One thing to mention in connections with this. Vas, fs and Qts are important values when designing the box, but they are derived from the underlying physical parameters like Cms, Mms etc. Here we are mainly discussing changes in Cms, and it affects both Vas, fs and Qts greatly.
However, the effects are such that they mainly cancel each other's effects on frequency response. Below is a simulation of a system with a classic max flat design (Cms=1mm/N, green line).
Look how small the changes are if the suspension stiffness changes! This is particularly true if the suspension gets less stiff. Physically the Cms variation is the only change between the systems, just as it would in the real world. The "high level" parameters Vas, fs and Qts changes a lot as a consequence of this, though.
High-level parameters for the systems are
Blue: fs=49 Hz, Qts=0.54, Vas=16 liter
Green: fs=35 Hz, Qts=0.38, Vas=33 liter
Red: fs=24 Hz, Qts=0.27, Vas=65 liter
Yellow: fs=18 Hz, Qts=0.19, Vas=131 liter
...bottom line here is that Cms changes are far less important than one may think. It is not good enough to model the change as a Vas change, unless the corresponding changes in fs and Qts are taken into account. Most simulation softwares want Vas, fs and Qts, so this is a bit of a pitfall.
However, the effects are such that they mainly cancel each other's effects on frequency response. Below is a simulation of a system with a classic max flat design (Cms=1mm/N, green line).
Look how small the changes are if the suspension stiffness changes! This is particularly true if the suspension gets less stiff. Physically the Cms variation is the only change between the systems, just as it would in the real world. The "high level" parameters Vas, fs and Qts changes a lot as a consequence of this, though.
High-level parameters for the systems are
Blue: fs=49 Hz, Qts=0.54, Vas=16 liter
Green: fs=35 Hz, Qts=0.38, Vas=33 liter
Red: fs=24 Hz, Qts=0.27, Vas=65 liter
Yellow: fs=18 Hz, Qts=0.19, Vas=131 liter
An externally hosted image should be here but it was not working when we last tested it.
...bottom line here is that Cms changes are far less important than one may think. It is not good enough to model the change as a Vas change, unless the corresponding changes in fs and Qts are taken into account. Most simulation softwares want Vas, fs and Qts, so this is a bit of a pitfall.
Hi,
Svante, you forgot to say that in Basta there is possible to change Cms alone and watch other “higher level” parameters change correspondingly, very convenient.
I think that while Andrew test with a very low level the cloth cladding mostly acting with property's as a spring (more so when cold). Once we have higher excursion cladding will be more of an elastomer, it will then be more lossy and absorb some energy and therefore heat up a bit, thus softening a bit.
Just as Cal says, “ warm up” in cold weather.
Svante, you forgot to say that in Basta there is possible to change Cms alone and watch other “higher level” parameters change correspondingly, very convenient.
I think that while Andrew test with a very low level the cloth cladding mostly acting with property's as a spring (more so when cold). Once we have higher excursion cladding will be more of an elastomer, it will then be more lossy and absorb some energy and therefore heat up a bit, thus softening a bit.
Just as Cal says, “ warm up” in cold weather.
Hi,
old thread similar topic.
Took a pair of small 2way to a friend. Left them in the car overnight. -1degC last night.
Brought them back in to my house minutes ago and plugged them back into my audio system.
No bass, and maybe reduced mid as well.
As I am typing this the mid has come back and the bass is just starting to come back.
A very "toppy" sound that I'm not used to !
Stiff surround from the low temperatures must have reduced the LF excursion.
old thread similar topic.
Took a pair of small 2way to a friend. Left them in the car overnight. -1degC last night.
Brought them back in to my house minutes ago and plugged them back into my audio system.
No bass, and maybe reduced mid as well.
As I am typing this the mid has come back and the bass is just starting to come back.
A very "toppy" sound that I'm not used to !
Stiff surround from the low temperatures must have reduced the LF excursion.
Lot's of confusion
Despite the progress that has been the results of the mathematical models that has resultet in the Thiele7Small-parameters one must admit that the T/S-paraeters has also caused a lot of confusion.
This thread is is a perfect example of what the confusion is all about. As the Vas of a woofer is changing with temperature the models usually predict that also cabinet-volume and -tuning will have to be changed (with changes in temperature) sometimes substantially.
No wonder this is confusing.
Putting the same woofer in any reasonably sized closed box will almost take Cms and Vas out the equations, and force the designer to focus on the essential parameters: cone size, moving mass, BL-product and DC-resistance of the voice-coil (Sd, Mms, BL and Rdc).
With respect to most people the work done by Thiele, Small, Keele and many others have created confusion on a very high level. And the performance-increase that should have been a welcome result has very often not materialized.
Steen
Despite the progress that has been the results of the mathematical models that has resultet in the Thiele7Small-parameters one must admit that the T/S-paraeters has also caused a lot of confusion.
This thread is is a perfect example of what the confusion is all about. As the Vas of a woofer is changing with temperature the models usually predict that also cabinet-volume and -tuning will have to be changed (with changes in temperature) sometimes substantially.
No wonder this is confusing.
Putting the same woofer in any reasonably sized closed box will almost take Cms and Vas out the equations, and force the designer to focus on the essential parameters: cone size, moving mass, BL-product and DC-resistance of the voice-coil (Sd, Mms, BL and Rdc).
With respect to most people the work done by Thiele, Small, Keele and many others have created confusion on a very high level. And the performance-increase that should have been a welcome result has very often not materialized.
Steen
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