3" full range driver, high or low Qms

[Scottmoose]

Qes is no more a mathematical construct than Qms. Old timers who have done these measurements with a scope know, that you look at a point on the impedance curve that is 1/3rd lower than the maximum. This is of course arbitrary, it could have been 1/2 and nothing would change except the numbers. But the underlying physical quantities don't change. Qes is a measure of electric braking force and Qms of mechanical braking force.

Actually, Qms is a mathematical construct. When we talk about 'mathematical constructs' we are referring to unitless values which are mathematically derived from 'real' / fundamental properties, but are not fundamental properties themselves. Qms is not a physical property, merely a numerical means of expressing a number of given features, derived mathematically from those fundamental properties.

As to Scottmoose's point: there is no reason to believe that drivers need friction to operate. None.

T/S parameters do not exist in some isolated environment. They (as in Small's derivations from electrical filter theory, not the fundamental parameters) are 'just' expressions of behaviour up to the mass-corner -in the case of Qms the a lumped expression of mechanical damping. You appear to have focused so much on your concerns about friction you have forgotten what it actually is (a lumped expression of damping). If you are saying no drive unit requires mechanical damping, that is technical nonsense I'm afraid.

Take the Alpair 5.3 mentioned above as an example. Aluminium-magnesium alloy cone, and the surround (which is the only mechanical suspension element) is required to provide damping to the periphery of the cone and control its TL (resonant) modes in a given / desired way, as well as providing stability to the usual front-rear oscillatory motion, keeping the VC centred, and maintaining an air-seal around the cone itself. If that surround provided no damping, the cone & cap would ring / resonate in an uncontrolled fashion. QED: all drive units require some degree of damping, how much or how little depending on type. Now: a question for you. Do you think, based on that, that an Alpair 5.3 could work if it had, say, a Qms value of 8? I'll give you the answer: no. It couldn't. It's not physically possible to remove so much mechanical damping and maintain control over the coil and cone. You're welcome to try, if you think you know better than MA. Just commission an MOQ run with a Cms value that will provide you with the Qm value that you desire, and see how well it works. The results won't be pretty, I promise you that. 😉

 

[planet10]

I'm more looking at the cone geometry, cone material, frequency response, dispertion and distortion figures to see if a driver will be good sounding or not, not at T/S parameters. They only tell how low it can go in what kind of alignment and how big the speaker cabinet must be.

What he said.

dave

 

[planet10]

[QUOTE="vrbbra, post: 6931924, member: 534476”]...no matter Qms how you will describe without listening above mentioned drivers?
[/QUOTE]

In the end one has to listen.

I have heard good speakers that don’t look that good on paper, and good speakers on paper that sound like crap.

dave

 

[vrbbra]

Thanks all for comments. Maybe in new project try one of these two fullrange (Alpair 5.3 or SB) or try paper cone from Visaton B80.
Propose for driver would be cover 450, 500 Hz up in Open Baffle.