AR$X Notations

[oldguide]

I just bought a pair of 4x for $20. Aside from the usual fixes of cleaning the pots, fixing some cabinet scratches, replacing the stuffing and recapping, I have a question for the old AR hands. On both these speakers there are red letters on them. Each has what looks like a five or an "s" along with what looks like the initials of a signature. Was this something done by AR or someone else?

The speakers do not look to be modified other than in one way. The AR-type batting was still there, still has Sprague caps, etc. The drivers themselves look the same as on my other set of 4xs. The only difference is the inductor coil also has a five or "s" written on it. It appears to have been replaced because the connection from the speaker is directly soldered together rather than using a screw connection as in my other pair of 4xs. Is it possible the inductor was replaced?

If so, will the voicing on this match my other 4xs as I wonder if the xover is different. My other 4xs had the old ice block caps rather than Spragues.

If the inductors are different and I want a "matched" set of four do I need to find an inductor to match the earlier made pair? Or is this no big deal. I will be recapping with the same cap I used for the earlier pair.

Serial#s on new pair: 365328, 365232. Old pair: FX162519, FX162487.

Thanks for any help on this.

[JKent]

Hi

Earlier 4x's had a #4 inductor. Later ones had a #5. That's a "5" on the inductor.

According to Roy C the Spragues are the best caps AR used and are likely still good.

The other difference between early vs late 4x's was the amount of fiberglass stuffing.

Kent

[RoyC]

I just bought a pair of 4x for $20. Aside from the usual fixes of cleaning the pots, fixing some cabinet scratches, replacing the stuffing and recapping, I have a question for the old AR hands. On both these speakers there are red letters on them. Each has what looks like a five or an "s" along with what looks like the initials of a signature. Was this something done by AR or someone else?

Hi Kent and oldguide,

The information regarding the Sprague caps was shared with me by John O'Hanlon (johnieo), who has done MUCH capacitor testing of late!

Attached is a photo of the red mark described by oldguide, which is often seen on AR cabinets. It is a factory mark, but I don't know what it means.

Oldguide, the sound of your 4 speakers should be reasonably close, regardless of era. AR-4x woofer construction and response varied a bit as well, but did not significantly affect the overall sound character of the speaker.

Roy

[oldguide]

Hi Kent and oldguide,

The information regarding the Sprague caps was shared with me by John O'Hanlon (johnieo), who has done MUCH capacitor testing of late!

Attached is a photo of the red mark described by oldguide, which is often seen on AR cabinets. It is a factory mark, but I don't know what it means.

Oldguide, the sound of your 4 speakers should be reasonably close, regardless of era. AR-4x woofer construction and response varied a bit as well, but did not significantly affect the overall sound character of the speaker.

Roy

That is exactly the mark. What about the initialed signature?

As for the Spragues somewhere in the forum I had seen that they deteriorate with age. If not then it's just a matter of cleaning the pots (which aren't too bad). restuffing and some modest refinish work.

Also have to apologize for hitting the wrong key so this topic name is all messed up. AR made some speakers that are truly $ bargains but never a $x

[RoyC]

As for the Spragues somewhere in the forum I had seen that they deteriorate with age.

Generally speaking, the Spragues have held up better than the rest according to John. They are, however, 35+ year old electrolytics, so it is probably prudent to replace them when possible. I always do.

Roy

[oldguide]

Generally speaking, the Spragues have held up better than the rest according to John. They are, however, 35+ year old electrolytics, so it is probably prudent to replace them when possible. I always do.

Roy

Found the following from johnieo:

--AR changed the crossover frequency from 1,400- to 1,200-Hz somewhere between June 68 (s.n. 175,xxx) and Jan 69 (s.n. 225,xxx). The earlier units can be identified by the number "4" inductor (0.88 mH), whereas the later units used the AR number "5" inductor (1.187 mH).

---At about the same time, AR reduced the stuffing weight from 18 oz yellow fiberglass to 12 oz. This increased the Q factor of the speaker from about 0.5 to about 0.7.

Also:

Electrolitic capacitors drift over the years due to seal leakage. (See date code YYWW for the year and week of manufacture.) First C increases as the electrolyte concentration changes, then C finally drops to essentially zero, after the electrolyte has completely evaporated. The quality of the hermetic seal varied greatly with the manufacturing firm and that's one reason why some are no longer in business!

[RoyC]

Found the following from johnieo:

--AR changed the crossover frequency from 1,400- to 1,200-Hz somewhere between June 68 (s.n. 175,xxx) and Jan 69 (s.n. 225,xxx). The earlier units can be identified by the number "4" inductor (0.88 mH), whereas the later units used the AR number "5" inductor (1.187 mH).

---At about the same time, AR reduced the stuffing weight from 18 oz yellow fiberglass to 12 oz. This increased the Q factor of the speaker from about 0.5 to about 0.7.

Also:

Electrolitic capacitors drift over the years due to seal leakage. (See date code YYWW for the year and week of manufacture.) First C increases as the electrolyte concentration changes, then C finally drops to essentially zero, after the electrolyte has completely evaporated. The quality of the hermetic seal varied greatly with the manufacturing firm and that's one reason why some are no longer in business!

John and I compared 4x and 3a notes for the better part of three years, and he remains the repository of all the data:-)! Anyway, after his post above I very recently sent him many Spragues. After some rather sophisticated testing, he found that they have held up surprisingly well. We both agree, however, that replacing old electrolytics is always a prudent way to go if one does not have the means to measure the old caps, or would like insurance against failure.

Even though the woofer inductor and cabinet stuffing was changed, we have not been able to determine if it was the result of changes in the woofer (as it appears to have been with the 3a). The sonic character of the 4x remained very similar over the years, though the woofer varied somewhat in construction. I prefer, therefore, to use the original configuration IF I know the original woofers are in the cabinets.

Roy

[oldguide]

John and I compared 4x and 3a notes for the better part of three years, and he remains the repository of all the data:-)! Anyway, after his post above I very recently sent him many Spragues. After some rather sophisticated testing, he found that they have held up surprisingly well. We both agree, however, that replacing old electrolytics is always a prudent way to go if one does not have the means to measure the old caps, or would like insurance against failure.

Even though the woofer inductor and cabinet stuffing was changed, we have not been able to determine if it was the result of changes in the woofer (as it appears to have been with the 3a). The sonic character of the 4x remained very similar over the years, though the woofer varied somewhat in construction. I prefer, therefore, to use the original configuration IF I know the original woofers are in the cabinets.

Roy

The woofers in these appear identical to the ones in my 100000 series 4x. The only difference between the two is the inductor and the spragues in place of the ice block caps in the early 4xs.

[oldguide]

The woofers in these appear identical to the ones in my 100000 series 4x. The only difference between the two is the inductor and the spragues in place of the ice block caps in the early 4xs.

Not to get too crazy on this, but if i wanted to match the inductor values on the old 4x (.88) it appears I have two alternatives:

1) I could unwind the #5 inductor which is 1.187

2) Parts Express has a jantzen coil rated at .90.

So do I unwind the #5 or just replace?

Being totally new to inductors, if I wanted to unwind a #5 to turn it into a #4 how many turns would I unwind? I have found several tables online, but they ask for wire values and I do not know what wire was used in the ARs. A search of threads turned up nothing. There apparently used to be an inductor table Tom Tyson put together, but the links to it are all dead.

With everything else being the same between the old 4xs and the newer ones, changing the inductor would make them as identical as possible since the new caps would be the same.

[genek]

Not to get too crazy on this, but if i wanted to match the inductor values on the old 4x (.88) it appears I have two alternatives:

1) I could unwind the #5 inductor which is 1.187

2) Parts Express has a jantzen coil rated at .90.

So do I unwind the #5 or just replace?

The .90 coil sounds like the easier way to go to me. Without using an inductance meter as you unwind, just unwinding coils X number of turns is unlikely to get you any closer to "exactly" .88 than the .90, and might even be further off.

[RoyC]

oldguide,

Not that it makes a huge difference, but the AR inductor coils are 17 ga wire, which is generally not available today.

I have a bunch of AR coils, and would be happy to test and share a #4 or #5 or two (free...just postage).

Contact me through the forum message feature if you are interested.

Roy

[RoyC]

oldguide,

Not that it makes a huge difference, but the AR inductor coils are 17 ga wire, which is generally not available today.

I have a bunch of AR coils, and would be happy to test and share a #4 or #5 or two (free...just postage).

Contact me through the forum message feature if you are interested.

Roy

Oldguide, check your forum messages. My responses to your emails are apparently not getting to you.

Roy

[oldguide]

Oldguide, check your forum messages. My responses to your emails are apparently not getting to you.

Roy

Just a quick public thanks to Roy for all his help on this project and all he does for this forum. We are fortunate to have someone like him so willing to share and help those of us who are still learning.

[oldguide]

Just a quick public thanks to Roy for all his help on this project and all he does for this forum. We are fortunate to have someone like him so willing to share and help those of us who are still learning.

I finally have a theory about the markings in my speakers. I had not thought to look, but the signature in one matches a signature on the exterior card, meaning the inspector signed both the card and the speaker. This might explain the mysterious "S; which simply mean satisfactory.