Help identifying AR 4x woofers

[DMRanney]

Hi all - newbie here!

A friend sold me a pair of AR 4x speakers for $50 each as a refurbishment/learning project. They work but don't sound all that great right now. I pulled the grilles off and right off the bat I'm puzzled by what I see. The two woofers are obviously very different. The right one looks pretty original and crusty, with the cloth ring, and is mounted slightly recessed from the panel. The left one looks almost new, with the foam ring, and is mounted out of plane with the panel: from flush on one side to about 1/8th proud on the other side.

My friend says he purchased them new as a pair while on leave from the Air Force in Tokyo in the early seventies. He has no memory of ever having one of the woofers replaced, although it's possible he's mistaken. The older-looking one is serial # 364181, and the newer-looking one is serial #FX329797. Is there any way his recollection of purchasing them new as a pair back then holds up? Is it plausible that both woofers are the originals?

Other differences between the two speakers are: The right one has slightly lighter toned walnut veneer, very slightly lighter colored and heavier-feeling grille cloth, and a crudely crafted pressboard grille frame as opposed to neatly crafted black-stained wood. 

At a casual first listen, both woofers sound fine - it's the midrange that sounds really muddy and the pots seem completely nonfunctional. I'm just wondering if I should just shrug off the woofer puzzlement or worry about having the woofers match?

[JKent]

13 hours ago, DMRanney said:

They work but don't sound all that great right now. I pulled the grilles off and right off the bat I'm puzzled by what I see. The two woofers are obviously very different. The right one looks pretty original and crusty, with the cloth ring, and is mounted slightly recessed from the panel. The left one looks almost new, with the foam ring, and is mounted out of plane with the panel: from flush on one side to about 1/8th proud on the other side.

Welcome to CSP DM

Very nice. The 4x's are very good sounding speakers, so something is amiss. I suspect the 20uF wax capacitors have drifted and the pots are shot. 

As for the woofers, Im pretty sure there were a few woofer styles in the 4 series but they all had cloth surrounds (and none had that external gasket). I suggest you pull the woofer. You'll have to do that to replace the cap and pot anyway. See if you can identify it or post a picture of the back with any markings here. 

There's probably some of the original dried putty sealant around the perimeter of the woofer cut-out and that's what's making it angle out a bit. It's also possible that woofer does not have a good seal, adding to the sound issue.

If it's a woofer from a later AR speaker it may be OK to keep it. In any case I'd do the electronic work first and then audition them.

The slight difference in color is easily corrected. If the veneer is otherwise good, I'd clean both with mineral spirits then use clear Watco Oil on the dark one and walnut Watco Oil on the light one. But I see you're a woodworker so you probably know what to do (and if you have a better method please share it).

Kent

Edited December 17, 2022 by JKent

[DMRanney]

Thanks so much for the feedback. I'll pull the woofers and see if there's some identification on the newer one.

 

Any thoughts on that funky pressboard frame for the grille cloth? It sure looks homemade to me.

 

-Doug

[RoyC]

51 minutes ago, DMRanney said:

Thanks so much for the feedback. I'll pull the woofers and see if there's some identification on the newer one.

 

Any thoughts on that funky pressboard frame for the grille cloth? It sure looks homemade to me.

 

-Doug

The "pressboard" frame is an original AR frame.

The woofer with the foam surround appears to be a later (early 80's) AR woofer. It is not original to the 4x.

Roy

[DMRanney]

I pulled the woofers and the newer one is clearly a replacement, marked "service replacement unit." It looks like a very sloppy job: the dried up sealant was not renewed, making the speaker sit cockeyed in the opening. When I pulled out the insulation there were several chunks of dried sealant sprinkled in. The inductor coil is laying loose - not mounted on it's post over the capacitor! And to top it off, the pot seems to be wired wrong, which probably explains why the tweeter doesn't work at all.

 

[DMRanney]

The other cabinet had the original cloth ringed speaker (marked 4X 2748H). Strangely, though it had no sealant at all but rather this white styrofoam-ish gasket. Same for the tweeter. Can this possibly be original? Or has this one been messed with as well?

 

 

[RoyC]

1 hour ago, DMRanney said:

The other cabinet had the original cloth ringed speaker (marked 4X 2748H). Strangely, though it had no sealant at all but rather this white styrofoam-ish gasket. Same for the tweeter. Can this possibly be original? Or has this one been messed with as well?

 

 

The white foam gasket, and everything in the cabinet, are original. Someone most likely used putty when the replacement woofer was installed in the other cabinet. The serial numbers of both cabinets are rather late in the 4x game, and foam gaskets would have been used in both cabinets by that time. It is not uncommon for those gaskets to tear, requiring replacement when removed. Putty was originally used in earlier days, and frequently used by people replacing drivers in later days.

Roy

[DMRanney]

Kent and Roy, thank you so much for your patience with my ignorance. 

I took apart one of the pots and to my eye it seems pretty good. Would a delicate polishing of the contact surfaces be sufficient (and safe) in your opinion?

And is it best practice to simply replace the capacitor as preventative maintenance?

Thanks,

Doug

[JKent]

Those pots do look good so you may want to clean them up. Definitely replace the caps. The can cap may be ok but the wax one is probably toast. AR4x speakers sound great when functioning properly. Clean the pots, replace the caps and mount the woofers with proper gasket tape and check the sound again. I’d also check the tweeters while the woofers are disconnected. 

[RoyC]

22 hours ago, DMRanney said:

Kent and Roy, thank you so much for your patience with my ignorance. 

I took apart one of the pots and to my eye it seems pretty good. Would a delicate polishing of the contact surfaces be sufficient (and safe) in your opinion?

And is it best practice to simply replace the capacitor as preventative maintenance?

Thanks,

Doug

The pots are in nice shape, but will require a bit more than delicate polishing. There is both tarnish and some corrosion present, which should be completely removed. Do not, however, use an abrasive on the resistor coil.

The capacitor could be an Industrial Condenser brand cap, which should be replaced. Just because it is a large "can" type of cap doesn't mean it is the superior Sprague brand. If in doubt, replacing a single cap is relatively easy to do and will provide peace of mind.

If you decide to replace the caps send me a PM. I just acquired a rather large number of them from a (recently closed) shop for which I used to do repair work.

Roy

[DMRanney]

I already ordered two Dayton Audio PMPC-20 20uF 250V Precision Audio Capacitors from Parts-express.com. Sorry I didn't see your reply sooner! The can-type capacitor that's in there now is a Sprague, actually.

 

Thanks,

Doug

[RoyC]

21 hours ago, DMRanney said:

I already ordered two Dayton Audio PMPC-20 20uF 250V Precision Audio Capacitors from Parts-express.com. Sorry I didn't see your reply sooner! The can-type capacitor that's in there now is a Sprague, actually.

 

Thanks,

Doug

All good! Best of luck with your project.

Roy