Has anyone tried?
Just an idea, I mean using two PRs in clamshell.
Might sound silly but that might be the only way in my case.
For a very small enclosure, think micro sub.
A sort of truncated cone, so the only place for the PR is the big diameter, that is two times larger.
The PRs I tried were not good enough, and adding enough mass might just kill it (I only tried the reasonable prices).
I imagine it would half the Vas, just like for a regular driver.
But would it impact Qms as well, like doubled?
This way I could add enough mass since it would be shared.
This is just theoretical, I have drivers in mind (mostly TB W3, isobaric too) but many other directions to go with.
Goal is more about the fun and the look of the sub than the best SQ.
And currently no access to WinISD so I do all my sims online, a bit cumbersome and probably faulty.
So far in sims it looks to work well with only Vas halved.
Just an idea, I mean using two PRs in clamshell.
Might sound silly but that might be the only way in my case.
For a very small enclosure, think micro sub.
A sort of truncated cone, so the only place for the PR is the big diameter, that is two times larger.
The PRs I tried were not good enough, and adding enough mass might just kill it (I only tried the reasonable prices).
I imagine it would half the Vas, just like for a regular driver.
But would it impact Qms as well, like doubled?
This way I could add enough mass since it would be shared.
This is just theoretical, I have drivers in mind (mostly TB W3, isobaric too) but many other directions to go with.
Goal is more about the fun and the look of the sub than the best SQ.
And currently no access to WinISD so I do all my sims online, a bit cumbersome and probably faulty.
So far in sims it looks to work well with only Vas halved.
PR does not reduce required box size. If you want small sub, think micro sub, use two real woofers in isobaric.
Thx adason,
Yes I know and I don’t want to reduce the box size here (for this I ‘d use isobaric sub mount), but I’m looking out for a « stronger » PR.
I mean a PR that would behave close to a bigger one, in term of Vas, and ability to take more mass.
Thus the similarity in using the term isobaric for the PR as well.
In sims so far, by just halving the Vas of one PR only, it gets better.
- So would two PRs halve the Vas of just using one? (face to face mount, minimal volume in between)
I can't add mass on my sims but IRL I would sure play with it to lower the Fs
- but will they then share the added weight?
Yes I know and I don’t want to reduce the box size here (for this I ‘d use isobaric sub mount), but I’m looking out for a « stronger » PR.
I mean a PR that would behave close to a bigger one, in term of Vas, and ability to take more mass.
Thus the similarity in using the term isobaric for the PR as well.
In sims so far, by just halving the Vas of one PR only, it gets better.
- So would two PRs halve the Vas of just using one? (face to face mount, minimal volume in between)
I can't add mass on my sims but IRL I would sure play with it to lower the Fs
- but will they then share the added weight?
Isobaric means equal pressure.
Two driver motors driving two cones in a clamshell arrangement are "isobaric", the volume of air between the drivers is more or less under equal pressure.
The force driving an interior clamshell PR would come from the pressure in the cabinet, slapping the inner PR cone against the outer cone, then create a partial vacuum between the two on the return, "sucking" the outer PR cone back in until it slaps against the interior cone as it is driven on the next cycle.
If the PR cones are separated far enough to not slap into each other, the compression and rarefaction of the air between would waste much of the energy- the outer cone would not move in phase with the inner.
As well as the slapping noise and wasted energy aspect, the displacement of the pair is only that of one PR, and the PR displacement should be double the driven isobaric pair.
Two driver motors driving two cones in a clamshell arrangement are "isobaric", the volume of air between the drivers is more or less under equal pressure.
The force driving an interior clamshell PR would come from the pressure in the cabinet, slapping the inner PR cone against the outer cone, then create a partial vacuum between the two on the return, "sucking" the outer PR cone back in until it slaps against the interior cone as it is driven on the next cycle.
If the PR cones are separated far enough to not slap into each other, the compression and rarefaction of the air between would waste much of the energy- the outer cone would not move in phase with the inner.
As well as the slapping noise and wasted energy aspect, the displacement of the pair is only that of one PR, and the PR displacement should be double the driven isobaric pair.
I haven't tried it, but I think your analysis is correct.
Art (Weltersys) correctly points out that there will be problems with the PR diaphragms hitting each other. This could be overcome by mechanically joining the diaphragms, which would allow the PR weights to be distributed across 2x suspensions. ie, less likely to become damaged from adding lots of weight to only one PR>
The ratio of cone areas between active driver and passive radiator still needs to be about 1:2, though, so you'll still need to make sure that works. Otherwise, you'll end up over-driving your PR(s), which results in a lot of distortion.
Chris
Omg I completely missed this part Weltersys thanks, of course without the motor to move them in sync it would rely on pressure/suction and would be messy!
Unless... I can fill the gap with liquid, with the right mass, silly 😛
Joining them mechanically is interesting Chris, back to back should be easy through their threaded parts.
But total volume would increase too much (in my case).
Front to front maybe, probably a too precise job for me.
Ok I think I just need to check better PR, the Purifi looks already better.
Thx all!
Unless... I can fill the gap with liquid, with the right mass, silly 😛
Joining them mechanically is interesting Chris, back to back should be easy through their threaded parts.
But total volume would increase too much (in my case).
Front to front maybe, probably a too precise job for me.
Ok I think I just need to check better PR, the Purifi looks already better.
Thx all!
You could always clamshell the PRs and remove the dustcaps or bore through them to sandwich the threaded rod.