Power output & Speaker load

Surround Modes

Channels 5.1,6.1,7.1 etc

Number of inputs

Video switching

Multi source

Multi zone

Audio ADC/DAC resolution
























- Power output & Speaker load back to menu

From the article The Relationship of Voltage, Loudness, Power and Decibels we can see the effect of amplifier power output, but one of the things people regularly try to do themselves without understanding the theory, is to add more speakers to their system in the belief that this will make it sound better or louder.

Simply daisy-chaining additional speakers onto existing speaker cable runs does not have the effect of doubling the loudness of the speakers. The first thing that will happen is the current will preferentially flow through the path of least resistance, so one speaker is going to get more power than the other and therefore try and do more work. Secondly you are altering the  load on the amplifier. This is a good way to pop an inexpensive amplifier without decent protection.


- Surround Modes back to menu

It's worth a little look back at the origins of the surround sound phenomena in order to understand what these modes are and what they attempt to do.

Throughout the 60’s and 70’s Dolby Laboratories, sound recording pioneers, were developing Dolby Stereo: An exhilarating 4 channel surround sound designed to be used in cinemas. In 1977 Close Encounters and Star Wars made a huge impact on the movie going public by embracing this new technology. Previous to 1977 movie theatres were still using mono technology developed in the 1930’s.

Dolby Stereo became Dolby Surround and was produced for the home video market in the early ‘80s. Dolby Pro Logic (1987) became the first home system to use a center channel and consequently for the first time the public had an affordable surround sound system to compete with the one Star Wars used so well in the 70’s.

Dolby AC-3 was born in 1992, an improved surround sound system developed for use with digital cinema devices. By the late ‘90s every home had its own Digital cinema device in the form of a DVD (Digital Versatile Disc) player. Dolby AC-3, which became known simply as Dolby Digital, was the obvious format to replace and improve upon Dolby Pro Logic.

Meanwhile in 1990, with backing from Universal studios, The DTS, or Digital Theatre System company was born. They created a rival digital cinema sound system. With the release of Jurassic Park, and an incredible 876 DTS systems installed within 6 months in U.S. cinemas, DTS was established as the leading cinema audio system.


- Channels 5.1,6.1,7.1 back to menu

Any respectable DVD player or home theatre receiver will happily decode either Dolby Digital or DTS soundtracks and both systems are 5.1. This is simply 5 channels or speakers and 1 subwoofer to add bass depth to them. Since this isnt a full channel of information - in fact it's normally only the bottom few hundred hertz that is available, this is known as .1 of a channel. Logically then 6.1 would use 6 speakers and 1 subwoofer, 7.1 would use 7 speakers and so on.

Next time you catch a movie, watch the opening credits to see which system is in use.

If the next opening credits you see at the cinema, use the famous THX logo, you are in for an audio visual treat. This is not however, another type of surround sound. THX, named after the title of George Lucas’ first film THX 1138, is actually a standard set by Lucasfilm.

In the early ‘80s George Lucas set out to ensure a movie looked and sounded the same no matter which cinema screened it. Extremely rigorous tests of room acoustics, projector quality and audio performance must be met for a cinema to receive a THX rating. Return of the Jedi in 1983 was the first film to be shown in a THX certified auditorium. To date there are around 2000 THX cinemas worldwide.

Increasingly home cinema products are meeting the Lucasfilm requirements for performance and display the THX logo accordingly. Many VHS and DVD titles have gone through the demanding THX digital mastering program for high post-production quality of sound and video compression as well as overall replication. For the full THX effect in the home however it is necessary to apply the same THX standards to the room the movies are going to be played in. For technical specifications on THX standards

In 1997 DTS Entertainment, a subsidiary record label of the DTS company, began creating DTS products for the home market such as DVD’s, video games and DVD audio.

DVD audio is probably the most interesting audio innovation since the compact disc. This is not necessarily because of its improved CD sound quality, but rather its use of 5.1 speaker systems. Artists such as Eric Clapton, Neil Young and Underworld, understanding that millions of us have DVD systems in place in our homes, have begun creating music with 5.1 in mind.

Not only is this a far more involving listening experience, it also gives artists “on screen” credits, sleeve notes, lyric guides and artwork opportunities that were lost after the demise of vinyl albums.


- Number of inputs back to menu

One of the items that is most quanitfiably improved as you progress up the home theatre receiver pecking order, is the number and quality of video inputs.

Be sure to investigate whether the receiver youare considering has sufficient inputs for your current and projected future needs.


- Video switching back to menu

The video switching capabilities and indeed usefulness of a receiver can usually be determined by whether or not the receiver has component video inputs and output.

Entry level amplifiers may only support S Video and may not be able to switch component, which is becoming more important with digital set top boxes, foxtel and DVD players all offering component output as their highest quality.


- Multi source back to menu

Multi source amplifiers are by default multizone capable. Multisource simply means you can use and control a second source device for the 2nd or additional zones. An example of this might be listening to the sport on the radio on the deck through the outdoor speakers, while the kids play XBox in the home theatre.


- Multi zone back to menu

Multi zone amplifiers are able to supply signal to a 2nd or additional zone. Often this means another power amplifier is required for the 2nd or subsequent zones. True multiroom systems have amplifier channels enough to accommodate running multiple rooms speakers off the one system without recourse to additional amplification.

The volume in the 2nd zone can either be remotely controlled or an inline volume control can be wall mounted in the room or outdoor area.


- Audio ADC/DAC resolution back to menu

This refers to the actual number of samples the DAC or ADC can handle per second. All things being equal (jitter management etc) the higher the sampling resolution - the more musical. Back to that phrase "all things being equal", in the real world they're not equal. Chassis rigidity, Power Filtering and isolation, internal interconnect quality, component choices and pickup and transport differences ensure that the resolution is not the holy grail - though it's a mighty fine chalice to chase in general.

In order to convert an analog waveform into a digital bitstream it is necessary to slice the wave up into very very small instants of time and record the snapshot of sound. Play these digital snapshots back at the same speed they were captured and you can reconstruct an approximate to the original waveform. (Don't laugh about the "at the same speed" business - more than one classic CD has been laid down overly fast and therefore slightly off-key. One Miles Davis CD springs to mind as an example of a 44.1khz CD released directly from a 48khz studio master tape.)

Many inexpensive CD players and pc CDRoms feature lower resolution Audio DAC's with steep filter curves offering harsh sound. Better Audio CD players offer at least 96khz sampling resolution.


- Separates back to menu

In audio circles the word "Separates" means purity and purposefulness. While for convenience and simplicity many devices have been combined into one to form very powerful and capable receivers for home theatre and HiFi use, there is always acompromise when individual components are made to share, whether it's space inside the skin, or power supply, there is always noise generated. Separates are the purest form of devices. Here you have a separate pre-amplifier, another device is just a power amplifier etc.

With separates each device is the best of it's breed. It has no compromises with power supplies. Each chassis is individually isolated so there is no crosstalk between it's innards.

Finally apart from anything else, there is a certain pride in ownership of a sports car because it's a thoroughbred. The same goes for separate components.