noah katz said:
Generally incorrect (though humidity levels are a factor with low mass driver dampening). (For more info. look to impeadance transfer.)
Additionally, understand though that, with the exception of exotic drivers (i.e. lighter than air plasma's), the driver's mass for a given sd will be greater than surronding air. (even ribbon's and peizo's are this way).
(btw, don't be discourged by this - its a pretty common belief.)
I was not enamoured by ribbons as I wrote higher in the thread. Maybe because I always listened to them in commercial speakers that they were trying to highlight them. But today when really comparing in a design very well controlled by my friend and me, knowing the ins and outs of its developement, I saw that there is distinct musical merit in ribbons. I am building a smaller 16 ohm 2 way with 2xHM130C0 and worse of bunch in Zaph's tests, the YAG20 planar. If it will still outperform many domes....then we have to see what is really going on with test methods needed. It reminds me a lot the ss vs vacum debate at this point. The most mundane ss measures better than megabuck vacum, but tubes play better music.
Scott,
"Generally incorrect "
Could you please elaborate?
Why then is it that materials that ring when in thick form do not when very thin?
Do you believe that ribbons have a significant degree of electromagnetic damping? I was under the impression that they did not because of the large air gap and consequent low field strength.
Thanks
"Generally incorrect "
Could you please elaborate?
Why then is it that materials that ring when in thick form do not when very thin?
Do you believe that ribbons have a significant degree of electromagnetic damping? I was under the impression that they did not because of the large air gap and consequent low field strength.
Thanks
ShinOBIWAN said:
I'm not going to say necessarily that some were better than others
I think efficency confuses people's ears sometimes... and masks flaws within the sound... not to say there aren't some great low distortion high efficency speakers
what I would say though is that I do enjoy ribbons... but I enjoy domes generally just as much (if the dome isn't an inefficent little bugger)
none of the results surprised me really... I never imagined that any ribbon would be particularly low distortion in comparison to well made domes
Of course, technically bass IS fast, and the lower the frequency the faster it is! 🙂 No poke at you, just a general observation...ShinOBIWAN said:
I'm a DJ with my hand on the RPM stick or maybe I playback all cd's at 48Khz?
Fast bass does exist but only a few have heard it. They are the chosen ones. 😀
SPL is proportional to acceleration - constant acceleration for a given Sd yields flat SPL versus frequency. Which then implies that the velocity must double for every dropping of an octave in frequency (and hence the oft-cited quadrupling in excursion for every dropping of an octave).
So, physically, the lower and louder a given diameter driver plays, the faster it must play - it's velocity simply must increase...🙂
My favorite little physics thing to tweak those who talk about tweeters moving so much faster than woofers...😉 A 1" dome tweeter at 3 kHz typically has a lower maximum velocity than a 6.5" woofer reproducing the same SPL at 45 Hz.
Note what that does to those who rave on about low mass being critical for speed - the Mms of a typical 6.5" woofer is typically 60-100 times that of a 1" tweeter. Yet it simply must have a higher speed to work properly.
Dan Wiggins
Adire Audio®
noah katz said:
It would take a rather l-o-n-g elaboration.. and thats why I said look to impeadance transfer. Consider this though, what happens when you cup your hands to your mouth when you yell out to someone? ..Doing so increases the air pressure (density of air) around your mouth - do you do this to dampen your voice/vocal cords?
As to materials science in driver design look to propagation speed, internal loss, and modulus rigidity. (looking at the thickness of a material is a bad idea.. heck, even looking at density alone is bad idea.) again, sorry, but such a seemingly simple question is NOT simple.
For the question on ribbons and dampening:
Yes for a given mass and sd, ribbons are quite well dampened magnetically. (ever see the raw freq. response of a good ribbon vs. a good dome (i.e. not the averaged response)? Ribbons are usually F A R superior/"smoother".) More importantly however is the NATURE of that dampening. Internal loss (mechanical driver dampening) = a loss of signal information (but it also can = a loss of driver created distortion, so its a give and take thing). Traditional pure ribbons have very low internal loss levels, while sometimes having higher than normal driver related distortion - so while they "add" to a signal, they aren't "taking away" nearly as much as a conventional driver.
Additionally, I've mentioned this several times in various other threads, but harmonic distortion (particularly when related to reproduced direct sound i.e. a singer, or an acoustic instrument), is not nearly as detrimental to sound as most people would have you believe, NOR is the subjective quality of a particular harmonic (as reproduced by the driver) what many would ascribe to. For instance Zaph/John specifically concludes that the subjective descriptors of a pure ribbon's "air" or "shimmer" is related to driver distortion. I have NEVER heard this effect from the driver's distortion. I have heard it from comb filtering however (particularly from axial room reflection interactions - which are quasi-natural with regard to reproduced music).
Finally, total driver dampening (the summed effect of electrical and mechanical dampening) really hasn't been explored much. I find that it makes a BIG difference depending on the freq.. I wouldn't hesitate to say that most systems are W A Y over dampened, particularly higher in freq.. A good ribbon tweeter can really high-light this effect by simply switching between a very low output impeadance amplifier driving the ribbon and a matching (or slightly higher) output impeadance amplifier. (..the first sounds artificial and extremely "focused"/"pin-point imaging"), the latter sounds much more natural while providing a more realistic "image size" and "image palpability"/"image density".)
DanWiggins said:
oh lordy, not this again..
Dan, I believe that NO ONE (or it almost seems that way) but you references the description of bass "speed" in this fashion. Sure, you are fundamentally correct, but you know quite well that when others say "bass speed" that they are not describing what you have just stated. To "jump-in" with this information while not providing a caveat just serves to muddle communication. (..as bad as it is on the non-technically proficient english "speaker", imagin how hard it is on those who can barely communicate in english?.. of course the same could be said about my spelling.. 😀 )
DanWiggins said:
'fast' bass for me is a function of the room, driver distortion and overall group delay characteristics of the system. Fast bass isn't some sort of myth but could probably better be described as clean bass which leads a tendancy to sound more instantaneous and lighter with better dynamics hence I call it quicker than the boom fest that can be called bass.
I think when most folks say fast bass they aren't infering that the laws of physics were suddenly bent by a miraculous driver but rather the subjective feeling is one of a more pacey sound.
Maybe "fast bass" could better be represented with the step response? ie how fast the driver returns to a non excited state after a signal.....
Just another thing about measurements compared to playing music, it has long been my feeling that measurements test very specific things, whereas a piece of music is very complex, with lots of different sounds and harmonics (yes instruments produce harmonics too) that the driver needs to reproduce instantaneously. Think about it, when you are listening to live (acoustic) music there are multiple different sound sources, we are expecting one little driver to do the work of ALL of those different instruments at the same time
So one driver under particular synthetic tests may look better than another, but it may subjectively sound worse in a real world test than a driver that didn't perform as well, because the apparently worse performing driver is better able to handle real music.
Tony.
Just another thing about measurements compared to playing music, it has long been my feeling that measurements test very specific things, whereas a piece of music is very complex, with lots of different sounds and harmonics (yes instruments produce harmonics too) that the driver needs to reproduce instantaneously. Think about it, when you are listening to live (acoustic) music there are multiple different sound sources, we are expecting one little driver to do the work of ALL of those different instruments at the same time
So one driver under particular synthetic tests may look better than another, but it may subjectively sound worse in a real world test than a driver that didn't perform as well, because the apparently worse performing driver is better able to handle real music.
Tony.
salas said:
Looking at the data, I'd say that there's a parallel to drawn between the ss vs. tube and the dome vs. ribbon argument. Take a look at this extract from Hugh Dean who is the man behind the quite wonderful AKSA amps:
The points of interest relate to the relatively high H2 and H3 distortion components of tube based amps yet higher order distortion is vanishingly low, this is in direct contrast to most SS designs whereby H2 and H3 remain almost immeasurably low and the higher order harmonics are, in direct comparison to a tube design, higher.
Hugh Dean eventually cites musicality as being the greater absence of higher order harmonics which introduce audible artifacts in terms of grains of hardness of sound.
One of a few drivers where its possible to both have your cake and eat it is the Scanspeak R2904-7000:-
Tested at 2.83v/1m = 94.3dB SPL:
2nd order: From 3k to 7k is 0.2-0.3% and above 7 k, 0.1%.
3rd order: At 500 Hz is 0.3%. At 1K its around 0.1%. At 2.5Khz its 0.1% and above 2.5kHz its below 0.1%.
5th order: From 500Hz to 20 kHz its under 0.01% but with a small peak at 800hz which equals 0.03%
All forms of distortion, especially 3rd order and higher, are very low. The best of both worlds? I think so from my experience with this driver, although it isn't strictly a dome 😉
Besides distortion there's a plenty of other important aspects to performance such as waterfall or energy-time-frequency plots, IM distortion, impulse response and amplitude.
Also:
Its common sense but in all the discussion, the focus as a whole toward one driver does not make a loudspeaker system, the rest of the components are just as important of course.
Its common sense but in all the discussion, the focus as a whole toward one driver does not make a loudspeaker system, the rest of the components are just as important of course.
wintermute said:
Actually an impulse response is what you want to look at, particularly the leading edge decay of the pulse (..but the rise is almost as important). Really though, even that is a poor measurement when compared to the complexity of music (i.e. there isn't a measurement that convey's the driver's subjective sense of "speed").
Note: this applies equally as well to other freq.s (not just bass).
Additional Note: A CSD plot (cumulative spectral decay or waterfall plot) is a 3D representation of an impluse response. While they are fantastic for looking at decay (and its nature relative to freq.), it isn't very good for determining the subjective sense of "speed" because the initial "rise" really isn't graphically represented in the time domain. Remember, when looking for "speed" you want to see not only how long it takes a signal to decay, but also how long it takes to re-react (or "rise" again) - which can be guessed at by looking at the time required to "rise" (and the nature of the "rise") on the impulse response.
"As to materials science in driver design look to propagation speed, internal loss, and modulus rigidity. (looking at the thickness of a material is a bad idea.. heck, even looking at density alone is bad idea.) again, sorry, but such a seemingly simple question is NOT simple."
Propagation speed, modulus *of* rigidity (shear modulus), elastic (which is I suspect you meant) are irrelevant to the discussion.
Internal loss factor is as well, since for aluminum it's a few thousandths of a % (don't have my vibrations book here with the exact number).
Impedance matching *is* relevant.
Since you haven't said anything substantive to refute it, I still contend that the layers of air in contact with a ribbon that become part of the effective moving mass, have mass on the order of the diaphragm itself, and thus the impedance matching is high enough to effect damping by the air.
"(looking at the thickness of a material is a bad idea.. heck, even looking at density alone is bad idea.) "
Why is that? It's relevant to the discussion, per the above.
Propagation speed, modulus *of* rigidity (shear modulus), elastic (which is I suspect you meant) are irrelevant to the discussion.
Internal loss factor is as well, since for aluminum it's a few thousandths of a % (don't have my vibrations book here with the exact number).
Impedance matching *is* relevant.
Since you haven't said anything substantive to refute it, I still contend that the layers of air in contact with a ribbon that become part of the effective moving mass, have mass on the order of the diaphragm itself, and thus the impedance matching is high enough to effect damping by the air.
"(looking at the thickness of a material is a bad idea.. heck, even looking at density alone is bad idea.) "
Why is that? It's relevant to the discussion, per the above.
Good thoughts... However, a driver tends to "return to rest" as fast as it moves from rest, since it's actively driven to such a state by the amplifier. There's always a force acting in the motor, because there's a current flowing in the voice coil.wintermute said:
I'd say that what most audiophiles consider "fast bass" is actually a lack of bass, similar to what ShinobiWAN was hinting at. Eliminate the deeper frequencies, and room modes aren't as excited (which are NOT actively driven to rest like the driver), the music tends to sound "lighter" and thus quicker, and you tend to get richer harmonics when pushing a less-deep-performing system hard with low tones.
Just today I was discussing amplifier soundstaging with a recording engineer/musician here in Seattle. He likes his transformered-output McIntosh MC2100 amp when reproducing music because the subtle crosstalk it has presents what he feels is a wider, more involving soundstage. Is it more accurate than a set of quality monoblocks? In terms of measurements, absolutely not! However, in terms of perception, he believes it usually is.
Likewise what is "bass" and what is "fast" or "slow". I've yet to hear an organ - or even a 6 string low A tuned bass - that had that lowest note start and stop quickly. True deep bass is inherently slow, being long to start and long to stop! Of course, it takes 50 msec for just one cycle of a 20 Hz cycle to complete...🙂
Where I think a lot of the crispness of bass that audiophiles seek comes from is midbass - make it punchy in the 60-150 Hz range. Of course, the easiest way to do that is eliminate the stuff below that range...
Oh, and Scott? Speed is just the scalar of velocity...😀 I know, I was just tweeking some noses,...
Dan Wiggins
Adire Audio®
I'm not an ME like you, but I think you're pretty right on here... The mass of air is about 1.3g/L. For a ribbon like the R1, the moving mass is around 0.008g, and the Sd is ~60 cm^2. Assuming the ribbon can move 1mm forward, the weight of the displaced air is around 0.0078g, so it's nearly equal to the mass of the ribbon itself...noah katz said:
Unless my conversions are all screwed up. Like I said, I'm not an mechanical engineer! 😀
Dan Wiggins
Adire Audio®
Since the Bohlender Graebener Neo3 PDR won, I wonder what it would perform in front of the Seas 27TDFC and 27TBFC/G.
John please? Hehehe!
That would be best vs best.
John please? Hehehe!
That would be best vs best.
noah katz said:
Well then lets take the questions in order. Obviously if don't like the answer then don't take my word for it - research it yourself, I'll not waste more of my time on this. While my answers below specifically reference your questions above, note that the overall answer effectivly is: "yes air dampens the driver's diaphram adding mass, but the effective result is simply a loss in overall sound pressure level (spl) which isn't meaningfull in a driver comparison context except for comparing driver effeciency".
A. No they are not - at least with reference to a loudspeaker driver's diaphram where the increase of both typically causes a decrease in internal loss. However, depending on the material, the loss/gain may not be proportional (i.e. some materials are inherently better than others because of their relationship between elasticity and inertia).
B. Again, no. A change of internal loss of even .001 can be audibly significant in a driver, especially as a driver's mass decreases (typical of higher freq. drivers) .
C. No comment.
D. Will an increase in mass on the driver neccesarily increase damping? Generally yes (unless there is an off-set in the impeadance transfer), but what is the nature of the damping on the driver? Typically a decrease in spl (amplitude) while extending the driver's bandwidth lower in freq.. In otherwords it isn't just the driver's decay thats experiencing a loss of amplitude, but also its "rise" - and the decrease is fairly proportional between the two. This is NOT the case with internal loss of the driver's diaphram which primarily targets driver decay (conversly flexural rigidity and speed propagation targets "rise".. see answer "A" above).
E. Moot point on an abstract position, see answer "D" above.
Dan,
Thanks for doing the calculations I was too lazy to 🙂
Scott,
"yes air dampens the driver's diaphram adding mass, but the effective result is simply a loss in overall sound pressure level"
Well, yes, that's what damping the output means.
And it increases efficiency by a better impedance match, same as a horn.
A. Air damping would occur even if the material were rigid (infinitely stiff). Propagation of transverse waves would be relevant if we were talking about internal damping, but we're not.
B. Why are you even bringing up internal material losses, anyway?
D. "Will an increase in mass on the driver neccesarily increase damping? Generally yes"
You rest my case.
I don't get the rest of what you said. All vibrations move the material in both directions.
A. No they are not - at least with reference to a loudspeaker driver's diaphram where the increase of both typically causes a decrease in internal loss. However, depending on the material, the loss/gain may not be proportional (i.e. some materials are inherently better than others because of their relationship between elasticity and inertia).
B. Again, no. A change of internal loss of even .001 can be audibly significant in a driver, especially as a driver's mass decreases (typical of higher freq. drivers) .
D. Will an increase in mass on the driver neccesarily increase damping? Generally yes (unless there is an off-set in the impeadance transfer), but what is the nature of the damping on the driver? Typically a decrease in spl (amplitude) while extending the driver's bandwidth lower in freq.. In otherwords it isn't just the driver's decay thats experiencing a loss of amplitude, but also its "rise" - and the decrease is fairly proportional between the two. This is NOT the case with internal loss of the driver's diaphram which primarily targets driver decay (conversly flexural rigidity and speed propagation targets "rise".. see answer "A" above).
Thanks for doing the calculations I was too lazy to 🙂
Scott,
"yes air dampens the driver's diaphram adding mass, but the effective result is simply a loss in overall sound pressure level"
Well, yes, that's what damping the output means.
And it increases efficiency by a better impedance match, same as a horn.
A. Air damping would occur even if the material were rigid (infinitely stiff). Propagation of transverse waves would be relevant if we were talking about internal damping, but we're not.
B. Why are you even bringing up internal material losses, anyway?
D. "Will an increase in mass on the driver neccesarily increase damping? Generally yes"
You rest my case.
I don't get the rest of what you said. All vibrations move the material in both directions.
A. No they are not - at least with reference to a loudspeaker driver's diaphram where the increase of both typically causes a decrease in internal loss. However, depending on the material, the loss/gain may not be proportional (i.e. some materials are inherently better than others because of their relationship between elasticity and inertia).
B. Again, no. A change of internal loss of even .001 can be audibly significant in a driver, especially as a driver's mass decreases (typical of higher freq. drivers) .
D. Will an increase in mass on the driver neccesarily increase damping? Generally yes (unless there is an off-set in the impeadance transfer), but what is the nature of the damping on the driver? Typically a decrease in spl (amplitude) while extending the driver's bandwidth lower in freq.. In otherwords it isn't just the driver's decay thats experiencing a loss of amplitude, but also its "rise" - and the decrease is fairly proportional between the two. This is NOT the case with internal loss of the driver's diaphram which primarily targets driver decay (conversly flexural rigidity and speed propagation targets "rise".. see answer "A" above).
DanWiggins said:
Hi Dan,
Its not a lack of bass at all. Its balanced bass reproduction. The 20hz-80hz is critical for a realistic sounding system but I do agree that low bass can start the room modes off.
What its essential to do in cases where you have dips and peaks in your response is either experiment with positioning or use DRC/EQ.
You can have a tuneful and pacey bass all the way down to 20hz if you calibrate your system and take care to iron out the frequency response.
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