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

[owdi]

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]

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

 

[davesaudio]

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]

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]

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]

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

 

[Ron E]

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]

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]

...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...