a decibel question

[bongomania]

Yes but a watt is actually heat measured as a unit of power.

Heat is one type of energy. Not all power comes from, exists as, or transmutes into "heat", although certainly a lot of power lost from a circuit is lost in the form of heat, but that's not because there are little "heat-units" circulating through the wires.

 

[deBont Amps]

No, 10dB extra means twice the volume, so ten times the power is twice the volume.

Alex

NO, 3 dB extra is twice the volume or soundpressure. The human hearing works according to a logarithmic scale, describe in the 'Weber–Fechner law'.

Get this, three db is nothing, simple and fact.
For instance there is really no reason to pay $300 extra for an amp putting out 500 w compared to one putting out 250w. Power wise.

BS

Yes but a watt is actually heat measured as a unit of power...

Now that's just plain silly!
Watt (or power) is a calculated number from the amount of current at a certain voltage (P=UxI). Current is calculated by voltage and the resistance of e.g. a cable or speaker (I=U/R). So lets say the power going through your speaker is the voltage (square) at a given time, divided through the resistence of the speaker (P=(UxU)/R).

 

[ggunn]

NO, 3 dB extra is twice the volume or soundpressure. The human hearing works according to a logarithmic scale, describe in the 'Weber–Fechner law'.
.

Twice the SPL does not equal twice the volume. As you say, the ear's response to SPL is logarithmic. 3dB is twice the SPL, but 10 dB is twice the volume.

 

[Lelander]

http://www.phys.unsw.edu.au/jw/dB.html

"Experimentally it was found that a 10 dB increase in sound level corresponds approximately to a perceived doubling of loudness."

So no, doubling the power, which increases SPL by 3dB, doesn't make it sound twice as loud.

To know how loud a combo is going to get based solely on the size of the driver and the wattage of the amplifier is, essentially, impossible. You can make an estimate based on the reported sensitivity of the cabinet and the wattage as has been outlined earlier in the thread. This will be a rough estimate because that sensitivity is not reported in a standardized or necessarily meaningful fashion.

 

[seamonkey]

Maybe in the middle of human hearing 10db is perceived doubling of loudness, but not everywhere. It depends on what part of the scale you're on.
If you have a hair dryer running at 80db, and you turn on another one, you'll have 83db. Turn on another two and you'll have 86db, turn on another 4 (eight in all) and you'll have 89db. But at what point is it twice as loud as the just one?
Try the same with a buzzing fly(s).
Then again with a jet airliner(s).
Or just the slider on your mixer if it's calibrated in db. For me at least, at low levels just a couple of DB's is twice as loud, at high levels it's a much different story.

 

[Lelander]

Maybe in the middle of human hearing 10db is perceived doubling of loudness, but not everywhere. It depends on what part of the scale you're on.
If you have a hair dryer running at 80db, and you turn on another one, you'll have 83db. Turn on another two and you'll have 86db, turn on another 4 (eight in all) and you'll have 89db. But at what point is it twice as loud as the just one?
Try the same with a buzzing fly(s).
Then again with a jet airliner(s).
Or just the slider on your mixer if it's calibrated in db. For me at least, at low levels just a couple of DB's is twice as loud, at high levels it's a much different story.

That is absolutely true, and it's there for you to read about in the UNSW article. With most rock amplification, you are attaining some pretty enormous SPLs at even moderate wattage. Build an efficient cabinet (most bass combos are not nearly optimized for the driver being used) and you can achieve > 100dB @ 1m. The unspoken, often overlooked secret of audio amplification is that building a better cabinet can do more for you in many cases than buying a bigger amp. I think that Bill Fitzmaurice weighed in on this thread earlier. He is one of the modern masters of designing a cabinet that does amazing things with fairly reasonable wattage. I suspect a BFD Omni10 being driven by 100 watts would be many, many times louder than my little Hartke Kickback 15 under exactly the same power.

 

[seamonkey]

That is absolutely true, and it's there for you to read about in the UNSW article. With most rock amplification, you are attaining some pretty enormous SPLs at even moderate wattage. Build an efficient cabinet (most bass combos are not nearly optimized for the driver being used) and you can achieve > 100dB @ 1m. The unspoken, often overlooked secret of audio amplification is that building a better cabinet can do more for you in many cases than buying a bigger amp. I think that Bill Fitzmaurice weighed in on this thread earlier. He is one of the modern masters of designing a cabinet that does amazing things with fairly reasonable wattage. I suspect a BFD Omni10 being driven by 100 watts would be many, many times louder than my little Hartke Kickback 15 under exactly the same power.

Agreed.

There are tradeoffs, More efficient for bass usually means bigger. And efficient class-d - pulse width amps can put out more power than traditional amps with the same line current draw. So you can drive less efficient speakers to higher levels with essentially the same line requirements.
There's also the audio illusions that can be played to reduce the size of the cabinet yet still sound loud and low - missing fundamental approaches like MaxxBass or Crysonic newB seem to work the best. Things showing up in new mp3 player speakers. It's actually a form or distortion, but it works.

 

[spector29]

I believe it's called the Fletcher Munson or something like that curve/graph.
That'll show you the db differences to hear certain frequencies.
The human speech is between around 1000hz to 4000hz usually thats why we don't need much volume there.....Were use to it.

And sorry if I'm wrong about Watts being heat, but I was taught that watts is heat (heat being friction) represented through a power rating.
Maybe I've forgotten it all, but I was definitely taught that watts is a form of heat energy, to cut out all technical jargon. But I am no electrician and it wasn't an electrician course.
I don't know if it's a good example but would a radiator heater rated at 2800w be a good example??
Or how your amplifier does heat up so much because of all the electrical friction??
Maybe I've gone crazy with the watts but I stand by my other points.

But definitely check out the fletcher curve.

 

[bongomania]

Lol, I think the heat thing is one of those things where you heard the teacher say one thing but what they really meant was something a bit different, and it got stuck in your head the wrong way many years ago. It's happened to all of us I'm sure. I still get confused by "hypotenuse" and "avogadro" because of a teacher who had us memorize the words without adequate understanding of what they meant.

Heat is a form of energy, and power is one of the ways we quantify the transfer of energy, and watts are the units of power. A radiator uses (for example) 2800 watts of power to generate heat. It doesn't have 2800 watts of heat in it, it just has the ability to take 2800 watts of power (meaning a transfer of energy) and convert it from electricity into heat.

 

[spector29]

I know it doesn't have 2800 w in it but I still must be confused, I'm gonna go back and slap that lecturer.
I think maybe I'm thinking something like energy gets transfered into the circuit and creates a certain output which is usually caused by friction resulting in heat which is measured as watts.
I don't have my notebook anymore. I'm gonna have to get a 2x4 and beat in some sense.

 

[spector29]

Just a quick point or question,
if 1 volt of potential difference is applied to a resistive load, and a current of 1 ampere flows, then 1 watt of power is dissipated.
But isn't something it that dissipating typically occurs when an energy source is converted to heat??

And just by some reading:
For example:
A nuclear power plant has a fission reactor that generates 2108 MWt(mega watts thermal), which creates steam to drive a turbine that generates 648MWe (mega watt electrical).
The difference is heat lost to it's surroundings.
Now I may be wrong but that sounds to me like watts are both thermal energy yet when electrically focused it has less as further certain amount of watts is dissipated from the electrical circuit.
Or am I understanding wrong.
I learn't most of this from wikipedia under watt.

 

[bongomania]

Electricity is not heat, but it can be turned into heat. Watts are used to measure electrical power, not heat. You're seeing so many instances where heat is part of the discussion because the physical limitations of the electro-mechanical systems we have today all lose a certain amount of energy in the form of heat. But again, the energy was not heat in the first place. It becomes heat as a side effect of the physical limitations of the wires, circuit components, and other mechanisms that are used to transfer energy. Friction is an example of a mechanical process where heat may be generated while power is dissipated, but watts are not used to measure friction or heat generation from friction.