Hello Folks!
I am currently in the process of building an PR tuned enclosure.
After searching for available PRs it looks like the market is quite thin. But maybe there is another option?
How about using a active driver with nothing connected to the voice coil or maybe even with the Magnet and voice coil assembly removed as a PR?
It looks like many of the available PRs are already just normal available woofers with just the magnet and VC removed.
Let us take a look at this for example: PURIFI PTT6.5PR-NF1-01 vs PURIFI PTT6.5X08-NFA-01
The PR very much looks like it uses the exact same parts as the actual woofer. However it somehow doesnt add up.
Qms and Qmpr should be exactly the same as these values are just related to the mechanics, same for Vas / Vapr.
Vas is almost the same on these, but Qmpr is much higher than Qms?
Xmax is different but this makes sense as the active chassis is likely limited by the voice coil leaving the magnet field vs the PR is only limited by the suspension.
If we take a different manufacturer it gets even worse:
So whats going on here? Are they using different materials for the suspension to get different characteristics? Is the voicecoil influencing anything?
Lets say we need a PR, can we just use a Dayton DSA175-8 instead of a PR and get the same performance if we remove the magnet?
Or the other way around: can we use a cheap woofer, remove the magnet and voicecoil and it will act with the same Qms / Vas when used as a PR?
Is my logic incorrect that removing the VC shouldnt influence Qms and Vas at all? I can only imagine that Qms would increase slightly because some eddy currents could be removed when the VC + former dont have a magnet fields around them.
Could this also increase Vas as it results in less "breaking" while moving?
I am currently in the process of building an PR tuned enclosure.
After searching for available PRs it looks like the market is quite thin. But maybe there is another option?
How about using a active driver with nothing connected to the voice coil or maybe even with the Magnet and voice coil assembly removed as a PR?
It looks like many of the available PRs are already just normal available woofers with just the magnet and VC removed.
Let us take a look at this for example: PURIFI PTT6.5PR-NF1-01 vs PURIFI PTT6.5X08-NFA-01
| PURIFI PTT6.5PR-NF1-01 | PURIFI PTT6.5X08-NFA-01 | |
| Vapr / Vas | 26,2L | 26,4L |
| Qmpr / Qms | 10,9 | 6,6 |
| Cmpr /Cms | 1,05mm/N | 1,06mm/N |
| Xmax | 15mm | 10mm |
The PR very much looks like it uses the exact same parts as the actual woofer. However it somehow doesnt add up.
Qms and Qmpr should be exactly the same as these values are just related to the mechanics, same for Vas / Vapr.
Vas is almost the same on these, but Qmpr is much higher than Qms?
Xmax is different but this makes sense as the active chassis is likely limited by the voice coil leaving the magnet field vs the PR is only limited by the suspension.
If we take a different manufacturer it gets even worse:
| Dayton DSA175-PR | Dayton DSA175-8 | |
| Vapr / Vas | 26,9L | 18.7L |
| Qmpr / Qms | 4.30 | 1.66 |
| Cmpr /Cms | 1.15 mm/N | 0.71 mm/N |
| Xmax | 8 mm | 5.3 mm |
| Dayton Audio Epique E180HE-PR | Dayton Audio Epique E180HE-44 | |
| Vapr / Vas | 12,52 | 16,15L |
| Qmpr / Qms | 3.5 | 2,93 |
| Cmpr /Cms | 0.48 mm/N | 0.61 mm/N |
| Xmax | 19 mm | 14,7 mm |
So whats going on here? Are they using different materials for the suspension to get different characteristics? Is the voicecoil influencing anything?
Lets say we need a PR, can we just use a Dayton DSA175-8 instead of a PR and get the same performance if we remove the magnet?
Or the other way around: can we use a cheap woofer, remove the magnet and voicecoil and it will act with the same Qms / Vas when used as a PR?
Is my logic incorrect that removing the VC shouldnt influence Qms and Vas at all? I can only imagine that Qms would increase slightly because some eddy currents could be removed when the VC + former dont have a magnet fields around them.
Could this also increase Vas as it results in less "breaking" while moving?
Some properties of an active voice coil also influence Qms, e.g. eddy currents, as far as I know.
So Qmpr is not equal Qms of a connected voice coil.
Have a look at alexander gessler's explanation (scroll down for use of normal drivers as PR):
https://www.donhighend.de/?page_id=8581
you can use an active woofer as PR as long as the voice coil stays unconnected (otherwise the PR gets very lossy). a PR should have as soft suspension as possible as low loss as possible. needs more mass than the woofer to tune low.
... Is weight a part of the equation?
Most PR's have extra mass to provide a proper load effect in relation to suspension resistance at FS, the electrical resistance of the voice coil and the magnetic field is taken out of the equation and is being replaced with a specific mass, of course that would inevitably change the physical response of the mechanical compliance.
But I have no idea about these things, just thinking out loud.
Most PR's have extra mass to provide a proper load effect in relation to suspension resistance at FS, the electrical resistance of the voice coil and the magnetic field is taken out of the equation and is being replaced with a specific mass, of course that would inevitably change the physical response of the mechanical compliance.
But I have no idea about these things, just thinking out loud.