Don's View

June 2008 Depth and Image

The terms depth, image, soundstage etc. are bandied about in describing a systems ability (or inability) to recreate a reasonable facsimile of musicians playing their instruments in your listening room. Another way of describing this illusion is to say that the speakers "disappear" sonically. In order to recreate this illusion there are a few simple rules.

Rule # 1 The recording must be made correctly. When more than 2 microphones are used in a stereo recording, you're snookered. All the King's horses and all the King's men cannot unravel a mix. Another term often used in audio is coherent. It becomes a physical impossibility to create a coherent stereo illusion when more than one mic is used for each channel.

Rule # 2 The electronics in the system play a surprisingly small part in creating the illusion. It takes a wretched power amp to totally screw things up. It is not necessary to spend vast sums of money on exotic thermionic based units. Also, the crossover, assuming it's not a total dog's breakfast, has little to do with recreating the illusion of an image. (see Rule #4).

Rule # 3 A conventional pair of front firing loudspeakers cannot recreate a natural stereo illusion. It always sounds like a sophisticated public address system. I suppose the continued success of front firing units is due to the proliferation of PA systems wherever you go. A "live" jazz event isn't really live when everything is squeezed through a PA system. Hell, even the opera is now mic'd since most of the citizens expect things to be "loud".

Rule # 4 The dirty little secret of the recreating stereo illusion with a loudspeaker is: 360 degree dispersion at all frequencies into a solid angle. When a two way sytem is used the woofer and the tweeter must be snuggled as close together as possible. Both units must exhibit 360 degree disperion at all frequencies into a solid angle. To achieve this task the drive units are forced to behave in this fashion. One need only look at the detail of an omnidirectional microphone to see how it "receives" it's signal. A grid is fixed over the capsule forcing it to receive from all directions. At the other end of the chain we simply turn the thinking inside out and "broadcast" the signal by forcing it to disperse into a solid angle. Many speakers will have drive units on different faces of the box firing six ways to sunday. This won't work. It may sound a bit more "spacious" but since the drive units are too far apart and there is not a solid dispersion pattern at all frequencies due to lobe effects, we end up with yet another PA system. A full range single drive unit suffers the same problem. When mounted in a conventional front firing fashion the effects of a discontinuous signal launch of all frequencies will get us back to PA land. A single drive unit firing upwards and then forced to launch its signal into a 360 degree angle at all frequencies will work. The bad news of course, is that a single driver will always trade off frequency extremes - this is true no matter how it's mounted. Any talk of the basic "monkey coffin" type of loudspeaker having great imaging is nonsense on stilts.

2007 January - Musicality

Canadian music lovers fondly remember Bob Kerr's afternoon radio show Off The Record on CBC. He provided us with a vast array of titles and running commentary including an almost weekly tirade on the liner notes of CD's. "How the hell can anyone possibly read such tiny print with blue type on a black background!"

Nothing much has changed in that department. Bob Kerr also commented on the recordings. The better ones he would describe as "the sound of real musicians playing great music and sweating while sitting on squeeky chairs". These great recordings remain a rarity.

The illusion of real musicians making real music in your living room is a worthy and satisfying goal.

Modern recordings however, have been stripped of their "life" and texture. This has nothing to do with the LP/CD argument. The problem starts with the number of microphones. Assuming 2 channel stereo, there can only be 2 microphones. Period.

There are no exceptions to this inexorable law of acoustics.

Secondly, there can be no compression of the signal ie: the louder bits squished down in amplitude to achieve a more or less uniform level of sound. This destroys any dynamic contrasts which allow the music to come alive.

Finally we have what I like to call the processed cheese syndrome. Those cute and tidy perfect little slices each in its plastic wrap are perfect. Each slice like the next. None of them has anything to do with a great nippy old cheddar. Likewise the "studio multi mic mix" recordings. Tunes are recorded, mixed, processed and then if there are any tiny flaws they are edited and scrubbed clean with a patch taken from another take. All in the name of perfection. The result? Perfect elevator music. Nothing remotely resembling a live event. If the event is not correctly captured at this point, it can never be rescued by all the associated equipment nor can it be saved by throwing money at it.

2006 April - Double blind testing

How to conduct a double blind test (or how to make an enemy and a few bucks)

Buddy has just spent the equivalent of a trip to the Bahamas on a pair of interconnect wires. You challenge him to a duel (figuratively speaking). You tell him that your $10 cables sound the same as his "Bahama" wonders. Not wanting to look like an idiot he goes for the bait. Offer him $100 if he can identify which cable is which. If he can't he pays you $100. All you need is to have is a correctly designed preamp with an output impedance of say 200 ohms or less. The test is 20 trials of either cable "A" or cable "B". Instead of tossing a coin you can go a bit high tech. With your $7 pocket calculator you can use the random number generator. Any number from 001 to 499 can be cable "A" and 501 to 999 is cable "B". Should the number 500 appear you can toss it out. Have a third party poke the calculator and jot down the sequence 1 to 20.

Caution! Before undergoing the test you must do a sighted trial!

Hook up Buddy's cables and let him see them attached. When
the music starts he will immediately swoon and go into an audiophile trance. The depth! The image! The shimmering highs!...well, you know the routine.

Now swap the cables and let Buddy see the connection. Now see the frown. The sneer. Gawd what an awful cable! Now the test begins. Both you and Buddy leave the room. The 3rd party connects according to the chart A or B. 3rd party now leaves the room. From this point on no one knows which cable is in the circuit. Do this 20 times. There can be no communication whatsoever with the 3rd party! No one has ever been able to determine which is which. By sheer guess you'll get 10 out of 20. Statistically you must score 17 or so. After all, if the expensive cable was so much better when sighted surely you should be able to pick it out by just listening... Buddy will come up with every excuse you can think of. You can remind him that he heard the difference when the test was sighted. Now take his $100 and split it with the 3rd party. Order pizza.

2006 February - On Coherence

I get a chuckle out of audiophiles. They pick up all the buzz words from each other and those words and phrases get etched in the audiophile jargon. Pace, rhythm and timing (I'm not making this up) is a biggie. It is proported that a particular piece of equipment posseses an ability to: "have good P.R.A.T."

Simply amazing.

It beggers the imagination. I have a CD from the shelf of Beethovan symphonies. The first movement of the 1st symphony is marked as 8 min. 20 sec. Does this mean that a good amplifier will adhere to the elapsed time and a bad one will straggle in at 8 min. 33 sec.? Just wondering.

Anyway, one of the favourite hand- wringing phrases of the audio junkie is "coherent." The term can be translated roughly as "reproducing the entire waveform of the signal as regards to its frequency and phase from microphone capsule to speakers" A noble goal to be sure. Here's the rub. Assuming a stereo (as in 2 channel) system. 2 and only 2 microphones can be used. Period. Any additional mic's render the entire chain INCOHERENT. Just like poor old Humpty Dumpty, all the king's horses and all the king's men cannot put it back together again. Any stereo recording using more than 2 microphones is no longer stereo. It is now multiple monaural. A forest of microphones will not save the situation. Only by using 2 will it remain coherent. Now ask yourself "how many true stereo recordings do I have?" The answer maybe 1 or 2. The other 1573 are not.

Vast sums of money are spent on equipment and yet, the sound doesn't really improve until we use a correct recording. With the usual multi mic mixdown of current recordings the net result is just a very exotic P.A. system. An expensive system plays very loud and has the typical "in yer face" sort of reproduction. It still sounds like a P.A. system. I suppose that 99% of the problem lies in the musical taste of the listener. The sight of a middle aged audiophile parked in front of his $80,000 system while listening to some over produced rock album is pathetic. With twanging electric guitars and screaming vocals squeezed through miles of microphone cables and hundreds of circuit boards the result is a totally incoherent soup. Playing back this mess at levels that Helen Keller can hear is not the answer. Perhaps an improvement in musical taste might be a good start.

Morrison Audio