HamboneF18
Super Member
What I read on CSP was that his are 25 ohm.
AR-2ax Speaker - what kind of wood veneer? Pine?
- Thread starter redpackman
- Start date
What I read on CSP was that his are 25 ohm.
r_brumett61
Well-Known Member
FOR BILLS-GOOD LUCK
Bill S
Thread Killer
16 ohm I believe.
Just placed an order for 4 potentiometers from vintage AR.
https://www.ebay.com/itm/193414315287?hash=item2d08643d17:g:w9gAAMXQO21RzZTf
Bill S
Thread Killer
Might be too late but would get them from Jkent on Classic Speakers Page. Discounts for members here. The ones you got will work too tho as I think he's away till later in the month.
HamboneF18
Super Member
You’re right. I’m wrong!
Guess I’ll have to parallel in a resistor to drop the equivalent resistance. I’ve got bunches, so not a big deal to me. A 60 ohm (50+10) will do it. But I hope I won’t need either pot.
My work schedule is getting slammed for April so I won't be advancing as fast as I would like on any of these projects anyways, so no big deal really.
HamboneF18
Super Member
Same here. Spring lawn/gardening and house stuff (wife) plus work on Exploration Upper Stage (EUS) and finishing Core Stage analyses for NASA. Deadlines approaching fast. Went grocery shopping after work last night so that killed any spare time I had. Maybe an hour available tonight?
HamboneF18
Super Member
For my tweeter issue, I found the problem.
It’s an AR factory defect. The voice coil was mounted very crooked in the motor gap. Also, because it’s crooked, the rubbery sealant got into the voice coil gap. This dome was wedged in and glued in place!
Below, you can see how the right side in the pics (dome bottom) is not down. You can see the voice coil windings raised up in the right side of the pics; left side is flush to the face plate. NO WAY this tweeter can work properly mounted this far out of alignment, and out of the motor gap! And…glued in this way!
So my ears weren’t lying to me.
Left side flush:
Right side raised up:
It’s an AR factory defect. The voice coil was mounted very crooked in the motor gap. Also, because it’s crooked, the rubbery sealant got into the voice coil gap. This dome was wedged in and glued in place!
Below, you can see how the right side in the pics (dome bottom) is not down. You can see the voice coil windings raised up in the right side of the pics; left side is flush to the face plate. NO WAY this tweeter can work properly mounted this far out of alignment, and out of the motor gap! And…glued in this way!
So my ears weren’t lying to me.
Left side flush:
Right side raised up:
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Bill S
Thread Killer
That will do it I suppose. Good luck with the repair. No sense to keep the old suspension blobs on now for allignment. Maybe a 9v battery to center the VC?
HamboneF18
Super Member
So I don’t see where I have a choice. I’m removing and remounting this dome:
Remove the sealant:
Lifting out the dome and voice coil. Lots of cleanup work to do on the voice coil. Also, note damping under dome; it has to be put back in place later:
Remove the sealant:
Lifting out the dome and voice coil. Lots of cleanup work to do on the voice coil. Also, note damping under dome; it has to be put back in place later:
HamboneF18
Super Member
Not 9v, but I think you’re right. A 1.5v battery should work, applied to the brass terminals. Hard part is going to be the cleaning of the old sealant off the windings, without causing damage.
HamboneF18
Super Member
Anatomy of the early 2ax Dome Tweeter:
This dome tweeter has a unique build. The cloth-phenolic dome is light, although heavy by modern soft dome standards. It uses enameled aluminum wire on the voice coil, which is why you don’t see solder on the brass binding posts below the tweeter’s mount; the wires are twisted on the posts.
The suspension assembly is very unique. When in the voice coil gap, the stack of batting inside the dome supplies an upward (outward) spring pre-load to the dome. Of course, it also damps vibration and kills sonic energy inside the dome. The 4 liquid-foam deposits (yellow, applied as a foam liquid during assembly, then allowed to cure) anchor down the dome, against the pressure of the dome’s internal batting. The faceplate has 4 cutouts for anchoring the foam away from the voice coil. Then, a thin, sticky, clear elastomer sealant is applied on top of the foam, and on both the perimeter of the dome, as well as on the perimeter of the face plate. This elastomer sealant is allowed to cure. When all is cured, the dome is suspended by the batting that pushes the dome outward, and held in place by the 4 dollops of yellow foam and the clear elastomer membrane.
Below, the polyester batting that is compressed below the dome. It provides damping and spring force outward:
The four foam cutouts in the faceplate for anchoring the liquid foam:
Below, the four foam suspending anchors to “float” the dome:
Below, with the clear elastomer sealant applied, that forms a dust seal, and a resilient retaining membrane, to allow the dome to achieve pistonic motion when a music signal is applied.
This dome tweeter has a unique build. The cloth-phenolic dome is light, although heavy by modern soft dome standards. It uses enameled aluminum wire on the voice coil, which is why you don’t see solder on the brass binding posts below the tweeter’s mount; the wires are twisted on the posts.
The suspension assembly is very unique. When in the voice coil gap, the stack of batting inside the dome supplies an upward (outward) spring pre-load to the dome. Of course, it also damps vibration and kills sonic energy inside the dome. The 4 liquid-foam deposits (yellow, applied as a foam liquid during assembly, then allowed to cure) anchor down the dome, against the pressure of the dome’s internal batting. The faceplate has 4 cutouts for anchoring the foam away from the voice coil. Then, a thin, sticky, clear elastomer sealant is applied on top of the foam, and on both the perimeter of the dome, as well as on the perimeter of the face plate. This elastomer sealant is allowed to cure. When all is cured, the dome is suspended by the batting that pushes the dome outward, and held in place by the 4 dollops of yellow foam and the clear elastomer membrane.
Below, the polyester batting that is compressed below the dome. It provides damping and spring force outward:
The four foam cutouts in the faceplate for anchoring the liquid foam:
Below, the four foam suspending anchors to “float” the dome:
Below, with the clear elastomer sealant applied, that forms a dust seal, and a resilient retaining membrane, to allow the dome to achieve pistonic motion when a music signal is applied.
HamboneF18
Super Member
I got the gap cleaned and the voice coil cleaned. Pretty obvious that AR allowed the glue to get into the gap and on the voice coil, pretty much glueing the foam at the 4 points and on the coil windings. Very little clearance between the center magnet and inside edge of the coil.
Besides all of that, the stack of polyester batting inside the dome puts a VERY substantial preload on the dome. I put a HEAVY steel washer on the dome, and it isn’t enough to force the dome and voice coil down into the gap!
The batting:
Using the heavy steel washer. I need a bigger weight!
Besides all of that, the stack of polyester batting inside the dome puts a VERY substantial preload on the dome. I put a HEAVY steel washer on the dome, and it isn’t enough to force the dome and voice coil down into the gap!
The batting:
Using the heavy steel washer. I need a bigger weight!
HamboneF18
Super Member
Done with the tweeter rebuild.
I’ve been playing the speaker this evening. Wow what a difference the working tweeter makes! I actually have balance. I can hear plenty of clean, shimmering output from it. No more squawking and blaring midrange. I have the tweeter at 80% on the pot, mid at 65%. Nice detail and depth to the sound (even though it’s a mono signal) now that the tweeter provides good fill.
Steel washer for clamp.
I’ve been playing the speaker this evening. Wow what a difference the working tweeter makes! I actually have balance. I can hear plenty of clean, shimmering output from it. No more squawking and blaring midrange. I have the tweeter at 80% on the pot, mid at 65%. Nice detail and depth to the sound (even though it’s a mono signal) now that the tweeter provides good fill.
Steel washer for clamp.
HamboneF18
Super Member
The only RTV silicone I used was black. That’s to secure the lead wires. (On top of the original black tape on the plywood baffle) I used clear butyl rubber on the dome. I mixed clear butyl with red “dope” to make the butyl more “spungy”. It also has micro encapsulated silicone grease, so the red “goop” is a very good damper compound. (I used my ultrasonic tank to mix the silicone grease into the butyl rubber)
HamboneF18
Super Member
Sound test of the rebuilt tweeter:
redpackman
Active Member
Well, an interesting discussion of what pine AR2ax's look like when stripped. WAY, way back on the first couple pages before we got into a discussion of every other component in the AR2ax, you'll see pictures of the the ones I have before cleaning them up and sanding them. Here's what they look like now.
I have cleaned the pots (by disassembling them and polishing them with a brass brush Dremel attachment). I've also replaced all the caps with poly caps. They sound great.
I have cleaned the pots (by disassembling them and polishing them with a brass brush Dremel attachment). I've also replaced all the caps with poly caps. They sound great.
Attachments
HamboneF18
Super Member
Look great!!