AR-2ax Project

[lARrybody]

6 hours ago, JKent said:

Even cheaper--these are sold by several ebay sellers. My technician recommended it so I'm guessing it's a great deal for about 6 bucks 

These test many kinds of components and even identify what the thingy is when you attach it. No case but you can make your own.

Hey I have one of those. Couldn't figure out how it works. No instructions. It measures ESA and that is a plus. I wonder if there is a PDF of a owners manual out there somewhere?

1 hour ago, stupidhead said:

 

Hey Michael,

As I suggested in your AK thread, if you source a set of cloth surround woofs the Masonite ring issue goes away, the inductor issue goes away, and these worthy candidates are closer to OEM. Just a thought.

 

That would be ideal. Even the larger woofer frame with the foam surrounds use the #5 inductor according to Roy.  Just purchased a supposedly un touched original pair off the auction site last night. Item Number 182968061807  Low serial numbers 40611 and 38728. Grills supposedly never removed. If they are what I think they are my current pair of early AR2ax's will be offered up. 

[Glitch]

31 minutes ago, larrybody said:

Hey I have one of those. Couldn't figure out how it works. No instructions. It measures ESA and that is a plus. I wonder if there is a PDF of a owners manual out there somewhere?

Google "gm328 transistor tester manual" and you will get something from the same family (I'm pretty sure).  Many of these meters seem to have common roots, but are slightly different depending on where you buy it.

This link  http://www.avrtester.tode.cz/upload/ttester_en.pdf seems to be an up to date version.

The version that I have sometimes does things that are a mystery to me, especially when it gets into calibration mode.  Overall, it does a pretty reasonable job.  It provides readings that are consistent with some of my more expensive equipment.

[dxho]

aka mega328 or atmega328

[lARrybody]

Thanks for the info. A wealth of reading to do. I am thru hijacking Michael T's post. It is all about getting his AR 2ax's up and running. Wish everyone a good holliday and may the new year bring us more classic speakers to refurb.

[Michael T]

I'm looking at veneer and I'm a little overwhelmed. I'm guessing I should go for raw (unbacked). Outside of that I'm not sure what to look for. There are different types of walnut, there are a number of manufacturers and distributors and I'm not sure if there are different thicknesses.

Any suggestions on what and where I should get for repairing my cabinets?

[stupidhead]

you can likely find a set of donor speakers on craigslist, goodwill or other type of place. peeling off old veneer is not tough and it didn't look like you had to much patch work to do from the pics.

[ra.ra]

6 hours ago, stupidhead said:

....find a set of donor speakers .... it didn't look like you had to much patch work to do from the pics.

Unless there is some damage that we can't see from your pics, I would agree with this approach. No need to go shopping and get yourself confused. If it's only a few square inches of walnut veneer that you need, I might be able to furnish some decent scraps for use. Send me a PM if interested. My "donor" would be a very rough empty AR-3 cabinet, so I would assume the veneer thickness is essentially identical to your cabinets.

[Michael T]

On 12/22/2017 at 4:03 PM, stupidhead said:

Hey Michael,

As I suggested in your AK thread, if you source a set of cloth surround woofs the Masonite ring issue goes away, the inductor issue goes away, and these worthy candidates are closer to OEM. Just a thought.

Geoff

I ended up getting woofers with cloth surrounds. I got a bit anxious and probably paid more than I should have. But I really do want to get these speakers OEM.

Something I've been meaning to ask: should I put the old nasty mineral wool back in when I'm done? I have access to new ceramic wool if that would be a good match. What is my best route?

I'll be starting on the cabinets this week. I realize that I won't be using 80 grit sandpaper on the veneer, what grit should I start with?

[JKent]

26 minutes ago, Michael T said:

should I put the old nasty mineral wool back in when I'm done? I have access to new ceramic wool if that would be a good match.

If your speakers have rock wool get rid of it. If it's fiberglass it's OK. If you want to replace it use plain ol' house insulation. The new stuff from Johns Manville or Owens Corning is formaldehyde-free. Home Despot and Lowes sell it in small bags, about 12 oz each.

-Kent

[RoyC]

21 minutes ago, JKent said:

If your speakers have rock wool get rid of it. If it's fiberglass it's OK. If you want to replace it use plain ol' house insulation. The new stuff from Johns Manville or Owens Corning is formaldehyde-free. Home Despot and Lowes sell it in small bags, about 12 oz each.

-Kent

Hi Kent,

Lately I have been using the small bags of yellow insulation found in the hot water heater insulation area of Home Depot. The bags hold about the same amount as the other type (which is actually closer to 9 oz), but it tends not to expand as much.

https://www.homedepot.com/p/E-O-3-4-in-x-16-in-x-48-in-Multi-Purpose-Fiberglass-Insulation-SP1-12/100187670?MERCH=REC-_-PIPHorizontal1_rr-_-100032413-_-100187670-_-N

Each cabinet takes about 2.25 bags each.

Roy

[ra.ra]

2 hours ago, JKent said:

If your speakers have rock wool get rid of it. If it's fiberglass it's OK.

JKent et al, I need to ask - - - why has this response become such an automatic blanket statement from some enthusiasts? I have re-used original rock wool in multiple pairs of restored AR-4's and am duly impressed with the speakers' performance(s). Can someone state with assurance that a vintage speaker restoration will result in superior performance when new fiberglass stuffing replaces the original rock wool? Many have opined that mineral wool contributes to accelerated pot corrosion, but I am not yet buying into that theory.  

[RoyC]

1 hour ago, ra.ra said:

JKent et al, I need to ask - - - why has this response become such an automatic blanket statement from some enthusiasts? I have re-used original rock wool in multiple pairs of restored AR-4's and am duly impressed with the speakers' performance(s). Can someone state with assurance that a vintage speaker restoration will result in superior performance when new fiberglass stuffing replaces the original rock wool? Many have opined that mineral wool contributes to accelerated pot corrosion, but I am not yet buying into that theory.  

John O'Hanlon, our 3a restoration guide scientist, postulated that the high sulfur content he measured in it contributed to the corrosion of the pots. I personally hate the stuff. Just touching it makes particles become airborne in great quantities. I hope nobody is dealing with it indoors and/or without a filter mask. On the other hand, I always retain the post 1970 clumpy yellow fiberglass.

Roy

[ra.ra]

10 hours ago, RoyC said:

....the high sulfur content he measured in it contributed to the corrosion of the pots.

Yes, I've read these thoughts in the past, and while I have no reason to doubt John's conclusions from his own case study or even his theory about the sulfur, I just haven't seen any consistent relationship between type of stuffing and the level of pot corrosion. In fact, if I were allowed to cherry pick from my own examples and experience, I could practically make the contrary argument. I've encountered pots from rock wool cabs with relatively little corrosion; and I have found pots from FG cabs that were totally unusable.

Re: rock wool, I'm beginning to now think that my few encounters with this material may have been somewhat atypical. I have no love for the stuff, but it's never caused me such irritation that I've felt the need to replace it. Several voices in this forum have agreed with Roy's disdain for mineral wool insulation, but I've found little difference between handling it and early fiberglass fill (pre 1970?). Of course any stuffing needs to be handled with care and some degree of protection (hands, nose, eyes) - - - both materials are packed in with handful-sized random clumps, but I often encounter some level of irritating loose fibers when removing and replacing fiberglass fill as well.   

      

[Michael T]

It seems that the question that was here has been answered in a previous post. 

[RoyC]

1 hour ago, ra.ra said:

 Several voices in this forum have agreed with Roy's disdain for mineral wool insulation, but I've found little difference between handling it and early fiberglass fill (pre 1970?).    

Our experience obviously differs. The later yellow clumped fiberglass is much more stable. Try handling the old stuff in sunlight next time and watch the cloud.

The stuffing discussion is actually quite technical. This is only part of one that took place some years ago.

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/2080-ar-4x-cabinet-damping/

Roy

[Michael T]

On 12/27/2017 at 1:53 PM, RoyC said:

Our experience obviously differs. The later yellow clumped fiberglass is much more stable. Try handling the old stuff in sunlight next time and watch the cloud.

The stuffing discussion is actually quite technical. This is only part of one that took place some years ago.

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/2080-ar-4x-cabinet-damping/

Roy

Well...that was a fun read. It sounds like once a speaker is opened you've basically ruined it for sound, if you listen to some of those guys.

Seriously though, that's a lot of technical info. 

[genek]

You only ruin the sound if you open the speakers and don't put them back together again the right way.

[Michael T]

Having said all this, I am continuing with my restoration and will still be asking for advice and help but I have enough info to get me through the next week or more. This will give my brain a chance to clear out (I have ADD so I am easily overwhelmed). So I'll simply post pics as I go for a bit.

Thanks for you patience with me.

[dxho]

Tune it to your taste. That's what everyone else does :-)

[ra.ra]

On 12/27/2017 at 1:53 PM, RoyC said:

Our experience obviously differs. The later yellow clumped fiberglass is much more stable.

Yes, I'm beginning to think likewise, Roy - - my few experiences with rock wool in the old AR-4's just never elicited the type of strong responses that others have decried about this "wretched" stuffing - - - perhaps my specimens simply had not experienced the normal level of degradation? I just dunno. And yes, I agree, the later fiberglass works very well and is indeed more stable and easier to handle. 

Upon re-reading the 3a restoration guide, there are a few mentions, but not any real discussion, about rock wool fill. The consensus advocacy (underlined and italicized) is for the use of fiberglass fill - - and I'll go along with that - - but one statement (in part 4.3, page 21) led me to think that perhaps there is a performance benefit for using fiberglass in lieu of rock wool, which states that rock wool fibers do not increase the cabinet volume as well as FG. This makes me wonder if maybe I missed an opportunity to improve the LF performance of my AR-4's by using original rock wool instead of new fiberglass.

And thanks for that technical link (re:stuffing) - - while it is enjoyable to see the level of study that several members have conducted, that is far more information than I will ever be able to digest and put to use. Much of that thread is way above my pay grade and makes my eyes glaze over. Nonetheless, there was one particular part of the discussion that caught my attention - - - Carl was reporting on the restoration of a pair of early 3a's with alnico woofers and rock wool fill (28 oz), and seemed to be pleasantly surprised with his results using a lesser weight of new FG (20 oz) fill, rather than the amount (28 oz) prescribed by the 3a restoration guide. 

Through interpolation, can this be interpreted to suggest that my AR-4's - - - or Michael T's 2ax's with rock wool, for that matter - - -  might benefit from the replacement of original stuffing with a lesser weight of new FG fill?   

(Note: Apologies to Michael for this unexpected detour here in your 2ax thread. ) 

[Michael T]

1 hour ago, ra.ra said:

 

(Note: Apologies to Michael for this unexpected detour here in your 2ax thread. ) 

No probs. I think what you said about eyes glazing over and pay grade was a nicer way to put what I had said.

I will say that it is great that people are willing to share their knowledge and that there are some extremely knowledgeable people here and at AK. I will also acknowledge that there are people who will appreciate such in depth studies. I am just not quite there.

I'm kinda used to having my threads led around a bit, the detour about the meters earlier and the guy wanting to refurbish his cherry speakers over in my thread on AK :). It's all good.

 

[GD70]

Hi Michael,

With any first time restoration, it's easy to be overwhelmed. I sure was! There will always be detours along the way with the different experiences we all have, our opinions as we approach each step differently, parts we like to use etc...

Focus on one step at a time, take lots of pics for reference for when reassembling, and to show us your progress.

Glenn

 

 

[Michael T]

17 hours ago, dxho said:

Tune it to your taste. That's what everyone else does :-)

Yes, that is what I figured. I hate to do it but my expenses have already exceeded my anticipated level so I'll save a few bucks now and put the rock wool back in. At least I know that this part will be original. If they last me 20 years, by which time my hearing will be to the point I won't know the difference, I can give them to my son and show him how to restore them.

[RoyC]

There is plenty of basic information in this forum to get AR restoration candidates back into the "original" AR ballpark. Although it sometimes involves choices regarding approach, it is not difficult to achieve that goal. Bear in mind that the drivers of the old beasts are often around 50 years old, and unknown differences in wear and performance are much more significant than the recent cabinet stuffing discussion, as well as others that often take place regarding such things as types and brands of capacitors or level controls, etc.

Things can seem complicated and/or overwhelming when subjective answers are given to basic repair questions, or when an inexperienced person asks questions which cannot be answered simply (ie the recent AR-11 vs 3a crossover questions, and the stuffing question Michael deleted) which touch on the technical aspects of speaker design. Books are written on these things. Michael's 2ax's have as much chance of sounding like an original pair of AR-2ax's as others whose owners are wringing their hands over the use of L-pads or pots, the retention of original stuffing, or Solen vs Dayton capacitors...among other geeky considerations.

Ra.ra and Michael, I did not expect most folks to understand the technical aspects of the link I posted about cabinet stuffing. I was just letting it be known there are sometimes no simple answers. An even more detailed discussion took place subsequent to that thread by email which had my eyes glazing over as well. Ken Kantor referenced a very technical paper he wrote on the subject. Fiberglass is considered to be the best material for cabinet stuffing. I personally conducted measurements of various amounts and types of stuffing in AR-3a cabinets, and compared notes with John O. and Carl over a period of months. The conclusion was that fiberglass yielded the best results in amounts of 20 to 28 oz in the 3a. (I think someone at the AR factory must have been jumping up and down in the woofer hole to make 2+ lbs of that early rock wool material fit into the cabinets. ). Primary variables were differences in the compliance of the woofer suspensions and the effects of wear on same. Earlier, more compliant woofer suspensions worked better with more stuffing. The later, stiffer woofers worked better with less....but these variations did not compromise restorations to a significant degree. When AR went to the yellow fiberglass in all models around 1970, the amount of stuffing was reduced. Around the same time, woofer inductor values were reduced as well. It is not known if these two changes were connected. Ask "why" at your own peril. Better yet, don't ask why and enjoy listening to your repaired speakers.

Roy

[ra.ra]

48 minutes ago, RoyC said:

Bear in mind that the drivers of the old beasts are often around 50 years old, and unknown differences in wear and performance are much more significant than.......

Thanks again, Roy, for bringing us back to Earth with this excellent summary - - - and this statement that you have made a number of times in this forum is maybe the single most important thing I remind myself with any of these restoration projects. Even though I did once-upon-a-time purchase a single pair of AR speakers in "new" condition, it was over 40 years ago and I can no longer claim to have specific recall of those original sound characteristics from when my ears were younger. So in my projects, my modest goals are to get the speakers looking good and sounding good with minimal but prioritized investment and possibly make some modest compromises along the way. And that's always been good enough for me to have some fun with this hobby.

If there is ever a next encounter, I'll probably give more immediate consideration to ditching the original rock wool.