Uhh… is this a “normal” repair?

ajt528 · March 27

Some pics of Polk 7A’s I posted about a few weeks ago and got some help here on the sound not being right. (Thanks for that.) Read up on the crossover upgrades and decided I’d give it a whirl. Started pulling one speakers apart tonight. And I mean, literally ***pulling*** it apart. Tweeter had to be pried out. This can’t be a normal repair, right? Or is that the way early Polk speakers were built? With some kind of sealing putty?

And has wire ever been soldered onto the driver and tweeter posts? Because there’s that too. I’ve never seen that.

Toolfan66 · March 27

That has to be that moretite crap that was the craze for a short minute around here many years ago..

Definitely replace it with Armacell, much better product..

The wires being soldered was standard on early polks..

pitdogg2 · March 27

IIRC early Polk did use mortite. Polk did solder all the drivers in the beginning. The tweeters are fragile do not try and desolder, clip the wires about about 4" from the soldered tabs on the tweeter then use quick connectors.

ajt528 · March 27

Thank you. Yes, I clipped them figuring I would have to install quick connectors anyway. I may just do the latest tweeter upgrade (number escapes me rn… 194’s or whatever). I still have to get all the solder off the tweeter connectors.

I’ll look into the armacell. Some of that moretite peels off easy and… some does not.

pitdogg2 · March 27

The peerless is a better tweeter, or is yours the SL1000?

ajt528 · March 27

Appears to have the pinhole, so I guess Peerless.

pitdogg2 · March 27

If they're good keep those.

ajt528 · March 27

Well, those parts I just ordered weren’t cheap. Great, another expensive hobby. 😂

F1nut · March 28

Peerless...Mortite, all 100% original. Do NOT replace those tweeters. Do replace every bit of the Mortite.

ajt528 · March 28

I’ll see what I can do to get all the solder off the Peerless’ posts. Been a dozen or so years since I soldered anything and that was just to fix a broken wire on an old set of electronic ear muffs (and I never really did it regularly before that). I’ll have to find some piece of busted electronics around here, open it up and practice a bit.

I ordered Soniccaps and mill resistors. I didn’t really want to spend the coin on Soniccaps but I couldn’t find the appropriate 33uF ClarityCaps anywhere in stock (in the USA anyway). Those seem to be the two “go to” capacitors from my forum reading. I did get a pair of RD0194’s but I plan on putting those in my RTA 8t’s, which I think have the 2000 tweeter.

Toolfan66 · March 28

Well slap me silly, I guess I didn't know Polk used Mortite, or I just don't remember.. I do remember a lot of folks using it around here for a minute..

Gardenstater · March 28

I remember reading MP comments where he said he actually favored Mortite over gaskets. I guess when the stuff is fresh and pliable it does a very good job of coupling the drivers to the baffle.

VR3 · March 28

I guess you could say it is more tight then others

mhardy6647 · March 28

Yeah. Good old Mortite (or, as I waggishly referred to it, Lesloose).
It was the Windex* of DIY loudspeaker projects for a while, about 25 or 30 years ago

This is the kind of thing that one ends up doing when sucked into the Mortite cult.

Did it help that awful, ringy Klipsch squawker (Klispsch's term, not mine) horn? Not enough. Not nearly enough.

Oh, while this thead is dredging up my Mortite PTSD

-- I used Mortite to make speaker gaskets for my folded mass loaded TQWTs. That was very dumb

given that I also didn't finish the Baltic birch plywood cabinets. The oil (or solvent) in the rope caulk has slowly but surely soaked into the wood over the decades. Derp.

______________________
* Windex, the miracle cure revealed to the world in My Big Fat Greek Wedding.

ajt528 · March 28

Gardenstater wrote: »

I guess when the stuff is fresh and pliable it does a very good job of coupling the drivers to the baffle.

To be fair to the stuff, the tweeter was really sealed in there. I tried pushing it out from the inside but… nope, wouldn’t budge. I needed to pry the tweeter out of the housing. I had “hold my breath” moments as the tiny flathead I was using to even get underneath slipped a few times.

But the mid drive and crossover just fell right out and the mortite broke apart. I will not be using it again. 😂

F1nut · March 28

Toolfan66 wrote: »

Well slap me silly, I guess I didn't know Polk used Mortite, or I just don't remember.. I do remember a lot of folks using it around here for a minute..

As I recall, Matt said they used Mortite because real gaskets were too expensive for them at that time.

F1nut · March 28

Gardenstater wrote: »

I remember reading MP comments where he said he actually favored Mortite over gaskets. I guess when the stuff is fresh and pliable it does a very good job of coupling the drivers to the baffle.

When fresh and pliable (read squishy) it decouples.

Gardenstater · March 28

F1nut wrote: »

Gardenstater wrote: »

I remember reading MP comments where he said he actually favored Mortite over gaskets. I guess when the stuff is fresh and pliable it does a very good job of coupling the drivers to the baffle.

When fresh and pliable (read squishy) it decouples.

F1nut · March 28

Yet, when they could afford real gaskets they dropped Mortite faster than a hot potato.

It's squishy no matter how thin you make it. Therefore, it decouples.

michaeljhsda2 · March 28

ajt528 wrote: »

I’ll see what I can do to get all the solder off the Peerless’ posts.

Why do you want to do that? Do you want to remove the tweeter for some reason? I didn't realize that trying to desolder the wire would cause the tab to come off and ruin the tweeter and I was the one that found out the hard way. Leave it be is my strong recommendation. As others have said, if you want to remove it, cut the wire at least 4 inches and use quick connects.

ajt528 · March 28

michaeljhsda2 wrote: »

Why do you want to do that? Do you want to remove the tweeter for some reason?.

Ok. I understand what you are saying now. I’ve never had speakers which didn’t have quick connects connected directly to the tabs on the driver or tweeter. I assumed, perhaps incorrectly, that under the mass of solder on the tweeter connection, there was a post of some sort. So my theory was get all the solder off the tweeter posts, attach quick connects to the wire and hook them up like “newer” vintage Polks.

pitdogg2 · March 28

You will apply quick connectors to the wires. They're your speakers, we are trying to warn you that in doing what you insist on doing will in all likelihood damage/ruin the tweeter.
Those Peerless are getting hard to acquire. The RD-0194 is not a replacement for the Peerless, not to mention it will not fit without cabinet modification. Please learn from our mistakes.

Gardenstater · March 29

ajt528 wrote: »

michaeljhsda2 wrote: »

Why do you want to do that? Do you want to remove the tweeter for some reason?.

Ok. I understand what you are saying now. I’ve never had speakers which didn’t have quick connects connected directly to the tabs on the driver or tweeter. I assumed, perhaps incorrectly, that under the mass of solder on the tweeter connection, there was a post of some sort. So my theory was get all the solder off the tweeter posts, attach quick connects to the wire and hook them up like “newer” vintage Polks.

There is a post, you are correct. The terminal is riveted to that post. The problem is that the voice coil wires are soldered to that post. You can see where the wires are soldered to the post if you look at the front of the tweeter and follow the upside down V to where there is a circular blob of insulating material. That's the connection that is vulnerable to any heating of the terminal. The rivet can't take a lot of stress either.

If you were to attempt to desolder the tabs you would have to use a heatsink clip on it and probably would still need to work fast. I've never had good luck with the plunger solder suckers I've tried. Probably never got a good one and the solder wick material I've had mixed results with. You need the combination iron/suction bulb type.

F1nut · March 29

^Wrong^

It's the tab that breaks off.

Gardenstater · March 29

F1nut wrote: »

^Wrong^

It's the tab that breaks off.

If you read what I said, I covered that when I said that the rivet can't take a lot of stress. For the OP, what would happen in that case is that the tab/terminal will break off. There have most definitely been people who have reported the solder joint getting melted where the voice coil attaches. Either one will ruin your day.

F1nut · March 29

Gardenstater wrote: »

F1nut wrote: »

^Wrong^

It's the tab that breaks off.

If you read what I said, I covered that when I said that the rivet can't take a lot of stress. For the OP, what would happen in that case is that the tab/terminal will break off. There have most definitely been people who have reported the solder joint getting melted where the voice coil attaches. Either one will ruin your day.

Oh, I read your post. The rivet does NOT break off, the tab does. The rivet stays in place. Provide one example of someone that has, "reported the solder joint getting melted where the voice coil attaches." I've been doing this a lot longer than you and I've never seen nor heard of that.

Gardenstater · March 29

The post is basically a hollow rivet that gets peened over, compressing the insulator and holding the terminal. Then they usually add solder for good measure. Some may have cra ppy rivet peens and rely more than others on the solder for strength. This is one that I have that has very little if any solder on the rivet. Melting the solder is risky, which is why it is advisable to not try to desolder the terminals. I clipped mine at 1" and crimped and soldered on a male faston.

Heat will travel through the post (hollow rivet) and can melt the voice coil attachment, which is risky also.

F1nut · March 29

Keep dancing

ajt528 · April 5

Currently working on these 7A’s and I have appreciated the advice and guidance. Since I’ll have these things apart for a while as I figure out how to install these huge capacitors, I’m going to do some further upgrades. But I’ve had to pull info from several posts on the forum (so I did search for answers to the below questions and either didn’t find them or it wasn’t clear to me). While I’m sure some of this is basic, I just want to make sure I have this info correct before I make some permanent or hard to undo changes:

1.) I purchased a roll of Armacell tape today at Home Depot. The tape just gets put where the mortite was around the edges where the speaker mounts, right? I don’t need to cover the whole area (for the tweeter) where the speaker seats and use armacell in place of a gasket, right? I use both armacell and gaskets.

2.) I saw a thread that mentioned hurricane nuts in 1/4”-20 but I looked at those size screws in Home Depot today and they seem awfully big compared to OEM. #8 or maybe #10 seemed more appropriate. What’s the size to use?

3.) Dynamat goes on the speaker baskets and the general recommendation is only on the basket fins, not all over.

4.) Is it recommended to replace the 40+ y.o. internal speaker wire? If so, with what is the recommended brand? It appears the OEM Polk wire is silver not copper. (As an aside, I did some speaker identification between my original post and this one, and unfortunately it appears I have the SL2000 tweeters in these 7A’s not Peerless, so I’ll probably upgrade to 194s).

5.) What are the “go to” binding posts forum members recommend, if I were to replace the originals?

6.) Last question on capacitors. I read a thread that you can’t use a lower VDC capacitor in place of the original. The crossover in the 7A uses 50 VDC, but the soniccaps are 250 VDC. That’s what was available. Most of the pics I see of rebuilt crossovers around the forum use the 250 VDC. At least one set had some 400 VDC. I don’t entirely understand why you can and/or should use such a high VDC compared to original.

Thanks. 🙏

Gardenstater · April 5

Wasn't this your picture? It is of a Peerless tweeter mfg. date 1978. Polk wasn't making the SL2000 at that time or the time of the 7A. Probably around 85 the SL2000 was introduced. Don't hold me to that exact date.

ajt528 · April 5

Gardenstater wrote: »

Wasn't this your picture?

It is, but the fronts have those straight… I guess they are voice coils… which I understood from looking at some forum posts are SL2000. The peerless appear to have the angled voice coils, and I think the SL1000s have those too. But maybe I misunderstood what I was seeing/reading.

Uhh… is this a “normal” repair?

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