Thanks!
Yeah you basically visualized what Klippel et all have written down as well what can be concluded by just looking at the definitions, the point where I started 🙂
Great addition to this story for those who find it hard to picture how this practically translates! 🙂
It does make you wonder if choosing a subwoofer with a very low Fs could be beneficial as well?
Since we are pushing the effect of the change in compliance down even further.
Although it already feels like there will be some kind of compromise there...
Yeah you basically visualized what Klippel et all have written down as well what can be concluded by just looking at the definitions, the point where I started 🙂
Great addition to this story for those who find it hard to picture how this practically translates! 🙂
It does make you wonder if choosing a subwoofer with a very low Fs could be beneficial as well?
Since we are pushing the effect of the change in compliance down even further.
Although it already feels like there will be some kind of compromise there...
The box air ‘spring’ is also nonlinear since the volume is modulated. I don’t think the effective air mass load changes much with the box volume.
Sorry, I deleted the previous comment. Okay, the air mass inside the box is not a significant contributor to the moving mass. But the driver suspension stiffness can change significantly with different box sizes.
Doesn't the non-linearity of the air box spring increase with the reduction of the air volume? I remember seeing a chart at one time showing this relationship. Obviously the larger the Sd the greater the non-linearity as well.
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Haha, well there is nothing bad about saying that 🙂
If we take a step back to reality, in same cases we can't or don't want to go bigger.
Yet, still want to enjoy all great performance and quality gains 🙂
18 inch subs are great, but if you can't use them for whatever reason, they are quite useless at the same time. 😉
Are there actually inherent downsides in lowering the stiffness?
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It's all about pressure = SPL
At the same sound pressure levels a bigger driver will do as much as a smaller one, just with less cone excursion since Vd = Sd * x
But yeah, if you want to go louder, you technically also need a bigger cabinet or have to deal with a little bit more distortion.
Not that long ago I think @markbakk calculated that. (could be someone else)
If I am not mistaken the distortion was in the order of magnitude of a 1-3% or so.
So the only way is to go big, which introduces other issues like internal cabinet resonances, more volume/space etc.
Or have no cabinet at all, but in that case the efficiency is so low that you have to compensate that with cone excursion = introducing more distortion again.
Plus you still need need a massive baffle, even a ripole isn't that small and still not very effective at very low frequencies (say below 40Hz)
Unfortunately the law of conservation of misery still holds up.
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I was more specifically asking about the non-linearity of the air spring constant that Irisbo was discussing,
at some point the mechanical stability over the full excursion range is lost (rub and buzz). BTW, the old 'Acoustic Suspension' principle was exactly to let the air spring totally dominate, ie a soft suspension.
Box air nonlinearity: The gas law says that the pressure is proportional to 1/(1+Vd(t)/Vbox)). The Taylor series for 1/(1+x) is somthing like 1-x+x^2-x^3. From this we can calculate the expected harmonics by letting x=Vd(t)/Vbox.
If that is the only option available, it's the only idea, therefor a great idea 😉
Things are by definition a set of compromises.
Personally speaking, a penalty of a few perfect of plain HD distortion at low frequencies, is something I am willing to take compared to a lot of other things.
@lrisbo In theory we could actually design the Kms in such a way that it would compensate for this.
Although only to a small amount and only valid for one specific size cabinet.
I guess you mean rocking here?
Yeah, back in the day it was all focused on efficiency, so little cone excursion = less of these kinds of problem
You only have to deal with a massive cabinet, creating all kinds of other sorts of problems. 🤣
damn bloody physics.......
No, but you'll need a ton of additional cone excursion in return, see a couple of posts above.
Which is not only gonna be more than just a few percent of HD distortion, but introduces more IMD as well.
So we didn't solve much.
"Percent", i suppose?
And am i correctly assuming it's H2 mostly, thus not very disturbing?
Don't quite agree with that. It's easy to add more woofers/Sd in OB to limit Xmax. In IB bass works just as infinite box so you just don't get this added box compliance with it's variations.
Adding more woofers also works in closed boxes.
Sure we can add more stuff, but that doesn't make it apples to apples anymore.
We are talking about similar systems here.
An infinite baffle isn't really practical btw.
You might as well just build a big cabinet instead, does nearly the same thing.