Original AR4x woofers?

[Carlspeak]

I have two woofers that look similar to originals* that had cloth surrounds. However, someone decided to experiment with sealing the cloth and failed miserably (seems like they used shellac!). Each has an alnico magnet rear end. The cones have the four line cross-hatch pattern I know was on some of the AR originals

The p/n's on the back are 1414, 137 610, and 5808096, each printed on a different row. There's no mention of AR.

Could these be ABT replacements? or, one of the many variants AR used in the 4x's. AR historians?

I've cut off the sad, stiff cloth surrounds and installed 8 inch BA filleted foams which brought the Fs down to a nice, respectable 32 hz but still am wondering about the origin of these.

* the similar look is mostly at the rear end. The frame od is not round, but instead has bulges at the bolt holes.

[tysontom]

Carl,

Without seeing any images of your woofer, it would seem to be the stock CTS-built, AR-modified woofer used by AR for the AR-4 and possibly the very early AR-4x. The standard, or original, fs for this woofer is around 27 Hz, so the 32 Hz number you got is "close enough for government work," as they say. There were numberous variations of this woofer, but all had the slug-type Alnico-5 magnet and cloth surrounds. Most are therefore interchangeable.

--Tom Tyson

Attached image: AR-4 woofer.

[Carlspeak]

Yup, that's it. Thanks Tom!

After break in these should drop down to around 30 hz.

BTW, these have purple colored, cup type spiders which are quite soft.

[ironlake]

doesn,t that open weave dust cap allow air to leak out?

[Carlspeak]

doesn,t that open weave dust cap allow air to leak out?

Actually, it allows air to leak in and keep the voice coil cool.

[RoyC]

doesn,t that open weave dust cap allow air to leak out?

Many AR-4x woofers have porous fabric covers (see attached photo) over the sides of the alnico magnet, as well as untreated cloth dustcaps. These woofers do indeed allow some leakage from the cabinet past the voice coil. It is not possible to achieve the typical "slow" woofer return with the push test with these woofers. This issue has driven some folks to gunk up (and compromise) the cloth surrounds in an effort to "seal" the surrounds/cabinets, with no success.

Roy

[Rob dalton]

Since I have a good sounding pair of AR4xs this was an interesting thread. Other than scratchy pots (which can be positioned about right, but obviously have corrosion) my AR4xs sound very good. Mine are S/N 43566 and 43574 and appear to have cloth surrounds. Is there a S/N cutoff that would indicate when cloth was changed to foam? Is Permatex 80062 still considered to be good goop for resealing cloth surround? I've also wondered if the system resonance would tell me if they even need sealed (if resonance is around 30 HZ they are probably good enough). How does one measure system (speaker in box) resonance. Would i expect to see a pronounced change in impedance or drive current? Thanks..

[ra.ra]

To supplement Tom's woofer pic, I'd like to add this side-by-side comparison of AR-4 (left) and AR-4x (right) drivers. My pair of 4's is very early (s/n's 00105 and 00242) and the woofs do not have the criss-cross hatching or swoopy floral pattern.

To Carl, my AR-4 woofers have factory notations nearly identical to yours (137-430 and 5808096, but the third number is 187 or 306).

To Rob, once you settle on an appropriate product for the re-doping of cloth surrounds, be sure to use a thin solution and a light appliaction. I used the liquid butyl which I have heard is (or will be) available from vintage AR.

[RoyC]

I used the liquid butyl which I have heard is (or will be) available from vintage AR.

Any Classic Speaker Pages member can contact me directly for the sealant. Ebay's Larry Lagace/Vintage AR can also provide it on request if It isn't listed in his Ebay store.

Roy

[Carlspeak]

Carl, Without seeing any images of your woofer, it would seem to be the stock CTS-built, AR-modified woofer used by AR for the AR-4 and possibly the very early AR-4x. The standard, or original, fs for this woofer is around 27 Hz, so the 32 Hz number you got is "close enough for government work," as they say. There were numberous variations of this woofer, but all had the slug-type Alnico-5 magnet and cloth surrounds. Most are therefore interchangeable. --Tom Tyson Attached image: AR-4 woofer.

Tom/Roy: to continue the 'mystery' a bit more, I removed the coils from the speakers the woofers came out of. They don't match anything listed in the AR coil list (Dwg. # 102014). "265" is written on each (# of turns I presume). I meas. the mH and DCR and got 1.75 and 0.7 ohms respectively. I also measured the wire ga. and confirmed it is 17 ga. FWIW, the speaker ser. #'s are FX 41343 & FX 41133.

[owlsplace]

I have two woofers that look similar to originals* that had cloth surrounds. However, someone decided to experiment with sealing the cloth and failed miserably (seems like they used shellac!). Each has an alnico magnet rear end. The cones have the four line cross-hatch pattern I know was on some of the AR originals

The p/n's on the back are 1414, 137 610, and 5808096, each printed on a different row. There's no mention of AR.

Could these be ABT replacements? or, one of the many variants AR used in the 4x's. AR historians?

I've cut off the sad, stiff cloth surrounds and installed 8 inch BA filleted foams which brought the Fs down to a nice, respectable 32 hz but still am wondering about the origin of these.

* the similar look is mostly at the rear end. The frame od is not round, but instead has bulges at the bolt holes.

Digging up an old thread here but I also came across these woofers and they do indeed seem to have some kind of shellac in the surrounds. I am attempting to revive them using an alcohol wash with some degree of success so far.

I am curious if anyone has attempted to make new cloth surrounds for any of the 8, 10, or 12 inch woofers. What would be an appropriate sealant. Hopefully not shellac! Not sure why they would do that. Seems like some die-cut cloth, mould, sealant, release agent would be about all that is needed to do this.

Anyone interested in new cloth surrounds for classic AR woofers?

Roger

[JKent]

Funny this just came up. Last week I was considering a pair of KLH Model Fives that had been "re-doped" with PVA glue. Roy confirmed there was no way to remove the glue so I contacted Bill LeGall of Millersound. He said he could make new cloth surrounds for them.

As it turns out I decided against the Fives but if you need new cloth surrounds....

-Kent

[ra.ra]

Roger, your post does not mention anything about the texture or compliance of your cloth surrounds, and I'm curious why you have assumed they are coated with shellac. Visually, the close-up Tom has shown in post 2 could almost be amber shellac, but indeed that is the correct appearance for the tacky butyl coating. While alcohol is indeed the correct solvent for shellac, toluene or toluol is the solvent used in the butyl solution, but lacquer thinner is another volatile solvent that does a good job of softening the original dope coating.

[owlsplace]

Funny this just came up. Last week I was considering a pair of KLH Model Fives that had been "re-doped" with PVA glue. Roy confirmed there was no way to remove the glue so I contacted Bill LeGall of Millersound. He said he could make new cloth surrounds for them.

As it turns out I decided against the Fives but if you need new cloth surrounds....

-Kent

Great minds run in circles ... I sent him an email as I am not interested in modding these old woofers with foam surrounds ... will update when I have a reply.

The original doping on these surrounds looks like some type of polymer with a shellac top coat used to cut down on its sticky qualities. That is my best guess anyway. Both compounds have degraded which is not surprising considering their age.

Roger

[DavidDru]

Interestingly enough, over the weekend i rotated the big woofers on my Altec Valencias 180 degrees. It's the prescription for those after so many years in their original configuration because the dope used on the surrounds has mostly settled on the bottom. Sticky amber colored stuff. I took what I could off that has run off onto the baffle edge and edge of the driver but was curious if there is anything else I should/could do.

[owlsplace]

Roger, your post does not mention anything about the texture or compliance of your cloth surrounds, and I'm curious why you have assumed they are coated with shellac. Visually, the close-up Tom has shown in post 2 could almost be amber shellac, but indeed that is the correct appearance for the tacky butyl coating. While alcohol is indeed the correct solvent for shellac, toluene or toluol is the solvent used in the butyl solution, but lacquer thinner is another volatile solvent that does a good job of softening the original dope coating.

Very stiff ... shellac based on Carl's comment and my observation about what solvents were able to soften it. They are perhaps playable but no where close to the original specs.

Toluene has been taken off the market here because kids are into using it for confined vapor tripping. I didn't feel like mail-ordering a gallon to try it out.

Roger

[t1500]

I can get toluene by the quart here in Maine at a local ACE Hardware. In the paint section.

[ra.ra]

Agreed that it is prudent to remind everyone that these type of volatile solvents need to be used only with conscientious safety precautions, even it means gloves, respirator, and goggles. All of these chemicals commonly available at the hardware store - - toluene, MEK, lacquer thinner, many paint strippers, and more - - can be hazardous and require ample ventilation when used.

One more totally unscientific observation about these 8" surrounds. Based on a casual 'touch test' of a dozen cloth woofers from AR-4's and 4x's, my modest collection offers this consistent conclusion: the black cloth surrounds (lamp black added to the butyl mix, I believe) are noticeably more soft and pliable than are the amber colored surrounds (see posts 2 and 8) on my specimens, yet I am fully confident that these lighter, non-black surrounds are still performing as originally intended despite a slightly stiffer feel when touched with a finger. They all sound very good when properly installed in the cabinet.

[owlsplace]

Funny this just came up. Last week I was considering a pair of KLH Model Fives that had been "re-doped" with PVA glue. Roy confirmed there was no way to remove the glue so I contacted Bill LeGall of Millersound. He said he could make new cloth surrounds for them.

As it turns out I decided against the Fives but if you need new cloth surrounds....

-Kent

Bill is willing to do them on a one-off basis when he isn't too busy because of the time involved. I am more interested in finding a supplier of surrounds or making my own surrounds if necessary. So, I will continue to investigate all possible avenues before deciding.

Roger