Saturday, April 05, 2008

sound advice 2

Listening, Speaker Placement and Room Dampening

I’m sorry it’s taken me so long to post no 2. I’m also off to Beijing tonight and so possibly won’t even be able to access blogspot due to censorship, for about the next 10 days.

The practical exercises herein require no one else in the house except you and your helper for a good 4 – 5 hour afternoon. The helper will need to be a sympathetic audio nut or a beginner nut. You will need the house empty not only because you will be playing strange bits of music and odd sounds but you will be doing some things that may appear stupid to an audio philistine and having to explain will be unrewarding. From much experience I can warn that this can easily turn into a 12 stubby job for two. Non drinkers should stock up on good coffee, biscuits and Lapsang Souchong.

I classify listening into two categories:

1. Active listening – where the listener is in their lounge room or similar and concentrating almost exclusively on the sound and is seated about 6 (1.8m) to 10 feet (3m) in front of the speakers in a sweet spot. (Most headphone listening is active.)

A subset of active listening, which I think is underutilised by household listeners, is Nearfield Listening. Nearfield listening is what recording studios use for monitoring and playback. The speakers are usually smallish or bookshelf size and placed anywhere from 6 inches (.15m) to 2 (.6) feet apart. The listener is not usually more than 3 feet away from the speakers. This tends to minimise many room effects and give a better sound at a lower volume.

I use this in my office with two Yamaha NS-10s on a shelf at ear height and about an arms length in front of me. (NS-10s are of course famous – mine cost me a slab of green tinnies). Nearfield listening and speaker placement can also work well for those in flats and or small rooms. Sitting close to speakers saves space and will allow lower volumes. You can even do this with your existing speakers (or those in a shop) to get an idea how they sound with minimal room interference. Just bring them to within one foot of each other, toe them in and drag a chair up to about 3 feet away so that you ears are roughly at tweeter level.

2. Everyday Listening – where the listener is in the room but perhaps wandering around to different rooms or reading or writing or eating at a table but not in the sweet spot. Most people, including me, do most listening in this mode. This is louder and more involved than background listening. Background listening is low volume and incidental. The effect is a bit like lift muzak. I generally disapprove of background listening but will sometimes have FM classical on very low.

One of the most common mistakes made in sound is speaker placement. It is also the easiest to fix and the most likely to make a difference in sound.

Whilst it is true that the room probably has the most impact on sound, the fact is that most of us do not have the luxury of a purpose built dedicated listening room. Generally the sound system is plonked in the lounge or living room and juggled around furniture, views, fireplaces, TVs, pathways, heater vents or partner needs.

In the ideal audiophile’s view, and in most hi-fi magazine articles, the listening room is at least 25 feet (7.6 m) X 20 feet (6m) and dedicated almost solely to the hi-fi setup. (Many American audio nuts seem to have much bigger rooms usually in the basement.) These rooms are well suited to large floorstanding speakers and need largish speakers with big woofers to fill the room properly.

Speakers consist of an enclosure (the box) and drivers (commonly called speakers) and a crossover or possibly more crossovers. In oversimplified terms: Drivers are the smallest called tweeters, which carry the higher sounds, midranges which carry the mid sounds (voices etc) and larger woofers which carry the low sounds. Subwoofers carry even lower sounds. Crossovers essentially separate out the signals and send high sounds to the tweeters, mid to mid and low to woofers. It’s not quite that simple but that’s the essentials.

The art and science of good sound is basically in the crossover design and the calculation of enclosure volume for the drivers. Despite all the marketing spin drivers are a mature commodity and very few speaker brands make their own. The well known Scandinavian driver manufacturers turn up in many top end brand speakers which incidentally is what makes speaker do it yourself kits with well designed crossovers extraordinary value. But more of that later.

Most speakers these days will be two way. That is they will have two drivers - a tweeter and a combined woofer/midrange. Older or floor standing speakers commonly are three way -one tweeter, one midrange and one woofer. Home theatre set ups commonly have a sub-woofer.

Think of the tweeters as relatively directional, that is the sound will travel in close to a straight line from the tweeter. Think of midrange / woofers as relatively non directional. Following on from this it is obvious that the tweeters should be at, or slightly above ear height when seated in the ideal active listening position. For most people that will involve raising the speakers off the floor. If you have bookshelf speakers you may eventually get proper stands but for the time being use anything solid to raise the tweeter height to ear height. Milk crates (all music lovers have a cache of milk crates) or small tables or even bookshelves. Bookshelves aren’t the best as we will see a bit later.

There are many complicated formulas for setting up speakers in a room which I will provide links for later if you are inclined but basically it boils down to having the speakers themselves about 6 feet apart and the listener at the apex of a triangle about 8 to 10 feet in front. Toe the speakers in a bit to aim the tweeters at about where the listeners ears might be. Depending in the size of your head and ears that should be around 8 inches apart at the listening point.
If at all possible the speakers should be a meter from any side wall and a meter from the rear wall. In most modern rooms this just isn’t practical but try as much as possible to have speakers away from walls.

Start off with the speakers a meter out from each wall but just say about sic inches away from each other while you sit directly in from about 6 – 8 feet away with tweeters at ear height. Get helper to move speakers slowly apart to eventual 6 – 8 feet apart while you listen.

Get your helper to move the speakers in toward each other and out and at slightly different angles whilst you sit and listen. At some point in the process you will begin to hear and understand stereo imaging and there will be a sweet point when the sound has some depth and seems to come from somewhere in the middle of the two speakers rather then from each speaker. Mark your listening spot and the speaker spots with something like blu tac or chalk on the floor not texta. It is most likely that this set of spots is not practical due to everyday use and other family members. But keep it marked as you will eventfully try to slyly creep to this arrangement over the next few months.

You will of course have been playing some well chosen music or sounds that has a good stereo image and a bit of depth. I can recommend any of the test discs from Chesky which these days usually also contain a good selection of well produced jazz music as well as test sounds.  JB will have some at times.

Another extremely useful and supremely enlightening fiddle you can try now is room damping. Ths is where mny advice to have house empty will be appreciated.

Music will reproduce best where the room sound is flat and the room provides little or no additional echo or bouncing of sound waves around the room. (There are exceptions but this is a basic rule). Notice how a radio studio always is dampened and dead and how the music from the studio speakers sound great. Or a recording studio is similar.

Now most people cant realistically have a dead listening room but you need to hear your speaker at least a few times with the room as dead as possible in order to see if perhaps you speakers are ok and not really in need of replacement. Anyway, after this exercise you will be constantly seeking to deaden the room.

If the floor isn’t carpeted throw as many rugs as possible on the floor especially in front of the speakers to cover floorboards or tiles. Grab as many doonas and blankets as you can and somehow get them around the walls around ear height. A good but embarrassing way to prop them up is using brooms and sticks to prop up doonas on the walls. Or hang carpets from picture rails. Crowded book shelves also work well. The object is to cover all the floor and surfaces up to a bit above ear height or higher with soft sound absorbing material.

Now sit down and listen properly to a well produce bit of music for a long time – at least and hour. Your speakers are now in the best environment to perform for you.

Listen to see if they can reproduce a bass well – tightly without booming, listen to hear if the mid range reproduces voices guitars and piano well. Bad speakers will have a booming or non existent bass. The hardest bit to get right is the mid range. It seems to me that these days the emphasis is all on tweeters and woofers and midrange is ignored. Most cheaper and even a lot of the more expensive home theatre sound is all high end and low end with no midrange. You will find that this combination is fatiguing as well as missing out the wonderful sound of voices guitars and pianos.

If you have done all the above this last hour or so will be your peak experience with your current system. It is pointless getting new speakers without going through all this set up. Naturally you probably can’t leave the doonas and speakers and seats exactly where they should be forever. But you can know that this is where you are aiming and gradually dampen the room with furnishings like couches, carpets, wall hangings and book shelves full of books.

You will find that if you do the above even a crappy old all in one stereo will sound better than expected. It will even improve a boombox.

Good listening. Link to a page of mad speaker links to keep you busy for hours.

Next up in the series Choosing Speakers and perhaps fixing up good old speakers and I would like to do a list of true hi-fidelity recordings. Perhaps commenters could throw in a bunch of suggestions.