Acoustic Room Treatment

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November 26th Written by 

Common wisdom in the world of high end audio has long held that the two most important components in a high fidelity audio system are the loudspeakers and the room. In an era of very high quality digital sound sources and mid-priced receivers which can blow the doors off many mega $ audiophile amplifiers of just 10 years ago, this is more true than ever.

Loudspeakers are dealt with extensively on our site. Obviously we feel wide dispersion Ribbons, whether in classic two way or the ground breaking Coaxial Ribbon LineSource configurations, are the best answer for most listeners in most rooms. The LineSources in particular can work well in some exceptionally large or irregular spaces. 

But great loudspeakers can’t overpower terrible room acoustics and it is here that a little thought can yield great sonic payback. Room acoustics is really the management of reflected sound and the minimization of room dimension dictated “modes”. Some reflected sound is good but too much and from the wrong direction can be degrade soundstage coherence and create listening fatigue. 

Limited reflected sound from the side walls can enhance the high fidelity experience while sound bouncing off the ceiling, floor and back wall almost always degrades the soundstage and results in listening fatigue.

One of the reasons large Ribbon and electrostatic loudspeakers have gained their vaunted reputation in the audiophile world is they have very limited vertical dispersion so they automatically minimize floor and ceiling reflections. This is contrasted to dome tweeter based systems which radiate hemispherically and therefore push sound in all directions almost equally. 

There are a number of ways to tame room reflections. By tame, we mean arrive at a satisfying ratio of direct to reflected sound, not create a totally dead anechoic chamber. Managing reflected sound actively is done by damping the surfaces which reflect the sound. Passive management is achieved by moving the listening position and loudspeakers closer together so the path length from speaker to reflective surface to listener becomes much longer than the speaker to listener path distance. In acoustics, the further a wave has to travel, the weaker it gets. 

There is a listening distance which is best for each room and each listener so experimentation is necessary. Too much reflected sound is unlistenable and too little is unnatural. 

Reflected sound should be equally balanced from each side. This is often the most difficult thing to do since many rooms have an open side or the sound system has to be installed off centre. If reflected sound can’t be equalized, then the overall side to side balance will have to be tailored using speaker toe-in and possibly the balance control. Acoustic symmetry is the key. 

Sound reflections occur at all frequencies. Treatment for low frequencies (long waves) is different from that for midbass and higher frequencies. Very often effective room treatment can take the form of putting furniture, plants, bookcases and tapestries in the right position. Or by installing heavier drapes or blinds. 

Stuffed furniture and bookcases (filled with books) absorb sound, hard furniture breaks up reflections. Plants do a little of both whereas drapes form variable dampers as do doors which can be opened and closed depending on the sonic effects they create. 

Beyond these common in-room devices, home made damping can be provided in the form of blankets propped up by 2x4s or hockey sticks and small mattresses and pillows placed for maximum effect. (Usually behind the listening position if a rear wall is close). 

Of course, there are professional products readily available to do a first class job once you have determined the final approach. These products will also come with expert opinions if you purchase at the right place and hence will be vastly more useful. 

There are many room treatment companies. Here are three. You can discuss bass traps and slap echo damping. 

A company with a lot of experience and a great product selection. 

www.auralex.com 

If you are looking to design your room from scratch, ASC will have some material and advice useful for soundproofing. 

www.asc-home-theater.com 

And the old audiophile favourite which has helped many an audio company over the years (including Newform) wrestle audio show room acoustics to the ground. 

www.echobusters.com 

A prime consideration in room acoustics is keeping your walls quiet. If the drywall or the floor moves or rattles, they will add resonances which are very hard to deal with. Keep your walls, floors and ceiling solid! 

Of course, there are nearly ideal rooms which require an absolute minimum of work. If you are lucky enough to have a rectangular room maybe 14' to 18' wide x 24' or longer, consider yourself acoustically blessed. Concrete floors, walls and ceiling? Even better. 

A nice long room guarantees that rear reflections will be weak in which case the soundstage will really have a chance to become well defined. Damping on the rear wall can go a long way to sonically replicating a long room. 

Room modes are dependent on the placement of the speakers and the location of the listening position. Varying these can either minimize the mode or shift it out of the listening area. In some rooms though there can be wicked peaks and suckouts which will not be dealt with by mere speaker placement techniques. 

We find that only about 25% of our audiophile customers have great rooms. The rest of us have to work a little harder. But treat your listening room appropriately and it will treat you to many years of musical bliss. 

Loudspeakers Unsurpassed in Soundstage, Transparency, Detail and Dynamics in High End Stereo and Home Theater Systems

Read 4126 times Last modified on Wednesday, 25 December 2013 16:23
Published in Audio Planet
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