AR 4x Odd Couple

[DavidDru]

So I have a pair of 4x's. One is the plywood cabinet (PX 35807) and the other the usual Walnut Oiled (fx256120) The plywood one was stained a pretty dark cherry or similar along with a very shiny lacquer. It is starting to come off so it will need to be sanded down and I will face the same dilemma as some of you have had with the unfinished pine plywood cabs. The other is in very nice condition as you can see with the white linen grille. both need pot work but I am still able to find spots that work.

I was just listening to Blue Note Grant Green, Idle Moments. Impressive. I see what you guys have been saying about these smaller AR's.

The 3rd photo I put the KLH Model 32 on the right and my model 5 on the left for reference/comparison.

[DavidDru]

Oh yeah, right now they are getting some New Class A Power from a very stout Technics Stereo/Mono DC Amplifier SE-A7 (60w). if you ever happen upon one, grab it. I found this one on the shelf at the thrift store - $14. The thing is about 2" high but feels like a lead plate.

[ra.ra]

Hi David,

It seems that you find more vintage AR's in the far reaches of the upper Rockies than we do here in the shadow of the original factory, and this "pair" does seem a bit like the Oscar and Felix of loudspeakers (i.e., The Odd Couple). Nonetheless, having followed a number of your threads and posts, I am sure these will be an enjoyable project for you.

A few observations and questions come to mind right away. First, your two speakers obviously have different cabinets; they also most likely have different drivers; and I would hazard a guess that they probably have different crossovers as well. And about those serial numbers - - the AR-4 had an "F" prefix while the AR-4x had an "FX" prefix, but I have never seen a "PX" prefix.

I am guessing that your walnut FX speaker in pic 2 is the 'run-of-the-mill' yet excellent AR-4x version that was the groundbreaking best-selling small bookshelf speaker of the 1960's. Still, it will be interesting to see the drivers and crossover to confirm or refute this assumption. But it is the speaker in pic 1 that will be of interest to dissect - - - it is the outlier and oddball of your find. That woofer was used in the AR-4 (coil only), but was also found in early AR-4x (coil and cap), so it will be interesting to see the innards of that cabinet. The tweeter, however, is the most curious component, since it more closely resembles the tweeter of the AR-4 rather than the tweeter of the AR-4x. If your tweeter on the PX speaker (with wire mesh grille) were to have a full cover of felt damping, it would be identical to the typical AR-4 tweet (or AR-2ax mid). But it appears slightly different due to that hole in the center of the damping.

When you are able to get around to it, please post a new batch of pics and discoveries, particularly about the PX speaker. I'd be real curious to see: the paper label; the crossover circuit; and maybe even the backside of the tweeter. Very interesting find, and am looking forward to your follow-up.

[DavidDru]

RaRA, you are correct and I could have posted a photo of the other with the grille off, Yes, it is the later version with no cloth surround or caged tweeter etc. I have a few other photos on my other computer so I will add those tomorrow.

on the other plywood one I looked a little closer and it is indeed also FX. The ink had probably smeared a bit and made it look like a P.

I will for sure post some photos of what I find inside.

[owlsplace]

So I have a pair of 4x's. One is the plywood cabinet (PX 35807) and the other the usual Walnut Oiled (fx256120) The plywood one was stained a pretty dark cherry or similar along with a very shiny lacquer. It is starting to come off so it will need to be sanded down and I will face the same dilemma as some of you have had with the unfinished pine plywood cabs. The other is in very nice condition as you can see with the white linen grille. both need pot work but I am still able to find spots that work.

I was just listening to Blue Note Grant Green, Idle Moments. Impressive. I see what you guys have been saying about these smaller AR's.

The 3rd photo I put the KLH Model 32 on the right and my model 5 on the left for reference/comparison.

Put this one up on the auction site "as is." It will probably sell for enough cash to buy a matching set of 4x's from what I've seen lately. The ply cabs won't stand a lot of sanding before you go through the top ply which is thin like a veneer only softer wood..

Just a thought on the auction site ... it will be a pain trying to match that cab up with another orphan unless you use an opaque finish ... not sure what it is about those old CTS cloth surround woofers but they seem to sell quite well.

Roger

[owlsplace]

Just a note since I saw this one on the auction site: these old AR-4x series paper woofer cones are quite fragile. This one could be patched but...

[ra.ra]

Hey David,

OK, so the PX serial number does not exist, so that eliminates one mystery, but when you can, please post some further detail about the speaker in your first pic - - - particularly the crossover, but maybe also the label and the tweeter backside. Thx.

[DavidDru]

Hey David,

OK, so the PX serial number does not exist, so that eliminates one mystery, but when you can, please post some further detail about the speaker in your first pic - - - particularly the crossover, but maybe also the label and the tweeter backside. Thx.

You bet. Right now I have my 3's and 2ax's opened up so I am a bit reluctant to open another. Probably get all the pieces mixed up and have 6 frankenspeakers when done to show you instead of what they should be!

[ra.ra]

Totally understand - - when in dis-assembly mode, you can never take too many notes or pics just to remember your starting point and then be sure it all goes back together correctly, and particularly when there are multiple projects happening simultaneously.

Take care of those big boys and get back to junior when you can - - will look forward to a new post from you on this curious speaker when it's more convenient.

[DavidDru]

My hope is to get the 3's back together this long weekend unless family fun takes it's place. I was planning on opening up the 2ax's to see if I should use those pots on the 3's instead of LPads I have ready to go.

[owlsplace]

So I have a pair of 4x's. One is the plywood cabinet (PX 35807) and the other the usual Walnut Oiled (fx256120) The plywood one was stained a pretty dark cherry or similar along with a very shiny lacquer. It is starting to come off so it will need to be sanded down and I will face the same dilemma as some of you have had with the unfinished pine plywood cabs. The other is in very nice condition as you can see with the white linen grille. both need pot work but I am still able to find spots that work.

I was just listening to Blue Note Grant Green, Idle Moments. Impressive. I see what you guys have been saying about these smaller AR's.

The 3rd photo I put the KLH Model 32 on the right and my model 5 on the left for reference/comparison.

...

Ok David, this one will be fun to watch on the auction site since they are the same serial range as the one you posted Auction #171805336504

The woofer on the right has a punctured cone and surround. Carl has previously noted problems with surrounds on these old CTS woofers which I can verify.

Current bid is $80 with six days to go. I wouldn't be surprised if they sold for over $200 if the seller was willing to ship. These are local pick-up only in the Palm Springs area.

Roger

[DavidDru]

I've added it to my watch list.

Quick impression using my pair is that the older version sounds better. Too many variable to put much stock in that but interesting none the less. I have kept them hooked up in my office system for a week or so now. Great application.

[DavidDru]

I went ahead and opened up the older one:

[owlsplace]

May as well ditch that nasty stuffing. I believe it is rock wool. Plenty of room for an HK pot w/Lasco

Roger

[ra.ra]

Thanks for that post, David - it's all very interesting. Most definitely a 4x speaker, yet a bit of an oddball, as I suspected. The first thing that is slightly uncommon is that crossover, but now I am even more curious about that tweeter.

I have a similar pair of 4x's with s/n FX 38XXX - - plywood cabinets, identical woofer (1404-137-532-5808096) and what I suspect is an identical crossover. Your 4x crossover has two caps, as evidenced by the three wires, and the metal strap holding down the wax block is actually part of the circuit. I am guessing you will not find printed markings on that cap block, and Roy was very helpful to me in determining the cap values - - I then sketched up this schematic, which is probably applicable to your speaker.

About that tweeter - - is it a version of the AR-4 tweet or the AR-4x tweeter? They both fit the same baffle board cut-out dimensions, but the metal cage and the felt damping visually hints at the earlier AR-4 tweeter. Hmmm, what's going on? Perhaps one more pic of the tweeter backside will clear this up - - it should have numeric info as well as a view of the magnet.

Roger and many others automatically ditch the rockwool, but I've got no particular problem re-using the original stuffing. Some have claimed that it contributes to pot corrosion, but I've seen no real evidence to support that notion. We all know that the pots themselves are the weak link in this series of speakers rather than the material composition of the stuffing. Corroded pots occur with fiberglass fill as well.

That is a fairly uncommon AR speaker you have. Despite having a mismatched "pair" and based on your level of interest in vintage AR's, it should be considered a "keeper", or at least as significant trade bait.

[DavidDru]

Thanks for the great response RaRa! The schematic too.

I find the wrap around the cap wax block interesting. There wasn't one on my AR3 cap block of course. Also, no date stamp on the inside cabinet wall.

I will go ahead and remove the tweeter to get a better shot of it.

Yeah, I have no problem re-using the wool. It insures proper quantity goes back in.

Shall see what condition the damn pot is in. This makes 10 pots I have that are crap.

You guys think there anything wrong with stripping and sanding down the cabinet to unfinished wood? (other than be careful)

Also, anybody know if there is a way to check the cap to see how the values are currently without taking it out of circuit?

[ra.ra]

Here is an interesting thread about the very same speaker, and as you can see, there is confusion about the tweeter-cap relationship. Your speakers definitely do not have the small, simple 6uF cap from the AR-4.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4152

And here is my earlier thread, with help from Kent and Roy and Vern and others, about my similar speakers, which by the way, have been stripped of heavy paint down to raw pine cabinets.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7798

About the stuffing, some people really do hate the original rockwool, but I find that it is not all that different from old fiberglass with regards to handling and such. Of course, new fiberglass or fiberfill will work as well in appropriate quantities, but for me, "if it ain't broke, don't fix it".

Pic of the dis-assembled original 4x crossover is attached.

[DavidDru]

So, did AR manufacture this early early version with the various finish options like all the others? Therefore the fact that it is the unfinished pine makes it even more rare. I will want to keep this one as close to original as possible in the restoration and maybe find a match along the way at some point.

[ra.ra]

Attached is the earliest AR-4x brochure I have seen (from 1965), which lists only oiled walnut and unfinished pine. Even AR made special mention that the pine cabs were "not recommended for staining", which is exactly what myself and others have been trying to advocate to owners with bare pine cabinets (see pic attached for reasons why). As difficult as it was for me to strip heavy, thick white paint from my pair, a dark stain finish may be even more stubborn to resurrect to an acceptable level due to the stain's penetrating nature.

In the 1971 catalog, a third option is listed for unfinished birch, but I have never seen a pair in birch.

[DavidDru]

Here is the tweeter. Dated May 4th, 1966 on the faded stamp and also T-66 on the marking.

[ra.ra]

Thanks, and again I find this interesting. Looks like you had to conduct some deep-dig excavation to pry out that old tweeter.

Based on the magnet, it appears to me that you have the regular 2-1/2" cone tweeter found in the 4x, yet for whatever reason, some limited number of these tweeters were outfitted with the addition of the metal grille and donut-shaped damping ring, which then makes it appear (in its front view) very much like the 3-1/2" cone tweet from the earlier AR-4. I can only guess that this small tweak represents some experimentation with on and off-axis dispersion performance, as the best installation of this 'new' tweeter was possibly still being determined.

The first pic below shows a comparison view of two of my AR-4 (left) and typical AR-4x (right) tweeters, from front and rear. The larger magnet on the 4 tweeter has a diameter of 2-3/16" (silver face) and 2-5/16" (black magnet). The 4x tweeter measures 1-7/8" (face) and 2-1/8" (magnet). The second pic (not mine) appears to be identical to your tweeter.

Not unlike yours, my pair of 4x's with the two-cap crossover have tweeters dated from Feb of '66 (and measure at between 4.4 and 4.6 ohms DCR). When you do dig a little further, you might even discover one of those amusing ink stamps on the cabinet interior surface!

Nice little speaker you have - - keep us updated.

[owlsplace]

....

Also, anybody know if there is a way to check the cap to see how the values are currently without taking it out of circuit?

I think you need to isolate the common to get a reading on the caps. If you rebuild this you may as well just attach the 24mfd directly to the woofer terminals.

You will have fun stripping that (aka: glutton for punishment). I wouldn't sand it very much.

Roger

[DavidDru]

Yeah, I will go with stripping chemicals first. The gloss of lacquer on these is thick.