|View Poll Results: Do You Prefer Bipole, Dipole, or Monopole Surround Speakers?|
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In the early days of surround sound, the surround speakers were most often bipoles or dipoles, with two sets of drivers facing in roughly opposite directions. In bipoles, the two sets of drivers are in phase with each other, while in dipoles, they are out of phase, which creates a null region between the two sets of drivers. The goal with both designs is to create a diffuse soundfield with much less localization in the surround channels, which matched the diffuse nature of the mix in those channels.
These days, the surround channels often carry much more localized information, which is why monopoles, also called direct radiators, are becoming more popular as surround speakers. This type of speaker emits sound in only one direction rather than two, allowing it to present a more precise surround soundstage.
Which type of surround speaker do you prefer, and why?
I use (4) B&W 802D as surrounds :)
Great for music and movies
I have moved the K4 tripoles to the rear surround position in place of monopole K5s but I'm not sure I need to have bothered, but I can make use of the K5s elsewhere so it seemed the best use. I'd love another pair of Wafer 1 speakers as rear surrounds but they rarely come up used as I found and new price is equal to over $2,500 so I can't justify them unless I win the lottery.
For instance, if you had some Danley Synergy horns on the sides and rear and you had them at the appropriate distance for the seating area to be fill wit the sound then the mono speaker would be the best.
My ultimate surround:
However, when it comes to the more conventional speaker, I would have to say that I still think the mono is best, maybe not optimal, but the bipole would create more room interaction which MAY not be good.
Trying to enjoy the simple things in life.
I am using two quadpolar Axiom QS8's that replaced my monopolar speakers (side surrounds) and I find the directionality to be just awesome. I am much more immersed than before and rarely can I tell where the speaker is located just by listening. I don't see myself ever getting rid of them or having the need to upgrade. The beginning underwater scene in Prometheus was just insane - the sound made me feel like I was underwater with the bubbling above me and all around. Great surround track, IMHO. Anyway, my rears are monopolar and they seem to do the job just fine.
I have a second row that is rarely used so I would expect that the surrounds probably sound a little more forward than intended, but I do have a pair of surround back speakers that helps envelope the viewers if sitting in the back row.
Now I also used to have some Def Tech BP10Bs for mains that were in an array with a Def Tech CLR2000. While the BP10Bs were a good speaker for two channel music, I found that with many of the soundtracks where vocals and sounds effects were mixed across the front three channels that the tonality was an issue. So I upgraded the front array to three Def Tech CLR3000 speakers. This by far has been the best audio upgrade for multi-channel soundtracks.
As others have said I think the room plays a big part if a particular speaker will work in a particular setup. The problem though with true dipoles is that the left and right speakers should be mirror images of one another and many manufacturers that made them and most don't anymore cheaped out and just made the same identical speaker. Ideally if a sound is supposed to be in phase between the left and right surround channels you want the left and righ forward facing driver moving in the same direction. When they used the same speaker design instead of mirror image you have one forward facing driver moving forward while on the other speaker the forward driver is moving the opposite direction. It's just another way that bad dipole designs can introduce phase errors in the listening environement.
I make use of Bipole speakers on 34" stands to allow better placement and effect then mounting on walls in current setup, as most rooms are never ideal dimensions.
"Listen with an open heart and mind."
But if a movie uses the theatrical sound mix or one substantially derived from it, then the mixer would have been assuming the kind of diffuse surround array standard in theaters., and reproducing that mix is going to sound compromised coming from two directional sources.
My solution is four directional speakers for surround, so that I can run in Direct mode (disabling the rear surrounds) for 5.1 music, and in DPLIIx mode for movies (with the rear surrounds aimed for diffusion, rather than pointed at the listeners). This seems to work for my needs, in my room.
on the Edge
of the World
Dipole / bipole were created and used specifically for THX setup during matrixed surround (read: Dolby Surround). You go to Dolby and DTS sites, they all recommend monopole. Mixing studio have always use monopoles too; hence it's the correct way of reproducing the sound as the soundtracks were recorded in the studio.
Depending on studio recording the rear channels might just represent reverberation, so there might be little benefit with using monopole vs bipole for reproduction in a home environment against your room layout. Isn't the performer suppose to be in front of you, not on the sides and back of you? With movies its different as you said, the studios like to have moving or rotating sound effects to make the listening environment more lifelike.
One more point that's missing here, is that I found a lot of surround speakers are not well made, and offer poor diffuse sound-field generation compared to monopoles. You get what you pay for here, don't go cheap on the surrounds, even if they are monopoles.
As far as surround speaker quality goes, ideally you should use identical speakers for every channel. Again, all three studios above are all using identical speakers for all channels. In the case of Abbey Road, they use identical amps (Classe) and speakers (B&W 800D). In my case, I use a group of measly PSB Century 300i large bookshelves for fronts and rears.
But I am quite sure that monopoles would probably be better in a large room.
As per the link to the PMC Wafer speaker's product page: