AR-4x Restoration - Where to start?

[JKent]

On 12/15/2020 at 9:43 AM, BrianG said:

I uncovered the mystery of the missing screws after talking with my father.  One of the speakers was serviced.  It looks like who ever did the work left out two of the screws and did a less than perfect job on the gasket tape.

Wonder if that also explains the missing pot. It may have been bypassed because it didn't work but the hole should have been sealed. No matter. The 4x is a pretty simple (but very good) speaker. Just replace the cap & pot. If you know how to solder, good. If not you can use crimps. Review the AR-3a restoration booklet. The 3a was top of the line, 4x was entry level but they are of the same generation and share similarities.

When you remove the woofer try to save the Kimpac sheet that separates the woofer from the fiberglass. The 3rd pic below shows it. If it's shot no worries. You can replace it with crinolin or (a tip from Roy) a sheet of poly batting https://www.walmart.com/ip/Poly-Fil-Low-Loft-Quilt-Batting-72-x-90-1-Each/878980086?selected=true  You want to keep fiberglass fibers out of the woofer. IF the speaker contains rock wool instead of fiberglass you may want to replace it with fiberglass house insulation https://www.lowes.com/pd/Owens-Corning-R-6-7-5-6-sq-ft-Unfaced-Fiberglass-Roll-Insulation-16-in-W-x-4-ft-L/50370324 Early 4x's had 17oz of fiberglass, later ones had 11 oz. I worked on one, SN FX127823 and it had 19oz of rock wool so I replaced it with fg. It would appear that early AR-4x, say before about serial 290,xxx (mid-to-late 1969), used AR-#4 inductor (0.88 mH) and contained 17 oz fiberglass stuffing. The later AR-4x used AR-#5 inductor (1.2 mH) and 11 oz of fiberglass stuffing.

The 4x were my first speakers in 1970 and my first restoration project 30+ years later. I got a lot of help here from Roy and others. The first pic below shows a labeled crossover from John O'Hanlon. "Zen" is the 20uF cap.The 2nd shot is the finished xo. As I said, it was my 1st so I'd do it differently today but this shows the use of crimp connectors. These days I solder and also keep a variety of wire so I can keep the same color coding but that's not really important. 

 

 

Edited April 5, 2023 by JKent
removed 2 photos

[BrianG]

Roy,

You connected the dots!  The speaker with the missing screws is also missing the pot!  The hole was not sealed, as best as I can tell. 

Your wiring photos will be very helpful especially if I have to add a pot that was missing.  

I ordered the parts you recommend and they should arrive by the weekend.  

Thanks for your tips on the Kimpac and fiberglass.  I may go ahead and order that to have it on hand so I can get the project done in one sitting.

Thank you kindly for your detailed answers to my questions.  I'll post again when I get the woofers off.

Kind regards,

Brian

[Lucky Pierre]

Hi Brian,

I am late to the thread, but one piece of advice I can offer it to not use a drill with a screwdriver bit to remove the woofer screws.  I learned by experience that the drill has too much torque and can easily damage the cabinet flange and T nut.

Good luck!

Peter

[BrianG]

Peter, Thanks!

 

[BrianG]

I hope everyone had a good holiday!

I've opened the speaker with the missing LPad.  This speaker had been repaired, poorly.  The woofer came out easily. 

1. Only two screws where replaced.  I see that the two that were replaced had a socked that they were screwed into.  Q - As two of the sockets are missing, is this something I can replace?
2. The Mortite gasket is a mess. There were some small pieces of wood that stuck the the Mortite gasket.   I'm assuming I just use a putty blade to to gently remove Mortite from the cabinet and the driver.  When I replace the Mortite it will fill in the places where the wood lifted off. 
3. The Kempac looks in poor shape.  I'm going to order the suggested Poly-Fil Low-Loft Quilt Batting.
4. The stuffing is in bits and packed.  I'm going to order new Owens Corning R-6.7 5.6-sq ft Unfaced Fiberglass Roll Insulation as suggested.  Q - Do you recommend replacing the stuffing?  Is there any specific way that this needs to be stuffed?  Or just pack it so the space is will filled, but not jammed in?
5. I've found the missing L-Pad.  The crossover has been rewired in an odd way.  I don't see a capacitor.  This might explain why the LPad has been pushed into the cabinet.  Q - Where can I get a wiring diagram?

Thanks to everyone for your help!

Kind regards,

Brian

[Aadams]

• The Mortite gasket is a mess. There were some small pieces of wood that stuck the the Mortite gasket.   I'm assuming I just use a putty blade to to gently remove Mortite from the cabinet and the driver.  When I replace the Mortite it will fill in the places where the wood lifted off. 
• Yes.  You might want to fill and sand a bit but you will use gasket tape instead of mortite.
• The Kempac looks in poor shape.  I'm going to order the suggested Poly-Fil Low-Loft Quilt Batting.
• The stuffing is in bits and packed.  I'm going to order new Owens Corning R-6.7 5.6-sq ft Unfaced Fiberglass Roll Insulation as suggested.  Q - Do you recommend replacing the stuffing? NO that is the original glass fiber stuffing just pack it in a plastic bag and put it aside to be reused. Is there any specific way that this needs to be stuffed? No just pack in a way to prevent rubbing and rattling of wires  Or just pack it so the space is will filled, but not jammed in?  Yes
• I've found the missing L-Pad.  The crossover has been rewired in an odd way.  I don't see a capacitor.   The capacitor is the yellow box.  This might explain why the LPad has been pushed into the cabinet.  Those are pots not lpads.  You will replace them with Lpads.  Q - Where can I get a wiring diagram?  Open the other cab to see if it is intact.  If it is unmolested that is your wiring diagram.  There are some wiring diagrams posted in the threads that have been previously linked.

[JKent]

Adams covered just about everything. Those sockets the screws are screwed into are T-nuts. A good hardware store will have them or order some from PE when you order the foam gasket tape and 20uF capacitors. I don't remember the size/pitch of the machine screws (ex: #10/32) but if you take one of the screws to a good hardware store they'll tell you.

btw, I agree with Adams that you should just reuse the old fiberglass, no matter how crumbly. My suggestion regarding new fiberglass was only if your speakers contained rock wool instead of fiberglass.

Kent