10" WOOFERS DIFFERENCE

[DON]

I'm getting ready to reassemble my 2ax and 5s and I have three pairs of 10" woofers. Two are the same but the other one is noticeably heavier than the other two. The lighter ones have the magnets edges wrapped with tape. The heavier ones don't have tape and have the numbers 5617347 on the magnet. The lighter ones have nov. 1970 on the magnet but no part number. One set will be used in 2ax and the other in 5s. Should the heavier one go in the 5 or does it matter? Thanks. Don.

I'd post photos but I can't get them small enough

[DON]

Geez! twenty people don't know anymore than I do? Oh well I'll just use one of each in the 2ax and one of each in the 5s. that should even things out.

[Robert_S]

I'd hazard a guess that the "lighter ones . . . magnets edges wrapped with tape" would be best placed in the AR-2ax, though they may well be interchangeable.

Robert_S

[ra.ra]

While I understand the frustration in posting pics, it is often the very best method to get specific advice on a particularly situation - - I think in a previous post I may have tried to walk you thru this. But, even without pics, I'll try to add a little value here.

I am not exactly sure how your magnets might be different, or what method you may have used to determine this. I have only had one experience with these woofers (2ax's), and mine have taped magnets, screened baskets, and flat dust caps. Any of this sound familiar?

I've attached two images for information. First is a portion of the 1979 AR parts list which, in fact, does give different part numbers to the 10" woofs in the 2ax and the 5 speakers, even though there is no hint at what that difference might actually be (magnet size, perhaps?). As I began responding to your post, it occurred to me that I have an image (see below) of my 2ax woofer sitting on a postal scale, and it seems to weigh in at close to 3 pounds exactly.

My 2ax woofers were stamp-dated Sep 13 1972 on the tape. The printed 5617347 on your woofers is not a part number - - - the 561 might be a stocking code, but the 7347 indicates date of production as 47th week of 1973.

[DON]

Thanks rara and Robert. I do know "how" to post photos and I think I finally got one sized correctly ad posted it. My problem is with I Photo and resizing.

ra ra the woofer photo you posted is just like the lighter woofer. I haven't weighed these but the weight difference is apparent when i'm handling them. The heavier ones have a somewhat flat dust cap with the handwritten figure 5 on it and the others have a prominent dome.

I think maybe I'll just use the heavier one in the 5s. It's just that I'm closer to being ready to putting the woofers in the 2ax. I'll continue my education in posting photos and I feel stupid not knowing exactly what Photo and my I Mac require of me. Everyone here does it so easily but apparently windows makes sizing simpler. Thanks don

[tysontom]

I'm getting ready to reassemble my 2ax and 5s and I have three pairs of 10" woofers. Two are the same but the other one is noticeably heavier than the other two. The lighter ones have the magnets edges wrapped with tape. The heavier ones don't have tape and have the numbers 5617347 on the magnet. The lighter ones have nov. 1970 on the magnet but no part number. One set will be used in 2ax and the other in 5s. Should the heavier one go in the 5 or does it matter? Thanks. Don.

I'd post photos but I can't get them small enough

Don, the 4-bolt, 10-inch AR-2ax and AR-5 woofer (with the masking tape over the assembly) used a pole-piece magnet in the pre-1973 versions. This woofer used the 1-1/2" voice coil with the same "overhang" as the later version with the square ferrite magnet (which was considerably heavier due to the ferrite magnet). In actuality, the pole-piece-magnet woofer is very similiar to the ferrite-magnet version (4-bolt, that is) in efficiency since the magnet is right against the voice coil, forming the center element or "pole piece." Therefore, the flux density was about the same as the larger ferrite magnet, since the pole-piece version doesn't lose flux density through the iron top plate. This type of assembly had many names, including slug magnets, pole-piece magnets and so forth. The magnet material was actually Alnico 5, but the total "magnet assembly" weight was considerably less than the later ferrite version. This later version -- after AR moved from Cambridge to Norwood in 1973 -- had a square ceramic ferrite magnet sandwiched in the usual fashion between a top plate and a bottom plate (holding a steel pole piece between). Therefore, both woofers are very close, but you would be better off to use the same type woofer for each speaker, rather than mixing and matching, even though the differences are slight. The old original lightweight woofer is excellent, so don't worry about the weight of the speaker; it has very little to do with performance. The only caveat on the pole-piece magnets has to do with excessive power input: if the owner of the speaker applied too much power over a long period of time to the speaker (point of distortion over long periods), the magnet itself can lose some magnetism. This is fairly rare, and the end result is a noticeably weak-responding speaker.

Therefore, both woofers are about the same, each with the same free-air resonance and approximately the same sensitivity. Both styles of woofers had the same voice coil, and the cones are very similar in weight and density. The AR-5 did have an early variation from the AR-2ax: it had an special cone with a round dust cap rather than the flat version used on the AR-2ax. Later on, all of the 10-inch woofers used the flat cap until the mid-70s versions, such as used on the AR-14. Note: in all of this discussion, I'm not referring to the original AR-2/AR-2a and early AR-2ax woofer with the 6-bolt flange.

I hope I didn't confuse you further....

--Tom Tyson

[DON]

Thanks Tom. You cleared it all up for me. I really do appreciate your very informative explanation of the differences in these woofers. I had incorrectly assumed that the heavier woofer would be stronger. A few stickies on the 5s and 2ax would be very helpful to everyone who isn't working with the AR3a.

Don