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DIYAudiphileElliottBridge
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14/02/2020 8:44 am  

Hi guys, just some information on Atmos specific surround setup. Some of this also applies to a 2D setup as well. A lot of this also applies to other object based surround formats such as Dts:x and Auro3D 🙂

Atmos keeps becoming more and more popular as time goes on, so I thought I should post about my knowledge of layouts as I hear some people thinking of moving to an atoms setup.

Of course as with any Multi-channel setup our aim is to keep the angles between all of the speakers as similar as possible to keep our sound stage as even as possible, the same should be said for atoms.

However there is a range of quality in terms of atmos set-up:

First we have our up-firing speakers (Audioholics call them Bouncy-house speakers as a lot of their processing is psycho-acoustic), their aim is to 'bounce' the sound off of the ceiling towards the listener, however they aren't the best setup to use. There are several reasons for this, you need a completely flat ceiling, which is impossible for some setups. But we also have the fact that the sound signature reaching your ears from these "bouncy-house" speakers is very different to that coming out of the speakers, this is part of the psycho-acoustics, because the signature is so different, you can more easily pick out the height effects, which is good because the technology creates too diffuse of a sound field for that pin-point sound, so they need it to be noticeable. This isn't great because this is meant to be object based audio which needs seamless integration between speakers, so even though you have overhead effects, they don't work as Atmos (as a technology) is intending. Think of almost comparing them to di-pole speakers (not bi-pole). Anyway enough of that, if anything needs clarifying further on that you could ask below (I think I already said to much about "bouncy-house" technology 😀 oops).

Even with the disadvantages mentioned above, a lot of people say it is a good alternative to not having any overhead effects at all, especially if you can't drill holes into the wall or mount ceiling speakers. Anyway, I have digressed enough now:

Up second and third we have our "height" speakers (which are essentially bookshelf type speakers mounted at ceiling height but bracketed to the wall), and of course our in ceiling speakers. There are benefits and drawbacks to both. I will list the ones I can currently think of:

In ceiling speaker position:

Dis adv:

Have to cut holes in ceiling and do a lot to the ceiling to brace the speaker then you have to wire through it.

You also need a flat ceiling just as with the "bouncy-house" speakers.

You also have a slightly different sound signature, try to pair in ceiling speakers that sound as similar as possible to the rest of your system, but because they are effectively an kind of "in-wall" type speaker you will have different diffraction effects on those speakers compared to those a few inches away the wall or even the "on-wall" speakers. Inherently, you will always get a different overall response so you could say the sound stage isn't entirely perfect.

Advantages:

Unobtrusive to appearance, especially good if all your speakers are in wall as you can achieve a perfectly balanced sound signature everywhere. Directly overhead you you can achieve a slightly better layout too, as the angles between all speakers can be matched more effectively, hence achieving a more seamless sound stage (this is in comparison to the height speakers by the way).

 

Height speaker position:

Dis adv:

Still have to drill holes into wall but not as difficult as cutting holes in a ceiling (you also have a less difficult job as routing the wires).

Heavier speakers when mounted need to be attached to the wall studs which sometimes may not be in ideal place, however this is the best option for mounting any speaker as the plasterboard is certainly not inert and will vibrate a lot and colour your sound 🙁 . Speakers like the SVS prime are made for this sort of thing but lack bass response so doesn't seamlessly integrate. Try to see if you wall studs are ideally positioned, if so get a good speaker mount and mount some bookshelves, this is where I will lead onto the advantages.

Depending on the shape of your room you might not be able to get your height speakers high enough for the angles between all of the speakers to be as equal as possible from the ideal listening position.

Advantages:

Possibility of having the same speaker for every channel in your room without having to use in wall speakers everywhere. This I already discussed as having the best situation of a closely integrated sound stage for that pin point accuracy always shouted about in object based surround systems.

Often a lot cheaper than in-ceiling systems. That is all I can think of at the moment. Please comment and ask as many questions as you want. I'll try and get back as quickly as possible. ;D


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ImCoKeMaN
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14/02/2020 3:17 pm  

It's nice to see some pros and cons on different setups.

For the heights I'm guessing you mean above front speakers pre atmos right?

And do you have any advice or thoughts on timbre matching for ceiling speakers?  Like do they need same power handling or sensitivity?  How distracting would it be if they are different brands etc?  

If anyone has had experience with that I'd be interested.  I am thinking about ceiling speakers but I'd need a new receiver for atmos and I'm not really there yet.

Thanks


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DIYAudiphileElliottBridge
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14/02/2020 3:56 pm  

@imcokeman

As for timbre matching ceiling speakers, that is a difficult one, which is why I prefer height speakers, and yes I do mean putting them above L and R but also RL and RR as well (sorry I hadn't made that clear, I thought I had). There are many combinations and positions available and even more, if using DTS:X or Auro3D. Also, don't worry about sensitivity or power handling too much, as long as they can play as loud as your other speakers without distorting you will be fine. As for trying to timbre match, try to compare frequency response graphs, Dolby recommends setting your in-ceiling crossovers to the sub at 120Hz so anything below that you don't have to worry about. Try to get in-ceiling speakers where you can aim the tweeters to the listening position unless you don't have a sweet spot that is, also when looking at the frequency response graphs try and see where the response rises and falls as you follow along the x-axis as this is what determines the timbre. If you really want to match them well try and also compare off-axis response plots such as polar plots (there will probably be some on google images from a reviewer somewhere), and the impulse response of the speakers as well (how quickly they stop), a good one for this is waterfall plots.

Hope this helps. 😀

 


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123Toid
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15/02/2020 1:06 am  

@diyaudiphileelliottbridge

Great write-up!  Thanks for this! I do like Atmos and understand the intrigue of up firing modules.  They are becoming very popular.  This is mainly due to the fact, that you don't have to do any more constructions, just throw them on top of your speakers and go.  The one thing I'll add though, is that is a misconception.  Even if you buy speakers like that for atmos, you still need to experiment with positioning.  If you don't the reflected area may not be the intended area.

 


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DIYAudiphileElliottBridge
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15/02/2020 3:05 pm  

@123toid

Yes I do agree, the amount of dispersion is directly related to how far your ceiling and listening position is from the speaker itself, a brilliant and simple way of positioning speakers is to use a mirror, but highly directive speakers can often sound better with dramatic over-toe. But as with everything there are preferences. Like for example I personally have a bit of a grudge against those up-firing speakers as people really aren't getting the listening experience that is really provided with atmos, I like to compare it to a soundbar with virtual surround, never as good as the real thing. However, I do accept this is the only option for many people. Luckily I don't have to deal with the WAF. 😀

My favourite option I think are the height speakers, because you don't need to cut holes in the ceiling and if you already have the same bookshelf speakers as mains you get really good sound stage integration.


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ImCoKeMaN
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16/02/2020 6:00 pm  

I was doing some more looking around and since this relates more to Atmos than my Klipsch setup I figured I'd come back to this thread =)

I found the atmos diagram from Dolby for 5.1.2 and 5.1.4 ceiling speakers here:

  Specifically page 27 for 5.1.2 and 29 for 5.1.4

It looks like with my couch against the back wall the 5.1.2 makes the most sense and matches pretty well with the diagram I made in the other thread this calls the ceiling speakers top middle.  A 5.1.4 looks like it can work with the speakers above the surrounds on the left and right, and keep the 5.1.2 positions that were top middle and calling them top front now.  

 

Also another thing I was seeing is debates around 7.1 or 5.1.2.  In my case a rear surround wouldn't really be possible so I'm more interested in Atmos, but I'm curious how an atmos upmixer in an AVR might handle merging those channels if it were to see a 7.1 track.

 

One thing Dolby mentions for the Atmos speakers is wide dispersion, is there anywhere to see some sort of specs around that?  

 

image
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123Toid
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16/02/2020 6:55 pm  

@imcokeman

You can only hope to see a speakers off axis response.  Unfortunately, that is rarely given. 

 


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DIYAudiphileElliottBridge
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18/02/2020 4:08 pm  

@imcokeman

Have a look at reviews of the speakers, you'll find that the off-axis response is usually covered in reviews of in-ceiling speakers, as for when using heights, you don't need to worry as much. Overtoeing the speakers (strongly directive ones like Klipsch's especially) generally increases the range of the sweet spot and increases imaging, sounds strange but is actually really effective.

 


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