Can I Use Dipole Speakers in a Dolby Atmos Setup?

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Q Way back when surround sound at home was the new big thing, installing dipole surround speakers at either side of the main listening position was recommended. Are dipoles still the optimal surround speaker choice now that technology has transitioned to object-based audio formats like Dolby Atmos? Assuming that no more speakers can be added to a system due to space limitations or cost, can an existing 5.1 speaker system (with dipole or conventional in-ceiling surround speakers) work effectively with the new sound formats? —Steve Benoff, Beaumont, CA

A The dipole surround, a speaker design featuring dual matched sets of drivers facing front and back and wired out of phase, dates back to the old Dolby Pro Logic days when processors extracted a mono rear surround channel from encoded soundtracks on analog formats like VHS tape and Laserdisc. THX required the use of dipole surrounds for THX-certified speaker systems, with the main claimed benefit being more even distribution of the mono rear effects channel in a typical home viewing environment, along with reduced localization. (The surround channel was additionally low-pass filtered to achieve the latter goal.)

Following the arrival of digital 5.1 surround formats with discrete surround channel information, Dolby started to recommend the use of direct-radiating surround speakers instead of dipoles. Installation recommendations also changed from high up on the sidewalls directly in line with the viewing seat to behind the viewing area, angled inward and on the same horizontal plane as the front left/right speakers. Those very same Dolby speaker and setup rules also now apply to Atmos-ready systems, though there’s now the additional factor of overhead effects speakers (which should also be direct-radiating).

Can you adapt an existing 5.1 speaker system for the new immersive formats such as Atmos and DTS:X? Absolutely — but with a few modifications. First, you should follow Dolby’s guidelines by losing any side-mounted dipole surround speakers in the system and replacing them with properly positioned direct-radiating models. In-ceiling speakers that were originally installed for use as conventional surrounds can also be repurposed for a 5.1.4 hybrid Dolby Atmos-enabled/overhead speaker setup (as shown in the photo). In this configuration, the surrounds get re-wired to serve as left and right top rear overhead speakers, while Atmos-enabled speaker modules can be added to the system’s main left and right speakers to deliver the front overhead effects.

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Homer Teatro's picture

There is a situation in home theater where you can find dipole speakers useful. In a room large enough to get 6 feet or more of distance from any speaker to the closest seat, I would suggest using direct radiating speakers. But in rooms where you have a listening seat that is 5 feet or less to any given speaker, a dipole speaker can deliver the correct "amount" of sound, but it will not be too loud for the nearest seat as it would be with a direct radiating speaker. This can be useful in the side surround position in narrow rooms. In "short" rooms that have limited depth and little space behind 1 row of seats, dipole speakers for rear surrounds can be useful for, again, delivering the correct "amount" of sound into the room without that sound being loud because it is so close to the listener. Most height channels should be far enough from listeners that direct-radiating speakers will usually be the best choice, but a situation like a basement system where the finished ceiling is 7 feet or even a little less... you may find direct radiating speakers too easy to localize while dipoles would spread the sound out enough that they would "disappear" into the room better. So, to recap---if you have 6 feet or more from any given speaker to listening seats you care about delivering balanced sound, direct radiating speakers are the best choice. At speaker positions that have to be 5 feet or closer to the nearest listener who you wish to NOT have the sound from that channel seem to be too close or too loud, using dipoles (left and right, even if only 1 side is 5 feet or closer) can provide a better balanced sound. If you only care about your main seat having the best sound... let the measurements from your ears in that seat to each channel be your guide to whether you might get a better experience with dipoles in some channels, and direct radiators in most channels.

3ddavey13's picture

Are ML Electrostatic speakers considered dipoles, and if so would it help to place some kind of sound reflective material directly behind the electrostatic panels?

Sandy G's picture

It is important to understand, as Al has explained, how and why dipoles were recommended to be used in tn the early days of surround sound. Basically with a dipole, you get more or less complete cancellation to the direct side of the speaker. When oriented so that the side of the speaker is pointed at the listener the listener hears no direct sound from the speaker and just hears the indirect sound that that comes from the front and rear of the speaker into the room. In effect the listener hears all ambiance.Later surround technologies such as Dolby Digital and Dolby Atmos want very specific information contained in each channel directed and heard directly by the listener. If you were to orient dipole speakers with one of the driver arrays pointed directly at the listener, you would be getting, more or less, direct information, minus the bass that would be cancelled. When using a dipole like a Martin Logan, with the front of the speaker pointed at the listener it will be providing direct information and will work just fine. The sound coming out the rear will provide a small amount of added ambiance, but this will basically not interfere with things. Again, when a dipole is oriented with the side facing the listener, you end up hearing basically all ambiance and no direct info. A bipolar speaker, unlike a dipole, has the front and rear drivers in phase with each other, rather than out of phase. It is in someways similar to an omnidirectional speaker with some drop off to the sides but not full cancellation as you get with a dipole. Bipolar speakers normally would be oriented with the front drivers pointed at the listener and work fine as surround speakers in all surround setups.

Al Griffin's picture
Thanks, Sandy, for your expert addition to my response. Very happy to have you contribute here!
Homer Teatro's picture

Also, many dipole surround speakers are sold with a mode-switch. You can setup these surrounds as dipole, bipole, or direct radiating. This way, you could use direct radiating mode when nobody is close to one of these dipole surrounds, and only change it to dipole mode if the theater is "full" and someone is sitting close to one or more channels. But if the room is large enough... direct radiating is the way to go for most systems.