what about Large signal parameters

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I wonder how effective it is to just know thiele small parameters for pro drivers, as pro drivers will be used to its almost full Power / extrusion, which would change the thiele parameters completely.

For eg. If we consider an 18” or 15” driver having a qes of 0.28 and xmax of 6mm (Linear) and to be used in a horn cabinet. Now driving the driver above 6mm (one side) when the coil is half out of magnet field this would change almost all the thiele small parameters. So what would be the effect on the sound output.

So a Driver with a xmax which would be linear till it touches touches the back plate OR Max extrution to be linear would be the best.

I assume small thiele parameters would come into effect for knowing what type of enclosure would be best for the driver, and one should also consider Large signal Parameters if its to be used in a Pro use.
 
I wonder how effective it is to just know thiele small parameters for pro drivers, as pro drivers will be used to its almost full Power / extrusion, which would change the thiele parameters completely.

For eg. If we consider an 18” or 15” driver having a qes of 0.28 and xmax of 6mm (Linear) and to be used in a horn cabinet. Now driving the driver above 6mm (one side) when the coil is half out of magnet field this would change almost all the thiele small parameters. So what would be the effect on the sound output.

So a Driver with a xmax which would be linear till it touches touches the back plate OR Max extrution to be linear would be the best.

I assume small thiele parameters would come into effect for knowing what type of enclosure would be best for the driver, and one should also consider Large signal Parameters if its to be used in a Pro use.
 
The only large-signal parameters that you usually find are things like x-max and thermal compression (if you are lucky).
It would be very difficult to design/calculate an alignment with dynamic nonlinearity taken into account (what frequency at what SPL would you want to design it for ?).
The best thing one can do is trying to not add more dynamic nonlinearity that is already there by using generously dimensioned port areas, not placing damping material too closely to drivers etc.

Regards

Charles
 
T/S parameters are really only small signal parameters, although people do measure at large signal levels and use those for designing enclosures as well. I've heard people say that enclosures designed this way sound good, but I haven't tried it myself.

Probably the most widely used method for measuring parameters at various levels is the Klippel analyzer. The basic parameters measured are BL, Cms, and Le vs cone excursion (well, really current and voltage are measured, Sd, Mms, and BL at zero excursion are known, and everything else is calculated). The software also calculates variation in Fs, Q values, Re, etc. There's more information on the Klippel website. Most major driver manufacturers have one of these machines, but they don't publish the data.

For common overhung drivers, they usually begin to distort as soon as they move from rest. Xmax is only a number showing where the distortion starts to become objectionable. Underhung coils or things like Adire's XBL2 motors can lower BL distortion. Shorting rings can reduce Le distortion. There are things you can do to reduce the change in Re. Good design of a spider can reduce Cms distortion. Needless to say these things are not common, so the drivers that use them cost more.

Also, I would not want a driver that was linear up to its mechanical limit. That would invite driving it to that limit and tearing it up. If you have some extra room for the driver to move where distortion goes up, then you will know to turn down the volume before you break something.
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
You would want the driver to be linear for small signals, but also when offset from neutral position. most high frequency content are of small amplitude.

For low frequency signal, the amplitude is large, and you would want it to be linear because distortion would be interpreted as a higher frequency content in reality.

So linear over the full range is the best. Designing speakers just based on TS parameters only might be misleading because the model is reduced for academic theory explanation purposes, and not for actual design acurracy.
 
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