4x inductor coil

[Guest Jim Collins]

I recently purchased a pair of AR 4x and they appear to have different inductors. One is marked "4" and one is marked "5". I have no equipment to test these so I have no way of knowing if they are of thee same value. The coil marked "4" appears to have less coil. Would it be best to buy two identical 1.2 mhz coils? Thanks

Jim C

[JKent]

I recently purchased a pair of AR 4x and they appear to have different inductors. One is marked "4" and one is marked "5". I have no equipment to test these so I have no way of knowing if they are of thee same value. The coil marked "4" appears to have less coil. Would it be best to buy two identical 1.2 mhz coils? Thanks

Jim C

Hi Jim

As John O'Hanlon (johnieo) told me when I had a similar situation:

Roy C. and I have been comparing notes on AR-4x details. 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."

So,,,, I would suggest you get another #5 inductor. There is probably a member here with a spare. And make sure you use about 11 oz. of fiberglass in both boxes. Replace the caps, clean the pots and you should have a nice matched pair.

Good luck!

Kent

[genek]

So,,,, I would suggest you get another #5 inductor. There is probably a member here with a spare. And make sure you use about 11 oz. of fiberglass in both boxes. Replace the caps, clean the pots and you should have a nice matched pair.

I think it would be a good idea to compare the rest of the components and the sound of the speakers as well. Not discussed in the referenced exchange is why the inductor and FG weight were changed. If the speakers have different woofers but their bass sounds the same as-is, perhaps it was to compensate for different components and you might be better off leaving well enough alone.

[Guest Jim Collins]

Hi Jim

As John O'Hanlon (johnieo) told me when I had a similar situation:

Roy C. and I have been comparing notes on AR-4x details. 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."

So,,,, I would suggest you get another #5 inductor. There is probably a member here with a spare. And make sure you use about 11 oz. of fiberglass in both boxes. Replace the caps, clean the pots and you should have a nice matched pair.

Good luck!

Kent

Thanks Kent... Both woofers are different, one has the magnet structure taped with masking tape, and the other is vented. No date on the vented (newer I presume) woofer and a date of 1968 on the other. Both have the cloth surrounds, however the older woofer is taller. Both tweeters are identical and only off by a few months in 1968. I will begin my search for the # 5 inductor and the proper woofer for that inductor... all will be equal. The rock wool that was removed weighs in at 17-18 ozs. from both cabinets. I am to replace with fiberglass weighing only 11 ozs??

[JKent]

Let's see if John or Roy chime in here regarding the stuffing.

Too bad but I just sold a suitable woofer. One new and one old as a matter of fact. OTOH they went cheap ($10 each) so you should be able to get one to make a pair without much expense.

[Guest Jim Collins]

I think it would be a good idea to compare the rest of the components and the sound of the speakers as well. Not discussed in the referenced exchange is why the inductor and FG weight were changed. If the speakers have different woofers but their bass sounds the same as-is, perhaps it was to compensate for different components and you might be better off leaving well enough alone.

Thank you Genek. The speakers are way off in the serial #'s so I imagine AR made some changes during production. The rock wool is the same weight in both units at 17-18 ozs. Although original AR,the woofers are very different.

[Zilch]

I describe two AR4x woofer variants and crossovers here:

http://www.audiokarma.org/forums/showthread.php?t=123113

They are very different.

[i also get radical with them there, but you don't have to read that part.... ]

[RoyC]

The earlier, larger magnet woofer was apparently a holdover from the AR-4, and the #4 coil was used in the earlier 4x models. There was a variation in the capacitor arrangement as well, but the most common tweeter crossover is a single 20uf cap (some early ones have 2 of them). All AR models had a reduction in stuffing around 1970, and 11oz of fiberglass is very common with the smaller magnet 4x woofer after that date. Other woofer variations have been noted along the way, including woofers with foam surrounds at the very end of the production run, but the crossover configuration and lesser stuffing amount appears to have remained the same after 1970+/-.

Whether these variations are important or not is dependent on how the speakers sound to the user. Presumably AR had reasons for the variations, and tried to maintain consistent performance as the changes were made. If the pair sound OK, and there isn't a noticeable mismatch between the two speakers, it is probably prudent to fix what needs to be fixed (ie pots, new caps) without changing anything else.

It is worth the effort to scroll through some of Zilch's 4x AK Forum posts, as he has much experience with this model.

Jim, I do have extra #5 coils and smaller magnet 4x woofers. If you decide you need them send me a PM.

Roy