Home audio & video forum: 75 Watts RMS.. what does it actually mean

RMS
Literally "root mean square." A DC voltage that will produce the same heating effect (power output in Watts) as the AC voltage. For a sine wave, the RMS value is equal to 0.707 times the peak value of an AC voltage. Example: divide Peak-to-Peak by 2 (or in half) and multiple by 0.707 = RMS voltage.

If 75w.RMS is not the total power of the system but rather the individual outputs then that should be plenty for the HTS.

don't even bother with PMPO. there is no IEEE standard or anything for that... PMPO is mostly a marketing ploy to make your 75 watt speaker system sound REALLY powerful. stick with the RMS.

this is an advertisement stunt as u said meaningless.

no user can measure the peak music power output

earlier practice of rating in RMS power is more meaningfull

really the acoustic power output of the speakers is what actually matters

then they will have to rate equipments in terms of
decimals of a watt to few watts

as this also is not measureablr to end user this also will not give an idea about the sound output requirements of user

from experience i have seen an equipment rated 10 Watta RMS into 8 or 4 ohms speaker is more than ample for any home use.

finally more depends on the speaker quality and its effeciancy is more important for real sound output
ramaswamy

If it 75 watts RMS per channel it shoud be fine. If it is 75 total system power forget it. Only the RMS figure has ANY MEANING, the others are usless. John

Hi There,

Its hard for me to explain what exactly 75 Watts RMS means, but it refers to clean power/wattage. Forget about what you hear of read in stores regarding 1000 watt receiver/amp/speaker. 75 watts rms is good for a home speaker, 100 watts rms is even greater. You dont really need anything more powerfull unless you are installing a boom box in your car. My back speaker in my car which are 6.5 inch round push 120 watts rms and they are very sufficient and capable of doing a great job. You will be satisfied with 75 watts RMS. Maybe you should consider something like 100 watts RMS. If your a audiophile like myself, you may see yourself returning the 75 watt speakers for something like 100. Hope this helps a bit.

Pete

I used to design audio output transformers. A very fine
am-fm radio could generate 6 to 8 watts rms power across the frequency spectrum. 8 watts will blast you out of your office and be objectionable to others around you.

In engineering terms, the Peak Power is double the RMS power. But, this applies for a single frequency.

When you consider peak power over a range of frequencies, like in an audio system, its not that simple. At any instant, the output signal has a band of frequencies and the instantaneous power is the sum of powers of all the frequencies.

There is no standard for relating the RMS power to the so called Peak Music Power Output (PMPO), a term created by the Japanese as an advt. gimmick. I have done some hands on measurements and have noticed that the PMPO can be anywhere from 4 to 12 times the RMS!

The real specification of an audio system will mention the output in terms of RMS / per channel into a specified load at a specified Total Harmonic Distortion (THD). It will also mention the frequency bandwidth at which the power will drop to half the rated value( 3 dB).

I would say that for a High End home theatre system, 30 Watts RMS for the Sub Woofer and about 15 Watts RMS per channel is good.

This is one thing that gets neglected in most discussions. The total power output as stated is 75 watts RMS. Now if this is a 5.0 system, there are more things left unsaid. Watts per channel needs to be spelled out as most rear channels are at a reduced wattage. Most likely divided as thirty watts per channel for the front and five watts for the rear pair and the center. This could be any combination that totals 75 watts. Power is voltage times current but the resistance of the speakers causes changes in the voltage as a lower resistance will give you a higher current but lower wattage. Putting speakers in parallel reduces the impedence and could cause much smoke in the amplifier final stages.