Lighter woofer cones will bring down the force on the cabinet, but will tend to make the cone less stable and limit how well it performs at its upper edge. I find most woofers fail my performance expectations at the upper edge so I have found that heavier cones are a necessity n this regard. If one could make a light cone that was well behaved then great, but this tends to not be the case.
In my experience the cabinet re-radiation concern is over-blown. It can be an issue in a poorly design system, but need not be an issue at all.
I use heavy coned woofers, but also very thick (about 2") well damped (CLD) baffles, so the reactive force is not such an issue.
In my experience the cabinet re-radiation concern is over-blown. It can be an issue in a poorly design system, but need not be an issue at all.
I use heavy coned woofers, but also very thick (about 2") well damped (CLD) baffles, so the reactive force is not such an issue.
Just curious, how much of the motor force in a woofer is to push the cone, vs. the air? I've never done the math.
A racecar analogy should include ACTIVE suspension, since the woofer cone is actively driven directly by an amplifier and not just along for the ride.
Not what I meant... we do not drag the cones over bumps do we?
The amp pushes the cone, it's the weight of the cone compared to the weight of the enclosure, that's being compared to the weight of the wheel/brake assembly + part of the shock absorbers vs the rest of the car (body engine, basically everything else).
The amplifier should be considered able to make the cone move, it's the forces of the moving mass, as in the picture of the article I linked, that's under comparison.
The amp would be the road, (the wheel follows the road as the cones follow the amp signal) but that makes it a weird comparison
.
Fairly important point ...
The radiation mass is highly complex and not actually a pure mass as its value is frequency dependent. It varies with cone area as well. At its peak it could be a few grams, not a major addition, but not irrelevant either.
To me its not the reactive force of the entire cabinet against the cone mass - as it would be at very low frequencies - but the structural vibrations that get into the cabinet walls through the frame of the driver - mostly by the reactive force of the magnet against the voice coil. All these forces are very different things. The former I would tend to ignore, but the later is worth looking into. Adding mass to the enclosure via a top load only affects the former. It does very little to the later.
For example, I saw a large improvement in my speaker responses when I used a low mass woofer (neo.) The cone mass did not change, but the magnets reactive force on the cabinet through the frame would have been substantially reduced.
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I know what you mean, wesayso. But I want my racecar analogy to have an obvious active component other than the road, or else the analogy falls apart....?
Not completely, at least, it would depend on what we are comparing... I try to leave the enclosure walls re-radiating out of this equation. We're putting a heavy object on the enclosure, I'm not even 'considering' the difference in tension that the added weight would apply to the enclosure walls. Just moving mass vs the enclosure, and how it's placed on the floor etc... For instance, I don't use spikes. I use industrial damping feet.
I want my speakers to have an active suspension, that's why I use FIR filters (lol). Or would that be considered launch control....
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I think you are forgetting the moving mass is not moving in a vacuum - it is the moving mass + the mass of the air (not a lot) + the force it takes to increase the air pressure (and decrease) to the level it does by displacing that volume of air in that time.
The volume is not much and the pressure may not be much BUT because F=MA and the pressure increase is a cubic factor in this which effectively adds a restive force to the equation it would be something like this:
Fd=(Mc+Ma+(Some function of kPa cubed))*A
Fd = force driver exerts
Mc = mass of cone
Ma = Mass of air
Please dont stamp all over this valiant effort - Im dragging this up, with brain damage, from an A level 27 years ago- LOL. If im talking **** brake it to me gently 🙂
The volume is not much and the pressure may not be much BUT because F=MA and the pressure increase is a cubic factor in this which effectively adds a restive force to the equation it would be something like this:
Fd=(Mc+Ma+(Some function of kPa cubed))*A
Fd = force driver exerts
Mc = mass of cone
Ma = Mass of air
Please dont stamp all over this valiant effort - Im dragging this up, with brain damage, from an A level 27 years ago- LOL. If im talking **** brake it to me gently 🙂
Let's generalize as much as possible. If I double the total mass of cabinet+woofer, then the reaction to the cone in the cabinet+woofer is halved. That's instructive. Now it's a question of where to place that extra mass for it to be most effective.
Maybe all the addded mass should go on the woofer and magnet?
Maybe some on the woofer and some in the baffle?
Does the woofer benefit from a gasket to better distribute the forces into the baffle?
Does added mass anywhere on the cabinet help?
Maybe all the addded mass should go on the woofer and magnet?
Maybe some on the woofer and some in the baffle?
Does the woofer benefit from a gasket to better distribute the forces into the baffle?
Does added mass anywhere on the cabinet help?
You've also radically changed the baffle diffraction and frequency response of the tweeter. I suggest that *this* is the cause of what you hear.
By doing that you are subjecting all the reactive forces to just the basket (at least above the corner frequency of the compliance -- do the match to see how large that would need to be to be effective at a low frequency) increasing the problems.
dave
dave
Would you agree that the moving mass + air would be the same between the speaker without the granite tiles and with them? I am being gentle, right? 🙂
So what does change....
The weight in the part that stands still.
The pressure/tension the weight creates on the walls that carry it
The baffle size due to the extension the pile of tiles add
What feet are on the speakers, the weight will affect the coupling to the floor.
Any more?
Here's an idea, do you have a measurement setup? We could look for differences....
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Yes - im only talking about calculating the true force the driver cone is actually imparting as it fires (say) outwards. Nothing else
I don not have a measurement set up - BUT if anyone can tell me how it can be achieved with the kit available 1 imac, 1 iphone 6, 1 ipad pro ill very happily measure it & I dont mind buying say a microphone for a few $$
Does the size of the baffle truly increase in the way we think of a baffle? the block is solid, it can not flex and impart additional unwanted elements from within like the speaker baffle its self.
However (and I know this is moving off topic), What i have been thinking for a while is "why dont we 3D print speaker cabinets" - ok a 1m3 3D printer is $50k, that aside - the polymers used can now be of structural grade, you can have truly unlimited triangulated "nano-bracing" connecting any point on the cabinet to any number of other points, there is no restriction on the shape due to manufacturing constraints. You could make it in wax and then cast it in say Magnesium alloy through the lost wax process or in resin with vacuum infusion.
I don not have a measurement set up - BUT if anyone can tell me how it can be achieved with the kit available 1 imac, 1 iphone 6, 1 ipad pro ill very happily measure it & I dont mind buying say a microphone for a few $$
Does the size of the baffle truly increase in the way we think of a baffle? the block is solid, it can not flex and impart additional unwanted elements from within like the speaker baffle its self.
However (and I know this is moving off topic), What i have been thinking for a while is "why dont we 3D print speaker cabinets" - ok a 1m3 3D printer is $50k, that aside - the polymers used can now be of structural grade, you can have truly unlimited triangulated "nano-bracing" connecting any point on the cabinet to any number of other points, there is no restriction on the shape due to manufacturing constraints. You could make it in wax and then cast it in say Magnesium alloy through the lost wax process or in resin with vacuum infusion.
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Now thats a little bit outside my level of understanding for me to comment on without just making most of it up.
BUT what i would add is the difference is pretty identical with the tweeter mounted as before in the cabinet as it is mounted on the granite block up top.
2nd. Most of the change happens in the frequency the woofer handles
I am sure there are many many variables that come into play here and im sure it could be refined significantly more but can i just suggest someone else gives it a try. It costs about $10.
There is always the possibility that it corrects a design flaw in MY speakers and for everyone else it makes no difference or even makes things worse.
I know that My Wilson Benesch Square 2's - for what is it $8k or $9k have some serious issues eg.
Aluminum fixings to plinth fatigue and crumble
Crossover directly above shielded Neodinium Boron Fe magnet suffers terrible Microphony (sp)
Play with this diffraction simulator and you'll see the difference: Home of the Edge Model both the woofer and tweeter and you'll see the differences would be considerable, definitely audible, so you can't rule out this variable.
Fairly easy to test. Put a second speaker box on top of the cabinet instead of the granite and see if it sounds the same as the speaker on its own.
I'll give that a go - give me 15 mins, I happen to have one in the other room that will sit atop nicely.
These guys are NOT talking about "max bass sound". Their concept is that the decoupling is REDUCING "false low frequencies".
I have some heavy old fans, like the one pictured, and it is sometimes very striking how much buzz and "false low frequencies" various stands / pieces of furniture can add to their operating noise.
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