Subwoofer-shake cancellation theory...

…I think a better idea is a driver on the inside with no cone per say...but a mass attached to a VC
That is essentially what a bass-shaker is. Often the coil and the magnet positions are swapped(ie stationary VC, magnet attached to suspension). This improves cooling of VC and you get the required added mass for “free”, since you needed the magnet anyways.

What is wrong with good old bracing, damping and padding to get rid of resonances. Why introduce another resonance creator in the form of a shaker.
Brace and damp your enclosure to your hearts content, then attach it to a wall and turn up the bass…you will have your answer. The slim profiled SubRosa was designed to be mounted either in-wall or on-wall. Back in the day, there was a pretty slick demo setup in a Dallas AV store where you could switch on/off the vibration cancelling shaker. With it off during bass heavy movie scenes it sounded horrible, like the walls were going to vibrate apart. Switched on, and you were left with clean bass. Placing a hand on the enclosure or wall during intense action scenes, it was pretty impressive how little vibration remained while those 2 woofers were pumping away.
 
To recap TS: "Most of the time, the cabinets are heavy enough to keep the subwoofer in check, but with the new breed of long-throw high-mass power-hungry mongrels, the boxes really don't have to be very big or stout to accomplish the performance goals- unless you want it to sit still as well". And TS think in theory a Bass shaker type of fix for resonances will work

I made a joke (notice smiley face in my post) and in the end Weltersys solved it because someone already tried and even patented it.

Wolf_Teeth It seems to work. So now build a prototype and shake it baby! :p
 
Camplo,

Bolserst already linked to patents for both, and a commercial product that uses the concept of a "shaker" to cancel vibrational force in a subwoofer in post #30, before someone revived this thread.

Before commenting on "impossibilities", helps to know what has already been accomplished decades past.

SubSoniks- blobs of "bluetack" won't cancel force, and won't keep a light cabinet with a single, heavy, forward/rearward facing cone at high excursion from "walking", as many low frequency waveforms are asymmetrical, "hammering" the moving mass more in one direction than another.

Art


Fact:

i can get a twin thermo acoustic motor suspended in air (overhead fishing line or similar) to start rotating from its own offset moments of inertia. Even as two in equally positioned snd ‘balanced’ opposition. Youtube: ‘blade atilla’. Its only the beginning...:thumbsup:


~not quite 100% a ‘fact, but almost:

if i place that hot/cold source at the same location as we use for ‘offset driver Qw pipes’ that fill the 3x qw fb void, it is lame. Its dead, it Wont spin! Its a fulcrum In pressure wave for us, but also in the system of energy and mass conservation or whatever apple fell and hit my head while trying to be issac newton or Gauss or Fournier, lol(?) (or just clueless nitwit!)
 
People have probably thought of this but I cannot see it mentioned in this thread.
Threaded rod is readily available in various lengths and diameters. You could easily poke it through the mounting holes of both drivers and put nuts on each end. Better than nothing I guess. You would need to seal the rod on exit points of course. I will try this on a new build and see how it goes.
 
I know. A simple solution for the oscillating sub of course is mounting it on a suspension with resonance frequency below low cutoff frequency of the sub. I mean, the average washing machine has far bigger ‘shake’ challenges than any sub, see how simply they are encountered.

And: use a (subsonic) high pass filter to reduce excessive cone movements that don’t do anything in terms of sound output. Taking away the cause instead of trying to cure the problem.
 
People have probably thought of this but I cannot see it mentioned in this thread.
Threaded rod is readily available in various lengths and diameters. You could easily poke it through the mounting holes of both drivers and put nuts on each end. Better than nothing I guess. You would need to seal the rod on exit points of course. I will try this on a new build and see how it goes.

OK I have played around with this idea some more.
It works but needs modifications.
All drivers I have seen have holes suitable for M4 bolts/screws.
If you just use threaded rod terminated in a nut it looks ugly.
So I tried domed nuts, better.
But some drivers have a surround that is too small for a nut. They are designed for bolts or screws.
And they are a PITA to connect.
So my latest plan is to use M4 bolts on the drivers, connected to M4 hex couplers, to threaded rod, to another coupler then bolt on the other driver.
You need access via top and bottom so leave those off until everything is fixed.
You only need 4. Most drivers have 6 or even 8 bolt holes. Use screws in the remaining holes and put them in first to make fixing the threaded rod easier.
This has another advantage in that it does away with the need for box bracing in my tiny 17L sub boxes.
Hope this helps someone.