Axiom Home Page Forums General Discussion Technical Questions M80 Max 400w?

I tried finding this topic by searching but after a few tries I figured it was just easier to ask the question.

In the Specs for the M80s is says that their is a max of 400w into 4 ohms. Is the 400w RMS?

So, If I understand "RMS" correctly that means when I turn the amp on, 400w will constantly be sent to the speakers without any music playing. When I play a CD/DVD the watts will increase from 400w on up, right? A loud hard charging rock song would be 400-500 watts or higher?

If I get an amp that has 400w into 4ohm will I be ok?

Thanks

No, Mike; the maximum power rating on a speaker supposedly would be the amount that could be input for an extended period without it going up in smoke. Alan has reported here a couple times that the M80s have been lab tested at as much as 1200 watts, although it wasn't said for how long a period.

If no music is playing essentially no power is sent to the speakers(maybe a tiny fraction of a watt for background noise level). At a comfortably loud average listening level the M80s use 1 watt or a bit less. The maximum on brief peaks would be much more, of course, depending on the dynamic range of the material being played, but isn't likely to be more than about 100 watts. So, don't worry about the maximum power rating of the M80; your ears would give out long before it would.

As John and Axiom employees have mentioned many times, the 80's were pumped with 1,000+ watts during lab testing with no problems. The Specs say "Max AMP power 400 watts" which is a conservative statement. This is not how many watts the 80's can handle. Most AVR's that are stated to be 100-120 watts per channel, would really read more like 80 watts or so when driven fully and lab tested.

Now my Emotiva amp is rated at a true 300 watts into 4 ohms (with all channels driven). I've never had to drive the amp to its maximum, but I can tell you at a cranked up 110dB's for short moments the 80's are just doing some stretching excercises and not breaking a sweat.

Power ratings are one of the hardest things to measure and communicate since a speaker's ability to handle power is totally determined by the kind of signal going into the amplifier and how close that signal is to "typical music". If you take a 100w amplifier and run a single, high frequency tone through it with the amp set to deliver 100w into the speakers you will probably vaporize the tweeters.

If you run a typical music signal (with a distribution of high and low notes, and varying loudness from moment to moment) and set the amp so that it is delivering 100w at the loudest peaks it will sound fine (although you may get told to turn it down ).

When you adjust the volume control on a receiver or amplifier you change the voltage of the audio signal being sent to the speakers. When you send more voltage to the speakers more current flows through the voice coils and you get more power being delivered to the speaker. The speaker transforms electrical energy into acoustic energy so more power in = more sound out.

You can use a high powered amplifier with any speaker -- it's just that you have to be careful with smaller speakers so you don't give them too much power and overheat the voice coils. With bigger speakers and higher power handling capability (like M80s) you don't have to worry so much.

Most people here (including me) will tell you that you are more likely to damage speakers by overdriving a low power amplifier than by using an amplifier that is too powerful.

I think most people run M80s with receivers in the 100W range, so strictly speaking their ability to play loud is limited by the amplifier power more than the speakers. They generally don't care, because the REAL limit on playing loud is generally either family comments or your own tolerance for loud music, and that limit usually gets hit before the amplifier runs out of power

If you have a large room and the ability to play and enjoy loud movies/music (I'm talking SERIOUSLY loud here) then a more powerful amplifier (200-400W) will let you play more loudly without distortion. Many people also feel that the more powerful amp gives them better sound when playing at lesser volumes, although this is hotly debated by people who don't own more powerful amplifiers

I would interpret the 400W power rating on M80 to say "if you have a power amplifier of about 400W/channel playing typical music, the amplifier and the speaker will start to hit their limits at approximately the same time". You don't *need* a 400W amplifier; a better statement would be "the M80s can make good use of a 400W amplifier but most people don't need that much power".

As others have posted, Axiom does test M80s with more powerful amplifiers on a regular basis, but the testing is done in an sound insulated room because it's just TOO DARNED LOUD otherwise.

On the other hand, the 4 ohm rating *is* something you need to consider. Remember I said that the volume control affects the voltage being delivered by the amplifier ? For any given voltage (volume control setting) a 4 ohm speaker will draw twice as much current from the amplifier as an 8 ohm speaker, so the same volume control setting will deliver more power into M80s than into (say) M60s.

The biggest discrete amplifiers are designed to cheerfully handle a 4 ohm load, as are the amplifiers in receivers from HK, Denon and a few others (Rotel ?). If you have an amplifier that is not happy with a 4 ohm load, the "overload protection" circuitry will kick in too early and either shut down the amplifier or limit the power you can get. In other words, those amplifiers would be able to deliver more power into an 8 ohm load than a 4 ohm load while the better amplifiers can deliver more power into a 4 ohm load.

Confused yet ?

Nice post Mr Bridgman. Let me just add to confuse it further that most of the time speakers run on 1-10watts depending on speaker sensitivity, but for transients, you know those thundering bass drums or screaming guitars, you need 10X the power to double SPL or loudness. In amplifiers gain in volume requires a logarithmic increase in power.

Its during those loud passages that you can hear if your amp is up to snuff by increased distortion or clipping. How much additional power you need will vary with the size of your room, listening habits and size of speakers.

With powerful amps and great speakers you can play very loudly without distortion or clipping. My brother visited from LA a few weeks ago and his system is kind of low fi. He just kept cranking up the volume to very loud levels (for me anyway) and saying it didn't seem very loud. He is more used to hearing distorted transients and turning down the volume than me. My rule of thumb is to get the most powerful amps you can afford. The more wattage the better. Its one reason I am eagerly awaiting the new Axiom 1500W monster amp.

Quote:

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Alan has reported here a couple times that the M80s have been lab tested at as much as 1200 watts, although it wasn't said for how long a period.

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Actually when i toured the factory, Ian noted the testing period as 100 hours, though this may have been with slightly lesser wattage, but still in excess of 700.
Factory tour

I have the M80's powered with an HK 630, which is 75w per channel. I have a 4000+ sq ft room and they will play very loud distortion free. They play louder then I care to listen to them.

Find yourself a 100w per channel amp and you should be plenty happy with the way they sound and how loud they will play.

I just realized we didn't completely answer one of the original questions...

No matter what the power rating of the speaker is, there will be zero power going into the speaker when there is no signal. The amplifier will draw a bit of power from the wall plug, but that all gets dissipated as heat in the amplifier.

jakeman: I would strongly suggest that you review your electronic math. It does NOT take a factor of 10 increase in power to increase the SPL by a factor of 2!!!!!

As for peak or transients, I have seen data that suggests that a factor of 20-25 may be required to handle the peak power requirements versus average power.

One other thing to consider is that you do NOT want your amp to clip. That COULD destroy your speakers. I didn't see that aspect mentioned on this threat, but I didn't read all the posts that closely.

This is an article from Alan and he states "The receiver must deliver ten times as much power to double the subjective loudness.".

There seems to be a lot of debate in the psychoacoustic world about "how many dB to sound twice as loud" but there's no question that the most common answer is that a 10dB change in SPL sounds twice as loud (and takes 10x the power to achieve).

Reading between the lines, it sounds as if it might take a bit less than 10dB to sound twice as loud at low SPLs, and a bit more than 10dB to sound twice as loud at high SPLs, ie even the ear's logarithmic response is only an approximation.

I do think Jakeman's original statement was correct.

I just read the article by Alan he says "The lesson in all this is that you can never have too much power , and that big amplifiers rarely damage speakers. Little amplifiers driven into clipping burn out speakers. In the scheme of high fidelity, that last barrier to realism is having enough power and being able to approximate real-life loudness levels"

I don't plan on getting an amp that puts out 400 watts, but close! Adcom GFA 7707 is what I've been looking at.

thanks for all your replies!

Mike

I think a more useful number (well, for me) is you need to double the power in order to get a 3dB increase in volume into the same load/speaker.

If you have a 87dB efficient speaker, it can play 87dB @ 1 watt (usually at 1 meter, which means less volume at your listening chair). 90dB at 2 watts, 93dB at 4 watts, 96dB at 8 watts, 99dB at 16 watts, and so on. You reach a ceiling pretty quickly, which is why, if you like it loud, speaker efficiency is every bit as important (maybe more so) as amplifier power.

The difference between a 100 and 200 watt amplifier, in total volume - all else being equal - is +3dB total volume. Of course, the more powerful the amp, the better able it is to handle transients at louder volumes. I've seen different numbers for transient peaks, with regards to required amplifier power - anywhere from 3x to 10x (i.e., if you're using 10 watts of continuous power at a given volume, you'll need anywhere from 30 - 100 watts in order to properly handle the peak transients in music/movies).

I'm going on memory, so hopefully this is correct. The gist of it is that you can never go wrong buying the most powerful amplifier you can afford. You'll never use 400 Watts continuous in real world listening, but you may need a huge reserve to handle the peaks.

wid: interesting. I have never seen the term "subjective loudness" used before. Of course, when you are drinking music tends to be played louder, MUCH LOUDER!!!!

All that said, I stand by what I post about electrical math. In electrical terms, what I said was 100% correct.

Budget: true. And, with the GIANT amp, you can always say to someone else, "mine is bigger than yours."

LOL!!!!

I want a bigger amp!!!

Budg, that's pretty much it: a doubling of power results in only a 3dB increase in the maximum sound level possible on brief peaks. The increase in level is logarithmic, not linear, so exactly the same 3dB increase occurs between 1 and 2 watts, 10 and 20 watts, 100 and 200 watts, etc. Also note that the sound level using 1 watt is actually quite loud, and is what might be used for a typical average listening level. The peak power required might vary from practically nothing more in the case of some almost uniformly loud pop music recordings to 100 times or more for very dynamic material, such as some classical items that I have.

Yeah, Bernard, the term "subjectively twice as loud" is seen fairly often, but nobody knows what it really means.

>>Yeah, Bernard, the term "subjectively twice as loud" is seen fairly often, but nobody knows what it really means.

Amen to that. Even as I was typing my last post in the back of my mind I was thinking "so what *does* <twice as loud> sound like ?"

I believe it's the incremental difference between one hand clapping and two hands clapping.

No wonder it takes 10 times as much power.

It gets even more confusing when you factor in electronic crossovers. If you have a normal HT setup, the bottom two octaves are filtered prior to amplification for the 5 or 7 speakers. The sub fills in the 20-80Hz range, using it's own amplifier. Thus, your 100 watt amp - unencumbered with reproducing the power-hungry frequencies of 20-80Hz - can now play louder and cleaner. This is one of several reasons to buy a quality powered sub - especially if you use a reciever to power all 5 or 7 channels.

I wonder if we have beat this dead horse to death??

LOL!!!