Surround speaker positioning is a complex subject. However, it is made more complex by guidelines published by Dolby and DTS for their object-based systems that seem to be one-size-fits all.
Dolby’s recommendation is to position surround speakers at ear height and not to use dipole or tripole speakers in surround and surround back positions. While this sounds straight-forward enough, this totally ignores THX’s “every seat a good seat” mantra, which I certainly live by when it comes to home theatre.
Direct Radiating Speakers
Mounting surround speakers at ear height – including for Dolby Atmos or DTS X / DTS X Pro – can cause the following issues:
- Unless you sit exactly in the centre position, one side of the surround sound field will be stronger. This is exactly why cinemas don’t mound surround speakers at ear height.
- Direct sound can distract from the front sound-field
- While home mixes might be mixed this way, cinema mixes are not.
So what effect does raising the surround speakers have?
- As you raise the surround speaker height from ear height, you equalise the distance to all listening positions more and more – even if people end up sitting on the sides close to one speaker, they won’t get an earful of left or right surround.
- The sound will fill the room at the back – as opposed to your ears. The reverberations will add to the spaciousness of the sound – as long as you have the room treatment in the right places.
- Cinema mixes will have their correct tonal balance restored.
If you have a 5.1 or 7.1 setup, you will be able to raise your surround and surround back speakers much higher – even closer to the ceiling – then if you have object based audio (Atmos or DTS X / DTS X Pro / Auro 3D / up-mixing with the new Dolby Surround up mixer) setup with top or back height speakers. If you have only front heights, you can also raise them more without impacting steering.
If you have top speakers however, you will be able to raise them less without impacting Dolby Atmos steering so you will need to balance the need for seat-to-seat consistency and Atmos steering precision. I would still mount the speakers so they point over the listeners heads and not right at their ears as that can be incredibly distracting if you are sitting on the sides and will impact steering more across the listening space then raising the speakers.
Dipoles and Tripoles
Dipoles shoot the sound to the sides away from the listeners’ ears, while tripoles normally put the tweeters and mid-range drivers to the sides and the woofers shooting towards the listening position. The reason this is done for tripoles is that base frequencies may never reach the listeners – even indirectly – unless they are shot straight ahead from the surround speaker due to room interaction.
Dolby recommends AGAINST using dipoles and tripoles as surround and surround back speakers. I tend to agree with regards to the surround back position – as direct radiating speakers normally work best there. However, interestingly, if you want to or must have your speakers at ear height, your best bet is to use a dipole or tripole. This is because the sound is shot into the room and reaches the listeners’ ears indirectly as opposed to directly.
When mounting dipoles or tripoles, they should be mounted at ear height with the speaker – not its drivers – shooting straight ahead at the listeners’ ears. Dipoles and tripoles create a NULL cone in front of the speaker due to the sound-waves councelling each other out so that the indirect reflected sound reaches the listeners. This mimics what happens in a real theatre with an array of surround speakers.
The only exception to the above is with a sofa that is right at the back wall. In such an instance, dipole speakers can work as either back surrounds or the only surround speakers. This is because it is incredibly difficult to put direct radiating speakers behind a sofa, mount them low enough and have them fill the back of the room. Mounting them to the side can also be problematic. However, a pair of good quality dipoles or tripoles – even mounted higher up – can fill the gap nicely and shoot the sound towards both the listeners and into the side walls for a larger sound space.
Unfortunately, the big guys (Dolby and DTS) have a one-size-fits-all advice which quite frankly – does not fit all spaces. In fact in my opinion can hurt the sound. I hope this article helps you understand the balancing act when setting up surround speakers and you’ll be able to get the most ideal sound from your speakers.
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