Tim's triple 3a restoration

[owlsplace]

1 hour ago, KlausDK said:

I have had the same problem with broken voice coil, managed to repair, see this post:

Don't sacrifice the Improved versions, due to the lack of the rheostats and an in general better cross-over, they sound better than the normal 3a, in my opinion.

BRgds Klaus

Now that looks like something I would try. The 12" woofers are easier to find on this side of the pond though.

Roger

[TimmyTonga]

here is what my attempt to replicate Klaus's excellent repair looks like at close of play today.

 

 

I think my former is more wrecked than Klaus's; I have no remaining holes with which to line up the two halves of the former. But I think the diameter of the holes is about 5mm (can anyone confirm?), so I am setting the two halves apart by that distance.

Tomorrow I'll clean off the torn paper and find a suitable glue.....

Tim

 

[TimmyTonga]

cleaned up the paper:

and stuck on my new piece of card;

took note of a post from Klaus's original thread that mentioned the over-heating, so I used a hole-punch to mimic the factory former.

Bit worried that the gap between my upper and lower portions of former is a couple of mm too large, resulting in a slightly longer former than was originally there...

 

[owlsplace]

1 hour ago, TimmyTonga said:

Bit worried that the gap between my upper and lower portions of former is a couple of mm too large, resulting in a slightly longer former than was originally there...

I would think the VC wires would limit the gap size.

Looks nice anyway ....

Roger

[frankmarsi]

Pardon me, but this doesn't look like it will work.

It doesn't seem to allow for much cone travel which can be as much as 1/2 inch.

The stalwart and hardy AR-3a woofer may outwardly look somewhat rough in it's construction but, to this day in some circles at least is still considered a excellent woofer, maybe better than many newer cones.

I posted a couple of links, other than that, you will have to buy an appropriate used woofer.

 

[Stimpy]

As long as the repaired section does not bottom against the pole piece, I think the OP did a FANTISTIC job.  At least, it'll keep his speakers up and running, until a replacement woofer shows in the UK.

 

 

[TimmyTonga]

You may be right Frank, but it was the only game in town, as there are so few used woofers to be had over here. I have about half an inch as it stands, but it may be less than that once I've put a new surround on it, as it may hang lower in the basket.

[frankmarsi]

With shipping this may not be not such a bad option.

http://www.ebay.co.uk/itm/Acoustic-Research-AR-12-Woofer-ORIGINAL-AR-Speaker-/252378600632?hash=item3ac2efd4b8:g:G4QAAOSw9ZdXKj-8

What's that about $98.53 in USD. I'm presently watching a pair for $175. USD.

Because of their heavy weight combined with its odd shape and inherent odd balance, packing should be discussed and made very clear.

I've had many a woofer shipped to me ( on the same continent) but, on occasion, the woofers either broke through their box or two woofers attached to each other arrived with bent frames. I've sent some back for refund. Most times, I was fortunate and all was good.

Please keep this a secret but I own 28 of them these days with only 10 in operation. The rest are waiting for refoaming and placement in the numerous empty cabinets I have, mostly AR-3as. True, I am a hoarder but still a true lover of the AR attraction and musical portrayal they afford.

However, if we're talking about one single woofer, your chances are better for safe arrival.

 

[TimmyTonga]

2 hours ago, Stimpy said:

As long as the repaired section does not bottom against the pole piece, I think the OP did a FANTISTIC job.  At least, it'll keep his speakers up and running, until a replacement woofer shows in the UK.

 

 

Thanks for the positive vibes Stimpy. The proof of the pudding will be in the eating!

 

t

[TimmyTonga]

1 hour ago, frankmarsi said:

With shipping this may not be not such a bad option.

http://www.ebay.co.uk/itm/Acoustic-Research-AR-12-Woofer-ORIGINAL-AR-Speaker-/252378600632?hash=item3ac2efd4b8:g:G4QAAOSw9ZdXKj-8

What's that about $98.53 in USD. I'm presenting watching a pair for $175. USD.

Because of their heavy weight combined with its odd shape and inherent odd balance, packing should be discussed and made very clear.

I've had many a woofer shipped to me ( on the same continent) but, on occasion, the woofers either broke through their box or two woofers attached to each other arrived with bent frames. I've sent some back for refund. Most times, I was fortunate and all was good.

Please keep this a secret but I own 28 of them these days with only 10 in operation. The rest are waiting for refoaming and placement in the numerous empty cabinet I have, mostly AR-3as. True, I am a hoarder but still a true lover of the AR attraction and musical portrayal they afford.

However, if we're talking about one single woofer, your chances are better for safe arrival.

 

With all the import duty and the poor exchange rate at the moment, I think I would be looking at at least £100. And that dust-cap looks a bit suspect.

I’m reluctant to give up on this woofer because it has exactly the same day of manufacture as its twin - 10th April 1974. But I'll fire it up on Sunday, and then we'll see if I got away with it like Klaus did.

it would have been much simpler if I had gotten an obsession with a British speaker. *sigh*

[Stimpy]

12 minutes ago, TimmyTonga said:

The proof of the pudding will be in the eating!

"How can you have any pudding when you don't eat your meat!?!"  

 

 

[frankmarsi]

1 hour ago, TimmyTonga said:

With all the import duty and the poor exchange rate at the moment, I think I would be looking at at least £100. And that dust-cap looks a bit suspect.

I’m reluctant to give up on this woofer because it has exactly the same day of manufacture as its twin - 10th April 1974. But I'll fire it up on Sunday, and then we'll see if I got away with it like Klaus did.

it would have been much simpler if I had gotten an obsession with a British speaker. *sigh*

Well, you're correct about this particular woofer, it incorrectly has a porous dust cap which is not recommended in an acoustic suspension enclosure, however it was just an example. Watching for others should be an everyday chore for you in order to increase your chances of landing a good one. AR was once big in England so, there might be others closer to home.

Ultimately, this attraction for speaker components and their boxes is part of the equation however, ultimately it's about the music. I should know as I was such a lover of the 'box' and raw speakers that I was building my own boxes and using old TV speakers found in other folk's trash. By late 1967, I was fortunate to work on Wall St. near the long forgotten 'Radio-Row' aka Cortlandt St. where I bought two pre-made large cabinets and mounted "Jensen" woofers and no name horn tweeters. By 1972 I was lucky enough to afford $392. for my first pair of AR-3as. I still have those big cheap boxes and certainly kept my original 3as. My digs looks like 'hoarder-central' with so many wood boxes strewn about.

Of course my main listening room is dedicated only for my most complete system. My AR-9 system is set-up in another room but, never used until I clear some clutter and decide which direction I will take with amplifiers. I'm thinking about more modern and expensive ones compared to what they're presently connected to, or making up my mind to totally rebuild the amps I'm using. Again, the mechanical aspect for me can be a distraction.

Knock on wood, my main system is almost finished, still a stretch to go yet. Nonetheless, it sounds magnificent at this point and thus enables me to experiment with MC phono cartridges and room acoustics like bass traps and so forth. I should mention that typically I do put in many hours of listening. Vinyl of course.

I do know what it feels like to want to keep things original and appreciate your direction but, sometimes there may not be a recourse.

Ultimately the music and the whole concept of what music does for the mind and soul is the last word.

Hopefully, a time will come when your speakers are complete, your system is performing at peak and the simple pride of ownership makes some room for the exclusive pleasure of music listening and not the 'nuts and bolts' that can sometimes be energy consuming and distracting from the music itself.

Good luck to you and happy listening. I hope you find suitable woofers.

[TimmyTonga]

I had to redo this repair, as it became obvious when I tried to refoam that I had not aligned the top and bottom halves of the former precisely enough, so the cone was at a slight angle to the basket. So for anyone else attempting this repair - do the surround first!

Mindful of Frank's concerns I did try and close the gap slightly:

so in the end I had pretty much 1/2". (the stuff at the bottom is pink plastic shims bent over and stuck down with tape to give me more room to work).

I then stuck the woofer in the cab just to give it a basic road-test, and I can report it works;

 

....and survived Billy Cobham's 'Red Baron' at what I might call a 'significant' volume (This is a decent sub-100 cycle workout for any woofer, imho). 

Also pleased to report that the volume seems no different to that of its twin.

So my heartfelt thanks to Klaus for drawing my attention to his fix from 9 years ago! Long may it last.....

Tim

[owlsplace]

okay, perseverance pays off ...

Roger

[KlausDK]

23 hours ago, TimmyTonga said:

So my heartfelt thanks to Klaus for drawing my attention to his fix from 9 years ago! Long may it last.....

Tim

my pleasure

[TimmyTonga]

Dear All, here's an update.

Both pairs of 3as are working - hurray! All pots work OK. 

All drivers work...OK

But as predicted, there is something of an issue with the amount of energy from the tweeters. I decided it was not possible to judge the quality of the output from them until the quantity was sufficient to get them in balance with the other two units. I considered bypassing the pots, but other posts on this board suggest that this gets you 1/2, maybe 1db at best. i think this may not be quite enough, so I am going to drop in L-pads from VintageAR. Larry doesn't think there is any technical reason to  put a resistor in circuit with these, and so that is where I will start, and then amend as necessary. They will arrive early next week and I'll let you know what I think when I've dropped them in.

So while this issue has been parked, I've been looking at the third of the unholy trinity - the pair of Improved.

I've got this;

(Try and ignore the KEF tweeter....)

 

I've got no papers on the back, (but obviously an A/B switch).

 

I've got this;

 

and I've got this;

 

 

I know - it looks like a truck-load of 3as crashed into an electronics concession.

Who would put new caps in circuit and not position them so you can see the values? We need to see your working! Still, we seem to have Solen, and a mixture of film and npe on the woofer so we might give him the benefit of the doubt.

 

Here are my questions to all you Improved experts out there..

• Does the coil #16 in the top right-hand corner look original to you, or has someone put in new values to accommodate the KEF?

• Does the layout of the baffle board suggest that both midrange and tweeter were once front-wired, or just the tweeter?

• Am I right in thinking that the woofer is 1974? (its twin is unmarked)

If the tweeter was originally front-wired then I would assume an A.19 would be the first choice, but that one could put in an A.23 instead.....

Many thanks for any help, as ever...

Tim

[RoyC]

On 7/22/2016 at 11:17 AM, TimmyTonga said:

Dear All, here's an update.

Both pairs of 3as are working - hurray! All pots work OK. 

All drivers work...OK

But as predicted, there is something of an issue with the amount of energy from the tweeters. I decided it was not possible to judge the quality of the output from them until the quantity was sufficient to get them in balance with the other two units. I considered bypassing the pots, but other posts on this board suggest that this gets you 1/2, maybe 1db at best. i think this may not be quite enough, so I am going to drop in L-pads from VintageAR. Larry doesn't think there is any technical reason to  put a resistor in circuit with these, and so that is where I will start, and then amend as necessary. They will arrive early next week and I'll let you know what I think when I've dropped them in.

So while this issue has been parked, I've been looking at the third of the unholy trinity - the pair of Improved.

.Here are my questions to all you Improved experts out there..

• Does the coil #16 in the top right-hand corner look original to you, or has someone put in new values to accommodate the KEF?

• Does the layout of the baffle board suggest that both midrange and tweeter were once front-wired, or just the tweeter?

• Am I right in thinking that the woofer is 1974? (its twin is unmarked)

If the tweeter was originally front-wired then I would assume an A.19 would be the first choice, but that one could put in an A.23 instead.....

Many thanks for any help, as ever...

Tim

Tim,

If your pots were functional the L-pads will not improve the output of your AR-3a tweeters to a significant degree...and they certainly will not increase output more than by-passing the controls would have. The L-pad at maximum rotation is the same as by-passing an original pot.

Regarding your AR-3a Improved project.

-The #16 coil does not look original. Measuring them is the only way to be sure.

-In 1974 (yes, that is when your woofer was manufactured) AR was still using some front-wired tweeters with the original terminal board, but switched to back-wired mids along the way. Your mids are most likely original to the cabinets.

-The 3a type tweeter (A.19 or A.23) would be original to the Improved, but the AR-11/10pi tweeter (A.24) would work better today.

Roy

[TimmyTonga]

 

 

On 23 July 2016 at 6:54 PM, RoyC said:

Tim,

If your pots were functional the L-pads will not improve the output of your AR-3a tweeters to a significant degree...and they certainly will not increase output more than by-passing the controls would have. The L-pad at maximum rotation is the same as by-passing an original pot.

Regarding your AR-3a Improved project.

-The #16 coil does not look original. Measuring them is the only way to be sure.

-In 1974 (yes, that is when your woofer was manufactured) AR was still using some front-wired tweeters with the original terminal board, but switched to back-wired mids along the way. Your mids are most likely original to the cabinets.

-The 3a type tweeter (A.19 or A.23) would be original to the Improved, but the AR-11/10pi tweeter (A.24) would work better today.

Roy

Thanks for the confirmations on the Improved Roy. Rarely see 11s or 10pis over here, and I've never seen an A24 tweeter for sale. Perhaps these will have to be parked a bit longer.....

With regard to the 3a and the VintageAR L-pads, I fitted them yesterday and the amount of extra energy you get from the tweeters is considerable - I would say you get another 3db to play with. I went from having not enough top with the 15ohm pots to having too much with the L-pads and having to turn them down. I'm assuming this is because they are 8ohm, and perhaps consequently this is causing compromises elsewhere in the crossover, but I must say there are none immediately apparent to me.

They are a pig to solder in, but the second one was much easier then the first once I established a MO. I haven't changed the pot on the mid, which works fine.

What is rather unexpectedly heartening is that the tweeters don't seem to have lost the super-highs that people sometimes call 'air' - around 16-20k. I can't hear these as tones anymore, but pick them up in programmes well enough. Overall the tweeters seem well-balanced throughout their range.

Which is pretty amazing when you look at the state of the three blobs of foam holding them in place....

Tim

 

 

[TimmyTonga]

....but having said that, I am now going to stick a 25 ohm resistor across pins 1&2 on the Lpad and clock the difference.

[RoyC]

5 hours ago, TimmyTonga said:

....but having said that, I am now going to stick a 25 ohm resistor across pins 1&2 on the Lpad and clock the difference.

The L-pad lowers the crossover point and provides more power to the tweeter, especially at maximum rotation. The parallel resistor compensates for this. If the tweeters are still louder at each setting (other than maximum) with the resistors installed, your original pots were probably not working properly.

Roy

[TimmyTonga]

Hello, nearly finished. Could someone please confirm or otherwise that with an Erse MET cap I don"t need the 0.27 ohm series resistor?

many thanks,

Tim

[RoyC]

4 hours ago, TimmyTonga said:

Hello, nearly finished. Could someone please confirm or otherwise that with an Erse MET cap I don"t need the 0.27 ohm series resistor?

many thanks,

Tim

You don't need the resistor.

Roy

[TimmyTonga]

Thanks Roy.

[TimmyTonga]

So here is a wrapping-up kind of post, as the pair of 3a Improved are parked indefinitely until some of the right tweets show up. The two pairs of 3as are, I think, finished. The interior looks like this; when I restuff the cabs I will paste a photo of the new 6uf cap inside the box somewhere unobtrusive....

I ditched the L-pads and reinstated the pots because;

• without 25 ohm resistors and with repeated listening it became apparent they distorted the upper-midrange FR curve, and not in a good way. With the resistors, they offered no advantage.

• there was less phase-coherence in the upper mids, which I put down (not necessarily correctly) to a frequency overlap between tweet and mid unit, due to the crossover point of the tweet being lowered.

• I was constantly anxious that the tweeters would be dealt a fatal blow by a crash cymbal.

• they didn't look right

 

One pair has extremely well-balanced tweeters, which allowed me to put a jumper between B and 1 on the hi pots, and remove any doubt as to whether they were at max or not; and also avoiding that 'dead' spot just below max. Whoever I 'give' them to in the future can choose between the jumpers or the pots.

 The other pair had one extremely energetic tweeter and one subdued, which meant I was resigned to having the pots active. Given that the paper certificates have serial numbers of 01953 and 01703 I can't account for this disparity. I haven't taken the tweeters out to see if one was a service replacement (and don't intend to).

Just so I couldn't say 'what if' anymore, I put a 0.28 ohm series resistor alongside the mid-range film cap, glued to a piece of self-adhesive neoprene, which is attached to a brace.

All four mid-unit pots sit fair and square on the white dot. This sounds absolutely right to me, and the idea that the 'flat' position is somehow achieved with the pots on max is a complete head-scratcher. (I know that letter has been much discussed, and I may post separately about it, as it raises some interesting questions).

All the woofers were saved, and Klaus's repair lives on!

 

As someone who was brought up on Tannoys, I was dubious as to what the AR3a could possibly bring to the party. But they are, for their size, better than any competition. There are not many speakers that will deliver that low-end curve; the fantastic tightness and depth, but without any of the fluffy indeterminate boom that so many other speaker manufacturers call 'bass'; it's the first domestic speaker I've heard that doesn't seem to have a hump at 150hz. The midrange too is exemplary, although possibly a little 'shouty' at high volume; however I'm quite prepared to concede this might be due to my ears getting more sensitive as time goes on. 

I've been listening to them flat, with a fairly neutral amp. If I was prepared to plug an EQ unit in, I would probably add a 2db shelf at 10k; the speakers may have been designed to be this dark, but for my money that's what they would need to give the kind of detail to the top end that you would expect in 2016. Expectations were different in 1974.........there's probably a few people on this board remember what an AR3a sounded like straight out of the factory, but the tragedy is that because their hearing has deteriorated with age, the only datum level they have for the top-end is in their heads....   : )

we will never know....

Thanks to all for their advice, and of course the restoration document - the existence of which single-handedly inspired me to start an AR journey, and without which I would have been completely stuffed. Even for someone with incomplete electronic skills, you read it - and you think yes, I can do that.

Next up  - a pair of MSTs....

tim