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AR 12 WOOFER QUESTION


lARrybody
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In April I acquired a set AR 12 speakers in relatively good shape. The tweeter and mid range are in excellent shape, but unfortunately the woofers are replacements. Even with the unknown woofers and the original crossovers they sound excellent.   There are pictures on page 4 of GD70's recap post.  

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/8721-ar12s-restored-a-few-pics/&page=4

The examples on the web have been rare and expensive. RaRa posted that some of the late production AR2ax's used the same woofer. Last week I found a pair in good shape for about one third what the others were. They both test out right under 8 ohms each. New foams are on the way. 

 

 CIkDJ4Q.jpg

 

w2FmNeE.jpg

Here is my question. These have the flat dust cap of the 2ax. The ones on the AR 12 had a second dome dust cap added. I have some 65mm paper caps that look like a good fit. Did the original AR 12 woofer have mesh caps or paper caps? Cannot tell from photos. Some of the 8 in AR woofers that had double caps with the second being mesh.  Thanks in advance for checking for me.

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Hi Larry,

This is just a wild stab at one plausible explanation, all based on information from the Library archives. The first two images show the two versions of the flat dust cap, which probably pertains to all of the original 'Classic' models with 10" woofers: AR-5, AR-2ax (and 2x), AR-LST/2 and AR-8. The third image shows all of the drivers from the ADD series that followed, and you can see that all woofers shown have domed dust caps.

When you look closely at the assembly drawing for the 200004 woofer, additional clues are revealed, and you can see multiple production changes made to this driver over many years. Not only have some original material components been erased or deleted entirely, but the list of revisions literally goes from A to Z, and beyond. Most notable are these notes about dust caps: at some point (Revision "U") a second cosmetic cap was added over the original flat cap. I suspect this was implemented to bridge the production from 'Classic' to ADD series, and to use up the inventory of flat-cap woofers in the new series but with a refreshed appearance. Once these flat-cap woofers were exhausted, Revision "Z" was most likely implemented and the subsequent woofers for the AR-12 and AR-14 used only the single domed cap. After all of these various revisions, this is what shows up on the 200014 drawing in the Library, as shown in final attachment here. Not sure if these caps were made of paper or another material, but I doubt if any were a mesh material which would allow air to pass through.  

5b1345c4b7fb9_200004dustcap.thumb.jpg.445c080c8b6e1010b5b20766b0f6ec05.jpg

5b1345d7bff67_200004-2dustcap.thumb.jpg.eeffc8857cdc82ed516936874955082c.jpg

5b1345f80c5a3_ADDdrivers.jpg.52f2b376b12ffcbb2f1de9c6f6c3e454.jpg

5b134bc23715c_200004revisions.jpg.699b8cc29de4df7aecf0379cc0756757.jpg

5b134fc639b52_200004profile.thumb.jpg.d2293ee75a945dcd4b6998097d4c8e6e.jpg

 

 

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ra.ra you are a wealth of information. Mine are the dust caps in the second attachment. Mine measure around 55mm and AR has them at 53.848mm. Close enough. I may have just answered my own question by rereading GD70's original post over at Audiokarma, Page two.

http://audiokarma.org/forums/index.php?threads/ar-12-restoration-pics.698197/page-2

I will be ordering some 2.25 in. (57mm) mesh dust caps from Midwest Speaker and they should fit perfectly over the original flat caps. 

I suspect you are right about AR adding the dome dust caps to the 200004-2 woofers when used in the ADD series to make them appear more modern. Mine originally came from some late production AR2ax's, thus the flat dust cap. My 2000040-0 woofers in some AR38S speakers have a single solid dust cap. The Dayton caps arrived yesterday so i can get busy on the crossovers waiting for the woofer parts. Maybe I just do one crossover and  woofer at a time so i can compere with what i have now. They already sound excellent.

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2 hours ago, larrybody said:

I may have just answered my own question by rereading GD70's original post

Yeah, that AR-12 restoration thread by Glenn is simply terrific, and the pic attached here (credit to GD70) must be what you're referring to. The entire tutorial is filled with useful information and great pics, but my favorite parts are the restoration of the unique mid drivers and the creative work to build entirely new grille frames. In the same thread, michiganpat shows off some excellent grilles he fabricated for his AR-58s speakers. Also in that same thread is a pic of AR-12's with flat dust caps, but I presume those woofers were scavenged from AR-5's or 2ax's.  

The earliest version of this woofer has the alnico slug magnet and then went to the square ferrite magnet (as you've shown here). In other threads, you and RoyC have shown the various 4-hole and 6-hole basket frames to fit the appropriate openings in the cabinet prep, so we know there are several versions of this woofer that fall under the 200004 part number. What escapes me, however, are the particular differences that designate the dashed suffix for this woofer - - - as you've indicated, your specimens include both the 004-0 and 004-2 varieties. With your terrific collection of vintage AR's, you've probably got more specimens of this p/n 004 10" woofer than just about anyone. :lol:

200004 dust caps.jpg

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Yes, a wealth of info and nice work!

I have a pair of AR-48s with the correct ceramic magnet woofers do you all think that they

are roughly the same as the AR-5 ceramic woofers?  Based on AR published Fs, Fc and Qtc

I'd say that they are but what about the impedance?

Edit:  Should have checked my own work, AR-48 woofers have RDC = 6.4 and AR5/2ax 4 bolt

woofer RDC = 6.8 so I'd say they are the same within reasonable tolerances.

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I wouldn't know how to address this question since it appears that the woofer part no. is different and locating published material on this series (the 'S' series) of AR's seems to be a bit scarce. The 10" woofers discussed here are p/n 004, but the woofer in the AR-48s seems to be p/n 040, which I think was also used in the AR-14 two-way model.

The Drawing section of the Library has plenty of good info on the 48s model. You can find cabinet construction, final assembly, crossover, and even individual driver drawings, but I'm not sure if there are any spec test documents. Not unlike the AR-12, however, the 48s is a 10" three-way with a cone midrange with its own separate enclosure. The only other 10" three-way produced in this relative time period is the AR-92 - - but that's a very different speaker with dome drivers in a vertical format - - so I think it could be said that the AR-48s is pretty much a direct descendant from the AR-12. The ad attached shows the AR-48s in the lower right corner.

AR-48s parts.jpg

AR-48s series ad v2.jpg

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The one year wonder...the 12...and what AR tried to do was offer a "rocknroll" speaker for which it was advertised as.

All I know is when I got my mids done and had them in my great room on the carpeted floor. ...they blew me away with their sound. I just wasn't expecting it. 

So, I threw on Dark Side of the Moon on since I saw them advertising it for such a band and cranked it up. It sounded phenomenal. Even my son came from the other side of house to the landing and asked what speakers I was using!...lol. He loved it...and said it was coming in clear in his bedroom. I told him 75 watts baby...

That mid on that thing was clear and forward....and bass was deeper than on any if the other 10" AR's I had listened too. They got it right for a rocknroll speaker.

.

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I lugged (5) that's FIVE of these woofers around with me and (2) original cast frame types for TWO HOUSE moves - for a Grand Total of SEVEN AR 10" woofers, all from 2ax(s)

Four were from consecutively numbered boxes 

NO BODY wanted 'em, including the vintage AR guy who sells on ePay (and is a member here)

Could not give them away, even on craigslist

All were perfect, measured well, just needed foam (except the cast pair obviously, one of those had the shitty spider glue syndrome)

I had gone with Layne Audio woofers in these particular restorations (why I had so many)

Couldn't bring myself to doing anything drastic with them until I just got sick of looking at them/making space for them so about 5 years ago I just shit canned them (literally, on trash day) - couple of late production tweeters too with the plastic flanges and "AR" stamped in them

Now, everyone wants them to the point of parsing serial numbers and magnet types

You know, if you're going to get involved in this hobby you almost need a warehouse

It's worse than collecting anything - it always seems to just grow

Craig

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  • 3 weeks later...

Just want to go over my AR 12 woofer swap and re cap. A couple of weeks ago I installed new foams on the 20004-2 woofers and re caped one of the speakers. I used Dayton polys with Dayton film .01 bypass caps. I used two 3uf 1% Dayton's  in parallel with a Audiocap Theta .01 for the bypass on the tweeter cap. 

8FeFiJO.jpg

4cONCP8h.jpg

I also purchased new mills resisters (12 in total), but after inspecting the potting goop on these euro built crossovers I decided to forgo trying to remove the existing resisters embedded in  this mess. Not the hot glue I normally run across but some king of rubbery silicone that is impossible mess to melt and very difficult to cut away.  The 40uf electrolyte capacitor is quite a contrast to the new poly.

homCxfnl.jpg 

Here is one finished and I hooked it up with the existing speaker and listened for a few days. First I noticed the new speaker played slightly louder than the untouched one. Probably due to the more efficient AR woofer, because I doubt that caps could make a difference in sensitivity. The recapped speaker defiantly was more detailed, crisp and forward in both flat and -3db positions. The bass was tighter and slightly deeper than the original non AR woofer speaker. It was apparent the recapped speaker was more dominate ,relegating the original to the background.

iopq0tYl.jpg

Last week I recapped the second speaker to bring it up to snuff, which it did. Interesting enough according to my meter the original caps were not that far off. 

wdjL01Zl.jpg

Another interesting spec is the difference in weight between to generic replacement woofer and the AR 20004-2.  Almost 2lbs.

RdM7X11l.jpg

I am liking what I hear. Time to start swapping out different amplifiers and thinking about cosmetic improvements. Right now I am enjoying these. As lakecat has  has stated, these really are some rock and roll speakers.

 

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  • 4 weeks later...

Thanks for the kudos gents and glad to see the thread is a helpful reference.

As ra ra has shown the variations, Roy told me they will all pretty much sound the same.

I'm pretty anal regarding originality, but the similar replacements should perform well.

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