Ever since Alexander Graham Bell patented the first electric loudspeaker nearly a century and a half ago, speaker engineers have been steadily improving the technology used to produce lifelike reproductions of recorded sound. In 1940, Walt Disney pioneered the first developments of surround sound in a theater environment, and the industry took off from there.
However, technological advance quickly outpaced the actual acoustic science behind creating an ideal surround sound environment, which remains an active field of research even today. In the rush towards the “perfect sound” a number of competing speaker technologies came to market: the monopole speaker, the bipolar speaker and the dipole speaker.
Newcomers to the surround speaker market are understandably mystified by the difference between these technologies. Which one is better? Should they be combined for the best possible sound? Fortunately, our engineers at Fluance are happy to elaborate:
First, Some Helpful Definitions of Surround Speaker Types
In order to correctly gauge which speaker type is best for you, it’s important to know exactly how monopole, dipole and bipolar speakers differ from one another:
- Monopole speakers are probably the type you are most familiar with. These are direct-radiating, forward-facing speakers wherein the speaker drivers (the cones) are all facing the same direction on a flat surface.
- Bipolar speakers feature two speaker drivers placed at an angle to one another in a single encasement. The speakers are engineered to be in perfect phase with one another, radiating sound over a wide sound field.
- Dipole speakers also feature two speaker drivers in a single encasement, but they are wired to be out-of-phase with one another, creating a phase-cancellation null at the listening point.
Now, what do these definitions mean for your home theater setup? Let’s examine each one in turn:
Monopole Speakers in a Home Theater Setup
Monopole speakers direct sound towards the listener. In a 5.1 surround speaker setup, for instance, this means having all five drivers pointing towards the listener. This is a very reasonable way of ensuring that the listener gets an even response from each speaker. There are two situations in which a monopole speaker setup is ideal: When a single listener wishes to sit in the “sweet spot” equidistant from each speaker, and in rooms larger than 5,000 cubic feet that nonetheless feature few seats, all placed as close as possible to the ideal listening position. The further away from that position someone sits, the more likely they are to be disturbed by the louder sound of the speaker closest to them.
Bipole Speakers For Advanced Home Theater Use
Since bipole speakers feature two drivers in phase with one another, the sound they produce diffuses over a wider field while nonetheless coalescing towards the rooms “sweet spot”. This is ideal in a situation where you need to use a room’s acoustic qualities to diffuse sound for its audience. These speakers can provide excellent coverage when placed correctly—often, directly behind or to each side of the ideal listening position. There are cases when a bipolar speaker can be used as front channel speaker as well, thanks to its phase correlation which includes the space directly in front of the two offset drivers.
Dipole Speakers, Problem Solvers for Home Theaters
This particular speaker type was originally conceived as a way to make monophonic sound (think of vinyl albums from the 50s and 60s) appear warmer and more ambient. By using phase cancellation between the two drivers, sound is diffused away from the listening position. This might sound counterintuitive, but it can produce a more lifelike feel in a small-room surround sound environment, particularly if there are many seats placed throughout. Where direct-radiating speakers concentrate their sound, creating hotspots, the dipole phases out distracting signals to create a more balanced response everywhere in the room—when properly placed.
It’s worth mentioning that there is an industry-wide tendency to avoid these types of speakers unless they are deemed absolutely necessary. Phase cancellation can produce unexpected effects, such as losing much-needed bass frequencies. Due to the physics of phase cancellation, you might find that even boosting the bass to its maximum level doesn’t suffice. Most home theater setup buyers are perfectly capable of getting the right sound using a mono- and bipolar speaker combination.
The Keys to Great Sound: Placement and Room Acoustics
One of the mistakes newcomers often make is assuming that buying the “best” speakers will produce the best sound. The reality, however, of room acoustics and speaker placement mean that there is no one-size-fits-all solution. The way your speakers interact with your room is simply too important to overlook. Smaller rooms that benefit from acoustic treatment and have multiple seats usually offer better results with dipoles, while larger theaters can safely use direct radiating surrounds since room reflections don’t need to be emphasized as much. In the end, the best home theater setup is the one that fits your particular room best.
Signature Series Hi-Fi Bipolar Surround Sound Speakers
Unique bipolar speaker configuration creates a widely dispersed three dimensional soundstage for optimum surround imaging.