Speakers in phase when using two amps ?

Dale Hampton · From: Missouri, USA

First of all I would like to say hello to every body. I have been a lurker for quite a few years because I knew That I didn't have any information to offer that couldn't be given by some one better qualified here than me. I have learned so much from the form and felt that I should join and be a member. I have a question about multiple speakers. I know they must be in phase when used with an amplifier, but what about when using two amps? If they are of different makes like Fender Twin and Evans, How would you know if the speakers were in phase and giving you the best sound with the combination of the two amps? I hope I didn't start off with a stupid question, but I would really like to hear what you electronics guys say about this. Please ,if this is a really stupid question, please have mercy on me. Dale

Pete Burak · From: Portland, OR USA

Welcome, Great question.
The way I do it is, with one amp on zero volume, turn the other amp up to a comfortable level.
Then play a low note, and slowly bring the volume of the other amp up from zero.
If the speakers are out of phase, when you reach the point where the volumes are equal, most of the low frequency will disapear.
This is called phase cancellation.
If this is the case, reverse the speaker wires on one speaker.
Now when they are in phase, repeat the test, and there will be no point where the bass drops out.
'Hope that helps.
Pete B.

Jerry Overstreet · From: Louisville Ky

Welcome to the forum Dale. I must admit this is a situation I never thought of. Good question indeed. I don't know the answer, but I wouldn't have expected phase cancellation to be a problem using 2 separate amps each with it's own speaker unless you were only using the power amp sections and pre-amping both from a single common stereo source like an Amp Modeler/Fx unit etc..... but PB's pretty savvy. HMMMM?

Papa Joe Pollick · From: Swanton, Ohio

I read in a Gerald Webber colum that you can listen with both amps facing the same way and then turning one of them around facing away and listen for a difference..If they sound better both facing the same way they're in phase..If they sound better with one turned around then they're out of phase..Never done it so can't say if that works...

billy tam R.I.P. · From: baton rouge, louisiana

Like Jerry I've always been more concerned with out of phase speakers when running two speakers with one amp(ext) or two speakers on a stereo amp. We use to check them in a music store I worked at with a 9 volt battery. putting the 9v on the speaker terminal the cone will either move in or out when touched to the terminal. If they both move in with the 9v the same on both terminals(+ and -) you are ok otherwise swap wires on one speaker. Primitive I know but I am from Louisiana. Very Happy

Thanks,
Billy

Earnest Bovine · From: Los Angeles CA USA

The sort of pedant who would say that ain't ain't a word would point out that speakers can't be out of phase, but may be wired in matching polarity, or in opposite polarity with each other.

If your speakers are hooked up in matching polarity, the sounds from the 2 speakers can be out of phase with each other, if you are half (or 1.5, 2.5 etc) a wavelength further from one speaker than from the other.

OTOH if your speakers are hooked up in opposite polarity, the sounds from the 2 speakers can be out of phase with each other, if you are one (or 2,3, etc) wavelength further from one speaker than from the other.

Audio contains just about every wavelength from a fraction of an inch to several yards. So where e'er you are, it seem to me some of the sounds (some frequencies/wavelengths) will be out of phase, and some in phase, no matter whether the speakers' polarity matches or not. Also, much of the sound you hear is reflected, so what you hear is even more complicated.

Dave Grafe · From: Hudson River Valley NY

Pete Burak has your answer here, even when the speakers are wired for similar polarity not all amps are...

Earnest Bovine · From: Los Angeles CA USA

I didn't mean to imply that polarity makes no difference. The lowest freq on 10 string E9 is about 100Hz, wavelength about 10 feet, so you will definitely notice some low freq cancellation if your pair of speakers is much closer than 10 feet.
Some guys like the sound; e.g. Jay Dee Maness.

Dale Hampton · From: Missouri, USA

Thanks for all the informative replies. I may be wondering about something here that just isn't an issue. I will set up my two amps and reverse the speaker wires in one of them and see if I can notice a change. Dale

Pete Burak · From: Portland, OR USA

Jim Smith · From: Midlothian, TX, USA

I'm pretty sure I read a long time ago that John Hughey used to use two different amps and deliberately wired them out of phase.

Mike Wheeler · From: Delaware, Ohio, USA

If you want a quick and easy way to test for speaker polarity (phase) try this. Play some music through both amps...use a "Y" cable or the like. Set both amps to the same volume and tone settings...doesn't have to be loud, just loud enough to hear.

Now stand in front of one amp and listen to the sound. Now, move to a position right between the two amps. If you notice the low bass disappear, your speakers are out of phase. Just reverse the speaker wires on one of the amps, and test again.

This is especially useful if you are using different amps...say a twin and a NV400. The electronics can cause this phase reversal. The method I described above will reveal any problem with their phase relationship.

The only important factors are to have the volume of the two amps about the same, and use the same music source fed to both amps....so you can easily hear the phase effect (if present).
_________________
Best regards,
Mike

Dale Hampton · From: Missouri, USA

Thanks guys for all the helpful replies. I set my twin reverb and evans FET500 about 4 feet apart. Things I noticed (1) turning one amp backwards did work for checking for cancellation just as did reversing the speaker wires on one amp when both were facing forward. (2)It was true that the cancellation was noticed on low notes and when the volumes were the same. I could only stand in one spot, if I moved left or right, volumes changed. (3) I think I prefer the in phase but I really have no idea how this plays out in getting the sound out in the room, which is why I was curious about this to begin with. I think it is more complex than I can understand so I'm just going to stick with having fun playing. Great forum I'm glad to be a part of it. Dale

Dave Grafe · From: Hudson River Valley NY

Very simply, having your amps in phase projects your sound into the room, having them out of phase acts to cancel it.

Dale Hampton · From: Missouri, USA

Dave, That is what I think also. I have a good friend that a few years ago was playing a jam session . I took my equipment and decided not to play because these pickers were way better than me. My friend playing steel wasn't getting out front very well. I asked him if he wanted to play through my session 400 along with his amp. He did and I know that he did not play any louder on stage from where he was setting, but it was unreal how his sound was filling the room.This I heard with my own ears. I just wish I could know what I sound like out in the room that I am playing. Dale

Brad Sarno · From: St. Louis, MO USA

Important point to mention how different amps will electronically have different polarities at the speaker. You could have a Webb and a Twin side by side and you may or may not be in phase from amp to amp. You could use the "normal" channel of the Twin and it will be the opposite polarity as the reverb channel. Once of those Fender channels will be in phase with the Webb and the other won't.

Ideally you get your two amps as you like them, and if there's a polarity issue, simply reverse the wires at ONE of the amps. JBL's and Black Widows and others fortunately let you release the wire connections with the push of a button instead of soldering.

The way I tell phase/polarity is to basically put your head right between the two amps and have them pretty much the same volume. The out-of-phase sound will make your ears and brain tweak and it causes a dizzying effect and the sound appears to come from somewhere other than the point between the amps. When in phase, the sound appears to come from a phantom center point between the amps, right down the middle. That's what you want unless you're Weldon or JayDee who dig that phase-cancelled bass effect as it gives a wide, stereo-like effect and removes un-needed bass energy from the steel sound.

B

Dale Hampton · From: Missouri, USA

Brad thanks for the info. Just a note on the out of phase of the two twin inputs. I made a mod to mine by moving one wire that put reverb on both channels. By doing this the two channels are in phase and I now can daisy chain the two channels together and it adds a little more body to the sound. kinda like adding the second amp. I got to give Ken Fox credit for bringing this mod to my attention. Dale

Dale Hampton · From: Missouri, USA

sorry double post

Forum Index > Electronics		Next oldest topic :: Next newest topic