Anatomy of a 200029-1 Tweeter

[spazmoch]

This is all really good stuff. I have a couple of dead tweeters from a set of ar28s. At some point I may well have a go at opening one up myself. Thanks for the great pics and descriptions.

[Giorgio AR]

Hi,

in my opinion, in addition to the problems of ferrofluid, I think I can suggest an excellent alternative substitute to the AR9 tweeter (visible in the photos below, taken from the usual auction site E..y)
in this case, replacing the complete magnet and dome unit.
Another option or use in my opinion (I hope that experts like Roy C or Frank M. or Tom T. will test this!), the second use that I believe can be done is the replacement of expensive AR10 / 11 200011-1 tweeters, probably disassembling the magnet from the plastic basketball and assembling the complete group 200054-0, otherwise replacing only the dome, coil and cables.
Last, and probably possible, this could also replace the tweeters of AR3 (same 2 modalities as AR10 / 11).
It's been a long time since I think of this tweeter as a possible substitute for dead AR tweeters.
I hope to have stimulated interest and to have indicated another way to restore the tweeter of our beloved AR
Giorgio

[Giorgio AR]

In this moment, 2 of these tweeter in auction at 22,50 $, cost about 1/3 compared to other non-original replacements!

[Giorgio AR]

On 1/1/2019 at 7:08 PM, Giorgio AR said:

In this moment, 2 of these tweeter in auction at 22,50 $, cost about 1/3 compared to other non-original replacements!

Now still missing 16 minutes to expire (unfortunately there is no sale in Italy, I would buy them !!)

[Pete B]

Just to be sure I follow, are you saying to transfer the faceplate so that they are correct 

for whatever 4 ohm application you want to use them for?

Those are 4 ohm I take it?

[Giorgio AR]

3 hours ago, Pete B said:

Just to be sure I follow, are you saying to transfer the faceplate so that they are correct 

for whatever 4 ohm application you want to use them for?

Those are 4 ohm I take it?

Hi Pete, this is my "intuition", I can not know if the tweeters are 4 or 8 ohm (I live in Italy, the seller does not send to me and does not declare the resistance of the tweeters), but my thoughts are: 1) these are made in the USA not Tonegen and the construction and aesthetic dome / coil and output wires is identical to the AR10 / 11 tweeters.
2) the magnet according to my opinion and the visual comparison makes it identical to that of the noblest tweeters (in the AR10 / 11 tweeters the magnet is inserted in the plastic container, glued on it on the back, above then were placed transparent or black stickers , depending on the period for aesthetic reasons) also the subsequent series AR9, AR58 etc. (look at the holes for fixing the top flange of these tweeters)
3) Same procedure for adapting the complete tweeter in the plastic box of the AR3a and LST, also possible the front wired connection as originally (I'm not a technician, but you have ability to perform a correct crossover in this case!).
4) disassembling the dome / coil assembly, this could be a valid replacement with little work for all types of tweeters described above!
I repeat Pete that these are my intuitions, but in case of purchase of the tweeters at auction, with a small expense you could probably have 2 valid and original spare parts.
5) if the tweeters were 8 ohms, the AR loudspeakers that could benefit would also be in this case many: AR5, AR2ax, AR LST2 and many later

[Pete B]

Yes that makes sense, wish I had not missed the ebay auction.

[Pete B]

@seventy1  your writeup on how to replace the ferro fluid is excellent and very similar to how

I repaired an AR-11 tweeter.  I also used a Sharpie to mark both rotation and position of the

dome.  It would be good to play a test tone at Fc, around 2 KHz and listen for voice coil rub in 

case the dome position needs fine tuning.

[DavidR]

On 6/4/2018 at 11:21 AM, seventy1 said:

If I do another, I'll find a way to dilute the cement and apply it with a small brush for a smoother more uniform coating.

The typical solvent for rubber cement is naphtha. Some use hexane (or maybe heptane) but that is unusual due to it having a very low flash point. Naphtha is available at Home Depot and other places that sell paint.

[seventy1]

Hey Pete, thanks, I played a 5 kHz tone. I just randomly chose a frequency below my old-man hearing limit. And thanks, David, for the solvent recommendation. Since the tweeter oil change, I'm still using the AR91s as my main two channel speakers and loving them. This past weekend, I swapped out the Erse Pulse-X 3.9 mfd MPPs that I had installed with Mundorf EVO Oils with 0.1 mfd bypass MPPs. I also added bypass caps to the 24 mfd Erse Pulse-X mid-range caps. The change had a noticeable effect, more detail but less harshness. I'm really enjoying these speakers, or actually the music, now where before I couldn't wait to move on to something else.     

[ra.ra]

This thread is simply a great tutorial on the surgical dissection, blood transfusion, sterile re-suture, and successful recovery of an aging patient complaining of ennui and general malaise. Really great close-up pics and descriptions - - thx again.

The de-solder and re-solder of those tiny tinsel wires to the terminals looks to me like the most delicate step. I really appreciated the tips for using a test tone during re-assembly, and to apply the new fluid directly to the VC. Any idea what the specific purpose is for that thin clear gasket?

[seventy1]

6 hours ago, ra.ra said:

Any idea what the specific purpose is for that thin clear gasket?

I assumed that it provides insulation and a bit of a cushion for the leads when the face plate screws are tightened to the metal base/magnet. If you left the lead wires under the gasket by mistake, it may be possible to break through the thin lacquer insulation and short to the base.  The gasket also spaces the face plate away about the thickness of the tweeter surround so it's clamping to a somewhat flat surface.

[ra.ra]

1 hour ago, seventy1 said:

I assumed that it provides........

Thinking about this a bit more, and I suspect you have correctly identified several very possible functional criteria. Mostly, I was surprised to see the tinsel wires threaded above the gasket, where I first thought it would be used to protect the delicate wires during assembly. 

[Pete B]

On 5/8/2018 at 9:07 PM, seventy1 said:

The lead wires are continuous pieces from the coil winding and appear to be solid enameled copper.  Thin as a hair and so far, impossible to solder to itself.  I broke one and have been trying to solder it back together.

@ra.ra  The lead in wires are not tinsel rather according to seventy1 they are "continuous pieces from the coil winding" 

so they are solid magnet wire.

[ra.ra]

1 hour ago, Pete B said:

The lead in wires are not tinsel....

Sorry, Pete, but I guess I'm just not schooled enough to know the difference between "tinsel" and "lead wires.....thin as a hair.....impossible to solder". Perhaps a micrometer measurement would educate me on the differences? Please clarify.

[Pete B]

Sure, I don't know if you've ever looked closely at the lead in wires to a woofer but they 

are often fine multistrand wrapped or braided around a fiber center.  These are tinsel 

wires.  The fiber center helps provide some physical strength and to keep the wire from

kinking.  Solid wire subject to vibrations tends to find a single point to flex where it 

eventually breaks if driven hard enough.

There's a picture here in Section 6:  http://sound.whsites.net/articles/speaker-failure.html

Most Kloss era Advent and EPI tweeters had tinsel lead in wires.

They are usually used with low crossover points such as 2 KHz or less but are always 

better to have for reliability.

[ra.ra]

21 hours ago, Pete B said:

I don't know if you've ever looked closely at the lead in wires to a woofer but they  are often fine multistrand wrapped or braided around a fiber center.  These are tinsel wires.

Hmmm.....I find this interesting - - - thx for the clarification.

Of course I have seen that type of wire in many uses and configurations, but never with the braid as shown in the center example from your link. Nonetheless, I was not aware that this constituted the definition of "tinsel", and I have been mis-using this term to identify tiny hair-thin wires, as found in the OP's tweeters. Oops....

[DavidR]

I'm curious as to why copper wire, no matter how thin, would melt from soldering. Copper's melting point is close to 2000'F and 60/40 solder is approx 400'F

[JKent]

29 minutes ago, DavidR said:

60/40 solder is approx 850'F

60/40 solder is about 390 F

[DavidR]

Just now, JKent said:

60/40 solder is about 390 F

That makes more sense. I thought it was approx 400'F. Google was wrong. Imagine that.

[JKent]

Yeah. I have a nice adjustable Weller soldering station that belonged to a friend. I think its max temp is about 700 F. I usually set it about 600.

[Stimpy]

10 hours ago, DavidR said:

I'm curious as to why copper wire, no matter how thin, would melt from soldering. Copper's melting point is close to 2000'F and 60/40 solder is approx 850'F

I hand solder 1 Mil 99.9% gold wire at work.  Not easy, but proper technique is key.

We use Weller irons, at around 700F.  They're equipped with the smallest Weller tip.  The most important thing is not to apply direct heat to the wire.  I lightly touch the tip with the solder, to get just a small drop of solder in place on the end.  That drop of solder gets touched to the well-fluxed wire joint.  On and off very quickly.  The wires need to be stationary too, with as little movement as possible.

[DavidR]

I have some copper wire that thin and put my soldering iron to and it didn't melt. ?

[lsandev]

Dear all,

I know this is an old thread but just wanted to share my experience maybe it will help somebody.

I bought AR-90 a few days ago... one tweeter worked occasionally and when it worked I could hear it works on lower volume. First I thought it must be the crossover and the switches on the back. Well to keep it short it wasn't. When I took out the tweeter it showed a dc resistance of 80ohms, then 2kohms, then 50 ohms etc when poked on the metal parts for wires... I thought it was some oxidation but actually it was bad solder between the speaker coil wires and the metal parts (i do not know the english word for it, its on the picture). Resolder it, got normal 4.7 ohms and the tweeter works fine.