To Doug Schneider,
I was wondering which of these two types of speakers are better for a 5.1- and 7.1- channel surround-sound system. For instance, if I decided to have a 7.1-channel setup, would it be better to buy four bookshelf speakers for the surrounds or use a pair of bipole or dipole speakers. Thanks in advance and more power to your company.
Regards,
Maximillan Cue
From what I understand, you are either looking at using four bookshelf-type speakers (monopoles), or two bipole or dipole speakers. Therefore you'll either be setting up a 5.1- or 7.1-channel system. There are various schools of thought on what to use for surrounds and how to set them up. I’ll tell you what I’ve learned and what I prefer.
Monopole speakers have their drivers mounted on the front of the cabinet and, therefore, radiate the majority of their energy in front of the cabinet as well. Bipole speakers have drivers mounted on the front and back and involve the room the most by radiating sound from their front and from their rear in phase. In phase means all drivers are moving in and out in unison. This is more or less like having two monopole speakers placed back to back. Dipole speakers have drivers on the front and back and radiate similarly to a bipole, but the front and back are out of phase, meaning as one set of drivers is moving in the other set is moving out. If you measure the output of a dipole, you'll see a cancellation to the sides of the speaker because of the way the drivers are moving. The dipole’s presentation is similar to a bipole, but not quite the same because of that cancellation. Plus, bipoles tend to have more bass because all the drivers are operating in phase.
How these speakers interact in the room not only depends on the way the speaker radiates its sound, but also on the room itself, and, obviously, the speaker positioning. But there are some general rules of thumb about their performance that can be made. Bipoles and dipoles create the most spacious sound, but imaging from these speakers is less precise. In contrast, monopoles sound less spacious, but have more precise imaging. A few years ago the thinking was that monopoles should be used for surround-sound music playback, which generally requires more precision in the rear of the stage, and bipoles or dipoles should be used for movie soundracks, which tend to have diffuse effects in the rear of the stage anyway. The problem is that not everyone can afford to have two kinds of surrounds for music and movie playback, so most people are faced with the exact same questions you posed.
What you should do depends on how your system will be set up and, also, what your own listening preferences are. I suspect you’re thinking of using four monopoles to get more spaciousness, and that might work, but I can tell you what I’d do -- get bipoles, regardless of whether I were going to use one or two pairs. I prefer the sound of a bipole over a dipole, because I don’t like to have to deal with that awkward cancellation that dipoles have, and they have more bass. They involve the room a little bit more, but I’ve never found that to be too much of a problem. I also find that the imaging of most bipoles is precise enough, at least for my tastes. In fact, I prefer a little less specificity in the rear of the stage, even with music, because I can’t stand it when I can tell exactly where the sound is coming from and where the speakers are positioned, which almost always happens when monopoles are used. Essentially, bipoles provide the best overall performance in 5.1 or 7.1 systems, at least for my listening tastes. . . . Doug Schneider
