Banner
Banner
cookie-banner

Surround-sound systems

Article Index
Surround-sound systems
Placing the loudspeakers
All Pages

 

SOUND ALL ROUND


Top quality digital audio from Blu-ray is best heard through a high fidelity surround-sound system. Forget Home Cinema – this is better!



marantz-sr8002

The AV receiver lies at the heart of any surround-sound system. Today's receivers are very complex and offer a bewildering array of options, yet they are a great way to listen to music, having some little appreciated advantages. Here's an easy guide to hi-fidelity, surround-sound style.


Surround sound gets very complicated and - yes - all those loudspeakers can be intrusive, but it also has some intriguing advantages over stereo. A surprising one is that stereo CDs, can be processed successfully into surround sound and some sound better like this. Why? A lot of the frontal muddle (out of  phase info) is extracted and sent to the rear loudspeakers, tidying up the sound.

 

Then of course, you get the full benefit of surround-sound from SACD and DVD (Video and Audio), and also Blu-ray. Blu-ray music concerts are commonly recorded in high resolution digital audio (24/48 and 24/96) and now Blu-ray music discs are appearing (see 2L of Norway) with top resolution 24/192 digital recordings. A modern AV receiver will handle all these, as well as Dolby and DTS sound tracks of all varieties.


john-mayer-blu-ray-3 2l-1


John Mayer live in high definition ( 24/96) surround-sound and Trondheim Soloists in top quality 24/192.


 

 

This is a brief overview of  surround sound systems, the practical difficulties, the jargon, drawbacks and - especially - the benefits. Of course, being a hi-fi magazine, the issue of sound quality is what we will concentrate on.


PHYSICAL LAYOUT

Surround-sound’s primary purpose was to reproduce DVD video soundtracks and its layout derives from cinema sound systems. A standard domestic 5.1 system has a loudspeaker at front centre (C), which in a cinema handles dialogue. It is supported by front left (Fl) and right (Fr) loudspeakers that construct a frontal sound stage. At rear are two, often small, Surround loudspeakers, usually identified as Surround left (Sl) and Surround right (Sr). Then there’s the (self powered) subwoofer, fed from a sixth low frequency effects channel (LFE), which accounts for the 0.1 part of 5.1, as it is in octave terms one tenth of the audio spectrum.


loudspeakers-5.1-converted


The recommended layout for 5.1 surround-sound.


 

This basic specification is commonly expanded to 7.1 where the Surround channels are supplemented by two Back channels, often pictured a pair of small, full range ‘speakers on a shelf. Nowadays most receivers have seven amplifiers on board to accommodate 7.1. However, as 7.1 means having no fewer than four rear loudspeakers, plus cables of course, for small benefit, just about all 7.1 receivers can be reconfigured to run 5.1, with front loudspeakers bi-amped - the audiophile choice - or two loudspeakers in another room. At present  movie soundtracks and most surround-sound music discs (SACD and DVD-A) are 5.1 format by the way; the rear channels being synthesised from 5.1, meaning they are fake. Initially, its best to keep it simple and install a 5.1 system. Whether true discrete 7.1 surround-sound will ever arrive no one knows, but receivers with HDMI linking can handle it.

 



loudspeakers-position-7


A typical 7.1 surround-sound layout.




In most rooms finding somewhere to put the Surround loudspeakers and getting cables past the living room door are the two main difficulties. Small Backs can conveniently be put on a wall shelf. Side Surrounds can be placed on stands or shelves. Ideally, all loudspeakers should be the same size and full range. In practice, small, full range hi-fi loudspeakers are a fine choice and will give a great sound. Surround sound makes this more attainable than stereo, as the total acoustic power in the room is split between six (inc subwoofer) or more loudspeakers and the front sound stage uses three of them, so none are especially stressed - and you can hear this as an easy, relaxed presentation with big dynamics.


It is easier to visually accommodate many small speakers, especially when it comes to the thorny problem of the centre front. And if all loudspeakers are identical, you get a smooth, cohesive sound all round, especially across the front sound stage, which is most critical.


Today’s surround-sound systems are a cabling nightmare, but this is easing. HDMI links replaces all digital and analogue cables so get a receiver with HDMI, version 1.3a or later as this carries DTS HD Master Audio and Dolby TrueHD, as well as copyright protected SACD in DSD format.


You need to keep your feet on the ground and not get carried away with the many technicalities of surround-sound to achieve good sound quality. Best to go for good quality basic receiver as they will give great stereo and surround-sound high fidelity, as well as a wonderful cinema experience from DVD and – especially – Blu-ray movies. Our reviews consistently show Onkyo and Marantz receivers offer the most consistent results and best sound quality. An audiophile alternative is to use a surround-sound preamplifier like the Onkyo PR-SC886 to drive valve amplifiers.


pr-sc886-front

The Onkyo PR-SC886 surround-sound preamp will drive valve power amplifiers for best quality.


The front Centre loudspeaker is ill suited to music and most difficult to accommodate and optimise for high fidelity. It is usually pictured as a small oblong box below the TV. Unfortunately, mixing engineers tend to direct vocals and drums into this channel on music discs, meaning lead vocals emanate from the floor and the drums have a boomy sound  - not exactly realistic. For more on this investigate the Trifield Ambisonic format, on Wikipedia, etc.


The speaker can go above the screen, but then it is high up, wires dangle down and it is visually intrusive. A small ‘speaker like the Usher S-520 is easiest to accommodate at Centre, one reason for choosing five small hi-fi loudspeakers in the first place. Concentric loudspeakers like KEF UniQs work well as centres too, because of their even dispersion, and a set of five small iQs with the centre on its side is another possibility, although KEF make two dedicated centre speakers in this range.


There’s disagreement about use of the centre channel even amongst recording engineers and sometimes it is not used in music discs; Chesky once put height information into it (and the subwoofer channel) for example! A real centre channel gives stronger imaging of course, but it is a mixed blessing with music. It is this sort of malarkey, as well as an endless variety of proprietary processing schemes, from Dolby and DTS in particular, and the peculiar logic where a system has more back channels than front channels, that tends to turn people off surround-sound. For music it is a good idea to switch the Centre channel off at the receiver. This directs the channel information equally into Left and Right speakers to form a phantom centre image, as in normal stereo. This image will be just above the loudspeakers, due to the arc of the stereo stage caused by ceiling reflection, and this will put it right in the centre of the TV screen. Quality will improve, as Centre speakers are necessarily size limited and over-burdened, and centre dominance will be less obvious in a bad mix.


Another contentious feature of surround-sound is the Low Frequency Effects (LFE) channel, which carries explosions and what have you in film sound tracks. It isn’t really necessary for music and isn’t always used, meaning a subwoofer is optional where music takes precedence. On the matter of subsonics, to reduce boom from the subwooofer, keep it away from corners if possible. Accurate tuning is crucial to get a smooth, integrated sound, yet it is a difficult process without test equipment, so take care here.


SOURCES

Surround-sound receivers can process a wide variety of sources, a point in their favour. Best to input CD digitally through SP/DIF optical or electrical (RCA ‘phono’ socket) inputs. Do not use the analogue connectors, as A/D then D/A conversion is introduced, which will degrade the sound. Also, the analogue inputs commonly overload at exactly 2V whilst CD players often produce up to 2.6V these days; Marantz and others fit attenuators to cope with this. You can use the digital output of a CD player or a dedicated CD transport.


The high resolution layer of SACD, which gives best (DSD) sound quality, can come in stereo or surround-sound. You need to look at the album’s label to see whether it is a Stereo or Multichannel DSD (Direct Stream Digital) recording. All SACDs have a CD layer to make them compatible with CD players, and this is always stereo. SACD gives lovely sound quality so it is worth being able to play it in full resolution which often provides surround-sound as well. To do this you will need a Blu-ray player able to output SACD over the HDMI link - and few do. Oppo (USA only) and Cambridge Audio have excellent audiophile players able to do this and they are not overly expensive at around £500. Both play SACD and DVD-A discs at full resolution, great for those with large disc collections. Just be aware that whilst you can play SACD and DVD-A discs successfully in many modern Blu-ray players, you get only the low resolution option tracks. This means that with SACD you will get CD quality, and with DVD-A, Dolby or DTS surround-sound where compression has been applied, both of which give slightly vague, soft quality compared to uncompressed high resolution tracks. The latter are punchier and dynamically deeper, so buy Oppo or Cambridge if you want high definition, digital sound quality.


650bd-front

Cambridge Audio 650BD Blu-ray player can play every silver disc through an AV receiver.


High Definition television commonly has Dolby 5.1 surround-sound that can be entertainingly channelled through a surround-sound system. BBC HD TV  comes with Dolby AC3 surround-sound. So if you want to experience the twitterings of a surrounding jungle in your lounge without getting charged by a gorilla, this is the way to go. See our article on Freesat.


Most receivers are fitted with VHF/FM radio, plus AM medium wave. Some have DAB, but this may be an option. Check the receiver's handbook first - it is usually available on-line in the Support area of the product.


Some of the more serious audiophile receivers also have a phono stage, so you can even play LP and - bizarrely - use Dolby ProLogic IIx to synthesise surround-sound 1970s Quadraphonic style! It may even be possible to get good results with old QS and SQ matrix encoded discs (see our Quadraphonics article), but we have not (yet) tried this.


Surround-sound is a hideously complicated subject, that’s for sure, as a glance at any receiver handbook will show you. But it does offer a fantastic experience for the family, and superb music quality too. As higher definition music recordings are released in surround-sound it becomes an ever more compelling experience.

 

Add your comment

Your name:
Subject:
Comment:
  The word for verification. Lowercase letters only with no spaces.
Word verification:

Search

Hi-Fi World, Powered by Joomla!; Hosted by Joomla Wired.