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Dipole/bipole or direct, plz help me choose!


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#1 of 4 Micah

Micah

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Posted May 12 2002 - 09:50 AM

First, my system and room specifications:


Denon AVR-3802, Denon DVM-1800, JBL ND310 mains, JBL S-CenterII center, JBL PB10 powered sub. Room is approx 20' wide and 30' long, listening area is dead center in room. I listen to 60/40 music/movies, but take movie sound seriously. Now my question, if you couldn't already geuss what it is:


I am planning on getting four more speakers soon, two surrounds and two rear surrounds, but don't know if I should match my other JBL's by getting four N or S series bookshelf's which only come direct, or mis-match but gain bipole/dipole by getting maybe Polk f/x300i's or maybe PSB Image 10s'. Any comments?


My instinct tells me to get a set of higher end (s28II) JBL bookies(smaller N series JBL's can't keep up with my ND310's in a room this size) so that all my speakers are sound matched, and since I listen to more music than movies. At the same time I am very enticed by the diffuse soundfield of a good bipole speaker. Maybe a set of Polks for the mid channel surrounds and a set of s28II's for the rear surround channel? ARRGGGHHH!! Please help me before I spend again! Thanks to all who answer.

#2 of 4 Neil Joseph

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Posted May 12 2002 - 02:32 PM

If you are planning to soon have more than one pair of surrounds, and if you also will listen to 40% music, then I recommend directs for your current surrounds then. The dipoles are good to use if you have only one pair of surrounds and you want a more dispersed soundfield in the rear.
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#3 of 4 Selden Ball

Selden Ball

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Posted May 13 2002 - 02:42 AM

Apparently you're aware of this, but...

Dipoles are essentially two adjacent speakers wired out of phase, so that the soundwaves cancel for people seated along their centerlines. As a result, you primarily hear the reflections off the walls. Those soundwaves travel different distances, so most of them aren't so much out of phase and don't cancel anymore. This produces a diffuse soundfield without directionality.

Bipoles are essentially two adjacent speakers wired in phase, so they don't cancel. You can hear both the direct sound and reflections off the walls at comparable amplitudes. They provide some directionality as well as a diffuse soundfield.

Monopoles, or direct radiators, produce most of their sound along their centerlines. Although there is some delayed sound reflected off the walls, they are highly directional. The sound seems to be coming primarily from the direction of the speakers.

The soundfield produced by a good 7.1 receiver can be rather diffuse, since DPLII, for example, will blend the sounds sent to the surround channels. Four surround speakers wind up being rather close to one another, too.

In other words, monopoles should be fine.
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#4 of 4 Cameron Yee

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Posted May 13 2002 - 04:12 AM

I used a pair of Polk f/x300i dipole/bipoles for about a year, decided recently to compare the experience with a pair of JBL s26s (making all my speakers, except the subs, JBL Studio Series) and am now a monopole convert. Watching films like Episode 1 and T2 are a much more powerful experience now. I like diffusion, but I think the dipoles diffused too much and sapped the "energy" of the surround effects. While I still prefer a tad more diffusion in the less aggressive moments of films (e.g. music soundtrack, ambience) my overall impression is monopoles provide a much greater balance between localized effects and ambient sounds. Plus, ambience seems to be as much an engineered quality as placement, speaker type, etc. In other words, an audio engineer can make something sound diffused so in a sense there's no need to diffuse it again with dipoles.

Also it's nice to have timbre matched speakers, especially with flybys. The mismatch of the Polks and JBLs always bothered me in scenes like Heat's airport runway showdown.

In my research I did find an article in which a blind test showed that for 7.1 folks tended to like dipoles on the side and monopoles for the rear center. My system is just a 5.1 so I can't speak to your exact situation.
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