AR-3 cabinet construction

[Andy]

Wanted to know what year or at what serial number did ar change from a plywood cabinet to a mfd cabinet (I know the utility version remained a plywood type after the veneered versions had stopped using plywood). I've also noticed that the back panel remained wood after mfd had started to be used in the rest of the cabinet. Finally the back was mfd as well, but at what year hese changes accured I would like to know?

[RoyC]

It was probably a gradual thing based on availability of materials. I have a pair of 1972 era AR-3a's #67069 with a plywood back panel and #67071 with a particle board back panel.

Roy

[tysontom]

>Wanted to know what year or at what serial number did ar

>change from a plywood cabinet to a mfd cabinet (I know the

>utility version remained a plywood type after the veneered

>versions had stopped using plywood). I've also noticed that

>the back panel remained wood after mfd had started to be used

>in the rest of the cabinet. Finally the back was mfd as well,

>but at what year hese changes accured I would like to know?

To my knowledge only a few of the very early finished-wood AR-3s had actual veneer-covered plywood cabinets. I think nearly every one probably after 1960 or so was NovaPly, a high-quality medium-density core. The veneer adhered to engineered wood better than plywood. The non-plywood cabinets were actually acoustically better than plywood. There is a mystique about plywood cabinets, and some companies (KLH for one) used 15-ply marine plywood in their cabinets, but in the end the mdf cabinets were better and less resonant.

--Tom Tyson

[RoyC]

The attached photos are of the (2) 1972 cabinets I mentioned above which are separated by a couple of serial #'s. Both are mdf but the back of one is clearly plywood. I've noticed that the internal bracing varies between plywood and mdf as well.

Roy

[Guest Bret]

That's interesting that those cabinets are close together in serial number. They had to change at some number, I realize.

Did AR always build their own cabinets in-house, or did they ever "outsource" the cabinets' construction?

Bret

[tysontom]

>The attached photos are of the (2) 1972 cabinets I mentioned

>above which are separated by a couple of serial #'s. Both are

>mdf but the back of one is clearly plywood. I've noticed that

>the internal bracing varies between plywood and mdf as well.

>

>Roy

Roy,

I think the explanation for this is that incoming cabinets were stored in a specific cabinet-storage area, and when a production run of AR-3as came along, production-line workers probably got the necessary raw materials from this storage area, whatever might be there at that time. The vendor might have had a mixture of mdf and plywood backs and fronts until the supply ran out and all cabinet fronts and backs were mdf. The side-wall box construction, however, went away from plywood as far back as 1957 or 1958. I have seen the earliest AR-1s and AR-2s with veneer-covered plywood, but by the time the AR-3 came around in 1959, the veneered cabinets were all NovaPly (except for the utility Pine, of course).

--Tom Tyson

[RoyC]

Thanks Tom..that makes sense.

I just took a look and found that the front panels are plywood as well on both of these cabinets.

There must have been a number of leftover plywood backs and fronts hanging around for awhile as its not unusual to see them in Ebay pics.

The '74 and '75 cabinets I have are completely mdf.

Roy

[tysontom]

>Thanks Tom..that makes sense.

>

>I just took a look and found that the front panels are plywood

>as well on both of these cabinets.

>There must have been a number of leftover plywood backs and

>fronts hanging around for awhile as its not unusual to see

>them in Ebay pics.

>

>The '74 and '75 cabinets I have are completely mdf.

>

>Roy

Roy,

Do your '74 and '75 cabinets have glue-on grills or Velcro? Is the label in the back the blue-ink small version without the warranty card? Are either or both of these speaker back-wired? These changes may have come in 1976, but I'm thinking they came along about this time as well as the change to electrolytic capacitors.

--Tom Tyson

[RoyC]

Tom,

The 74's are back wired with velcro grill attachment. The label is the small blue one and the EIA #is 561 7451 for both, I presume indicating they were built in late 1974. Interestingly serial #96621 has the blue 6uF Sprague tweeter cap and #96584 has the old wax block. The rest of the crossovers are the same, both utilizing the Industrial Cond. Corp. "Royalitic" caps for the woofers and mids. The mid caps however are the more modern looking small "Royalitic" 50uF. They are actually smaller than the blue 6uF Sprague tweeter caps.

The "75's" are a puzzle. I call them '75's only because they fit the description of that era or later and I seem to remember a drive with a 1975 or 1976 date stamped on it. Unfortunately it was before the days I was interested in such things. I don't have all the parts to these. They are teak and have the later thin front molding with the larger, velcro attached grill and one large label on the top of the back panel. The serial #'s 15725 and 15724 do not fit the normal sequence. I only remember that the crossovers had no wax block caps and contained the blue Sprague tweeter caps. They are FRONT wired...part of the puzzle. My only clue is that the rear label refers to the placment of the speakers in "metres". Were these mid 70's imports?

Roy

[tysontom]

>Tom,

>

>The 74's are back wired with velcro grill attachment. The

>label is the small blue one and the EIA #is 561 7451 for both,

>I presume indicating they were built in late 1974.

>Interestingly serial #96621 has the blue 6uF Sprague tweeter

>cap and #96584 has the old wax block. The rest of the

>crossovers are the same, both utilizing the Industrial Cond.

>Corp. "Royalitic" caps for the woofers and mids. The mid caps

>however are the more modern looking small "Royalitic" 50uF.

>They are actually smaller than the blue 6uF Sprague tweeter

>caps.

>

Roy,

This AR-3a pair (#96621 & #96584) was probably at or near the beginning of the back-wired series in which the crossover was, I believe, changed. The price also went to $285/ea. from $250 in 1974, I believe (SteveF would probably know for sure), and AR dropped the many lovely optional cabinet finishes in lieu of oiled-walnut finish only. I think this was the beginning of the 525 Hz crossover with electrolytic capacitors, but I'm confident of exactly when this occurred. I do know that the crossover remained at 575 Hz until Roy Allison left AR in 1972, so if it changed it was probably with the new version with back-wired drivers.

*Important question: what is the style and value of the capacitor across the woofer? These two AR-3a's should also have the newer-style AR-11/10Pi woofer, and likely a different weight fiberglass wadding inside. The rogue Chicago Industrial plastic-encapsulated paper capacitor you mention was likely a leftover production part. The linen grill material had changed by this time, as well, and it was whiter in color and thicker in texture than the earlier beige-linen versions. I believe the world supply of that original linen cloth ended at AR somewhere in the early 1970s.

>The "75's" are a puzzle. I call them '75's only because they

>fit the description of that era or later and I seem to

>remember a drive with a 1975 or 1976 date stamped on it.

>Unfortunately it was before the days I was interested in such

>things. I don't have all the parts to these. They are teak and

>have the later thin front molding with the larger, velcro

>attached grill and one large label on the top of the back

>panel. The serial #'s 15725 and 15724 do not fit the normal

>sequence. I only remember that the crossovers had no wax block

>caps and contained the blue Sprague tweeter caps. They are

>FRONT wired...part of the puzzle. My only clue is that the

>rear label refers to the placment of the speakers in "metres".

>Were these mid 70's imports?

>

These were definitely the European versions, very similar to the AR-3a Improved, and they were not imported to the US. The reason for the thin grill molding was a reluctance on the part of the British, especially, to accept the styling of the thick edge molding on the AR-3 and AR-3a, and the pair you have reflects that change to the thinner style (I have a pair of AR-2ax speakers with that same exact molding). AR built drivers in the US and shipped them to Europe, built the speakers in England and Holland. The serial numbers were the European number sequence I think.

--Tom Tyson

[RoyC]

>*Important question: what is the style and value of the

>capacitor across the woofer?

Both have large silver cylinder 150uF 50v Industrial Cond Corp (Chicago) "Royalitic Capacitor Long Life" woofer caps (AR4728). They both have small, modern style, silver 50uF midrange caps (AR4727) with the same markings. I've been inside alot of AR-3a's and have never seen any AR-3a with crossover components of different values other than late 60's versions with the #7 (1.9mh) woofer inductors.

These two AR-3a's should also

>have the newer-style AR-11/10Pi woofer, and likely a different

>weight fiberglass wadding inside.

They actually look more like my 72 versions...with a slightly tighter suspension...but with the painted black basket outer edge (no facing foam) and larger masonite ring to which the foam surround attaches. The label is the "red dot 200003" white sticker by the terminals.

The fiberglass weighed 20 to 21 ounces in both cabinets...the same weight and type as my '71 and '72 cabinets.

The rogue Chicago

>Industrial plastic-encapsulated paper capacitor you mention

>was likely a leftover production part.

It also measures 7.5uF..end of the line for that baby..

*These cabinets contained the first AR-3a crossover wires that I have seen that were not tinned.

The linen grill

>material had changed by this time, as well, and it was whiter

>in color and thicker in texture than the earlier beige-linen

>versions. I believe the world supply of that original linen

>cloth ended at AR somewhere in the early 1970s.

The 74's seem to have a smoother, tighter weave and are just a bit lighter in color...The Europen versions are definitely whiter than the 74's however.

>These were definitely the European versions, very similar to

>the AR-3a Improved, and they were not imported to the US.

Thanks for solving the mystery, Tom!

Roy

[tysontom]

>

>Both have large silver cylinder 150uF 50v Industrial Cond Corp

>(Chicago) "Royalitic Capacitor Long Life" woofer caps

>(AR4728). They both have small, modern style, silver 50uF

>midrange caps (AR4727) with the same markings. I've been

>inside alot of AR-3a's and have never seen any AR-3a with

>crossover components of different values other than late 60's

>versions with the #7 (1.9mh) woofer inductors.

>

Roy, thanks for the quick reply and good information. The plot thickens. All the AR-3a's appear to have the same crossover values, and the designer, Roy Allison, is emphatic about the 575 Hz crossover, I now wonder where the 525 Hz number came into play, and what changes were made to get it? SteveF even has letters from AR stating that those changes were made, but I've yet to see the evidence in the crossover itself. Incidentally, the AR part numbers for the above capacitors: 150 mfd is AR#803008-0; 50 mfd is AR#803007-0. Those numbers above off the capacitors were the manufacturer's specific part number.

>They actually look more like my 72 versions...with a slightly

>tighter suspension...but with the painted black basket outer

>edge (no facing foam) and larger masonite ring to which the

>foam surround attaches. The label is the "red dot 200003"

>white sticker by the terminals.

>The fiberglass weighed 20 to 21 ounces in both cabinets...the

>same weight and type as my '71 and '72 cabinets.

>

Did the woofers (in your '74s) originally have the clear butyl-rubber coating on the surround, or did the surrounds have the later-style surrounds with smooth urethane-foam surrounds? All the AR-3a ceramic woofers from 1969 through at least 1972 or 1973 should have the butyl-rubber coating, and the masonite ring (orange tint in color) that went out beyond the surround edge closer to the edge of the flange; of course, much of the surround detail would be hard to tell today since virtually all of the original surrounds are long-gone. Cone texture on the bottom side of the new-style woofer cone is slightly different, too, I believe.

>

>It also measures 7.5uF..end of the line for that baby..

>*These cabinets contained the first AR-3a crossover wires that

>I have seen that were not tinned.

>

I don't know why AR stopped using tinned wires. They may have changed vendors or wire specification for cost-reduction measures, or decided that tinned wires were not necessary since most connections by this time were crimped-on affairs (except for the level controls).

--Tom Tyson

[RoyC]

Hello again Tom,

>Did the woofers (in your '74s) originally have the clear

>butyl-rubber coating on the surround, or did the surrounds

>have the later-style surrounds with smooth urethane-foam

>surrounds? All the AR-3a ceramic woofers from 1969 through at

>least 1972 or 1973 should have the butyl-rubber coating, and

>the masonite ring (orange tint in color) that went out beyond

>the surround edge closer to the edge of the flange;

I've attached a pic of the woofers before and after (Millersound). The refurbished one is the '74 and the beat up one is an older woofer of an unknown (earlier) vintage. That one has the big red + instead of the 200003 label. They were identical with a large tan color masonite flange ring as opposed to the more orange color I have seen. They both had the butyl-rubber coating as well.

>I don't know why AR stopped using tinned wires. They may have

>changed vendors or wire specification for cost-reduction

>measures, or decided that tinned wires were not necessary

>since most connections by this time were crimped-on affairs

>(except for the level controls).

The '74 wire colors are a lighter shade of the same old colors. Incidentally Home Depot carries 24 foot rolls of 16 ga "Carol" primary wire in various colors including green, yellow, blue and red for those going for the authentic look in restoration projects.

Tom, I know the timing is off and we've discussed it at length before, but could it be possible that ol' #7 coil is where the change really took place? 1.9mh would represent a lower woofer/mid crossover point than the #9 (2.85) coil. I'm willing to stop bugging you on this issue when we have some evidence of other crossover changes :-).

Roy

PS Everyone, if I'm overdoing the attachment bit let me know...

[tysontom]

>

>I've attached a pic of the woofers before and after

>(Millersound). The refurbished one is the '74 and the beat up

>one is an older woofer of an unknown (earlier) vintage. That

>one has the big red + instead of the 200003 label. They were

>identical with a large tan color masonite flange ring as

>opposed to the more orange color I have seen. They both had

>the butyl-rubber coating as well.

>

Roy,

Thanks for those images. I think those two woofers appear to be a similar vintage, although the cone on the right side does seem to be slightly different. Both appear to have the same masonite ring and flat-black-painted flange. The one on the left appears untouched and would have been manufactured in the 1971-1974 time-frame, I believe, as you can tell from the cone material, dust cap and so forth. Both also have the short voice-coil lead-wire eyelets (compared with earlier long wires farther down the cone from the apex). The long wires characterized the first woofers from 1969 through early 1970 or so. Also, look along the magnet edge itself and see if you can find a date stamp. I would also surmise that both these woofers have the same spider, but you would have to inspect them carefully to know for sure. It's sometimes difficult to read and the date can get rubbed off by handling over time, but each woofer was stamped with the build date. The rebuilt woofer (on right side of picture) appears to have the retrofit smaller-diameter (looks like .5 inch) surround foam material and a new dust cap. It also appears to have been shimmed when rebuilt, a process that is completely unnecessary. It's really better *not* to shim the cone on this woofer because shimming can sometimes put the spider in a slight bind if the voice coil was not in perfect alignment when it was manufactured. If you look closely, you can also see that the cone rests slightly below the masonite ring, which was normal. New surrounds can sometimes raise the cone *above* its center "rest" position slightly, so always check for this. This is not a big deal, of course, since the voice coil is one-inch long in a one-half-inch gap, but it is probably better to get a surround that is the full 5/8-inch diameter and that does not appreciably change the height of the resting cone. This company, among others I am sure, has the correct surround kit for the AR 12-inch woofer, despite the fact that they call an 11-inch woofer:

http://www.speakerworks.net/surround_info.html

It seems likely that the compliance of the ceramic woofer did not appreciably change from 1969 through about 1974, at least until the *new* version of the AR-3a was introduced with the Velcro grills and back wiring.

>

>Tom, I know the timing is off and we've discussed it at length

>before, but could it be possible that ol' #7 coil is where the

>change really took place? 1.9mh would represent a lower

>woofer/mid crossover point than the #9 (2.85) coil. I'm

>willing to stop bugging you on this issue when we have some

>evidence of other crossover changes :-).

>

This certainly seems to be the most plausible explanation for any change, and thus a change in the L/C ratio. I guess the question is: where in time did this inductor change occur? I don't have a clue. I have an early print of the AR-3a crossover that shows the 3700-0 woofer (Alnico), but it shows the #9 coil. I do have other AR-3a schematics, but they are buried in a recent move, and I will have to find them.

Your images are great! Incidentally, I have a problem: I have many images I would love to download, but for some reason I cannot get them to fill the attachment box, even though my jpeg images seem to upload (Step 1, Step 2, Step 3). I have no idea why they don't go further than that, and if anyone can help me with this I would greatly appreciate it. Perhaps there is a filter setting somewhere that prevents them from populating the Forum Server.

--Tom Tyson

[RoyC]

Tom,

Uh oh, I think we've turned this into yet another woofer thread:-)

>Thanks for those images. I think those two woofers appear to

>be a similar vintage, although the cone on the right side does

>seem to be slightly different.

The cone "feels" the same. Millersound dyes the cone to look new.

Also, look along the magnet edge itself and see if you

>can find a date stamp. I would also surmise that both these

>woofers have the same spider, but you would have to inspect

>them carefully to know for sure.

The spiders do appear to be identical. I can't find dates on any of my woofers with the exception of (2) Oct. 1972 woofers I recently re-foamed myself (see attached pic). They appear to be the same as the '74's as well but have the big red "+". I think the masonite is darker due to the glue.

As you can see I used the 5/8" surround. I'm not sure why Millersound uses the 1/2" but they sound OK. For some reason Bill used new dustcaps on the '74's but he usually leaves the old dustcaps when just replacing surrounds.

>It seems likely that the compliance of the ceramic woofer did

>not appreciably change from 1969 through about 1974, at least

>until the *new* version of the AR-3a was introduced with the

>Velcro grills and back wiring.

My '74's are back wired and have velcro grill attachment. The EIA # indicates a late 74 build date, so it must have been closer to 75 that the woofers changed.

I wish I could help with your attachment question..haven't had a problem on this end. I can't wait for you to figure it out. I'm sure you have some great stuff to show us!

Roy

[Guest Bret]

>I have no idea why they don't go further than that, and if anyone can help me with this I would greatly appreciate it.<

Are you getting any error messages, Tom?

Bret

[tysontom]

>>I have no idea why they don't go further than that, and if

>anyone can help me with this I would greatly appreciate it.<

>

>Are you getting any error messages, Tom?

>

>Bret

Bret,

Thanks for your interest.

Disregard all the info below. I "brute-forced" the image by actually copying and pasting the URL for the image (are you supposed to do that?) into the attachment box. If that's the drill, I missed it somehow long ago.

It's working, at least for now!

No, I don't get any error messages, and everything appears to go fine, but the images just don't populate the message anywhere. I'm sure I'm doing something wrong, but I rarely have any problems sending or receiving images with e-mail and so forth, so I'm at a loss.

Here's my routine: (1) "Click here to choose your attachments," which I do, and then the attachment window appears on the screen. (2) I then do "Step 1, Click on Browse..." to select a jpg image, of which I have many to share. (3) I define the image file as JPEG. (4) I click on "Upload file!" After all this, the dialog box at the top says that the image was successfully downloaded, but it does not appear on the message screen. Perhaps it is floating around on the Forum server, but it does not populate the message box.

Got any ideas? Anybody?

Thanks,

--Tom

P.S.: I tried it again in this message. This time it again said the file was sucessfully (sic) uploaded to the server. It even gave the file URL:

http://www.classicspeakerpages.net/dc/user_files/375.jpg

I even went out on the internet, pasted-in the above URL, and the image appears. However, why won't it post in the message? Just for the fun of it I posted the attachment URL in the attachment box -- maybe that's what you are supposed to do....

[RoyC]

Hi Tom,

I can't open your attachment. In your step #2, when you choose your jpeg, do you click on "open" before going to step #3? You should if you haven't been.

Meanwhile, great foam surround pics...

Roy

[tysontom]

>Hi Tom,

>I can't open your attachment. In your step #2, when you choose

>your jpeg, do you click on "open" before going to step #3? You

>should if you haven't been.

>

>Meanwhile, great foam surround pics...

>

>Roy

>

>

>

Roy,

Thanks. The embeded image of the foam surrounds, showing the 1/2-inch and 5/8-inch versions, was the same as the attachment. When I choose my image file in the "Browse" Step 1 mode, I then open it from the "Choose fie" menu choice there, and I then select the radio button for JPEG image file, and then I go to step 3 "Upload file!" For example, I loaded another file (see below), and you can paste that URL into your browser and it will bring up the image of the AR-10Pi Live-vs.-Recorded crossover with its heavy-duty transformer and wiring. This file, however, finally did upload into the message box after repeated attempts, even using the "brute-force" method.

http://www.classicspeakerpages.net/dc/user_files/379.jpg

--Tom Tyson