Reattaching whizzers to Hemp FR8 - diyAudio
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Old 19th May 2008, 10:16 PM   #1
nodiak is offline nodiak  United States
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Default Reattaching whizzers to Hemp FR8

Questions:
What adhesive to use? Seems like a tiny line of silicone would work. They used something black, like on small Fostex I've seen. Don't know if harder or softer adhesive is best for them to produce treble.
Does the whizzer need to touch vc? At present the whizzer "apex" is smaller than vc circumference. So they need trimmed, will lose maybe 2-3 mm in wh height to get the opening to fit on the outside edge of the vc which sticks up ~ 1mm (which provides an attachment point and a dam for adhesive to settle in).

My hope is to repair the drivers so I can EnABL them. But I would have to use phase plugs, unlike Buds example.

My "Don't Do This" story time: A while back I decided to remove the dustcaps and put in phase plugs. In the process the whizzer came off with the dustcap - as it is attached to dustcap. At one point I pulled juuuussst a little bit instead of cutting, lifting the wh with the dc. I went with it at the time thinking I would try them whizzerless with tweeters, as I wasn't too pleased with the treble anyway. So they went on the to-do shelf...for a long time.
Well, without whizzers they beam like a flashlight. I worked with it a little bit trying to xo to tweeters. Closest I came was using dome tweet in waveguide ala Zaph. Potential there, but I feel the FR8 still beams even with 2 mH coil.
So GM or someone must know if whizzered drivers normally beam without wh's. And if it's the cone profile or...what causes it?
Don
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Old 24th August 2009, 04:54 AM   #2
col is offline col  Australia
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Interesting.... I was considering removing the whizzers from my FR8C and going with a small compression driver and horn above 6khz. Maybe I'll leave them alone.

cheers,
col.
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Old 24th August 2009, 05:07 AM   #3
CLS is offline CLS  Taiwan
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I think the whizzer should be attached to the VC former as rigid as possible.

On those I've cut, the whizzers touch VC former directly, and the glue is applied on the side where they contact. And the glue is very hard. (maybe some kind of epoxy or other 2-part adhesives... )

If soft adhesive is used, in the frequency range it's supposed to operate, I think the whizzer can not move simultaneously with the VC.
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Old 24th August 2009, 06:02 AM   #4
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The only set of FR8C i did a dustcapectomy to lost the whizzers. They were already damaged thou, so we didn't take too much care with there attachment. The Wild Burros -- also made by Misco -- have similar potential to loss whizzers when dust caps are removed. On the one pair of those i have done, the 1st whizzer partly came off, i reattached it with PVA (modpodge). On the second one i was even more careful and it stayed put.

Optimally the whizzer attaches directly to the voice coil.

The black stuff is probably Locktite Black Magic (?). I understand it is a pain to work with (Moray?)

dave
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Old 24th August 2009, 12:17 PM   #5
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I really dont know if thats what they use but, Loctite black magic is a pain to work with. It bonds to skin prety much instantly.
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Old 26th August 2009, 06:53 AM   #6
BudP is offline BudP  United States
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I just called Misco in Minneapolis and asked for a small amount of the glue they used to attach the things originally. I still have some, but am not sure how good it is, as I do not know the shelf life. Simple procedure. It is not Black Max from Loctite. Rather, a pretty soft adhesive that sets up after application. No hardener to mix at all.

Bud

Last edited by BudP; 26th August 2009 at 06:56 AM.
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Old 28th August 2009, 03:00 AM   #7
Nanook is offline Nanook  Canada
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Default Why bother?

As I own the set of FR8C drivers that Dave cut the whizzers off of, I can say that with a set of his (Dave's) phase plugs, I don't miss the whizzers at all. In fact, I believe that the top end has improved losing them and going with the phase plugs only.

The damage to the whizzers could have ignored...one of them had a small crease in it, but I did want to try phase plugs only.
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Old 28th August 2009, 03:09 AM   #8
col is offline col  Australia
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Nanook, any photos?

cheers,
col.
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Old 28th August 2009, 04:00 AM   #9
BudP is offline BudP  United States
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I think Stew has the right of it. I was NOT impressed with the FR8 whizzers. I don't think I ever really got them under control and if I had a pair today the phase plugs would be on my list to do. Even though the glue from Misco was free and postage paid.... I think they knew they had a problem.

Bud
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Old 28th August 2009, 04:34 AM   #10
Nanook is offline Nanook  Canada
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Default not a great picture....

hope that is viewable.
Attached Images
File Type: jpg Hemp Demetris.JPG (30.1 KB, 67 views)
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Last edited by Nanook; 28th August 2009 at 04:36 AM. Reason: no image attachment?
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