I've acquired a woofer from one of those, back in the day, Japanese systems incorporating the superwoofer. It's a 10" driver with a serious mechanical X-max. I've no clue as to the TS parameters. It struck me - these drivers were crammed into very small cabinets.
I modelled a random Eminence 10" driver in a 20l cabinet. The results were awful, f3@80hz, +5db @ 200hz.
What characteristics does a driver require to work in a small cabinet.
I modelled a random Eminence 10" driver in a 20l cabinet. The results were awful, f3@80hz, +5db @ 200hz.
What characteristics does a driver require to work in a small cabinet.
Strong motor, low Fs.
Try modelling a B&C 18" IPAL driver.
Chris
Try modelling a B&C 18" IPAL driver.
Chris
This one from Atohm seems to be designed for small cabinet:
https://www.atohm.com/en/products/drivers-kits/drivers/ld230-cra-08m.html
BL 19.8 N/A
Fs 24Hz
Used in 8,5 liter sealed passive sub from Sun Audio:
https://sunaudio.com/products/atohm-9-passive-subwoofer-pair
https://www.atohm.com/en/products/drivers-kits/drivers/ld230-cra-08m.html
BL 19.8 N/A
Fs 24Hz
Used in 8,5 liter sealed passive sub from Sun Audio:
https://sunaudio.com/products/atohm-9-passive-subwoofer-pair
With or without equalization?
Vented or closed?
Low VAS is usually a good indicator.
Edit: or high qts (and low fs and enough Sd) and you don't even need an enclosure, just an open baffle.
This is what I call a car solution - it's crap. 82dB is 10-15db below the output of a decent 10" woofer. @F10 82dB is nothing special.
It needs no (or less) EQ and may be useful if you don't want to do that.
There was a calculator on mh-audio to show the influence of added diaphragm mass. It only reduces higher frequency sensitivity/efficiency, just as you state, but very low influence at lower end.
Dieser hat bei mir in einem Volumen von ca. 10 Litern ein sehr gutes Ergebnis geliefert. Mehr dazu hier .
Es gibt mindestens ein kommerzielles Produkt mit demselben Treiber.
Es gibt mindestens ein kommerzielles Produkt mit demselben Treiber.
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Oops ... Seems my browser was in translator mode, sorry! I meant to write:
This gave me a very good result in a volume of approx. 10 litres. More about that here .
There is at least one commercial product with the same driver.
This gave me a very good result in a volume of approx. 10 litres. More about that here .
There is at least one commercial product with the same driver.
The Vas is directly dependent on the Sd (cone surface). If the Mms is low, that means the fs will rise a lot in a small enclosure. To counter that, they rise the Mms and at the same time they are stiffening the suspension to keep the high mass in control. Unfortunately, that, more often than not, this results in high losses. You can usually hear that, the subwoofers only really 'wake up' above a certain level. And these mud-pumps usually don't have a good resolution either.
That's correct. If you ever ask a 'car specialist' they will tell you "just buy a bigger amp".
I wish my brain would absorb the different ways super stiff suspension and high moving mass (in car audio drivers) verses high Qes weak motored driver's( of any kind) acts in ‘large’ or small enclosures (without having to simulate it to observe the super underdamped peaks and deep valleys of nothingness in between resonances (s).
is that the result of small signal info(TS parameters) and simulation tools that uses them in their math?
once you get that stiff, heavy thing moving its actually doing much ‘bettter’ between the resonance peaks than portrayed by TS info? Maybe?
is that the result of small signal info(TS parameters) and simulation tools that uses them in their math?
once you get that stiff, heavy thing moving its actually doing much ‘bettter’ between the resonance peaks than portrayed by TS info? Maybe?
You need more mass to get low end extension. With a light mms, the Fb goes too high to have any low end once you start shrinking enclosure size.
You have to keep multiple parameters within a range for it to have a positive effect on the low end without sacrificing high end. Just adding mms by itself to a normal subwoofer with no other changes will yield no benefit. In addition to more mms, you also need more motor force to keep the equilibrium as more motor force lowers Qes. Otherwise it only increases Qtc like it shows in your graph.
My rule of thumb is: for a 10" you need a BL^2/Re of 75+, for a 12", you need 100+, and for a 15" you need 150+. But where mms comes in to play is a ratio of mms to motor force (essentially just the efficiency). Divide your motor force by your mms, and that ratio will be an indicator of your bandwidth. The lower this number, the less efficiency and bandwidth. For subsonic subwoofers that don't need to play more than an octave, this ratio can be between .2 to .3. For audiophile subwoofers that can play 2-3 octaves, this ratio needs to be .3 to .4. And for a very wide bandwidth, .45+. Once you get around .45+ the subwoofer wants to start being more of a woofer and you begin to compromise low end extension.
Vas is also heavily dependent on cms, or the compliance of the suspension. Normal big subwoofers with heavy mms and stiff suspension are not designed for high fidelity small sealed usage; those subs are designed for high power vented enclosures. If we take those big, powerful, and heavy subwoofers and build them with a very soft suspension, they are now spec'd to work very well in small sealed enclosures. The problem is that the market for small sealed enclosure audiophile/hifi subwoofers with good low end extension doesn't really exist yet, but we are on the precipice of companies being interested in offering that. Also, the "resolution" of the "mud pump" is entirely dependent on its non-linear distortion characteristics. A big heavy sub with linear BL/Kms/Le will be as articulate as anything else out there, there is just no getting around the need for a lot of power for it to be used in small airspaces. Power is cheap now, so sensitivity/efficiency in this context is not as important as it was 30+ years ago.
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@ICG I was wondering about different answer. I mean, that answer is in alignment with my knowledge, and except for hardware based EQ, I see no point in adding mass. It's almost pure loss. The misinformations are still spreading like a plague.
@Booger weldz You can simulate extreme cases in the simulator of your choice and get the general understanding on what's up.
@hurrication
In previous posts with graphs, it has been debunked. About same low end output, the lighter cone was just much more sensitive and efficient in the upper range. You can simply EQ that out and be done with it.
The chase for equilibrium of flat voltage response is outdated. No need for that now. Just go for highest motor force, highest displacement volume, and lightest Mms for highest true efficiency and performance. Adding weight and stiffening suspension for other than vital function of the safe piston movement of the cone is a bad approach. Immature, wrong, under the line, stoneage, sinful. 😃🤭
At no point* adding motor force to the woofer causes it to be less subwooferry with less extension. That's an electrical design problem, not a output capabilities issue. Adding more magnetic field and wire cannot cause in grand scheme of things less output. The physics cannot break here. If we benchmark it ad absurdum, we'd come to the conclusuion then, that with no wire and no magnet, we'd get most output. And there is no coeficient in existance that would alter that course of thinking. So no. The more the better, and let's deal with it on the amp side.
I do agree that efficiency and sensitivity is not as important. But exactly because amps and EQs are cheap now, it is shooting oneself inthe leg needlessly by adding unnecessary weight and stiffness.
If the speaker is more efficient, it can be lighter then, it can be powered by lesser amp, and that is cheaper. It bugs me how noone is following that. Most upper class and high end car audio speakers are ridiculously expensive. Anything that would outdo a $500PA speaker in general costs between $700 and $1300. They want money for different things than performance.
Thinking about the rule of thumb, I guess it only works for certain class of speakers. For example strong car audio 15" has mms approaching 400g. PA speaker is about 300g at 18" to keep in the displacement volume ballpark. Now, the lighter cone must travel shorter distance per same volume displaced, also saving on the force to move the cone mass. When less force is required for the same volume displaced, then the motor can be somewhat weaker. Again, money saved on the motor assy.
@Booger weldz You can simulate extreme cases in the simulator of your choice and get the general understanding on what's up.
@hurrication
In previous posts with graphs, it has been debunked. About same low end output, the lighter cone was just much more sensitive and efficient in the upper range. You can simply EQ that out and be done with it.
The chase for equilibrium of flat voltage response is outdated. No need for that now. Just go for highest motor force, highest displacement volume, and lightest Mms for highest true efficiency and performance. Adding weight and stiffening suspension for other than vital function of the safe piston movement of the cone is a bad approach. Immature, wrong, under the line, stoneage, sinful. 😃🤭
At no point* adding motor force to the woofer causes it to be less subwooferry with less extension. That's an electrical design problem, not a output capabilities issue. Adding more magnetic field and wire cannot cause in grand scheme of things less output. The physics cannot break here. If we benchmark it ad absurdum, we'd come to the conclusuion then, that with no wire and no magnet, we'd get most output. And there is no coeficient in existance that would alter that course of thinking. So no. The more the better, and let's deal with it on the amp side.
I do agree that efficiency and sensitivity is not as important. But exactly because amps and EQs are cheap now, it is shooting oneself inthe leg needlessly by adding unnecessary weight and stiffness.
If the speaker is more efficient, it can be lighter then, it can be powered by lesser amp, and that is cheaper. It bugs me how noone is following that. Most upper class and high end car audio speakers are ridiculously expensive. Anything that would outdo a $500PA speaker in general costs between $700 and $1300. They want money for different things than performance.
Thinking about the rule of thumb, I guess it only works for certain class of speakers. For example strong car audio 15" has mms approaching 400g. PA speaker is about 300g at 18" to keep in the displacement volume ballpark. Now, the lighter cone must travel shorter distance per same volume displaced, also saving on the force to move the cone mass. When less force is required for the same volume displaced, then the motor can be somewhat weaker. Again, money saved on the motor assy.
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Hi,
I'm interested about your observations about the 'wake up' phenomenon you mention so fee questions.
I understand from your text that 'wake up' phenomenon relates to suspension and that there are drivers that do have the 'wake up' and those who don't. How do you read this from TS parameters or is it always sometging one must listen for, enclosure related and not just the driver?
Vas is directly related to Cms, suspension compliance, but suspension losses have another parameter Rms and I would guess since they are separate parameters that stiff suspension doesn't necessarily mean high losses?
Manipulating Rms in a box simulator has very little effect on system transfer function. Also manipulating Cms (and Vas, and Qs that change with them) has surprisingly little effect, 50% change in Cms changes transfer function roughly with a dB here and there. So, how the 'wake up' effect can be read from any of this before buying a driver and building a box?
I'm helping a friend to make a system that is good for hifi and for occasional party, so for low and high SPL use and if 'wake up' is real phenomenon I need to not have it in the system.
Thanks!
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Nothing has been debunked. Those graphs by stv are just taking a Dayton sub and adding weight to it without changing anything. What those graphs are doing is decreasing the motor force / mms ratio that I mentioned earlier, which by itself will not increase any low end output. I literally said that doing this exact thing in the sim is not going to get the result of more low end.
The BL^2/Re for that sub he cited is 14.5 from the factory, and a 26.6g mms. Its motor force / mms ratio is .54. His sim with a 50g mms brings this ratio down to .29, and his sim with a 100g mms brings this ratio to .145. Refer to my rules of thumb from earlier to see how those altered sims play in to its performance. My rules of thumb are what loudspeaker engineers use to design speakers.
"Just eq that out" doesn't work if you shrink the enclosure airspace; you lose low end that you can not get back even with more power or EQ.
I never said anything about stiffening the suspension, in fact I spoke against it. You need a compliant suspension to drop the fs of the sub low enough to get a desirable Fb in a small enclosure. The logic of high motor force and lightest mms is 30+ year old mindset and does not yield any low end in small airspaces. It might seem like a bad approach to those who are still stuck in the past, but subwoofer technology has advanced since then. You take a subwoofer like that and put it in a small enclosure, and your Fb is too high to be usable.
Do you know what happens when you increase motor force but keep the mms the same? Sensitivity increases. Are you familiar with Hoffman's law? High sensitivity, low end extension, and small enclosure size: pick two. When you increase the motor force / mms ratio, you increase efficiency/sensitivity. The higher these are, the less low end extension you will have for a subwoofer in a given airspace. This is pretty basic stuff.
This train of thought is fine if you are ignoring airspace. This goes out the window if say you only have 1.25 cubic feet to work with. Stick that 18" in 1.25 cubic feet and it will have zero low end regardless of how much power you put on it. The car audio 15" with more power will have more low end in the same airspace, assuming my rules of thumb that loudspeaker engineers use from above are met.
I will do some simulations on this when I get home to show that I am right and put this to bed once and for all.
@hurrication
Uh oh, Funny, because I believe I held well with not calling your ways old ways or dysfunctional oldschool ways, though I AM guilty of thinking the same way.
No, I think there is some misunderstanding in this. There is relation to these, but not causation. I am coming from little different place.
In pure physics, you want the lighter cone. If it was infinitely stiff and sturdy, you can disregard final Fs, as total output is not reliant on Fs at all. Total output though is reliant on Mms. The more weight the less output, and we don´t want that.
Sure, reality doesn´t want to get there freely, and so in order to make a woofer perform and be sturdy, weight will increase in both soft parts and motor part too. So be it. I am talking about unnecessary weight. There is no reason to add weight except that one that is used to keep the cone and coil mechanically stable. That weight is inevitable and needs to be used.
Regarding stiffening situation, this is again practical issue. You would want servo or magnetic linear motor to drive the cone. But if "arbitrary signal" drives the cone in the nonlinear system, you would develop huge offsets too, making the device unusable. So zero position restoring force is needed, and it needs to be somewhat strong, hence the stiff suspension.
So bacis, that we have a serious argument about that. So maybe not so basic, but one has get off the high horse. I am very open to the situation where we communicate that I am wrong. Yes, teach me and humble me. No shame about it. But at the moment, it doesn´t look like it really.
If I get this right, then that statement of yours is not a true statement. If you add motor force, you will not have less extension. Not with such plain expression. Again. With stronger motor, the motor pushes more Newtons per Watt on the cone, and so at no point you get less bass. That is the issue with old ways and thinking in terms of constant voltage, not power.
I also did say nothing about smaller enclosure. All things same, just motor force. It seems you are manufacturing scenarios I did not suggest, and then clubbing me with these.
I like the practical proposal of the 1.25cu. ft test. This is close to the ad absurdum benchmark. Indeed, let´s do that! Set boundaries, parameters we can agree on, and go. This is great learning opportunity.
Uh oh, Funny, because I believe I held well with not calling your ways old ways or dysfunctional oldschool ways, though I AM guilty of thinking the same way.
No, I think there is some misunderstanding in this. There is relation to these, but not causation. I am coming from little different place.
In pure physics, you want the lighter cone. If it was infinitely stiff and sturdy, you can disregard final Fs, as total output is not reliant on Fs at all. Total output though is reliant on Mms. The more weight the less output, and we don´t want that.
Sure, reality doesn´t want to get there freely, and so in order to make a woofer perform and be sturdy, weight will increase in both soft parts and motor part too. So be it. I am talking about unnecessary weight. There is no reason to add weight except that one that is used to keep the cone and coil mechanically stable. That weight is inevitable and needs to be used.
Regarding stiffening situation, this is again practical issue. You would want servo or magnetic linear motor to drive the cone. But if "arbitrary signal" drives the cone in the nonlinear system, you would develop huge offsets too, making the device unusable. So zero position restoring force is needed, and it needs to be somewhat strong, hence the stiff suspension.
So bacis, that we have a serious argument about that. So maybe not so basic, but one has get off the high horse. I am very open to the situation where we communicate that I am wrong. Yes, teach me and humble me. No shame about it. But at the moment, it doesn´t look like it really.
If I get this right, then that statement of yours is not a true statement. If you add motor force, you will not have less extension. Not with such plain expression. Again. With stronger motor, the motor pushes more Newtons per Watt on the cone, and so at no point you get less bass. That is the issue with old ways and thinking in terms of constant voltage, not power.
I also did say nothing about smaller enclosure. All things same, just motor force. It seems you are manufacturing scenarios I did not suggest, and then clubbing me with these.
I like the practical proposal of the 1.25cu. ft test. This is close to the ad absurdum benchmark. Indeed, let´s do that! Set boundaries, parameters we can agree on, and go. This is great learning opportunity.
Smaller enclosures do indeed appear to be the reason for what's being discussed. Following with rapt attention. Great to see that a number of issues that I have pondering on for a few months now are also getting raised by others 🙂
The title of the thread literally says small enclosures and that is what we have been talking about. I'm not sure how any context that disregards enclosure size would be considered relevant.
I am a paid loudspeaker engineer, and have spent the last year developing a new subwoofer design that is exactly what we are talking about in this thread: low end extension in small airspace. It is a 15" that has a Fb of 39hz and a .62 qtc in a 1.25cf sealed enclosure, and it is going to be displayed in a demo booth at Cedia in a few weeks by a high end hifi company. What I am explaining in here, especially my rules of thumb for this exact scenario (which took a lot of R&D to figure out), is what I have gone through in the development process. It exists, and it exists exactly how I am explaining it, there is no hypothetical. My advice in this thread is literally about what you have to do to design a driver that works in small sealed airspaces. I am not trying to get on a high horse or humble anybody, but it's pretty ridiculous to explain exactly how to make a small sealed subwoofer and get people basically saying "nuh uh".