Yet another AR-3 project

[RoyC]

18 hours ago, mvboland said:

Perhaps as expected, the bass response is much improved with the speaker in that position.   The frequency plot below is with a calibrated microphone at 1 meter (red line - still showing some room acoustic artifacts) and right in front of the woofer (orange line).  Still lacking a home anechoic chamber but both are much flatter than the ones above.

In terms of the missing screw, I do still believe that was a factory boo-boo since the sealing putty that had filled the hole was painted over (just like the screws) and the t-nut underneath worked great fine once I got a new screw.

In my experience, room placement and room acoustics are the most overlooked aspects of speaker evaluation. It is why audio forum pronouncements of such things as "required" amplifier power, for example, should be taken with a grain of salt.

Regarding the missing screw, I have found a number of AR screw issues over the years in untouched, all original specimens. In every case it was one loose or missing screw covered by putty. Dislodged T-nuts have been the usual cause of this apparent "repair", and it was certainly easier to maintain the integrity of the cabinet's seal with some putty than to remove the entire driver. Bear in mind that the grills were securely glued in place, and nobody at AR was expecting this conversation to be taking place nearly a half century later.

Roy

[tysontom]

On 2/5/2023 at 8:47 PM, mvboland said:

Thanks as always to @tysontom for sharing AR wisdom.  I was led astray after going down a YouTube rabbit hole on speaker placement as modern speakers seem to be best away from walls. Instead, I should have paid more attention to item #4 on the decal on the back of the speaker:

Perhaps as expected, the bass response is much improved with the speaker in that position.   The frequency plot below is with a calibrated microphone at 1 meter (red line - still showing some room acoustic artifacts) and right in front of the woofer (orange line).  Still lacking a home anechoic chamber but both are much flatter than the ones above.

In terms of the missing screw, I do still believe that was a factory boo-boo since the sealing putty that had filled the hole was painted over (just like the screws) and the t-nut underneath worked great fine once I got a new screw.  I can see how it might have been missed as it was the screw that is closest to the top of the case, almost under the overhang where the grill mounts. These have also been in the family since they were new and have not been opened or taken for repair in my memory (40+ years). I checked with my mom and she doesn't remember any service either (her memory goes back somewhat further 😉)

Thanks again to everyone for contributing!

“In terms of the missing screw, I do still believe that was a factory boo-boo since the sealing putty that had filled the hole was painted over (just like the screws) and the t-nut underneath worked great fine once I got a new screw.  I can see how it might have been missed as it was the screw that is closest to the top of the case, almost under the overhang where the grill mounts. These have also been in the family since they were new and have not been opened or taken for repair in my memory (40+ years). I checked with my mom and she doesn't remember any service either (her memory goes back somewhat further.”

Michael, it definitely is possible (as Roy suggests, too) that this screw was missing from production when the speaker was produced.  Most of the screw-ups (NPI) occurred during repair; but no one is perfect, and the factory was under pressure to build a lot of speakers during early 1959 when this speaker was manufactured.

Looking back, the AR-3 prototype was first displayed to the public in the summer of 1958 at the Chicago Hi-Fi Show.  In October of that year, the AR-3 was officially introduced in its “production” form at the New York High Fidelity Music Show.  To say it was the “hit” of the show is an understatement; by November, Acoustic Research had received 500 firm orders for the brand-new speaker system!

Because SN C 0997—definitely finished in lacquered walnut—was manufactured in the early part of 1959, mistakes would have been more prevalent even with several quality-control inspections along the way.  It was common to fix air leaks with Mortite putty anyway, so a screw was somehow left out and the screw hole filled it in with Mortite.  The big machine screws were overkill anyway, so a single missing screw would hardly affect performance if there were no air leaks.  No big deal, but QC probably missed it or ignored it at the time since AR was rushed to fulfill a high order rate at the time (AR was growing quickly, as employment had grown from around six at the beginning in the summer of 1954 to 50 employees in 1956 when the company moved into the four-story building at 24 Thorndike Street in Cambridge).

Can you show some images of the other AR-3 (#C 0978)?  I didn’t see it anywhere, but I may have missed it. 

Note that AR didn’t add an additional “0” to the serial-number range until 1960.  It is also unusual to have consecutive serial numbers with early AR speakers, as they were never produced in “pairs” until the AR-7.  It’s more happenstance than intentional to find a consecutive pair, so it is not as though AR matched-up speaker pairs.

—Tom

[mvboland]

One more question for the group: What is the (or your) preferred method of re-attaching the front grilles? I presume something sturdy but not so sturdy as Gorilla Glue. I take it there were different materials used over time and these look like perhaps plywood?

 

 

[mvboland]

@tysontom - the two speakers are indeed not consistently represented above so here they are in a more orderly fashion (both now back together):

 

The internal wiring was identical between the two and it looks like I only got one wide-angle shot showing the potentiometers and capacitors:

 

Let me know if there is more worth seeing!

-Michael

[tysontom]

On 2/20/2023 at 4:03 PM, mvboland said:

@tysontom - the two speakers are indeed not consistently represented above so here they are in a more orderly fashion (both now back together):

 

The internal wiring was identical between the two and it looks like I only got one wide-angle shot showing the potentiometers and capacitors:

 

Let me know if there is more worth seeing!

-Michael

Michael, great images!  You do have a rare set of early AR-3s; there are very few this old that are still in this condition.  As for your grill, allow the grill material to go beyond the grill panel itself since the grill is tucked-in under the molding.  This was a complicated way to do this, and AR did later change the method to the later AR-3a style, but frankly, the early AR-3 grill (when properly installed) was a much more elegant-looking grill than the later AR-3a grill with the noticeable gap around the edges of the molding.  The older ARs with the gold thread were very handsome, in my view!

Note that the grill tucks in flush within the grill panel, and it's usually best to use a kitchen knife or putty knife to gently tuck the grill in under the molding.  AR actually applied glue under the molding, but it's not always necessary to do that, but the grill need to be carefully positioned to line up the threads and the panel, and to remove any creases or wrinkles.  Properly done, the grill should lie flat without any creases or bows, and so forth, of course easier said than done.  The "3" stick pin is always in the lower right corner, spaced away from the corners the same distance as the logo badge itself.  I sent this AR-3 to the San Francisco Air Port Museum for their exhibit on high-fidelity sound in 2006.

Another view from an old WTFM radio ad:

  Notice the location of the "3" stick pin in the lower-right corner.

Tom