Speaker power/output

Bruce Griffin · From: Iowa City, Iowa

Just curious; if you apply 15 watts to a speaker(Tone Tubby or something of that nature)rated at 15 watts, and say 80 watts to a speaker rated at 80 watts, will the sound output be roughly the same? I don't want to start a multpage topic, and I'm not technical, just wondered. Thanks!

C Dixon · From: Duluth, GA USA

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Speakers aren't real efficient to begin with, and their power rating has nothing to do with their efficiency, which is thier output with a given input. That said, most speakers will be doing good if their efficiency is 15%. So, assuming both speakers are 15% efficient, the one receiving 15 watts of electrical power would produce 2.25 watts of audio, and the one receiving 80 watts electrical would produce 12 watts of audio.

The 80 watts would sound a little over twice as loud as the 15 watts, but not five times as loud, as the figures might lead you to believe.

Tony Palmer · From: St Augustine,FL

I believe the key word here is decibels, which is related to the intensity of sound by a factor of ten.
So, all other things being equal, you would need an amp to be 100 watts to sound twice as loud as a 10 watt amp.

John Daugherty · From: Rolla, Missouri, USA

Tony has a good point. I have a hard time making people believe that doubling the power is a waste of time and money. It is hardly,if at all, noticeable.
An increase in power is helpful in the fact that more headroom results in less distortion at the lower sound levels.
To make a long story short; My first good amp was a ~1960 Fender Bassman (~50 watts). I now use A Peavey Nashville 400 (~200 watts). NOT MUCH NOTICEABLE DIFFERENCE in the SOUND LEVEL (in my opinion).

Mike Brown · From: Meridian, Mississippi USA

+3dB=2 x power=Noticable difference
+6dB=4 x power=Moderate difference
+10dB=10 x power=Twice the difference in loudness.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Decibels, acoustic perception, logarithmic scales, audio vs. electrical watts, yada, yada yada.

Yes, I've heard the same thing time and time again. I also realize there's probably scientific theory and proof (somewhere?) that it takes 10 times the power to make something "sound" twice as loud.

Pardon me, but I just never accepted it.

Science or no science, it does not compute in my feeble brain. I deal mainly in "real world" experiences amassed from well over 40 years of playing music. To me, it simply doesn't take 10 times the power for something to sound twice as loud, and I believe anyone who's heard a 10-watt amp on stage beside a 50-watter would agree. (The 50-watter is easily twice as loud.)

I can also appreciate John Daughterty's dilemma that his 50-watt Fender Bassman is almost as loud as his 200-watt Peavey Nashville, but...that can be explained. The bass-reflex cabinet of his Bassman is probably 3 times as efficient as the open-backed Nashville cabinet. So, in actual audio output, despite the 150-watt disparity, there's probably only about 10 (audio) watts difference between the two.

Dan Tyack · From: Olympia, WA USA

Then there is the transistor versus tube issue. Tube amps sound really musical through their rated power output (less if you need a clean sound). Transistor amps sound like crap when they get anywhere near their rated power output.

In terms of John's Bassman that was nearly as loud as a Nashville, I am assuming that this was a 4X10" open back amp, since it was 1960, so the speaker efficiency isn't an issue. My completely unscientific rule of thumb is that it takes two times the transistor wattage to equal tube watts. So it makes sense that the Nashville is only marginally louder.

Ray Minich · From: Bradford, Pa. Frozen Tundra

The factors that determine the subjective loudness of a sound are complex, and much research is being done (still) on the subject. One such factor is that the human ear is not equally sensitive to all frequencies, but is most sensitive in the 2 kHz thru 5 kHz range. and least sensitive at the high and low ends of the audio spectrum. This phenomenon is more pronounced at low SPL's (sound pressure levels) than at high SPL's. To give the same apparent loudness as a 1000 Hz tone at 70 dB, a 50 Hz tone must be at an SPL of 85 dB.
(From "Measuring Sound" by B&K Instruments)

In an industrial environment you gotta wear ear protection where the background noise level stays above 85 dB.

FWIW, a mosquito generates a sound level of 14 femtowatts (that's 0.000 000 014 watts I believe...).

100 dB of 40 Hz tone will rock you around but it don't hurt that much. 100 dB of 4500 Hz tone will make your eye teeth pop out.

Oh, and I gotta add this bit of wisdom from the B&K book...
Another useful aspect of the dB scale is that is gives a better approximation to the human perception of relative loudness than the pascal (absolute pressure) scale since the ear reacts to the percentage change in level, which corresponds to the decibel scale where 1 dB is the same relative change everywhere on the scale. 1 dB is the smallest change we can hear. A 6 dB increase is the doubling of the Sound Pressure level, although a 10 dB increase is required to make it sound twice as loud.

So, louder is better, but is it twice as loud? only the SPL meter knows for sure, and even it gets confused...

[This message was edited by Ray Minich on 25 May 2004 at 03:55 PM.]

[This message was edited by Ray Minich on 25 May 2004 at 04:00 PM.]

[This message was edited by Ray Minich on 25 May 2004 at 04:09 PM.]

[This message was edited by Ray Minich on 25 May 2004 at 04:13 PM.]

C Dixon · From: Duluth, GA USA

With much sincere respect Donny (I agree with you 99% of the time), I must tell you dear friend that the statement it takes 10 times the power change for a human to sense twice the power change is not just a statement off the top of one's head.

Believe me much scientific and carefully controlled triple blind tests prove it time and time and time again. The reason for this is, the human ear was as the poster said, able to hear astronomically low levels as well as incredibly high levels. NO device ever made by man has the dynamic receptive capability of the human ear.

But this unprecedented range means the ear must be also incredibly non linear. It is this non linearity of the way humans perceive sound that gives truth to the 10 times scenario.

Unless you have a true verifiable given wattage amp versus another verifiable given wattage amp could you even begin to test the validity of this. Many amps have speaker efficiences far and away superior or inferior to other speakers in the same wattaged amps, etc. In addition, manufacturers have from day one played tricks with Power ratings.

But take it to the bank that the ten times statement is indeed true. It is taught in audio 101, also any audiologist will attest to it; and ear specialists geared toward perceived sound in humans will all agree to it.

Luv ya man,

carl

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Carl, I understand and appreciate the sheer magnitude of our hearing capabilities. It's just my nature to question and doubt things that go against my own experience. I'm sure that scientists, engineers, and audiologists alike have no trouble accepting the "X10 to double" rule. Some can probably even prove it scientifically. However, until I witness it personally, I'm not going to accept the premise.

Here's one example of my "questioning mind"...

When I was in college many decades ago, our astronomy professor pointed out that the speed of light is both an ultimate and a "constant". It zips along, unchanging, at almost 6 trillion mph, just over 186,000 miles per second. When I noticed that our textbook said light speed was 186,786 miles per second in a vacuum, my own feeble mind made me ask the dumb question "If the speed is constant, why does it make a difference if it's in a vacuum?" Well, he apparently wasn't educated enough to tell me that the speed of light does change! That change is both measurable and significant. The term "constant" doesn't refer to the speed at all, rather it refers to measurement from different observation points.

Likewise, some scientists are now doubting other scientists and postulating that faster-than-light travel may indeed be possible, though light-speed has been thought for decades (even by Einstein) to be the "ultimate velocity". (Interestingly enough, there's no way to scientifically prove either theory.)

I have great respect for scientists, but I temper that respect with my own stubborn inquisitiveness and experiences. After all, it was scientists who once proclaimed that the speed of sound was an "impenetrable barrier", and man could never exceed it and live to tell about it.

I probably wouldn't have listened back then, either.

[This message was edited by Donny Hinson on 25 May 2004 at 07:08 PM.]

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