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How Much Does A Cinema Room Cost ? Part 3 - Loudspeakers, Subwoofers & Amplification

Choosing a high quality loudspeaker package and amplifier for your cinema room leaves you looking at a vast array of options on the market place. It's probably a good place to start by looking at what we need our loudspeakers and subwoofers to achieve in your room and how we can place them for best effect. We will assume you've read our article on acoustic treatment for your room and it is reasonably well damped and controlled to let your speaker choice shine. Popcorn at the ready !

1. Behind The Screen ? This is the ideal setup when it's possible to achieve. Mounting the front 3 channels (left, right and centre) directly behind an acoustically transparent projector screen will give you the same professional effect that's achieved at your local commercial cinema. The centre channel is primarily there to reproduce dialogue and lock it to the screen so you can understand it clearly. When the brain sees the on-screen action and sound coming from the same place, it's much easier to suspend your disbelief and focus on the voices when there's lots of action sounds coming from the other speakers. If the centre channel speaker is placed above, below or either side of the screen, there can be a disconnect between the on-screen action and the audio that can be subtly distracting, but it's not set in stone. If you don't have the option, there are plenty of ways to "tune" the sound based on your screen size and wall dimensions to give the best effect.

2. Avoid The Corners. This is a common problem with home cinema installations. The left and right speakers get shoehorned into the corners which may at first give you a wider sound stage, but will cause lumpiness in the bass response due to boundary effects. If possible, we recommend placing the left and right loudspeakers in a little more - ideally on an ODD dimension of the wall width. Think thirds and fifths (eg. place the left speaker a FIFTH of the way in from the left wall and the right speaker a FIFTH of the way in from the right wall. Or a THIRD of the way in if you have a larger room - Use a tape measure to get it accurate as positioning can be critical for balanced sound. You can use the same rule for mounting HEIGHT of your speakers - we try and aim for a THIRD of the way down the wall (for wall mounted fronts and rears). Mounting at HALF the room height is best avoided if you want clearer sound.

3. Double Up Subwoofers. A great trick we started implementing many years ago was to use TWO subwoofers in the room. A single subwoofer in a cinema room may produce plenty of low bass notes but will usually sound lumpy and boomy, changing character as you move to different seating positions. The benefit of twin subwoofers will be that they only have to do HALF the work each for the same effect and their distortion will be substantially lower as well because the speaker cones don't have to move so much. You also increase your headroom for very loud bass events. By placing them in different room locations the bass response of the room and listening positions will be smoothed out and more even in character. When listening to high quality music playback you should also notice it's much more tuneful to listen to. It can take a bit of tuning to find the best positions for your particular room shape, but once you have it dialed in you should notice a remarkable improvement in bass clarity and depth.

4. Use the SAME Speakers For All Channels. Another "top tip", don't mix and match your loudspeakers, keep them identical if you can. We often see clients mixing and matching loudspeakers from different brands, some wall mounted or floor standers and even in-ceiling speakers. Imagine a film where a loud helicopter flies 360 degrees around the room, the sound has to come out of all the different speakers in the room and the chances of the character of the sound remaining the same are pretty slim. By using exactly the same loudspeakers all around the room we stand a better chance of having the same acoustic sound signature (timbre) flying around your head and the result will sound much more believable. This results in a much more immersive effect. We don't want the limitations of your hardware distracting viewers from the movie experience.

Additionally, the same loudspeaker will have the same "dispersion" pattern. For a cinema room there is a benefit to having a limited vertical dispersion as this reduces ceiling and floor reflections. This is often achieved by implementing vertically stacked drive units (eg 4 tweeters vertically on the baffle). Larger loudspeakers with more vertical drive units will act more like an acoustic line source and this will benefit rooms with more seats as volume levels will be more consistent from seat to seat (Line source loudspeakers volume reduces less with distance compared to smaller point source loudspeakers). Because we are using subwoofers your loudspeakers only need to go down to about 50Hz, so don't need to be big floor-standers (unless you have a very large room) Typically we will set the crossover frequency of ALL the speakers and the subwoofers at the recommended THX crossover frequency of 80Hz. So speakers that play loud down to about 50Hz should have plenty of headroom. Tiny speakers (eg. at the back of the room for surround duties) can be a compromise, but sometimes are unavoidable. If you have to mix sizes, do so from the same manufacturers range as often the same drive units and cabinet materials are used throughout in different configurations - there should be a similar "family" sound when done this way.

5. Speaker sensitivity and power. The ability to match the loudspeakers to your room is very important if you want the very best sound in your home cinema. Sound pressure level (SPL) is a measure of how loud the sound is - in loudspeaker measurements it's often measured at 1 metre from the front of the loudspeaker with the amplifier set to give out 1 Watt of power. You may see some speakers being specified as having a sensitivity of 88db - that's pretty typical of many domestic speakers. Higher than this and it means your loudspeaker is more efficient at turning the amplifier power into acoustic power. Lower and it means you'll need to feed more power from your amplifier to get the same volume level. Add to all of this the SIZE of your room and you'll see quite quickly that larger rooms require more power output from the loudspeakers and in turn, the loudspeakers may require more amplification to achieve that.

6. More Amplifier Power Than You Need. When we pair loudspeaker and amplifiers for professional home cinema designs we should ensure that each discrete channel has enough power to drive the loudspeaker to reproduce reference level volumes (assuming the loudspeaker is capable of that). Let's for the moment give the amplifier and loudspeaker a simple job - reproducing a 1000Hz pure tone. If the amplifier is under-powered and we turn the volume up, as it reaches it's upper limits, instead of reproducing a nice clean sine wave that faithfully reproduces the 1Khz tone, the tops and bottoms of the wave become flattened off (called amplifier clipping). These flat parts of the wave are effectively DC current and will quickly heat up the voice coils inside your loudspeaker and cause them to burn out. It's much better to have an EXCESS of power in the amplifier so it has plenty of spare power to drive the speaker to the levels we need. Apply too much CLEAN power and the speakers will start to complain as the voice coils hit their end stops, but you should hear this first giving you time to back off the volume levels sensibly. Remember, most blown speakers are caused by under powered amplifiers producing clipping distortion which burns out the voice coils in the speakers.

7. Reference Volume Levels And Linearity. The upshot of these speaker/room/amplifier interactions is that you need to ensure your own intended combination will reach the realistic volume reference levels a home cinema needs to provide an effective reference level experience for the listener. It needs to do this with very low distortion as well. In professional mixing/dubbing theatres it's typical to set the -20db reference point of the loudspeakers by calibrating them individually to reproduce 85db sound pressure levels at the central listening position. That means the 0db reference level (or full volume) needs loudspeakers capable of producing 105db peaks (and 115db peaks for subwoofers which are measured slightly differently) at the same listening position. That's asking a lot for many loudspeakers which is why you'll find professional home cinema designers like ourselves will specify some very specific brand combinations to achieve this requirement. These speakers will play at much louder levels with low distortion. If you manage to get this right then you can be sure you're hearing the soundtrack as the director intended. Listening at quieter levels because your loudspeakers aren't capable of the volume levels required means your ears will be working on a different linear scale, so some sounds may be masked more than others. Your ears don't work in a linear fashion at changing volume levels so it's important to set your room to playback at these reference levels (look up "Fletcher Munson curves" for more information).

8. How Much Should I spend ? For smaller rooms you can often find some budget solutions on the used market that will save you a packet. Look out for THX certified equipment if you can as it will carry some performance specifications with it. You could start with a single subwoofer and add a second when funds allow. For around £1000 you could get a fine sounding solution for a smaller room on the used market. For new equipment we have a variety of suppliers offering cinema packages from £1500 to £3000 typically. Moving up to medium and large rooms, things become progressively more difficult and more consideration needs to be paid to getting the right mix. You will certainly be needing a couple of subwoofers to adequately fill these larger rooms and loudspeakers will need to be larger affairs with scope for higher SPL levels. We often recommend and supply systems by MKSound as well as Klipsch, Meridian Audio, Kef and several others. We're always happy to give advice by email or phone if you want our latest and best recommendations. For a medium size room look at spending £3k to £5k and for larger rooms we can supply systems up from there into the tens of thousands if you are looking for the very best sound in your room. Quite often, some of the largest rooms may require multiple subwoofers and even several extra channels for multiple surround sound speakers and even overhead Dolby Atmos speakers. For the ultimate cinema rooms we recommend Procella Audio systems which can cost from £50,000 and up.

9. How Will It Sound ? Well, if you follow our recommendations above, you'll be surprised how good a professionally designed and installed home cinema can sound - often much better than commercial cinemas (where we're not trying to please a few hundred people at the same time). Played at the recommended reference levels, a low distortion combination of room, amplifier and loudspeaker won't stand out as being loud - you'll be surprised how the volume level can be turned up without sounding at all harsh or unpleasant. In fact, quite the opposite! The sound should float around the room seamlessly and surprise you with its' subtlety and ambiance. You'll be hearing sounds deep down in the mix you hadn't picked up on other systems. Now you can sit back in your luxury cinema chair and revel in your favourite movies in your own bespoke home cinema. Enjoy the popcorn !