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Direct or Dipolar Speakers for Dolby Atmos?

Al Griffin  |  Nov 17, 2014

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Q I am building out a dedicated 7.2-channel home theater and was planning on buying dipolar surround speakers to help “spray” sound along the side and back walls. After reading a few articles on Dolby Atmos, however, it seems that direct-radiating speakers would be the more appropriate option since they can better pinpoint objects in the room. Am I correct in thinking that direct-radiating speakers would serve better in an Atmos environment, or do I have things totally wrong? —Adam Tremai / via e-mail

A We’re all still thinking through the details a bit this early in the game. A key element to Atmos at home is the “height” experience, and that will most effectively be delivered by on-/in-ceiling speakers. A more popular Atmos option, however, is likely to be “elevation” speakers that bounce sound off of the ceiling by firing at an upward angle from the top of the front and/or rear channels.

If your plan is to bypass both ceiling-mounted and elevation speakers for your 7.1-channel setup, chances are you won’t be reaping the potential sonic benefits of Dolby Atmos. An advantage to dipolar designs is that they present a diffuse soundfield that emulates existing cinema multi-speaker surround sound arrays. In Atmos cinemas, however, these multi-speaker arrays have been repurposed into individually addressable point sources. So, while diffuse surround speakers remain a good choice for 5.1-channel speaker setups in small rooms, or as surround channel speakers for 7.1 setups in larger rooms, they don’t emulate the effect of surround channels as now used in Atmos cinemas. Also, while dipoles are adept at “spraying” sound around the back and side walls of a room, they won’t necessarily give you the height dimension that a ceiling-mounted or elevation speaker should deliver.

To sum up, getting a proper Dolby Atmos experience at home will likely call for direct-radiating, roughly ear-height speakers in the positions used today for 5.1 or 7.1 systems plus at least two or four speakers for the height effect—namely ceiling-mounted and/or elevation speakers that bounce sound off the ceiling of your room in order to emulate ceiling speakers.

COMMENTS
HMB's picture
Submitted by HMB on November 18, 2014 - 4:25pm

My present side speakers are dipoles, that are set at about 7 feet high as that was a convenient place to put them - I bet many people have their side speakers on the high side. It seems that Atmos is designed for ear level, directional speakers. This will be its biggest stumbling block.
Another comment I have- I bet most receiver calibration systems won't be optimized (yet) for Atmos systems. Maybe I should wait awhile until all of the kinks are worked out.

HomerTheater's picture
Submitted by HomerTheater on November 20, 2014 - 8:44am

Dipoles have NEVER been the right speakers for surround sound systems with 5.1 or 7.1 discrete channels except for ONE case...

If your room is on the smaller side and you can't place the side or rear surround speakers more than 5 feet from the main seat(s), you don't necessarily want "normal" speakers. When you are that close (5 feet or less) to the side or rear speakers, you want to use speakers that don't project directly at the listening position, so dipoles would be good to use in that case. For every other case, you WANT directional speakers in the side and rear (and height for newer surround modes). Reason being, discrete surround can and will place specific sounds in specific locations. For example, there might be a scene where a sound like dropped keys happens in the right rear. The "image" of those keys dropping will be specific with directional speakers. With dipoles in medium to large rooms, you'll get a huge, out of proportion and not well-localized "image" of the sound of the keys dropping.

Dipoles for surround sound were the right thing to use way way way back in the days of Dolby Surround were there were no discrete sounds in surround channels, you only would get ambience in the surround channels (wind, crickets, etc.). In those days there was never any "imaging" of sounds in the surround channels. Dipoles helped spread out that ambient sound. Dolby Surround (and other surround options from that time period) extracted surround sound from stereo mixes. When 5.1 and 7.1 came into existence with Dolby Digital 5.1 and DTS 5.1, each channel could be encoded uniquely with very specific information from ambience to very localized sound. Dipoles will eliminate the ability of the system to localize sounds in medium to large rooms, but in small rooms, dipoles avoid the problems you have if the speakers are too close to the listener(s).

And... there is a convention for describing the channels in home theaters with height speakers... they are listed like this "ground level" channels.subwoofers.height channels. I have 7.2.5 using that naming convention. So 7.2 isn't a Dolby Atmos configuration and won't benefit from using Dolby Atmos. You have to at least have 7.1.2 for Dolby Atmos, though Pro Logic IIz and DTS Neo:X will do 7.1.2 also so, again, 7.1.2 isn't "much" of a system for Atmos... you really want at least 7.1.4 to get into Atmos. This may be referred to as 11.1 in home theater AVR-speak.

xyvyx's picture
Submitted by xyvyx on February 21, 2018 - 9:44am

Sorry "HomeTheater", to suggest the reason behind the use of Dipoles at home pre-dated discrete surround channels and was only useful for small home theater is simply false. Dipoles were suggested to replicate the user of multiple direct radiators used by commercial theaters.

Tom Holman of THX was a strong proponent of the use of diffuse arrays of speakers for surround configurations. Countless soundtracks with 5.1 and 7.1 discrete channels have been mixed assuming such a configuration. Dipoles were just a compromise to get a similar effect at home.

Yes, Atmos is different and benefits from the use of multiple, direct-radiating channels. Does that mean that the prior decade+ of home theater speaker selections with 5.1 or better arrangements were mis-configured? not at all.

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