what does bi pole di pole and tri pole mean?

Bob McElfresh

Senior HTF Member
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May 22, 1999
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5,182
"pole" means fireing in a direction for speakers.
  • Monopole (what most speakers are) fire sound in 1 direction. Often called a "Direct Radiator" because they fire sound directly at the listener.
  • Bipolar speakers fire sound in 2 directions. Often forwards and backwards so you get a back-echo some short time later, but sometimes they fire 90 degrees to each other.
  • Dipolar - these also fire in 2 directions, but usually along a wall and not directly at the listener. They became popular when ProLogic video tapes emerged. The guys at Dolby wanted rear speakers with indistinct sounds like wind/rain/noise, but DID NOT want you to be able to tell where the speaker was. So they wanted a speaker that only bounced sounds off of a wall. These speakers have fallen out of popularity with DVD's and 5.1 systems where you WANT your attention pulled to the speaker location. This is sometimes called a "indirect speaker".
  • Tripolar - these are a bit of a gimmick and non-standard. They often have 2 drivers fireing along a wall like a dipolar, and a third driver that fires out towards the listener like a monopole. Hence "Tri" pole which means 3. Sometimes there is a small switch to change the speaker from indirect to direct.

Does this help?
 

Michael Reuben

Senior HTF Member
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Feb 12, 1998
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21,763
Real Name
Michael Reuben
Bob's explanation is excellent as always. I should point out, however, that this question, like so many of the questions asked here, is largely covered in the Beginner's Primer and FAQ:

Dipole Type Speakers

The only thing missing from the Primer is any discussion of "tripole" speakers, which, as Bob points out, are non-standard and made by only a few manufacturers.

M.
 

JamesCB

Second Unit
Joined
Feb 20, 2003
Messages
440
Michael,

The FAQ probably covers this (I'm too lazy to read it), but you missed one important difference between bipole and dipole.

Bipole: Drivers on opposite sides of the cabinet are wired in phase, that is they produce the exact same sound from the front and bacj.

Dipole: The drivers are wired out of phase, meaning there is a cancellation at the side of the speaker.

Definitive Technology makes bipolar speakers.
Magnepan speakers are dipolar.
Miller & Kriesel make tripolar surrounds. (not sure how they work though)

Note: I dont mean to step on your toes. I just thought that would help. Just my 2 cents.
 

Bob McElfresh

Senior HTF Member
Joined
May 22, 1999
Messages
5,182
Oh I understand the phase issue. I just did not want to throw too many concepts at Myo.

Myo: My advice is this -

Only consider direct-radiator speakers for your HT system.

If you hear some bipolar speakers like the DefTechs (which I own and love) and want them, keep this in mind: Bipolar speakers need 2-3 feet of space behind them to work well. If your room/spouse does not allow this, skip the bipolar speakers.

Hope this helps.
 

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