Friday, December 6, 2013

High-end Soundstages - Part 3

Once the sophistication of audio playback systems rose to a quantum level revealing the ability of two loudspeakers to recreate a 3-dimensional soundstage, it quickly became clear that room shape, loudspeaker positions, sonic treatment, and location of the listener all interacted with each other in a synergistic way that not only influenced the size and shape of the soundstage but also the level and smoothness of the system’s perceived response. Someone once said, “The devil is in the details…” and with audiophiles, they seek out those details, the room/speaker relationship being a big one.

The vast majority of audiophiles initially recruit an existing room in their home in which to listen to music. This room (appropriately termed the listening room) is often a choice of convenience rather than that of optimum design. But this begs the question:

Which room will most likely give me a good sound stage?

From this point on, we will explore five basic rules that apply to most situations calling them a “RULE NUMBER…” but as rules go, they are all made to be broken, so keep in mind that what works for your friend’s home may not work in yours. The best thing you can do is to experiment and I will point out ways for you to do this and things for you to listen for while making your adjustments. I use an approach that requires you to take notes and keep track of what you tried so from this point on, grab that tablet, find a tape measure, get some masking tape, and let’s get started.

RULE NUMBER ONE: The best choice for a uniform soundstage is to select a room with symmetrical walls at the end of the room in which the loudspeakers will reside. Whenever possible, this should also be the short wall of this room (listen through the length of the room rather than its width).

As I mentioned, rules are made to be broken and if you have no other choice, use what you have. Good results can still be achieved in non-ideal rooms when understanding where to begin.

 Best Orientation (Left) of Same Ratio Rooms

Guidelines for optimal-shaped rectangular rooms based on ceiling height use what is called the “golden rule” of dimensional ratios. This rule states that – all things being equal – to keep room resonances under control, the dimensions of a listening room should closely align with this ratio: 1:1.62:2.62. For various ceiling heights, these rectangular room dimensions are:

Ceiling Height
Room Width
Room Length
7’ 6”
12’ 2”
19’ 8”
14’ 7”
23’ 7”
16’ 2”
26’ 2”
17’ 10”
28’ 10”
19’ 5”
31’ 5”

If your ceiling slopes, take the average height of the ceiling (this of course is not precise but it is a good guess). For example, if your cathedral ceiling slopes from 8’ to 10’ and back to 8’, estimate your ceiling height to be 9’. For highly irregular vaulted ceiling heights, you will just have to give it your best guess.

RULE NUMBER TWO: Listening should be the main purpose of this room and the speakers should occupy about 1/3 of that room.

This seems to be a logical assumption but many people try to do too many things in one room. Multiple hobbies end up taking up floor space and if this is the case, it is better to clutter up the listening end of the room as opposed to the speaker end. Just keep the clutter at a reasonable distance from your ears and things should work out fine. We will see how these other things can be arranged to actually enhance the room’s effect on the sound, but more on that later.

RULE NUMBER THREE: Make an accurate drawing of your listening room. If you do this with paper, make a “master copy” that you can reproduce on a Xerox machine and not have to redraw the room over and over again. Simple graphics programs are really useful in this analysis and these programs add-up dimensions to allow you to make accurate dimensions of everything. Verify these measurements after your floor plan is done. Make several copies to try out different arrangements.

Regardless of what dimensions your room has or the orientation you must use, the next question would be: exactly where should you locate your speakers?

RULE NUMBER FOUR: There is another pair of “golden rules” about positioning speakers that uses the width dimension of your listening room (that is, the wall behind the loudspeakers regardless if it is the length or width of the room). Regardless of the ceiling height in your listening room, this Rule Number Four explains how far away the center of the woofer should be from the side walls. This rule is Room Width times 0.276 (Ds = RW x 0.276) and the table below explains where the center of your woofers should measure from the wall to the left or right of it. Each speaker should be roughly this distance from the side wall nearest to them.

Room Width
Woofer Center to Sidewall
2’ 9”
3’ 0.5”
3’ 3.75”
3’ 7”
3’ 10.5”
4’ 1.75”
4’ 5”
4’ 8.25”
5’ 3”
5’ 6.25”

For example, if your room is 14 feet wide, Ds=14x0.276=3.864 or roughly 3’ 10”. Note that this is not the distance to the center of the cabinet but to the exact center of the woofer. You do not have to take off the grills to your loudspeakers to make this measurement more accurate. Start with as best of an approximation as you can figure since later you will move your speakers around anyway trying to find that “perfect” place.

RULE NUMBER FIVE: This rule describes the distance from the center of the woofer face to the wall behind the speaker.  This rule is: Room Width times 0.447 (Df = RW x 0.447) and the table below explains where the center of your woofers should measure to the wall behind them (called the Front Wall since you will be looking right at it). Both speakers should be this distance.

Room Width
Woofer Center to Front Wall
4’ 5.5”
4’ 11”
5’ 4.25”
5’ 9.75”
6’ 3”
6’ 8.5”
7’ 2”
7’ 7.25”
8’ 0.5”
8’ 6”
8’ 11.25”

For example, if your room is 14 feet wide, the distance from the woofer center to the sidewall (Ds) is about 3’ 10.5” and the distance from the woofer center to the front wall (Df) is about 6’ 3”.

Calculated Loudspeaker Positions Based on Rectangular Room Width

This is a great starting point for your speaker positions. However, life has its compromises and the one typically made in a family home is to make the distance from the front wall to the woofer face much, much shorter. If you must concede optimal placement for convenience, my advice is to move your speakers as far out into the room as possible and make final front-to-back adjustments from there. The further forward your speakers are toward the optimal distance (Df), the deeper (front-to-back depth) the soundstage should be.

YOU'RE NOT DONE... It’s time to get out the masking tape and mark the spots on the floor where your speakers now sit. Before hooking up your speakers to your amplifier, do the following: 

  • Use your tape measure and record the current positions in your tablet. Make several measurements from corners of the speaker cabinets to the side and front walls. You will use these measurements later when you compare various placements and writing down what you observe at each position helps you to know if you are moving them in the correct or incorrect direction.
  • Put your speakers on stands so that the center of the midrange driver is at the center of your ear height while sitting in the sweet spot. Have a friend help you determine this height and remember to measure the height of your spouse's ear too (please substitute whatever word you use for the politically correct term in your situation). With spouses, a mathematical average between these two ear heights is always a good compromise.
  • Use speaker stands with firm connections (spikes) to the floor and speakers. FOR NOW, DO NOT PRESS THE SPIKES INTO THE FLOOR. In Part 4 of this series, you will move these speakers a little bit at a time to find the best location for your room.
  • Re-measure the location of the speakers on the stands so that the positions measured from the side and rear walls are still correct. Move the speakers and stands accordingly until these locations are again confirmed to be correct.
  • If there are bare wood floors between your speakers and your listening position, put a large soft decorative rug between the two. Coordinating decor with function is a great idea.
  • Sparingly add furniture back into the room on the listening-end of the room only. You will be tempted to add end tables, bookshelves, pictures, and the like but for now RESIST THE URGE TO DECORATE.
  • Now connect the speakers to the amplifier.

Know that this masking tape will only be on the floor for a short while so that final adjustments to their positions can be made more easily.

Speaking of final adjustments, Part 4 of this series describes exactly how to “tweak” your speaker positions based on furniture arrangements, doorways and hallways, and similar issues. I will explain how to use regular music and describe what to listen for as you move your speakers around to get the best sound possible.

For now, be patient. Put your listening chair centered between the speakers so your ears are about the same distance from the rear wall as the woofer faces are from the front wall (Df) and enjoy the 3-D illusion of a good wide, high, and deep soundstage! Things will only get better from here!

Links to the entire series:
Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7
Yours for higher fidelity,
Philip Rastocny 

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

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