AR2ax (Early) Tweeter Dome Suspension

[ReliaBill Engineer]

8 hours ago, RoyC said:

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.

Well, maybe CSP folks should reconsider. The alternative is….nothing. Just pics. So, if I said that I thought these sounded good, then left you with just pics, what would anyone learn? What gauge would you have?

[RoyC]

2 hours ago, ReliaBill Engineer said:

Well, maybe CSP folks should reconsider. The alternative is….nothing. Just pics. So, if I said that I thought these sounded good, then left you with just pics, what would anyone learn? What gauge would you have?

It's never easy, Bill, as many subjective claims are made in audio forums. I really doubt anyone thinks you didn't do a good job. You were just asking for feedback...

Below is a page taken from an AR document. It may be of some assistance to you if you are running response curves. Note the 2ax at the far right. I believe it said it was with the level controls at max.

Roy

[ReliaBill Engineer]

I have choices. Using the pot, the tweeter can be turned down to “OEM” levels, or turned up to help the mid-tweet, kissing or surpassing the mid-tweet while (both) having sufficient output to match and compliment the woofer. 

IMO it was a mistake to not allow the tweeter to fully compliment the other drivers. The fact that AR later changed to a different tweeter supports this. AR was more limited in materials back then, than now. 

This tweeter has a very powerful magnetic circuit. AR purposefully used brute force to restrain this tweeter’s output, overdamping the internal air volume, and restraining the dome by its suspension. 
 

What I did was trade for more controlled output by using a lossy suspension. The red compound I used can be dropped from 4 feet vertical and it won’t bounce; yet it is very elastic. So I freed up the dome just a tad, but it is highly damped. 
 

So this tweeter now accommodates more modern tastes, or not. Just a turn of the pot. OEM or more modern.

It handles power. This evening I was peaking at 90 watts,40 watts music power. No breakup and no distortion.  Wife was out talking to neighbors.

[Giorgio AR]

3 hours ago, RoyC said:

Note the 2ax at the far right

In this case, however, the measurements concern the next tweeter with a paper dome and greater dispersion, different efficiency compared to the previous tweeter

2 hours ago, ReliaBill Engineer said:

Using the pot, the tweeter can be turned down to “OEM” levels, or turned up to help the mid-tweet

Certainly the Pots allow a fine regulation of the mid and tw emission, allowing to find the best (or subjectively preferred) sound balance.
Anyway Bill I have to offer you my sincere compliments on the work done, on the attached photo shoot, on your dexterity and technical ability... I love the old AR tweeters too and knowing that they can be brought back to optimum efficiency is wonderful news.

[Aadams]

16 hours ago, ReliaBill Engineer said:

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.

Your result is probably close enough because your pot settings are in the range of the most common settings for AR Classic 3 way or 2.5 systems.  The appearance is also correct.  I can count on two fingers the number of other people who are known to do this specific mechanical repair. 

The most important goal is for you to create a matched pair.  It would be a bonus to be able to match the performance curve of the original spec for the AR3 which was aimed at linear power response rather than high on axis output.

According to history on this site, reject rate for the four blob tweeters was high with a large percentage being sent back for rebuild.

 

 

 

[rjr513]

Nice work @ReliaBill Engineeron the rebuild of these great tweeters. The image below is jig I used to hold the dome in place while the suspension blobs applied 

[ReliaBill Engineer]

I have to admit, that my expectations for these speakers (after cap replacement, pots cleaned) may not have met their “off the shelf” AR intended performance. But right now, my dad is happy, my wife is happy (story later…) and I’m happy. These do what the ‘66 Wharfdales couldn’t do. I remember those well; I rebuilt them in 1982. They were chesty, beamy, fatiguing, yet “clear.”  No sweet smoothness, and no “melting” of the output into a cohesive output. It’s like each driver was audible unto its own. But their cabinets had my mother’s WAF. 
 

I absolutely love how this (later, “these!”) speaker, using a mono signal, delivers a sense of air and depth. Easy smoothness. If that’s the “AR sound”, I’m liking it!

 

WAF: My wife read me the riot act when these ARs showed up. Man, did she let me have it!! “Wasted money! No room! Another project!” When I brought them in, wired them, played them, (untouched) she let me have it again. “Why? Your other speakers sound fine! I don’t like these! They look old! I don’t like those covers! Do they have roaches and bugs??! Where are you going to put them??! They don’t sound very good! You wasted our money!”

I can honestly say that now, she is more understanding, and more approving. She still wants black grill cloth….

 

 

[RoyC]

12 hours ago, Giorgio AR said:

In this case, however, the measurements concern the next tweeter with a paper dome and greater dispersion, different efficiency compared to the previous tweeter

True, it can only be assumed that AR carried over the design goals from Bill's earlier era specimens, as they were sold interchangeably.

Other than the foam blob suspension, the tweeters were certainly different. DCR of the early large orange dome tweeter is under 2 ohms and the later smaller black dome is around 6 ohms. Since they both were used with the same 4uf crossover capacitor cap and level controls, this alone would have made them behave much differently if their mechanical properties were the same.

The huge magnet structure made the earlier tweeter perform as intended at higher frequencies with a more restricted/less compliant suspension. The later small dome was more compliant, and had a soft foam material under the dome instead of packed fiberglass. In other words, AR relied on mechanical properties more than electrical to achieve the same, or similar, design goal.

Dispersion was really not all that different between the early and later versions, especially when the cabinet grille is taken into account.

Roy

[Giorgio AR]

1 hour ago, RoyC said:

Since they both were used with the same 4uf

Roy I love them both, certainly they don't sound the same, to my ears perhaps the 3/4 tweeter is more discreet, but well defined in the high harmonics (it almost disappears when listening, but does its job excellently), the early one is more "visible" , but defines the high harmonics similarly...what can I say? They are masterpieces born from brilliant minds, innovative in the 50s and then developed without changing the original philosophy.

[tripleguy]

Good job. I can notice a difference in the recordings played through my system. Cymbals and the other highs are much more present. One thought tho on recalling a speaker's characteristics from hearing them last 50 years ago. I could not tell you what my speakers from 40 years ago sounded like (JBLs). I know I liked the way they sounded but if I heard a restored pair today I couldn't tell you if that's what I heard 40 years ago. As long as they sound good to you is all that matters.

[ReliaBill Engineer]

My dad only owned 2 pairs of speakers in his entire 93 years. Just the ARs and Wharfdales. He was quite into HiFi in the 50s and 60s. He got laid off from NASA in 1972, after Apollo 17. He has an amazing memory. Life took over after that. 
 

I wish bass came through on YouTube vids. I put on my Shure V15V cart and was playing some Linda Ronstadt earlier, my wife’s favorite singer. The vid doesn’t seem to play the bass heft and tightness. 
 

I love what AR managed to get from these. The more varied the music, the more I’m impressed. 
 

 

[Martin]

I wonder which version of the generally disappointing W70 your dad bought to replace the ARs. Seems to me the W70 was updated a few times with newer & possibly, improved,  tweeters that may have made them more competitive with AR & KLH, etc. 

[ReliaBill Engineer]

He had this version of the W70. 
 

 

 

The tweeter, not the pink donut:

[Giorgio AR]

7 hours ago, ReliaBill Engineer said:

He had this version of the W70. 

Wonderful speakers, greath photos...

[ReliaBill Engineer]

Getting ready to work on the 2nd speaker of the pair. 
 

The pots rotate freely, and the mid and (super) tweeter respond to turning the pots. There is faint output from the tweeter. Cabs of both are in very good condition; no crushed corners or peeling veneer. Just lots of scratches in the finish. Badges are gone. Sold, likely.
 

Im going to record from this as-is. Possibly as close to original tweeter domes as I’ll ever find.

 

 

Stapes:

 

 

 

 

 

[ReliaBill Engineer]

Here is the raw, unmolested speaker. Both pots turned up to 100%. I get output from the mid and tweet. Both pots turn down/up their respective drivers.

BTW: AR cheated on the pots. When I mounted the cleaned pots in the first speaker, I mounted the pots so 50% lined up perfectly with the white dot. I had to rewire the pots to get enough wire slack. 50% and the white dots don’t match up in the original manufactured configuration.
 

 

 

And for comparison, same track, rebuilt tweeter, new caps, cleaned pots:

 

 

[ReliaBill Engineer]

Cheat? Yes. On the tweeter pot, the white dot lines up with a 75-80% setting, from the factory. The mid is pretty close; at the white dot, you’re close to 50%.
 

Full increase, where I set the the pots:

 

At full decrease:

 

 

Factory mount, full increase:

 

Factory mount, full decrease:

 

[RoyC]

"Cheat? Yes. On the tweeter pot, the white dot lines up with a 75-80% setting, from the factory. The mid is pretty close; at the white dot, you’re close to 50%."

Cheat? No. AR set up the controls so the white dot was "normal" for the typical room. Full increase for the both the mids and tweeters varied with each model. It is why the pot's anchor notch is placed differently for each driver in each model. This is a common misconception for people new to AR.  It had much more to do with design goals than whether or not a tweeter (or mid) with more output could be manufactured.

The original schematics and drawings are quite specific in this regard.

Roy

 

[ReliaBill Engineer]

I respectfully disagree. The graphic for the pots “imply” that the white dot is a 50% setting. That’s why I said “cheating” in quotation marks.

It doesn’t require one to be a veteran AR aficionado to see that. 
 

I will reset the second speaker so the white dots “are” at 50% of the wiper travel, as I did the first one. Makes sense to me.

 

[ReliaBill Engineer]

So here is the second speaker, grill removed last night. 
 

The tweeter appears to be in pristine condition, as do the mid and woofer.

 

 

 

 

I’ll change out the capacitors, check the pots and adjust their positions. Then I’ll replace the woofer and have another listen.

[genek]

3 hours ago, ReliaBill Engineer said:

I will reset the second speaker so the white dots “are” at 50% of the wiper travel, as I did the first one. Makes sense to me.

 

Hopefully, you are not planning on reselling, because a vintage AR "aficionado" considering buying will be unhappy to discover that the white dots no longer correspond to AR's factory Normal settings.

[RoyC]

Bill,

AR never implied the white dot to be the 50% point of the rotation. See attached label and partial factory schematic of the AR-3a. It shows the "normal" white dot setting of the AR-3a's tweeter to be 1 3/4 ohms off full increase and the "normal" dot setting to 3 1/4 ohms off full increase for the mid. I have other documents that state that the fully increased setting is considered to be "flat".

As i mentioned earlier, when the pot's anchor tabs are seated in their corresponding notches on the crossover board (see attached photo of an AR-4x I'm presently repairing), the pot is placed in the appropriate position to meet AR's specs for the dot. The normal/white dot settings and corresponding internal pot mounting positions varied with model (ie. the AR-3a is different than the AR-2ax or the AR-4x seen in the photo).

If the white dot was meant to be halfway for every model and every driver, it would make all of this meaningless.

If you haven't done so yet, take a peek at the forum Library. It will provide insight into AR speakers of the era.

[ReliaBill Engineer]

8 hours ago, genek said:

Hopefully, you are not planning on reselling, because a vintage AR "aficionado" considering buying will be unhappy to discover that the white dots no longer correspond to AR's factory Normal settings.

Very few would care. The white dot setting is relative anyway. Most everyone is going to set and adjust by ear, regardless of the white dots.  My repair of the tweeters kinda blows those white dot settings out of the water anyway, so it’s really a moot point.
 

I showed the pic of the pot settings to my wife and oldest son. They both assumed the white dot would equate to 50% output. So it’s intuitive. 
 

I don’t like the sound of these, as delivered. The seller, the original buyer/owner’s son, said he tried them, didn’t care for them. “Too dull sounding.” He removed the badges from the grills and sold them.  Only the most die-hard AR fans like them as they are. My son wants these when I’m done. He likes the “cool factor” and says they will sound great when the second speaker is updated. I agree. Others apparently think the HiVi tweeter is an upgrade, not a molestation. I think updating the capabilities of the original tweeter is a better way to go. Certainly more original than a replacement tweeter. Updating the capabilities of the original tweeter is no more blasphemous than replacing the capacitors, IMO.

 

As you are aware ^^^^ I took pictures of the original pot positions. They can be returned; I left plenty of wire slack. 
 

So let me ask you this: Would “original aficionados” even be interested in these, since I “changed” the character of these original tweeters? Somehow I don’t think I need to worry.

[genek]

Someone who is an "original aficionado" would most likely want to see some new response curves to determine how the speakers with rebuilt tweeters compare to published curves for the speakers when new. This is the crowd who would care that the level controls don't line up with original settings and would be looking into things like adding resistors or coils to bring response back to original.

There are others who will be more flexible. These are the folks who replace original tweeters with HiVis and don't bother with adding coils, or are satisfied with L-pads instead of pots. For them, you'd probably be ok just specifying the ways in which the speakers have been modded from original. 

[ReliaBill Engineer]

How many people who buy a new speaker want response curves, so they can compare to published response curves? And 58 year old speakers?  Anyone who asks *me* for response curves is out of luck. What they can do, however, is feel free to adjust the pots to their liking. I’m confident that there are pot settings on these  that will exactly match original response curves.

 

And from original: All original drivers, original pots, original wiring, original interior rock wool, all original veneer, original grills and original grill cloth, new capacitors.