GDay!
I've got a couple of my favourite 10in drivers that have distorted coil formers due to "excess enthusiasm".
Could I remove the magnets and use them as a pair of PR's?.
If so I would build a single driver / dual PR box.
A frequency sweep should identify the tuning frequency, and thus the apparent mass of the PRs. From there it should be easy to work out how much mass to add to get the desired tuning frequency.
Has anyone been down this road before...?
Collo
I've got a couple of my favourite 10in drivers that have distorted coil formers due to "excess enthusiasm".
Could I remove the magnets and use them as a pair of PR's?.
If so I would build a single driver / dual PR box.
A frequency sweep should identify the tuning frequency, and thus the apparent mass of the PRs. From there it should be easy to work out how much mass to add to get the desired tuning frequency.
Has anyone been down this road before...?
Collo
Hi,
its certainly possible. I've used 2 blown 8"s with 2 6.5"s.
UK 2p coins hapened to fit perfectly into the voice coil, and superglued
into place near the suspension point were used to adjust mass.
It was a bit rough and ready but one 2p seemed to work well for
a overlarge sealed cabinet the owner had built for a 6.5" driver.
/sreten.
its certainly possible. I've used 2 blown 8"s with 2 6.5"s.
UK 2p coins hapened to fit perfectly into the voice coil, and superglued
into place near the suspension point were used to adjust mass.
It was a bit rough and ready but one 2p seemed to work well for
a overlarge sealed cabinet the owner had built for a 6.5" driver.
/sreten.
Yes, I've done it a few times. The trick is to get old woofers with a fair amount of excursion, nice big spider etc.
Paint the backs of the cones with a few coats of PVA glue to stiffen. (Assuming they are paper)
Add weight (can be glue) to the inside of the dust cap from the back. This will also help to seal the cap if not solid.
Plug the hole in the voice coil if it is still attached.
If your old drivers are not high excursion then lower the ratio of active to drone ie: one 8" or 10" active with two 10" drones. It'll work like a charm.
Paint the backs of the cones with a few coats of PVA glue to stiffen. (Assuming they are paper)
Add weight (can be glue) to the inside of the dust cap from the back. This will also help to seal the cap if not solid.
Plug the hole in the voice coil if it is still attached.
If your old drivers are not high excursion then lower the ratio of active to drone ie: one 8" or 10" active with two 10" drones. It'll work like a charm.
Thanks for those encouraging replies.
When I model PRs in WinISD, it asks for some T/S parameters for the PR. As mass is added, it shows the new Fs
Qms.....same as original driver?
Xmax.....same as original driver..maybe more with the pole piece removed??
Sd.....same as original driver
Vas
Fs
Does anyone know if the Vas and starting Fs (no mass added) are also the same as the original driver, or whether these have to be determined experimentally?
When I model PRs in WinISD, it asks for some T/S parameters for the PR. As mass is added, it shows the new Fs
Qms.....same as original driver?
Xmax.....same as original driver..maybe more with the pole piece removed??
Sd.....same as original driver
Vas
Fs
Does anyone know if the Vas and starting Fs (no mass added) are also the same as the original driver, or whether these have to be determined experimentally?
Collo said:
Hi Collo
I'd punt on them being the same as I had a look at the Peerless XLS drivers and PR is identical to the motored woofer but without the motor and it's the added weight 400-425g that has changed the Fs and Vas.... but I could be wrong.
Is the starting mass to add equivalent to the weight of air that would be in a port with the diameter = effective cone diameter? I'd like to know as this looks worthwhile to play with to use up those busted drivers.
Hi there Rabbitz,
Thanks for that comparo on the Peerless gear. I'll push on assuming that the T/S are the same.
The finishing mass (with the mass added) is equivalent to the mass of air in an equivalent port
WinISD pro lets you choose PR's when you're first setting up the project and choose the box type. The parameters for the PR are entered and later you can change the added mass on the PR tab. This saves you having to do the calculations manually.
I'm looking at around 230g to add. One method to add mass, is to use some lead shot mixed with epoxy, and pour it into the coil former - a bit permanent though. For experimenting, a hot glue gun and some lead washers might be a better bet.
Here's my project file using the Jaycar Titanium 10inch drivers:
http://www.users.bigpond.com/bcolliso/winisd-projects/my-pr-design.wpr
(save it to a temporary file and then open it. For some reason it doesn't load correctly direct from the web)
Thanks for that comparo on the Peerless gear. I'll push on assuming that the T/S are the same.
The finishing mass (with the mass added) is equivalent to the mass of air in an equivalent port
WinISD pro lets you choose PR's when you're first setting up the project and choose the box type. The parameters for the PR are entered and later you can change the added mass on the PR tab. This saves you having to do the calculations manually.
I'm looking at around 230g to add. One method to add mass, is to use some lead shot mixed with epoxy, and pour it into the coil former - a bit permanent though. For experimenting, a hot glue gun and some lead washers might be a better bet.
Here's my project file using the Jaycar Titanium 10inch drivers:
http://www.users.bigpond.com/bcolliso/winisd-projects/my-pr-design.wpr
(save it to a temporary file and then open it. For some reason it doesn't load correctly direct from the web)
I did wonder about that.
A little research with Google......
A project used a Peerless 10in PR with a mass of 400g plus another 200g added
http://www.hardwareanalysis.com/content/article/1789.5/
A Dayton 12in PR sold by Parts Express lists the cone mass to be 145g and a maximum total of 1200g.
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-192&ctab=12#Tabs
It's suspension looks similar to the driver I'm modifying, so hopefully it will cope.
A little research with Google......
A project used a Peerless 10in PR with a mass of 400g plus another 200g added
http://www.hardwareanalysis.com/content/article/1789.5/
A Dayton 12in PR sold by Parts Express lists the cone mass to be 145g and a maximum total of 1200g.
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-192&ctab=12#Tabs
It's suspension looks similar to the driver I'm modifying, so hopefully it will cope.
It really depends on the construction.
The driver I'm playing with had the magnet glued and screwed onto the frame. The only way to undo the screws would have been to remove the cone, and I was woried that the spyder, which was glued into place would be damaged.
Since the frame was pressed steel, an old chisel worked well to cut the magnet off. - see attached pic....
The ragged edge left on the frame was cleaned up with some shears.
Had the frame been cast, a hacksaw would have been needed, resulting in a lot of metal dust, which would have gotten into the spyder.
Some grease would have fixed this, but getting it out again would need solvents that could damage other parts. Perhaps a water based gunk of some sort. Decisions, decisions.....
Regarding the added weight - I also felt that it was asking a bit much, although the suspension is quite stiff - Qms=8.2
I'm making a glue-on flange with a bolt, so I can experiment. Total cost so far= zero, so I'm not too worried
The driver I'm playing with had the magnet glued and screwed onto the frame. The only way to undo the screws would have been to remove the cone, and I was woried that the spyder, which was glued into place would be damaged.
Since the frame was pressed steel, an old chisel worked well to cut the magnet off. - see attached pic....
The ragged edge left on the frame was cleaned up with some shears.
Had the frame been cast, a hacksaw would have been needed, resulting in a lot of metal dust, which would have gotten into the spyder.
Some grease would have fixed this, but getting it out again would need solvents that could damage other parts. Perhaps a water based gunk of some sort. Decisions, decisions.....
Regarding the added weight - I also felt that it was asking a bit much, although the suspension is quite stiff - Qms=8.2
I'm making a glue-on flange with a bolt, so I can experiment. Total cost so far= zero, so I'm not too worried
Attachments
Collo
Did some modelling with the driver here and came out worse than vented.... so the port stays and the PR idea gets the flick.
I ended up getting a motor assembly off one sub woofer (B&W) a while back by using wedges between the motor assembly and steel basket. The fasteners just pulled through the holes as easy as.
With driver I was going to use for a PR, the cast basket was going to be cut between the spider and the motor.
Did some modelling with the driver here and came out worse than vented.... so the port stays and the PR idea gets the flick.
I ended up getting a motor assembly off one sub woofer (B&W) a while back by using wedges between the motor assembly and steel basket. The fasteners just pulled through the holes as easy as.
With driver I was going to use for a PR, the cast basket was going to be cut between the spider and the motor.
Attachments
I've turned a few blown speakers in to PR's...
I usually just find an acceptable box volume via winISD and then tune the PR by adding mass until I find it's f3 to be acceptable.
It might effect longevity adding all that mass, but a blown speaker has no longevity to begin with, so you're not losing much
I usually just find an acceptable box volume via winISD and then tune the PR by adding mass until I find it's f3 to be acceptable.
It might effect longevity adding all that mass, but a blown speaker has no longevity to begin with, so you're not losing much
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