Which loctite for magnet shift?

Tony M

lawdogg wrote: »

I should clarify that I don't put any adhesive between the faces, only around the perimeters. (Some does wick inside, but not much.)

I've found that adhesive applied anything other than PERFECTLY even between the faces can cause the angle of the voice coil movement relative to the pole piece to shift from perfectly normal, which makes it impossible to go back together correctly ... the voice coil can no longer move up and down in perfect alignment with the pole piece axis.

That was a (really) annoying lesson early on in my re-centering learning curve.

So, when I get Rob's AWESOME JIG, I only have to make sure the voice coils are moving very freely and then apply 2-part epoxy (off the shelf Gorilla Glue) to the rim joints?

This sounds great to me.

lawdogg

That's really all there is to it!

xschop

I agree with Lawdogg, if you haven't had experience with Loctite anaerobic setting adhesives like Blue# 242 or stronger faster setting Red #271, then I would just re-glue perimeters after re-setting magnet and pole-piece.
You would never want to use a thick high viscosity adhesive between magnet and pole piece or back plate as that could set the pole- piece off axis and cause voice coil rubbing no matter how centered you got it.

And another important thing is to not get any glue on the inside of the jig as the inner rim sets perfectly flat on magnet perimeter and does all the aligning of set screws automatically.
So be sure magnets are free of debris before- hand.

turkeyaddict

Hi All -

I thought I should circle back around and give an update!

After making my initial posts, I realized I had stashed an old pair of 5Bs, bought for $10 at Goodwill, in my basement.

I had a few PMs in response to my initial posts, and was glad, because I had never checked the speakers with a multimeter to see if they were bad. In my 7Bs, one of the MW6500 and both of the black Peerless tweeters had no resistance (ohm at infinity), so I decided to concentrate on the 5Bs.

I had never even hooked them up and by using the simple push test quickly realized both of the midrange speakers were locked. I took the lone MW6500 from the 7B and both of the MW6502 from the 5Bs and reset the pole. I hooked all 3 up, and one of the 6502 seems to have some interference (not sure it if shifted or I hit the coil) but I was able to get the lone 6500 and one of the 6502 repaired and sounding very well. Both of the tweeters in the 5Bs were solid (these are 7-8ohm) and these little 5Bs crank. Thanks for all the help and the ideas.

Regarding the Loctite - I went with the green. At first I tried not using any liquid, but had such a difficult time moving the pole plate without some liquid between it and the magnet that I bit the bullet. I simply added 4-5 small drops to the magnet and took a plain piece of paper to spread the loctite before dropping the pole piece into the hole. I had at least 5 minutes of good working time to center the pole piece and confirm movement, and was happy with the outcome. I used Gorilla epoxy to seal everything. I'll also say that I used the blown 6500 (which also had a cracked magnet) for 'testing purposes'. Gorilla epoxy is strong, but you can remove it with an ice pick and patience, and can separate the magnet and pole piece by placing a screwdrive (or putty knife) on the side of the pole plate and then hitting with a small hammer to separate. I determine if something shifts during glue-up, there is the chance to start over without damaging the parts, and I will eventually take apart the one 6502 to see if I can repair better.

However - now I've got a followup question that I'm sure someone on here can help me answer. I tried moving everything into the 7B cabinets, but they sound like crap - I suspect there is a crossover issue, or it has something to do with the resistance of the tweeters. The original black tweeters are (I believe) 4 ohm, and the silver tweeters register 7-8 ohms.

The tweeters in the 5Bs look similar to the Peerless in the 7Bs - but instead of being black, they're silver/dull chrome. Are these also Peerless or are these something else? They don't have the horizontal groove that I see in most of the pics of the SDL tweeters, and I can't seem to find much information on silver/chrome tweeters in the older monitor speakers. If it helps, the sticker on the MW6502 speakers sticker had 1984 as the date. Pic attached:

turkeyaddict

Also - does anyone know if you can get replacement posts for the grills? The grills for these 5Bs are in great shape, but only 2/8 grill posts are intact, the other 6 are snapped or completely pulled out/missing.

pitdogg2

Tweeters are SL1000 not as good as the peerless.

https://www.parts-express.com/Heavy-Duty-Grill-Guides-12-Pair-260-367

turkeyaddict

Thanks for the quick reply and link.

What are people currently using as aftermarket replacements for the peerless tweeters and the mw6500 midrange? Classic rock sounds pretty good with the SL1000, I'm now curious how much better these will sound with aftermarket upgrades.

Is this the tweeter still preferred by most who have replaced/upgraded?


MW AUDIO MT-4115: 1 INCH DOME TWEETER
https://www.midwestspeakerrepair.com/shop/home-audio/tweeters/dome/mw-audio-mt-4115-1-inch-dome-tweeter/

pitdogg2

Only you can decide if that tweeter is for you. The replacement for the SL1000 would be the RD-0194, it does however have a slightly larger faceplate and the cut out for the peerless/SL1000 is different than that of the SL2000/RD-0194. The cut out and screw holes are off ever so slightly to mess with you. You would need to modify the cabinet slightly.

That tweeter from midwest I've seen rave and stay away from reviews. It seems to be a love/hate thing