Taralabs cables

Sound pressure readings are made using a special microphone probe and a meter that resembles a tape recorder's VU meter but is calibrated in dynes/cm2 of pressure or in decibels above the threshold of human hearing. The sound meter shares the same shortcoming as a VU meter in that its indicator needle, having some inertia, does not respond fully to transients, but gives an average (or RMS) reading.
The RMS level of sound during an orchestral crescendo, as heard from a fairly close seat in the concert hall (row C, for instance), measures about 100dB on a sound level meter. The acoustical power (not electrical, please note) needed to create this sound level, at a distance of 15 feet from a loudspeaker in a 10' by 15' by 20' room, is on the order of 0.4 acoustic watts.
If we used a 100% efficient speaker (which is unlikely, because there's no such thing), we could recreate the RMS power of the original sound with 0.4 watts of electrical power. To find the amplifiet power required to get this acoustical power from a practical speaker, we simply multiply the reciprocal of the speaker's efficiency rating (in percent) by 40. Thus, for a 10% efficient speaker, we have: 40 x 1/10W, which works out to 4 watts. For a typical "low-efficiency" speaker of about 1% efficiency, we would need 40 watts of amplifier power to produce 0.4 acoustical watts.

The power figure derived by the above calculation represents the minimum amount of RMS power needed to reproduce an orchestral crescendo at its original measured sound pressure. The figure will apply as a total power requirement for both channels of a stereo system, but it will not apply for a monophonic system, because mono sound of a certain measured pressure level does not sound as loud as the same level when the reproduction is stereophonic. This means that, in order to reproduce monophonic material at the subjective level encountered in the concert hall, we need more power than would be indicated on the basis of sound level meter computations.
How much more is a moot point, because the disparity between stereo and mono power requirements varies with the program material, the way it was microphoned, and the acoustics of the listening room. It usually works out to about a 1–2dB difference, which seems negligible until we remember that it takes double the power to raise the listening level by a mere 3dB. To cope with a 2dB increase, we must up our original power estimate by a factor of about 1.6. Hence, if our original figure came out to 4 watts, we would have to multiply this by 1.6 to get our power requirement for monophonic listening, and this would come out to 6.4 watts for the 10%-efficient speaker.

The formula that we described for arriving at our minimum RMS power figure assumed that the loudspeaker radiated its sound in all directions away from the source. In truth, some speakers don't. The best loudspeakers for small-room listening are direct-radiator types, simply because they do radiate the sound over a broad area. But horns. which usually behave best in very large rooms, tend to direct most of their output forward, so a higher proportion of the radiated sound goes directly toward the listener. This would tend to reduce the power requirement even more for a horn-loaded system, but the high efficiency of the average horn puts its power requirement so low to begin with that it is pointless to quibble over an extra watt or two, even though this may represent a doubling or halving of the computed figure.
An orchestral crescendo, or a full choral passage, contains transients that are fully 10dB higher than the average volume of the sound, as measured by a sound level meter. A 10dB increase in level represents a 10-fold increase in power, so how can we possibly hope to cope with this sort of thing? Fortunately, we don't have to. Recording studios and broadcast stations use peak limiters to keep these huge transients out of the received signal, and tape recorders have their own built-in limiting action. Transients are high- frequency phenomena, and tape will saturate instantly if a strong treble impulse is fed to it. The result is a shearing-off of the peak, and if the overload doesn't last too long, this won't cause any more audible disturbance than a good peak limiter.

Thus far, we have fairly well established the power that we must have in order to avoid outright overload when reproducing original orchestral level through a speaker of known efficiency. But it is not all the power we should have on hand, because there’s more to fidelity than just reproducing sound at the proper volume.
Anyone who has perused an amplifier’s power-vs-distortion curve will have noticed that distortion rises gradually with output until just below the overload point, beyond which the distortion skyrockets. This is one reason why a high-powered amplifier is likely to sound better than a low-powered one even at every low power levels. They may both be operating at well below their overload point, but the fact that the high-powered one is running at 1/10 of full power when the other is at 8/10 of full power will mean that the former is contributing less distortion at all times  and this will generally show up as cleaner, more "comfortable" sound.

There's a second reason why high-powered amplifiers should outperform low-powered ones, even at low output levels. It is customary to equip an amplifier with an output transformer that is no larger than it has to be in order to yield full rated power in the middle range. The British are still making low-powered amplifiers with substantial output transformers, but the prevailing attitude in the US seems to be that the low-powered amplifier is sort of a stopgap component, to tide the buyer over until he can afford to purchase something good. There is rarely any attempt to design a really good low-powered amplifier. As a result, the typical 10-watter, even though it may well meet its rated power at 1kHz, is severely limited in power capability at both ends of the spectrum. The power loss is usually most severe at the low end, where there is often a great deal of energy in the audio signal, so the unit may only be able to deliver half, or less, of its rated power before the program material overloads it