Monday, December 16, 2013

High-end Soundstages - Part 6

In Part 6 of this series we will start moving things around and improving upon what should already be an enjoyable experience. As mentioned earlier, the advancement of the high-end is a process, not an event. Many pieces of gear have most likely come and go in your upward quest for audio nirvana and the typically overlooked element is your speaker positions. When something is “not right” about the sound of your rig a trip to your local audio salon finds its way in your weekly “to do” list. Without a doubt changing equipment has the biggest impact on the overall sound of your system, but the position of your speakers has the greatest impact on the size and shape of the soundstage (and the smoothness of the bass).

Many may argue “the cart before the horse” or even “the weakest link” analogies when embracing a soundstage, and rightfully so: you must have good gear to get a good sound stage. But conversely, bad speaker positioning will make even the best gear sound mediocre or even worse. The point is that tweaking your system involves more than swapping equipment or software. Getting everything in your audiophile repertoire to synergistically work together takes wisdom, planning, and patience.

If you have been following this series, in Part 1 you saw how monophonic sound progressed into stereophonic sound and from there into what is presently called the high-end. From Part 2, you know what happened in the audio industry as the 3-dimensional soundstage developed favor and why rectangular listening rooms are preferred. You also learned how moving speakers influences bass prominence and how the listening room itself influenced the overall sound. From Part 3 you learned how to minimize room bass resonances by mathematically positioning your speakers based on your room dimensions and roughly how high off the floor they should be. You also know that floor rugs are good and that your listening chair (a.k.a. the "sweet spot") are about the same distance from the rear wall as the speakers are from the front wall. In Part 4 you identified the locations of first reflections in your room and hung sound absorbers and diffusers in the appropriate places. In Part 5 you assured yourself that your speaker wires had proper electrical and absolute phasing. And you used an RTA app on your smart phone or tablet to take a snapshot of your system’s smoothness.

In this part, we will explore how to tweak your speaker positions so you can achieve the biggest soundstage possible in your listening room regardless of its size or shape. I presume that you have done all of your homework assigned in Part 4 and purchased the two versions of source material you will need to follow these tuning instructions. Remember to put masking tape securely on the floor to mark the current location of your speakers. So with this introduction, make sure your ears are REALLY clean (I am serious about this) and let’s get on with it.

SOUNDSTAGE WIDTH-AND-HEIGHT: It is when your speakers are properly positioned that the sound will appear to come from other locations than the speaker centerlines and places in between. Ignoring for the moment the depth of a soundstage, the first soundstage property you want to optimize is its width and height.

You may already notice that the size of the soundstage became altered and the sound may even appear to originate from locations beyond the outside of the speaker centerlines. As you move the positions of your speakers from these points of origination, the size and shape of the soundstage – either good or bad – will follow. To help you remember how it changed, you must create a grid on the front wall so you can see exactly how things changed. Hang colored yarn (use a high contrast color to that of the front wall) and thumb tacks every 12 inches from floor-to-ceiling and from the side walls toward the center making an easily-seen grid. Draw a sketch of your room including the yarn grid and record the distances from the side wall (Ds) and the front wall (Df) of your speakers. This will help you remember where the speakers were when you observed this particular-sized soundstage.

Grid Lines on the Front Wall Made from Colored Yarn and Thumb Tacks

The procedure you will use to note the height and width of your soundstage is simple:
  1. Sit in the sweet spot
  2. Play the track
  3. Close your eyes while listening to the track
  4. Listen to the ambience of the recording rather than the fundamental notes of the sounds themselves. Listen deep into the noise floor for those subtle ambience clues.
  5. With your eyes still closed, point to where you perceive the edges of the soundstage to disappear (no echoes or instruments emanate from beyond this point)
  6. Open your eyes and record the position your finger is pointing to on the grid of the front wall by making a small X at their perceived point on your paper.
  7. Add about a dozen or so points to this 2-dimensional paper chart at regular intervals, enough to tell you where at any point on the grid the limit of the soundstage is. Like connecting the dots on a child’s drawing, you will eventually transform onto the paper the psychoacoustic illusion your system creates.
  8. Repeat steps 1-6 on different sheets to account for minor head movements and different seating positions before changing a speaker’s position (use same Df and Ds distances and make more than one sketch)
  9. Create a “master” sheet for that Df and Ds position by averaging together these multiple subjective measurements

For example, put on track 12 of the Red Book version of the Norah Jones album. Listen to the guitar in the first 10 seconds of this track but instead of listening to the guitar, listen for the echoes in the room in which the recording was made (the echoes in the studio and not the artificial echoes created by your listening room). You may have to turn up your system pretty loud to hear these subtleties but play this piece at a level where you not only hear the nuances in the strings but also the slight reverberations in the studio. Stop the playback before Norah’s voice chimes in and replay this track’s first 10 seconds until the sound level is adequate for you to hear these subtle details. Below is a sample of what your first marked-up sheet may look like when focusing on the echoes in the first 10 seconds of track 12.

Sweet-Spot Sketch of a Soundstage

The challenge here is to subjectively determine where in 2-D space the echoes (and possibly the instruments) appear to be. As you reposition your speakers, you will notice slight shifts in these positions and your sketches will help you remember which location expanded or better defined the size and shape of the resulting height and width of the soundstage. Using the same signal source allows you to repeatedly test for improvements or degradations. Before moving things around, let’s take a crash course on how to listen.

LISTENING TECHNIQUES: As mentioned, listening deep into the noise floor for ambiance clues helps you understand the current size and shape of your soundstage. Take your time and learn how to listen for these clues on as many different types of music as you have available, especially your personal favorites. After you understand where these ambiance echoes exist, move your attention to the details of the instruments themselves. Listen for the sonic information just before and just after a single note is played. The “attack” and “decay” of these notes determines the quality of your system, or rather the accuracy of its reproduction but has little to do with the creation of the soundstage. However, as your speakers are moved around and the soundstage size improves, you will be able to notice other such details that were constraining your system’. Let’s take an in-depth look at the Red Book version of track 1 "Don’t Know Why” for these types of clues.

This song begins with a simple trio of acoustic guitar, drums, and bass. The guitar starts playing on its solid-wire strings and is hand-strummed with fingers and thumb. This sound is very different – softer – from that played with a stiff guitar pick, and reveals the lower midrange nuances of the guitar and its body resonances as opposed to the harmonic content of the string. The drummer swishes wire brushes on the snare drum to blend this softer sound with the soft guitar not only setting the tempo but also re-emphasizing the mood of the track. A double-bass is also hand plucked similarly revealing its character announcing the marked differences between this instrument and its fretless electric bass guitar rival. Full-body resonances of the double-bass dominate the lower scales and just as you settle into enjoying the relaxed atmosphere created by these masterfully-wielded instruments, Norah’s silky voice chimes in at a similarly low level almost as if the guitar gave it birth. But with the next word falling from Norah’s lips, she quickly takes command of the performance by raising the volume of her voice to just the right level where it draws your attention to it without becoming overbearing. Your ear is masterfully redirected from the accompaniment to the vocals without disturbing the enjoyment of the entire performance – in other words, a synergy between musicians occurs and this is what sets true artists apart from others. At that moment, all of the nuances created by the vocals and instruments – their echoes and reverberations – define the shape of the soundstage. You can literally point to where the snare drum is with respect to the double-bass and the piano. You can tell where Norah’s voice is with respect to the double-bass. The positions of the instruments you should hear (as laid down by the recording engineer and revealed in the Red Book version) are this:

Track 1 General Instrument Positions

Everyone automatically does this step without observing the cooperative process your brain/ear takes in making these positioning assessments. Directional hearing is as natural as breathing and from it we understand where a sound originates. However, training your ear to hear more than these fundamental positioning clues will make the difference in creating a larger soundstage. The detail of the instruments is where you should now focus, that is, how much distance between each of them can you subjectively assign? Do they sound like they are all coming from dead center or is there “air” between each one? Does the high-hat appear in the same position as the snare drum or is it too in a slightly different location? How far to the right of the bass player is the drummer’s cymbal positioned? Is the piano always dead center or do the high notes appear a little to the right and the low notes to the left? At 1:10 into this track, can you hear the low-level background singers (actually Norah again in an overdub) and where are they positioned with respect to Norah’s lead voice? Your answers to these subjective questions will help you fine tune your speaker positions.

Take good notes about what you hear with your speakers in their current position. Establish a baseline so that you can refer back to your current observations before repositioning your speakers. Use the grid lines on the front wall to help you picture exactly what your system is doing. Create another picture of the soundstage showing the detailed position of instruments after listening to more than their relative locations.

Track 1 Detailed Instrument Positions

After you understand the answers to all of the above questions and have made a detailed picture of instrument positions, now is the time to move your speakers.

POSITIONING THE SPEAKERS: Your goal is to create the tallest and widest soundstage possible. Moving your speakers forward, backward, left, and right will alter the overall size of the soundstage each time you change their positions. Begin by making large moves of about 4-6” in one direction and redraw the shape of the soundstage on one chart and the instrument positions on another. For now, keep the speaker faces parallel to the front wall. Which direction you choose to move your speakers is up to you but in general moving them out from the front and side walls will make the soundstage bigger to a point after which additional movement in this direction begins to shrink its size. Remember that moving your speakers also changes the bass smoothness and a new RTA measurement should be made after you reposition them to see if the perceived improvement in the size of the soundstage has detrimental effects on the smoothness of the bass. The process is simple:

  1. Move your speakers to the new position
  2. If there is an initially observed improvement in the soundstage size, especially in the air between instruments, you have moved them in the correct direction
  3. If the sound stage is somehow compromised (over-emphasis in any individual instrument or shrinkage of the size), move them one inch at a time back towards their original position
  4. Make two diagrams of the changes in instrument positions and in the height and width of the soundstage
  5. Listen to the new position for a prolonged period with your favorite music to see if the improvement impacts the detailed instrument positions in a constructive or destructive way
  6. Make an RTA measurement. If a large swing in bass smoothness is noted, evaluate if this is an acceptable loss compared to the gain in the size of the soundstage.
  7. If you are happy with their new location, move the masking tape on the floor to mark this new position
  8. Repeat steps 1-7 in smaller increments than before.

Remember that speaker positioning is an iterative process where one location will definitely fail and others will succeed. Some positions you find will have a great sized soundstage that will compromise bass smoothness and others will have really smooth bass but fall short in the soundstage size. The way you select your final position becomes a compromise of these two parameters. I prefer to listen to a large, detailed soundstage with a lot of air between instruments and use other methods to help correct bass smoothness if possible.

While symmetrical placement is a rational assumption, you may find that asymmetry is preferable especially in non-symmetrical rooms. However, start by moving both speakers the same amount and in Part 7 we will use another round of tweaks for fine tuning. Remember, proper speaker placement is an iterative process of which this is the first round of many. Do not be too hasty in judging a change. Allow yourself time to understand what did and did not happen as a result of the move.

Always adjust your speakers for an optimal soundstage size as observed from the sweet spot. However, minor changes in position can expand the appreciation of the soundstage from other than this ideal location and additional experimentation can only tell you if it is or is not possible to do so.

SUMMARY: From your drawings and extended listening, you should now begin to see the effects of speaker position, bass smoothness, and soundstage size. You may have found that asymmetrical positions create a better soundstage than symmetrical ones and you may have to compromise on bass smoothness to get a larger soundstage. You may be fatigued by moving your speakers and need a break, especially if you have large speakers and it takes two people to move them.

Coarse positioning (movements of several inches in one direction) will quickly get you near the preferred location; smaller movements from this coarse location (those less than one inch) will eventually find that ideal position. RTA measurements will tell you what compromises you made by moving your speakers.

In Part 7, we will see the last adjustments you can make to improve the air between instruments at the current speaker positions. Until next time…

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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