The Beta 50 and 40 have the same Sensitivity (2.83V @ 1m) of 91dB. So whats up with your numbers. If you were just using those numbers for examples, then you must know it takes twice the power to get 3dB increase, so for a 1.5dB increase it will take 50% more power for the Beta 40s to play at that dB.
You cannot compare MPG to AMPS. Receivers cannot make more power. That is like saying I have a 250hp engine and I get 300hp to my back wheels. Wiggle room..what? Watts and AMP are measured by the US Goverment called UL Listed. These are real numbers with no wiggle room.
RMS has nothing to do with Frequency. If you are willing go to ( http://en.wikipedia.org/wiki/Audio_power
) to see what RMS is.
RMS Values and Measurement
July 18, 1996
The following is to help alleviate confusion about measurement of RMS (Root Mean Square) values of AC voltage.
RMS, or Root Mean Square, is the measurement used for any time varying signal's effective value: It is not an "Average" voltage and its mathematical relationship to peak voltage varies depending on the type of waveform. By definition, RMS Value, also called the effective or heating value of AC, is equivalent to a DC voltage that would provide the same amount of heat generation in a resistor as the AC voltage would if applied to that same resistor.
Since an AC signal's voltage rises and falls with time, it takes more AC voltage to produce a given RMS voltage. In other words the grid must produce about 169 volts peak AC which turns out to be 120 volts RMS (.707 x 169). The heating value of the voltage available is equivalent to a 120 volt DC source (this is for example only and does not mean DC and AC are interchangeable).
The typical multi-meter is not a True RMS reading meter. As a result it will only produce misleading voltage readings when trying to measure anything other than a DC signal or sine wave. Several types of multi-meters exist, and the owner's manual or the manufacturer should tell you which type you have. Each handles AC signals differently, here are the three basic types.
A rectifier type multi-meter indicates RMS values for sinewaves only. It does this by measuring average voltage and multiplying by 1.11 to find RMS. Trying to use this type of meter with any waveform other than a sine wave will result in erroneous RMS readings.
Average reading digital volt meters are just that, they measure average voltage for an AC signal. Using the equations in the next column for a sinewave, average voltage (Vavg) can be converted to Volts RMS (Vrms), and doing this allows the meter to display an RMS reading for a sinewave.
A True RMS meter uses a complex RMS converter to read RMS for any type of AC waveform.
When taking readings with a non True RMS reading meter, a 120 Volt RMS sinewave will still measure about 120 volts RMS. This is because the meter uses the mathematical relationships shown below to give a proper RMS reading for a sinewave. However if used with a modified sinewave or square wave these meters will only read about 90-105 volts. Don't be misled, there is nothing wrong with the inverter or the meter, and to prove this try the following test. plug in a normal light bulb and check its brightness. If there is only 90-105 volts RMS available it will look orange as it would during a brown out. If it appears to have normal brightness the voltage is approximately 120VAC RMS.
You can see that improper measurement can easily lead someone to believe that a modified sinewave or square wave inverter is not putting out its rated power. For example, remembering that Power = Volts(90-105) x Amps (33) a 4000 watt inverter (24VDC input) would measure out at about 3000-3500 watts if a proper true RMS reading is not taken.
Normally True RMS reading meters are very expensive, such as the Fluke 87 series meters. However, Radio Shack now offers two models priced under $90.00. Check with Radio Shack for details and features.
A few handy things to keep in mind about RMS values that apply when dealing with a sine wave, are as follows:
Peak Volts AC x .707= Vrms
Vrms=1.11 x Vavg
1.414 x Vrms= Peak Volts AC
Vavg= .637 x Peak Volts AC
For a modified sinewave or square wave these equations do not apply, and the easiest way to deal with this is to invest in a True RMS reading meter. (For a square wave Vavg, Vrms, and Vpeak are all equal.)
This article was originally written and published by Trace Engineering, now owned by Xantrex Technology, in July 1996.
I dont want to start a pissing match, however I do want to learn as much as I can. So if you are willing, please take my commits with a grain of salt.
So a amp that only pulls 4amps of power like the Pioneer 74 and 72 can have its power supply taxed harder when powering muti. channels. Compared to the Denon 3805 that pulls 7.1amps. There is a sound difference between the two receivers. The Pioneer does not have as warm of a sound as the Denon or Marantz. You will lose some detail in your mid range. Listen to different receivers and you will hear what I am talking about.