Can I cut a hole in the spider of my passive radiator?

owdi · 10th October 2004, 11:59 PM

So I'm a moron. Instead of making the trip to a hobby store for modeling clay I used bathtub sealant to add mass to my passive radiator. I thought it cured overnight, but it didn't. Now I have a bunch of sticky sealant soaked into a part of the spider of the PR.

I picked out as much as I could, but there is no way to get it all. There is a 1/8" thick layer over 1/6th of the spider. Can I cut this out? I realize it will change the behavior of my passiver radiator, but I think I can work around it. If I position the PR so the cut-out portion is on the bottom, I don't think there will be a problem with the cone staying centered.... even after I add about 1.5lbs of mass.

Will removing some of the spider lower the fs of the PR? If so I would need less mass to get the tuning frequency I want....

What do you guys think?

... and yes, I know I can get a new spider from Adire. I'll do that eventually.... just looking for a short term solution, if there is one.

Dan

catapult · 11th October 2004, 12:18 AM

While I haven't seen it, I'd think leaving the gunk on would be better than cutting holes.

davesaudio · 11th October 2004, 04:21 AM

seeing as there used to be passives made without anything but the surround I think it won't be a problem to cut a bit out

owdi · 11th October 2004, 08:56 PM

catapult - I can't leave it on because the gunk is slowly hardening, limiting the output of the PR. One nice side effect is that it behaves as if the vas of the PR was cut in half, alowing me to tune really low (24hz) with 200mg of mass (instead of 800mg).

davesaudio - good to hear, I'll go to town with a razor blade tonight!

On a side note (don't want to start a new thread), can someone offer some input on using a PR in a 4th order bandpass? Any advantages over a typical PR application?

Dan

Vikash · 11th October 2004, 09:42 PM

It is difficult to judge the best course of action without seeing it. Based on my impression of it, I absolutely wouldn't cut a hole in the PR spider. 1/6th as a lot. How do you know that the VAS is cut into half? If the PR stiffens then I would imagine that fs reduces and acts as if you've added weight to it anyway.

My input would be to leave it as is until you have a chance to replace the PR.

mg?

m4dm4n · 11th October 2004, 10:09 PM

owdi i'm testing an hybrid 6th bandpass box with ports and slaves

Ron E · 11th October 2004, 10:51 PM

I bet if you drove it near resonance for a while (after it hardens) some of it would fall off anyway. or loosen so you can peel it off.. The spider is pretty strong, and most caulk/sealant is not. Beware of VC heating if you drive at resonance, because the VC isn't moving much.....

Stiffening the PR suspension will raise resonance and increase the mass you must add.... Removing all or part of the spider could cause the assembly to rock and that could damage things more than just leaving it as it is.

owdi · 12th October 2004, 02:39 AM

Well I've run some tests after scraping even more of the crap off the spider and it looks like it's OK for now. The bathtub sealant appears to have dampened the spider somehow, because I still get really really low tuning for the amount of mass I add to the PR. In my book that is a good thing

Maybe I found a new alternative to mass loading PRs!!! hehe

I'll just leave it as-is, I can test the resonance frequency in about five seconds flat, so I'll know if it ever wanders up.

Dan

davesaudio · 12th October 2004, 01:05 PM

...another Dan from bellingham who builds speakers....
and you have a friend named dave and
do sonar stuff for a living?
- first reaction to the post was that wiggins was having one over on us...

10th October 2004, 11:59 PM	#1
owdi diyAudio Member Join Date: Sep 2003 Location: Bellevue, WA	Can I cut a hole in the spider of my passive radiator? So I'm a moron. Instead of making the trip to a hobby store for modeling clay I used bathtub sealant to add mass to my passive radiator. I thought it cured overnight, but it didn't. Now I have a bunch of sticky sealant soaked into a part of the spider of the PR. I picked out as much as I could, but there is no way to get it all. There is a 1/8" thick layer over 1/6th of the spider. Can I cut this out? I realize it will change the behavior of my passiver radiator, but I think I can work around it. If I position the PR so the cut-out portion is on the bottom, I don't think there will be a problem with the cone staying centered.... even after I add about 1.5lbs of mass. Will removing some of the spider lower the fs of the PR? If so I would need less mass to get the tuning frequency I want.... What do you guys think? ... and yes, I know I can get a new spider from Adire. I'll do that eventually.... just looking for a short term solution, if there is one. Dan

11th October 2004, 04:21 AM	#3
davesaudio diyAudio Member Join Date: Feb 2003 Location: GTA	seeing as there used to be passives made without anything but the surround I think it won't be a problem to cut a bit out __________________ intentionally blank

11th October 2004, 09:42 PM	#5
Vikash diyAudio Moderator Emeritus Join Date: May 2003 Location: UK	It is difficult to judge the best course of action without seeing it. Based on my impression of it, I absolutely wouldn't cut a hole in the PR spider. 1/6th as a lot. How do you know that the VAS is cut into half? If the PR stiffens then I would imagine that fs reduces and acts as if you've added weight to it anyway. My input would be to leave it as is until you have a chance to replace the PR. mg? __________________ "The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)

11th October 2004, 10:51 PM	#7
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	I bet if you drove it near resonance for a while (after it hardens) some of it would fall off anyway. or loosen so you can peel it off.. The spider is pretty strong, and most caulk/sealant is not. Beware of VC heating if you drive at resonance, because the VC isn't moving much..... Stiffening the PR suspension will raise resonance and increase the mass you must add.... Removing all or part of the spider could cause the assembly to rock and that could damage things more than just leaving it as it is. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

12th October 2004, 01:05 PM	#9
davesaudio diyAudio Member Join Date: Feb 2003 Location: GTA	...another Dan from bellingham who builds speakers.... and you have a friend named dave and do sonar stuff for a living? - first reaction to the post was that wiggins was having one over on us... __________________ intentionally blank


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11th October 2004, 12:18 AM	#2
catapult diyAudio Member Join Date: Dec 2002 Location: Planet Earth	While I haven't seen it, I'd think leaving the gunk on would be better than cutting holes.

11th October 2004, 08:56 PM	#4
owdi diyAudio Member Join Date: Sep 2003 Location: Bellevue, WA	catapult - I can't leave it on because the gunk is slowly hardening, limiting the output of the PR. One nice side effect is that it behaves as if the vas of the PR was cut in half, alowing me to tune really low (24hz) with 200mg of mass (instead of 800mg). davesaudio - good to hear, I'll go to town with a razor blade tonight! On a side note (don't want to start a new thread), can someone offer some input on using a PR in a 4th order bandpass? Any advantages over a typical PR application? Dan

11th October 2004, 10:09 PM	#6
m4dm4n diyAudio Member Join Date: Oct 2004	owdi i'm testing an hybrid 6th bandpass box with ports and slaves

12th October 2004, 02:39 AM	#8
owdi diyAudio Member Join Date: Sep 2003 Location: Bellevue, WA	Well I've run some tests after scraping even more of the crap off the spider and it looks like it's OK for now. The bathtub sealant appears to have dampened the spider somehow, because I still get really really low tuning for the amount of mass I add to the PR. In my book that is a good thing Maybe I found a new alternative to mass loading PRs!!! hehe I'll just leave it as-is, I can test the resonance frequency in about five seconds flat, so I'll know if it ever wanders up. Dan

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