse them.
With a separate speaker cabinet, especially a closed back one, this is not so easy. Using this cable makes it easy and is all you need to do. The cable essentially swaps the lugs for you.
Also, if you use one of their amps, and another amp by any other maker, and they are out of phase, you will also have this weak/thin tone problem.

With regards to a single amp set up, with a single speaker (combo or head/cab, it doesn't matter) I have never heard of a difference in sound by reversing the speaker leads to in or out of phase.
Granted, I don't know everything, but I'm skeptical and would actually need to experience this test in person before I'm a believer.

Also, their comment on a Fender amp:
"Take any Fender amp with reverb in it (Deluxe Reverb, Super Reverb, Twin Reverb, Bandmaster Reverb etc.) if you plug into the NORMAL channel the amp is in phase, if you plug into the VIBRATO (reverb) channel it is out of phase."

First of all, it should be TWO CHANNEL Fender amp, not ANY Fender amp.
Then, if I understand them:
- If you plug into one channel, then
- jumper a cable to the other channel, then
- turn the reverb/trem off, then
- set the volume and tone controls the same on both channels,
the resulting sound should be really thin and weak.
You would be mixing two identical signals that are out of phase with each other, and they would cancel out.
I do not have a two channel Fender amp.
If somebody here has one you can try it and report back.

Note that if you are using an A/B switch box to switch between the two channels, only one at a time, you should not hear a problem either.

My gut feel tells me that if you are only running a single amp, you have nothing to worry about.
Like I said, until I see/hear this in person, I'm moving on.

And, if you can afford two of their amps, I wish I had your problems.

[Jeff Highland]

You would probably notice the difference with a single speaker If you were playing at high volume in close proximity especially with an acoustic instrument. In phase the speaker will drive the strings increasing volume and sustain especially low frequencies. Out of phase will reduce this effect, which is why it is used to counter feedback problems.
Obviously this makes no difference with a purely electronic source such as a keyboard.

[Steve Kimock]

The Two Rock write up is confusing and seems to be lacking some detail, or needs to be re-worded for clarification.
I really struggle trying to figure out what they're trying to say.
They may also be trying to cover more than one topic without clearly differentiating between them.

However, I'll take a stab at it.

Some of their amps are in phase, input to output. Some of them are not. This is understandable.
If you use one of each, and the cabinets/speakers are wired up "normal" (+ to +, - to -), your overall tone will be thinner/weaker.
If you reversed the wiring on one cabinet only, the problem should be solved.
This is easy to do on combo amps if the speaker(s) is connected with lugs on the terminals. Just pull them off and reverse them.
With a separate speaker cabinet, especially a closed back one, this is not so easy. Using this cable makes it easy and is all you need to do. The cable essentially swaps the lugs for you.
Also, if you use one of their amps, and another amp by any other maker, and they are out of phase, you will also have this weak/thin tone problem.

With regards to a single amp set up, with a single speaker (combo or head/cab, it doesn't matter) I have never heard of a difference in sound by reversing the speaker leads to in or out of phase.
Granted, I don't know everything, but I'm skeptical and would actually need to experience this test in person before I'm a believer.

Also, their comment on a Fender amp:
"Take any Fender amp with reverb in it (Deluxe Reverb, Super Reverb, Twin Reverb, Bandmaster Reverb etc.) if you plug into the NORMAL channel the amp is in phase, if you plug into the VIBRATO (reverb) channel it is out of phase."

First of all, it should be TWO CHANNEL Fender amp, not ANY Fender amp.
Then, if I understand them:
- If you plug into one channel, then
- jumper a cable to the other channel, then
- turn the reverb/trem off, then
- set the volume and tone controls the same on both channels,
the resulting sound should be really thin and weak.
You would be mixing two identical signals that are out of phase with each other, and they would cancel out.
I do not have a two channel Fender amp.
If somebody here has one you can try it and report back.

Note that if you are using an A/B switch box to switch between the two channels, only one at a time, you should not hear a problem either.

My gut feel tells me that if you are only running a single amp, you have nothing to worry about.
Like I said, until I see/hear this in person, I'm moving on.

And, if you can afford two of their amps, I wish I had your problems.

Hi.
The idea with the reverse speaker cable is mostly consistent performance across the product line for comparison purposes.
There’s enough of a diff with the guitar and amp in a room together at volume, that you might notice it and express preference for one amp or the other when it’s just a polarity issue.
So, eliminate the variable just in case.

The Fender amp thing is pretty cut and dried for the black and silver face reverb amps at least; those all reverse phase between reverb and normal channels.
The non-reverb amps, it depends what amp it is.
Blackface Bassman, same both channels.
Blonde Bassman, reverse.
Same deal for the brown amps with the harmonic trem, those also reverse.
But otherwise, it’s a safe bet the non-reverb Fenders are the same polarity both channels.
Probably a safer bet not to assume : )

Positive pulse at the input equals positive pulse at the output is a foundational practice for good audio, no reason not to observe it.

[Thomas Stone]

An acoustic guitar is more likely to suffer feedback when the positive pressure wave from the speaker hits the soundboard as it is moving inward, because then the high pressure makes it move even further.

If you reverse the phase of the speaker, either with a phase switch, a cable, or by swapping the + and - leads, the tendency to feed back will be reduced.

But all this is all true only at one frequency, and only if you are standing at the same distance from the speaker. You could also reduce feedback by moving one half wavelength away from or toward the speaker.

For example, say you were getting feedback with your 6-stringer's low A string, at 55 Hz. The wavelength of a 55 Hz pressure wave is about 20 feet, so moving 10 feet away from or toward the speaker would be equivalent to a phase shift.

Oversimplified, but you get the idea.

[Marco Schouten]

You would probably notice the difference with a single speaker If you were playing at high volume in close proximity especially with an acoustic instrument. In phase the speaker will drive the strings increasing volume and sustain especially low frequencies. Out of phase will reduce this effect, which is why it is used to counter feedback problems.
Obviously this makes no difference with a purely electronic source such as a keyboard.

That doesn't make sense. The wavelength of an audio frequency at 440 Hz is 78.41 cm. You would have to measure the distance from your speaker to your guitar and place it exactly at x times 78.41 cm for it to theoretically work. However, every frequency has a different wavelength, so that will never work out.

[Steve Kimock]

You would probably notice the difference with a single speaker If you were playing at high volume in close proximity especially with an acoustic instrument. In phase the speaker will drive the strings increasing volume and sustain especially low frequencies. Out of phase will reduce this effect, which is why it is used to counter feedback problems.
Obviously this makes no difference with a purely electronic source such as a keyboard.

That doesn't make sense. The wavelength of an audio frequency at 440 Hz is 78.41 cm. You would have to measure the distance from your speaker to your guitar and place it exactly at x times 78.41 cm for it to theoretically work. However, every frequency has a different wavelength, so that will never work out.

The wavelength/distance stuff is irrelevant.
There’ll just be a volume threshold sufficient to produce feedback at whatever frequency is most susceptible.
At that point if you flip anything 180 degrees, what was previously a peak becomes a dip,
That’s exactly how the feedback suppression stuff on the acoustic guitars works, noise canceling headphones, etc.
You don’t need to know the frequency, you just need to take away the plus sign and replace it with a minus sign, and whatever was previously being reinforced will now be canceled.

Works good!

Anyway, acoustical coupling is broad, loose, fairly sloppy, and overtone series based,
It’s very difficult to drive an in -phase fundamental without also driving all its overtones, and it’s impossible to drive an out-of-phase signal without canceling the fundamental and splitting it into its overtones.

Point being you can’t really expect to zero in on a single specific frequency and distance relationship in a real life thinking that frequency and that distance were the only values being driven.
It’s gotta start somewhere, feedback, and it does, but it’s broad.

Too be clear about the “very difficult” part of coupling a specific frequency, it’s the kind of thing you get when you jam the headstock of an archtop into the speaker cabinet as hard as you can and hunt for that one note really loud,
Literally direct mechanical coupling will do it, but thru the air?
Air just doesn’t couple that tightly.