Underpowered receiver

[PENG]

What I'm saying is this. It is the power actually delivered to the load that will blow it. In other words blow a speaker.

Agree, since post#1.

Now in a speaker we both know that you can't calculate the current from power/V. At times the current will be higher depending on the phase angle.

Agree also, since post#1.

Now that excess current is going to the load, but also back to the source and the power given back over time.

That's a problem with some google contributors. Ask youself exactly what is meant by "power given back over time", I mean like you can use it to power your light bulb? The fact is, regardless of the power factor, i.e. phase angle that like you said we both know what it is, 10 ampere is 10 ampere. If that 10 ampere flows through a resistor it produces heat. If it flows through an inductive or capacitive load it does not produce heat except for that little bit of inherent resistance of the inductor and the capacitor, just a small amout.

Now that peak current has to be allowed for in the source and the supply lines. However only the power converted into heat and sound will be supplied by the source over time.

Agree, since post #1.

In practice what this means for the OP if his speaker is pretty typical, is that you would think his amp could provide 25 watts into his four ohm speakers over time, and only blow the fuse if this was exceeded. However if his speakers are typical, you could actually only deliver about 17 watts to them over time without blowing the fuse.

You seem (just seem) to be contradicting what you said earlier about the "....given back over time......" as though part of the amperage have no effect on the power delivered to the load. In fact that whole 2.5A counts, the 2.5A flows to the speaker but only develop heat according to 2.5AX2.5AX the resistance of the voice coil. No heat is produced by this 2.5A through the reactive part of the impedance of the speaker. So it is the reactive part of the impedance that has no effect on the heat produced. If you are saying the same thing then again there is no disagreement since post#1.

We got into this discussion, because I was trying to point out that a speaker line fuse will blow at a lower power level than calculated from the usual DC formulas, we ran for the OP earlier in the thread

It seems that we got into this discussion for that long because we are not sure what exactly what we agree and disagree on, hopefully, until now. I do have major problem with this true power thing. In the electric motor example I used, a 5 kW motor would have very low winding resistance. That 5 kW is not due to the power produced in its winding resistance but due to the load coupled to its output shaft. My understanding is that a speaker is a bit like a motor in some way, it is not really technically an active load as such but it does have a complex impedance and can produce back emf like a motor does. It does have much lower efficiency that a typical electrical motor, but what the heck is the "true power" of a speaker? I did ask you to clarify it so I do not have to guess but may be you did not see that part of my question. Please do not tell me what true power is in a RLC circuit though because we both know what that means.

 

[PENG]

I'm not confusing anything and regard the source resistances as part of the supply chain resistance which it is.

Well that's great, sorry.

I'm defining true power as the power consumed by the load and converted into heat, sound, mechanical energy or what ever.

Now that you have defined it I know what you are saying. No disagreement I wish you did it earlier. Thanks!

An amplifier really does have to provide significantly more current into a speaker than a four ohm resistor and if it can't it clips.

We both know an amplifier have to provide more current into a low impedance load so you won't expect me to say anthying else right?

I have not examined the receivers talked about extensively in these forums. However I suspect most of them can provide no more current into an 4 ohm load than a 8 ohm one, even if they don't blow up. My best guess is that these receivers actually deliver less than 50 % of their rated power into most speakers. Most speakers are four ohm loads and even less in the frequency range were most of the power is drawn form the amp. So because of their inability to provide adequate current, voltage will be limited. So I think if these receivers were looked at critically you would find many of the receivers rated at 100 watts into 8 ohms probably actually clip at about 35 watts into most speakers.

I would guess the same if you are talking about entry level $500 or below kind of receivers. I would disagree if you are talking about receiver such as a Marantz 8000 series, Denon 4000 series and Onky 87X series, and up. I know they are much more capable than what you are saying here.

I can tell you for certain that was so before the advent of high current solid state output devices. I studied amps of the early generations extensively and that is exactly how they performed. Since manufacturers of most receivers just state they are four ohm stable (ie don't blow up) but don't specify the power they do deliver into a four ohm load I have a strong hunch that the clip point is at a much lower power point than is generally imagined.
For the above reasons I don't discount your assertion that the OPs amps may clip and that he could need more power. However I doubt they are clipping at the point his 2.5 amp fuses are limiting his current and power.

I glad you at least would not discount that possibility.

 

[TLS Guy]

Well that's great, sorry.



Now that you have defined it I know what you are saying. No disagreement I wish you did it earlier. Thanks!



We both know an amplifier have to provide more current into a low impedance load so you won't expect me to say anthying else right?



I would guess the same if you are talking about entry level $500 or below kind of receivers. I would disagree if you are talking about receiver such as a Marantz 8000 series, Denon 4000 series and Onky 87X series, and up. I know they are much more capable than what you are saying here.



I glad you at least would not discount that possibility.

As far as I know the terms true power, apparent power and reactive power, is standard defined nomenclature. So I would not have expected to define it initially. I was familiar with these terms on high school. While recently moving the controls for my generator, my electricians apprentice who is still in school asked me about this issue, as he is struggling with it in his course work.

As I understand it this is how it is defined.



apparent power


DEFINITION -

Apparent power is a measure of alternating current (AC) power that is computed by multiplying the root-mean-square (rms) current by the root-mean-square voltage. In a direct current (DC) circuit, or in an AC circuit whose impedance is a pure resistance, the voltage and current are in phase, and the following formula holds:

P = ErmsIrms

where P is the power in watts, Erms is the root-mean-square (rms) voltage in volts, and Irms is the rms current in amperes. But in an AC circuit whose impedance consists of reactance as well as resistance, the voltage and current are not in phase. This complicates the determination of power.

In an AC circuit, the product of the rms voltage and the rms current is called apparent power. When the impedance is a pure resistance, the apparent power is the same as the true power. But when reactance exists, the apparent power is greater than the true power. The vector difference between the apparent and true power is called reactive power.

If Pa represents the apparent power in a complex AC circuit, Pt represents the true power, and Pr represents the reactive power, then the following equation holds:

Pa2 = Pt2 + Pr2

So I have tried to put it in terms the OP might understand which is what I have been saying all along. True power is the actual power supplied by the source in watts. The apparent power is a derived number, but this power is not expended, however the current required to calculate this number is delivered from source to load. The load will expend the true power minus any losses due to resistance in the power chain.

The fuse in the line will blow according to the calculations for the apparent power. The load (speaker voice coil burn out) will depend on the true (actual power) delivered from the source minus line losses. So when I originally stated the blowing of the OPs fuse will track the current from the the apparent power and whether the voice coil burns or not will relate to true power, I was correct. I maintain I have been consistent about that through out, and that that is the correct analysis of the situation presented.

 

[PENG]

As far as I know the terms true power, apparent power and reactive power, is standard defined nomenclature. So I would not have expected to define it initially. I was familiar with these terms on high school. While recently moving the controls for my generator, my electricians apprentice who is still in school asked me about this issue, as he is struggling with it in his course work.

As I understand it this is how it is defined.



apparent power


DEFINITION -

Apparent power is a measure of alternating current (AC) power that is computed by multiplying the root-mean-square (rms) current by the root-mean-square voltage. In a direct current (DC) circuit, or in an AC circuit whose impedance is a pure resistance, the voltage and current are in phase, and the following formula holds:

P = ErmsIrms

where P is the power in watts, Erms is the root-mean-square (rms) voltage in volts, and Irms is the rms current in amperes. But in an AC circuit whose impedance consists of reactance as well as resistance, the voltage and current are not in phase. This complicates the determination of power.

In an AC circuit, the product of the rms voltage and the rms current is called apparent power. When the impedance is a pure resistance, the apparent power is the same as the true power. But when reactance exists, the apparent power is greater than the true power. The vector difference between the apparent and true power is called reactive power.

If Pa represents the apparent power in a complex AC circuit, Pt represents the true power, and Pr represents the reactive power, then the following equation holds:

Pa2 = Pt2 + Pr2

Let me borrow what 3 db said to you in post#26:

"I have a degree in Electrical and am well versed in this. " and please stop trying to explain those things that I myself have posted many times on this forum!!

I really cannot understand why you still fail to understand I was asking you to define "true power" for loads such as loudspeakers and electric motors. When you finally took the time to define it you did say what I was waiting for you to say:

"I'm defining true power as the power consumed by the load and converted into heat, sound, mechanical energy or what ever." instead of the simplistic I²R for a RLC (resistance, inductance, capacitance) circuit. And, the key words "converted into sound, mechanical energy....."

I sure hope others can see the confusion you have created by saying it is the true power consumed by the load (in your previous posts) that blow a speaker. Yes, as EE I am saying true power in the case of speakers, motors and loads of similar complex nature do take on meanings other than just the power converted into heat as you stated in your own definition. Engineers do not design an electric motor to consume power in the form of heat, they simply cannot avoid such losses, their goal is to design motors that converts electrical power to mechanical power, not heat.

So I have tried to put it in terms the OP might understand which is what I have been saying all along. True power is the actual power supplied by the source in watts. The apparent power is a derived number, but this power is not expended, however the current required to calculate this number is delivered from source to load. The load will expend the true power minus any losses due to resistance in the power chain.

I do thank you for your patience, but again please please stop repeatedly explaining things that people know all too well already and have previously told you so. How would you feel about it if I kept trying to explain the same to you? Actually I do remember long time ago I was the one who had to correct you once when you disregard the consideration of the "phase angle" thing.

Finally I have to repeat just one more time that the only main point I say you are incorrect, is the way you use the term true power in the very application (speakers, motors, not just a electrical circuit/network) we have been discussing. The definition you have just provided is fine, but not the way you had it taken out of context in previous posts. If I cannot make this clear to you by now I probably never will so I am ready to quit.

The fuse in the line will blow according to the calculations for the apparent power. The load (speaker voice coil burn out) will depend on the true (actual power) delivered from the source minus line losses. So when I originally stated the blowing of the OPs fuse will track the current from the the apparent power and whether the voice coil burns or not will relate to true power, I was correct. I maintain I have been consistent about that through out, and that that is the correct analysis of the situation presented.

You sure can maintain your position and if you now want to once again define true power for a speaker load as I²R then we are in fact saying exactly the same thing so you are correct but I have also been quite consistent in saying that you are confusing the issue.

You stated in your own definition, that true power is not just power that converts into heat, but also sound and mechanical power. There is a possibilty, however unlikely, that the OP might have thought you meant the sound part rather than the I²R part because it is normal to think that in this case true power means the power converted to sound power plus a little bit of mechanical power due to the fact that the speaker cone does move quite a bit at high frequencies. We both know the efficiency of speakers are extremely low but others may not. In other words, people may intuitively think that true power for a heater is the power consumed to convert electrical power (strictly speaking consumption unit is energy not power) into heat, for a motor it is the mechanical power plus a little losses in the form of heat, for light bulbs it is the light it emits plus losses in the form of heat, and therefore for loudspeaker it is the sound it produces plus losses in the form of heat.

At the end of the day, may be you can call it six and I call it half a dozen and we can move on to other less boring topics next time. I know what the truth and fact are though.

Just curious, since you have studied amps and speakers extensively, have you studied Fourier Analysis? When I studied it in university I really didn't think too much of it until I had to take a course in communication years later. Then I realize how useful it is and consider it indispensable for anyone interested in audio and telecommunication engineering. It is the best thing, if not the only thing I know that allows engineers to analyze signal waveforms and understand what harmonics really are. Without Mr. Fournier, we would have no cell phones and we probably won't have anything to argue about.

 

[TLS Guy]

Let me borrow what 3 db said to you in post#26:

"I have a degree in Electrical and am well versed in this. " and please stop trying to explain those things that I myself have posted many times on this forum!!

I really cannot understand why you still fail to understand I was asking you to define "true power" for loads such as loudspeakers and electric motors. When you finally took the time to define it you did say what I was waiting for you to say:

"I'm defining true power as the power consumed by the load and converted into heat, sound, mechanical energy or what ever." instead of the simplistic I²R for a RLC (resistance, inductance, capacitance) circuit. And, the key words "converted into sound, mechanical energy....."

I sure hope others can see the confusion you have created by saying it is the true power consumed by the load (in your previous posts) that blow a speaker. Yes, as EE I am saying true power in the case of speakers, motors and loads of similar complex nature do take on meanings other than just the power converted into heat as you stated in your own definition. Engineers do not design an electric motor to consume power in the form of heat, they simply cannot avoid such losses, their goal is to design motors that converts electrical power to mechanical power, not heat.



I do thank you for your patience, but again please please stop repeatedly explaining things that people know all too well already and have previously told you so. How would you feel about it if I kept trying to explain the same to you? Actually I do remember long time ago I was the one who had to correct you once when you disregard the consideration of the "phase angle" thing.

Finally I have to repeat just one more time that the only main point I say you are incorrect, is the way you use the term true power in the very application (speakers, motors, not just a electrical circuit/network) we have been discussing. The definition you have just provided is fine, but not the way you had it taken out of context in previous posts. If I cannot make this clear to you by now I probably never will so I am ready to quit.



You sure can maintain your position and if you now want to once again define true power for a speaker load as I²R then we are in fact saying exactly the same thing so you are correct but I have also been quite consistent in saying that you are confusing the issue.

You stated in your own definition, that true power is not just power that converts into heat, but also sound and mechanical power. There is a possibilty, however unlikely, that the OP might have thought you meant the sound part rather than the I²R part because it is normal to think that in this case true power means the power converted to sound power plus a little bit of mechanical power due to the fact that the speaker cone does move quite a bit at high frequencies. We both know the efficiency of speakers are extremely low but others may not. In other words, people may intuitively think that true power for a heater is the power consumed to convert electrical power (strictly speaking consumption unit is energy not power) into heat, for a motor it is the mechanical power plus a little losses in the form of heat, for light bulbs it is the light it emits plus losses in the form of heat, and therefore for loudspeaker it is the sound it produces plus losses in the form of heat.

At the end of the day, may be you can call it six and I call it half a dozen and we can move on to other less boring topics next time. I know what the truth and fact are though.

Just curious, since you have studied amps and speakers extensively, have you studied Fourier Analysis? When I studied it in university I really didn't think too much of it until I had to take a course in communication years later. Then I realize how useful it is and consider it indispensable for anyone interested in audio and telecommunication engineering. It is the best thing, if not the only thing I know that allows engineers to analyze signal waveforms and understand what harmonics really are. Without Mr. Fournier, we would have no cell phones and we probably won't have anything to argue about.

I agree we have spilt a lot of ink and not moved further ahead from my original brief advice to the OP in my first post in this thread.

And yes, I have studied Fournier analysis. I remember the first time I got interested in it. It was provoked by a question to me from my housemaster, father Fabian, when I was ten years old.

He had a table radio at the side of his desk. He knew I was interested in electronics. He asked me how the speaker in his radio, could reproduce violins, cellos, flutes, horns, trumpets etc, at the same time. I quickly realized I could not give him a complete coherent explanation. However I was savvy enough to realize the speaker could only move in one direction at a time.

So I had to read up on this, and was guided to Founier wave forms. After comprehending the problem, I was able to explain to Father Fabian, that his single speaker was actually only producing one sound wave, and how that wave was derived from the multiplicity of sounds in the orchestra.

I agree that if complex waves could not be broken down into multiple sine waves, we would have a terrible problem.