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How important is RMS for selecting an Amplifier?

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jay

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Hi,

I would like to know how important is the term RMS when we intend to buy a stereo amplifier.

Say for Yamaha AX 397 priced at 17,000/- has 100W RMS per channel whereas a Marantz PM6002 priced at 28,000/- has 60W RMS per channel.So why is this difference?What value addition does RMS give and whether we should buy higher RMS Amps or prefer lower ones.

Please suggest.
 

spirovious

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Hi,

I would like to know how important is the term RMS when we intend to buy a stereo amplifier.

Say for Yamaha AX 397 priced at 17,000/- has 100W RMS per channel whereas a Marantz PM6002 priced at 28,000/- has 60W RMS per channel.So why is this difference?What value addition does RMS give and whether we should buy higher RMS Amps or prefer lower ones.

Please suggest.

I will put in simple way.
RMS is unit to caculate power of amp.Higher the number better the power.

But actual power needed depends on the speaker.If speaker is more sensitive ,less power is required to drive it.Sensitivity of speaker indicates the
sound pressure delivered by speaker.ie movement of spk driver.
eg. 86db spk may need 100w rms power whereas 90 db spk will be loud with 50w rms.

Secondly you have to check clearity of amp.
You can check THD of amp.Lesser the no.more good the amp.
Then S/N ratio-more is good.
 

jay

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I will put in simple way.
RMS is unit to caculate power of amp.Higher the number better the power.

But actual power needed depends on the speaker.If speaker is more sensitive ,less power is required to drive it.Sensitivity of speaker indicates the
sound pressure delivered by speaker.ie movement of spk driver.
eg. 86db spk may need 100w rms power whereas 90 db spk will be loud with 50w rms.

Secondly you have to check clearity of amp.
You can check THD of amp.Lesser the no.more good the amp.
Then S/N ratio-more is good.

Well if higher the number of RMS better the power THEN how will it be useful for the amp?Does more power means I have a better amp?Does it make any difference in the end output?

Also when i need to match speakers with the amp I have I am told that the RMS of speakers which I chose should always be more than what I have in the AMP.Is this correct?

Can you please explain what is S/N ratio?
 

jay

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Typically an amp from a reputed audio manufacturer will be superior in all of the above. One from a motorcycle manufacturer, may not be. It could, but it's highly likely it will not.

Do you mean to say that Yamaha as an electronics manufacturer is not at all competent in the segment which it caters to?
 

venkatcr

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Typically an amp from a reputed audio manufacturer will be superior in all of the above. One from a motorcycle manufacturer, may not be. It could, but it's highly likely it will not.

I am afraid this is a oversimplification and grossly incorrect. Yamaha Corporation, the company that makes and sells musical instruments, A/V products, semiconductors, computer products was started in 1887, long before any of us were even born.

The Company that makes motorcycles, Yamaha Motor Corporation, was incorporated only in 1955, and has nothing to do with the parent company. It is independently managed and run very successfully.

Yamaha literally pioneered many a product in the electronics and A/V field. Some of the sound chips made by Yamaha are used in legendary products such as Atari, AdLib Cards, SoundBlaster Cards, Sega Drives.

As early as 1985, Yamaha pioneered what we know as HT today with their specialised DSP chips that provided 6 channel surround sound. This was even before Dolby and DTS started looking at multi channel sound. Yamaha tape drives are legendary.

Some of the products made by Yamaha include the following:

  • Pianos
  • Guitars
  • Percussion instruments
  • Trumpets
  • Horns
  • Saxophones
  • Piccolos
  • Flutes
  • Clarinets
  • Electronic organs
  • Portable Keyboards
  • Music workstations
  • Synthesizers
  • Tone generators
  • Woodwind MIDI Controllers
  • Music sequencers
  • Analog mixing consoles
  • Digital mixing consoles
  • Digital audio workstations
  • Public address loudspeakers
  • Power amplifiers
  • Digital Processors
  • Studio monitor loudspeakers

Many famous singers will not use anything other than a Yamaha piano or a guitar. Literally every professional group, every music director in India, and every studio of some repute will have Yamaha recorders, synthesisers, keyboards, and mixers. Many of the better cinema halls in the world use Yamaha loudspeakers specially designed for cinema halls.

Yahama makes extremely good products for the A/V market. If we have competing and affordable products of excellence today in the A/V market, it is because Yamaha took a lead. They were one of the earliest to make receivers affordable, and have been ruling the market for a long long time.

Cheers

PS: As Marsilians said somewhere, I don't work for Yamaha, and have no commercial interest in any product of any company.
 
Last edited:

hemantwaghe

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Before writing what "YAMAHA" is someoone else wrote!
Anyway pls pls do not call YAMAHA as motorcycle manufacturer. They 'know " music better than anyone else.
What do you call world's biggest musical instrument manufacturer??( rf wikipedia--
Yamaha Corporation - Wikipedia, the free encyclopedia

Yamaha was established in 1887 as a piano and reed organ manufacturer by Torakusu Yamaha as Nippon Gakki Company, Limited (??????????, Nippon Gakki Seiz? Kabushiki Gaisha?) in Hamamatsu, Shizuoka prefecture, and was incorporated on October 12, 1897. The company's origins as a musical instrument manufacturer is still reflected today in the group's logo a trio of interlocking tuning forks.

Yamaha has grown to become the world's largest manufacturer of musical instruments (including Pianos,"silent" pianos, drums, guitars, brass instruments, woodwinds, violins, violas, celli, and vibraphones), as well as a leading manufacturer of semiconductors, Audio/Visual, computer related products, sporting goods, home appliances, specialty metals and Industrial robots.


Infact they had archry division which inspite of solid performance was closed down!!!

"In 2002, Yamaha closed down its archery product business that was started in 1959. Six archers in five different Olympic Games won gold medals using their products."

So pagain get your facts right!

( I have no commercial interest in Yamaha- nyway I owe Yamaha - used to own Onkyo :)
 

marsilians

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Hi,

I would like to know how important is the term RMS when we intend to buy a stereo amplifier.

It is something that you should definitely review but not take at face value since all the tests are done in stellar audio labs and also there is no standard process a manufacturer has to follow to put out those nos.

It is much better to have too much power than not enough. The easiest way to damage a speaker is to have the amplifier clip or distort because it doesnt have enough power to reproduce the input signal at the selected volume level. This is regardless of their power handling specifications.

Other things to consider are THD (Total Harmonic Distortion) which says if you ramp up the volume to high do the sounds still feel distinct and clear. High distortion means terrible sounds. This is

Basically, you will most likely never push your amp to put out its max power for more than a fraction of a second through your listening periods.

Say for Yamaha AX 397 priced at 17,000/- has 100W RMS per channel whereas a Marantz PM6002 priced at 28,000/- has 60W RMS per channel.So why is this difference?

No standards that manufs have to follow!

What value addition does RMS give and whether we should buy higher RMS Amps or prefer lower ones.

Please suggest.

I have answered this as part of first question.

Also to quote from a musical fidelity article,

Amplifier power and dB Watts

The vast majority of people have no idea of the practical connection between watts and dB watts. Let us enlighten you. Watts are simply a measure of an amplifiers heating power. There is no intuitive relationship at all to listening level measured in dB. Ignorance about the practical connection between watts and dB watts is one of the biggest causes of the problems of the business.

When we explain the basic relationship between watts and dB watts, you might begin to understand why amplifier manufacturers are anxious to sweep it under the carpet. Essentially, each dB step in sound pressure level requires a 25% increase (approx) in power. A 3dB increase requires double the power. This sounds incredible, but it is true. Perhaps now you might glimpse why amplifier manufacturers are anxious that you dont look at amplifier power in terms of what the amplifier actually does with music. Below is a chart which converts watts to dB watts.

30W 15dBW
40W 16dBW
50W 17dBW
63W 18dBW
80W 19dBW
100W 20dBW
125W 21dBW
158W 22dBW
200W 23dBW
251W 24dBW
316W 25dBW
400W 26dBW
500W 27dBW
631W 28dBW
795W 29dBW
1000W 30dBW
 

jay

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Also when i need to match speakers with the amp is it a must that the RMS of speakers which I choose should always be more than what I have in the AMP.Is this correct?
 

marsilians

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Also when i need to match speakers with the amp is it a must that the RMS of speakers which I choose should always be more than what I have in the AMP.Is this correct?

All that the speaker RMS is saying is that it can withstand that much amount of thermal energy. Due to the dynamic nature of music and movies this RMS is briefly touched upon during a scene or a song.

The best analogy is your body weight (speaker) and your car's weight (AVR). Now you see which one should be higher to carry the weight (or get sound out of the speaker).

There is no harm if you AVR RMS >> Speaker RMS

The other way is bad
 

spirovious

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Well if higher the number of RMS better the power THEN how will it be useful for the amp?Does more power means I have a better amp?Does it make any difference in the end output?

Also when i need to match speakers with the amp I have I am told that the RMS of speakers which I chose should always be more than what I have in the AMP.Is this correct?

Can you please explain what is S/N ratio?

OK.
Power is related with current that amp outputs to spk.Power=current*voltage

When you choose smaller spk ,you need less power.ie-when listening to ipod,
walkman you need very little power.If you check speci.of those,you will see
power in miliwatt.Still you can get very loud sound from device.

If you check car decks ,power required is hardly 50w.

For home use you need 70 to 100w(depending on area)
In open ground you need 1000w.

Other aspects r sensitivity(as said earlier)& impidence of spk.

Impidence is like resistance(spk coil)If imp is less (6 ohm)naturally more current will flow through spk,so more power is rquired.
So to drive 6oh spk, you need more power than 8 oh spk.
In other words check the spk impidence before you you decide amp power.

S/N ratio is signal to noice ratio-if signal unit is 100 & noice(distortion)is1
(signal/noice) then ratio will be 100(100/1)

So as we need less noice in sound S/N ratio has to be more.

Lastly as per electomagnetic theory,when amp send signal(sound) to spk,
another opposite signal is sent by spk to amp.
So amp has to cancle that signal & send newone to get mooth sound.
So if you select amp with slightly more power than spk ,its better.
 

pradski

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I got a question. I wanted to know if one particular speaker sounds different if you use same AVR with higher RMS.(Eg: between 100 rms and 150 rms AVR of same make and speaker being constant) What difference will be there. If any.
 

marsilians

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I got a question. I wanted to know if one particular speaker sounds different if you use same AVR with higher RMS.(Eg: between 100 rms and 150 rms AVR of same make and speaker being constant) What difference will be there. If any.

I dont know how you will manage this "if you use same AVR with higher RMS" because the RMS is fixed range for each AVR. If you move to another component then you will hear things louder and a bit more dynamic sound as low frequency sounds that would not ahve been heard will be amplified enough that youwill start to hear them. this is called head room in AV terms.
 

vinyl_man

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Guys,
Just a few days ago I sold my Yamaha M80. I think it was probably one of the best amps ever made.

The fact is that this thread has gone haywire.

A simple answer is- Watts indicated are never true in many cases. My McIntosh with 100 watt RMS sounds more powerful to the M80. But here is another fact-- My Rogers Vintage tube amp with 30 watts power drives my KCS 350 watt professional speakers equally good too.

In a nutshell, listen to what pleases your ears.

Isar
 
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spirovious

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I got a question. I wanted to know if one particular speaker sounds different if you use same AVR with higher RMS.(Eg: between 100 rms and 150 rms AVR of same make and speaker being constant) What difference will be there. If any.

When you take amp of same make with diff RMS ratings,definately the components used inside amp are totally different(ratingwise)
No amp is ideal.It tries to reproduce amplified sound curve closed to original properties.So you get difference in sound.

Higher rms can give little heavy sound.
 

marsilians

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But here is another fact-- My Rogers Vintage tube amp with 30 watts power drives my KCS 350 watt professional speakers equally good too.


There is a reason for low wattage tube amps to drive similar to high wattage solid state amps. It boils down to its properties.

when solid stage amps hit their max wattage, they distort rather harshly. Tubes on the other hand gradually compress the signal as their limits are reached, resulting in less distortion (i.e. making the audio more appealing).


Vacuum tubes do have more distortion than solid-state amplifiers, the distortion is of different harmonic content than the distortion in a solid state amp
 

jay

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All that the speaker RMS is saying is that it can withstand that much amount of thermal energy. Due to the dynamic nature of music and movies this RMS is briefly touched upon during a scene or a song.

The best analogy is your body weight (speaker) and your car's weight (AVR). Now you see which one should be higher to carry the weight (or get sound out of the speaker).

There is no harm if you AVR RMS >> Speaker RMS

The other way is bad

Hi,

So that means the bottomline is the RMS per channel of the Amplifier should always be more than the RMS per channel of the matching Speakers.

Please correct me if I am wrong.
 

marsilians

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Hi,

So that means the bottomline is the RMS per channel of the Amplifier should always be more than the RMS per channel of the matching Speakers.

Please correct me if I am wrong.

It need not be but its advisable to be or recommended to be.

Following is the logic (All my university education has to pay off somewhere :) )

You don't want the amplifier to start clipping out before or near the peak rating of the speaker power. Instead you want to have sufficient power to drive the speaker up to it limits comfortably with the cleanest power possible. So, to have a good listening experience, you want the amplifier to drive the speakers without much effort (which implies greater RMS)

As an aside, the concepts of speaker RMS and amplifier RMS do not mean the same at all in any sense including how they are derived the the manufacturers. So, again, don't dig too much into these values. What you shoudl look for is impedance of speakers to match the amps and Total Harmonic Distortion.

For amplifiers, you want the peak power and # channels.
 
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