Vas, cms, etc... for Dipoles

[EC8010]

I don't understand why anyone should be interested in Vas for a driver on an open baffle; Vas is a parameter that is relevant when dealing with boxes. On an open baffle, the only important parameters are fs, Qts, and efficiency. As a sweeping statement, output falls at 6dB/octave as frequency falls from an open baffle, and the frequency at which that happens is inversely proportional to the size of the baffle, so the primary consideration is the size of the baffle. In practice, there are ripples in the response caused by the peaks and nulls from in and out-of-phase addition. A bigger baffle makes the difference between the peak and null frequencies smaller, so it makes the amplitude of the peaks and nulls smaller. That's why a big baffle is better than a little one. I have a sneaking suspicion that there may be a critical minimum size of baffle related to the ear's FFT process and low frequency discrimination.

Once the applied frequency falls to fs, the 12db/octave attenuation of the driver is added to that of the baffle, or, to put it another way, there's no point in using a driver with a lower fs than the baffle response (equalised or not). Reduced fs always forces reduced sensitivity.

The graph in the earlier post demonstrated the effect of Qts. It's much easier to electronically equalise lower values of Qts.

[Raka]

It seems that everyone wants to talk about how to equalize a dipole, well the information is welcome, but is not the point.

Keltic, thanks for the link, it's very interesting the Vas value. In the AES paper Vas it's mentioned, but in a generic way and related to system efficiency.
What intrigues me is what happens to the cone modes if they are not damped by a closed box, and how to measure/valuate this effect.