Differences in drivers.
Hi Steve,
Good you asked this question. I have several bass units from different manufacturers with different specs.
The one with a wider bandwidth does sound "tighter" in the bass when played in free air. The difference is quite large and you do not have to look for it. So the bandwidth 'does' make a difference.
In a system with mid and tweeter the relative level of the upper frequencies with respect to the bass does affect the 'tightness' in the bass. I am not quite sure the 'bass harmonic' frequencies extend up to the tweeter frequencies. See the spectrum I got from a well recorded bass drum. In a two way it probably does but in a three way it might not reach up to the tweeter ( approx above 3 to 5 Khz).
The amp also contributes quite a lot. That should be a different thread.
Cheers.
Hi Steve,
Good you asked this question. I have several bass units from different manufacturers with different specs.
The one with a wider bandwidth does sound "tighter" in the bass when played in free air. The difference is quite large and you do not have to look for it. So the bandwidth 'does' make a difference.
In a system with mid and tweeter the relative level of the upper frequencies with respect to the bass does affect the 'tightness' in the bass. I am not quite sure the 'bass harmonic' frequencies extend up to the tweeter frequencies. See the spectrum I got from a well recorded bass drum. In a two way it probably does but in a three way it might not reach up to the tweeter ( approx above 3 to 5 Khz).
The amp also contributes quite a lot. That should be a different thread.
Cheers.
Not IF their response (which should reach above the crossover frequency) is taken into account PROPERLY when designing the crossover.
Regards
Charles
That's the point
Even guys at JBL give sensitivity and distortion figures of a 18" subwoofer like 2241 between 100 and 500 Hz, following aes-standards, crazy imho, why not use it as a mid-range, it's useable upto 800Hz max cutoff.
Numbers are not enough to design a good x-over.
Allthough having a big magnet, good fabrication and so on, this 18 incher is not capable of reproducing a good bass if used on the max of the given specs (ie. crossed at 800Hz).
imho excellent upto 80 Hz , 120 Hz max, that's what you paid for, so roughly 10 times less as quoted
http://www.jblpro.com/pages/pub/components/2241.pdf
Even guys at JBL give sensitivity and distortion figures of a 18" subwoofer like 2241 between 100 and 500 Hz, following aes-standards, crazy imho, why not use it as a mid-range, it's useable upto 800Hz max cutoff.
Numbers are not enough to design a good x-over.
Allthough having a big magnet, good fabrication and so on, this 18 incher is not capable of reproducing a good bass if used on the max of the given specs (ie. crossed at 800Hz).
imho excellent upto 80 Hz , 120 Hz max, that's what you paid for, so roughly 10 times less as quoted
http://www.jblpro.com/pages/pub/components/2241.pdf
Re: Differences in drivers.
You are 100% right, when you play it in free air, without xover, without mid/tweeter
Jan Didden
ashok said:
You are 100% right, when you play it in free air, without xover, without mid/tweeter
Jan Didden
7V said:
Consider that one definition of good vrs great is "what does it do at 40 dB down?"
at 4 kHz -- 1st order, 15 dB down, 2nd order 27 dB down, 3rd order, 39 dB down
So in all but the situations where you have a very steep XO you will have a difference, and that steep XO has its own issues.
dave
Static resistance.
I am not sure how this applies to normal music , but static resistance is higher than dynamic resistance. Like pushing a trolley - you have to push harder to start it rolling and then it needs less force to keep it moving.
So the stationery to start movement of the cone needs lots of power as compared to generating a full waveform. Maybe someone should measure this on some drivers and see what we get. Use a one cycle 30Hz waveform and determine the driver's output.
I think the lighter drivers would probably fare better as someone mentioned earlier. But then again the lighter drivers may have to be equalised to produce deep bass. That is something we want to avoid.
I am not sure how this applies to normal music , but static resistance is higher than dynamic resistance. Like pushing a trolley - you have to push harder to start it rolling and then it needs less force to keep it moving.
So the stationery to start movement of the cone needs lots of power as compared to generating a full waveform. Maybe someone should measure this on some drivers and see what we get. Use a one cycle 30Hz waveform and determine the driver's output.
I think the lighter drivers would probably fare better as someone mentioned earlier. But then again the lighter drivers may have to be equalised to produce deep bass. That is something we want to avoid.
A powerful amplifier with a lot of capacitance would be a good way to make woofers respond, I think. That way, even if the power supply's rails cannot support transients, there is enough stored juice that the amplifier will not run out of power starting the cone.
Maybe Velodyne has it right with their servo-control stuff. Their amplifiers actually monitor the woofers' response to the transient and put out more current if the woofer is not meeting the needs of the signal. It's like how some cadillacs monitor how well the car's steering is meeting the demands of the driver, and selectively apply the rear brakes independently to help the car turn.
Maybe Velodyne has it right with their servo-control stuff. Their amplifiers actually monitor the woofers' response to the transient and put out more current if the woofer is not meeting the needs of the signal. It's like how some cadillacs monitor how well the car's steering is meeting the demands of the driver, and selectively apply the rear brakes independently to help the car turn.
Re: Static resistance.
It is totally beyond me why someone pushing a cart in a supermarket makes the giant leap to conclude that to "start" a woofer would need more energy then to sustain movement.
This is how "common knowledge" starts, I guess. In the next post, already the leap is made to amp energy storage. Amazing!
Jan Didden
PS I have another one for you: when the sine wave goes from pos to neg, it inverts direction. That means stop and then start. Would that be infinite acceleration for the cone?
ashok said:
It is totally beyond me why someone pushing a cart in a supermarket makes the giant leap to conclude that to "start" a woofer would need more energy then to sustain movement.
This is how "common knowledge" starts, I guess. In the next post, already the leap is made to amp energy storage. Amazing!
Jan Didden
PS I have another one for you: when the sine wave goes from pos to neg, it inverts direction. That means stop and then start. Would that be infinite acceleration for the cone?
BAM said:
The woofer does not respond to the transient, because the woofer never sees the transient. Please read the relevant posts before repeating the blatant nonsense.
Jan Didden
We can even go a step further:
Even if we had a single wideband transducer, the cone MOVEMENT doesn't have to follow the input voltage to produce a PRESSURE response equal to the input voltage step. Simply due to the fact that the radiation resistance is rising with frequency.
In other words: The cone of a perfect wideband transducer would move in a triangular fashion approx when reproducing a rectangular input signal !
Regards
Charles
Hmmm. The squarewave signal would cause a linear increasing current in an ideal voice coil inductance, there's your triangle. Then the cone would move according to the linearly increasing current producing an excusion with constant velocity - or was it constant acceleration?
(Dick Pierce where are you???)
But, if the radiation impedance is resistive, wouldn't the voice coil impedance be resistive rather than inductive as well?
I do know that motional feedback often works by returning the accelaration rather that the velocity of the cone (using a differentiator in the feedback loop).
Jan Didden
(Dick Pierce where are you???)
But, if the radiation impedance is resistive, wouldn't the voice coil impedance be resistive rather than inductive as well?
I do know that motional feedback often works by returning the accelaration rather that the velocity of the cone (using a differentiator in the feedback loop).
Jan Didden
Re: Re: Static resistance.
A body continues in its state of rest or of uniform motion in a straight line, until acted upon by an external force.
And ...
force = mass x acceleration
(from Newton's laws of motion)
Steve
janneman said:
A body continues in its state of rest or of uniform motion in a straight line, until acted upon by an external force.
And ...
force = mass x acceleration
(from Newton's laws of motion)
Steve
This, together with the increasing radiation resistance makes for the linear amplitude response while cone amplitude is decreasing with frequency.
This is the primary effect. The VC inductance (which should be zero for an ideal driver) is just causing an additional pole at the upper end.
Regards
Charles
Physics.
This follows the basic laws of Physics. Once the object is in motion you only need to supply energy to overcome frictional losses. To 'start' you need to supply energy ( which a moving mass has by virtue of its motion) which the 'mass' does not have while it is stationary and the energy to overcome the frictional forces.
If you mean the crossing about the X axis as we see a sinewave on a graph :
The 'zero' position ( crossing the X axis) is the location where the cone is travelling "fastest"! This is not a positive to negative transition. That transition occurs at the extreme ends of the waveform ( extreme ends of cone travel - top and bottom of a Sine wave). There the cone decelerates to zero and starts accelerating in the opposite direction. On the X axis ( Zero position) the acceleration is 'zero' and velocity is at a maximum.
You will not find infinite acceleration anywhere - it is not required.
This could have been clarified very easily - politely! I respect everyone's opinion. We could make humorous cracks at some posts( also humorous to the source of the post ) . There is no need to get 'rough' ! This is a great forum - we should take all kinds of views with the refinement that Humans should have.
Cheers.
This follows the basic laws of Physics. Once the object is in motion you only need to supply energy to overcome frictional losses. To 'start' you need to supply energy ( which a moving mass has by virtue of its motion) which the 'mass' does not have while it is stationary and the energy to overcome the frictional forces.
If you mean the crossing about the X axis as we see a sinewave on a graph :
The 'zero' position ( crossing the X axis) is the location where the cone is travelling "fastest"! This is not a positive to negative transition. That transition occurs at the extreme ends of the waveform ( extreme ends of cone travel - top and bottom of a Sine wave). There the cone decelerates to zero and starts accelerating in the opposite direction. On the X axis ( Zero position) the acceleration is 'zero' and velocity is at a maximum.
You will not find infinite acceleration anywhere - it is not required.
This could have been clarified very easily - politely! I respect everyone's opinion. We could make humorous cracks at some posts( also humorous to the source of the post ) . There is no need to get 'rough' ! This is a great forum - we should take all kinds of views with the refinement that Humans should have.
Cheers.
Re: Physics.
Cheers to you,
Jan Didden
ashok said:
This follows the basic laws of Physics. Once the object is in motion you only need to supply energy to overcome frictional losses. To 'start' you need to supply energy ( which a moving mass has by virtue of its motion) which the 'mass' does not have while it is stationary and the energy to overcome the frictional forces.
/start Janneman:
Indeed, but the cone of a woofer never travels with constant velocity (that would be a DC signal). The cone is constantly accelerating and decelerating - in other words, the first derivative of the speed will never be zero (OK, except at the signal apex). Therefor, the cart analogy is flawed. It would be a good analogy when the shopper would constantly accelerate/decelerate the cart, but then he would quickly discover that that would take as much energy as the initial push.
/end janneman
If you mean the crossing about the X axis as we see a sinewave on a graph :
The 'zero' position ( crossing the X axis) is the location where the cone is travelling "fastest"! This is not a positive to negative transition. That transition occurs at the extreme ends of the waveform ( extreme ends of cone travel - top and bottom of a Sine wave). There the cone decelerates to zero and starts accelerating in the opposite direction. On the X axis ( Zero position) the acceleration is 'zero' and velocity is at a maximum.
You will not find infinite acceleration anywhere - it is not required.
/start Janneman:
Indeed again. At least SOMEONE does his thinking. How many of you accepted my statement at face value? Shame on you all!
/end Janneman
This could have been clarified very easily - politely! I respect everyone's opinion. We could make humorous cracks at some posts( also humorous to the source of the post ) . There is no need to get 'rough' ! This is a great forum - we should take all kinds of views with the refinement that Humans should have.
/start Janneman. Sorry, sometimes I get carried away. No intention to hurt anyones' feelings. Apologies.
/end Janneman
Cheers.
Cheers to you,
Jan Didden
Jan's reply.
Thanks Jan !
That was a great reply !
One for you ----
One for me -----
Cheers.
Ashok.
Thanks Jan !
That was a great reply !
One for you ----
One for me -----
Cheers.
Ashok.
Okay, some calculus.
Fact: Any function has a derivative. The derivative of the function is (basically) the slope of the function at every point; that is to say, if the position of the woofer cone is a function, the derivative of that is the velocity of the woofer, which is also a function. The derivative of the velocity function is acceleration.
Newton's laws pretty well damn the notion of velocity or acceleration, and ensure that there will be no undefined points in any of the derivative functions.
Square waves are impossible to produce for this reason; the derivative of the square wave graph is zero, with a bunch of undefined points where the graph slews up or down! It is mathematically and physically impossible for a speaker to produce this, or an amp, or even a computer, outside of theory!
The cool thing about a sine wave is that the derivative of a sine wave is an inverted cosine wave; the derivative of that is an inverted sine wave, and the derivative of that is a cosine wave. Sine waves are as smooth as they can get; that's why when you see something exibiting sinusoid motion, it seems very smooth and natural, and nice to look at.
Transients from kick drums can be represented as lots of sine waves of different frequencies, amplitudes, and phases, on top of one another. If the woofer reproduces the lowest frequencies well and the tweeter produces the highest frequencies well, and there are no frequencies that are the wrong amplitude or phase, you will get an EXACT replica of the kick drum out your speaker. This is, of course, the definition of an ideal speaker, and AFAICT, it hasn't ever been built yet.
Key word: yet.
Fact: Any function has a derivative. The derivative of the function is (basically) the slope of the function at every point; that is to say, if the position of the woofer cone is a function, the derivative of that is the velocity of the woofer, which is also a function. The derivative of the velocity function is acceleration.
Newton's laws pretty well damn the notion of velocity or acceleration, and ensure that there will be no undefined points in any of the derivative functions.
Square waves are impossible to produce for this reason; the derivative of the square wave graph is zero, with a bunch of undefined points where the graph slews up or down! It is mathematically and physically impossible for a speaker to produce this, or an amp, or even a computer, outside of theory!
The cool thing about a sine wave is that the derivative of a sine wave is an inverted cosine wave; the derivative of that is an inverted sine wave, and the derivative of that is a cosine wave. Sine waves are as smooth as they can get; that's why when you see something exibiting sinusoid motion, it seems very smooth and natural, and nice to look at.
Transients from kick drums can be represented as lots of sine waves of different frequencies, amplitudes, and phases, on top of one another. If the woofer reproduces the lowest frequencies well and the tweeter produces the highest frequencies well, and there are no frequencies that are the wrong amplitude or phase, you will get an EXACT replica of the kick drum out your speaker. This is, of course, the definition of an ideal speaker, and AFAICT, it hasn't ever been built yet.
Key word: yet.
I do basically agree but one has to add that all these sinusoids are multiplied each with an own windowing function (i.e. their amplitude is a function of time).
Regards
Charles
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