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Cloth surround discoloration?


stupidhead

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Hi folks, I am wondering what is the appearance of the cloth surrounds on the AR early models supposed to be? I have refurbished a set of AR 4x and noted that the surrounds had a hue of a rust color to them. The cones were fine and appearance seemed fine, just the surrounds. I efforted gentle cleaning before doping with Roy's magic mixture, but the appearance is still sort of rusty looking. I am now in the process of starting (finally) a set of 2ax with cloth surrounds and the same appearance to these!? Is this a normal color or is this a discoloration? If discoloration, is it a problem? I know the idea is to have the least amount of mass on the surrounds and if this is some sort of rusting/aging, possibly it is adding mass and should be eliminated? I am also not fond of the look as a side note. I can provide pics if needed, but I suspect my description of this will suffice.

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Several of my 4x woofer surrounds have huge differences in color - - - from almost a golden tone to pure black - - - and they all look just fine and perform very well. I could provide images later if need be, but meanwhile it will be difficult for anyone to comment on your specific situation without seeing your woofers, so I'd suggest uploading a few pics.

Also, evidenced from my small assortment, these woofers may have different types of cones, magnets and/or baskets.

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Hi folks, I am wondering what is the appearance of the cloth surrounds on the AR early models supposed to be? I have refurbished a set of AR 4x and noted that the surrounds had a hue of a rust color to them. The cones were fine and appearance seemed fine, just the surrounds. I efforted gentle cleaning before doping with Roy's magic mixture, but the appearance is still sort of rusty looking. I am now in the process of starting (finally) a set of 2ax with cloth surrounds and the same appearance to these!? Is this a normal color or is this a discoloration? If discoloration, is it a problem? I know the idea is to have the least amount of mass on the surrounds and if this is some sort of rusting/aging, possibly it is adding mass and should be eliminated? I am also not fond of the look as a side note. I can provide pics if needed, but I suspect my description of this will suffice.

Several of my 4x woofer surrounds have huge differences in color - - - from almost a golden tone to pure black - - - and they all look just fine and perform very well. I could provide images later if need be, but meanwhile it will be difficult for anyone to comment on your specific situation without seeing your woofers, so I'd suggest uploading a few pics.

Also, evidenced from my small assortment, these woofers may have different types of cones, magnets and/or baskets.

Ra.ra and stupidhead:

Before you dope the cloth surrounds on the AR-4x and AR-2 (or the AR-12-inch Alnico woofers), check to be sure that the surrounds are actually leaking. In many cases, after all these years, the surrounds continue to do a fine job of sealing the woofers and should not be altered.

With the woofers still in the cabinet, gently press down about ½" on the center of the cone (around the dust cap) and quickly release, and watch the cone as it returns to the center position. If it moves back quickly, check for air leaks in the cabinet; once that has been determined, if the cone returns quickly (as though in free air), the surround needs treatment. If it moves slowly—as if in a viscous fluid—then the surround is probably fine and definitely should not be treated. Remember, too, that the cabinet makes an acoustic seal, not a hermetic air-tight seal. An "acoustic" seal means that the cone travel will be restored to a frequency approximately one-half octave lower than the resonance frequency (fc) or the lowest frequency being reproduced. Being completely air tight would mean that the woofer cone would then move in and out with a change in barometric pressure, not a desirable thing. Adding the dope to the surrounds can sometime raise the free-air resonance or affect the damping and thus degrade the low-frequency performance somewhat, especially if too much is applied.

As for color, the original cloth surrounds were made from an orange-tinted cloth material, and with the butyl-latex (originals were not water-based) clear material applied, the surround looks orange or yellowish orange in appearance, which is 100% normal. Later, AR (and others) added lamp-black dye to the material to make the surrounds black and thus not be noticeable through the grill cloth. No real difference in performance, except that the early orange-colored surrounds seem to remain somewhat better sealed over time. Perhaps the lamp black causes the material to harden sooner.

—Tom Tyson

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+1 on eveything Tom said...

It should be noted that many 4x's will never provide a "slower" woofer return due to deliberate air leakage through the screen cloth dust cap (providing "aperiodic" loading). It makes little sense to apply much of anything on those surrounds. In fact, 4x surrounds seldom appear to be completely sealed. Later 4x's have screen covers over the alnico magnet of the woofer (earlier versions have masking tape), allowing cabinet air to escape past the magnet and voice coil, and through the dust cap.

stupidhead...The sealant is available as clear/amber or tinted black.

Roy

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Thx, Tom and Roy - - as always, interesting history and great advice.

For illustrative purposes, shown here are one woofer each from four different pairs of 4-series speakers. The OP is clearly asking about the 4x model, but since he mentioned "early models", I am showing woofers from both AR-4 and AR-4x speakers - - - two of each, in fact, just to show some of the variations of the early 8" woofers, as well as the transition from the model 4 to the 4x. Three of the four woofers shown here have the non-circular basket perimeter, and they all share the yellow-orange cloth surround color that Tom mentioned.

First pic shows an AR-4 (left) and AR-4x (right).

AR-4: amber color surround, no cross hatch on cone, screen dust cap (s/n F00105, F00242)

AR-4x: light color surround, grey cone, screen dust cap (s/n FX316924, FX 320139)

Second pic shows an AR-4x (left) and AR-4 (right).

AR-4x: very light color surround, cross-hatch on cone, screen dust cap (s/n FX38643, FX38644)

AR-4: amber color surround, cross-hatch on cone, non-screen dust cap (s/n F07162, F07241)

(note: the 4x woof shown in pic 2 is from the oddball version with two capacitors)

All of these woofers have a very light thinned coating of Roy's butyl sealant - - I have now treated at least eight small cloth surrounds and barely made a dent in the bottle of potion. Probably due to the intentional passage of air with these porous dust caps (and magnet enclosures), each of these woofers failed to offer conclusive results from the push-release-return evaluation.

post-112624-0-57729100-1411783538_thumb. post-112624-0-09531500-1411783716_thumb.

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Hi folks and thanx for the responses. Initially I didn't upload any pics figuring it was relatively common and relatively benign. After going through my pics I have found this one to probably be the best example of what I am referring to.

post-170704-0-85151900-1411810047.jpg

This pic is actually a 2ax woofer (serial 01035) and looks entirely different than the pic(s) that ra.ra has graciously posted. Maybe I am once again being too literal, but I am intrigued by Tom's description of the original cloth having an orange tint. The above pic certainly suggests orange, but to my eye it seems splotchy color variation in the cloth, and nothing at all like ra.ra's creamish colored woofers. In person the variation in color is even more obvious, and maybe I should take some more pics that focus on this question. I hope to do a little testing this weekend as Tom has suggested (thanx for the step by step) to determine if any action is needed. I am also recalling the 4x refurb in which I saw some actual rust around the tweeter exterior frame. See this next pic..

post-170704-0-81254600-1411812369.jpg

which by the way is a terrible pic, and as woofer above, just a random photo I took along the way which was not focused on what we are talking about but still sort of captures it. The real rusty look around the tweeter is evident, the woofer screws show evidence as well and there is a little evidence of a rust color on the actual woofer and surround.

The last thing I want to do is any damage to these as I go along, and the guidance that I have gotten from this, and other forums like it, has been greatly appreciated! A sincere thanx to all involved.

post-170704-0-85151900-1411810047_thumb.

post-170704-0-81254600-1411812369_thumb.

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By all appearances, both of your woofers look just fine. Your 4x woofer appears mostly black-ish, and actually it is very much like the 4x woofer with the grey cone (first pic, right side) that I attached in post 5 - - I suspect that the only difference between these two woofers is that your woofer dope contained lamp black whereas mine did not - - both woofers show obvious evidence of the original dope extending half way down the paper cone.

And, as you tried to describe in post #1, your 2ax cloth woofer surround does indeed appear to have a rust tone. This is normal, too, and falls somewhere between the colors of the two similar 10" woofers shown here. If your diagnosis does result in a decision to apply fresh butyl sealant, you will likely find that the wet application actually revives the remaining original butyl, which might result in a coloration with more black than one would expect.

At least this happened to me once while re-sealing a pair of 4x woofers. The darkening appearance was not drastic, but I thought "Whoa....where did that black come from?" Perhaps there was lamp black micro-particulate lurking on the underside of the surround roll - - I dunno. Since then, I like to "pre-dope" the cloth surrounds with a very light application of solvent only, which merely smooths and blends any original sealant which is still present, then allowing them to fully dry out before applying the fresh butyl.

post-112624-0-48518900-1412178494_thumb.

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