Your Universal Remote Control Center
RemoteCentral.com
Custom Installers' Lounge Forum - View Post
Previous section Next section Previous page Next page Up level
Up level
The following page was printed from RemoteCentral.com:

Login:
Pass:
 
 

Page 2 of 4
Topic:
Do speakers draw watts from an amp or get fed watts ?
This thread has 47 replies. Displaying posts 16 through 30.
Post 16 made on Sunday February 4, 2018 at 23:48
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
On February 4, 2018 at 22:42, Dean Roddey said...
Anyway, probably no clearer than anyone else, but I can never resist the challenge to be less understood than my fellow man.

And, as proof, he's done it:
The speaker acts as the same sort of resistance to the amp trying to push electrons through it....you'd probably blow up the amp or trip a fuse in it, because there would be no resistance to the electron flow... That's also why amps have limits on how low the ohms (resistance) on the speakers can be.

In all of those cases Dean means amplifer, not Ampere.

On February 4, 2018 at 02:33, ErikU said...
I think the OP was asking a question about the correct use of terminology. I cringe when I hear electrical terms misused, so I suspect that was the point of the question..?

I cringe when I read sentences like that. You say that because you cringe when you hear electrical terms misused, you suspect the misuse of electrical terms was the point of the question.

Why, indeed how in the world, would your attitude about misuse of words influence the point of the question?

Amps are a measurement of current. (I)
Watts are a measurement of power. (P)
Volts are a measurement of potential, voltage, or electromotive force (E)
Ohms are a measurement of resistance (R)

So, speaking of using terms correctly, this list seems to be a list of similar things, but watts are in a totally different category from the other units.

The units discussed here are all instantaneous quantities except for power, which is energy expended over a period of time. Because of that, power isn't the same kind of unit. The correct term that you want is Watt-hours, a measurement of energy. But that's kinda complicated.

As for which word to use, current is measured in amps, power is measured in watts, EMF is measured in volts, resistance is measured in ohms... what determines that you should use one of those terms but not the other? Is "the current is five amps" somehow incorrect because it doesn't just use the term "current"?

A pet peeve of mine is hearing things like "how many amps is that", instead of "how much current does that draw". It sounds as awkward as asking someone "how many pounds are you" instead of asking "how much do you weigh".

"How many ohms is that resistor?" gets the question asked with fewer words. Beside that, the answer will be given in ohms, so it's not in any way incorrect to ask the question using the term ohms.
Unless you are referring to a specific measurement (ie. that circuit is rated for 5 amps, or I weigh 200 lbs), you should refer to what it is you are trying to measure.

When I measure the voltage, I want an answer in volts. So how do I refer to voltage (a general term with no assignable number) (that is, you wouldn't say "its voltage is 200") without naming volts?

You ARE talking about a pet peeve, though, and pet peeves often are based on tiny little judgments that aren't important to most of the rest of us.

I think to the original question I would say that speakers are a consumer of watts, just like a light bulb. Unlike a light bulb though, that consumption is not static.

Speakers and light bulbs don't consume watts. Speakers and light bulbs convert some small percentage of the supplied energy to two or three other forms of energy (or power; do you want to argue about that?). Speakers convert electrical energy to sound and heat energy. Light bulbs convert electrical energy to light, heat, and sometimes sound energy (ever had a buzzing bulb?).

And if we really want to go in deep, I wouldn't say that just current could start a fire. High potential can arc. Combine those two into high power and you really have something dangerous!

I was suggesting that a person of the knowledge level suggested by the question should not be bludgeoned with any information about how fires can be started without first clearing up the actual issues he's asking about.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 17 made on Monday February 5, 2018 at 06:21
Nick-ISI
Long Time Member
Joined:
Posts:
September 2004
444
I just love the way these types of threads (d)evolve.

The OP's original requirements soon get lost as the posts degenerate into a global pissing match as to who has used what terminology wrongly or not quite provided an explanation that delves into the minutiae of science.....

....hours of (worthless) entertainment.

Anyway can you desist long enough for me to go and buy some more Popcorn please....

:-)
What do you mean you wanted it on the other wall - couldn't you have mentioned this when we prewired?
Post 18 made on Monday February 5, 2018 at 09:42
highfigh
Loyal Member
Joined:
Posts:
September 2004
6,590
On February 4, 2018 at 23:48, Ernie Gilman said...
Speakers and light bulbs don't consume watts. Speakers and light bulbs convert some small percentage of the supplied energy to two or three other forms of energy (or power; do you want to argue about that?).

You could use Si base units of kg⋅m2⋅s−3
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 19 made on Monday February 5, 2018 at 13:33
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
Nick, you got your popcorn yet?

Highfigh, you're totally correct.

I think we've probably beat this topic to death, going way beyond what was asked.

If this was just about terminology, I'd expect the original post to include a question like "Which way do you describe it?" or "Are these the right terms for talking about this?"

Plus, we all try to comment as clearly as we can, but we end up leaving out details or making misstatements where the exactly correct expression would take a paragraph or more to be totally correct. For instance, here's one from the second post:

On February 3, 2018 at 14:27, buzz said...
Neither.

Current causes heating and heating can cause fires.

Heating is caused by a combination of voltage, current, and resistance. That's why the ohm's law formulas for power have all three variables in them.

I believe the rest of this comment is an entire chapter in a textbook.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 20 made on Monday February 5, 2018 at 19:03
highfigh
Loyal Member
Joined:
Posts:
September 2004
6,590
On February 5, 2018 at 13:33, Ernie Gilman said...
I think we've probably beat this topic to death, going way beyond what was asked.

First, it's 'beaten' and second, I, for one, won't be satisfied until this topic has been ground into a fine paste. :D
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 21 made on Monday February 5, 2018 at 19:56
crosen
Advanced Member
Joined:
Posts:
April 2009
996
On February 3, 2018 at 13:09, james_aa said...
Do speakers draw watts from an amp or get fed watts ?

Eg. would a 60w speaker connected to a 100w amp draw 60w or get fed 100w ?

A bit oversimplified, but speakers get fed watts.

A 100watt amp could feed up to 100watts to an (8 ohm) speaker, even if that speaker was speced at 60watts.

That 60watt speaker is only built to handle being fed 60watts, so feeding it 100watts could blow it out.
If it's not simple, it's not sufficiently advanced.
Post 22 made on Monday February 5, 2018 at 20:06
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
crosen, your signature says your answer is not sufficiently advanced:

If it's not simple, it's not sufficiently advanced.

But, of course, your answer is totally correct.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 23 made on Tuesday February 6, 2018 at 10:46
drewski300
Super Member
Joined:
Posts:
January 2007
3,716
On February 3, 2018 at 16:55, buzz said...
Pot accuses kettle ...

And his post was equally as long! LOL
"Just when I thought you couldn't possibly be any dumber, you go and do something like this... and totally redeem yourself!"
Post 24 made on Tuesday February 6, 2018 at 11:45
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
On February 3, 2018 at 16:13, Ernie Gilman said...
buzz, I'm hardly the guy to say this, but this could have been answered more simply.

This is pot accusing kettle while commenting that he's doing so. You missed that, I guess. Keep your eyes open for the self-deprecating humor.

On February 6, 2018 at 10:46, drewski300 said...
And his post was equally as long! LOL

It actually was a teeny tiny bit shorter, which is why I wrote:

That didn't turn out to be much shorter, did it?
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 25 made on Tuesday February 6, 2018 at 12:07
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
I saw something new when I looked at this again:

Do speakers draw watts from an amp or get fed watts ?

I see why it's tempting to conceive of speakers as drawing power from an amplifier, but here's a parallel situation: if a pipe connects a lake of one elevation to a lake of a lower elevation, does the lower lake draw water, or does the upper lake feed water? It's definitely the latter.

The difference in elevation provides a force to move the water to the lower lake: the force of gravity. With amplifiers and speakers, the voltage at the amplifier output provides the force to move energy into the speakers.

The diameter of the pipe and the difference in elevation of the lake determine how much water will flow. The impedance of the speaker and the voltage of the amp determine how much energy will flow into the speaker.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 26 made on Tuesday February 6, 2018 at 15:21
highfigh
Loyal Member
Joined:
Posts:
September 2004
6,590
On February 6, 2018 at 12:07, Ernie Gilman said...
I saw something new when I looked at this again:

I see why it's tempting to conceive of speakers as drawing power from an amplifier, but here's a parallel situation: if a pipe connects a lake of one elevation to a lake of a lower elevation, does the lower lake draw water, or does the upper lake feed water? It's definitely the latter.

The difference in elevation provides a force to move the water to the lower lake: the force of gravity. With amplifiers and speakers, the voltage at the amplifier output provides the force to move energy into the speakers.

The diameter of the pipe and the difference in elevation of the lake determine how much water will flow. The impedance of the speaker and the voltage of the amp determine how much energy will flow into the speaker.

Which causes water to flow depends on the original water level at the lower body of water. If it was below the low end of the pipe, it couldn't have drawn the water to it and even then, if the upper lake was already spilling into the pipe, the lower one won't affect flow until its level creates enough back pressure that the flow from above is resisted.

Speakers are presented with voltage. What happens after this is up to the speaker's resistance/impedance. If the impedance is extremely high, not much current will flow but the power is still only determined through calculation and it's neither constant, nor is it due to anything more than the fact that a connection between the amp and speaker has been made.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 27 made on Saturday February 10, 2018 at 03:24
g007
Regular Member
Joined:
Posts:
October 2015
78
james_aa

This is very interesting question. It seems simple to answer, on the surface, but when you get into it, not so simple. In fact it can get quite complex. I will throw out some tidbits and let you guys run with it.

1. Think of the amplifier as the utility company and the speaker as the only load they have.

2. The speaker is an electromechanical device, a transducer. It converts electrical power (or energy if integrated over time) into mechanical motion which results in a pressure wave, which we perceive as sound.

3. The load is an AC Load, so it has AC Resistance (will hit on this later), Inductance and Capacitance. because of its reactive components, it has the ability to STORE energy and RELEASE (back EMF of the speaker) energy.

4. DC Resistance implicitly indicates 0Hz operation!

5. When you talk about any AC Load you MUST specify the frequency. Once you know the frequency the reactive terms have meaning. You can calculate the magnitude of each one and then vector sum them together to get the net reactive impedance, either inductive or capacitive. You then vector sum the AC Resistance with the resulting reactive component to realize the impedance vector Z at the frequency of interest. You then can compute the Phase angle and determine the true power and apparent power.

6. AC Resistance takes into account the Skin Effect present in all non-zero frequency wire situations. It is a calculation that is always done by power transmission engineers AND especially RF engineers and/or anyone who is subject to its effects. The best analogy I can come up with to describe this Skin Effect is the water pipe analogy.
At DC the full cross sectional area is usable. As the frequency goes from zero to non-zero another solid pipe, small in diameter at first, is inserted into the larger hollow pipe diameter. This forces the flow to the remaining open area, thus causing an increase in resistance. As the frequency increases, the solid pipe get larger and larger and forces the flow closer to the surface of the wire. The cross sectional area gets smaller and smaller until very little of the original cross sectional area is available. As an example at 50Hz 100 ft of 16 gauge wire has .39085 Ohms of AC Resistance. At 60 Hz its .39086 Ohms, at 600Hz its .39108, at 6000Hz its .39328, at 20kHz its .42022 Ohms. Anyway you get the picture. The inductance, the number of wires and their spacing will also come into play. The formula can get quite complex. Knock your socks of if you want to delve into this area.
Post 28 made on Saturday February 10, 2018 at 18:05
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
On February 6, 2018 at 15:21, highfigh said...
Speakers are presented with voltage. What happens after this is up to the speaker's resistance/impedance. If the impedance is extremely high, not much current will flow but the power is still only determined through calculation and it's neither constant, nor is it due to anything more than the fact that a connection between the amp and speaker has been made.

It makes little sense to ignore all the things that need to be in place so that when one connects the amp to the speaker, power flows. You're describing the action of a system. Saying "not due to anything more" ignores all sorts of assumptions about what is in front of you, including but not limited to whether there's a line level signal of the proper voltage, and even whether the damn power amp is plugged in!

Everything I said above may be seen as trivial, but it's true: without ALL things in place, no power will flow.

Also, "the power is still only determined through calculation" if you mean knowing the quantity of watts so you can write it down. That is a bit of a philosophical statement, the idea being not to confuse the actual power with the number we give to it. (A parallel example is thinking that the number "3" IS three. It's only a symbol that represents three, just as a measured power level represents the power, but is not the power.)

The actual determiners of actual power in any given situation are... you've heard it already: the speakers connected to the power amp, the line voltage level (whether 120V power or audio), volume control setting, load impedance, etc. Those things are far more determinative of power than a calculation. A calculation only describes what already is.

On February 10, 2018 at 03:24, g007 said...
james_aa

This is very interesting question. It seems simple to answer, on the surface, but when you get into it, not so simple. In fact it can get quite complex. I will throw out some tidbits and let you guys run with it.

That's fair. We've already gone a few miles as it is.

3. The load is an AC Load, so it has AC Resistance (will hit on this later), Inductance and Capacitance. because of its reactive components, it has the ability to STORE energy and RELEASE (back EMF of the speaker) energy.

Isn't AC resistance the combination of resistance, and reactive components?

4. DC Resistance implicitly indicates 0Hz operation!

I love the blank look thrown my way when I tell someone, quite on purpose, that DC is 0 Hz. Or that for transistors to work, they must first encounter the first half of a very long 0 Hz-ish waveform, that is, the application of battery power.

5. When you talk about any AC Load you MUST specify the frequency. Once you know the frequency the reactive terms have meaning. You can calculate the magnitude of each one and then vector sum them together to get the net reactive impedance, either inductive or capacitive. You then vector sum the AC Resistance with the resulting reactive component to realize the impedance vector Z at the frequency of interest. You then can compute the Phase angle and determine the true power and apparent power.

These paragraphs are in the wrong order. It's not appropriate to bring in a new term, AC resistance, without definition, especially since it has next to nothing to do with audible signals. You should defined it first, so we could know we could ignore the difference between AC resistance and DC resistance.
6. AC Resistance takes into account the Skin Effect present in all non-zero frequency wire situations. It is a calculation that is always done by power transmission engineers AND especially RF engineers and/or anyone who is subject to its effects. The best analogy I can come up with to describe this Skin Effect is the water pipe analogy.

The rest of this was just mental play since skin effect is negligible at the frequencies we've been talking about, that is, audible-by-humans audio.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 29 made on Saturday February 10, 2018 at 18:22
buzz
Super Member
Joined:
Posts:
May 2003
2,801
On February 10, 2018 at 18:05, Ernie Gilman said...
Isn't AC resistance the combination of resistance, and reactive components?

I'd rather call it the Magnitude of the impedance because this keeps the frequency dependent nature of the quantity in focus.
Post 30 made on Sunday February 11, 2018 at 00:10
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
28,468
buzz, he did not mean impedance. He meant AC resistance! When I was writing earlier I found a clear description of AC resistance but google is resisting (or impeding) my search for that description. It's at [Link: en.wikipedia.org].

So buzz misunderstood what was meant by AC resistance, as I did. That's because it looked like a mistaken term, it's arcane, is unrelated to audio, and was introduced without giving the definition at first. The following is from a wikipedia article on skin effect. I've highlighted the parts that relate to this discussion.

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor. The skin effect is due to opposing eddy currents induced by the changing magnetic field resulting from the alternating current. At 60 Hz in copper, the skin depth is about 8.5 mm. At high frequencies the skin depth becomes much smaller. Increased AC resistance due to the skin effect can be mitigated by using specially woven litz wire. Because the interior of a large conductor carries so little of the current, tubular conductors such as pipe can be used to save weight and cost.

And

The ratio AC resistance to DC resistance of a round wire versus the ratio of the wire’s radius to the skin depth.

The second quote is from the legend of a graph.

NONE OF THIS DISCUSSION MENTIONS INDUCTANCE AT ALL. g007 decided to make reference to a term that I've never seen in any discussion of resistance or impedance, ever. That doesn't mean it doesn't exist. That means it's outside the sphere of what we're dealing with and talking about.

I think the most important fact to notice from this is that the "skin" at 60 Hz is 8.5 mm, which is about a third of an inch. That is, any conductors less than a third of an inch in diameter WILL NOT SHOW ANY SKIN EFFECT. (Zero gauge wire is just slightly smaller than a third of an inch.)

This is why I say the entire issue of skin effect and the g007's use of the term AC Resistance has no place here. It makes absolutely no difference to anything we're talking about.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Find in this thread:
Page 2 of 4


Jump to


Protected Feature Before you can reply to a message...
You must first register for a Remote Central user account - it's fast and free! Or, if you already have an account, please login now.

Please read the following: Unsolicited commercial advertisements are absolutely not permitted on this forum. Other private buy & sell messages should be posted to our Marketplace. For information on how to advertise your service or product click here. Remote Central reserves the right to remove or modify any post that is deemed inappropriate.

Hosting Services by ipHouse