B&W FST drivers are designed by default to be terminated progressive radial wave drivers. This just basically describes a fancy high internal loss cone profile which progressively absorbs higher frequncies as they travel outwards through the cone.
As the input signal frequency rises, the earlier the sound wave gets absorbed to the VC perimeter. Opposite of this, the lower frequency waves are able to travel further outwards through the cone, presenting a progressively larger effective cone diameter to lower frequency sounds. Providing you had a sufficiently shallow cone profile, the high frequency off axis performance was very good. The top end frequency limit was defined by the decoupled VC mass and inductance
Some older fostex full range drivers were designed similar to these FST mids. A soft polymer connecting the cone to the VC acts as a passive mechanical crossover, progressively decoupling the VC from the cone at higher frequencies.
As the input signal frequency rises, the earlier the sound wave gets absorbed to the VC perimeter. Opposite of this, the lower frequency waves are able to travel further outwards through the cone, presenting a progressively larger effective cone diameter to lower frequency sounds. Providing you had a sufficiently shallow cone profile, the high frequency off axis performance was very good. The top end frequency limit was defined by the decoupled VC mass and inductance
Some older fostex full range drivers were designed similar to these FST mids. A soft polymer connecting the cone to the VC acts as a passive mechanical crossover, progressively decoupling the VC from the cone at higher frequencies.
Interesting. For those who have not followed the "Experiments with the current drive"-Thread, The FR is eq'ed to be identical, and the same SPL level is dialled in. Btw, how do you eq to exactly the same FR? Rephase?
Current drive doesn't do much for even order distortion and is acutally detrimental around resonance where mechanical nonlinearites start to dominate if electric damping is taken away.
I am surprised it drops HD3 by 10 and HD5 by 5 dB. Are these the yellow drivers both of us bought from England? That motor is about as good as it gets, and unlike the Purifi motor, it still benefits substantially from approximated current drive!
Current drive doesn't do much for even order distortion and is acutally detrimental around resonance where mechanical nonlinearites start to dominate if electric damping is taken away.
I am surprised it drops HD3 by 10 and HD5 by 5 dB. Are these the yellow drivers both of us bought from England? That motor is about as good as it gets, and unlike the Purifi motor, it still benefits substantially from approximated current drive!
Just googled 801D4. That is a €40k speaker that came out in 2021, so I would expect its FST driver to be even better than the yellow one. Did they use a simpler motor?
"No. Safe the best for last" Kind of a cliffhanger. Maybe the 2014 DST is better than the 2021 DST?
?
It has been redesigned completely. Ne basket, magnet, cone materials etc.
Just look at a few pictures of the proposed drivers and you would see that.
Who says it is worse? there is a difference in H3.
There is other factors then distortion that matters. Depends on your intended purpose of use. Actually it is the least quantifyable and comparable measurement there is in many ways.
And do note the 2014 kevlar version was measured with a XO in place for the comparison.
The main problem is we all have is the same 24 hours in a day.
Right now all one can say that they are different- the new cone has a smoother FR. But it has a single neo motor.
Whilst the festival one has a double neo motor like thr theatre based FST from the CT8LR. And around 6dB higher sensitivity. Is it due to the cone , voice coil motor or suspension ?
Given that it’s around 100dB/2.83V (ref 1Khz) it not exactly surprising that the harmonics are lower for any given SPL with a log chirp / exponential sine sweep.
As I gather more data I will post findings in the initial post.
Can they improved with a passive XO?
Active crossover? Or current drive? Or a combination? Who says we have to stick to one?
Also, I need some improvements to my environment before I can take measurements which may correlate better with perception
Right now all one can say that they are different- the new cone has a smoother FR. But it has a single neo motor.
Whilst the festival one has a double neo motor like thr theatre based FST from the CT8LR. And around 6dB higher sensitivity. Is it due to the cone , voice coil motor or suspension ?
Given that it’s around 100dB/2.83V (ref 1Khz) it not exactly surprising that the harmonics are lower for any given SPL with a log chirp / exponential sine sweep.
As I gather more data I will post findings in the initial post.
Can they improved with a passive XO?
Active crossover? Or current drive? Or a combination? Who says we have to stick to one?
Also, I need some improvements to my environment before I can take measurements which may correlate better with perception