Thursday, May 23, 2013

Room Tuning - Part 2

So far, you've identified where in your listening room the first reflections occur. Now comes the time to do something about it. There are a few choices you have depending upon what is presently there in the room and what you want the room's aesthetics to be when you are done.

For some audiophiles, acoustic panels and tube traps are aesthetically pleasing as well as acoustically enhancing.  But to the rest of the world, these things are pretty ugly and have no part in a normal living environment.  I live with a woman who falls into the latter category and I - over time - have agreed with her decorating opinions. What I came up with was an approach that hides the acoustic treatment in plain sight (a win-win scenario).  I used whatever we would normally put into the room and changed its acoustical properties to do what I needed ti to do.

For example, living with an artist you can imagine how much art we have hanging on the wall all of which are not leaving the listening room.  But these items when properly relocated to strategic points and treated can offer some assistance in helping to eliminate first reflections.

So what can you do? The first and easiest thing is to go out and buy at least 10 yards of 10 ounce batting from your local fabric supply store (the kind used in making comforters, quilts, and the like). This material is very easy to cut into shape and when placed behind objects such as pictures, tapestries, and the back of your equipment cabinets, also provides sound absorption (the win-win). 

Cutting the batting a little smaller than the size of the object keeps it out of sight and the thickness of the batting pushes the object away from the wall - just a little.

1. Use the picture as a template

2. Cut the batting a little smaller

 3. Cut out a section to permit hanging

I took down the pictures and cut pieces of batting behind them and using double-sided tape to hold them in place while hanging them securely on V-shaped hooks.  The V-shape holds onto the object better than a straight nail and the hook also stands off from the wall further than a nail would.

10 Oz. Batting Behind a Picture

But there are some locations that just do not lend themselves to pictures and here you must be a little more creative to hide what it is you are doing. Look at the surface requiring treatment as an opportunity rather than an impediment or obstacle (a valuable lesson in life).

For example, I needed to absorb a first reflection near the rear corner on the right wall.  What is located there is a small coat closet that I converted into a turntable room (sandbox and shelving for albums - see my other posting on the turntable closet).  I knew that applying batting to this door would be a great idea but it would also look terrible if not done properly. So my wife went to the fabric store with me and picked out some neutral material that would be acoustically transparent while still maintaining some reasonable aesthetics (it matched the wall color really well and reasonably disappeared into the decor).

I removed the door, hinges, and knob and cut batting to fit.  With the fabric on the floor, I laid the batting on top, and then the door on top of the batting (remembering which side was to be OUT). I stapled the cloth to the inside of the door carefully wrapping the material around the edges of the door. Reconnecting the hinges and handle was not as tough as expected and when it was re-installed into position it resembled a padded bench. Regardless, it looked reasonably well but more importantly it functioned perfectly and we didn't like the looks of the old door anyway so anything was an improvement. Note also in the below image the treatment of the rear of the satellite speakers.

Look at challenges as opportunities

Treating the room then became a game of musical chairs where we tried to fit this picture here and that tapestry there arranging things that at first sounded best and then compromised on what looked better.  What you can do is to treat the rear of your pictures, the inside rear frames or paintings, the undersides of tables, the back sides of your speakers, and whatever rear panels of furniture (those surfaces that are not normally seen).  Moving these treated items as close to the first reflection locations as possible helps to solve your acoustic nightmare and improve your system's otherwise excellent imaging and sound staging abilities.

What I heard prior to treatment was psycho-acoustic images slightly drifting in the sound stage and parts of an instrument appearing from the speaker and not the other parts of the psycho-acoustic image. Happily, I can report that the entire acoustic waveform of all instruments now are embodied by the psycho-acoustic illusion in its position in the sound stage. As a result of treatment, the depth of the sound stage is enhanced as is the ability to resolve faint echoes and nuances in a recording are greatly improved.

With a little trial and error, things began to sound pretty gosh darned good.  Areas of midrange muting were removed as were high-frequency extension.  And the size and shape of the sound stage grew in every dimension imaginable creating a very pleasant listening experience from more than just the sweet spot.  The enhancement to the sweet spot was even better stabilizing instrument positioning and permitting additional clarity to inner detailing. Instruments are rock solid in 3-D physical space and the accuracy of an instrument's characteristics is mind blowing.  To hear an oboe not only solid in 3-D space accompanied by the illusion of the size of the room in which it was recorded is a true treat. And remember, all of these huge improvements came as a result of zero changes in the system's electronics, $50 in batting, and a few hours of our time.

To add to the objective aspect of my room treatment, I made before and after measurements from the sweet spot to see if what I was doing was what I was hoping to do. The graphs below show the before and after RTA measurements but the minor changes in the squiggly lines do not even begin to hint at how much more faithful acoustic reproduction is.  The bump in realism is much like calibrating a fine video system where once the whites are not overdriven and other levels are set appropriately, sheen, luster, succinctness, and resolution are all better resolved.

 Before Room Treatment

Treating First Reflection Locations

Treating the Door and Backsides of Things

As you can see from the above measurements and if you are familiar with the way your system sounds, you should not only be able to hear but also measure differences as a result of treating the first-reflection points in your room. Treating other areas such as the undersides of tables, back panels of your speakers, and behind equipment cabinets, can again alter the sound in a positive way that your system produces. And you can do these changes yourself.

My parting words to you is to experiment with your system. Remember that if you do not like what you hear after toying with things, you can always undo what you did and return things back to normal. If you never try tweaking, you will never know the joy of making your system sound better as a result of efforts from your own hands.

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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