# how loud is loud?

Discussion in 'Amps and Cabs [BG]' started by pkr2, Jul 26, 2000.

1. ### pkr2

Apr 28, 2000
coastal N.C.
I have never seen so many people obsessed with loud. Everybody wants all the rated watts that they can afford from an amp so they can be real loud. People, I'm real sorry to break this to you but the wattage rating of an amp tells you ABSOLUTELY NOTHING about how loud the amp will be in a gig situation. Manufacturers have been making specs say just exactly what the consumer wants to hear for years. I.E. P-P power and peak power.

To say that a certain amount of power in electrical watts equates to anything concerning loudness is trying to add apples and oranges. Loudness is defined by the "SOUND PRESSURE LEVEL. measured at a particular distance from the speaker at a particular frequency which is determined by the efficiency of the whole system, including speakers, enclosures and to some extent, the acoustics of the room.

The wattage rating of amplifiers is calculated from the anode current of the final stage in ALL amps. Plate or cathode current in tube amps, collector/ emmiter or drain / source current in solid state amps.

Before anyone blows the money to double the wattage of thier amp they need to know that the increase in volume they attain will be negigible. You can barely tell the difference in the sound level between 200 and 400 watts of acoustic power. To double the apparent volume you would have to increase the wattage by a factor of ten. Yes, I'm saying that to double the volume of the 200 watt amp you have to generate 2000 watts of acoustic power. That is if the 200 watt amp was really putting out 200 watts of acoustic power, which it ain't.

The assumption that because you can run a tube past the point of distortion and achieve some magic increase in power is absolutely erroneous.

If a tube amp which is rated at 100 watts clean should be capable of exceeding its rating by 100% through this supposedly magic headroom it would produce 200 watts. This is only 3db. of gain if all of the electrical watts were converted to acoustic watts.

Bottom line is this simple. Sound is measured in decibels. They don't add up like some people seem to think. Twice as much is not twice as loud.

If you want to get the most db's per dollar, forget watts and think efficeincy. That's where loudness is.

Frog

2. ### SMASHGuest

Jan 18, 2000
Brilliant post man!

That can't be said often enough.

3. ### ulf_kurt

Feb 10, 2000
Umea, Sweden
OK! I get that 200w isnt twice as loud as 100w. But why is it then that my 200w amp is MUCH louder than my previous 100w amp?

(they are are both 15" transistorcombos)

cheers!

4. ### Matthias

May 30, 2000
Vienna, Austria
Frog!
You are right, BUT...
I think there is a misunderstanding what people mean by saying 'loud' too. I don't think that they all refer to the sound pressure level.
Everyone knows, that you can make a lot of NOISE with 'weak' amps too. With a little combo you can achieve a lot of sound pressure coming from the midrange, but how does it SOUND?

My guess: Most people who say that they need to be 'louder' actually mean that they want a more 'powerful' sound at say slightly increased volume. And in this case, doubling the power makes a significant difference!

I upgraded from 200W to 400W last week and A/B'd the two heads before, just to be sure that it makes sense. Now I play at the same volume as before, but with more low end and less distortion!

Another problem in this context is 'cutting through'. Many people are not aware, that you need the mids to be 'loud' in the band mix. Instead they crank the bass knob and use all their power to shake the ground. And as they don't hear themselves, they think that they need a more powerful amp, but don't know how to afford this.

So if you ain't got enough money: roll off the bass, push the mids and you will cut through with a comparably weak amp.
If you got the \$\$\$: Cut through AND shake the ground

Last thing: IMHO the RMS power rating of amps IS useful. Though it doesn't say anything about loudness, it gives a hint, of what the amp is capable compared to another. Of course this is only vague, a 150W amp might have more guts than a 200W amp of another brand, but defintely less than any 400W amp.

cheers!
Matthias

[This message has been edited by Matthias (edited July 27, 2000).]

5. ### Andy Daventry

Matthias, very good post. Very clearly put! Thanks.

Andy

6. ### Woofenstein

Jun 9, 2000
Missouri, USA
A watt is a watt is a watt is a watt, right? Maybe not. Power is equal to the voltage across the speaker multiplied by the current through the speaker. If a given speaker has 100 volts across it, and 1 amp through it, it equals 100 watts (power=voltage x current). Also, if a given speaker has 100 amps through it, and 1 volt across it, it also has 100 watts. But, current is what drives a speaker, not voltage, so the 100 amp, 1 volt amplifier will be louder then the 100 volt, 1 amp amplifier. Later!

P.S. To all you tech heads out there: I know you will never get a 100 amp, 1 volt electrical output into 4, 8, or 16 ohm speaker load. I just used those numbers to make it easier to understand.

7. ### throbbinnut

I wrote a long and drawn out reply to all this crap, and then, right when I put in my Porno for Pyros CD, my computer crashed. So here's the short and sweet reply.

"The assumption that because you can run a tube past the point of distortion and achieve some magic increase in power is absolutely erroneous."

Actually, it's not erroneous. Power into the load increases as the output signal moves into clipping, whether the amp is solid-state or tube. Yes, the maximum peak-peak voltage swing is fixed in both amps, but as the wave goes from a sine wave to a square wave with the same amplitude, power goes up. It's dirty power, but it is an increase. Try it with an AC voltmeter and oscilloscope. I have. Power is equal to RMS voltage squared divided by resistance. 100 Watt amp into 8 ohm resistor, max clean power at 28.28 volts rms. 28.28 * 1.414 = 40V peak swing. A square wave with a +/- 40V swing has an RMS value of 40V, and into an 8 ohm resistance gives 200W power. Bingo, 200 Watts RMS output from a 100 Watt rated amp, completely clipped into a square wave, of course. Notice all of the above was using a resistor, not a speaker.

Next,

"A watt is a watt is a watt is a watt, right? Maybe not. . . .
. . .so the 100 amp, 1 volt amplifier will be louder then the 100 volt, 1 amp amplifier. . . "

I'm pretty sure a Watt is specifically defined, so that's a given. A watt is a watt. The other part about 1*100 or 100*1 is really a speaker efficiency thing. But check this out, magnetic force is proportional to the current times the number of turns, so a 100 ohm speaker that takes 100 V to get 1A probably has a lot more turns than a .01 Ohm speaker that only needs 1 V to get 100A. Lets say it has 100 times more turns, now the magnetic force is the same in both coils even though the current differs by a factor of 100.

More importantly, all this is hypothetical. There are so many variables that it is useless to simplify it to the above level and then argue about it. These things are true:

-speaker efficiency determines how loud something sounds for a given power input
-spectral content determines how loud something sounds for a given speaker and power input, i.e. midrange sounds louder than bass, check out your Fletcher-Munson curves, the reason stereos have a "Loudness" switch

Oops, I wrote another long drawn out reply.

All opposing opinions will be cheerfully rejected. All opposing facts will be cheerfully accepted.

Chris

8. ### pkr2

Apr 28, 2000
coastal N.C.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by throbbinnut:
I wrote a long and drawn out reply to all this crap, and then, right when I put in my Porno for Pyros CD, my computer crashed. So here's the short and sweet reply.

"The assumption that because you can run a tube past the point of distortion and achieve some magic increase in power is absolutely erroneous."

Actually, it's not erroneous. Power into the load increases as the output signal moves into clipping, whether the amp is solid-state or tube. Yes, the maximum peak-peak voltage swing is fixed in both amps, but as the wave goes from a sine wave to a square wave with the same amplitude, power goes up. It's dirty power, but it is an increase. Try it with an AC voltmeter and oscilloscope. I have. Power is equal to RMS voltage squared divided by resistance. 100 Watt amp into 8 ohm resistor, max clean power at 28.28 volts rms. 28.28 * 1.414 = 40V peak swing. A square wave with a +/- 40V swing has an RMS value of 40V, and into an 8 ohm resistance gives 200W power. Bingo, 200 Watts RMS output from a 100 Watt rated amp, completely clipped into a square wave, of course. Notice all of the above was using a resistor, not a speaker.

Next,

"A watt is a watt is a watt is a watt, right? Maybe not. . . .
. . .so the 100 amp, 1 volt amplifier will be louder then the 100 volt, 1 amp amplifier. . . "

I'm pretty sure a Watt is specifically defined, so that's a given. A watt is a watt. The other part about 1*100 or 100*1 is really a speaker efficiency thing. But check this out, magnetic force is proportional to the current times the number of turns, so a 100 ohm speaker that takes 100 V to get 1A probably has a lot more turns than a .01 Ohm speaker that only needs 1 V to get 100A. Lets say it has 100 times more turns, now the magnetic force is the same in both coils even though the current differs by a factor of 100.

More importantly, all this is hypothetical. There are so many variables that it is useless to simplify it to the above level and then argue about it. These things are true:

-speaker efficiency determines how loud something sounds for a given power input
-spectral content determines how loud something sounds for a given speaker and power input, i.e. midrange sounds louder than bass, check out your Fletcher-Munson curves, the reason stereos have a "Loudness" switch

Oops, I wrote another long drawn out reply.

All opposing opinions will be cheerfully rejected. All opposing facts will be cheerfully accepted.

Chris
<HR></BLOCKQUOTE>"The assumption that because you can run a tube past the point of distortion and achieve some magic increase in power is absolutely erroneous."

O.K. Chris, one paragraph at a time.
That's a true statement. There is no "magic" involved. It can be explained by fairly simple physics. Agreed?

"A square wave with a +/- 40V swing has an RMS value of 40V, and into an 8 ohm resistance gives 200W power. Bingo, 200 Watts RMS output from a 100 Watt rated amp, completely clipped into a square wave, of course. Notice all of the above was using a resistor, not a speaker."

The circuit you are describing stopped being an audio amp when you subbed the resistor for the speaker. A resistor of sufficent wattage rating will not self destruct. A speaker on the other hand will self destruct almost instantly under those test parameters. Kind of the apples and oranges thing again.

"A watt is a watt is a watt is a watt, right? "
I couldn't agree more.

"More importantly, all this is hypothetical. There are so many variables that it is useless to simplify it to the above level and then argue about it."

Chris, we aren't arguing. We are having a discussion. It should be kept at a simple level as much as possible because all of us are not at the same technical level. Sorry, that was an opinion, not a fact.

All opposing opinions will be cheerfully accepted. All opposing facts will be cheerfully accepted.

Frog

9. ### Tom-Jens

Jul 26, 2000
Antwerp, Belgium
Okay, that's all nice, but my one and only question is: will a 100 watt all-tube (new) Ampeg V4B head combined with Ampeg 2x10 and 1x15 cabinets be powerful enough for most playing situations?

------------------
Bassic greetings, T-J.

10. ### throbbinnut

"The assumption that because you can run a tube past the point of distortion and achieve some magic increase in power is absolutely erroneous."

O.K. Chris, one paragraph at a time.
That's a true statement. There is no "magic" involved. It can be explained by fairly simple physics. Agreed?

&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;Agreed. I thought you were disputing the fact that a 100W amp can produce an output greater than 100 Watts. Now I see you were saying there is no magic involved.

The circuit you are describing stopped being an audio amp when you subbed the resistor for the speaker. A resistor of sufficent wattage rating will not self destruct. A speaker on the other hand will self destruct almost instantly under those test parameters. Kind of the apples and oranges thing again.

&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;A speaker that has a high enough power rating will not be destroyed JUST by the shape of the wave. It is still power level dependent. True, a 40 Vrms (40Vpeak) squarewave is a hell of a lot rougher on a speaker than a 28 Vrms (40Vpeak) sine wave. But a 1000 Watt rated 8 Ohm speaker could most likely handle the nastiness of a 200W squarewave. Really distorted guitar approaches a square wave, and speakers handle it.

The reason I specified a resistor is so my power calculation example would be correct. An 8 ohm speaker is only about 4 ohms resistance, the rest of the impedance is made up by inductance. All the power dissipated in the 4 ohms of wire resistance is turned into nothing but heat. The actual total electrical power from the amp to the speaker is harder to figure since a speaker is a reactive load, and power is equal to current times voltage times the cosine of the phase angle between the 2 waveforms. Nasty calculations, unless it only involves periodic waveforms.

Chris, we aren't arguing. We are having a discussion. It should be kept at a simple level as much as possible because all of us are not at the same technical level. Sorry, that was an opinion, not a fact.

&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;That's cool. I'll try and be more civil. I think about this stuff so much, I just assume everybody I talk to is an electron geek like myself. Actually, we pretty much agree, now that I understand you were dismissing magic, not science. I still think that a high rated speaker can survive a square wave, though.

Chris

11. ### pkr2

Apr 28, 2000
coastal N.C.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Tom-Jens:
Okay, that's all nice, but my one and only question is: will a 100 watt all-tube (new) Ampeg V4B head combined with Ampeg 2x10 and 1x15 cabinets be powerful enough for most playing situations?

<HR></BLOCKQUOTE>

Absolutely! As long as the rest of the band is not so loud that they drown you out.

Frog

12. ### winstonSupporting Member

May 2, 2000
Berkeley, CA
I'm certainly no expert when it comes to electronics but one convincing explanation for different amounts of usable power from amps with the same wattage rating is that
the manufacturers use different methods of measuring power. I've seen some specs published that claimed, say 500 watts of output, but with, perhaps, a 1khz test tone and 5% total harmonic distortion. Then another amp will claim maybe 300 watts, but with 1% thd and a full range music signal input. I don't think you can compare amp A and amp B's wattage unless the power was measured in the same manner, and when you start factoring in speaker efficiency and such, things can get really confusing!

13. ### pkr2

Apr 28, 2000
coastal N.C.
" But a 1000 Watt rated 8 Ohm speaker could most likely handle the nastiness of a 200W squarewave. "

I agree, in principle. However from a practical point of view it would be so power hungry as to almost be useless. If the speaker is rated at 1000 watts and it's presented with 25 watts input it probably would sound pretty anemic. It's not the fact that a square wave is bad because it's a square wave- it's because a square wave has almost a pure D.C. content. I'm almost certain that no manufacturer of speakers would claim that thier speaker will withstand even 25 volts of D.C. across the voice coil for any length of time. Even though it's rated at 1000 watts of audio.

"Nasty calculations, unless it only involves periodic waveforms."

Agreed. Another good reason to try to keep it as simple as we can.

&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;That's cool. I'll try and be more civil. I think about this stuff so much, I just assume everybody I talk to is an electron geek like myself. Actually, we pretty much agree, now that I understand you were dismissing magic, not science. I still think that a high rated speaker can survive a square wave, though."

Fair enough. Because I don't agree doesn't imply that your input isn't valued. I wish I'd had you to call on when I first started into electronics. You obviously have done your homework. My problem is that I can't present my thoughts as clearly as I wish that I could. My first love is music and my second love is electronics. I don't know as much about either as I wish I did.

Friends?

Frog

14. ### pkr2

Apr 28, 2000
coastal N.C.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by winston:
I'm certainly no expert when it comes to electronics but one convincing explanation for different amounts of usable power from amps with the same wattage rating is that
the manufacturers use different methods of measuring power. I've seen some specs published that claimed, say 500 watts of output, but with, perhaps, a 1khz test tone and 5% total harmonic distortion. Then another amp will claim maybe 300 watts, but with 1% thd and a full range music signal input. I don't think you can compare amp A and amp B's wattage unless the power was measured in the same manner, and when you start factoring in speaker efficiency and such, things can get really confusing!
<HR></BLOCKQUOTE>

Right on, Winston. Then you have peak , PtoP, music power and any other gobbledy gook that manufacturers can come up with and the "specs" become almost meaningless.

From my original post:"Manufacturers have been making specs say just exactly what the consumer wants to hear for years. I.E. P-P power and peak power."

Frog

15. ### merlin

Well i'm in a "who cares mood" today. Like who really cares about all the technical stuff?? If its not loud enough, its not good enough! I find amps with a higher wattage i try out in the store fully cranked. Then i would buy it and use it in gig situations. The manufacturers are making money via the sale, and i'm making money via the gig!

Thats my two cents and no one can argue

------------------
Del: ahh Woodstock, now that was a show.
Garth: wow, you were at woodstock?
Wayne:alright man, party on.What was it like?
Del: Well it rained all morning and cleared up in the afternoon. I nearly remembered something else then....."

[This message has been edited by merlin (edited July 27, 2000).]

16. ### dancehallclasher

Jul 21, 2000
San Ramon, CA
when i say "pkr2" real fast, it sounds like pikachu. you know, the mouse-type-creature in that pokemon show. is that intentional? i mean, you are talking a lot about electricity and that mouse has some sort of electric powers. i bet you're wondering right about now if i have anything worthwhile to add to this thread, and i don't, but i was thinking, "this thread needs a small break in the tedium of technical jargon" so here you go.

i am learning a lot, by the way, so i hope i don't sound unappreciative.

------------------
we hope you are ok.

17. ### pkr2

Apr 28, 2000
coastal N.C.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by merlin:
Well i'm in a "who cares mood" today. Like who really cares about all the technical stuff?? If its not loud enough, its not good enough! I find amps with a higher wattage i try out in the store fully cranked. Then i would buy it and use it in gig situations. The manufacturers are making money via the sale, and i'm making money via the gig!

Thats my two cents and no one can argue

<HR></BLOCKQUOTE>

Merlin: If you don't have enough intelligence to use the English language any better than you do, I can see that you may be having a problem keeping up. This is the AMP FORUM.
If you are tired of this topic DON"T READ ANY MORE OF IT. No one is forcing you to read anything.

You appear to have the social graces of a goat when you respond to a post in the manner you have chosen to use.

How much of your own money have you spent buying all of this equiptment just to keep the economy healthy? Daddy's money doesn't count.

I see from your profile that you are 17 years old. You are 4 years away from being an adult. You are 4 light years away from anything that resembles adult behavior.

You are a newbie. Apparently it needs to be pointed out to you that it's not your thread and it's not your decision as to when the thread has run its course.

You may find a more receptive audience for your "wit" in Off Topic. It's not welcome here.

Frog

18. ### Matthias

May 30, 2000
Vienna, Austria
Frog!
Was an answer like this really necessary?
I can see a good argumet in Merlin's post: What counts is the result - is the amp powerful enough for the intended use or not?
It's not bad to have a little background knowledge, especially being aware of different measuring methods, as Winston said, and some 'laws' of acoustic.
But hardly any bass player is an electronics expert.

And what I don't like at all is your statement regarding good English and intelligence: Not everyone here (including me) is speaking English as his first language. (Merlin is Australian, so I guess he does, but that's another thing).

Keep cool man,
Matthias

Theory is when you know everything, but nothing works.
Practice is when everything works, but you don't know why.
We are combining both: Nothing works and we don't know why...

19. ### ulf_kurt

Feb 10, 2000
Umea, Sweden
Yeah! I'm with mattias, no need to throw **** at someone (we're all in the same boat here)

Speaking of "loud". How much do each part "weight" in the volume-chain.
String-Pickup-cable-preamp-amp-speaker.
Could for example changing strings or pickups make a noticeable difference in the output-volume of an amp.

Sorry, if the questions are dumb (and my spelling stinks). i'm just trying to be a better bassplayer. &lt;

cheers

20. ### Matthias

May 30, 2000
Vienna, Austria
I see it like this: active or passive pickups and the distance between strings and pickups and maybe other factors do have an influence on the output of your BASS, but NOT on playing volume.
It's the task of the pre amp section to deliver an optimum line level for the power amp section (for low signal to noise ratio) with ANY input signal (within the usual range). If the input level is high (e.g. active bass), you have to set the input gain low and vice versa.
Another way to say it: You can't use a hotter input signal to achieve more volume, because the preamp is limited in his output (and the power amp in his input).

There is two things that have an influence on volume as far as I know:
speaker cable diameter and connectors (XLR and speakon provide more contact erea than the good old 1/4"-plugs, wich is important for high powered systems). But I'm not too sure about that, maybe it's only the quality wich is influenced by that.

Matthias

[This message has been edited by Matthias (edited July 28, 2000).]