The "Real" Aerogel

[noodle_snacks]

There is the small matter of the fact that a midrange or bass cone requires some weight to bring the Fs down to a workable level.

The lightest, stiffest cone is not necessarily the best cone, if you want decent bass perfomance.

I don't pretend to know tons about it, but couldn't the electrical and mechanical parameters of a driver be adjusted to accomodate for this?

 

[AndrewT]

Hi,
there is a (loose) correlation between Fs and Mms.
However, different manufacturers and different efficiencies move this correlation around.

The answer being that a very soft suspension and low Mms can achieve a suitable Fs.

 

[APi]

There is the small matter of the fact that a midrange or bass cone requires some weight to bring the Fs down to a workable level.

The lightest, stiffest cone is not necessarily the best cone, if you want decent bass perfomance.

Your are right... almost

Usual cone mass and elastic suspension create mass-spring system that has some resonance frequency. When you drive current throught voice coil it creates force to cone.

1) Above resonance frequency this force accelerate cone mass (F=ma) and is much bigger that suspension force (F=kx). Acceleration of the cone is proportational to current (a=F/m).

2) But below resonance frequency acceleration is smaller and displacement is bigger. Therefore suspension force dominate and is equal to electromotive force. Displacement of the cone is proportational to current (x=F/k).

F = electromotive force
m = cone mass
a = cone acceleration
k = spring constant
x = cone displacement

If you want both linear frequency and phase response you should use element above frequency response where you get sound pressure proportational to current. Below resonance frequency you get displacement proportational to current so sound pressure drops constant 6dB/oct.

It doens´t mean that you cannot use element below resonance frequency if you just avoid resonance frequency and make active 6dB/oct corretion to drive current !!!

With very light cone it would be possible to do an element which have high resonant frequency and you would be possible to drive it ONLY BELOW resonance frequency and you wouldn´t need to worry about resonance frequencies any more. You could make speaker box very small so that resonance frequency is even bigger and still you have good bass reproduction. Lowest output frequency is limited by suspension, not resonance frequency.

The only cons are:
- You need more power from the amplifier.
- There could be a problem with harmonics if box volume to cone displacement -ratio is small.

 

[cotdt]

I will be investigating into these cones for my future drivers.