Thanks @AllenB .
I can use trial and error and measure the response. I wonder what is the max damping I could get so that I don't waste time building the box. Say, if I just short the coil with a 0-ohm resistor.
The real solution is to use passive radiators. But I'd like to find use for some drivers I do not plan to use otherwise.
I can use trial and error and measure the response. I wonder what is the max damping I could get so that I don't waste time building the box. Say, if I just short the coil with a 0-ohm resistor.
The real solution is to use passive radiators. But I'd like to find use for some drivers I do not plan to use otherwise.
An amplifier shorts the coil, so you know what the damping is if you want to put a number to it. Damping is the inverse of Q.
A shorted motor turns the driver into a piece of stiff cardboard.
The fs of the drivers is likely too high to be used as a passive radiator. Adding resistance would raise the fs, the opposite of adding weight to a pr.
There's no way to change the Fs of a driver electrically. The driver's Fs is determined by solely by its moving mass (primarily the cone and the voice coil and former) and its suspension (spider and surround). You'll have to either add or remove mass (the latter is a lot more difficult to do, LOL), or modify the driver's spider (~80% contribution) or surround (~20% contribution).
Fb, the resonant frequency of the driver when mounted in a box, will depend on the driver's parameters and the size of the box. This also can't be changed electrically, but you can electrically modify the driver's behaviour around Fb, e.g. changing the resistance attached across the voice coil's terminals will change the Q of the resonance at Fb.
Fb, the resonant frequency of the driver when mounted in a box, will depend on the driver's parameters and the size of the box. This also can't be changed electrically, but you can electrically modify the driver's behaviour around Fb, e.g. changing the resistance attached across the voice coil's terminals will change the Q of the resonance at Fb.
How about the opposite, give it some parallel delayed and Eq'ed feed from another amp :/ (active tuning weight?)
Adding resistance when using a driver as a PR will only reduce bass at the point where the PR cone velocity is highest. It will do no goodunless the box is mistuned and you can't add any more mass.
Nothing wrong with using separate processing on different drivers, but driven ("active") drivers are not passive radiators and processing does not change their weight or Fs.
Using old drivers for passive you would have to add weight.
Fb can be confirmed by measuring the impedance curve.
For low distortion, which passive unfortunately does quickly.
You need usually at least 2x the passive area as woofer area.
Older somewhat basic way to determine Fb is a salt test.
Woofer cone movement is very little at Fb.
So you do a frequency sweep and watch the salt you place on the woofer cone.
When you have least movement your at Fb.
Fb can be confirmed by measuring the impedance curve.
For low distortion, which passive unfortunately does quickly.
You need usually at least 2x the passive area as woofer area.
Older somewhat basic way to determine Fb is a salt test.
Woofer cone movement is very little at Fb.
So you do a frequency sweep and watch the salt you place on the woofer cone.
When you have least movement your at Fb.
Adding resistance across the terminals makes the driver "stiffer", a stiffer passive radiator has a higher free air resonance.
Anyway, as the OP wrote: "The real solution is to use passive radiators".
Adding a resistor across the terminals of an unconnected driver being used in place of a PR will apply a brake without friction
I have always wondered about modelling the behaviour of the tuning weight via electrical drive. Not the full signal but some analogue of PR behaviour in the form of a more advanced electric tuning
True. Interesting how physical circuits can be modelled as electronic circuits and vice versa. Physical being acoustic and mechanical systems. Like a 4WD drivetrain seems like it can almost be drawn as a circuit!
That's insightful and correct.
Inductor=mass
Capacitor=spring=stiffness
Resistor=friction=dashpot/shock absorber
Inductor=mass
Capacitor=spring=stiffness
Resistor=friction=dashpot/shock absorber
Thanks, I've been reading the posts in this thread. I can measure the curve. I should make a few tests when I'm back from vacations.