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#1
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Vas.....what does it really mean?
Let's say you have 2-15 inch subwoofers both have comparable specs
except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? |
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#2
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Vas.....what does it really mean?
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#3
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Vas.....what does it really mean?
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#4
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Vas.....what does it really mean?
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#6
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Vas.....what does it really mean?
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#7
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Vas.....what does it really mean?
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#8
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Vas.....what does it really mean?
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#9
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Vas.....what does it really mean?
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#10
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Vas.....what does it really mean?
Vas. Half of Vas Deferens. The tube that connects your balls to
your prick. OK? |
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#11
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Vas.....what does it really mean?
Vas. Half of Vas Deferens. The tube that connects your balls to
your prick. OK? |
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#12
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Vas.....what does it really mean?
Vas. Half of Vas Deferens. The tube that connects your balls to
your prick. OK? |
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#13
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Vas.....what does it really mean?
Vas. Half of Vas Deferens. The tube that connects your balls to
your prick. OK? |
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#14
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Vas.....what does it really mean?
Laurence Payne wrote in message . ..
Vas. Half of Vas Deferens. The tube that connects your balls to your prick. OK? If you have so much interest in my tools I can have it arranged so you can view them........Or just STFU! |
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#15
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Vas.....what does it really mean?
Laurence Payne wrote in message . ..
Vas. Half of Vas Deferens. The tube that connects your balls to your prick. OK? If you have so much interest in my tools I can have it arranged so you can view them........Or just STFU! |
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#16
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Vas.....what does it really mean?
Laurence Payne wrote in message . ..
Vas. Half of Vas Deferens. The tube that connects your balls to your prick. OK? If you have so much interest in my tools I can have it arranged so you can view them........Or just STFU! |
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#17
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Vas.....what does it really mean?
Laurence Payne wrote in message . ..
Vas. Half of Vas Deferens. The tube that connects your balls to your prick. OK? If you have so much interest in my tools I can have it arranged so you can view them........Or just STFU! |
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#19
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Vas.....what does it really mean?
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote:
Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. d _____________________________ http://www.pearce.uk.com |
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#20
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Vas.....what does it really mean?
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote:
Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. d _____________________________ http://www.pearce.uk.com |
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#21
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Vas.....what does it really mean?
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote:
Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. d _____________________________ http://www.pearce.uk.com |
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#22
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote: Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. |
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#23
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote: Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. |
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#24
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote: Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. |
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#25
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 13 Feb 2004 15:10:30 -0800, (conrad) wrote: Let's say you have 2-15 inch subwoofers both have comparable specs except one has higher VAS(one has 3.4 and the other 8.5)..you install them both in equal sealed boxes..which one will have greater bass..or what I really want to say "chest pounding bass"is it safe to say that the one with greater vas has greater compliance hence easier to drive and more louder? If the volume of the box is much smaller than the Vas of either speaker, then there will be no great difference. The big difference between these drivers is that the one with the bigger Vas can make good use of a far bigger box than the other. I have just built a sealed subwoofer into a concrete cupboard of 80 cubic feet volume. I used a driver with a really big Vas, and I now have a system that produces really, really low bass very well. It isn't chest-thumping though - that is generally a sign of a one-note, ported system designed for home cinema rather than music. Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. |
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#26
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Vas.....what does it really mean?
On 15 Feb 2004 07:06:20 -0800, (Svante)
wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. It will still be a small box, though, and to get any kind of bass response it will need to be ported - with all the unpleasant and unnatural bass response that goes with it. d _____________________________ http://www.pearce.uk.com |
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#27
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Vas.....what does it really mean?
On 15 Feb 2004 07:06:20 -0800, (Svante)
wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. It will still be a small box, though, and to get any kind of bass response it will need to be ported - with all the unpleasant and unnatural bass response that goes with it. d _____________________________ http://www.pearce.uk.com |
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#28
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Vas.....what does it really mean?
On 15 Feb 2004 07:06:20 -0800, (Svante)
wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. It will still be a small box, though, and to get any kind of bass response it will need to be ported - with all the unpleasant and unnatural bass response that goes with it. d _____________________________ http://www.pearce.uk.com |
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#29
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Vas.....what does it really mean?
On 15 Feb 2004 07:06:20 -0800, (Svante)
wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. It will still be a small box, though, and to get any kind of bass response it will need to be ported - with all the unpleasant and unnatural bass response that goes with it. d _____________________________ http://www.pearce.uk.com |
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#31
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Vas.....what does it really mean?
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#32
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Vas.....what does it really mean?
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#33
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Vas.....what does it really mean?
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#34
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. |
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#35
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. |
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#36
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. |
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Vas.....what does it really mean?
Don Pearce wrote in message . ..
On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. |
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Vas.....what does it really mean?
On 15 Feb 2004 14:35:09 -0800, (Dick Pierce)
wrote: Don Pearce wrote in message . .. On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. This is the point I was making about needing to consider all the parameters. A low Fs is good, and it is achieved by a high compliance. But mass is the other term in the equation, but there is good mass and bad mass. Good mass is the air you are moving, and bad mass is the cone. You can lower Fs by making the cone heavier, but only at the expense of poorer sensitivity. The result will always be less output for a given power, not more. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. I was not really talking about "in the passband" here, but in terms of low end extension. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system True but easily dealt with by not allowing those really low frequencies through. 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. When you are designing a one-off subwoofer, you will (OK: if you are me you will) measure the TS parameters for yourself and design round those. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. Well, yes - my opinion based on listening to far too many subwoofers over the years, and rejecting them all as sounding totally unnatural. It is not until now, with my IB sub finished and tuned in that I am satisfied. It is also interesting that the tuning in procedure was staggeringly easy with this sub. That alone says to me that is was a design that was simply right. d _____________________________ http://www.pearce.uk.com |
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Vas.....what does it really mean?
On 15 Feb 2004 14:35:09 -0800, (Dick Pierce)
wrote: Don Pearce wrote in message . .. On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. This is the point I was making about needing to consider all the parameters. A low Fs is good, and it is achieved by a high compliance. But mass is the other term in the equation, but there is good mass and bad mass. Good mass is the air you are moving, and bad mass is the cone. You can lower Fs by making the cone heavier, but only at the expense of poorer sensitivity. The result will always be less output for a given power, not more. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. I was not really talking about "in the passband" here, but in terms of low end extension. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system True but easily dealt with by not allowing those really low frequencies through. 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. When you are designing a one-off subwoofer, you will (OK: if you are me you will) measure the TS parameters for yourself and design round those. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. Well, yes - my opinion based on listening to far too many subwoofers over the years, and rejecting them all as sounding totally unnatural. It is not until now, with my IB sub finished and tuned in that I am satisfied. It is also interesting that the tuning in procedure was staggeringly easy with this sub. That alone says to me that is was a design that was simply right. d _____________________________ http://www.pearce.uk.com |
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Vas.....what does it really mean?
On 15 Feb 2004 14:35:09 -0800, (Dick Pierce)
wrote: Don Pearce wrote in message . .. On 15 Feb 2004 07:06:20 -0800, (Svante) wrote: Suffice to say, though that Vas is just one of the parameters that matter. Use a loudspeaker design programme, and read up on the theory so you understand all the parameters, and what they mean. That way you can design a sub that matches your room in the low bass range, rather than thudding and booming unpleasantly. Hmm... You make it sound like a high Vas value would be good. I'd say that (given that everything else is the same) if one speaker has a twice the Vas of another, it will *need* a twice as large box. With that box, it will produce *the same* response as the smaller box. Choosing between the two systems, I'd take the smaller box. No. Vas is the volume of box that would provide the same restoration force as the suspension of the cone. The total restoration force on the cone is the parallel combination of Vas and the actual box volume. Actaully, your are both correct. IF all other parameters were the same (which they almost never are), then a driver with a larger Vas will require a proportionally larger enclosure to achieve the same response. AND, yes, that Vas is the "equivalent volume of compliance:" it is that enclosed volume that, for the emmissive area of the diaphragm, will have the same effective acoustic compliance as the suspension itself does. And, as well, the total complianmce is determined by the COMBINATION of Vas and Vb. Vas is derived from mechanical compliance Cms as: Vas = Cms p0 c^2 Sd^2 where p0 is the density of air, c is the speed of sound in air and Sd is the emissive area of the diaphragm. Now, the PROBLEM is that it is EXTREMELY difficult to fabricate two drivers all of whose parameters are the same EXCEPT for Vas. For example, doubling the Vas by doubling the mechanical compliance lowers the resonant frequency by a factor of sqrt(2). So the resonant frequencies can't be the same UNLESS the moving mass Mms of the driver with doubled Vas is half that of the other driver. But then, the driver with the lower mass will ALSO have half the Q figures and FOUR times the efficiency, unless we lower the Bl product by a factor of two. This is the point I was making about needing to consider all the parameters. A low Fs is good, and it is achieved by a high compliance. But mass is the other term in the equation, but there is good mass and bad mass. Good mass is the air you are moving, and bad mass is the cone. You can lower Fs by making the cone heavier, but only at the expense of poorer sensitivity. The result will always be less output for a given power, not more. So while it's an interesting academic excercise to ponder what it would be like to have two drivers otherwise identical save for the equivalent volume of compliance, it has little, if any practical use. What this means is that for a speaker with low Vas, there is no point in trying to use a big box, because Vas sets an upper limit to effective box size. With a large value of Vas you have a choice, either to maintain the limitations of a small box, or use a greater physical volume to free up the motion of the cone beyond the limits of the low Vas speaker. Well, no. Inm the passband, the motion of the cone is NOT determined either by the suspension compliance or the enclosure compliance. It is largely determined by the moving mass. This is because in any mechanically resonant system, above resonance (and, thus, in this case, above cutoff, in the passband), the system is operating in the mass- controlled region. I was not really talking about "in the passband" here, but in terms of low end extension. Using twice as large a box with a higher Vas does not produce the same result, but a far more extended bass response. Well, subject to the practical limitations outlined above, no it will not have a "far more" extended bass response. Maybe somewhat somewhat extended response, but not "far more." Of course you can use a small box with either speaker, because all it does is fail to exploit the qualities available with a larger Vas. But you're only looking at one particular aspect of the problem. There are GOOD reasons for using a box volume significantly smaller than the Vas, including: 1. Since the box compliance dominates, and since the box compliance is decidely more linear than the best mechanical suspension, at those frequencies where the system is largely compliance- controlled, i.e. at and below resonance, the non-linearity of system will be largely determined by the box, NOT by the suspension. The generally means reduced distortion at the very lowest limits of the system True but easily dealt with by not allowing those really low frequencies through. 2. And, again, since the box comlpiance dominates, and since it is MUCH easier to control the box compliance during manufacturing (it's simply a case of maintaining the dimensions of the box) than it is to control the suspension compliance, then the inevitable variations in suspension compliance are insignificant in determining the total system compliance and thus system response. When you are designing a one-off subwoofer, you will (OK: if you are me you will) measure the TS parameters for yourself and design round those. It will still be a small box, though, and to get any kind of bass response it will need to be ported Or equalized. - with all the unpleasant and unnatural bass response that goes with it. This is opinion stated as fact. There are examples of ported systems whose low frequency repsonse can be considered exemplory, as there are examples of sealed systems whose low frequency response is pretty unpleasant and unnatural. Any idiot can design a loudspeaker and, unfortunately, many do. Well, yes - my opinion based on listening to far too many subwoofers over the years, and rejecting them all as sounding totally unnatural. It is not until now, with my IB sub finished and tuned in that I am satisfied. It is also interesting that the tuning in procedure was staggeringly easy with this sub. That alone says to me that is was a design that was simply right. d _____________________________ http://www.pearce.uk.com |
The OP *did* say that the 2 woofers
Linear Mode
