: Are Dolby Atmos Enabled speakers special? I have KEF Q900 tower speakers and want to use a pair of KEF Q15s as Atmos speakers on top of the towers. What angle should they be aimed at the ceiling?
: I'm glad you asked about implementations of Dolby Atmos that do not conform to the company's guidelines. I've spent the better part of the past year toying with various Atmos configurations in my studio, as well as attending many demos, and in the process, I've tried various approaches similar to what you are asking about.
But before I get to that, let's review what Atmos-enabled speakers are. Dolby Atmos is an audio format that adds overhead speakers to a standard surround array. You can mount speakers directly on or in the ceiling, or you can use "Atmos-enabled" speakers that point up at the ceiling, which reflects their sound back down to the listeners, creating the effect of sound coming from overhead. Atmos-enabled speakers integrate upfiring speakers on top of conventional front-firing speakers, while Atmos "modules" are separate speakers normally placed on or near the front LR and/or surround LR speakers.
Atmos-enabled speakers bounce sound off the ceiling to create height channels.
The answer to your first question—are Atmos-enabled speakers special?—is yes. The angle at which Atmos modules fire sound at the ceiling is just one factor in a proper Atmos-enabled speaker design. Other crucial considerations include dispersion characteristics and maintaining proper phase in 2-way designs.
Some Atmos-enabled speakers and modules use concentric drivers, while others employ one or more full-range drivers. Furthermore, good Atmos-oriented reflected-sound speaker designs use absorptive materials around the driver(s) to limit sound leaks to the sides.
Controlled dispersion is key to achieving the illusion that audio is coming from above. You only want to hear the reflected sound that bounces off the ceiling, not sound directly from the upfiring speaker itself. In order to achieve the best height effects, you want the beams of sound to be behave like spotlights, not floodlights.
One key differentiating factor between a standard bookshelf-style speaker and an Atmos module is the inclusion of a hardware circuit built into each module or speaker. Dolby says the processing it performs enhances the sense of sound coming from overhead. Manufacturers have to pay Dolby a licensing fee to include this technology in a design, and without it, a speaker does not qualify as Atmos-enabled.
When I first started experimenting with Atmos, using compact 2-way bookshelf speakers in a reflected-sound configuration produced good results. As I experimented, I discussed the use of satellite and bookshelf-style speakers for the reflected-sound channels with Dolby engineers as well as several speaker designers. While they did not explicitly endorse this sort of experimentation, I gleaned that it was OK to experiment as long as you understand the challenges you face.
Fortunately, Atmos for the home is robust and adaptable. If you keep a few key concepts in mind while experimenting with reflected-sound speaker arrangements, you should succeed in achieving 3D audio immersion without necessarily following Dolby's guidelines to the letter.
Let's discuss what you can do to implement Atmos using reflected sound and your KEF Q15s. It's 100% possible to get a good result—I know because I've done it using a number of different compact bookshelf speakers. The key to success is understanding how to coax the speakers you use into behaving more like well-designed Atmos modules than wide-dispersion bookshelf or satellite speakers.
During my experimentation, I found it was better to tell the system I was using standard in-ceiling speakers for height channels, rather than Atmos-enabled speakers. This let me choose the crossover point rather than using the predefined crossover prescribed by Dolby.
I determined that a 120 Hz crossover worked well for my reflective-sound system. The danger in using a lower crossover is that the low frequencies are omnidirectional, and they arrive at your ears directly from the speaker a lot earlier than the midrange and treble, which must travel up to the ceiling and back.
The KEF Q15 is an interesting choice for this application because it features a concentric 2-way driver, which turns out to be an optimum design for reflected-sound Atmos applications. KEF and Pioneer Elite both use concentric drivers in their Atmos-enabled products. However, it is quite possible that the dispersion of the Q15s is too wide to be optimal. There are two ways to solve this problem: add some padding/absorptive material around the driver to control sound leakage—an approach used in many official Atmos-enabled speakers—or elevate the speakers.
According to Dolby, the reflected-sound modules do not need to be directly above the speaker channel they pair with—there's about three feet of leeway for positioning. The best use of that leeway is to elevate the modules (or the speakers you are trying to use as modules) several feet above the tops of the corresponding ear-level speakers in the system. One option is to use short speaker stands on top of the main speakers. This simple act will ensure that you hear more reflected sound and less leakage.
If you can add acoustically absorptive padding around the driver and raise the whole contraption a foot or two, that is sure to produce the best result.
When it comes to the question of what is the optimal angle for the reflected-sound speakers, I recommend that you experiment to see what creates the best effect. The ideal angle will vary a bit depending on room size and seating position, but the goal is to make the reflected sound appear to come from the same spots you'd place ceiling-mounted speakers in an optimal configuration—that is, slightly in front of and (if you're using more than two upfiring speakers) behind the listening position.
One of the best ways to know if an improvised Atmos reflected-sound system is working properly is to run the automatic speaker configuration utility on the AVR or pre/pro. The system should report distances for the height channels that are consistent with the total distance from the speaker to the ceiling and then to the listening position.
If the automatic measurements don't include the extra distance required for the reflection, that's a sure sign it's not going to work because it means sound emanating directly from the speaker is louder than the reflected sound. For a proper Atmos effect, the reflected sound has to be louder than the direct sound.
If you take care to properly deal with the dispersion of your reflected-sound speakers, you'll likely achieve a good result. On the other hand, if you simply place bookshelf or satellite speakers (like the KEF Q15s) directly on top of existing tower speakers and wedge something underneath it, chances are the result will not sound very good. It's certainly worth experimenting if you already have the KEF Q15s on hand; you could well like what you hear.
If you've got an AV question, please send it to Scott Wilkinson (firstname.lastname@example.org) or Mark Henninger (imagic, email@example.com
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