Now, all of us agree that there is no error in Dr. Fourier's Theorem.
Never the less, it is indisputable that some woofers are "faster" or "tighter" than others despite the flatness of the frequency response within the passband of "slower" subs. Anyone who has heard a servo (motional feedback) woofer has heard the magic of tight bass.
So there is something subs are doing (or adding or failing to do or failing to not do) that makes them untight or slow. Maybe you'd use that deceptively mild euphemism "group delay"?
Is it mass corner, force-to-weight ratio, or just mass? What are the best ways to display the "fast" parameter?
For sure, today's half-pound* cone assemblies wound with #14 wire can't be very fast.
Ben
* .230 kg
Never the less, it is indisputable that some woofers are "faster" or "tighter" than others despite the flatness of the frequency response within the passband of "slower" subs. Anyone who has heard a servo (motional feedback) woofer has heard the magic of tight bass.
So there is something subs are doing (or adding or failing to do or failing to not do) that makes them untight or slow. Maybe you'd use that deceptively mild euphemism "group delay"?
Is it mass corner, force-to-weight ratio, or just mass? What are the best ways to display the "fast" parameter?
For sure, today's half-pound* cone assemblies wound with #14 wire can't be very fast.
Ben
* .230 kg
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Again, you don't understand how drivers work. Did you bother to read the linked Adire Woofer Speed article from post 19? Of course not, that would take time that could be better spent talking about how great motional feedback is and how terrible moving coil drivers are.
They do the math and this is the conclusion -
... the change in acceleration of a driver - how fast it can change position - is strictly a function of the current through the driver. In fact, if you could make the current change infinitely fast, then the driver would accelerate infinitely fast, and we'd have infinite transients - zero time to change between states. Infinite frequency response.
And this makes sense. Even if you take the world's biggest baddest heavy weight cone moving coil driver and put a 1 (or even 10) khz signal into it, it's going to play back that signal.
HOW COULD IT POSSIBLY DO THAT IF IT'S SO HEAVY AND SLOW? If it's slow wouldn't it play less than 1000 cycles if you gave it a 1 khz signal? That's what slow means, right? That it can't keep up?
It's because cone weight has nothing to do with anything.
Furthermore, fast, slow, tight, flabby, when used in this way are NOT scientific terms, and using them points to the fact that you don't understand what's really going on.
The article goes on to say that INDUCTANCE can cause a lag in the current (leading to less than perfect transient response) but it's a short delay.
Then there's time smear, which can be a cause of what you call "slow" drivers. Time issues can come from the driver itself (high qts) and can come from resonances, but unless fairly high in frequency and fairly long in delay, this smearing won't be audible, especially in subwoofers where the frequencies played are subject to copious amount of room induced ringing and resonances.
And then we come back to frequency response. As I've told you countless times, most of what we hear (especially at subwoofer frequencies) is frequency response. If you don't have a flat(ish) frequency response and you have big bumps in response at low frequencies the sound is often described as slow by people that don't know what is actually causing the problem. For audiophiles the frequency response usually has to be a lot leaner than flat as little or no low bass is what they perceive as fast.
So to sum it up - you didn't do the required reading. Moving mass has nothing to do with speed, speed is a result of current. Inductance can cause a very slight delay in current, high qts and enclosure resonances can introduce a small amount of time smear (BTW group delay is not a euphemism, it's a very real and measurable phenomenon that you likely don't understand), and frequency response is not surprisingly very important.
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How so?
"Fast" and "tight" have literally no quantifiable meaning.
How then can you say it's "indisputable"? Empty rhetoric. At any rate it, it sounds like you passed over the Adire article entirely before posting.
This just got even funnier.
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The Adire Audio write-up is interesting. But people with education or any research experience (which may not include all others posting here) are cautious about the pronouncements of manufacturers of loudspeakers on their websites about loudspeakers, eh. Um, even more so when they went out of business a decade ago.
The write-up offered some routine conclusions:
1. force and mass determine acceleration. Duh.
2. if you experimentally add a large inductance* in series with your woofer, you will lose a lot of high frequencies. Duh.
3. if you add 25 grams to your cone, you observe various changes but, for that driver and that added weight, these changes are hard to interpret.
Ben
* .47 mH, which by the back of my old envelope and stubby pencil, seems to be around a big 9 Ohms at 3kHz**
** only kidding; an old man like me can do that stuff with mental arithmetic any day of the week
The write-up offered some routine conclusions:
1. force and mass determine acceleration. Duh.
2. if you experimentally add a large inductance* in series with your woofer, you will lose a lot of high frequencies. Duh.
3. if you add 25 grams to your cone, you observe various changes but, for that driver and that added weight, these changes are hard to interpret.
Ben
* .47 mH, which by the back of my old envelope and stubby pencil, seems to be around a big 9 Ohms at 3kHz**
** only kidding; an old man like me can do that stuff with mental arithmetic any day of the week
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While I would normally agree that retailer websites are mainly about marketing and not to be trusted let's look at the context here.
Adire produced higher than average excursion and higher than average power handling drivers for the time period they were in business. Higher than average excursion and power handling necessarily comes with higher than average inductance as the two are somewhat linked (larger, longer coils = higher inductance).
So if Adire's products were necessarily higher than average inductance why would they present a paper saying you should avoid high inductance? Maybe because their thesis has merit. Customers could choose drivers with lower excursion and power handling potential which would also have lower inductance and that would not be good for Adire's business, so in this context it does not appear that this paper is driven by marketing.
The fact that Adire went out of business has nothing to do with the technical merit of this paper. Maybe they were just bad at business.
The part you probably aren't aware of (since you questioned it outright a couple of posts back) is that in the context of moving coil drivers there is plenty of force to move the mass as fast as it needs to go. The paper asserts that it's the time factor in the changing current that is the problem, not the mass.
This was only mentioned in passing right at the very end of the paper. Yeah, it's pretty obvious as that's what inductors do.
The paper's assertion about the impulse response measurements is this:
You can clearly see that the raw and mass loaded transient peaks - first negative and first positive peaks - occur at the same time. The inductively loaded (green) peaks are definitely delayed in time.
In that zoomed in impulse response measurement it does appear to be quite clear that this statement is true and that is the point of the entire paper. If you want to argue that point specifically you are free to do so, but preferably on a scientific basis. You can't just say "Nuh uh, mass is slow and motional feedback is fast.". That's not an argument to the information in the paper.
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wasnt this the reason for the development of, and subsequent patent issued for the XBL motor design? a design, if i'm not mistaken, that is still leased for production.
Right.
Their patent (Dan Higgins?) advocated longish gaps and shortish coils, along with very light paper cones, at least by the usual yucky car-audio approach today aimed at looney-tunes loudness levels.
Funny, looks like they were aiming for fast woofers*. Must be great drivers, at least the home music 12-inch unit, if not the car-audio 15-inch unit. Kind of like my great Stephens woofer or JBLs of yesteryear.
Ben
* very light cones, eh. Maybe they thought low mass does matter?
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Wiggins, Dan Wiggins. used to contribute regularly in the early 2000s on DIY forums. kind of where these little researches and such still hosted on the adire page come from.
oddly enough, the XBL motor designs were initially marketed at the "looney tunes loudness levels" folks, enter the adire audio brahma drivers. which if memory serves, only thing that came close to it at that time via "DIY" oriented companies was the Blueprint drivers... and if i recall, the brahma eeked out the excursion edge b/c of the motor design. though this could be wrong.
http://www.adireaudio.com/Files/XBL2ExecSummary.pdf
page 3 covers the goals in plain speak.
I'm looking at the Adire Tempest white paper right now. I believe the tempest was an xbl driver.
It's a 15 inch driver and it's got 195 g MMS. That's not particularly low.
It's got 2.9 mh Le and 3.5 ohm Re. That's an almost 1:1 ratio which is not considered to be low at all.
There are drivers in the same market space and time that had much lower MMS and much lower Le/Re ratio. They might not have had as much xmax or power handling but that's the natural tradeoff.
So regardless of what the patent says, Adire did not achieve anything remarkable in the field of low moving mass or low normalized inductance.
Wiggins did not find a way to circumvent physics, if you want high power handling and high excursion capability it's going to raise inductance no matter what you do.
By the way, the point of xbl was to increase linear Bl, it didn't have anything to do with inductance or mass. Today's long excursion drivers are capable of huge excursion but don't fare too well in klippel tests in the linear (low distortion) inductance and suspension categories. This is why it's common for companies that produce this type of driver to specify xmax as Bl performance alone while completely ignoring the glaring issues with inductance and suspension linearity.
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I don't know their speakers up close, but you sound perceptive about them.
My interest is improving speakers and HiFi gear, not dim-witted sim-soaked carpentry to produce 6th-order band-pass dreams. So the coil patent of Wiggins seemed pretty interesting to me as a good way forward.
Now... I think what they've done - just guessing - is create a trick weave for the winding that lets the magnetic force stay constant over longer distances than prior-art plain uniform weaves. Big improvements in distortion over the full range but no real improvement in max throw. Straightforward modelling, but a good move. (How come all manufacturers of Rice-Kellogg drivers don't figure that out?????)
So for marketing purposes they could say "louder" but in fact, they meant more linear further, as their write-up shows. Maybe being real engineers, they (like Paul Klipsch) never wanted to over-do things like magnet size, not without good engineering reason*. So their drivers do not seem to be too efficient.
BTW, for the innocent among us, the speaker tested in the "fast woofer" write-up was some 6.5-inch jobby that Klippel provided stats for.
Ben
* "good engineering reason" does not often lead to "really great" devices, like Buick versus Lotus.
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You have to understand how things work before you can start improving them. The sheer amount of misguided hubris in these statements is staggering.
And you managed to get a completely off topic swipe at sims in there too, good for you. While you are busy dreaming about improving things you don't understand and don't even like (even though all your subwoofers have been moving coil drivers with no motional feedback, not to mention some of your "hifi" items are bad design even for their 50s time period), some of us are creating real life high gain devices which perform as designed, not as failed 6th order bandpass dreams. You've seen measurements of my tapped horn as recently as last week, for example.
Coils are wound, not woven.
There was a real world improvement in max usable throw with xbl.
But just because the coil topology allowed Bl to remain more linear for a few more mm doesn't mean they were able to keep inductance under control or improve on suspension characteristics so there is still distortion at high excursion, just less distortion, and the distortion present is not due to Bl nonlinearity until very high excursion. There are drivers with 36 mm published xmax which is based solely on Bl linearity. When tested on klippel the Le test failed at just 20 mm. Le nonlinearity causes distortion too, although many people would like to ignore that fact.
Just a little bit of research would go a long way, Ben.
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Adire was Dan Wiggins and David Hyre, FWIW. I seem to recall the original group buy for the Shiva drivers that put the predecessor, Avatar, on the map. I think they ordered a pallet or so of drivers from Eminence, at one point attaching the purchase order to a mail to the "Bass List" that revealed their "per piece" cost at that volume of something like $38 each.
Simulators
@ bentoronto
Do you actually realise that ALL manufactures of BUILT loudspeaker cabinets use Simulators to design them ? They also use Simulators to design the Xovers for them ! They have been doing this for decades !
So for you to be constantly dissing Simulators is crazy !
@ bentoronto
Do you actually realise that ALL manufactures of BUILT loudspeaker cabinets use Simulators to design them ? They also use Simulators to design the Xovers for them ! They have been doing this for decades !
So for you to be constantly dissing Simulators is crazy !
Ron - I don't remember the inadvertent (?) publication of OEM pricing, but certainly do remember using the Shiva (moved a lot of air that one did) and reading about couple of their smaller drivers. The old Avatar site was a lot of fun, and had some interesting aesthetics in their enclosure designs.
@ bentoronto
Do you actually realise that ALL manufactures of BUILT loudspeaker cabinets use Simulators to design them ? They also use Simulators to design the Xovers for them ! They have been doing this for decades !
So for you to be constantly dissing Simulators is crazy !
Those who have passed Grade 4 Reading class, would have understood that my comment related to modelling the coil weave in relation to the magnet structure in order to achieve constant force over the longest throw feasible*. Quite a lunch of complicated math there.
Is that covered in models from Olson, Beranek, Thiele, or Small? No. (But I bet Olson considered it 75 years ago.)
Did Wiggins get a patent for modelling it and figuring the correction... and is offering rights for sale? Yes.
Is that correction widely used in drivers today? I don't know. Do you know which?
Ben
* Dan Wiggins also was addressing the problem of long throws in narrow gaps without the necessity of a second spider. Spider count in McBean?
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I do not understand where that logic is coming from...
When the woofer is small, in order to produce the same spl as big woofer, it has to move significantly more with membrane, which is not easy, as it moves against the resistance of surround and the spider.
When big woofer with large surface needs to create the same spl, it barely needs to move the membrane, hence it theoretically should achieve it much sooner.
That's what my logic would dictate. Complete opposite.
In the reality there is no such thing as "fast" or "slow" bass. It's just that each subwoofer will have slightly different response, therefore it will sound differently. Not necessarily faster or slower. If two subwoofers, one with small woofer and one with big woofer, will have absolutely the same fr response, they will both sound the same (assuming reasonable spl not pushed beyond the limits...).
LOL, how many times do you need to see WIGGINS before you stop saying Higgins? And you talk about grade 4 reading level ...
I'm not sure you understand what Wiggins was doing with xbl at all, which is not surprising since you don't do the required research and don't even know the guy's name. It's not a correction, it's a different coil layout, and it's not that dissimilar to other things that came before it. Did he get a patent? Sure, you can patent just about anything regardless of whether it works or if it's a unique idea. Patent office is staffed by useless idiots.
Xbl is licensed to a bunch of different manufacturers, although I'm not sure why you are asking about that.
Also I'm completely sure that you don't understand what simulators are for. Why would a spider count in a simulator?
Simulators are NOT SUPPOSED TO BE an all knowing all powerful force that can predict you exact in room frequency response, and all other metrics.
You CLEARLY don't understand that, as you pick apart the little things that simulators don't do on a regular basis and completely ignore the things they can do with freakish accuracy when used properly.
Most of us know very well what simulators do and don't do and we can fill in the blanks for the things the simulator doesn't account for.
If you want to know the effect of the spider check the klippel testing. And use that information in conjunction with the information from a simulator to predict some useful information.
Your quaint method of design which involves nothing but pure guesswork along with some (sometimes completely incorrect) assumptions of "good design practice" is a viable alternative but you can be sure that people that use simulators to their full advantage often know what they are doing and can get a lot better results than you can.
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