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Decibel Dungeon
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When we describe the hi-fi system as a 'chain' we shouldn't really describe the loudspeakers as the last item in that chain. That title falls to the listening room (or is it the ears, brain....?).
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The listening room is really an extension of your loudspeaker system. It is one of the factors accounting for the differing performances from the same 'speaker. If you want to discover how much the room affects your 'speakers, just set them up in your garden and hear how different they sound. So by altering the listening room, we can adjust the sound of our hi-fi system.
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So how can we change our listening rooms? Well ,you'll be glad to hear that you don't have to move house although, you may benefit from choosing another room in your home as your listening room.
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Here is a list of features for an ideal listening room:
- It should not be too small but nor should it be too large for the 'speakers which you are using. Smaller 'speakers will have a hard time filling a very large area with useful amounts of bass.
- It should have the right proportions. The worst shape is where all the room dimensions, height, width and length are the same. In that situation the sound waves all bounce off the room boundaries and meet in the centre of the room at the same time (because they have travelled the same distance). This causes an uneven sound resulting in some frequencies (particularly bass) being favoured. This is one of the causes of a boomy bass. Ideally, it should have no parallel surfaces but you will be lucky if you have such a room in your home!
- It should allow you to place the 'speakers in the optimal position with regard to the room boundaries and your listening position. This optimal position depends on the 'speakers and although there is some theory to get you started, it is best found by trial and error.
- It should be furnished in such a way that it does not overly affect any particular frequency range. Carpets and soft furnishings will help reduce bass boom and echo but too much will cause the mid-band and treble to disappear.
- The walls will be solid rather than the partition (hollow) types.
- The walls will ideally have features (pictures, moulded wallpaper, ornaments) which help break up standing waves.
- The room will not contain any items which will rattle or resonate in sympathy with the music causing unwanted sounds.
- It will be comfortable. Sounds obvious but some people pay so much attention to the hi-fi, they forget that listening to the music is meant to be pleasurable.
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Even if your room is not the best shape or size, and you can't move to another room (or home), there is still quite a bit you can do to get the best sound from your system. The following suggestions are made on the assumption that you have a free hand to do what you want in the listening room. Although I live on my own, I am aware that others have to make compromises to avoid conflicts with their cohabitors.
- Look at the layout of the room. Can you re-arrange the furniture? Is your hi-fi in the best position or is it made to fit in with everything else? If you can, try different arrangements until you find the best sounding one.
- Look at the amount and type of soft furnishings in the room. Try adding or removing them to see what effect it has on the sound. If your flooring has hard surfaces try placing a soft mat between you and the 'speakers.
- When your hi-fi is playing, move slowly around the room and see if you can hear any noises coming from windows, mirrors, ornaments or anything else which can resonate or rattle. This exercise is ideally done with a source containing test tones of varying frequencies. Once you have located any unwanted noises, see what you can do to stop them. Solutions include:
- Remove the offending item from the listening room (or try it in another part of the room.
- Damp the item. Try putting sand in ornaments with cavities or something compliant between ornaments and the (hard) surface which they stand on.
- Fix loose windows and doors.
- Don't forget to look at the walls when you are optimizing your listening room. Large pictures with glass and mirrors can cause problems by reflecting higher frequencies. Large areas of plain wall are best broken up with anything which will do the job and not look unsightly. This particularly applies to areas of the wall above the height of your ears while you are in your usual listening position.
- Look at your listening position. It should be on the opposite side of the room to the 'speakers and centred between them. Allow at least half a metre between your head and the wall behind you. Remember that a well-upholstered arm chair will soak up some of the sound (more so if it has a high back).
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If you need to convince someone that a good hi-fi needn't be intrusive, click HERE .
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Stephen Robinson has some further suggestions for improving room acoustics (and supporting equipment) on his very interesting Izzy-Wizzy site.
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I have found from experience that one of the biggest improvements you can make to the sound of your h-fi is to get the 'speakers positioned correctly. It is well worth the time and effort to get this right, but, if you have large, heavy 'speakers, it could mean a lot of effort!
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Below is a diagram of an imaginary listening room showing the correct positions for the 'speakers and listener.
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D1 = distance between 'speakers
D2 = distance from line joining 'speakers to listening position
D3 = distance from listening position to wall behind
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The 'speakers should be placed a minimum or 1.5 metres apart (D1) and depending on their size and type (sealed box, ported, horns etc) should have a certain amount of space between them and the rear and side walls. The distance from an imaginary line joining the two 'speakers to the listening position (D2) should not be less than the distance (D1) between the 'speakers.
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Unless the 'speaker has been designed to go right into a corner, it will cause problems if placed in one.
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Most (but not all) 'speakers benefit from being 'toed in'. This is where they are placed at an angle so that they face in toward the listening position. The amount of toe-in is critical and can only be found by trial and error. A good starting point is to have the 'speakers angled in so that imaginary lines coming from the front of the cabinets would cross each other just in front of the listening position.
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 - After going around in circles, trying to find the correct position for my 'speakers, I decided to take a more methodical approach. The problem was that I didn't have an accurate way of recording the exact positions I had tried previously. To overcome this, I constructed a useful tool.
The tool is made from two strips of timber, each about a metre long. These are bolted together at one end so that they make a sort of protractor. Use a wing-nut to enable you to loosen and tighten the bolt by hand. A scale is marked on both sides of both strips, and these, together with a reference point marked on the rear wall, enable me to record the precise position of the 'speakers. Not only can I work out the distances from the side and rear walls, but I also have a record of the 'toe-in' angle. As a bonus, the protractor makes it easy to position both 'speakers symmetrically.
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Using the 'protractor' to position a 'speaker
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There are two other considerations when positioning the 'speakers. The first is to get the height correct. The tweeter should be level with your ears (when you are in the usual listening position). I have also found that the vertical angle of the 'speaker affects the sound so it is a good idea to have some method of altering it. If you have adjustable spikes on your 'speaker stands or cabinets, you may find that this provides enough adjustment. If not then you could try getting some longer spikes, or using some wedges to provide greater adjustment.
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Remember to leave a minimum of half a metre between your head and the wall surface behind you (D3).
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Trying to get a pair of 'speakers positioned correctly, with the correct 'toe-in' angles, vertically aligned at the right height may seem like trying to find a needle in a haystack. However, if you build yourself a 'protractor' and take your time, perhaps limiting your trials to one movement each day, you will eventually find the best arrangement and find that it makes a worthwhile improvement to the sound quality of your hi-fi.
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- You will find it much easier to establish the optimum set-up for your hi-fi system if you use a test record or CD. These contain tracks which are designed to help you get the best from your hi-fi. I use the Hi-Fi News and Record Review (HFNRR) test CD which you can read about HERE.
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Finally on this subject, a few words about 'bookshelf' 'speakers. These are the very small 'speakers which we are told are designed to go on a bookshelf. No doubt some of them will work reasonably well on a shelf and many are designed so that their placement up against a wall will help their (bass) performance. However, placing a 'speaker on a shelf, or on the wall using a wall bracket, obviously limits the possibilities for experimentation.
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SOUND STAGE - When you listen to a good hi-fi, you should be able to perceive a three dimensional area around your 'speakers which we call a sound stage. This should extend well outside the actual 'speakers, both in width and depth. To get depth, the 'speakers need to be positioned well forward of the wall behind them.
IMAGING - an audio 'picture' of a sound source, eg a singer or instrument. In a good system you will be able to clearly perceive where this is situated within the sound stage.
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With a few notable exceptions like the famous BBC LS3 monitors, 'bookshelf' type 'speakers are not considered audiophile quality and are probably best avoided unless you are very limited for space. It's not that small 'speakers cannot perform well, they can if used with a sub-woofer, but confining them to a position against a wall is likely to limit their performance as regards certain qualities like the depth of sound stage and imaging.
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Although less critical as regards the sound quality of your system, having the rest of your hi-fi located properly is also important.
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In theory, you could place your source component(s) and amplification almost anywhere in the room and, providing you have long enough cables to connect them to your 'speakers, the hi-fi will work. In practice things are a bit more complicated.
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In the section on hi-fi cables, we looked at how different cables can affect the sound of our hi-fi systems. It makes sense that the longer the cable, the more it will affect the sound so it is best to try and keep all cable lengths as short as is practically possible. Even the sceptics who disagree about the affect different cables can have on sound quality, agree that shorter is better. For that reason, the optimal position for hi-fi equipment is between the two 'speakers. In theory, if you have placed your 'speakers two metres apart, then the 'speaker cables from the amplifier need be little more than a metre long. Of course, for aesthetic and safety reasons, it is not practical to run cables in a straight line from amplifier to 'speaker so we must also consider the extra length needed to route them sensibly.
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Now if the length of cables was our only consideration, we would be 'home and dry', but unfortunately we also have to think about another hi-fi problem, that of ensuring that the equipment is not affected by unwanted vibrations. These can be transmitted through the air from the 'speaker cones or through the floor, and, to a lesser extent, the walls. Obviously , the closer your equipment is to a 'speaker, the more susceptible it is to these vibrations.
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We could 'retreat' to the opposite end of the room but then we are back to the long 'speaker cables. Should we compromise and have the equipment half-way across the room? Or could we use wall-mounted equipment racks which would minimise the amount of vibration coming from the 'speakers through the floor (but not through the air)? I can only describe my set-up which seems to work quite well (after much experimentation) and should give you some guidelines to setting up your own system.
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I prefer the 'shortest cable' option and have spent my time trying to minimise the vibrational effects from the 'speakers. My equipment is sighted between the 'speakers in a bay window, on low stands. The power amplifiers are housed in wall-mounted boxes, immediately behind each 'speaker. My turntable is mounted above one of the amplifiers.
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My listening room has a suspended wooden floor and I have made the following modifications to minimise the problems caused by vibration:
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I have found that despite being situated immediately behind a 'speaker, the turntable does not seem to be adversely affected. This may be due to the design of my turntable where I have gone to some length to combat the problems of vibration. As it is the only practical location, I don't have much choice as regards repositioning it. (You often find that you have to make some compromises with hi-fi)
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I firmly believe that wall-mounting is preferable to floor-mounting for hi-fi equipment from the sound quality point of view. Of course, there are reasons against it:
- It may be unsightly
- You may not want to drill holes in your wall
- There may not be the space
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The first objection can be partially overcome with some careful design. In the case of my power amplifiers you can see that they are not visible, the cabling hardly shows, and the 'box' is a not unattractive shelving unit.
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So, assuming that you have now decided where to position your equipment, what is the best way of supporting it?
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As with cables, there has been much argument about the best way of supporting the electronic equipment used for hi-fi. And, of course, there have been many wild and wonderful theories, mostly emanating from those who were trying to sell their 'ultimate' equipment supports.
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One of the fundamental questions is whether the equipment should be coupled or decoupled to the support and/or floor/wall. Some favour decoupling and go to great lengths to achieve it, even hanging their equipment on bungies from the ceiling!
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And then there is the question of whether spikes couple or decouple. I've asked this question of several 'experts' and have never received a satisfactory answer. What does it matter? Well, we have two main considerations with equipment supports. One is trying to prevent external vibrations from getting into the equipment. This is very important with source components like turntables and CD players, less so with amplifiers and tuners etc. At the same time, we also want to have some method of draining away the vibrations produced by the equipment itself.
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The problem is, if we manage to completely isolate a piece of equipment from external vibrations we have then effectively cut off the path by which we can drain away the internally produced vibration. I wish that I could now write a concise and easy to understand essay on how energy travels through mass and how to control vibration. However, I have searched the internet for an easily understandable explanation but have yet to meet with any success. So, as usual, it's down to experimentation and what I have learned with my own system.
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One thing I have found is that just throwing loads of mass at the problem and hoping that this will 'sink' the unwanted energy, has its drawbacks. It would work if the energy entered the mass never to re-emerge (or at least not until we have finished listening). However, the energy is only temporarily stored by the mass, and then released causing a muddling of the sound due to the delay caused by the time it takes the energy to pass through the mass. Remember the scientific law that energy cannot be destroyed, only changed!
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In my experience, the effect of using a large mass ( under a source component) manifests itself in poorer timing, making the music appear slower. I have encountered this effect on several occasions with 'speaker cabinets, 'speaker supports, equipment racks and even the supporting shelves under equipment so I am fairly confident that this is not the way to go.
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Equipment supports obviously need to hold equipment securely so my recipe for racks and supports is 'light and rigid'. I prefer to use wood to metal as:
- It doesn't 'ring' like metal so doesn't need damping.
- It is easier to work with.
- It tends to look more acceptable in a domestic setting.
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I haven't had the time or money to experiment with different types of wood, often using what is available at the lowest cost. A friend who works with wood recommended I try some tulip wood, a cross between soft and hardwood with a straight grain. This is what my equipment racks are now built of.
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The racks are spiked to the floor using home-made spikes. These I make from threaded rod which I grind to a point at one end. The other end is inserted into a T-nut; a plastic disk, bolted to the spike acts as a thumb-wheel and facilitates adjustment. I know that hardened steel is deemed better for this purpose but it would make construction much more difficult without the right tools to fashion it.
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Home made spikes
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Each piece of equipment sits on its own support which in turn sits on the 'arms' of the rack. I use standard wood screws to 'spike' the supports onto the 'arms'. This also allows for accurate levelling of the support using a screwdriver.
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So we know where to place the hi-fi equipment, we have decided on the type of rack to place it on but we're not quite finished yet. There are two more stages before we have finished this job.
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The first is to decide what exactly the equipment will sit on. And does it matter? I once carried out an experiment to find out and I was quite surprised at the outcome.
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At the time, I was using a wall rack for all my equipment, I decided to try placing different sheets of material underneath the CD player. I had to hand some MDF, block-board, 6mm glass, 3mm aluminium and 20mm marble. To my surprise, I was able to distinguish differences in the sound when I changed one type of material for another. The glass sounded brighter, the marble duller. There was little to choose between the other three but I eventually decided that the best solution was the block-board (which is lighter than the MDF).
Update 2007. I now have no doubt that granite is the best material to have under a piece of hi-fi! But much depends on how the equipment is coupled to the granite, and how the granite is decoupled from the stand.
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I've have been using block-board since that experiment. Occasionally I have been tempted to try the marble again (mainly for cosmetic reasons) but have always gone back to the block-board. It's not a question of better or worse, more what works well with your own equipment but I repeat, I don't think that high mass has a place in a support system, particularly to support CD players or turntables.
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So, we're nearly there. Just place the equipment on the support and that's it. Well, not quite that straight forward because there's one last option to be dealt with.
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The last choice is: what do we place between the equipment and the support platform? And these are the options:
- The feet which come as standard with that piece of equipment
- Metal spikes
- Cones, either metal, ceramic, carbon-fibre, wood, plastic
- Compliant feet made from rubber, sorbethane or some other 'squidgey' material
- A partially inflated inner tube
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Once again, I have spent probably more hours than I should have on trying out just about every option. I've tried four 'feet' and three, inflated inner tubes, and other different compliant materials. My preferences were for the non-compliant types of feet, particularly the cone types.
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I am currently using an arrangement based on an idea given to me by a friend. It is the basis of a forthcoming commercial product and I have agreed not to divulge the exact details. All I can say at present is that experimenting with how you support an item of hi-fi on its platform can pay huge dividends!
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I haven't been tempted to play with any part of my support system for quite a while now, a sure sign that it is working well. I hope that the above information may save others at least some of the time I have spent experimenting on this part of my hi-fi.
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Update, 2007. My system is now much changed and I have recently built a version of the TNT Flexy Table from threaded rod, plastic pipe, and MDF.
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- If you really must have , or better still, granite to put under your hi-fi, go to somebody who produces fire-surrounds. They often have a stack of marble slabs which they cut from surrounds (the bit where the fire goes). In my experience they are glad to get rid of these 'off-cuts' for what ever they can get for them. I paid just £5 for pieces 430mm by 300mm including a polished front edge!
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Some very sound advice on listening and setting up your speakers can be found on the Tips and Tricks page on the Vertex AQ site!
A good read on the theory of controlling vibration.
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