Audio on the web appears to be cluttered with far out opinions and ridiculous claims followed by emotional criticism. The element of humor seems to be forgotten. One of the early publications from the 1950's making fun of audio was Emory Cooks "Audio Bucket". Then there were years and years of priceless cartoons by Charles Rodrigues. They started in High Fidelity magazine and ended in Stereo Review. Swann and Flanders made a record in the 1950's called At the Drop of a Hat that included a song called "Song of Reproduction" which was all about the joys and sorrows of hi-fi. (Angel 65042)

Your critical observations in audio are valuable. Contributions of funny audio one-liners and especially audio limericks are very welcome. This page is close to G rated so they should be geared appropriately. I can't guarantee all of them will be used but credit will be given to those that are used.

Floyd Toole wrote an article in Audio Scene magazine many years ago demonstrating that there is no audible difference between GOOD amplifiers. I have personally completed several blind A-B listening tests over the years between good amplifiers, tube or transistor. Although I thought I could hear a difference each time, my choice was only correct about 50% of the time. I have also conducted blind listening tests for other people. I have learned how important it is to set the amplifier gains to be exactly equal and that the amplifiers should not be seen or identified for the listener. The slightly louder amplifier often is preferred. Comparison must be instantaneous or the listener forgets. If the identity of the amplifiers is known, the listener often gets preoccupied with identifying which amplifier is playing instead of the sound quality. The questions asked of the listener about the sound quality are also very important. I even hide the speakers as well as the amplifiers behind an acoustically transparent curtain.

What about the definition of "good"? Rather than get into a controversy of opinions, lets indicate, for the sake of this discussion, a few measurements that most could agree with. Response is flat 20-20kHz within 1 dB, distortion is less than 0.3%, damping factor is greater than 10 and it is free from ringing or oscillation.

I should point out that most amplifiers depart from flat at the frequency extremes of 20 Hz and 20 kHz. These are areas that can have a wider tolerance without being audible. An article was published in Audio, July 1994 titled "Speaker cables: Measurements Vs Psycho-acoustic data" by Edgar Villchur. The psycho-acoustic data shows that for pure tones at 16kHz the smallest just noticeable difference in level is 1.31 dB. He also indicates: "It can be predicted that at a given level the just noticeable difference will be increased by a significantly greater amount by the masking effect of musical sound below 10 kHz."

Like other things in life, including us, amplifiers can be more than just good or bad. The Aristotelian world declares that things are either black or white, plus or minus, with no middle ground. The real world shows that there are all shades of gray in between. Amplifiers can range anywhere from good sound to bad sound. There may even be a twilight zone in between where we can't really decide.

Listening tests must be done without any of the amplifiers being overdriven. Amplifiers can sound different if they are overdriven and produce distortion. They clip differently due to individual linearity characteristics in the output stages or other sections regardless of whether they are tube or solid state. The various harmonic and intermodulation components can be measured and heard. For some amplifiers, high distortion can occur very abruptly while in others it may gradually increase as the amplifier is increasingly overdriven. The former is sometimes referred to as hard clipping and the latter as soft clipping.

In any case, overdriving an amplifier causes distortion that is undesirable no matter how the clipping occurs. It can cause excessive heating of the amplifier components and produce undesirable distortion in the music. Worse than this, perhaps, is that the harmonic distortion components from a clipping amplifier can damage or totally burn out a mid-range or tweeter in the speaker system that it's driving. The harmonic products generated by the distortion shift the energy spectrum to higher frequencies. Experience has proven that a higher power amplifier in the same situation will not damage the speakers, simply because it isn't driven into clipping.

Incredible as it may seem, some people are used to listening to distortion. For example: when tubes in an old amplifier have such low emission it can deliver only a few watts and it goes into distortion at a very low listening levels. Even worse, when the new tubes are put in, the same people don't like it because it isn't what they have grown used to.

Some amplifiers can sound different on the same speaker. They may have high internal impedance (low damping factor) that may be undesirable. If the internal impedance of the amplifier is high, let's say greater than 1 ohm, and the speaker impedance varies widely with frequency, let's say from 5 to 50 ohms, the response of the speaker may vary slightly. It will follow the speaker impedance curve. This may only be + or - 0.5 dB from the speaker's normal response, but frequency range affected is usually wide enough to be audibly different compared to being driven by an amplifier having a low internal impedance of let's say 0.1 ohms or lower. Amplifiers with low internal impedance are essentially not sensitive to speakers with wide impedance variations. However, when driving a speaker that has constant impedance with frequency, both amplifiers can sound the same.

It's conceivable that a speaker could be designed using an amplifier with high internal impedance (low damping factor) This means if there are impedance peaks and dips in the speaker, they can cause corresponding peaks and dips in the response that could be used to complement the driver output and provide an overall smooth response. The amplifier then becomes part of the system design. Of course, the higher the internal impedance, the more pronounced the response peaks and dips would be. The consequence is that the speaker can only be used with an amplifier with identical internal impedance to the one used for the design. Otherwise, when driven with an amplifier with lower or higher internal impedance, the system will not have the response that it was designed for.

A requirement similar to this was once specified by Ed Villchur at Acoustic Research for the AR woofer. He claimed that it worked best with an amplifier having a damping factor of one. Later, he no longer stated this requirement.

Did you catch the words at the beginning? Good amplifiers can SOUND the same. There's more to an amplifier than how it sounds. The lowest priced "good amplifier" is not always the best value. Added value comes with the manufacturer's reputation and the reliability of the product. If you're using a McIntosh amplifier with Power Guard, special circuitry in the amplifier prevents clipping. This avoids damage to the amplifier and/or speakers and maintains pleasant listening at high power with low distortion. In addition, there's the visual aspect of pleasing appearance that goes along with pride of ownership and prestige. High resale value can also be a factor if you later want to upgrade to higher power or a later model. Availability of service and parts may also be a consideration, particularly for older amplifiers.

Generally, good reliable tubes, and in particular output tubes, are hard to find that enable an amplifier to meet it's original distortion specifications. They are often very expensive and sometimes don't last very long.

Lightning strikes cause rapidly expanding and contracting electromagnetic fields, which induce electrical currents in nearby wires and electrical equipment. While vacuum tube equipment is relatively unaffected by such induced currents, solid state electronic devices can be easily damaged. In fact, a semiconductor microprocessor can be damaged by a nearby lightning strike even if it is not in use or plugged into a wall outlet or phone line.

The connection between the power amplifier output terminals and speaker input terminals is almost always a pressure device of some sort. It's unfortunate that these important connections are determined by to how tight you can turn a binding post or screwdriver or by the pressure of a spring which holds the speaker wire against the metal of the terminal. The metals that are forced against each other are often different. They might be brass or steel but plated with other metals. The wire could be copper or silver and perhaps coated with solder containing tin. They expand and contract differently with temperature. They can also become oxidized over time and the connection can become bad to the point where the resistance is significant compared to the resistance in the rest of the circuit. Dissimilar metals can also promote corrosion with action like a battery when they are in a humid environment. This eventually causes not only higher resistance but also clearly audible distortion as if a diode were inserted in series with the speaker and amplifier.

Suppose you have a system with adequately heavy speaker wire but the connections have gone bad over time. Simply removing and cleaning the wires and terminals and reconnecting them can make an audible difference. Incidentally, this is what can happen if the old wire is replaced with a new "miracle" speaker wire. By disturbing the terminals this can "accidentally" improve the contacts when the new wire with its clean surface is installed. A difference can be heard but not because of the new wire. The same change can be heard by simply cleaning the old wire/terminal contacts and reconnecting them.

Ah, you say gold plating takes care of all that. That isn't always true, particularly if the wire is tinned with solder, which is at least 50% tin, and the connecting post is gold plated. Here's what J. J. Whitley, Research Associate at AMP Incorporated (a well-known connector manufacturer) has to say about mating tin-plated contacts with gold. "In most cases, lubricated tin contacts can be mated with gold-plated contacts. This combination works as long as the conditions of contact force and stability for tin contacts are met."

"There is one major exception--where the service conditions involve wet or humid environments. Under these conditions, the gold-tin bimetallic junction is subject to galvanic corrosion. Generous application of protective lubrication is one way to alleviate this problem."

It would seem logical that instead of connecting the output wires inside the power amplifier to the output terminals, the wires should be wrapped and soldered directly to the speaker wires. Then, in turn, the other end of the speaker wires should be wrapped and soldered directly to the speakers, or crossover network. This is not practical, of course, unless the amplifier and speaker are integrated in the same cabinet.

The question here is do we need two subwoofers or one? We have been told by some people who are not burdened with knowledge: "Don't worry about 'stereo bass' --it doesn't exist in many recordings. Practically all of the low bass in a movie soundtrack is recorded in mono, and even if it weren't, low frequencies are mainly non-directional." Stereo Review January 1966 (See note 1)

The reply to my complaint is in Stereo Review April 1966 (see note 2). It's about the author's assumption that most bass is mono and therefore not important enough to warrant two subwoofers. He says: "With regard to phase, when I switched the stereo test signals into mono they sounded virtually the same. At these low frequencies the effects of the resonances and reverberation time of the listening room began to overpower the direct sound at the listening position, and there is insufficient "separation" of human ears at these frequencies for there to be large difference in the signal. Changing to mono can be plainly audible when very low frequency signals are heard through headphones but not in normal listening rooms"

Of course, I'm talking about audible differences in the same room playing the same recording and I can easily hear differences in deep bass in stereo compared to mono regardless of room effects. If I can hear them, I'm sure most people can hear them. Of course, there's all shades of gray where at other low frequencies phase differences have various degrees of being in or out of phase. This serves only to make things even more audible.

In AudioScene Canada, Andrew Marshall wrote: "If phase coherency is in, it doesn't seem to have occurred to many makers of subwoofers. Their solution has been to simply avoid the question by combining the channels below 100 Hz for the single subwoofer." (See note 3)

To go even further, at these frequencies we can even feel the sound waves as well as hear them. It depends, of course, on how the recordings are made. For example: some stereo recordings are made with two microphones at the same place, but pointing in different directions (coincident microphones) and there are no low frequency phase differences. Other recordings are made with microphones as much as 20 or 30 feet apart and there are significant low frequency phase differences.

In Audio, February 1994, John F. Sehring wrote about the advantages of Stereo Subwoofers "With out-of-phase signals, a mono subwoofer may give you less bass than no subwoofer at all." (See note 4)

In a good two or three microphone stereo recording, bass information can arrive at different times at each microphone. The arrival time at each microphone can be such that at some very low frequencies the sound is 180 degrees out of phase. If you combine these frequencies into mono, the result is zero output at those frequencies. This means if you have a 32 Hz organ pedal note that has a phase difference of 180 degrees between channels, you will get nothing and feel nothing, except perhaps hear a few harmonics. I think even a deaf person can feel the difference between a 32 Hz note being present or not!

But what if you play mono bass out of left and right subwoofers. Won't there be cancellation at certain deep bass frequencies? Yes, there can be but you would have to be sitting very close to only one of the subwoofers to get significant phase differences at the very low bass frequencies. There would need to be a path length difference from each subwoofer to your listening position of 8 feet at 70 Hz to get complete cancellation. At 32 Hz the difference in distance would need to be 17-1/2 feet. We normally sit at or near the center where the distances are almost equal. Room acoustics are then much more significant. Further, The subwoofers can be placed to the inside of the main speakers (closer to the center) to make the difference completely negligible and without deteriorating the deep bass stereo.

There are two ways to observe low frequency phase differences. Most McIntosh preamplifiers have a mode control that can be set to seven different positions including stereo and mono. By switching from stereo to mono sometimes a loss in deep bass can be heard, particularly if you turn up the loudness control. In that case phase cancellation of the program material is taking place. A single subwoofer is inadequate for that program material.

Another more scientific approach is to use a McIntosh MPI4 or an oscilloscope to display Lissajous figures. An adjustable electronic crossover having a rolloff of 24dB/octave and set to an 80Hz crossover frequency can be connected between the preamp output and an MPI4 or oscilloscope. This will eliminate much of the higher frequencies and make the deep bass easier to see. For the MPI4, push the Stereo button. For the oscilloscope, connect one stereo channel to the horizontal input and the other channel to the vertical input. With the preamp in the mono mode adjust the MPI4 or oscilloscope gain to display a 45-degree straight line.

Switch the preamp to the stereo mode. Any phase differences between channels will depart from a straight line and have a circular motion. When deep bass is heard, a corresponding pattern may be seen. If there are no phase differences, the pattern will remain a straight line. Different recordings will show a different variety of displays.

In my experience, deep bass does not occur very often, perhaps only 5% of the time, but when it's there it's most impressive and I don't want to miss it. If you are concerned about accuracy for all types of program material, and who knows how a recording has been mixed, two subwoofers should be used, one for each channel. How many of us use our home theater system to play our older stereo recordings as well as movies? Please raise your hand! Thank you. If you're using full range speakers on the left and right front channels and no mono subwoofer, you got it right!

In addition to the problems of combining left and right channels into mono, some people maintain that deep bass is non-directional and therefore subwoofers can be located anywhere with respect to the main speakers. What constitutes a deep bass frequency? In truth, the crossover frequency determines if this can be heard or not. Suppose you have the main speaker and the subwoofer separated by two meters. Perception of the different locations of this wide-range sound source occurs when the distance between the speakers is greater than 1 meter. A paper presented some time ago at the Audio Engineering Society by General Electric shows that only a few people are able to consistently perceive separate sound sources as low as 70Hz. As the frequency increases, however, more people are able to tell the difference. By 150Hz most people can distinguish this. If a crossover frequency above 70 Hz is used for a subwoofer, stereo imaging accuracy can decrease because the image is smeared between the subwoofer and the main speaker which is also radiating the same frequency. Keep in mind that a 70 Hz crossover doesn't mean that the woofer output suddenly dies at 71 Hz. It can continue to radiate through 80 Hz or 90 Hz or even higher depending on how sharp the crossover rolls off the higher frequencies. When using higher crossover frequencies, each subwoofer should be kept less than one meter from the main speakers.

Many years ago, Harman-Kardon began emphasizing the importance of square wave response in audio electronics. Today, the term "square wave" is no longer being used but a more obscure term called "fast" is used. Capacitors, speakers and amplifiers, etc. are referred to as being fast or perhaps slow. The implication that something might be slow in today's world of faster computers would be undesirable. Fast computer processing time is, in fact, desirable. Audio system response and hearing requirements are something entirely different.

A square waveform rises infinitely fast, holds at constant amplitude and then falls infinitely fast to an equal negative value, holds at constant amplitude and then rises infinitely fast to repeat over again. A square wave signal can be generated electronically and can cover a frequency range from of 20Hz to 20kHz or even wider. It can be applied to a preamplifier, power amplifier or other audio equipment and the resulting output observed on an oscilloscope.

Harmonic analysis of a square wave shows that it is made of an infinite array of odd order harmonics that decrease in amplitude. It consists of the fundamental frequency that has an amplitude of one. The 3rd harmonic has an amplitude of 1/3 of the fundamental. The 5th harmonic has an amplitude of 1/5th of the fundamental, etc. The fundamental and each of these harmonics can be thought of as a pure tone or what is called a sine wave. The lower harmonics are the most significant in contributing to the shape or "speed" of a square wave and the shape of the leading and falling edges. As the harmonics get even higher, the less they contribute until they become negligible.

As a rule, the bandwidth of an amplifier that will reproduce a good looking square wave must extend from 1/10th of the fundamental frequency of a test square wave to 10 times its frequency. For example, if an amplifier passes a 2000 Hz square wave without distortion, the amplifier can be assumed flat from at least 200 to 20,000 Hz.

But what if a 20kHz square wave is applied? Should the amplifier output also be a square wave? The third harmonic is 60kHz and the 5th harmonic is 100kHz. This is fine if the amplifier has an application for ultrasonics or some other industrial use. For human hearing, an output of only the fundamental frequency at 20kHz, a sine wave, is needed. We don't hear beyond 20kHz to appreciate the ultrasonic components. Any amplifier that has flat response from 20Hz to 20kHz is "fast" enough to reproduce audio accurately.

Amplifiers having extended bandwidth to 500kHz or more can encounter a new set of problems by picking up radio frequencies from local radio stations. This can interfere with the audio signal or be detected as in a radio. The radio program can be even heard through the system. That problem can be overcome by circuit shunting capacitors that reduce the bandwidth but not low enough to affect the audio bandwidth of 20Hz to 20kHz.

So why do companies make amplifiers that go beyond 20kHz? When feedback was introduced in audio amplifier design, one of the benefits was a broader frequency response along with reduced gain and lower distortion. Extended bandwidth to 100kHz or 200kHz was inherent with the application of feedback. This was for free, so to speak, and provided a step above other advertising claims, even though it couldn't be heard. Of course, there were the inevitable followers who thought this was audible. Their claim was that the associated phase shift of a 20kHz-limited amplifier was audible. It isn't.

Gordon Gow at McIntosh pointed out that acoustic square waves do not exist in nature. Even if they did exist, they couldn't propagate through air, which is a differentiating medium. At one time we investigated what we thought to be some things like a pistol shot, wooden block and spark gap. A 1/4" Bruel & Kjaer 4135 microphone having response to 100kHz was used along with a Tektronix storage oscilloscope to display the rise time. Perhaps the most promising was striking two small pins together directly in front of the microphone. Fast rise times shorter than 12 microseconds just weren't there. That's the rise time of a 20kHz pure tone or sine wave and represents 1/4 of the wavelength at that frequency.

The term "fast" becomes even more distorted when it is used to describe woofers. As in the electronics, to fulfill the "fast" requirement, a woofer must have a wide bandwidth, yet woofers are designed intentionally to have only a narrow bandwidth so that a smaller mid-range or tweeter can better radiate and disperse the higher frequencies. A "fast" woofer is therefore undesirable because it will radiate into the mid and high frequency bands and cause interference. The result is uneven response and directional peaks and dips.

Quoted directly from a catalog.

1. Tube speakers sound better. The speaker doesn't use permanent magnets that change with age and deteriorate the sound quality. It uses a specially wound copper coil that energizes the magnet structure. You can select the current in the power supply to control the magnetic field in the voice coil gap. You can choose several different magnetic damping characteristics. You can have an overdamped condition that has high efficiency but relatively little deep bass, a critically damped speaker that has moderate bass and efficiency or an underdamped speaker that has greater relative bass but lower efficiency. This method of controlling the speaker does not waste power like inferior methods that use a series resistor in the voice coil circuit.

2. You can't demagnetize the magnet assembly by overdriving it like some permanent magnet speakers. If the voice coil flux exceeds the magnetic characteristics of the iron pole piece, the gap flux is automatically restored by the heavy duty power supply as soon as the overdriving signal is removed. No permanent loss of output can ever occur.

3. This speaker has a tube power supply. The speaker won't come on right away because there's a warm up time for the power supply voltage to build up. This will eliminate any turn-on pops and clicks in case you're using a solid state component with this problem. The tube speaker power supply offers all the advantages found in power amplifier and preamplifier tube power supplies.

4. The tube power supply and copper coil is more expensive than an inferior permanent magnet speaker, but the benefits outweigh the cost.

5. The unique cabinet style gets rid of the conventional looking box appearance. The genuine hardwoods add a special elegance to the room decor. The colorful flower pattern of the grille enhances any home environment and is particularly acceptable to women who hate plain ugly black grille cloth in their home.

6. Operation is for 115VAC and 60 Hz. The power supply works very well with line conditioners that reduce harmonics, voltage fluctuations and "spikes".

Of course, all these words don't change what the speaker was 70 years ago. It really doesn't tell us how it sounds. How true are the statements I made? Well, some have a basis in fact but they're not the whole truth, which perhaps is more misleading than a lie.

1. A tube power supply for a speaker field coil, of course, doesn't make any improvement in the sound. Although a variable current power supply feature can control the flux in the voice coil gap, this may never have been a feature used either in speaker power supplies or radios having field coil speakers.

2. This is true but isn't the whole truth. A permanent magnet loses a tiny portion of it's strength right after it is magnetized but then it stays constant indefinitely. However, driving the voice coil with very high power can radically demagnetize a few alnico magnet speakers. I have done this. Ceramic magnets are almost impossible to demagnetize this way. The voice coil would burn out first or perhaps bottom and deform.

3. Magnetic flux is the same whether from a coil or permanent magnet. Field coils are more expensive because of the copper wire and the necessary power supply. In old radios the power supply for the tubes was also used for the field coil and a separate field coil power supply was not needed. The cost could therefore be kept lower. The permanent magnet works just as well and doesn't require a power supply or UL approval and greatly reduces the cost.

4. There are no advantages to a tube power supply that can't be done better and more reliably with diodes and a thermistor to delay the voltage buildup. Better yet, no power supply or coil or tubes at all.

5. It's true that many housewives and interior decorators would not like to see the speakers at all. Perhaps the gothic appearance of this speaker isn't as appealing today, but it may have been back then.

6. A line conditioner is not necessary. It neither enhances nor hinders the operation but is an added expense. However, if the conditioner helps to protect against line surges and lightning, it could be otherwise useful.

I'm sure that pages and pages of words can be added to the above example that I have suggested. The point of this ad is that it's easy to make up all kinds of claims and if no one can prove they're wrong, then they must be true. This kind of reasoning is faulty and is again Aristotelian in nature.

In formal logic it is the burden of the person making the claims to prove they are true. How many times have you bought a new component that has been praised up and down with words glorifying it's appearance and performance only to find it isn't as good as you were led to believe by reviews and advertising? Perhaps this attraction is based on appeals to tradition, authority or just plain blind faith.

It's common practice when reporting on a particular subject to first gather related facts about the subject. The next step can be to edit and select only the facts that support the point that is being made and ignore the rest. This goes for advertising, news writing and many other categories. For the experienced reader who is knowledgeable on the subject, the missing information will be noticed. For others who have no direct knowledge, the limited facts can create an entirely different story, sometimes in direct opposition to what would have been created if all the facts were mentioned.

This narrow tunnel vision is not unusual. We tend to see and hear only what we want to see and hear particularly when it supports our own opinion. A person's opinion can be different at different times, in the same way that what they see and hear is different at different times.

Superstition isn't just for those who believe in ghosts, flying saucers, faked moon landings and that the earth is flat. It has also invaded audio. This is particularly true for those who don't understand scientific thinking. The truth for some people has become a fad that rejects science and reason. It's a waste of time trying to convert the dedicated believers, but others may be willing to listen.

The opposition to these facts reminds me of a story where a research team came to investigate some lights that were seen at night by people in a certain area. They were opposed to the objective findings of the team saying that they didn't want to know the cause of the lights. They preferred the mystery and to think that the lights might be from alien spacecraft.

Here are some claims that are opinions and not facts.

Tubes sound better than solid state.
Expensive speaker wire is better than inexpensive speaker wire.
Digital watches interfere with CD players.
Green markers applied to the perimeter of CD's make them sound better.
There are some things that can't be measured that make the difference.
A special audio brick placed on your amplifier improves the sound.
Hookup wires are directional.