It’s becoming apparent that people really don’t know that much about the infamous CMSS and CMSS2 settings featured in the Audigy’s Creative Audio Console or X-Fi. I thought I’d post a few bits that might clear things up for people. I’m not 100% sure of a few things, so feel free to post what a noob I am.
Oh, I better add: Please keep in mind that I hate CMSS with a passion. I’ll try and explain why as we go along. Firstly, let’s see how Creative sell CMSS shall we? Here’s what Creative say.
What is CMSS? and how to use it?
The following information are abstracted from our Knowledgebase on CMSS. Please check the case relevant to your sound card below. You can also access the article on directly from the URL below.
Creative MultiSpeaker Surround (CMSS) is part of the EAX technology supported by the Sound Blaster audio cards such as Sound Blaster Live!, Sound Blaster Live! 5.1 series, Sound Blaster Audigy series, and Sound Blaster Audigy 2 or later series. It can also be found as a CMSS button on some multichannel speaker systems such as the Creative Inspire T7700, T6600/T6700, Creative Inspire 5.1 or Digital 5700, and on the external Digital I/O modules shipped with Sound Blaster Audigy 2 or Sound Blaster Audigy 2 ZS.
It can upmix stereo sources such as MP3, WMA, or Wav, to 4.1/5.1/6.1/7.1 channels depending on your speaker setup and sound card model.
What is Upmix and how does it work?
The 5.1 to 6.1 Upmix works by deriving a rear center channel from the rear left and right channel. Illustrated below is the speaker output scheme for the various input sources:
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Input Source
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5.1 / 6.1 Output Mode
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5.1 to 6.1 Upmix Output Mode
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6.1-channel
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6.1-channel pass-through
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6.1-channel with rear center channel derived from rear left & right
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5.1-channel
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5.1-channel pass-through (without rear center channel)
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6.1-channel with rear center channel derived from rear left & right
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4-channel
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4.1-channel with subwoofer channel derived from front left & right
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4.1-channel with subwoofer channel derived from front left & right
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2-channel
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2.1-channel with subwoofer channel derived from front left & right
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2.1-channel with subwoofer channel derived from front left & right
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So we’re clear at this point, hopefully. The center speaker will be playing both the same sounds from both left and right speakers. Now that’s plausible for filling large rooms, but on your average room you’re effectively damaging your sound field. You can’t expect to get fully directional sounds, nor can you expect a sound interpretation close to the original. I personally enjoy hearing music “as it was intended”. Now if you’re splitting a 2.0 channel MP3 to 6 channels, that’s 4 channels of stuff that’s already being played somewhere else. You’re just adding volume and digressing from the artistic source.
I understand Dolby ProLogic uses an (almost) identical technique for television, but with one difference. The movie/tv show producers code the content with Dolby in mind, and it’s intended. Somehow I don’t think Iron Maiden had CMSS2 in mind when they wrote “Can I Play with Madness”.
Dolby ProLogic II is a little different. The newer version can create discrete sound channels. To put it simply, ProLogic’s surround speakers play the same sounds -ProLogic II however has different sounds at different times from the rear speakers. This is where we can compare ProLogic II to CMSS2. I’m aware Dolby ProLogic II has a music mode for music -but it still sounds crap compared to a quality pair of stereo speakers or headphones. It’s ok for Movies though, as they were encoded that way.
X-Fi users get that bloatware entertainment thingie where they have to switch modes for music, games and movies etc. Why? Let’s ask Creative again shall we?
If you are listening to stereo content like MP3’s or CD’s and you would like the sound to be played over your surround sound speaker system, you can enable CMSS 3D on your X-Fi card.
It is important to remember that if you do wish to play a 5.1 encoded file like Dolby or DTS soundtracks, you will need to turn CMSS off. Otherwise you might not receive each discreet channel.
There we have it. Even Creative have enough common sense to suggest we turn CMSS off for movies. Why? Because CMSS channel matrix ruins the directional sounds -and you’ll really notice lack of dialogue volume. That’s why I turn it off and use AC3 Filter if any upmixing needs to be done. My son watches a lot of cartoons recorded in stereo avi format. It’s about the only useful reason to ever use upmix – to get the sound above your display.
CMSS, CMSS2 really don’t sound as good as a home made matrix, tuned to suit it’s need. Room size, room shape, furniture placement, speaker placement, speaker type – there are just too many variations in environments. I’m sure that if people took the time to tune AC3 Filter properly they’d never go back to Creative’s basic “one-size-fits-all upmix effect”.
So I better tie up some sort of conclusion. It’s been about 5 years since I came to it -but here it is anyway. If you want to play MP3/CD/Stereo sources -play them in two speaker. All you’re getting with upmix is a few more watts in volume, but you’re losing quite a few things. If you want to listen to music in 5.1 or above – then buy dts or Dolby Digital Audio DVD. Dolby Digital and DTS simply cannot be compared to inferior upmixes from ProLogic or CMSS.
I did have a URL in my favourites that demonstrated (with some geeky graphs) of what happens to SNR when you enable CMSS or that god-awful Crystalizer thing. I can’t find the link right now, but I’ll post it if it turns up. Anyway, the sound quality test is enough to make it obvious. If your system sounds better with CMSS on, perhaps your satellite speakers or whatever aren’t suitable for loud music in only 2 channels. Sure they’ll be great for movies and games -but only because they are coded to perform that way. Music is coded in to two channels usually (for your two channel ears).
You can find further information from the links below, check out the Dolby Wiki reference especially.
Dolby Pro Logic
CMSS
AC3Filter
Dolby Digital AC3
Peace!
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