Wednesday, January 15, 2014

High-end Soundstages - Part 7

Speaker position influences the size and shape of your soundstage along with the bass smoothness of your system. Unfortunately, optimizing one usually means compromising the other. Can you have the best of both worlds? Read on and let’s see.

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. Part 6 explained how to create a map of your soundstage and use RTA measurements to show you the compromises encountered when moving your speakers. Part 6 also explained how to keenly listen to music so you can know when moving your speakers made a constructive or destructive change in the soundstage beyond mere positioning clues.

As you moved your speakers about your starting point in Part 6, you eventually found a location that just starts to make the sound fuller where the psychoacoustic image perceived while listening to a recording got dramatically wider and higher. You thumb-tacked colored string onto the front wall and pointed your finger to an instrument’s perceived location on that grid to keep track of where the image moved as you moved your speakers. At some point during this moving process, the psychoacoustic image locations appeared to be well beyond left side of your left speaker, beyond the right side of your right speaker, and high above them both giving you the largest soundstage possible.

Along with an increase in the height and width of your soundstage, you may have begun to notice some unexpected magic also occurring at this position. Typically you will begin to hear an increase in the front-to-back depth, that is, the relative position of vocalists and instruments layered between you and the front wall. Your music begins to take on a realism that up until that point was overlooked and the closer you get to that magic location, the more this 3-D effect is enhanced. Here in Part 7, we will switch to a higher-quality signal source than the Red Book version and make final tweaks that may surprise you.

ASYMMETRY: While uniformity conjures up the highest, widest, and deepest soundstage it may also create the most unpleasant bass resonances. That is, with speakers positioned exactly the same distances from the front and side walls, bass smoothness will suffer the most. There is a really simple trick to prevent this from happening: move one of the speakers away from the wall(s) while keeping the face of the speaker parallel to the front wall. Moving one of the speakers compromises the size of the soundstage but can also eliminate one or more nasty room resonances. So how do you know if the bass has suffered?

As you listened before to the size of your soundstage from your sweet spot, listen now more critically to the smoothness of the bass. If there is a sharp rise at some note or group of bass notes, your speakers are most likely exciting inherent room resonances. For example, as the notes on a bass guitar or double bass go down the scale, some notes will sound much louder than others. It is these louder notes that tell you your speakers may not be in the optimum position for this room. You may be able to measure the low frequency behavior with a pink noise source and your cell phone’s RTA app although some cell phones have built-in low-frequency limitations to make your voice more easily understood. For example, I own a Samsung Galaxy S3 and my carrier is AT&T. This phone has this built-in limitation so frequencies below 200Hz are predictably attenuated. Nevertheless, room resonances can be observed as irregular rises in this reasonably smooth attenuation curve.

Picking Out Room Resonances

To observe room resonances, point your cell phone’s microphone at the midpoint between the speakers at your ear height from your listening position. It is best to place the cell phone on a tripod (or similar small, high table). Play pink noise (inter-station FM noise is good in a pinch) and look for peaks especially below 100Hz. Most likely, there will be some small peaks and possibly one or two larger ones. On the side of the room that is most uniform (no windows or doors nearby), move that speaker toward the other speaker (about two inches should do nicely) while keeping the face of the speakers parallel to the front wall. Recheck the effect on the size of the soundstage by pointing toward the grid as you did before and note the effect on its change in size. Then measure the room resonances again with the RTA app and pink noise from exactly the same position and see if the resonant peaks disappear or at least improve. Confirm your measurements with your ears to assure that other subtle changes in inner detailing are not adversely affected.

Move One Speaker 2” Toward the Other

Next, move this same speaker forward (toward the sweet spot) keeping it parallel to the front wall and repeat the RTA measurement and listening evaluation.

Move This Same Speaker Forward 2”

This new position (Ds+2” and Df+2”) is your asymmetrical starting point. As you did in moving your speakers around the Ds/Df starting point, do so in small increments around the asymmetrical starting point until there is a suitable position where room resonances are minimized. Again, use the grid lines and the RTA measurements to understand how moving a speaker impacts these resonances. For now, find a position that has better uniform bass smoothness (makes minor compromises on the sound stage size). There are more adjustments that will help return the size of the soundstage next.

TILT AND TOE-IN: Changing the orientation of a speaker (no longer parallel to the front wall or the floor) can achieve additional benefits to the size and shape of the soundstage, especially its depth. By tipping and twisting each speaker, minor adjustments in the soundstage are possible. Compared to just setting your speakers at any convenient position in your listening room, what you should gain as a result of optimal speaker tilt and toe-in is extended frequency range, wider dynamics, better transient response, and less distortion. Optimal tilt and toe-in allows you to hear in the newly-created soundstage additional details about a performance (either live or studio versions) like:

·         The acoustics of the hall or studio were the recording was made (far corner ambience)
·         Subtle noises of instruments (inner detailing of finger movements on strings, breathing just before reed instruments are played, or drumsticks striking the skin just before making a bass note)
·         Very low-level sounds (tapping feet of musicians or sheet music turning)

You will find yourself listening to a familiar performance – on of your favorite pieces – in a whole new light listening for these subtle clues deep into the silence of the recording. You will find more information in these quiet passages than you ever thought possible and within these more-silent moments are where these subtleties hide. They were always there but the interaction between the room and your system prevented you from fully appreciating them. From this magic position you may also more easily hear subtle effects when swapping interconnect cables, speaker wires, and power conditioning. Part of this ability to detect such minor changes synergistically occurs as you train your ear to hear these effects since with proper positioning such effects become more audible.

Once you find this magic position, now is the time to change your source material to the higher-resolution version since these last subtle tweaks will reveal even more nuances and bring them into the foreground.

TOE-IN: You should now be hearing things that you never realized were there from all of the music in your collection. From that magic speaker location, background details, whisper-level nuances, and instrument inner detailing all are more easily observed and seem to change their intensity. Echoes and reverberations reveal a dramatic sound space and your playback system is definitely not the same as it was before. Nothing has changed in your equipment, but the sound is radically different and far more captivating. Swapping to a high-resolution source will now reveal even more things about your system’s ability to pull out those nuances and permit your final tweaking. Here, focus on the far corners of the soundstage and listen to the amount of front-to-back depth.

Start by aiming your speakers toward the sweet spot so that the face of the speaker directly faces you. Rotate the speakers at the center of this position and twist them inwards about 2-3 degrees. See how this small change impacts the depth of your soundstage. There will be a point that the depth will increase and then decrease. Back off just a small amount from that angle and continue to listen.

Twist (Toe-In) Both Speakers Toward the Sweet Spot

For example, in the first three seconds of Track 3, “Cold, Cold Heart,” Lee Alexander introduces the song by artistically taping his finger on the vibrating double-bass string making it momentarily buzz as it quickly comes to rest. The double-bass is positioned by the recording engineer in the center channel relatively forward in the soundstage. After one second, Adam Levy joins in by plucking a muted a chord on his guitar. Adam is positioned to the left of Lee at a similar front-to-back location (as if standing next to each other on stage). Four seconds into this duet Norah’s piano joins in again in the center channel but its position is behind the double-bass (recorded at a lower volume so as to not overwhelm her melodic vocals).

Her piano resonances reveal information about the size of the studio in which it was recorded (this is a different studio from where the guitar and the double-bass are recorded). You should be able to hear low-level echoes in the far right and far left corners of the soundstage, especially at the ceiling level. Norah’s voice joins in at about 12 seconds, her center-channel voice is positioned forward of the double-bass. Notice that the artificial reverberation in her voice adds no hint to the size of the room in which her voice was recorded but makes it far more appealing than a flat, non-reverberant vocal. Although her voice echoes, it has no depth as does the piano and consequently as her voice fades, the reverberations remain forward of the double-bass even though the left and right sides of the soundstage indicate their borders.

It is difficult to graph what is happening to the psychoacoustic illusion of three-dimensional space from these movements since everything is purely subjective. But you can point to where you perceive the most distant corners of the soundstage and try to map that on your paper. At some point the sound from this performance appears full without emphasizing either the left or right sides of the sound stage. Once a twist-angle position is optimized, the next step is to tilt your speakers.

TILT: If you have not already done so, now is the time to clearly tape the floor marking the present position of the speakers including toe-in. Now is also the time to make sure that your speakers are on quality adjustable spikes (like the high-quality Track Audio models or the economical Dayton Audio versions). What is important about the spikes you use are that they remain sharp and they lock securely into place. And since room floors are not themselves completely level, leveling and tilting your speakers with adjustable spikes becomes an easy task. If your speakers do not have provisions for spikes, I highly recommend adding them now. I prefer using 3 spikes – 2 in front and 1 in back – as opposed to 4 spikes since 3 spikes are easier to tilt in any direction than 4.

With the speaker spikes in place, the speakers properly positioned from the side walls and the front wall, and the speakers properly toed in, now is the time to start tilting them. But first, you must make sure that both are currently tilted back in equal amounts. Hopefully, there is one flat surface on your speakers to which you can place a digital level. Matching the tilt angle with such a level assures that both speakers are tilted exactly the same amount.

Tilting the speaker aligns the time sound arrives at your ears from the individual drivers of your speakers. Once properly tilted, transparency, focus, and presence are optimized. With the bottom of the speaker parallel to the floor, start by listening to the current size and shape of the soundstage paying attention to focus – the ability to distinguish one instrument in free space from another. Tilt both speaker backwards about 1/8” (a half-turn at a time) by raising the front spikes. As before, make small adjustments and adjust both speakers by the same amount of tilt. You will eventually find a reasonable tilt position where instruments are rock solid within a performance (very little drift left/right, up/down, or front/back).

From any familiar high-quality favorite recording of yours, you should be able to observe this improved focus effect. A good source for this is Track 14, The Nearness of You, observe the studio ambience revealed by the piano. If your speakers do not reveal the furthest corners of this room, sit up really straight to raise or slouch down a little to lower your head at the sweet spot. If the room ambience improves with your head slightly higher, the speakers are tilted back too much. If the ambience improves with your head slightly lower, they are not tilted back far enough. You should find a tilt angle where the sound just clicks where the music really locks into both time and space. Just like pressing down on the gas pedal to achieve a certain cruising speed in your car (pressing down too much on the pedal makes you go too fast and not enough makes you go too slow), so does the optimum tilt angle allow you to enjoy a more clearly defined soundstage and a more purposeful sense of pace and rhythm.

Usually, the midrange driver in your speakers will be pretty much in a direct line to your ears at this optimum toe-in and tilt angle are achieved. Minor variations to this line achieve optimum clarity, focus, and imaging. Once you have fine-tuned that angle, lock the feet in place and you are all done.

Your soundstage should now be full and highly emotional charged with life and energy. Reverberations should begin to take on a fading effect that degrades into the distance beyond what you can see of the front wall. If your arms were long enough, it’s as if you could reach through the front wall and touch the distant corners. Typically, echoes in the upper right and upper left extreme edges are impacted by these last few tweaks and those changes can be again plotted on your paper. If you have a difficult time in correlating echoes to depth, focus on these same extreme corner positions to make these final adjustments.

Remember, you must decide the best speaker position for your own musical preferences. There will always be a tradeoff between smooth bass response and optimal soundstage size. My ears are more tolerant of bass bumps and dips and more critical of soundstage sizing and inner detailing. You must decide what you can tolerate and what you cannot and adjust your speaker positions accordingly.

I hope that this seven-part series helped you to enjoy your system even more than before and at the same time taught you a little about how to listen to music. It amazes me when asking an audiophile, “So what differences did you hear?” a long delay of utter silence results in the inability to describe clearly what one’s emotions feel. Most people know what they like when they hear it but have a difficult time putting that into words. With patience and time you will be able to clearly enunciate and accurately convey exactly what you hear and what you do not in any system. Once your speaker positions are properly “dialed in,” a whole new world of enjoyment and listening pleasure awaits. You may find yourself saying things like, “I never heard that before…” or “Did you hear that?” or “Wow! That was amazing!” Keep making small changes in all ways to complete your fine-tuning process. Oh yes, lastly, remove the tape from your floor and the strings from your walls, turn off the lights, and listen to what you’ve been missing!

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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