Another Hi-Fi holy cow put out to pasture . . .
- Thread starter Dougunn
- Start date
Daytons
clivem2
pfm Member
They do cancel hence 2 X 900W per channel though they work with 150W. They are even flat in that I don't need to equalise them low down. I use DSP but that's to fix my room modes.
It took me ages to dispense with concerns about action-reaction blunting transients but it doesn't. They simply don't move even with huge excursions....all the more huge due to cancellation. They are bloody heavy.
mattgbell
Help the elderly and unwell!
Am I seeing this right -- the two woofers are held together at a constant distance from one another by pins through the drivers' rims' screw holes but are suspended more or less freely from the frame?
Where did you get this idea from? (Not meaning to sound sceptical, just interested.)
clivem2
pfm Member
Yes you have that right. A pal of mine researched this, went into it on some forums about baffleless speakers. I simply replicated the design with my own mods.
Baffles sound coloured now...
mattgbell
Help the elderly and unwell!
So is part of the point that the cancellation of the two drivers means that the whole assembly doesn’t swing? Obviously a single hanging driver would swing quite a bit and the result would be a significant loss of energy.
Also having the two drivers pinned together like this makes for a symmetrical object that will hang vertically, which you can’t (easily) achieve with a single hanging driver.
Also having the two drivers pinned together like this makes for a symmetrical object that will hang vertically, which you can’t (easily) achieve with a single hanging driver.
Tony L
Administrator
I guess the way the drivers oppose/fire at each other in phase pressure-loads the gap between so cancellation may be less of an issue as the pressure wave will be sideways rather than in the direction of the cone movements, i.e. the pair are sucking/blowing air in/out from the gap between them. I don’t understand anything like enough speaker math (like any!) to be able to model this stuff in my head but it is a very interesting idea that will likely behave very differently to how I initially expected. I was just thinking of a big Tannoy or whatever out of a cab, which is hopeless, but this is logically entirely different.
PS How did you calculate or arrive at the gap between the drivers, is it a precise ratio or anything?
PS How did you calculate or arrive at the gap between the drivers, is it a precise ratio or anything?
clivem2
pfm Member
The drivers are out of phase which means the cones move in the same direction in this configuration. You'd think the drivers would pump in and out but no they don't. It may be the mass of the drivers vs the weight of the cone and voicecoil - spiders and magnets being so heavy means they don't move.
clivem2
pfm Member
Several sets have been made. I've just measured the gap on mine, it's 7cms. The gaps have varied for different versions from approx 4cms to 10cms without anything changing hugely. Yes you'd think the gap could be critical but luckily it's not too critical.
V
V2
Mullardman
Moderately extreme...
This is all fascinating stuff, especially clivem2's arrangement.. which I would love to hear, not least because it is very economical on space.
Ref the 'extreme' ones pictured. I'm really struggling with how anything approaching decent spls can be got from the smaller drivers at the top.. which aren't even in opposed pairs.
Re: The OP.. I'd have thought that something like a ball bearing on glass would de-couple, without introducing yet another set of resonant frequencies.. ( the wobble of the sorbothane) All you'd then need would be something to stop the things sliding off to their doom.. which rather points to the things pictured by cjarchez.. Or Tony's felt pads.
My own speakers are a two box floorstander. I did away with the little spikes between the 'main' speaker and the 'auxiliary bass' bit, by just using very thinly rolled out blu tack. I will be keeping the floor spikes though, as they provide a stable platform for a speaker with a small footprint on a thick carpet. The floor is bitumen.
Ref the 'extreme' ones pictured. I'm really struggling with how anything approaching decent spls can be got from the smaller drivers at the top.. which aren't even in opposed pairs.
Re: The OP.. I'd have thought that something like a ball bearing on glass would de-couple, without introducing yet another set of resonant frequencies.. ( the wobble of the sorbothane) All you'd then need would be something to stop the things sliding off to their doom.. which rather points to the things pictured by cjarchez.. Or Tony's felt pads.
My own speakers are a two box floorstander. I did away with the little spikes between the 'main' speaker and the 'auxiliary bass' bit, by just using very thinly rolled out blu tack. I will be keeping the floor spikes though, as they provide a stable platform for a speaker with a small footprint on a thick carpet. The floor is bitumen.
Colin L
High-tech low-life
Some Wilson Benesch speakers use reversd bass drivers in an isobaric configuration but they are front baffle mounted. How these work I have no idea. It seems a bit barmy, but Clive likes them then who I am to say otherwise. It would be interesting to hear and I would have thought they were dB limited. The cosmetics are “challenging”
DonQuixote99
pfm Member
It's always been clear to me that the idea is to prevent any vibrations coming from the speaker box (other than the radiation from the cone) from ever being heard, or from affecting, by any means, what the emitter is doing. I think this means they need to be absorbed by something, which I think means they should be turned into heat.
Spikes obviously transmit. Both ways, which might be quite ungood.
Spikes obviously transmit. Both ways, which might be quite ungood.
