Yes, frantic armwaving will do it.
Just sitting on the chair and moving your arms slowly to one side will move the chair to the other side. Didn't Newton have a law about that?
Sure - that's been what I outlined as action and reaction according to the masses involved.(plus their distance to the pivot in this very case)
Point is - you always move back to the original position *immediately* - given your swivel would be *free* of friction - there is no phase lag nor resonances either.
No way to make a full turn (for example) and sit on the chair the same way you did before - no matter how frantic you exercise arm waving.
Same in the suggested pendulum case for flying speakers.
It is a *100%* compensation.
The limitation here is that we have to keep the moving system "self contained" (if thats the right word) - meaning we must not allow for directional or velocity dependent force or power leakage.
This never will be fully the case of course but optimization (basically minimizing friction that is) is easy and results to be achieved pretty good.
There are other leakage paths too of course - asymmetric front / back radiation of sound not being the last one for example ...
Push pull acoustic impedance asymmetry another one..
And so on...
Michael
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OK, I know what's wrong in my previous analogy of 'air wrench vs wheel screws', its impacts are uni-directional, not back and forth.
Well, then, what can be done to an as-built speaker? (no matter boxed or baffled)
It's not easy to 'float' the entire cabinet. I think of bike's inner tire as a cushion between speaker and floor. With proper pressure, such air spring could be very compliant. But there might be some proportion of tilting motions (directional dependent force) ...
Or linear bearing? But I guess there'd be a tad of initial friction....
Ah! a swing can't be beaten on this.
Any other ideas?
Well, then, what can be done to an as-built speaker? (no matter boxed or baffled)
It's not easy to 'float' the entire cabinet. I think of bike's inner tire as a cushion between speaker and floor. With proper pressure, such air spring could be very compliant. But there might be some proportion of tilting motions (directional dependent force) ...
Or linear bearing? But I guess there'd be a tad of initial friction....
Ah! a swing can't be beaten on this.
Any other ideas?
Yes as well, but also not exactly at the point, CLS – the point regarding *impulse compensation* that you have to focus on :
standing on the floor with the air wrench in your hands – your body provides a "return path" for the force applied to the tire screws.
You would have to let go the power wrench to get a "self contained" system - or - as described - stand not at the floor but on the wheel instead.
Michael
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I had an observation the other day...
I don't have accelerometers or other instrument for this, only by fingers' touch. I found the vibrations were quite different on baffle suface and driver's frame. And also quite different in various locations on the baffles.
My woofers are secured on the baffles by screws and T-nut rigidly. Well, they should be rigid enough. Since no flexible gaskets/spacers or the likes are used. Metal frames contact plywood or MDF driectly, cramped by the screws and nuts.
The baffles have two kinds of feet to support them on the floor, one is thin plywood, the other is thin fabric pads (those little circular shape, bought from the hardware store, for preventing furniture from scratching the floor). Both are not so rigid.
The metal frames of woofers are very calm, much more so then I'd expect. There's still a tad of very slight vibration, but really slight under normal SPL. On the baffle, by comparison, vibrations are very much largers, while smaller where near the woofer and larger towards the outer edges. It seems infinite numbers of cantilevers combined together and centered by the driver's frame. It's nearly still at the center (actually a ring here), and the amplitude of vibrations become larger and larger towards the outside.
Is this possible, or just my illusion? Touching the driver's frame and baffle at the same time by 2 fingers of one hand, i.e., in very short distance, their different amplitudes of vibration are still sensible. How amazing! I don't expect the baffle is THAT flexible.
I did this because I was thinking of enlarging the existing baffle holes and 'hanging' the woofers inside the hole, then covering the gaps by very compliant material (which I've not figured out, yet). This is to take advantage of both suspended driver and larger baffle area to support the LF more effectly.
It seems the baffle is loaded (excited) not only by directly mechanical contact, but also by the sound wave pressure. I just don't know how significant they are. Maybe it's possible the baffles are still vibrating as they were when I hang the woofer in the enlarged hole...
Any idea?
I don't have accelerometers or other instrument for this, only by fingers' touch. I found the vibrations were quite different on baffle suface and driver's frame. And also quite different in various locations on the baffles.
My woofers are secured on the baffles by screws and T-nut rigidly. Well, they should be rigid enough. Since no flexible gaskets/spacers or the likes are used. Metal frames contact plywood or MDF driectly, cramped by the screws and nuts.
The baffles have two kinds of feet to support them on the floor, one is thin plywood, the other is thin fabric pads (those little circular shape, bought from the hardware store, for preventing furniture from scratching the floor). Both are not so rigid.
The metal frames of woofers are very calm, much more so then I'd expect. There's still a tad of very slight vibration, but really slight under normal SPL. On the baffle, by comparison, vibrations are very much largers, while smaller where near the woofer and larger towards the outer edges. It seems infinite numbers of cantilevers combined together and centered by the driver's frame. It's nearly still at the center (actually a ring here), and the amplitude of vibrations become larger and larger towards the outside.
Is this possible, or just my illusion? Touching the driver's frame and baffle at the same time by 2 fingers of one hand, i.e., in very short distance, their different amplitudes of vibration are still sensible. How amazing! I don't expect the baffle is THAT flexible.
I did this because I was thinking of enlarging the existing baffle holes and 'hanging' the woofers inside the hole, then covering the gaps by very compliant material (which I've not figured out, yet). This is to take advantage of both suspended driver and larger baffle area to support the LF more effectly.
It seems the baffle is loaded (excited) not only by directly mechanical contact, but also by the sound wave pressure. I just don't know how significant they are. Maybe it's possible the baffles are still vibrating as they were when I hang the woofer in the enlarged hole...
Any idea?
Your observations give testimony to "compact mass" concept being worth some serious considering.
A speaker attached to a baffle that further has to transfers considerable energy to a dislocated mass (mother earth in the end) simply isn't the best we could think of.
This way there *always* is the "mass – spring problem" = bringing in the problem of *resonances* with dislocated masses.
The magnet structure of a loudspeaker could be considered to be fairly "compact mass" on the other hand – 100% impulse compensation – *no* resonance issue.
Thus its no surprise that a baffle less speaker on a swing has lowest coloration – there simply is nothing (of sufficient radiating area) to resonate – given the speaker itself is Ok.
Attaching a small rectangular baffle made of – say 6-10mm MDF – to the nude speaker to improve radiation pattern is a compromise that should do no serious harm.
A half-hearted solution in this same context was presented by NAIM on RMAF with the Ovator S600 – though to be fair – a boxed speaker is nothing to realise the "compact mass" concept easily.
Naim Audio
They suspended the tweeter and additionally suspended the whole speaker, though – at least as for the tweeter - at a relatively high resonant frequency.
Michael
A speaker attached to a baffle that further has to transfers considerable energy to a dislocated mass (mother earth in the end) simply isn't the best we could think of.
This way there *always* is the "mass – spring problem" = bringing in the problem of *resonances* with dislocated masses.
The magnet structure of a loudspeaker could be considered to be fairly "compact mass" on the other hand – 100% impulse compensation – *no* resonance issue.
Thus its no surprise that a baffle less speaker on a swing has lowest coloration – there simply is nothing (of sufficient radiating area) to resonate – given the speaker itself is Ok.
Attaching a small rectangular baffle made of – say 6-10mm MDF – to the nude speaker to improve radiation pattern is a compromise that should do no serious harm.
A half-hearted solution in this same context was presented by NAIM on RMAF with the Ovator S600 – though to be fair – a boxed speaker is nothing to realise the "compact mass" concept easily.
Naim Audio
They suspended the tweeter and additionally suspended the whole speaker, though – at least as for the tweeter - at a relatively high resonant frequency.
Michael
OK, lets get back on topic here....
I finally got up from my acoustically optimized Italian swivel chair... just had to try a baffle-less 21" woofer as well. Using a cargo strap, one 21" was hung in the same frame as the 8" and tweeter. I kept the other mounted in the baffle for comparison.
And the result?
Its amazing! There much more vibration with the baffle-mounted woofer! The entire baffle vibrates very much. The suspended woofer is not totally vibration-free, but much better. Its also standing firmly in place even at very large cone displacements.
I finally got up from my acoustically optimized Italian swivel chair... just had to try a baffle-less 21" woofer as well. Using a cargo strap, one 21" was hung in the same frame as the 8" and tweeter. I kept the other mounted in the baffle for comparison.
And the result?
Its amazing! There much more vibration with the baffle-mounted woofer! The entire baffle vibrates very much. The suspended woofer is not totally vibration-free, but much better. Its also standing firmly in place even at very large cone displacements.
...depends on *how* its held at the magnet - not so much that its held *at* the magnet.
Attach the magnet to a baffle - which is in a way a multiple resonant flat spring - and you get the same results as when attaching the basket to a baffle...
As usual loudspeaker baskets are stiff compared to a baffle this is pretty easy to predict - no?
As a side note - what is so obvious as a vibration that easily can be detected "by hand" may be less obvious but nothing less serious further up in frequency.
Michael
I had thought the baffle was temporarily out of the equation.
I was not talking about mounting the magnet to the baffle (!) I was talking about the difference between a baffle-less 21" driver being allowed to vibrate freely in reaction to the cone movement vs being held more or less rigid in space, by any one of a number of means - usually some variant on a slab of plywood with cutaways and a clamping system, with a tapered profile.
Ok- got it, you want a comparison of two close to ideal outcarried concepts!
- but as said -
"being held more or less rigid in space, by any one of a number of means"
is the general distinction between impulse compensation by local mass and *try* to overcome the kick back of mass spring systems.
To "held a speaker rigid in place" usually is meaning to force resonant frequency of the complete structure up veeeery high - far out of bandwidth to be more precise.
The effort to do so compared to the effort to 100% side step the whole issue (especially with OB speakers) is the beauty of "swinging speakers" to benefit from "Complete Impulse Compensation....
Michael
- but as said -
"being held more or less rigid in space, by any one of a number of means"
is the general distinction between impulse compensation by local mass and *try* to overcome the kick back of mass spring systems.
To "held a speaker rigid in place" usually is meaning to force resonant frequency of the complete structure up veeeery high - far out of bandwidth to be more precise.
The effort to do so compared to the effort to 100% side step the whole issue (especially with OB speakers) is the beauty of "swinging speakers" to benefit from "Complete Impulse Compensation....
Michael
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My open baffle speaker is no longer an open baffle speaker! Its just an open speaker.... with no baffle!
It works! It stands still, and there is NO vibration transfered to the wood frame holding the drivers. The hanging method is great!
The frame is 48x48 mm (2"x2") lumber with a 48x173 mm (2"x7") at the bottom. The corners are joined with steel angle brackets. Mids and tweeter are hung using small steel plates with holes in each end, and long screws attached to the driver frame. The woofer is hung in steel chains. I've used 10 mm steel bolts here, as you can see. The pictures should tell it all.
All drivers are balanced out so they hang strait, thats the reason for the long screws used here.
It works! It stands still, and there is NO vibration transfered to the wood frame holding the drivers. The hanging method is great!
The frame is 48x48 mm (2"x2") lumber with a 48x173 mm (2"x7") at the bottom. The corners are joined with steel angle brackets. Mids and tweeter are hung using small steel plates with holes in each end, and long screws attached to the driver frame. The woofer is hung in steel chains. I've used 10 mm steel bolts here, as you can see. The pictures should tell it all.
All drivers are balanced out so they hang strait, thats the reason for the long screws used here.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
