Sound Power Challenge

[Bob Crowley]

I'm certainly no technical expert, but I'd assume in a bass speaker for instance, because of the greater distance the cone is moving compared to a treble speaker (to keep the terms simple), I'd have thought that the elasticity of the diaphragm would also contribute to the energy load.

The bass speaker would have to stretch the diaphragm more and I suspect it would be a parabolic curve rather than a straight line graph.

 

[Mark Quayle]

The Inverse-Square Law is not about square waves. Paragraph three of the OP makes it clear that I'm talking about sine waves.

What? Why bring the inverse square law into this? Yes, I suppose paragraph 3 of the OP is about sinusoids, I'm not going to bother to go look. But your description I was talking about sounds like square waves, not sinusoids.

What more information do you need to answer the question?

I don't need more information. You give too much irrelevant information. What you need is a specific question that doesn't depend on muddy thinking for a premise. Your question, as it stands, is bogus.

I didn't mention a resistor. I mentioned a coil; and I used the word impedance in the the OP to describe the load. Later I used the word resistance to describe the load, because it seemed that you didn't understand inductive reactance. BTW, you didn't ask me the minimum impedance of the coil, nor what frequencies were passing through the coil. That could make a huge difference in your calculations; but It's completely irrelevant to the question. The fact that the higher frequency might meet greater impedance through the coil was just a side not to accentuate the fact that it will take more more wattage to produce the same amount of sound power at a lower frequency. The answer is simple when you understand it; so there's no need to create a complicated model.



Huh?

There is a 90 degree phase shift through an inductor. See ELI the ICE man.

Of course I didn't ask you the minimum impedance of the coil, nor what frequencies you were imposing on the coil because the actual numbers are irrelevant to the discussion. I wasn't (and you weren't) calculating.

Here's an example of your incomplete, or vague, statements: "There is a 90 degree phase shift through an inductor." 90 degree phase shift of WHAT? You don't say, "The voltage on the second side of the inductor is shifted 90 degrees from the first." You don't say, "In a circuit the current following an inductor is shifted 90 degrees from the voltage applied to the inductor." So it is hard to know what you are getting at. Furthermore, the current is indeed skewed from sinusoidal in the magnetic coil of the transducer you use for your "sound power" descriptions.

Go back through your OP. You might sound to you like you make perfect sense, but you are not. I'm not saying that I'm any better at writing —obviously, I'm not getting through to you what my problem is with your question/writing— but...

Anyhow, power out equals power in —"power out" including heat produced and air moved in a transducer. The more violent the motion of any given transducer, obviously the higher amplitude voltage it takes to drive it.

NOW can you describe more clearly the phenomenon you want explained?

 

[AV1611VET]

I don't want you to feel like I'm ignoring you.

I've been thinking since yesterday how I could walk through this with you using that model. I started come up with one way to explain it; but as I worked through it, the explanation seemed to be more complicated than the model in the OP.


I'll keep trying.

LOL -- Thanks, Hark, but I was just being silly.

But for some reason though, the comb kazoo popped right into my mind when I read your post.

I think Bose was on the cutting edge of sound equipment technology at one time.

 

[HARK!]

I think Bose was on the cutting edge of sound equipment technology at one time.

Bose boosts the 3rd harmonic in their cabinet design, to trick the brain into believing that the ear is hearing bass. I like real bass. Back in the early 90's I wrote a computer program to build speaker cabinets for flat response using Thiel-Small parameters. I used JBL speakers, because depending on how speaker companies measured the characteristics of their speakers, they could present specifications on those parameters which might not be a true representation of real world performance. Each speaker manufacturer would present specifications on their speakers, which would put their speakers in the best light. The AES sought to solve this problem by creating standardized testing procedures. JBL was the only company at that time which subscribed to AES standards; and they touted that they met or exceeded all of AES's standards. I set up a small shop to build custom cabinets as a branch of my business; but I probably needed a better salesman, than myself, for the product. I ended up shutting down that shop about a year later.

Bose does have their place. If you're in an apartment; and you want to be enveloped in your music, without rattling the dishes in your neighbors china cabinet; Bose might be a good choice.

 

[HARK!]

Anyhow, power out equals power in —"power out" including heat produced and air moved in a transducer. The more violent the motion of any given transducer, obviously the higher amplitude voltage it takes to drive it.

You're getting warmer.

 

[AV1611VET]

Bose does have their place. If you're in an apartment; and you want to be enveloped in your music, without rattling the dishes in your neighbors china cabinet; Bose might be a good choice.

What's your take on Marantz and Pioneer speakers?

 

[HARK!]

What's your take on Marantz and Pioneer speakers?

I had no respect for Pioneer speakers in the '90's. I did have a Marantz amplifier at the time, which now I wish I had never let go. It was very basic. They did a great job with the filters (tone controls) on that one. I still have another Marantz amplifier that sold for $2000 back in 1978. You could buy a brand new car for that back then. I keep it as a novelty, because it has an oscilloscope built into it, and it's a quad amplifier (Quad was an awesome idea, much superior to surround sound IMO.). However, the filters in that amp are seriously lacking.

I can't speak on the qualities of what's on the market now. I backed out of the sound reproduction industry by the late '90's. Does anyone even buy nice stereos anymore?

 

[HARK!]

I'm certainly no technical expert, but I'd assume in a bass speaker for instance, because of the greater distance the cone is moving compared to a treble speaker (to keep the terms simple), I'd have thought that the elasticity of the diaphragm would also contribute to the energy load.

The bass speaker would have to stretch the diaphragm more and I suspect it would be a parabolic curve rather than a straight line graph.

How far the speaker cone moves in and out is dependent on the voltage. How fast it it moves in and out is dependent on the frequency. Theoretically, in a perfect world, the cone would move just as far, in and out, at a higher frequency (treble) and a lower frequency (bass) if they were both being driven by a voltage of the same amplitude. There are other factors that stand in the way of this oversimplified explanation being all equal in reality; but the reason why the bass pushes the speaker cone out further when we are listening to music, is because more voltage is being applied to the speaker at lower frequencies, to accurately reproduce the bass in proper ratio, to the treble, in the original recording.

All of that said, that is not the reason why it takes more electrical power to produce the same amount of sound power at a lower frequency.

Now that I'm thinking through this, so many years later, I'm starting to question the JHU Physicists explanation. I might have another explanation. I think he was on the right track; but think through this, I suspect that there might be a slightly different explanation. I'm still thinking this through.

I'll present my thoughts after I reveal his explanation.

 

[HARK!]

How far the speaker cone moves in and out is dependent on the voltage. How fast it it moves in and out is dependent on the frequency. Theoretically, in a perfect world, the cone would move just as far, in and out, at a higher frequency (treble) and a lower frequency (bass) if they were both being driven by a voltage of the same amplitude. There are other factors that stand in the way of this oversimplified explanation being all equal in reality; but the reason why the bass pushes the speaker cone out further when we are listening to music, is because more voltage is being applied to the speaker at lower frequencies, to accurately reproduce the bass in proper ratio, to the treble, in the original recording.

All of that said, that is not the reason why it takes more electrical power to produce the same amount of sound power at a lower frequency.

Now that I'm thinking through this, so many years later, I'm starting to question the JHU Physicists explanation. I might have another explanation. I think he was on the right track; but think through this, I suspect that there might be a slightly different explanation. I'm still thinking this through.

I'll present my thoughts after I reveal his explanation.

Yep, I believe that I have just debunked the JHU Physicists explanation. I'll still provide it later; and I'll provide a simple analogy which seems to disprove his explanation. I still have to give him credit for trying; and I give him credit for pointing me in the right direction.

 

[SelfSim]

I could have said the same thing! Read your first post again. You are not specific enough when presenting your thesis. You speak in confusing generalities.

Agreed.

What more information do you need to answer the question?

A circuit diagram of the respective circuits you're referencing, denoted by the relevant circuit element and power supply parameter values, would be a good start.
I've been watching this thread and, (now), two pages into it, I still don't have a clue as to why you think there's any question at all to be answered.
(Thread just looks like a fishing expedition in a pond devoid of edible fish, IMO).

 

[HARK!]

A circuit diagram of the respective circuits you're referencing, denoted by the relevant circuit element and power supply parameter values, would be a good start.
I've been watching this thread and, (now), two pages into it, I still don't have a clue as to why you think there's any question at all to be answered.
(Thread just looks like a fishing expedition in a pond devoid of edible fish, IMO).

You're making this far too complicated. Since you seem to have trouble grasping what I'm trying to convey; I'll oversimplify it for you.

You have a sine wave generator, an amp, and a speaker. That is your circuit. The amp delivers a flat response. It's a perfect world.

Run the two different frequencies, at the same amplitude through the system, at two different times.

Remember, one frequency at a time.

You put a DB meter at a fixed distance so that it is at the peak of the compression cycle for both waves. Pick two that will crest at the same distance, within a reasonable listening distance. The lower frequency will register lower on the DB meter.

Why?

Go fish.

 

[SelfSim]

You're making this far too complicated. Since you seem to have trouble grasping what I'm trying to convey; I'll oversimplify it for you.

Your oversimplifications force a basically useless and uninteresting answer, (which I'll provide below).

You have a sine wave generator, an amp, and a speaker. That is your circuit. The amp delivers a flat response. It's a perfect world.

Run the two different frequencies, at the same amplitude through the system, at two different times.

Remember, one frequency at a time.

You put a DB meter at a fixed distance so that it is at the peak of the compression cycle for both waves. Pick two that will crest at the same distance, within a reasonable listening distance. The lower frequency will register lower on the DB meter.

Low frequencies require the movement of more air compared with that needed for higher frequencies. Moving a larger volume of air, requires more power. If the supply power is fixed, then the measured acoustic power output from the speaker will be less.

Go fish.

Why?

 

[HARK!]

Low frequencies require the movement of more air compared with that needed for higher frequencies. Moving a larger volume of air, requires more power. If the supply power is fixed, then the measured acoustic power output from the speaker will be less.

In both cases, the signals are at the same amplitude. This means that the excursion of the cone will be the same for each cycle, no matter what the frequency.

 

[SelfSim]

In both cases, the signals are at the same amplitude. This means that the excursion of the cone will be the same for each cycle, no matter what the frequency.

Lower frequencies require the speaker cone deflections (up to the max amplitude) to evolve over a longer period of time, which requires more net delivered electrical power per signal cycle.
The pressure is also required to be distributed over a larger cone area of the speaker.

 

[Mark Quayle]

In both cases, the signals are at the same amplitude. This means that the excursion of the cone will be the same for each cycle, no matter what the frequency.

In a perfect world, yes.

You're making this far too complicated. Since you seem to have trouble grasping what I'm trying to convey; I'll oversimplify it for you.

You have a sine wave generator, an amp, and a speaker. That is your circuit. The amp delivers a flat response. It's a perfect world.

Run the two different frequencies, at the same amplitude through the system, at two different times.

Remember, one frequency at a time.

You put a DB meter at a fixed distance so that it is at the peak of the compression cycle for both waves. Pick two that will crest at the same distance, within a reasonable listening distance. The lower frequency will register lower on the DB meter.

Why?

Go fish.

Your oversimplifications force a basically useless and uninteresting answer, (which I'll provide below).

Low frequencies require the movement of more air compared with that needed for higher frequencies. Moving a larger volume of air, requires more power. If the supply power is fixed, then the measured acoustic power output from the speaker will be less.

Why?

Finally I can stop fishing around to figure out what your question really is. If you (HARK!) had asked this question as you state it here to begin with, instead of introducing all sorts of irrelevant (and false, or at least mis-stated) assumptions, you might have gotten an answer sooner.

In a real world there are many reasons. In a perfect world, there is also the fact that lower frequencies in the air, let's say as measured from 5 feet of distance from the transducer, have radiated from the direction of the motion of the piston (cone, or what have you), 'in front', to all other directions --the lower the frequency, the more spherical the pattern of radiation. (This is also why it is more difficult for the ear to get directional information from lower sinusoidal sound.) The high frequencies do not radiate the same, as the compression and rarefaction occur too quickly to spread to the side as readily. At 5 feet distance, then, for the higher frequencies, more energy is still concentrated in front of the transducer, where the measuring device is located.

 

[HARK!]

In a perfect world, yes.




Finally I can stop fishing around to figure out what your question really is. If you (HARK!) had asked this question as you state it here to begin with, instead of introducing all sorts of irrelevant (and false, or at least mis-stated) assumptions, you might have gotten an answer sooner.

In a real world there are many reasons. In a perfect world, there is also the fact that lower frequencies in the air, let's say as measured from 5 feet of distance from the transducer, have radiated from the direction of the motion of the piston (cone, or what have you), 'in front', to all other directions --the lower the frequency, the more spherical the pattern of radiation. (This is also why it is more difficult for the ear to get directional information from lower sinusoidal sound.) The high frequencies do not radiate the same, as the compression and rarefaction occur too quickly to spread to the side as readily. At 5 feet distance, then, for the higher frequencies, more energy is still concentrated in front of the transducer, where the measuring device is located.

Ah Q(f); but why would you assume that the directivity factor is the cause, rather than a result of the cause?

So why is it that when two sound waves, at two different frequncies, are produced in the X region, 0-26 Hz, where the propagation more resembles that of heat (in other words, no directivity) ; that the same phenomenon prevails?

 

[Mark Quayle]

Ah Q(f); but why would you assume that the directivity factor is the cause, rather than a result of the cause?

They are a result of the cause, no doubt, and in their own right a cause of the phenomenon you wanted explained, but not THE cause, and I didn't describe them as THE cause. But: in a perfect world, the driver has no mass, no physical resistance other than the air, no magnetic air gap, an infinitely thinly wafered magnetic core, no resonant frequency --almost none of the several things you began this conversation with.. Thus the excursion for high frequency is no more difficult than for low frequency, and the coil construction the same for both frequencies --in a perfect world.

So why is it that when two sound waves, at two different frequncies, are produced in the X region, 0-26 Hz, where the propagation more resembles that of heat (in other words, no directivity) ; that the same phenomenon prevails?

This is a separate, though related, question from the one about the waveform amplitude 'in front of' the speaker.

All sounds propagating from a central point (the driver) have directivity. The difference from left eardrum compared to right eardrum, however, at a low frequency is hardly discernible, but at a high frequency there is discernible difference between amplitude of peaks and valleys, left ear compared to right. Limiting the matter to 26 Hz was mere conversation on your part, I expect, as direction is still hard to find for more than triple that frequency, and below 25 Hz many, if not most, humans 'feel' encumbered at high volumes rather than actually 'hearing' a sinusoidal sound. Two different frequencies below 25 Hz, then, is pretty much irrelevant. That is, one would be pretty much the same as the other as far as orientation goes.

But I think what you may be asking in this last post is, "How does the closer distances from peaks to valleys in the higher frequency waveforms mitigate sideways propagation compared to the lower frequency waveforms?" Well, the physically larger regions of compression vs rarefaction allow time for the compression (or rarefaction) to propagate into any place (for eg, sideways) they are not bound by similar air pressures. Likewise, amplitude for the ear to hear low frequencies is also higher than for the higher frequencies, thus the difference between peaks and valleys tends to cause more dissipation at the sides of the radiation rather than maintaining an 'in front' characteristic

Now I have a question for you. Why, in a gas medium, does this phenomenon appear to demonstrate the opposite from that of a liquid at the surface? That is, why do low surface frequencies in a liquid (actual waves on the surface of a liquid) appear to maintain consistency of form more easily than high frequencies?

Another thing, do low frequencies of sound in a gas medium maintain integrity over distances better than high frequencies, and is the same true well below the surface of a liquid medium? Note, that directional discernment is very limited even in high frequencies below the surface of a liquid, because of the high speed of sound propagation. That is, a high frequency waveform is longer in water than in air.

 

[HARK!]

This is a separate, though related, question from the one about the waveform amplitude 'in front of' the speaker.

It's not separate at all. It undermines your presumption. Sinusoidal amplitudes >0 and <26 HZ are measurable 'in front of' the speaker.

All sounds propagating from a central point (the driver) have directivity.

No they don't. Only audible sound in the A,B, and C regions are directive in varying degrees. Sound in the X region is not directive. This is settled science.

All sounds propagating from a central point (the driver) have directivity. The difference from left eardrum compared to right eardrum, however, at a low frequency is hardly discernible, but at a high frequency there is discernible difference between amplitude of peaks and valleys, left ear compared to right

You have some to learn about psychoacoustics; but that is not within the scope of this challenge.

Limiting the matter to 26 Hz was mere conversation on your part

Not at all. It dismissed directivity factor as being the primary reason, in regions A and up, and completely dismisses it for the X region.

I expect, as direction is still hard to find for more than triple that frequency, and below 25 Hz many, if not most, humans 'feel' encumbered at high volumes rather than actually 'hearing' a sinusoidal sound. Two different frequencies below 25 Hz, then, is pretty much irrelevant. That is, one would be pretty much the same as the other as far as orientation goes.

We don't need the subjectivity of human ears to make our measurements. We have a dB meter.

 

[Mark Quayle]

It's not separate at all. It undermines your presumption. Sinusoidal amplitudes >0 and <26 HZ are measurable 'in front of' the speaker.

The question I was dealing with was directivity. To me, that implies what direction one hears a sound as coming from.

No they don't. Only audible sound in the A,B, and C regions are directive in varying degrees. Sound in the X region is not directive. This is settled science.

The question I was dealing with was directivity. To me, that implies what direction one hears a sound as coming from.

You have some to learn about psychoacoustics; but that is not within the scope of this challenge.

The question I was dealing with was directivity. To me, that implies what direction one hears a sound as coming from.

Not at all. It dismissed directivity factor as being the primary reason, in regions A and up, and completely dismisses it for the X region.

That is what I said. (Or are you defining directivity by how well any given frequency maintains amplitude as one recedes from the speaker compare to the same distances for another frequency?) Either way, I have already answered that with the way a low frequency's radiation is physically permitted to 'leak over' past the angle of its edges more than that of the high frequency.

We don't need the subjectivity of human ears to make our measurements. We have a dB meter.

If "directivity" means only amplitude maintenance over distance, you are right. Notice, though, I was not referring to the human ears as measuring devices, but as comparison devices, one ear against the other. Just saying...

I AM beginning to tire of the talking past each other. Particularly when it lends one to arrogance.

 

[HARK!]

The question I was dealing with was directivity. To me, that implies what direction one hears a sound as coming from.

The sound comes from its' origin no matter where the listener is in reference to that origin.

At high frequencies, sound is highly directive. The higher the frequency, the more it behaves like light. In the C region, the sound will a narrow dispersion pattern. Outside of that pattern, the amplitude of that sound pattern will quickly roll off. That dispersion pattern is emitted from the front of the driver. Now let's put that driver in a lead cabinet, with walls 3 feet thick. We might not expect to hear much coming off of the cabinet; as 3 foot thick lead walls don't vibrate very much.Let's make it a perfect world and say that we will hear nothing. Then we suspend that cabinet in free air; so that we don't hear any reflected sound. Now we will suspend ourselves behind the cabinet, in the opposite direction of where the sound is being directed. We will hear where the sound is coming from; but we won't hear it from where it is being directed.

We take the same cabinet in the same conditions, and put a frequency in the X region through it; and the amplitude of the frequency will be virtually the same in all directions; as in the X region sound behaves like heat.

(Or are you defining directivity by how well any given frequency maintains amplitude as one recedes from the speaker compare to the same distances for another frequency?)

If "directivity" means only amplitude maintenance over distance, you are right. Notice

Directivity is how much the amplitude rolls off, off axis to the driver. The faster it rolls off, off axis, the higher the directivity.