WTF is CMSS?

19 03 2009

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.
Knowledgebase article SID4883

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:

Input Source

5.1 / 6.1 Output Mode

5.1 to 6.1 Upmix Output Mode

6.1-channel

6.1-channel pass-through

6.1-channel with rear center channel derived from rear left & right

5.1-channel

5.1-channel pass-through (without rear center channel)

6.1-channel with rear center channel derived from rear left & right

4-channel

4.1-channel with subwoofer channel derived from front left & right

4.1-channel with subwoofer channel derived from front left & right

2-channel

2.1-channel with subwoofer channel derived from front left & right

2.1-channel with subwoofer channel derived from front left & right

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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13 responses

19 03 2009
WTF is CMSS? « No More Goat Soup

[…] WTF is CMSS? « No More Goat Soup […]

21 03 2009
Tom

I think you should note that this is simply your opinion.
Friend of mine’s old man is an audio professor who has some very expensive kit – and of course the source is Vinyl. He say digital music will just never compare to anaolouge and I completely agree.
Audio is a wave form (analouge) where as data is… digital ( 0’s and 1’s), so something fairly fundemental has been lost the moment audio is converted from analogue to digital.
Having heard his drop-dead-can’t-quite-believe-what-you’re-hearing set up first hand, I can honestly say CMSS2 comes very close to giving you that analouge/vinyl quality of sound.
Digital audio sounds flat and lifeless compared to analogue, and CMSS2 imo give it back its body, so to speak.
Admitedly CMSS2 can’t compare to proper HD audio (same examples of which can be found here: http://www.2l.no/hires/index.html), but still, i think it sounds awesome and can’t bare to listen to MP3’s without it.

21 03 2009
23 03 2009
ZeRo-G

I would have to agree with Tom. Activating CMSS does appear to give the music (we’re talking about MP3 quality) a nice boost. I’m referring to CMSS-Surround. That’s the one that is actually worth it. I’ll agree, though, if this article is just referring to the one that emulates surround. It seems to drive more volume to the rear speakers which, as Creative says, puts you “on the stage.” To me, it makes me feel like I’m using all my speakers. My experience is merely an opinion and qualitative though (I’m an X-Fi user BTW).

Also, it should be noted that if you don’t center the point on CMSS-Surround to the middle, it will continue sounding like poorly-emulated surround.

I think I also read on Tom’s Hardware that CMSS was improved with the X-Fi since it has more processing power. Then again, it’s up to the listener.

24 03 2009
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[…] WTF is CMSS? « No More Goat Soup […]

25 03 2009
Bob Smith

I hate cmss too. It sounds shit on my receiver.

2 06 2009
theshank

“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 would agree with the first poster that … part of your post is purely subjective. Sound and acoustics is a science , no doubt about that , but ultimately the end product is what-ever a particular sound engineer , along with the recording artists decide is good. And even that is just ..a matter of their opinion. Most music is artifically mixed and mastered anyway. A studio recording has little in common with a live performance.

All I know is when I purchased 5.1 surround Altec-Lansing spkrs with a Phillips Acoustic Edge soundcard around 10 years ago I was super impressed with the superior sound of it (the Phillips card)compared to the Sound Blaster Live 5.1. The problem was I could not find a driver for Linux to use on my dual booting pc , for the Phillips card.

I am not the discerning listener I used to be , but if you have enough wattage and separation of signal you can usually tweak things to your liking. But as was said , the room size , acoustics , and personal taste all play their part also .

But to the main point … you did provide data and a solid argument against CMSS .

I found your article interesting , thanks for the info.

3 06 2009
Tom

I take back what I said previously – CMSS really is god awful.
Just stumbled across the DFX DSP plugin for WMP and it sound awesome.
Doesn’t upscale to 5.1, just really brings out the best in my MP3’s.
Would like to try the SRS Audio Sandbox but it’s not compatible with either CLs drivers or the DD/DTS encoder. After installtion it appears as another audio device.
I suspect it would work using analogue outs and encoder disabled, but can’t be assed to fish out the cables.
DFX does sound awesome. Try it.

4 04 2012
cagri

i know it’s been 3 years , but hey i play necromancer on diablo 2 too so maybe it’s my nature to revive dead threads… anyway tom, i think dfx sounds awesome too but i hate to use it because it definitely changes audio that wasn’t intented to sound anything like that in studio. On the other hand i use cmms stereo all the time because i don’t need enhancing the bitrate, khz or 16 bits to 24 bits etc… i just want to use all my speakers to get more watts, which mr. nomoregoatsoup doesn’t like. In fact Dfx does hurt the original record more than cmms for that matter. All these technologies are confusing. I hear lots of people still using cmss headphone for 3d sound in games, i never tried it. But i heard it’s very nice to play with hardware accelerated 3d sound (if you accomplish to activate it these days) on cmms headphones.

4 06 2009
Bobby

I like the SRS Circle Surround plugin for some music. It’s in cellphones, cars, Tv and home audio systems too. I never used CMSS, always tick off.

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