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Professional Recommendations for Surround Sound Design

Rob Sinden

Distinguished Member
AVForums Sponsor
If you have read my previous post “Why Good Audio Sounds Bad” or have a basic knowledge of sound waves, you'll realise that just buying good audio equipment will not give you good sound quality.

The acoustics of your listening room account for well over half of what you hear and without addressing these effects you simply will not achieve hi fidelity sound.

What Is Good Sound?

Before looking at equipment and room design, let's look at what we're trying to achieve. The graphs below show the performance of “Stereophile” magazines favourite and least favourite loudspeakers when measured in a very well designed listening room.

The graph on the left shows the smooth response of their 12 favourite loudspeakers. Listening to music on speakers that give a smooth response means that all the frequencies will be reproduced at a similar volume. The sound of one note played on a piano for example will sound just as loud as the next.

The graph on the right shows the huge variations in the response of their 12 least favourite speakers. These graphs nicely illustrate the fact that speakers that measure better tend to sound better.

best-speakers.gif


Loudspeakers in “Normal” Rooms

The graphs above show speakers measured in an ideal acoustic environment. The real problem however is that no one has a listening room with ideal acoustics.

This graph shows the typical response of a very good speaker when measured in a “normal” listening room. As you can see the smooth, even response of this speaker now looks just as bad, if not worse than one of the worst speakers.

normal-rooms.gif


As a result this very well designed, very expensive speaker will now provide sound quality that is no better than a much cheaper alternative in an ideal listening room.

The HiFi Myth

Most speakers placed in a “normal” listening room will vary more than 20db.

A 20db variation means that one note will sound more than 4 times louder than the next!

As such, even though you may be using the very best hifi equipment, the sound quality that you'll enjoy simply cannot be described as “hi fidelity” – regardless of how well the components measured in a laboratory.

Unfortunately the hifi industry ignores this inconvenient truth or uses it as a method of selling you any number of upgrades such as cables, stands and mains conditioners, none of which can fix the fundamental errors that your room has created.

Solutions from an Expert

As the problems that rooms create are rarely discussed in hifi shops or in hifi magazines, trying to find good advice about sound quality can be very frustrating. If you are looking for the best home cinema however, one man that can help is George Lucas.

When George Lucas released Star Wars 20 years ago, there was as much focus on its superb sound track as the story line. At the same time the home cinema industry was taking off with the arrival of video tape and Laserdisc.

George Lucas was one of the first people to realise that in the near future movies were going to be watched in the home just as much as at the cinema. The problem however was just like today; most home audio systems simply weren't accurate enough to reproduce his superb soundtracks correctly.

The THX Standards

George Lucas realised that with even the best hifi equipment, his films often sounded disappointing. As a result he employed the finest audio engineer he could, to find ways of improving the accuracy and consistency of audio systems.

Tom Holman was the engineer and the standards are known as the THX programme. If you want to hear just how effective his recommendations are, just book a visit to a THX approved cinema!

George Lucas wants you to follow the THX standards Tom created, so that you'll enjoy his films at their very best. Virtually all the other advice you'll be given about surround sound is given by people who know far less about film sound tracks and are simply trying to sell you stuff!

The THX standards included advice on room design, amplifier power, equalisation and the use of small satellite speakers, with separate subwoofers to play ALL the bass.

These recommendations may be 20 years old but are just as valid today as they were then - the laws of physics haven't changed.

Perhaps only 1% of home cinema systems sold in the UK comply with George Lucas's THX's recommendations. This could be because the guy in the local hifi shop knows more about reproducing film sound tracks than George Lucas... or possibly because so much money is made by selling big loudspeakers.

If you found this post helpful you may be interested in some of the other topics I've posted on:
- Why Good Audio Equipment Sounds Bad
- The Benefits of Room-Friendly Speakers
- Acoustic Room Design
- Why You Need Room Correction
- The Result of Professional System Design
 
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jackobite

Established Member
I hope you can find a dealer near you that has a good quality, well set up sub / sat speaker system. When the bass is taken care of with a good sub there's no logical reason for needing speakers that play bass. This approach can save you a fortune and provide a much more discreete installation.
...ah rob...if i could only pick your brains...my wee wee problem is..my philips 42ins plazma tv...philips pfp5532d/05 has developed a problem...one of the speakers seems to be making a "noise" mostly at lower volumes..i have a cinema
sound system...6/7 speakers ect...i won it couple of years ago...but i havent the the room for it...as there is no easy way to add a couple of speakers to the tv...easy and quick....i read long time ago headphone sockets could be used...is this true....all i want is a clean sound again....without....mutch bother...im to old to donald duck around with this problem any advice welcome...sorry to hijack your magical piece.... aint proud i need help....ta many times.:lease::lease::lease:
 
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I'm no Rob Sinden, but utilising the headphone socket on the TV to run a couple of speakers is not going to work. The output is suffient for headphones but not enough for speakers.

If you can fit a couple of speakers in but not seven, a stereo amp (with a couple of speakers), hooked up to the TV output would do the job.:smashin:
 

jackobite

Established Member
I'm no Rob Sinden, but utilising the headphone socket on the TV to run a couple of speakers is not going to work. The output is suffient for headphones but not enough for speakers.

If you can fit a couple of speakers in but not seven, a stereo amp (with a couple of speakers), hooked up to the TV output would do the job.:smashin:

no no no...not seven...but just two good sounding speakers...i remember a piece on the forum...many moons ago....i think a pair of good quality p.c. speakers were used..speakers had there own power supply..volume..ect...the speakers in the philips tv...must be quite small...ive heard great sound...on some laptops...ect....appreciate your input....thanks....:hiya::smashin:
 
I see where you are coming from...

Yes I have stereo Yamaha active speakers on my sons PC, with an optional subwoofer.

So yes, active speakers from TV headphone socket would work.:smashin::hiya:
 

jackobite

Established Member
I see where you are coming from...

Yes I have stereo Yamaha active speakers on my sons PC, with an optional subwoofer.

So yes, active speakers from TV headphone socket would work.:smashin::hiya:

thanks..thats cheered me up.appreciate..what you say...me thinks i could on the right track....ile give it a try ...ordered... reasonable speakers from....play.com......if it works great...if not, i needed speakers...for my lap top...so no harm done.....:thumbsup::thumbsup::hiya:
 

jackobite

Established Member
I'm no Rob Sinden, but utilising the headphone socket on the TV to run a couple of speakers is not going to work. The output is suffient for headphones but not enough for speakers.

If you can fit a couple of speakers in but not seven, a stereo amp (with a couple of speakers), hooked up to the TV output would do the job.:smashin:

yes....thats a thought....i suppose...you could just fit two...speakers via the cinema sound setup..or, and centre speaker......i thought you had to use..every speaker..but i suppose...two or three...would work for my needs...good idea....if push comes to shove....its something i can fall back on....thanks.....you got me thinking...and thats no mean feet...cheers.....well i would like to thank all the folks who gave me support with my wee problem......got a pair "creative inspire T10pc speakers they work fantastically well on there own at all volumes...or in unison with tv speakers at higher volumes...a mini cinema system!!!..,.sweet sweet sound at low volumes now no slurring on voices ect..all for £30.00 from play.com...with ALL leads...a ten minute job...and ah pleasure...fantastic...thanks all who helped me...to make up my mind...and to use my brain and think...all tv sound modes work well with mini speakers..with big big sound...ta folks...jackobite..ps they fit well under tv unit!!!.in unison with tv speakers......wow....
 
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BlueWizard

Distinguished Member
Just one small problem, movie theaters are money making machines. As should be crystal clear by the price of popcorn and snacks. They can easily afford to bring their rooms and equipment up to THX specifications.

However, the average person looking for a sound system, whether it be stereo or surround sound, is on a tight budget. Yes, I can maybe afford £1,000 to £2,000 for a system, but it is not very likely that I can afford to create a £10,000 acoustically tuned room to put it all in.

We live with the rooms we have.

That said, the application of some common sense, and a few basic principles can improve things greatly.

In my search for flats in London, it seems that the ultra modern bare minimalist rooms are all the rage in the UK. And while such a modern room may be pleasing to the eye, it is a disaster to the ear. The leather sofa and lots of hard polished surfaces with no carpets or curtains are a disaster for sound reproduction.

However, the old fashion soft furnished rooms with bookcases, paintings on the walls, heavy curtains on window, and thick carpets on the floors, are much more conducive to proper sound reproduction. That and the general clutter tends to break up reflected sound waves.

At my local theater, though I don't know if it is THX certified, I find that the lower section of the walls are covered with thin carpet. The much larger upper section of the walls are padded and covered with a pleated curtain like material. The high ceilings have acoustical tile on them. The walls are meant to absorb and diffuse sound, and for a small town theater, they do a pretty good job. Though, that is probably not a design that is appealing to most housewives or complimentary to many living rooms.

But the keys are absorption and diffusion of sound. When you look at your listening room, you need to look with a critical eye and ask yourself to what extent is my room absorbing and diffusing the sound?

This is especially critical for the back wall. If it is a flat open surface, then you can expect problems in the room. The same is true of the side walls, the floor, and the ceiling. Though I personally think the back wall is the most critical.

Now you can go too far. If you have every been in a sound proof room, you know it is a creepy experience, and a true anechoic chamber is 10 times creepier still.

An anechoic chamber is not only sound proof in the sense that no sound gets in or gets out, but it is absolutely reflection free. It has 100% sound absorbing surfaces. It is a most unnatural experience, and most people can't stay inside one for very long; it's just too quiet.

So, you do want some reflection in a room, just as you want a degree of reflection when you hear a live performance. The reflection creates a degree of reverb and gives life to the music. Too much reflection though, creates a cluttered confused performance.

Too much reflection also creates hyper-live spots and hyper-dead spots in the room. In this case, only those lucky enough to be sitting in a vaguely neutral spot hear a good performance. Keep in mind that the peaks and voids don't just occur between the front and back walls, they also occur between the floor and ceiling, and the side walls.

To professionally acoustically tune a room can cost a king's ransom, however, there are common sense things the average person can do to make the room a more reasonable and practical listening environment. And, if you are a somewhat innovative person, most of these things can be done on the cheap.

If you have a dedicated music and movie listening room, you may be able to improve it by something as simple as hanging some cheap curtains on the back wall.

Rob, thanks for the link to more information.

Just a few thoughts.

Steve/bluewizard
 
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Rob Sinden

Distinguished Member
AVForums Sponsor
Hi Steve

I completely agree, you can do a huge amount to improve the performance of your system with curtains, rugs, bookcases etc. Most people clealry cant have dedicated listening rooms but if they are looking for the very best performance then the room must be regarded as important as the equipment used, just as it is in recording studios and classical concert venues.

Electronic room correction is another very powerful tool that can improve even the best acoustic space.

Rob
 

BlueWizard

Distinguished Member
Some thought on electronic room correction.

If you can afford it, electronic room correction can be a godsend. It can make a good room better. In fact, it can likely make a good room near perfect, but it can't fix a bad room. There are some aspects of a bad room that you simply can not correct any way other than literally correcting the room itself.

While I'm not criticizing electronic room correction, I think it is expensive and limited unless you start with a good room to begin with.

Steve/bluewizard
 

richard_t

Established Member
George Lucas wants you to follow the THX standards Tom created, so that you’ll enjoy his films at their very best. Virtually all the other advice you’ll be given about surround sound is given by people who know far less about film sound tracks and are simply trying to sell you stuff!http://www.avforums.com/forums/home...t-professional-system-design.html#post9624643

You're of course correct about the how the environment massively affects the sound of a set up. However to use THX as an example of a company that aren't trying to sell you stuff is utterly laughable.

While I'm sure that isolation from outside noise is extremely important was there really any need for THX to certify a door?

http://www.quietsolution.com/html/pr_quiethomedoor.html

THX Certified Acoustic Materials

10 or 15 years ago Home THX may have actually meant something. These days however their goalposts are so wide that even something such as the following apparently produces sound of THX quality...

Razer Mako 2.1

They're also certifying Home Theater In A Box products such as the Onkyo HT-9100THX which seems to retail for $900. Since THX is all about accurate representation of cinema sound does the fact that something like this is certified mean that this is all that's needed? If it's certified then it must be able to accurately reproduce a film sound track? If so then why would I want to spend much much more on M&K THX Certified products?
 

Rob Sinden

Distinguished Member
AVForums Sponsor
I know THX gets a lot of negative comments in the UK but they led the way in home theatre design.

I'm not saying that you'll get the best system possible sound using a THX system but you will get a consistancy if you adhere to all their recommendations that no other method provides. Buying a top of the range conventional fllorstanding system and putting it in a room will give a much greater variation in performance for example.

I think it was 20 years ago they were advising about room design, SPL's, distortion, dynamic range and EQ and I still dont know any other standards that are so encompassing.

As far as the financial side is concerned I really cannot see the tiny amount they must earn on licencing products is of any interest in comparison to the business of making movies and their merchandising. I believe they set the standards to bring a consistancy to home theatre standards and I don't know of anyone who has done this even 20 years on.
 

BlueWizard

Distinguished Member
I completely agree!

Room correction can't make a crap room sound great but if people can't do any treatment it's the best option - budget permitting.

......and the right room correction will make any system sound better.

I'm not sure I can agree, at least not completely. You can't undo heavy room reflections and the live and dead spots they create. You can't electronically remove standing waves. This is a physical and acoustic phenomenon, and as such must be fixed physically and acoustically.

Electronic room correction is NOT CHEAP. A person would do well to put that same money into literally fixing the room, than in trying to correct problems that can't really be corrected electronically.

As I said, electronic room correction can take a good room to perfection, but it can't really take a bad room any were, because the things that need to be fixed can't be fixed electronically. They can only be fixed acoustically.

Now there are certainly many things that electronic room correction can improve. Equalizing a room for example, making sure the response in the room is as flat as possible. But again, you can't equalize out reflected standing waves.

I think for high end systems, where you want to get the best out of your substantial investment and where you have a reasonably good room to start with, electronic room correction can be a godsend. So, I'm not putting down electronic room correction in general.

Steve/bluewizadr
 
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Rob Sinden

Distinguished Member
AVForums Sponsor
But room correction can be very effective at reducing the peaks that room modes produce. I think this is probably the most common and obvious problem it helps.

People dont realise how much some bass frequencies are exaggerated in their rooms until they can turn the correction on and off. The A/B comparision of this in many rooms is completely convincing.
 

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