Sound formats Explained

MP3 Mp3 is the new internet audio format, capable of compressing a audio file 1:12 of it's original size. Because of the high compression ratio, it is only suitable for personal audio and PC use- it is not a hi-fidelity audio format. Some new CD & DVD players can read MP3 home recorded discs, personally I don't see the point of this. If I want naff sound, I'll buy a midi system.

Nicam Nicam is transmitted from the BBC- it is digital stereo. You can listen to Nicam stereo sound with a Nicam TV.

ATRAC Atrac is Sony's proprietary audio compression codec for the Minidisc format. Sharp and several others have their own type of compression standard.

Dolby Surround The predecessor of Dolby Pro-Logic, Dolby Surround didn't have a center channel, just stereo left & right, and a mono rear channel.

Quad- Surround This was used to add more speakers to a stereo system. Unfortunately, it totally screws up the sound. Their is no time delay between the front pair and rear speakers- it is just duplicated the signal.

'Virtual' Surround sound, 3D Audio, SRS, etc These types of sound processing are included with Nicam TV's & DVD player- the makers try to persuade this DSP process will perform as well as a full Dolby Pro-Logic system. It won't. It usually results in totally messed up sound. 3D sound also included with DVD players. Usually included because of the WAF (Wife Acceptance Factor), due to Pro-Logic's extra 4 speakers.

There are two major types of DVD players..

• Players with Dolby Digital and/or DTS processors built-in (they have 3 pairs of phono's- called the 5.1 output)
• Players without the processor. I would buy the players without, and buy a AV amp or processor with Dolby Digital/DTS processing, as they are better sounding.

More info here  

DVD has twice the picture resolution of VHS, multiple angles, subtitles, languages & sound. They also have perfect still pause, fast forward & rewind. Capable of playing back CD's- although a CD player £350 or more will thrash it for sound quality. One DVD can store upto 18GB. With various audio formats like DTS, Dolby Digital, and english, french, germen etc audio versions.

Dolby-Pro Logic. Dolby Pro-Logic is encoded invisibly onto a stereo soundtrack. It is outputted from CERTAIN sources, such as TV, DVD, VHS or LD. CD audio does not carry Dolby Pro-Logic information (although it is possible)

Dolby Pro-Logic has the following..

• Full-range, left audio signal
• Full-range, right audio signal
• Matrixed (limited range) center- the info is squeezed out from the left & right channels
• Mono surrounds, limited range- rear info is squeezed out from the left & right, delay is added.
• Bass frequencies are handled by the AV amps/processor bass crossover. DPLogic has no dedicated LFE channel

DPLogic is a analogue audio stream, whereas Dolby Digital is digital. DPLogic cannot compare with DD for pure clarity. A simple way of explaining DP logic processing is the rears are reversed phased of the fronts, and the center is partially phase between fronts & rears.

Dolby Digital (aka AC-3) is the big audio format at the moment, available on DVD & Laserdisc. AC-3 has 6 channels of audio, but because the sub channel is limited range- it's called a 5.1 system

• Full-range, discrete left audio signal
• Full-range, discrete right audio signal Full-range, discrete rear left signal
• Full-range, discrete rear right signal
• Full-range, discrete mono center
• Limited-range, mono (15hz-120hz approx. (not sure of exact frequency))

Dolby Digital sounds much better than Dolby Pro-Logic, as Pro-logic has mono rear effects versus AC-3's stereo. Also Pro-Logics center & rear channels are matrixed- they are not totally discrete from the others, and Pro-Logic rears are limited frequency, range to DD full-range rears.

EX Surround The new Dolby Digital format for cinemas, and eventually home audio. DD

EX Surround has the following extra channel.

• Mono side channel- for inbetween effects fronts & rears

The extra channel is ot discrete like the other 6 in Dolby Digital 5.1, in fact they are matrixed like Pro-Logic.

EX Surround is backwards compatible (if you have a Dolby Digital amp, it will be able to use DD EX surround software, but it will only decode the normal Dolby Digital 5.1). The new Terminator 2 DVD edition has DTS & Dolby Digital EX Surround on it.

Mpeg-2 Mpeg-2 is the audio format for Ondigital & Skydigital. It is a 5.1 audio system like Dolby Digital, but it has not taken off for DVD (it did try though). Sky are going to replace Mpeg2 with Dolby Digital in the US. Not to be confused with Mpeg-II video compression, the format for DVD-Video.

DTS is another 5.1 sound system. DTS music DVD's are supposed to sound superior than the Dolby Digital version, as DTS has a higher sampling rate, and a lower compression ratio. Unfortunately, DTS hasn't got a huge software library available as Dolby Digital, although it is taking off. It has been around for years, even when Laserdisc was around. Another drawback of DTS is that their is a digital 'screech' upon the soundtracks initial 1 second initialize. Make sure you turn you amp down!

6.1/ES/Disctete/EX/Neo/Music Don't know about the new DTS versions- there are so many, and also new lower bitrate of 7xx Kbps (it used to be 1.4 Mb/sec) I know the 6.1 ES is matrixed extra rear channel, which is far from perfect. I proper discrete channel is far superior. Also just out 24/96 - 25 bit, 96Khz for all 6 channels.

HDCD comes from very few CD audio discs. They are supposed to sound better than normal CD's I can only tell a slight increase in quality. I have about 400 albums, only 1 of these is HDCD (Blondie: No Exit) The HDCD processor in the CD player decodes the data and translates this to a 20 bit datastream (CD audio is 16 bit 44.1 Khz) HDCD discs are mainly classical. Some AV amps/processors can decode HDCD. Also some DAC's & AV processors support HDCD (Audiolab 8000DAX, Tag DAC20, Tag AV32R etc)

CD-Text Not a sound format, just Sony's way of adding text which is scrolled on the display as you play the disc. I have only 2 CD's with CD-Text. Bit of a gimmick.

THX is not a sound Codec like Dolby Digital or DTS, it is purely sound extensions that happen before & after the processing. It is licensed from Lucasarts. Hardware must pass certain tests to gain certification. THX bearing equipment include -sources like DVD & LD, AV amps & processors, speakers and even speaker cable. THX functions include..

• RE-Equalization™- filters out the high frequencies, these are adjustable to suit the listeners taste/speakers.
• Timbre Matching™- matches to sound to unsure front-to-back panning sounds smooth and not obvious.
• Decoration™- Shifting the phase for Dolby Pro-logic rear effects and helps diffusion of rear effects
• Bass Crossover- advanced settings/adjustments for bass control. Also removes low frequencies to the fronts and directs it to the sub- this increases dynamic range.

THX systems are designed for home theatre, they really don't sound too good for stereo reproduction. The front three speakers in THX are identical (except the centre crossover) they must reach 80hz at 100W continuous. The rears demand tri-pole configuration 80hz at 100W, and the sub needs to go down to 15hz continuous at 100W, and high-frequency roll-off at 80-85hz.

& Luscarts have created a new classification for home use, this is now nominated as the SELECT version. The Ultra is the same as the old THX. For Select- power output has been lessened, as has subwoofer output. THX Select speakers are more affordable than Ultra spec versions.

Here's two, a M&K THX Select (approx £2000), and a M&K THX

THX 2 is also due, more support for 7 channel, music & cinema modes etc.