AR2ax (Early) Tweeter Dome Suspension

[RoyC]

AR used jigs to hold the dome down to apply the foam.

[ReliaBill Engineer]

I clamped the dome down flush with the steel mounting plate. I used that steel washer with 3 legs soldered to it. The magnet clamps the washer down. A magnetic jig, if you will. Then I applied the red butyl at the 4 points. Let it cure for an hour. Then thinned the clear butyl so I could apply it with a brush. Now letting it cure overnight. 
 

Once cured, when I release the jig, the preload from the batting should push the dome out, giving it clearance to move when a music signal is applied. Fingers crossed…..
 

Thinned butyl sealant:

 

 

 

 

[ReliaBill Engineer]

Looks a tad messy. But it sounds really good! Clear, focused, dynamic, well damped. Loud, too! Plenty of tweeter sound at 50% pot setting.

I decided to secure the leads with black RTV silicone. 

 

 

 

 

 

 

[Aadams]

Nice.  How does it sound compared to the tweeter in the other box?

[RickB]

Really good job! We all have our own opinions-The only thing I wonder about is the ATV on the leads-but if it works-it works.

[RickB]

RTV sorry!

[RoyC]

1 hour ago, RickB said:

RTV sorry!

Nice recovery. Shims would have been helpful as well.

Is the red and clear material around the dome a butyl rubber compound or rtv? I've seen a red rtv gasket material used for this purpose as well.

[ReliaBill Engineer]

42 minutes ago, RoyC said:

Nice recovery. Shims would have been helpful as well.

Is the red and clear material around the dome a butyl rubber compound or rtv? I've seen a red rtv gasket material used for this purpose as well.

I only used RTV silicone on the leads. I don’t like the electrical tape looks, although I did keep that 1 strip on the plywood.  So that’s black RTV. The rest is clear butyl. The red is a mix I came up with 4 years ago, for repairing GE VR1000 styli (and VR22). It gives the butyl rubber a more “spungy” quality to it. (I normally use gray butyl; for this I used clear.) I should have thinned it a bit more for easier application. But I didn’t want the mix to run; I wanted it to bridge between the faceplate and the dome. The red mix has silicone grease micro encapsulated in it, by using my ultrasonic tank; mixed the clear butyl with my red “dope”, putting it in the ultrasonic tank on Saran Wrap, then mixing a small amount of silicone dielectric grease in. After curing, if you slice it with a razor blade, then examine the cross section under a 25x loupe, you’ll see the itty-bitty beads of grease. It’s more flexible than butyl, and damps vibration really well. It controls the iron cantilever of the VR1000 and VR22 styli, giving an amazing level of tracking and clarity to the cartridges’ sound. So rather than use foam, I used this red mix. 
 

I won’t be able to give it a long listening session until tonight, after work. I briefly listened earlier, to make sure all was well. It sounded great for the minute or so I had it connected. Nice and clear. 

 

[ReliaBill Engineer]

5 hours ago, Aadams said:

Nice.  How does it sound compared to the tweeter in the other box?

The other tweeter hasn’t been molested. I haven’t even removed the grill; it’s still stapled. Still original condition as I received it. Currently the tweeter makes no sound. Mid is muted. 

[ReliaBill Engineer]

Been listening this evening. What a huge difference! Now I have balance. With the tweeter at 100% and the mid at 65%, the sound is no longer squawky and brash. My room is acoustically quite dead. Wall to wall carpet, drapes, cloth upholstered couch, loveseat, recliner. 
 

I can put my ear to the tweeter and hear plenty of output where I could barely hear anything before. It shimmers sweetly, not irritating at all. 
 

Could this be better? Probably. I don’t think it needs the 4-point suspension add-on. I think the clear butyl surround membrane is all it needs. It just needs a filler at those 4 notches surrounding the VC gap. That’s what I started to do originally. I was going to insert a strip of parchment paper, rolled into a tube. Then fill in the 4 notches flush to the top of the face plate with butyl. Let cure. Then remove the parchment to match the circumference of the faceplate gap. Position the tweeter in the gap. Clamp it down. Then just apply the thin membrane butyl seal. Let cure.

The 4 notches in the faceplate. Still has remnants of yellow foam in them (I forgot to take a pic after cleaning out the gap and notches.):

 

[ReliaBill Engineer]

A sound test of the rebuilt tweeter:

 

 

 

 

[ReliaBill Engineer]

I’ll pretty up the baffle, then start on the 2nd speaker. If its tweeter needs work, I won’t add the 4 suspension points. I’m going to smooth the baffle, then use satin black finish. 

[ReliaBill Engineer]

Sure is quiet in here…… Was hoping for a bit of feedback.

[Aadams]

I think you have plenty of monitors.  I, for one, am waiting for the second tweeter results.  One question:  Considering this is a stereo pair, if you rebuild the second tweeter in a different fashion how do you insure they will have near identical performance? 

Also, if you omit the 4 dots on the second tweeter does it count as mod or restoration? Assuming it works correctly.

The CSP community has never been much of one for watching videos of AR speakers playing on computer speakers.

[RickB]

I agree if it was mine I would try to rebuild it the same and then test it apples to apples. Great work on this super tweeter.

[ReliaBill Engineer]

Here is an apples to apples comparison. Same track of music, same cartridge. Before tweeter rebuild and after. The next speaker in the pair will be the same. 
 

Before tweeter rebuild (caps replaced, pots cleaned and working): (Mid driver is overpowering the balance of sound)

 

 

AFTER tweeter rebuild:

 

 

The above are playing a 2022 recording from Octave records on vinyl.

 

Below is a 1964 recording from Billy Vaughn, using the rebuilt tweeter. A new stereo album when these speakers were new (approximately):

 

[RoyC]

17 hours ago, Aadams said:

The CSP community has never been much of one for watching videos of AR speakers playing on computer speakers.

Agreed...Increased sensitivity is obvious, but quality is hard to determine in this way.

I think RickB meant "apples to apples" as it relates to consistent results.

[genek]

So if rebuilding a tweeter produces more output, do we know how it compares to the tweeter when new, and would more output than when new always be good...?

[Aadams]

From an AR3 Brochure in Early 60s.

That supertweeter was designed to crossover at 7500hz and smoothly rolloff to 18db down at around 4k hz.  Don't know what influence the crossover network played in this chart.  I just happened to find a clear one to enlarge.

 

[RickB]

Thx Roy- lol!’n

[RickB]

Auto correct is my enemy at 77-ha!

[ReliaBill Engineer]

5 hours ago, genek said:

So if rebuilding a tweeter produces more output, do we know how it compares to the tweeter when new, and would more output than when new always be good...?

There is a pot I can use to turn down the tweeter output.
 

I’m looking for *balance* here; the biggest complaint I’ve read about in various groups/forums re: these original drivers is lack of balance between the mid and tweeter. I’ve seen folks add padding resistors to the mid, and I’ve seen folks replace the tweeter; I’ve seen folks replace the mid driver. 
 

As for duplicating results, that’s easy. But at this point, the second tweeter is exactly as received. Soon enough, I’ll take a look at it. 
 

But a huge question remains: Who out there has a brand new original tweeter for these? 
 

My dad is still alive, who had bought a pair of 2ax speakers new in early ‘65. He decided to trade them in late in ‘66 for a pair of Wharfdale W70Ds, with a Garrard Lab 80 turntable.  He regretted it. For over 50 years, when we talk stereo stuff, he still mentions those AR 2ax speakers.  That’s why I recorded the 1964 Billy Vaughn track, it was one of his favorite records he remembers hearing over the ARs. He says this one AR speaker is the way he remembers it. So there’s that. 
 

If anyone has a recording of a new original early AR 2ax tweeter, I’d love to hear it!

Bass doesn’t come across well over cell phone speakers. But I can hear good mids/tweeter balance…or not. I can clearly hear how inadequate the tweeter was in my first recording pre-rebuild. And in my living room, this speaker sounds very good. Lacking nothing, and giving my Polks a run for the money in every area. The AR impressed me, even in a mono source. 

[genek]

Even NOS would be age degraded by now. Best you can do is measure frequency response and compare to old measurements.

[ReliaBill Engineer]

6 hours ago, Aadams said:

From an AR3 Brochure in Early 60s.

That supertweeter was designed to crossover at 7500hz and smoothly rolloff to 18db down at around 4k hz.  Don't know what influence the crossover network played in this chart.  I just happened to find a clear one to enlarge.

 

Problem here is that while we can see the XO response below target frequency, we can’t see relative output of the tweeter vs the mid-tweeter. That is a chart of only the tweeter response on, and off axis.

As long as I can get balance by adjusting the pots, I’m satisfied. The fact that I can get balance within the adjustment range of both pots, tells me I’m where I need to be with the tweeter output. And getting balance with both, AND the woofer, is a wonderful sound! Currently I’m at 80% on the tweeter, 60% on the mid-tweet.

[ReliaBill Engineer]

20 minutes ago, genek said:

Even NOS would be age degraded by now. Best you can do is measure frequency response and compare to old measurements.

Exactly my point. Again, balance, clarity, definition, smoothness, lack of distortion were my goals. There exists no way to hear a “new, original” AR tweeter for these. 
 

I trust my dad’s memory. He’s old, but his hearing and memory are very good. He’s anxiously awaiting my dive into the other speaker, then to finish the cosmetic work.