Audio Equipment and Home Theater Audio : Is 5.1 neccessarily 'surround sound'?

Is 5.1 neccessarily 'surround sound'?

I ask this 'cuz I was at my mum's a long time ago and she had a 5.1 system she wanted me to set up but it only seemed to have inputs that would make it so the Left and Back Left speakers would play the left stereo output and the Right and Back Right speakers playing the right stereo output... making it just a stereo system with 4 speakers and a sub.

Was I doing something wrong?
If I want proper 5.1 surround sound, what should I look for on the box?


Re: Is 5.1 neccessarily 'surround sound'?

The input would either be 5.1 analog (which would be 6 RCA cables) from the DVD player, or digital input (RCA, Optical, or maybe HDMI) which would carry all the signals in 1 cable.
If there were only 2 analog inputs it's not 5.1, its stereo.
then you might have a matrix (fake surround) decoder receiver,

The output would be clearly marked for 6 speakers. left, center, right, side left, side right (called surround) and subwoofer.
How many speakers did you have?

Re: Is 5.1 neccessarily 'surround sound'?

You need to look for documentation or logos indicating that the equipment has a surround sound decoder. There are various formats but the two major licensers of decoder technology are Dolby Laboratories and Digital Theater Systems (DTS).

Regardless of the inputs or outputs available, you need to look for evidence of a supported decoder, including any of the following formats:

Dolby Pro Logic/Pro Logic II (supports phase-shifted, matrix surround, a.k.a. Dolby Surround)
Dolby Digital
Dolby Digital EX
Dolby Digital Plus
Dolby TrueHD

DTS 96/24
DTS Neo6

Please note that the prevailing format is Dolby Digital 5.1-channel surround, on all DVDs and BluRay HD discs, and iTunes standard def and High Def encodes. So, it's unlikely you will find a receiver that has a DTS decoder but not a Dolby Digital decoder, but you should at least ensure that you have a Dolby Digital decoder.

Devices with a Dolby Digital decoder are capable of decoding Dolby Surround mixes or any content designed for a Dolby ProLogic/ProLogic II decoder.

Member - DFW Film Critics Association

Re: Is 5.1 neccessarily 'surround sound'?

Please note that the prevailing format is Dolby Digital 5.1-channel surround, on -- BluRay HD discs,
With DTS-HD MA thankfully gaining quickly, that won't be the case for long, thank god.

I can just about remember the time, when 'human suspect' was a given, not an option.

Re: Is 5.1 neccessarily 'surround sound'?

I hope not. DTS doesn't have the benefit of Dolby Laboratories' experience in signal processing and noise reduction standards, e.g. Dolby B NR, Dolby SR, etc.

Dolby Digital was born out of perceptual coding schema designed for noise reduction, and as a format, Dolby Digital and Dolby TrueHD carry metadata parameters that improve overall playback. These include dialogue normalization and dynamic range control... parameters that DTS lacks.

About the only thing I've heard people say they really like about DTS, noticeably, is that the mixes are louder... but that's actually a BAD thing. Nuances in a surround mix are lost when amplitude levels are running at or near peak constantly. See the Wikipedia article on the Loudness War ( for further explanation.

Granted, DTS is a form of ADPCM and can carry higher fidelity, but the benefits of higher fidelity are completely lost on soundtracks with levels mastered so high that signals are clipped and dynamic range is constantly narrow.

Theoretically, DTS HD MA can support a wider dynamic range than Dolby Digital 5.1, but pretty much an identical dynamic range to Dolby TrueHD. However, because DTS soundtracks tend to be mastered at or close to peak levels, the advantage of 24-bit depth amplitude resolution is lost on the format, and stereo playback of DTS-mastered soundtracks may be hampered as well due to the lack of a -3dB attenuation in stereo downmix mode.

The answer to all this is, use Dolby and turn up your volume knob... that's what it's there for.

But, I suspect just as in the case of badly mastered sound recordings of the last twenty years, DTS is gaining ground simply because its mix is louder—not better. Nobody seems to care that this is a colossal mistake... and consequently people have been buying poorly mastered sound recordings increasingly since 1989.

Any real audio enthusiast or home theater enthusiast should be annoyed and repulsed by this trend.

Member - DFW Film Critics Association

Re: Is 5.1 neccessarily 'surround sound'?

DTS is gaining because DTS-HD soundtracks carry the core-dts embedded in them, always, and BD standard states that the any movie has to have either legacy-DTS or DD soundtrack.

with TrueHD, you have to actually add the DD (or legacy-DTS) track.

and blaming DTS for participating in "loudness war" is silly, as the dynamic range of the mix is decided by the designer of the soundmix.. not DTS. granted, DTS-HD tracks seem to need about 5db's less of volume on my amp, but i do know how to turn the volume.

and please, if there's some evidence of DTS-HD tracks lacking in dynamic range compared to the TrueHD equivalent, link any evidence or reports of such a thing actually happening.

CD is not to be blamed for the loudness war, and neither is DTS.

I can just about remember the time, when 'human suspect' was a given, not an option.

Re: Is 5.1 neccessarily 'surround sound'?

Both DTS HD MA and Dolby TrueHD have fundamentally the same dynamic range. They're 24-bit amplitude values per quantization interval. This means roughly 140dB dynamic range (compared to about 103dB for Dolby Digital and 96.7dB for 16-bit stereo LPCM, i.e. CD Digital Audio).

But here's where the difference lies... after the surround sound mix is done, the MASTERING ENGINEER doing the DTS MASTER RECORDING is not held to the same specifications and standards as the Dolby Digital requirements.

I'll give you an example... if I want to use Dolby Labs' trademarks on any material I master to Dolby Digital, I need to master to an A-weighted average loudness, Leq(A), of about -27dBFS. This is substantially lower than the average loudness of a DTS or Red Book CD Audio spec. If the DTS engineering specs say -21 to -19dBFS, then there's less overhead remaining and the same track will require greater compression or suffer greater distortion at peak levels. On top of it all, if DTS doesn't utilize some kind of dynamic range control/compression (and they don't), then distortion is bound to occur constantly when the DTS master recording is riding clipping levels.

It's not rocket science and doesn't require research papers to prove... if you have two formats of equal dynamic range, equal noise floor, but one is consistently mastered to an average A-weighted loudness 5dB higher than the other (due to differing mastering specifications), that's 5dB less of dynamic range overhead remaining in that recording.

You turning the volume down isn't going to improve anything, because frequency aliasing and amplitude clipping and the resulting distortion are essentially hardcoded in the master recording and thus all duplications of it. (Garbage in, garbage out)

The point here is that both DTS HD MA and Dolby TrueHD fundamentally are identical lossless formats at their core... and it's really not that difficult for a content creator (like me) to transcode a Dolby Digital mix (with matrixed surround automatically in the front L and R channels in every DD encode/transcode to support backward compatibility all the way to Dolby ProLogic decoders). The fundamental difference is that the stricter mastering specifications, and metadata such as dialogue normalization, dynamic range control, 20kHz lowpass, DC offset filters, etc. are not standard in DTS encoders and therefore put DTS mixes at a disadvantage in terms of the overall user experience.

If DTS implements the same types of metadata and mastering specifications on their format, then I'll concede it's fundamentally the same user experience as Dolby Digital/TrueHD.

Member - DFW Film Critics Association