During a debate I highlighted the negative aspects of drivers with a large Xmax, inefficiency, sluggish response. I intimated there was a 'sweet spot', the ratio between Xmax and driver diameter. I used a piston engine bore / stroke as an example.
Certain members lost their minds!
To further my case I have made another observation which supports the case against. I have 6.5" driver with a ridiculously large Xmax, however, due to the large surround to accommodate the increased excursion, the diaphragm of the sub is smaller than that of a comparable 5" Hi-fi woofer.
I'm suggesting that in reducing the diaphragm size to accommodate a large Xmax you're simply producing a driver that requires more power to achieve the same result.
I'd appreciate somebody looking into the math on that.
Certain members lost their minds!
To further my case I have made another observation which supports the case against. I have 6.5" driver with a ridiculously large Xmax, however, due to the large surround to accommodate the increased excursion, the diaphragm of the sub is smaller than that of a comparable 5" Hi-fi woofer.
I'm suggesting that in reducing the diaphragm size to accommodate a large Xmax you're simply producing a driver that requires more power to achieve the same result.
I'd appreciate somebody looking into the math on that.
I'm not entirely sure what you mean by 'sluggish response' when you're looking at drivers with a large xmax.
Xmax and diaphragm area combine to produce a linear amount of swept volume displacement for the driver. It's easy enough to simulate the maximum theoretical SPL for a driver, at a given frequency, using freely available CAD software. You could use these to make reasonable comparisons.
Alternatively just look at the datasheets for various drivers and compare their SD and Xmax figures vs the chassis diameter.
What 6.5" driver are you talking about by the way?
Xmax and diaphragm area combine to produce a linear amount of swept volume displacement for the driver. It's easy enough to simulate the maximum theoretical SPL for a driver, at a given frequency, using freely available CAD software. You could use these to make reasonable comparisons.
Alternatively just look at the datasheets for various drivers and compare their SD and Xmax figures vs the chassis diameter.
What 6.5" driver are you talking about by the way?
It only takes 3rd grade math to figure out that a 12” woofer isn’t going to fit in a speaker enclosure that is 8” on a side. Why the push for small woofers? The desire for small *boxes*.
Alexa, play Tocatta in D. She’ll have a little trouble with that, but at least you’ll hear some of it.
Alexa, play Tocatta in D. She’ll have a little trouble with that, but at least you’ll hear some of it.
I'm not sure what is to be calculated but it should not be surprising that speakers with more surface area in rubber surround than cone sound rubbery to some people.
enter from the side. 1200cn2 or 1300 is pleanty of room for crossectioinal rectangle shapes at those needs. and can be shrunk in one dimesion from there. your at an advantage anyhow if on a node in a harmonic of the fundamental. this is not a driver cone size issue thats just an air pump. or meathod of it. please a few TS parameters and then its FINE tuned air pump instead of random misses of perfect pump action. acoustics need to remember elcetrical and mechanical versioins of pressure and mass velocity as well as capacatince and inducitve things. pretty hard to jump across these areas of concern but thyre al the real deal. motor force isnt BL. or QES. its a part of it after RE and LE have screwed it up. mass loaded air particles and/or mass of the moving parts are still dealing with VAS as capacative areas of potential concern? my head hurts just thinking about it all.... yikes friction and leaks in the math and reality...
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There is absolutely no difference in bass response if fc and Qtc (in cab) are identical no matter what the uncased values were. The volume works like an additional spring and the behaviour is the result of the complete system, also eventual filters contribute.
One example is https://www.parts-express.com/pedocs/specs/295-468-dayton-audio-rss390hf-4-specifications-46176.pdf
14mm=Xlin and Cms=0.22mm/N fulfill your sluggish idea
the same driver with hard suspension https://www.parts-express.com/pedocs/specs/295-044--dayton-audio-pn395-8--spec-sheet.pdf
Xlin=6.5mm Cms=0.09mm/N
The difference is that the rubber driver goes much deeper than the driver with hard suspension fs= 19.5Hz vs. 44.1Hz
The price for this is -10dB efficiency, less power handling and a bigger case.
It is also a fact that 1/2 of the surround contributes to the radiation area, so not so much is lost as you think. In fact the triple roll driver has almost the same radiating area 890.3cm² vs. 829.6cm²
One example is https://www.parts-express.com/pedocs/specs/295-468-dayton-audio-rss390hf-4-specifications-46176.pdf
14mm=Xlin and Cms=0.22mm/N fulfill your sluggish idea
the same driver with hard suspension https://www.parts-express.com/pedocs/specs/295-044--dayton-audio-pn395-8--spec-sheet.pdf
Xlin=6.5mm Cms=0.09mm/N
The difference is that the rubber driver goes much deeper than the driver with hard suspension fs= 19.5Hz vs. 44.1Hz
The price for this is -10dB efficiency, less power handling and a bigger case.
It is also a fact that 1/2 of the surround contributes to the radiation area, so not so much is lost as you think. In fact the triple roll driver has almost the same radiating area 890.3cm² vs. 829.6cm²
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theres an air spring and theres a soundwave. when they match in a length we can more easily observe at the same or a portion of it we are at a distinct advantage. vision. if it also fits with in the folding and harmoncs as sound wave of the same intervals then the whole thing is really clear and what happens is as well. im not good enough at a the math to o other wise so i stick to length based junk for subwooferes 😀 but i loooooove those RSS driver and RS drivers
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Some loose reasoning that might be helpful:
If you assume the following points:
Thiele/Small parameters - Wikipedia
But.. the larger woofer must have a stiffer suspension to keep Vas the same. Therefore the cone must be heavier to keep fs the same. As it has the same value of Qes, the larger woofer must have a stronger motor, which is BL/sqrt(Re). On the other hand, it has a shorter stroke, so less magnet and coil material is required for a given motor strength.
It depends on what assumptions you make when comparing the large and small woofer.
If you assume the following points:
- Compare two systems: one with a large woofer, one with a small woofer
- Closed boxes
- Vas, fs, Qts, Qes, Qms are the same
- Box size, fc and Qtc are the same
Thiele/Small parameters - Wikipedia
But.. the larger woofer must have a stiffer suspension to keep Vas the same. Therefore the cone must be heavier to keep fs the same. As it has the same value of Qes, the larger woofer must have a stronger motor, which is BL/sqrt(Re). On the other hand, it has a shorter stroke, so less magnet and coil material is required for a given motor strength.
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