AR-6's with zobel

[ra.ra]

The magnet stamp indicates production in the first week of '74, and 561 is some other code designation I've seen on other AR 8" woofers as well. Not sure if this is helpful or of interest, but the three attachments below are from the AR system assembly dwg. for the AR-6 speaker. The first is a parts list, and the second notes revisions made to the assembly drawing. The third shows two pictorial views. The original woofer is noted as part no. 200001, but revision E suggest an "alternate AR-6 woofer", and then calls it "AR-7-10708" if I am reading this correctly. This seems consistent with your woofer.

The drawing has a final engineering stamp date of Dec. 1976, but the origin date of this drawing is unclear - - in fact, it's box is incomplete. I was somewhat surprised to see that this drawing represents what I've referred to as version 3 (no coil and 2 position switch) and it's still unclear whether this was ever a model produced in the U.S. The crossover assembly designation (800009-1) is identical to the one listed on the similar drawing for the AR-7.

If you can, include a pic of the woofer and the revised x-o with your next update.

[genek]

I thought the earlier thread contained the 3-crossover diagram but I'm not seeing it there, so here it is again.

[ra.ra]

Thanks, genek, this is interesting - - - I'd never seen this last version of this holy triad. However, this is the second different schematic for this speaker to be posted here in recent days (see attachment comparison) and while similar, there are indeed differences. Klaus' schematic shows three wire terminals, a 6 mf cap and tweeter negative wire connected to terminal 1 (common). Your schematic shows two speaker terminals, a 10 mf cap, and tweeter negative wire connected to terminal 2 (hot).

The second attachment here, from the 1977 parts list (page 3), compounds my confusion just a bit more. The 'complete' crossover for the AR-6, AR-7 and AR-4xa is listed as the same part number (800009-1), so not only am I now somewhat perplexed about the correct cap values (6 or 10 mf?) for these speakers, but this would also seem to suggest that the 4xa maybe had no coil, which is inconsistent with the schematic (see attached) I recently located.

[kcbluesman]

If you can, include a pic of the woofer and the revised x-o with your next update.

Ra.Ra -

I don't have a working, high-quality digital camera right now, so no pics.

My crossover is the same as ( in the schematics provided above by Genek, but my woofer is the 10708 ( produced in January 1974), not the 200001, and the spider is attached to a masonite ring.

I started a separate thread - AR-6 Crossover Comparison - regarding my subjective comparison between one pair of my AR-6's in stock form (crossover B in the Genek schematic) and the other pair modified to the match the schematic provided by Klaus, above. The only difference is that I left my three-way switch intact, rather than convert it to only one resistor (and two settings). All woofers have new surrounds and all the caps are new Dayton Precision poly.

Here is the link to this new thread: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7566

My only other comment is that my AR-6's do not appear to be "european" versions...the cabinets are the same as US versions I have seen (as opposed to the more detailed front edges that I've seen on at least some pics of euro versions), and the labels on the back show AR's USA address.

I made the same comment earlier in this thread, but just wanted to help keep things straight for anyone who may be following along!

[kcbluesman]

Darned editing tool....the smiley face is supposed to be a B in parentheses....it didn't display the icon until after I posted.

[KlausDK]

Klaus -

I am planning to modify the crossovers in one pair of my AR-6's (the ones with the zobel glued to the woofers) to duplicate the crossovers in the "latest European version" that you referenced in your posting.

However, before doing so I would like to know if you believe the drivers in my version to be the same (or very close the same) as those used in that European version. I'm not sure that I want to move forward if they are significantly different.

On a related note...my web searching seems to indicate that my AR-6's are also referred to as a European version. Do you know if this is correct? The labels on the back of each ot them show AR's USA address.

And one final question to further take advantage of your expertise....as I noted earlier in this thead, my woofers have a masonite ring under the spider, and the outer edges of the surrounds are glued on TOP of paper gaskets in the outer rim of the basket. Any ideas as to the purpose of the masonite ring?

Thanks very much for any help or insight you can provide.

The woofer in the simple 6 uF capacitor x-over version is without the Masonite ring (by AR called the 8" universal woofer). I do not know if the masonite ring version woofer has the same roll-off of the high frequency area, but I doubt they are the same.

Could you post pictures of your speakers, that would make the identification easier, but if they were bought in Asia I doubt that they are European versions. I believe that they would also have had the European office address in addition to the US office address, if they were European made.

I don't know the purpose of the masonite ring under the spider, but a similar ring is used under the original ceramic magnet 12" woofer used in AR-3a and onwards. I assume that it has something to do with adjusting distance to avoid the voice coil to "bottom" the magnet, and again I do not know, but I assume that the paper gasket/masonite ring on the outer rim would serve the same purpose, add distance.

I have enclosed a picture of the outer rim of a later European version AR-6, where you can see that it is smaller than the US cabinet version of AR-6. Early European AR-6 had same cabinet as the US produced.

BRgds Klaus

[ra.ra]

For some reason today, I could not get these drawings from the library to open for me - - - but perhaps there is some explanation on the purpose of the masonite ring (see first attachment).

Many Euro versions can be easily identified by at least three features: the narrow profile wood edge at the front face of the cabinet; the speckled paint on the backside; and the mention of UK or Dutch address on the s/n card. I'm not altogether certain, but I think Euro models all had rear-wired tweets, too. Just for information or comparison, I've attached a few various images of AR-6 speakers, plus one pic of woofer 200001 (with no masonite).

[genek]

The AR-6 drawing clearly shows that it is for the later version of the product with a switch rather than a pot. I've never seen the inside of a 4xa, but I have seen the inside of a 7, and it definitely had no coil, only a cap. I'm guessing that the common 4xa/6/7 crossover in the service parts list is for a coil-less cap-only circuit and that the 4xa, like the 6, started out with a different crossover, at least in the US. Unfortunately, we haven't seen the insides of enough 4xa's and have never found an official AR-prepared crossover diagram for the 4xa.

[Rlowe]

I thought the earlier thread contained the 3-crossover diagram but I'm not seeing it there, so here it is again.

The attached UPDATE of the 3-crossover diagram has been amended to show the original 6uF capacitor in the ( C ) Crossover.

I have confirmed with Klaus that I inadvertantly left the 10uF while "cut & pasting" the Crossover circuits.

Sorry.

AR6-3 Xovers update Nov2012.pdf

[ra.ra]

Thank you, Rlowe, for looking into this and updating the schematic for version C. From what I have compared, this update now seems identical to the x-o in the AR-7, which is what kcbluesman has already confirmed from RoyC in post #9. Thinking about these late model, small cabinet, 2-way speakers that AR marketed simultaneously (AR-4xa, 6 and 7), I suspect genek is probably correct that the 4xa, much like the 6, had more than one version of crossover circuitry. And if, in fact, the later version of the 4xa x-o is also identical to the x-o in the 6 and the 7, then it seems to me that the only variable among the three speaker models at that point is cabinet volume.

As I posted in a different but recent thread (and again here), the only 4xa schematic I've ever seen is quite different and includes a coil, a 10 mf cap and a three position switch.

[ra.ra]

The 1977 parts price list seems to confirm that both the AR-6 and AR4xa (and MST-1?) models each had multiple crossover designs that implemented 6mf and 10 mf capacitor values.

[Joel]

My MST's only had two caps in them- 2uf and 10uf. Mine were labeled as "MST Improved". They were the 3 tweeter versions. More info them can be found here: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7446

-Joel

[ra.ra]

Yep, I've been following your thread on the MST's and encouraging you to try to get a second speaker up and running, and because of the paucity of information on this particular model, the several variations of this speaker remain somewhat obscure. In fact, I've never even heard of an MST-Improved - - - maybe this was the identification for the model change from four tweet to three tweet? - - - nor have I seen any MST schematic with a 2uf cap even though it is shown in this price list. Your notes seem to confirm that the MST, not unlike the AR-6 and the 4xa, most likely underwent design modifications after the initial release of these speaker models.