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re-wire Bipole to Dipole?

DANRB

Established Member
Hi thinking of the possibility of rewiring a current bipole speaker into dipole.

Seeing as some speakers come with a switch to be able to do this I am thinking cabinet construction only plays a small part.

Anyone ever tried this?

I will be doing this on a pair of Mission 78DS that have already been taken apart to repaint and recloth in white so know access to the wiring is easy.

So anyone think this will work?
 

BlueWizard

Distinguished Member
I think the switch is probably the best idea. Though you want to make sure you have a good quality slide switch. By that I don't mean the adjuster know slides, but that the contacts slide. Also, you want a switch that is break before make, meaning the old connection disconnect before the new connection is made.

I would suggest that you leave the front firing speaker (facing the front of the room) in standard positive phase wiring. Then use the switch to control the wiring of the rear facing speaker.

When the speaker are electrically in-phase, meaning both (+) terminals of the speakers are wired to the (+) terminal of the amp, they are mechanically out of phase.

When the speakers are electrically out of phase, they are mechanically in phase. Electrically out of phase, meaning the front speaker is wire amp(+) to Speaker(+), and the rear facing speaker is wired amp(+) to speaker(-).

Sadly, I can never remember which is referred to as Dipole and which is referred to as Bipole, even though I've looked it up several times.

If nothing else, put a switch in temporarily, so you can easily try it both ways. Once you find out which you like better, you could then permanently wire the speaker in a fixed configuration.

Just a few thoughts.

Steve/bluewizard
 

deckingman

Prominent Member
Steve,

That means you will "be in doubt", or spelt another way B in Dout. (Bi-pole = in phase, Di-pole = out of phase). Not perfect but a kind of way to remember.
 

BlueWizard

Distinguished Member
Steve,

That means you will "be in doubt", or spelt another way B in Dout. (Bi-pole = in phase, Di-pole = out of phase). Not perfect but a kind of way to remember.

So, is that electricaly B=IN phase and D=OUT, or is it mechanical? I suspect it refers to the electrical wiring.

Admittedly, it took me a while to figure out what you were trying to say, but it eventually sunk in; good mnemonic.

Steve/bluewizard
 

deckingman

Prominent Member
So, is that electricaly B=IN phase and D=OUT, or is it mechanical? I suspect it refers to the electrical wiring.

Admittedly, it took me a while to figure out what you were trying to say, but it eventually sunk in; good mnemonic.

Steve/bluewizard

Steve,

My understanding is this. If one drive unit cone goes out while the other cone goes in, then they are considered to be working out of phase and hence di-pole. If both cones go in and out together, then they are considered to be working in phase and hence bi-pole.
 

DANRB

Established Member
Seeing as alot of the true dipole speakers only have on midbass driver do you think it wouls be best in this situation to onlt reverse the phase of 1 of the tweeters?

Dan
 

deckingman

Prominent Member
Seeing as alot of the true dipole speakers only have on midbass driver do you think it wouls be best in this situation to onlt reverse the phase of 1 of the tweeters?

Dan

IMO the tweeters won't make any difference. Due to the short wavelengths, you won't be able to detect whether they are in phase or out of phase.
 

DANRB

Established Member
IMO the tweeters won't make any difference. Due to the short wavelengths, you won't be able to detect whether they are in phase or out of phase.

If this is the case, how are the likes of Monitor audio doing it in thier RSFX/RXFX range as there are only 2 parts that can be out of pahse on these and thats the tweeters.....

There is only 1 main driver so that can't be out of phase.

Dan
 

BlueWizard

Distinguished Member
There are several configurations of speaker for Di/Bi-pole speakers.

- the speakers have two complete sets of drivers, meaning two woofers and two tweeters with one set facing forward and one set facing rearward. In this case, I suspect the speakers are treated as sets. One full set is in phase with itself, and the other full set is either in phase or out of phase with the other.

- one tweeter and two midbass. The tweeter and one of the midbass are alway in phase, and the remaining midbass is either electrically in phase or out of phase with the other two (T+M).

- one midbass and two tweeters. Like above, one tweeter and one midbass are always in phase, and the remaining midbass is either in-phase or out of phase with the other two (T+M).

I suspect in the case where there are three drivers, the center and the forward facing are in phase, and it is the phase of the rear facing that is changed to determine Bi-pole or Di-pole.

I don't know if that answers your question, because I'm not quite sure what the question was.


deckingman

"If one drive unit cone goes out while the other cone goes in, then they are considered to be working out of phase and hence di-pole. If both cones go in and out together, then they are considered to be working in phase and hence bi-pole."

So, we could modify the mnemonic to read -

Mechanically Be in Doubt.

B=IN
D=OUT

Refers to the movement of the cone, and not the electrical wiring.

'Mechanically be in doubt'; seems just as easy to remember. And now that I have this, I will actually be able to remember it. Thanks.

Steve/bluewizard
 
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bobbymax

Prominent Member
Wish I understood what you guys are talking about.:confused:

All I can say is.... I've tried both and prefer the sound on Bi-pole, but still don't know what in theory it does, compared to di-pole :rolleyes:
 

BlueWizard

Distinguished Member
I'll give this a shot here.

Lets picture a Di/Bi-pole speaker mounted on the side of a room. For simplicity, we will say that the speaker has two full range drivers. While the speakers are usually at an angle, again from simplicity, we will say one driver faces forward, and the other driver faces rearward.

Can you picture that?

Now, a positive going electrical pulse enters the speaker, and moves both drivers forward away from the magnet structure. These speakers are electrically in-phase, since a positive voltage results in forward movement of the speaker.

But, let's look at that movement in relation to the room. Since one driver faces forward, and the other faces rearward, they are moving in the opposite direction. Relative to the drivers, the cones are both moving forward. But relative to the room, one cone moves toward the front of the room and the other moves toward the back of the room. They, relative to the room, are moving in the opposite direction.

They are electrically in-phase, but mechanically out-of-phase. This is a Di-pole.

If we reverse wire the back speaker, so the amp(+) connection goes to the (-) of the rear speaker. We now have drivers that are mechanically in-phase, but electrically out of phase.

When a positive voltage is applied, the front speaker moves forward away from the magnet, but the rear speaker moves backwards toward the magnet.

Now, again stepping back and considering the whole room, we see that the speaker are actually both moving in the same direction. A positive voltage moves both driver cones toward the front of the room.

Again, they mechanically move in the same direction, but since they face in the opposite directions, they have to be wired opposite.

EDITED: The corrected Phrase should be - Electrically, Be In Doubt. Mechanically IN-Phase, and electrically OUT of Phase would be DI-POLE.

ERROR: Mechanically in-phase, but electrically out-of-phase. These are Bi-pole speakers.

Now, it is hard to explain, but again, simply picture the movement of each cone relative to the room.

In the Di-pole configuration, the front speaker move forward toward the front of the room, and the rear facing speaker moves toward the rear of the room.

In the Bi-pole, the front driver moves toward the front of the room, and so does the rear facing speaker. They both move in the same physical direction.

Which is right? Well, both and neither. Each wiring method has its own advantages and disadvantages. It is up to you to determine which configuration you like best, and that is also why many speakers like this come with a switch, so you can have either configuration. Try both, and keep the one that sounds best.

A simple diagram would go a long way to explaining what I mean, but I'm not that good in graphics programs, so it would take some time to draw out.

steve/bluewizard
 
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BlueWizard

Distinguished Member
One picture is worth a thousand words.

Steve/bluewizard

Here is the corrected Diagram, as verified by several source.

bi-di-pole-1.jpg


Does anyone know how I can delete the other diagram from this post?

Here is an explanation from DeckingMan that explains this in the simplest possible way -

""If the cones move Out together,... they are Bi-pole. If one moves Out while the other moves In, ... they are Di-pole. ..."

You can remember that, or picture my diagram along with the phase - Electrically, Be In Doubt.

Which is a pneumonic for -

Electrically -
B=In phase
D=Out of phase.

EDITED: Please ignore the diagram below, as it seems it is in error and says exactly the opposite of what it should. The top item should be Bi-Pole and the bottom should be Di-pole. Once I have the diagram corrected, I will post a new version.
 

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  • Bi-Di-Pole.jpg
    Bi-Di-Pole.jpg
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deckingman

Prominent Member
Wish I understood what you guys are talking about.:confused:

All I can say is.... I've tried both and prefer the sound on Bi-pole, but still don't know what in theory it does, compared to di-pole :rolleyes:

What Steve has said but also, you might like to take a gander at this What are Direct, Bipole and Dipole Surround Sound Speakers? - Overview of Surround Sound Speaker Types - Direct, Bipole and Dipole Speakers

There is no "right or wrong" and, as you have discovered, it comes down to a matter of personal preference. To complicate things even further, there are also tri-pole and one manufacturer has a quadropole, but these are all variations on the same thing.
 

deckingman

Prominent Member
If this is the case, how are the likes of Monitor audio doing it in thier RSFX/RXFX range as there are only 2 parts that can be out of pahse on these and thats the tweeters.....

There is only 1 main driver so that can't be out of phase.

Dan

Hi Dan,

Just had a gander at the spec of the RSFX range. Appologies for not looking this up earlier.

It seems the crossover frequency is 2.2 kHz so I'd say from that the "tweeter" would be better described as a mid/high freqency driver, rather than a "tweeter" in the true sense. Usually, a tweeter would handle frequencies above about 4 kHz only. So, yes in your case, changing these between bi-pole and di-pole should make a difference.

For what it's worth, I use B&W tripoles and in di-pole mode, the crossover frequency is 250 Hz using mid/high range drivers, but in "monopole" mode (direct radiating) the crossover frequency is 4 kHz using a "tweeter". I use di-pole mode for movies but "mono" for multi channel music.
 

Mark.Yudkin

Distinguished Member
Just remember that Quad call their ESL-63 electrostats and beyond FRED: Full-Range Electrostatic Dipole. The sound coming out of the rear is (obviously) 180° out of phase with the sound coming out of the front, since it is the same physical membrane creating both, and the membranes emulated a point source by using concentric rings and delay lines. This, BTW, is a true dipole as the word originally meant.
(physics) any object (such as a magnet, polar molecule or antenna), that is oppositely charged at two points (or poles).
When used for effects speakers, the sound is of course not emitted from opposite sides, nor is it a point source, and hence both bipole and dipole are complete misnomers. Nevertheless, what does remain is that in a "dipole" the sound from one side has the opposite phase form the other. Hence there is centre cancellation and an apparent wider sound field.
 
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