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AR2ax Help/Advise


JB2009

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Can anyone help me with this.  Have two AR2ax speakers. Crossovers, pots, are new and new surrounds. The woofers are 1970 vintage taped magnet 6 hole mounts. One speaker has a #5 woofer coil the other has a #7 coil. One woofer measures about 5 ohms higher than the other (no coil in the circuit).  They sound ok except the one with the #7 coil does not have as much output so the speakers seem unbalanced. Does anyone have any ideas or fixes to match the woofers more closely. Would matching the coils help. Not sure why they are different.

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Hi JB2009, welcome to the forum. The AR 2ax evolved over the years from the early version with the cloth surround woofer to the later version with the foam surround woofer. The early version had the #5 coil ( 1. 2 mh) and the later version had the #7 coil ( 1,88 mh). There is a lot of information regarding these changes so you do have two AR 2ax speakers, just different versions. The early version also had a 1 3/8 inch phenolic tweeter while the later version had the 3/4 paper tweeter.

Dean

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Hi Dean,

Thanks for the info. It appears this may be a hybrid or something.  Both of these speakers have the exact same tweeter (3/4), and midrange drivers. The woofer are the same except resistance a little different. The woofers were dated 2 months apart.

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There was some transitional  time among the versions and in some instances, adapter rings were used to adapt the foam version woofer ( which it sounds like you have) to the cabinet originally housing the larger cloth surround woofer. I also have a pair of AR 2ax speakers with the early cloth surround woofers but also with the 3/4 paper dome tweeter.  So, there was some mix and matching of components as one version replaced the other. Mids always stayed the same in the versions. So, it sounds like your speakers may have the wrong coil  and were most likely adapted to use the later foam surround woofer with the xover for the cloth surround woofer of the earlier version. The coil can be easily changed out to one with the proper mh value  so this should not worry you.

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OR, if you do have foam surround woofers, inductor coil values  add together when in series, so you could jus add another 0.7 mh coil in series with the current #5 to use with the foam surround woofer. Not sure about the difference in ohm ratings between the woofers - a 5 ohm difference seems wrong. You are sure they are both original AR 10 inch foam woofers?  

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I don't have an adaptor ring. Both woofers are 11' diameter 6 hole mount and sealed with putty. It looks like only the coil is different.  This must have been before the transition to the 4 hole woofer. I also have two AR2a 's and they have the cast woofer with  6 hole mount. These are stamped steel early 6 hole woofer before the stamped steel 4 hole woofer. Mystery to me as how this happened. Maybe someone at the factory messed up and installed the wrong coil, but would that account for the low efficiency of the woofer.

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OK, so I understand that you do have the foam surrounds but they are on the same larger cast frames as the cloth surrounds? So, it sounds like your bass drivers are the same and I would venture to assume that at some period, AR actually attached foam surrounds to the larger cast frame before going to the smaller stamped frame. At this point, I would try and get the correct coil value in the xover in question before I did anything else. See if this makes a difference and then go from there. 0.5 ohm difference is not anything to be concerned over. There are much more knowledgeable AR enthusiasts on this Forum who might also have a suggestion but getting the coil mh correct is where I would start.  You could also just test the woofers independently ( out of circuit) to see if they have the same output independent of the inductor .

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There were three maybe four versions of the AR2ax. The one on the left has the transitional woofer with the larger 11 in frame only used around 1970. The middle early production one has the cloth surround woofer with the phenolic dome tweeter and the right one with the smaller woofer frame, but the same size cone. There possibly was another late final  version with a rear wired tweeter and different magnet woofer. Do you have the paper sheets with the serial numbers on the back. I doubt that AR would mix up the inductors, more than likely the earlier serial number one has had the original woofer swapped out with the transitional woofer since they both had 6 screws. The tweeters were also replaced with the better 3/4 in dome units. Just change the inductor and you are good to go. Also make sure everything is sealed up and there are no air leaks. Enjoy your 2ax's because they are very good 10 in three ways. 

Ny9FQOW.jpg

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Hi IARrboyd,

Great pictures.  Looks Like I have the one on the left. Both woofers were stamped early 1970 with the taped magnets. Thanks for all the help everyone.  The speakers sounded great except the woofer difference.  The one with the #5 coil sounded better. Will replace the #7 with #5 and see how they sound.  What was the main reason for AR changing coils? I really appreciate all the help.

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30 minutes ago, lARrybody said:

They all had 6uf tweeter and 4uf midrange capacitors.

Whoops....I think you got this mixed up - - it should read 4uF tweeter and 6uF midrange.

12 hours ago, JB2009 said:

I mean to say .5 ohms not 5 ohms

When measuring DCR, I don't think it's unusual to find a 1/2 ohm difference between two 50 year-old similar drivers. You have mentioned a preference for the speaker with the #5 coil, but it's unclear to me which woofer is paired with the preferred cabinet/crossover. Since you've already had the woofers out-of-circuit to measure DCR, it should be easy to swap them into each others' original cabinet to see if any different audible perceptions result.

On the 2ax permutations, this summary offers a very good description, but it does not address the capacitor values or the change of coil. Also attached are various foam woofers: 6-hole stamped basket with wide flange; 4-hole stamped basket with 6-hole adapter; and later version with square ferrite magnet.

AR-2ax history.jpg

10%22 woof wide flange basket.jpg

10%22 adapter ring 2.jpg

AR-2ax woofer.jpg

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Thanks for all the pics.  The woofers are both stamped steel 6 bolt mounts no adaptor rings.  The crossover's caps are identical in both cabinets.  So the only difference I can detect is the coil size. Since both woofers appear to be constructed the same I don't quite understand the coil difference still, but I will take the suggestion and swap out the coils and see which value gives me the best sound.

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1 hour ago, JB2009 said:

...but I will take the suggestion and swap out the coils...

In the end, you may be best served by having appropriate matching coils, but just to be clear, my suggestion for a test was far simpler - - - since you have mentioned the two woofers having different resistance measurements, I was just suggesting swapping the woofers (not the coils) between speaker cabinets to see if that might provide a better balance of output, as mentioned in your original post.

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1 hour ago, ra.ra said:

Whoops....I think you got this mixed up - - it should read 4uF tweeter and 6uF midrange.

Yes I did. Just replaced the tweeter caps on some AR3a's which have the same tweeter except for 4 ohm voice coils which use the 6uf caps. 

The late model square magnet  2ax woofers you pictured clearly state 2ax on the labels and have the part number 3903-2. The woofers pictured below also came from some late model 2ax's but sport the part number 200004-2.  Whats up with that?  Maybe AR had a variety of part numbers.

w2FmNeEl.jpg 

 

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I did some testing of the woofer.  Not scientific but some measurements.  Hooked each up to a tone generator and measured the db level of each.  The one that had the #7 coil is about 2db less than the woofer which had the #5 coil.  The test were made with just the woofer connected no coil inserted.   Is 2db loss within specs for a woofer of this type and do you think that is the main difference in output levels when playing. I would note one cone material looks a little different than the other.

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2 hours ago, lARrybody said:

The late model square magnet 2ax woofers you pictured clearly state 2ax on the labels and have the part number 3903-2. The woofers pictured below also came from some late model 2ax's but sport the part number 200004-2.  Whats up with that? 

As much as I try to pay attention to the numbers on these tags, sometimes another indecipherable code comes along to confuse us. A very similar looking tag appears on this 8-inch AR-6 woofer. I just dunno......

1 hour ago, JB2009 said:

The one that had the #7 coil is about 2db less than the woofer which had the #5 coil. 

Which one had the higher DC resistance reading?

woof rear A.jpg

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