Lynn Olson said:
All that info is included within each domain. From STEADY STATE we can derive the impulse response hence the CSD. Because it is the identical system.
A precondition is that the systems is linear. That is given with measurements as discussed here. To focus on non linear effects commonly HD and IMD measurements are performed.
All those assertions should be clear to anybody dealing with evaluating loudspeakers. One caveat against CSD is that it confuses the regular guy that hasn't learnt maths on school with the same eagerness with which he is now after audio perfection. No offense, but to - discuss - such basics is a bit boring. No offense. I would like to leave the thread. You could open an other one on that topic of CSD. It isn't related to something beyond ARIEL specifically.
Sincerely
X
John_E_Janowitz said:
This was pulled from rather far back in the thread..
I did take a look at their paper, which figure are you referring to? (Because I don't see inductance lower with both shorting rings vs. the AIC in parallel - which is the way it was designed to be used.)
As for heating - you must also factor in the effects of Back EMF and how it heats the coil. My suspicion is that you are still correct at much higher spl's, but at lower spl's (more common to home use) - I wouldn't be at all surprised if the AIC implementation was superior.
..as for the issue of "slow sound" vs. "fast sound":
.."slow sound" is not a by-product of higher inductance in a woofer to any significant degree. Most filter's are going to "lop-off" the high freq. bandwidth of a woofer anyway.
Mms and "Eff." are generic "tale-tell" signs (like the BL/Mms ratio). It's a user selection guideline that usually works. That a driver's behavior doesn't substantial change with added mass (at least at low spl's) is irrelevant to the user.
Back to the inductance thing again.. That a VC has higher inductance for a given mms is usually a sign of a "FASTER SOUNDING" driver. More linear (pistonic) mass movement, less diaphragm/suspension mass.
Again the BL/Mms ratio is a generic guideline for users. The DVC example doesn't factor in - it's still the same mms regardless of how it's connected. If we want to focus on Inductance and high freq. performance: a *useful* comparison for users would be perhaps the PHL 1040 vs. the 1050. Which one sounds faster? The 1050, despite having more than double the inductance.
For most woofer applications current *is* important with regard to Mms/Bl, but not in respect to inductance.
Here the problem is the rise in driver impedance near fundamental resonance (or its in-box resonance). The "average" impedance remains the same for the woofer - so Mms/Bl by itself is about as useful as the DVC woofer example (..because Mms is constant), or basically only useful overall in this application.
The real key for "fast" low freq. performance is the nature of the impedance change in relation to the design and the overall Bl/Mms performance of the driver.
IF the rise in impedance is broad-band, (say starting at 80 Hz and rapidly rising as freq.s go lower), and high when compared to the average, it actually DEGRADES the subjective impression of "fast" for a given mms. (..this is somewhat typical for higher "q" drivers.) By contrast lower "q" drivers tend to keep near their average impedance lower in freq. until their resonance (where the impedance change is usually higher though effecting less of the lower freq. bandwidth.)
Mechanically the issue here is driver damping. For as long (bandwidth) as the driver is mass controlled by the amplifier, typically the "faster" it sounds. As impedance rises however, the amplifier becomes increasingly less important for driver control, and Back EMF starts to account more and more for driver "control" (which it doesn't do well).
It's a bit different for bass reflex design. There you can largely "skip" the impedance trace of the driver (with regard to fundamental resonance), and instead look to the impedance trace of the vent. The vent is actually placing a compression load on the driver's motion near the driver's (in box) resonance - damping its motion and making it far more "mass controlled" in this region. The real problem with these designs are usually the result of "aligned" systems that don't tune the vent low enough in freq. to be both:
1. far enough removed from the driver's (in box) resonance, and
2. low enough not to be in the fundamental range for most material.
Of course all of this should be included with the look to the average Bl/Mms ratio.
Correct me if I'm wrong folks, but I somehow understand "no brainer" to mean "obviously simple" or "really easy to understand".xpert said:
This seems like a response of a paper coned or soft diaphram driver. Looks like the measurement has some room effect. Tones below 1KHz will have somehwat longer ring that may seem pleasing to some. High frequency transients are probabbly not as detailed
ScottG said:
Correction: that a VC has a higher average impedance for a given mms is usually a sign of a "faster sounding" driver.
Does that mean if a driver with high and low impedance options, the high impendance one would sound faster? (e.g. 16 Ohm vs 8 Ohm )
If so, when using 2 parallel 16 Ohm, I'll get the sense of 'impact' more than double (3dB more efficiency and 'faster'), is that right?
This is new to me. I never use 16 Ohm drivers, maybe it's about time to try one.
CLS said:
All else equal - yes (generally). Designers can make several alterations to the driver to have a 16 Ohm that "looks" identical to an 8 Ohm. In some cases though you end up with 1 watt at 1 meter (decibel) that is in reality up to -3db less.
That "sense of impact" is something different than "speed", though it can accompany this subjective trait. "Impact" has as much (or more) to do with mass as force. More mass, more impact (provided the force is adequate). Impact is also often related to air compression and resonance in sealed designs and resonances in rooms.
However most of the time if you parallel a driver (especially if it's in a common enclosure), it *reduces* the sense of impact vs. that of one driver. (..excursion is half that of a single driver assuming identical drivers and enclosure volume.)
2 parallel 16 ohm drivers *may* sound a little faster (lower excursion) than a single one, BUT they will likely have less impact. On the other hand you net +6 db. +3db double the drivers and +3db for 8 ohms (amplifier dependent).
Basically if you want an increased sense of speed and impact one 8 ohm driver at 95 db will be better than two 16 ohm drivers at 89 db wired in parallel (for a net 95 db). All else equal one 16 Ohm driver at 95db will be better than one 8 Ohm driver at 95db. ..At least I've found this to be the case.
gedlee said:Originally posted by John_E_Janowitz
"If you take a driver and increase cone mass it has no effect on impulse response time."
I had trouble following your comments (maybe I'm "slow"
Actually it is quite true. I've done the tests and many others have as well. It's very repeatable if you wish. You just need mass to physically add to a cone, and an inductor to put in series. I finally found the link to the other paper I was looking for. This was from Adire Audio originally.
http://www.diycable.com/main/pdf/WooferSpeed.pdf
See page 4 of the paper with measurements.
"We measured the impulse response of the driver raw, with 28.5 grams added (more than doubled the moving mass), and with 0.47 mH in series (78% increase in inductance). In other words, we more than doubled the mass, and didn't double the inductance. So the mass - if it really limits transient response (and hence frequency response) should really stand out compared to the inductive changes."
The result is that Mass only changes the magnitude of the impulse response but both positive and negative peaks are unchanged in time.
This is with more than DOUBLING the mass. Only a 78% change to inductance however has a significant effect in changing the time of both positive and negative peaks in the impulse response.
The summary is this:
"Mass isn't the problem - inductance is. So if you want faster transient response, ignore that moving mass parameter that some manufacturers push - look at the inductance! And if they don't list the inductance, ask
yourself why - is there something they don't want to show? Inductance is the key to driver transient response - ask for it when transient response comes up!"
John
Hello everyone,
I don't know why people are so upset using the waterfall presentation of the CSD.
The waterfall due to its perspective mask many important features of the spectral/time content of the impulse response.
The first important masked feature being the pulse attack itself.
You'll see here attached the spectrogram (ARTA call it "sonogram") presentation of the CSD which is IMHO more meaningfull that the waterfall.
The 6 sonograms were obtained using ARTA from my own measurements on 6 competiting loudspeakers during a contest organized by the french forum Haute-Fidelite.net
Discussion in French about those measurements at (with prior inscription)
http://forums.delphiforums.com/HAUTE_FIDELITE/messages?msg=30303.26
Best regards from Paris, France
Jean-Michel Le Cléac'h
I don't know why people are so upset using the waterfall presentation of the CSD.
The waterfall due to its perspective mask many important features of the spectral/time content of the impulse response.
The first important masked feature being the pulse attack itself.
You'll see here attached the spectrogram (ARTA call it "sonogram") presentation of the CSD which is IMHO more meaningfull that the waterfall.
The 6 sonograms were obtained using ARTA from my own measurements on 6 competiting loudspeakers during a contest organized by the french forum Haute-Fidelite.net
Discussion in French about those measurements at (with prior inscription)
http://forums.delphiforums.com/HAUTE_FIDELITE/messages?msg=30303.26
Best regards from Paris, France
Jean-Michel Le Cléac'h
Attachments
Jmmlc said:
Yes - thats what I consider the "stored energy" seen to be released as a resonance is coming from...
My guess is that this part is as important with respect to sonic pattern recognition as is the resonance itself - if it makes sense to distinguish the two parts at all.
But havent found a summary about it yet - and also not for the different forms of decay not being necessarily a mere exponential one at a discret frequency
Michael
Thanks a lot for your reply ScottG
However I'm somewhat confused between the 'speed' and 'impact' things.
IMHO, sense of speed (and also impact) involves at least up to midrange. Say, snaps of strings, hits on drums, bursts of voices.... etc. Those sounds come out with rapidly rise on amplitude, burst out suddenly, thus the sense of 'speed'.
But why does more sense of speed turn out to be less impact?
The sense of impacts should be some kind of function of the mass of driven air and time. More air within less time frame yield bigger impact, am I right?
If so, the less cone travel of double-driver should be averaged out by the double cone area -- same volume of air is driven. So I think it shouldn't be less impact.
In addition, 2 drivers on a baffle would be more directional (at least on one dimension), so the sound wave can be more concentrated or travel to a furthur distance. This also helps in delivering energy to the listener.
Oh well, all above are only in my 'thinking'. In reality, I only have experience in parallel woofers, which work in the range below 160Hz and I don't think there'd be any sense of speed in it.
Right now I'm using single 12" guitar driver as midrange. If 2 paralleled 16 Ohm drivers can be good, I'd really like to try 8" MTM. Same Sd, 2 motors, narrower vertical directivity... should be good.
However I'm somewhat confused between the 'speed' and 'impact' things.
ScottG said:
IMHO, sense of speed (and also impact) involves at least up to midrange. Say, snaps of strings, hits on drums, bursts of voices.... etc. Those sounds come out with rapidly rise on amplitude, burst out suddenly, thus the sense of 'speed'.
But why does more sense of speed turn out to be less impact?
The sense of impacts should be some kind of function of the mass of driven air and time. More air within less time frame yield bigger impact, am I right?
If so, the less cone travel of double-driver should be averaged out by the double cone area -- same volume of air is driven. So I think it shouldn't be less impact.
In addition, 2 drivers on a baffle would be more directional (at least on one dimension), so the sound wave can be more concentrated or travel to a furthur distance. This also helps in delivering energy to the listener.
Oh well, all above are only in my 'thinking'. In reality, I only have experience in parallel woofers, which work in the range below 160Hz and I don't think there'd be any sense of speed in it.
Right now I'm using single 12" guitar driver as midrange. If 2 paralleled 16 Ohm drivers can be good, I'd really like to try 8" MTM. Same Sd, 2 motors, narrower vertical directivity... should be good.
These concepts of speed and impact are rather esoteric. If you try to relate speed and impact (subjective terms) to a system's impulse response what do you look at? Do systems with the same speed/impact have the same impulse? On axis? If not, and there is any correlation between speed/impact and differences in impulse response then it comes down to difference in amplitude and/or phase response, or perhaps directionality, or nonlinearities?
Speed/impact is where reproduced fundamentals and their directly related harmonics arrive at the ear bearing the same amplitude relationships during music time as did the original waveform.
This being where driver/cabinet resonances, crossovers etc. cannot fail to modify resultant reproduction during music time.
This being where driver/cabinet resonances, crossovers etc. cannot fail to modify resultant reproduction during music time.
ScottG said:
This was pulled from rather far back in the thread..
I did take a look at their paper, which figure are you referring to? (Because I don't see inductance lower with both shorting rings vs. the AIC in parallel - which is the way it was designed to be used.)
Note that their paper is written with intent to show what they want it to. It is much more a marketing paper than a paper to evaluate the technology. Take the evaluation of flux modulation. They have figures 5 through 27 all showing flux modulation of a standard motor vs AIC. Yes, AIC does lower flux modulation, but not nearly as much as a solid fixed sleeve on the pole. They don't however show this comparison.
In terms of decreasing distortion the primary benefit is to reduce 2nd harmonic at higher frequencies. Compare Figure 30 (500 type with no shorting ring) to figure Figure 31(500 type with AIC). From 300hz on up, the AIC actually slightly INCREASES the 3rd harmonic (grey line). From 400hz on down AIC does virtually nothing for 2nd or 3rd harmonic. The benefit is a decrease to 2nd harmonic from about 500hz on up.
Now look at Figure 32 with shorting ring under the pole vs Figure 31 with AIC. Look at below 300hz first. The shorting ring has anywhere from a 5-10dB decrease in 2nd harmonic and everywhere below 800hz the shorting ring has lower 3rd harmonic than the AIC. We see similar with figure 33. This is with a shorting ring intentionally not positioned to be fully effective. Had the shorting ring been a full sleeve on the entire pole so it is adjacent to all of the coil at all points of excursion you would see drastically decreased distortion. But their paper wont' show you that either.
See the link posted in response to Earl above. If you'd like, try out the same experiment. You'll get the same results. If we're talking about speed it clearly makes sense to look at the time domain.
We are talking about "speed" and Bl/Mms ratio once again tells nothing. Testing shows that inductance increases the time to both positive and negative peaks. I don't see how this is irrelevant. Again look at the results in the paper. With double the mass, the impulse response occurs at the same time, meaning same speed. With 78% increase in inductance, it is shifted later in time. Clearly this tells which is more critical in terms of "speed".
A larger VC becomes a stronger electromagnet as more power is applied. It is more effective at modulating the flux field. This creates more distortion and longer rise and fall time if you look at the impulse response. Again, diaphragm/suspension mass has NOTHING to do with the speed of a woofer or the sound it can produce.
Clearly you need to take inductance in relation to Re, the same as you have to take BL in relation to RE or it means nothing. To compare motor strength you need to look at BL^2/Re. The PHL 1040 and 1050 are the same driver, just 8ohm and 16ohm. There should be no difference in the way they sound if played at identical levels. Mass is the same, motor strength is the same, and Le to Re relationship is the same. If the same amount of power is applied to both their impulse response will be the same. Neither sounds faster or slower as they are the same driver.
There is no relationship between Mms and BL directly. You need to factor in the DCR by using Bl^2/Re to compare motor strength. Without Re there is nothing to compare as Bl and Mms have no relationship at all.
If I asked which vehicle is faster, a vehicle with 1200HP or one with 100HP but didn't give you any other info it wouldn't mean anything. The 1200HP could be a loaded down garbage truck and the 100HP vehicle could be a Kawasaki Ninja.
Yes, my point with the DVC woofer is again that this Bl/Mms ratio shows nothing. You can change the relationship which you believe is important simply by wiring the coils in series or parallel. This clearly shows that the relationship is meaningless without other factors and never has any meaning.
John
John_E_Janowitz said:
John, I understand now what you mean, but I'd still claim that the impulse response has to change if the cone mass changes. What does not change, and this is your point, is the frequency response above resonance, and hence the early part of the impulse response will not be greatly affected - but it has to change.
Hello John
I never fully understood the Woofer Speed paper for a couple of reasons. First off they add a series inductor that is not part of the voice coil. If that's true you are running the test signals through a lowpass filter. Wouldn't you get delay from that alone?? It certainly going to roll off the top end response. Also because the additional inductance in not in the motor the BL number doesn't change like it would if you have more windings in the gap.
Wouldn't it been better to compare 2 identicle drivers that are 8 and 16 ohms where all the inductance is actually in the voice coil?? Looking at T/S tables for JBL's the 16 ohm drivers all have about twice the LE value that the 8ohm. 4 ohm versions less than that.
Does that mean the the 4 and 8 ohm versions will have better transient response even though the BL are much higher, almost double??
If you take a 4 or 8ohm version of the same driver vs a 16ohm driver do you see the same delay as you do in that paper??
Rob
I never fully understood the Woofer Speed paper for a couple of reasons. First off they add a series inductor that is not part of the voice coil. If that's true you are running the test signals through a lowpass filter. Wouldn't you get delay from that alone?? It certainly going to roll off the top end response. Also because the additional inductance in not in the motor the BL number doesn't change like it would if you have more windings in the gap.
Wouldn't it been better to compare 2 identicle drivers that are 8 and 16 ohms where all the inductance is actually in the voice coil?? Looking at T/S tables for JBL's the 16 ohm drivers all have about twice the LE value that the 8ohm. 4 ohm versions less than that.
Does that mean the the 4 and 8 ohm versions will have better transient response even though the BL are much higher, almost double??
If you take a 4 or 8ohm version of the same driver vs a 16ohm driver do you see the same delay as you do in that paper??
Rob
Robh3606 said:
The VC in a driver is a coil of wire, the same as the inductor put in series. It has the same effect. The amplifier has no way of knowing whether the inductance is all on the VC or a VC in series with the inductor.
If you are changing the amount of windings in the gap, then you are changing Bl as you mention and can no longer do a direct comparison.
Again go back and read my other comments. It isn't the overall Le value that is important. It is Le in relation to Re. Looking at 4, 8, or 16ohm versions of the driver all with the same Le to Re relationship will show almost identical impulse response.
The best way IMO to do this measurement is to take the same driver with and without the shorting ring. Take a TD15M for example. One driver with the copper sleeve and one without the copper sleeve. Matching Re to be within better than 1% tolerance between coils. Matching suspension so Fs is within 1% between both drivers. Check impulse response and you will see that the one without the shorting ring has delayed positive and negative peaks the same as shown in the other paper.
John
gedlee said:
"speed" and "impact" ("punch" and "slam") are subjective descriptive terms - perhaps what you would refer to in loudspeaker design as "black magic". What it is NOT (as suggested by others), is simply the result of inductance reducing the high freq. bandwidth for a driver (or even increasing non-linear distortion at higher freq.s for a driver). Still, it's always argued, and yes - the argument doesn't make any sense (..except perhaps for "full-range" drivers).
People are still trying to understand exactly what is responsible for these descriptions, but as John K has noted - we really haven't progressed very far here:
john k... said:
John_E_Janowitz said:
AIC:
I'll disregard the flux modulation pic.s (..you can't effectively argue you have support for something by saying "look, there isn't a comparison that proves I'm correct!").
As for the AES paper being marketing.. perhaps, but as we can see from their fairly extensive testing - it isn't exactly "all in their favor". So I'll mostly discount that the paper is "cooked".
When going through the very comparisons provided next, remember that virtually all of these examples are driver's pushed well beyond the bounds of general domestic use. (..as I mentioned before, I *think* it's likely that thermal stress is increasing distortion for AIC at freq.s near fundamental resonance when compared to those with "shorting rings". At much lower spl's I *think* that distortion would be better with AIC at lower freq.s as well, as opposed to the best that shorting rings can apply. It is however a guess).
Comparing figure 30 with 31:
The darker gray is 2nd harmonic, the "blue" gray is 3rd harmonic (which is the opposite of what you have stated).
From 300 Hz up AIC very marginally increase 2nd order distortion. The net result is insignificant for 2nd order distortion (either increases or decreases for the entire bandwidth). The only thing that AIC is doing in this example is reducing 3rd order distortion from 400 Hz up (in freq.)
Comparing figure 32 with 31:
3rd order distortion is dramatically higher around 100 Hz for AIC, and dramatically lower around 1kHz. 2nd order distortion is significantly higher around 100Hz and marginally lower around 1kHz. (..At these high input levels I believe that thermal compression is "rearing it's ugliness" for the 100 Hz distortion - giving the "shorting ring" a distinct advantage here.)
Comparing figure 33 with 31:
I agree, similar results with the figure 32 vs. 31 comparison. That the "shorting ring" here is not positioned correctly? That I can't confirm or deny, but I can say that you have not confirmed that it is the case. (..note however that I'm not saying your are incorrect, for all I know its significantly "biased".)
Now I'm not sure in what context you "quoted from me", but I will amend it by saying that:
AIC appears to be superior with respect to reducing inductance.
and,
AIC at very high sp-levels is only superior at lowering 3rd harmonic distortion levels at higher freq.s. It is distinctly inferior to good "shorting ring" implementation at very high sp-levels at lower freq.s. It *may* be that the reason for this inferiority is in part (or even mostly) due to AIC's lack of thermal sinking/cooling for these higher input levels.
In my mind this leaves 2 questions:
1. Can both AIC and Shorting rings be used together? If so will the results be better than either alone or not?
2. Is AIC's inferiority at lower freq.s a thermal problem, and if so - is it as good or better than a good shorting ring implementation at much lower input levels?