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Discussion in 'Beginners, General Questions' started by Myo K, Apr 15, 2003.
and how does it relate to speakers?
"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?
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.
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.
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.