Let's use a box, dimensions 1 foot x 1 foot x 1 foot. Speaker diaphragm is 1 foot x 1 foot, and occupies an entire side of the cube. Pressure in box is 1 unit.
Diaphragm moves 0.5 feet into the cube. Pressure in box is now 2 units, an increase of 1 unit. Diaphragm moves 0.5 feet out of the cube. Pressure in box is now 0.67 units, a reduction of 0.33 units.
As you can see, change in pressure on the diaphragm is different according to whether the diaphragm moves inward or outward.
Air is a non-linear spring.
Loose wool fibres settle in volume after a time and it must be kept suspended within the cabinet.
Another way to achieve this is by making small stuffed parcels using modified fine denier tights.
Another way to achieve this is by making small stuffed parcels using modified fine denier tights.
Diaphragm moving in:
V1 = 1.0
P1 = 1.0
V2 = 0.5
P2 = (P1 x V1) / V2 = 2.0
Diaphragm moving out:
V1 = 0.5
P1 = 2.0
V2 = 1.5
P2 = (P1 x V1) / V2 = 1.0 / 1.5 = 2/3
Your maths is correct. However the answers obey Boyle's law which is a linear relationship between pressure and volume - that is the point I was making.
Yes, we all use a 12 inch square cone, traveling 12 inches ( peak to peak ) in a 1 cubic foot enclosure...
Let's get more realistic, a cone with a piston area of .2 feet , traveling .01 inch in, .01 inch out in a 1 cubic foot enclosure, resulting in a pressure unit of 0.99800399, to a pressure unit of 1.002004; the less the displacement, the less the nonlinearity. The weight of the cone/coil will add more nonlinearity than that, and there's plenty of subs with drivers underneath that work just fine.
Let's get more realistic, a cone with a piston area of .2 feet , traveling .01 inch in, .01 inch out in a 1 cubic foot enclosure, resulting in a pressure unit of 0.99800399, to a pressure unit of 1.002004; the less the displacement, the less the nonlinearity. The weight of the cone/coil will add more nonlinearity than that, and there's plenty of subs with drivers underneath that work just fine.
Oh for god's sake - I was illustrating a point on the subject of maths and physics. (And yet Galu still thinks that Pressure vs Volume is linear.)
And the subject came up only when it was suggested that adiabatic (i.e. unstuffed) operation was higher in distortion than isothermal (stuffed). Fact is that, either way, any distortion is going to be dominated by the intrinsically non-linear spring that is the air in the box. Stuffed or not won't make much difference, as far as distortion is concerned.
But, as I already stated, this is why subwoofers in larger boxes will show less distortion. It's a mistake to think that "acoustic suspension" is intrinsically linear - it's the opposite, but would only be problematic in extreme situations (where excursion causes significant volume modulation). Especially as the human ear finds 2nd-order HD quite pleasing.
As for the mass of the cone/coil, that's the one parameter that really is intrinsically linear in its effect.
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The linear relationship to which I refer is the one between pressure and the inverse of volume as expressed in Boyle's law - which you used to illustrate your point.
A linear force ( mass + gravity ) added to a non linear spring ( rising rate ) will result in more of a non linear spring.
If something is linear enough in real life applications, it's, well, linear enough in real life applications.
If something is linear enough in real life applications, it's, well, linear enough in real life applications.
It would be interesting to do an experiment measuring speaker outside. One case: box speaker. Another: same box speaker without back panel but equalized to the first case scenario. Would be interesting to see how impulse response and thd differs.
In isothermal compression, Pressure x Volume is constant (Boyle's law).
In adiabatic compression, Pressure x Volume to the power of gamma is constant.
In the real world, compression is a hybrid between the two.
In adiabatic compression, Pressure x Volume to the power of gamma is constant.
In the real world, compression is a hybrid between the two.
Keithj01 - I have found that the non-linearity of an air spring is connected to the fact that it does not obey Hooke's law - as can be demonstrated via Boyle's law.
i can now justify your statement regarding the non-linearity of an air spring, but at the risk of boring the pants off wesayso! 😀
i can now justify your statement regarding the non-linearity of an air spring, but at the risk of boring the pants off wesayso! 😀
If you want to ensure a certain "Made In Yourestandingthere" kind of look, I think OSB is a very valid option.
You just have not experienced proper Lutefisk in the right setting with the intended atmosphere and condiments (like a bootle or two of Akevitt).
https://en.wikipedia.org/wiki/Akvavit
I'll toast to that!
Melamine Foam is my personal favourite, together with sheep's wool.
IB crowd disagrees.