Brian, you confuse me. I wasnt really talking about step response, i was talking of square waves. I know there is no spectral components of a square wave below its fundemental, but there are spectral contents above its fundemental. If moving coil speakers have no attempt at achieveing perfect impulse response, square wave response, or in any way come close to perfect signal tracking then why even bother. Perhaps you all have given up on the quest for the perfect loudspeaker, but I'm still young and I'd like to see multimedia to come to a point where it can only be seperated from reality by puporsed flaws. so we either need perfect reproduction of sound and video, or something you can stick into the back of your head like the matrix.
BassAwdyO: I dont know why he posted info on step/impulse response ,when you asked about square wave.
What youve got to understand is the IMPORTANCE of each of these measurements,and interpret them accordingly.
'oh my speakers do a square wave' - well what does that mean! Most people dont know.
The fact is that transducers themselves are reactive,while crossovers reactive also. So start reading those long articles!😀
http://www.geocities.com/kreskovs/Phase-B.html
What youve got to understand is the IMPORTANCE of each of these measurements,and interpret them accordingly.
'oh my speakers do a square wave' - well what does that mean! Most people dont know.
The fact is that transducers themselves are reactive,while crossovers reactive also. So start reading those long articles!😀
http://www.geocities.com/kreskovs/Phase-B.html
Just an FYI - the frequency response measurements were made with a CHIRP. Accepting that frequency response and time response are related to each other by the Fourier Transform, it follows that the driver with the wider bandwidth has faster rise times. In this case, adding mass did NOT lower the rise time; adding an inductor did.
In the classical Thiele/Small/Benson model of a loudspeaker driver, mass is a small secondary series inductance for the roll-off. You need a LOT of moving mass to get anywhere close to the inductive roll-off of even a modest voice coil.
Dan Wiggins
Adire Audio
In the classical Thiele/Small/Benson model of a loudspeaker driver, mass is a small secondary series inductance for the roll-off. You need a LOT of moving mass to get anywhere close to the inductive roll-off of even a modest voice coil.
Dan Wiggins
Adire Audio
While I appreciate what the moving mass experiments show, it should be made clear that delay in a woofer is not the same as the perceived "speed" of a woofer.
Delaying bass does make it sound slower, but it takes quite a few ms for it to be really noticeable, and the required delay increases as frequency decreases.
Still some configurations sound slower than others. Qts and F3 are definitely factors. As noted earlier, certain combinations of the two tend to sound fast. I've had plenty of experience of that playing with the filters on my synthesizer; resonant filters (which is what a loudspeaker is) can make a sound really fast and punchy, or very slow and boomy.
I'm sure there are other factors too, although it is hard to determine what they are without some double-blind tests.
Delaying bass does make it sound slower, but it takes quite a few ms for it to be really noticeable, and the required delay increases as frequency decreases.
Still some configurations sound slower than others. Qts and F3 are definitely factors. As noted earlier, certain combinations of the two tend to sound fast. I've had plenty of experience of that playing with the filters on my synthesizer; resonant filters (which is what a loudspeaker is) can make a sound really fast and punchy, or very slow and boomy.
I'm sure there are other factors too, although it is hard to determine what they are without some double-blind tests.
DanWiggins said:
Dan,
Rise time is just one aspect of speed. The entire issue of speed (the word literally) is really about definition. That is, on the time line, both the arrival time and "removal" time of each signal note need to be fast. In particular the removal time is hard to investigate or even be defined(that is why I put a similing face). The rise time only focuses on arrival time . Other factors such as distortion can be the places to find the answer because we can detect distortion down to -40db and changing mass does affect distortion characteristic. It is known that 2nd order distortion gives a perception of warm sound. If this 2nd order distortion is only dominant at low frequency, it may change our perception of an otherwise balanced (or coherent) sound.
I understand the entire issue is very complicated and difficult to solve, just like a detective cold case. And right now, there is no new evidence being presented.
Brian
Rythmik Audio
Mr Evil/Bryan,
Yes, I know that subjective evaluation of speed is completely different than what is being presented here. Our paper and experiments are more to show that mass does NOT make a driver slow or fast; leaning on moving mass as a determination for what is a fast driver is like leaning on sunlight being the cause of gravity.
Note then, by extension, the "acceleration factor" of BL/Mms becomes meaningless for "speed". It's really an efficiency factor, not bandwidth. SPL is directly proportional to acceleration; thus the acceleration factor is not bandwidth, but amplitude.
Fast bass is more about bandwidth, distortion, and decay rates. Which are related to bandwidth. Fast bass - perceived in a speaker - is usually the speaker with the best midbass. Dynamic range of the midbass becomes a big factor - compression (BL or thermal) is a big limiter in terms of perceived speed. At least, that's what we've found...
Dan Wiggins
Adire Audio
Yes, I know that subjective evaluation of speed is completely different than what is being presented here. Our paper and experiments are more to show that mass does NOT make a driver slow or fast; leaning on moving mass as a determination for what is a fast driver is like leaning on sunlight being the cause of gravity.
Note then, by extension, the "acceleration factor" of BL/Mms becomes meaningless for "speed". It's really an efficiency factor, not bandwidth. SPL is directly proportional to acceleration; thus the acceleration factor is not bandwidth, but amplitude.
Fast bass is more about bandwidth, distortion, and decay rates. Which are related to bandwidth. Fast bass - perceived in a speaker - is usually the speaker with the best midbass. Dynamic range of the midbass becomes a big factor - compression (BL or thermal) is a big limiter in terms of perceived speed. At least, that's what we've found...
Dan Wiggins
Adire Audio
BassAwdyO said:
The reason why I thought you would have talked about step response is that it is not a normal practice to use squre waves to evaluate speakers.
If your question is whether a good reproduction of square waveform is a necessary or a sufficient condition for a good sound reproduction. The answer is not either of them. If you know how nonlinear speakers are, it will drive you crazy. The square waveform response at say 90db is different from the square waveform response at say 100db. That is not to say there are no attemps to reproduce a near perfect square waveform. They were either very expensive or had failed due to flaws/deficiency in other area (such as not able to play loud, or high distortion at certain frequency, etc). I would encourage you to look at the entire chain of sound reproduction (from microphone pickup to speaker playback). When you do that, the ability to reproduce a square waveform at the very end of the chain is not that important any more.
Brian
Rythmik Audio
DanWiggins said:
Dan,
I wish you could put that at the first paragraph of the paper. Because all these factors (such as midbass reponse, thermal compression), with the exception of BL, are all mass related.
Brian
Rythmik Audio
Except, they're not. A high or low moving mass does not impact thermal compression, and it does not impact midbass response. It does affect efficiency, however.
Dan Wiggins
Adire Audio
Dan Wiggins
Adire Audio
DanWiggins said:
But, but.... Thermal compression is related to efficiency. With a higher efficiency speaker/subwoofer, the thermal compression is simply lower!!
Now the suggestion to put those in the paper is to provide another perspective of the question so the result will not be misquoted.
Brian
Rythmik Audio
Only in the most indirect method... The Eminence Beta 12CX is 8 dB more efficient than a Shiva, but the Shiva has less power compression than the Eminence. You reach 3 dB of power compression in the midbass region (80-320 Hz) at around 110 dB SPL with a Shiva; you'll hit 3 dB of compression with the Eminence Beta 12CX around 106 dB.
The way a driver dissipates heat is critical; in this case, the Shiva has a MUCH longer voice coil, with a thicker top plate, thicker pole piece, and better thermal dissipation characteristics. Yes, it is much more massive in terms of moving mass, but has less thermal compression. In essence, it takes more power to get the Shiva moving, but it handles the power much better than the Beta 12CX.
Remember, thermal compression isn't just power in; it's how well you dissipate that heat that is really the big issue.
Dan Wiggins
Adire Audio
The way a driver dissipates heat is critical; in this case, the Shiva has a MUCH longer voice coil, with a thicker top plate, thicker pole piece, and better thermal dissipation characteristics. Yes, it is much more massive in terms of moving mass, but has less thermal compression. In essence, it takes more power to get the Shiva moving, but it handles the power much better than the Beta 12CX.
Remember, thermal compression isn't just power in; it's how well you dissipate that heat that is really the big issue.
Dan Wiggins
Adire Audio
When we discuss whether a factor is important or not, we need to hold every other factor unchanged. Comparing 2 drivers with distinctive base structures or working principles does not constitue a fair study. For me, the simple question is if I just add 100g of moving mass to a woofer, does that make it more prone to the thermal compression than before.
Brian Ding
Rythmik Audio
Brian Ding
Rythmik Audio
The answer would be no. It wouldn't get as loud, but would still compress at the same power delivered.
Dan Wiggins
Adire Audio
Dan Wiggins
Adire Audio
directservo said:
That other "factors", include the SPL playback level and of course the frequency response (by equalization method). Otherwise, we can be comparing just the difference in frequency response.
Brian Ding
Rythmik Audio
That's a backwards way of saying, one way to reduce thermal compression is is to lower a woofer's moving mass. But if you are designing a driver there are always going to be other effects when you make that change.
Typically, yes. However, I've really never seen the case you're trying to set up. Does it happen? Theoretically, you can do it. In the real world, no...Mr Evil said:
Of course, with lower moving mass we also have less bass extension (Fs is higher), meaning that the lower end of the midbass scale may very well be thermally limited with the more efficient driver as compared to the lower efficiency driver! It takes more power to achieve a given SPL level because the driver is already in its controlled near Fb/below Fb roll-off...
Take a Beta 8CX, put it in a Qtc=0.707 box (7.5 liters). Measure the output; with 50W delivered, you'll get about 97 dB output at 80 Hz. Now add 15 grams to it (doubling the moving mass). You'll now have about 99 dB output at 80 Hz with 50W delivered. The efficiency "tradeoff" doesn't happen until 120-140 Hz or so. Below that point you actually GAIN real world output with the heavier cone.
Dan Wiggins
Adire Audio
DanWiggins said:
The difference in output at 80hz is because of the Q value has been changed and a higher mass gives a higher Q value. That increase in output is very local. We cannot draw any conclusion on a change of efficiency at a local point, such as 80hz. Now, if we move down the entire spectrum in the above discussion by one octave, that 120-140hz would have been 60-70hz which is midbass, and well within the spectrum where a subwoofer can be used. Would that have made a difference in your conclusion? If that doesn't cut it, how about move that another octave lower, which makes the 120-140hz to 30-45hz.
I came to the realization of how mass affects bass sound when I worked on servo subs and Linkwitz Tranform based subs, where frequency response can always be manipulated (or equalized) to be "almost" the same before and after the change. I wouldn't have any bias the moving mass should have been small or large to start with. And yes I can hear the difference. Here I merely offer what I think how the difference is related to mass.
Brian Ding
Rythmik Audio
Brian
Brian,
It can make a difference. But we're now talking case by case effects; are there exceptions? Yes! The point to take home is that mass changes can increase OR decrease efficiency, depending upon the bandwidth and application you're looking at. It's not an "always hurts" kind of thing.
Just like EQ with LTs - you can have too much gain. On paper, it should work; however, because of the increased average power to the driver, and the increase in basic DCR from heating (and thus Qes and Qts increases) means the LT alignment changes. So you end up with a varying set of alignments. And when "wedging" extreme changes in Qtc/Fb you can get much more resulting final response drift than you would have from just the driver on its own.
Dan Wiggins
Adire Audio
It can make a difference. But we're now talking case by case effects; are there exceptions? Yes! The point to take home is that mass changes can increase OR decrease efficiency, depending upon the bandwidth and application you're looking at. It's not an "always hurts" kind of thing.
Just like EQ with LTs - you can have too much gain. On paper, it should work; however, because of the increased average power to the driver, and the increase in basic DCR from heating (and thus Qes and Qts increases) means the LT alignment changes. So you end up with a varying set of alignments. And when "wedging" extreme changes in Qtc/Fb you can get much more resulting final response drift than you would have from just the driver on its own.
Dan Wiggins
Adire Audio
DanWiggins said:
That is what I meant as a correlation. I never say it is a direct cause. An analogy is on the research groups that looked into the correlation between cholesterol level and heart problem. If they had only looked at samples with cholesterol below 200 (very weak correlation), they would have arrived at a very different conclusion as compared to if they had looked at samples with cholesterol above 300 (very strong correlation). Can we still argue the correlation between cholesterol and heart problem is case by case given what we know today?
Brian Ding
Rythmik Audio
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