Thursday, May 30, 2013

Bozak Rebuild Project - Part 8

Sometimes, you just have to have faith.  I did believing that one day I would discover a high sensitivity leaf or ribbon tweeter that would match the acoustic efficiency of the Bozak drivers. This is a tall order but as Tony Robbins says, "You are what you believe." So I again put his legendary ideas together with my pursuit of the high end and viola - a 97dB/W/m ribbon tweeter enters my life.

I searched long and hard trying to find a dynamic driver that could keep pace with the Bozaks and found something sort of close - but not really. The Audax gold dome (TW025A28) came close measuring 94dB/W/m (not at the 1/2 meter point Audax publishes their data) and I was pacified with filling in the top octave where the Bozak B-200Y tweeters fell short. Below is an RTA measurement of the way this super tweeter in the system performed.

Audax TW025A28 Dome Super Tweeter

With persistence and perseverance, I changed my search focus from dynamic home audio drivers to professional compression drivers and found a few that were tempting. JBL, Fostex, and Fountek all had bullet-styled tweeters popular in car audio systems but my ears are more sensitive to the ringing and other inherent compromises in such driver designs and although VERY tempting, I decided to "keep the faith."

One day, I ran across what was called the Versarray made by the well established professional sound reinforcement company, Peavey. With its touted 97dB/W/m sensitivity, this seemed to be a perfect match for my dreams. Now, to find some.

Searching eBay, there were some Versarray  systems still sold despite the model now being discontinued. Apparently professionals either love them or hate them, mainly because of their limitations in stacking and angling vertical arrays, but those who played small club venues seemed to boast about them. With this in mind, I found one and gave eBay a bid that couldn't be refused. One Peavey RD 1.6 came to my door a few weeks ago and I was thrilled. It looked like it was going to work and with a quick attachment to the system (disconnecting the Audax and temporarily connecting the Peavey), I was not disappointed. But wait, I only have one! As Tony says, "keep your eyes on the prize."

So undeterred, I settled into that personal conviction where I just knew another driver would soon appear, and with the very next emailing of the Parts Express clearance catalog, my dreams and blind faith paid off.  Somehow, Parts Express bought Peavey's old stock and were now selling them for a pittance. If they still have them, here is the link.

Within a week, another of these little beauties arrived at my doorstep and I hurriedly unwrapped it and attached it temporarily to the system as the other.  Now with a pair of these drivers sitting on the tops of the woofer cabinets, I was able to judge the potential of their sound and it proved better than I could have anticipated. The sound stage opened up literally as if a doctor had removed ear wax from my ears and instrument inner detailing was remarkable. That was enough to convince me I needed to stuff them into the existing box - somehow.

Coincidentally (if you believe that there are such things as coincidences), this driver is exactly the same size as two Bozak B-200y drivers. So I pulled out the center two drivers from my satellite, stuffed in the RD 1.6, and flipped on the switch. I was shocked. After changing my underwear, I settled down and started to make some measurements trying to see if what my ears heard my RTA measurements could confirm  - and they did.

Peavey RD 1.6 Ribbon Super Tweeter

Now understand that there is a small error in the crossover network for the Peavey that I have yet to correct, but have already designed. Adding a few turns to the second-order Bessel inductor will bring things back into alignment and I will do this some time next week. But for now, I am thrilled with their performance and I cannot find the proper expletive to give this driver and this system.

Like any good leaf or ribbon driver, this one is no exception. Its massive magnet structure and low mass diaphragm sound so crisp and clean compared to the slower dynamic driver I had been listening to.  The Audax, while a very good dome tweeter, just does not have the transient abilities that a low-mass tweeter does. Now I can hear the taps of cymbals and tamps of tambourines clearly rather than in the distant background as before. Now I can hear sheet music turning in quiet classical passages and all of those other sparkling top-octave characteristics well-designed high-end speakers posses.

These speakers have come a long way from the first time I built the satellite and now can hold their ground with some of the best I have ever heard. Here is a picture of the system now to show you what the new satellites look like.

Satellites with RD 1.6 Drivers

I am shaking at the time of this writing since adrenaline is still coursing through my veins from the excitement. What I can say without reservation is that if you are considering performing any of the modifications to your Bozaks or adding a super tweeter to your system, you have to give this driver a chance. Parts Express has a really nice no questions asked return policy IF you do not solder the driver terminals (I used test leads with alligator clips for my initial evaluation) or blow out the driver (duh!). The price at $100 each is very fair and shipping for the pair is free.

So my friends, stay tuned for what appears to be the final round of tweaks to this amazing speaker system, the one where I finalize the crossover network design. Hopefully, the math and the reality match up and yes, I have faith that it will. See what happened next in Part 9.

See also Part 1Part 2, Part 3, Part 4, Part 5, Part 6, and 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.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.

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.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.

Wednesday, May 15, 2013

Room Tuning - Part 1

Pretty much everyone knows that rooms affect the way a speaker or system sounds.  This means that if you were to put your system into a friend's home and listen to a familiar song, it will sound very different from that in your listening room.  This is because of the way a room interacts with primarily your speakers and this is what I starred fussing with in my listening room.

Several really good books have been written on the subject or room tuning, the most popular being Get Better Sound by Jim Smith.  In his wonderful book, Jim discusses many real-life issues and uses many precise measurement techniques that combined with his decades of experience will move any listening experience closer to its full potential.  But for those of us who want to play with your room much like you do by swapping interconnect cables on your gear, there is another way to do this and achieve some very interesting and rewarding results.  All you have to do is understand a few important issues about the behavior of sound.

Before I begin, here are my basic assumptions:
  1. Your speakers are in the position you know them to perform their best (you have moved them left/right, up/down, forward/backward to find their best physical location)
  2. Your listening position (sweet spot) is at its stable location (you do not plan to change where you listen to your system)
  3. You are not planning to change your speakers
  4. You are not planning to alter the content or shape of your listening room (most importantly you do not plan to move or change walls as in a major construction project)
In other words, your listening room is pretty stable and you are happy with your speakers.  If you have a subwoofer and surround sound system, we'll get to these later but for now we'll just look at the primary front two speakers (front left and front right) and address the other channels later (their treatment needs are a bit different).

First of all, echoes are great in places like churches and canyons where sound can bounce all over the place creating a mesmerizing experience of reverberation and time delay.  Echoes are possible because of the speed that sound travels through the air, rather slow compared to something like the speed of light.  So when a reflecting surface is a long way off from where you are standing (like the wall of a canyon or wall in a very large room), exactly the same sound bounces back to your ears but at a differently-perceived time and at a reduced level (i.e., it is delayed and less loud than before).

When sound bounces off of a surface, some of its energy is absorbed by that surface and the echo is less loud than the sound that originally struck that surface.  When a surface is very flat, the reflected sound is louder than say if it were to bounce off a curved or irregularly shaped surface.  And when the surface is softer (like a blanket or down comforter), a lot of the sound is absorbed and very little is reflected as opposed to a hard surface.  Within these three statements hide the keys to how you can control echoes (reflections) in your listening room.

So the trick in your listening room is to control these reflections and to do so you can either change the shape of the reflecting surface (flat to irregular), change the composition of the reflecting surface (hard to soft), or remove the reflecting surface (something that is a little harder to do).  But the big question is WHERE to do this in your listening room to get the results you desire?  Enter a simple everyday state-of-the-art ultra-high-technology device called a MIRROR.

Mirrors do for light what walls do for sound, that is, they are both flat and hard and they both absorb little of the energy that strikes its surface.  So the first tool you need to get is a mirror, about a 12" x 12" will do nicely.  The next tool you need is a friend to hold that mirror against the surfaces in your listening room.  The last tool you will need is some blue or green painter's tape to put on the surfaces without harming them.

What you want to do is to locate where in the room you can see the fronts and backs of your speakers from your sweet spot.  Your friend will slide the mirror along the walls, floor, windows, and ceiling to where you see one speaker and then the other from your sweet spot and then use the painter's tape to mark those areas.  Now do not forget to mark the areas along the wall behind the speakers where you see the backs of the speakers in the mirror AND the walls behind the sweet spot.  What you have done in this simple exercise is to identify what is called the FIRST REFLECTION surfaces in your listening room.  These are the surfaces that reflect the MOST high-energy echoes to your ears and what we now want to do is to somehow change them so less energy is reflected.

Blue Areas are First Reflection Locations

Pretty neat trick, right?  So what you should have is a couple of rectangular areas taped on each of these surfaces that mark where you can see your speakers in the mirror (one taped rectangular area for the left speaker and one for the right).

The next question is this: NOW WHAT DO I DO?  For the answer to that, you'll have to tune in next time.

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.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.

Monday, May 13, 2013

More on Line Conditioning and Power Demands

I have owned an OPPO BDP-105 for several months now and I am continually impressed by its visual and sonic images (yes, I mean sonic images). Although my OPPO had a nasty firmware glitch, one that had to be corrected by returning the unit to the factory (argh!), all is well new in my home entertainment system.  I am pleased to report that a few minor additional changes to my rig has resolved some other annoying issues.

To provide some much-needed background, my darling wife is a stickler for parasitic power consumption (hates to leave things on that could otherwise be turned off) and our power conditioner turned out to be the rig's Master Switch.  However, powering down the rig in the correct sequence was a challenge for her to remember so we decided to do away with that and just compromise by leaving the system on continuously in whatever standby modes each piece of gear offered.  Most people understand that leaving your gear on improves thermal stability and this is what we first observed.  Things sound better right away and we do not have to wait the obligatory 30-60 minutes for the rig to warm up.

Another issue was caused by the huge number of power losses normally experienced in central Florida.  The power grid here is running at a capacity that pretty much exceeds its original design and, to compensate for the increased demand, transmission line voltages have been increased to their physical limits.  You can hear the huge ceramic insulators sizzle in high Florida humidity knowing that electricity is now flowing down them and into the ground rather than to its desired destination (apparently an acceptable loss to these infrastructure designers).  Raising the voltage on transformers not originally designed to operate at that level causes them to literally explode once thermal runaway begins (such as on hot days when there are a lot of air conditioners running and the heat-exchange efficiency is reduced on the cooling units for these transformers).  As a result, we lose power here a lot in dramatic fashion.  Without warning, thundering explosions echo through the treetops as substation transformers die in such spectacular fashion that even action moviemakers in Hollywood would envy.

The solution was a small pure sine wave UPS to power those electronics in the video portion of the rig that could withstand power interruptions for about 20 minutes without flattening the standby battery.  Moving the loads of these video components from the line conditioner to the UPS added capacity to the line conditioner for the audio components.  Much like overtaxing the power grid, my rig was taxing my line conditioner and splitting power in this way improved the audio playback quality.

What did I hear?  As you know if you have been reading any of my articles, I have a very dynamic system capable of huge transients and sudden surges of SPL.  What I heard was a distinct improvement in this attack where rim-shots on snare drums, explosions and gunfire, basically all of the starting moments in any instrument or sound effect were all greatly improved.  I attribute this to the additional power flowing through the line conditioner and primarily to the power amp.  Let me explain.

When you ask too much from your line conditioner, voltage levels sag and what was once 110V now becomes 108V or even worse.  Such voltage fluctuations result in non-linear power produced by any piece of gear attached to the line conditioner.  When the voltage drops at the line conditioner, the bias also changes slightly on the output devices and the distortion increases.  So not only do you get a power drop as demand goes up, you also get increased distortion because of these small bias changes.  When power supply exceeds power demand, you do not get this problem.

Think of it this way.  If you have a garden hose and want to fill a bucket, you can do a few things to fill the bucket quicker.  One is to use a larger garden hose and the other is to use a second garden hose.  There is only so much improvement in flow you can achieve by going to a bigger and bigger garden hose but as soon as you add a second hose you immediately reduce the time it takes to fill the bucket.  Adding the UPS to my rig was like adding a second garden hose.

Now there is a gotcha in adding the second power source and one that must be remembered.  You must always run all of the equipment in your rig off of the same electrical phase from your power panel (see my guide Extreme Audio 1: House Wiring for a complete explanation - a steal at 99 cents).  The connection of your "garden hoses" does not start at the wall outlet, it starts at the circuit breaker panel and you must plan to supply enough capacity to your system from there.

So there you have it, a brief walk through how to improve your system by properly designing adequate power capacity to operate your rig.  When playing your rig at loud levels and you notice that the sound deteriorates, I would suspect that the supply voltage at the outlet is dropping and you need to add more electrical capacity by adding a second power source (a second garden hose).

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.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.