BassoRider Posted July 10, 2007 Report Share Posted July 10, 2007 Hi, all!My first post here.I bought a pair of AR 2ax in 1975, and I'm planning to replace the caps in the crossovers. To my surprise I found 4uF caps soldered across the plus/minus terminals of the midrange elements.I started a thread at AudioKarma...http://www.audiokarma.org/forums/showthread.php?t=117356...and I was kindly adviced to post here.Any advice on this (unusual) arrangement? Remove or replace? Link to comment Share on other sites More sharing options...
KlausDK Posted July 10, 2007 Report Share Posted July 10, 2007 Hi BassoRiderWhat does the rest of the cross-over look like? Normally there is a 4 myF for the tweeter and a 6 myF for the midrange (in series with the drivers). They are often combined in a big yellow "box" capacitor with three leads coming out. Normally 2ax also has a coil in series with the woofer.BRgds Klaus Link to comment Share on other sites More sharing options...
BassoRider Posted July 10, 2007 Author Report Share Posted July 10, 2007 As far as I can tell a standard cross-over, with a large 50V cap with taps for 6 and 4uF. The other components I'm not sure about, but it corresponds with pictures I've seen.I'm on vacation right now, but can post more pictures after July 20.I'm very grateful for your interest. Maybe it's a unique speaker configuration! Link to comment Share on other sites More sharing options...
KlausDK Posted July 10, 2007 Report Share Posted July 10, 2007 I am not familiar with the AR-2ax, recently acquired a set, but I haven't restored it yet. Just went out to check them, and took out one of the midrange drivers: no resistors, no capacitor. My 2ax's are from 71 with alnico magnet woofers. Then I checked my inventory of spare drivers, somebody gave my a box with 2ax drivers some time ago, among them four spare midranges and and three of them have the two resistors and the cap, one didn't.I think we have to have some of the hard core AR CSP members to help here.BRgds Klaus Link to comment Share on other sites More sharing options...
RoyC Posted July 11, 2007 Report Share Posted July 11, 2007 BassoRider,AR did play around with the 2ax midrange in the mid 70's. We have speculated that it had something to do with a woofer change to the ceramic magnet type. The later 2ax midrange, although appearing identical to the original, had a higher impedance...dcr of 9 ohms as opposed to 6 ohms. It appears that the addition of the resistors to the original midrange occurred during a transition period leading to the revised midrange driver.I would leave the circuit unchanged.Are the woofers identical?Roy Link to comment Share on other sites More sharing options...
BassoRider Posted July 11, 2007 Author Report Share Posted July 11, 2007 The woofers are identical, the speakers are a matched pair I bought new. The woofers are the "Modern" type:http://layneaudio.hypermart.net/2axWoofers.JPGSorry, no pictures of the rest of the crossover at the moment, but it seems perfectly standard. Link to comment Share on other sites More sharing options...
BassoRider Posted July 11, 2007 Author Report Share Posted July 11, 2007 Yes, I will leave the circuit unchanged (but with modern replacement caps). I understand now that the caps on the midrange drivers are an integral part of the crossover design. I'm sure they knew what they were doing at AR! Link to comment Share on other sites More sharing options...
charger3834 Posted July 12, 2007 Report Share Posted July 12, 2007 Interesting post! We will need to know the serial numbers ? The leads are wired conventionally i.e. yellow is negative. Does it have a front or rear wired 3/4" tweeter ?You have arrived at the right place for AR info. The AR-2ax had gone through several design modifications over its 12 year lifespan(1964-1976) It had a major redesign in 1970 and several smaller changes in the 1970-1976 period. We need to doccument these changes before we can even begin to understand the reasoning behind them. But you are correct that AR knew exactly what they were doing.Both the woofers in your photo are "new style," post 1970, foam surround, stamped steel frame woofers, with a cone that provided very smooth midrange/midbass response. It also dampened edge reflections very well.In 1974, the Alnico slug version was replaced by the square, ceramic magnet version that had a slightly stronger midrange output. The midrange resistors, and eventually the higher impedance mid that Roy describes is associated with these versions. Link to comment Share on other sites More sharing options...
BassoRider Posted July 12, 2007 Author Report Share Posted July 12, 2007 I'm on vacation right now, and will post serial numbers and more pictures after July 20.Two thin wires on the front go up to the tweeters.The woofers have square magnets (note! it's not my photo!). Link to comment Share on other sites More sharing options...
JKent Posted July 12, 2007 Report Share Posted July 12, 2007 Here are befre & after pics of my AR2ax x-over upgrade. Zens are no longer available but you can use caps from Parts Express or MadisoundKent Link to comment Share on other sites More sharing options...
Guest gregounours Posted July 12, 2007 Report Share Posted July 12, 2007 You did a great job inside these cabinets. I didnt bother soldering directly to the pots. I kept the original caps box and hid the new one in though.Also my Ar2ax have serial in the 230 000 and I have the old woofer. How high did they go. I also just have a serial # related question. Does anybody knows around what serial # the switch from cloth to foam surround happened.Greg Link to comment Share on other sites More sharing options...
charger3834 Posted July 13, 2007 Report Share Posted July 13, 2007 >>Also my Ar2ax have serial in the 230 000 and I have the old>woofer. How high did they go.Not sure probably 280XXX I also just have a serial #>related question. Does anybody knows around what serial # the>switch from cloth to foam surround happened.>>GregThe new AR-2ax was released in 1970 at serial number 125000. The new foam surround woofer was part of that redesign. Link to comment Share on other sites More sharing options...
BassoRider Posted July 20, 2007 Author Report Share Posted July 20, 2007 Here's a pic of the crossover. Seems standard to me, apart from my bypassing the tone controls many moons ago!2514.txt Link to comment Share on other sites More sharing options...
BassoRider Posted July 20, 2007 Author Report Share Posted July 20, 2007 And here is one woofer. Identical in both speakers.2515.txt Link to comment Share on other sites More sharing options...
BassoRider Posted July 20, 2007 Author Report Share Posted July 20, 2007 And here is the serial number (008332). It seems very low... Could they have been specific for European models?2516.txt Link to comment Share on other sites More sharing options...
BassoRider Posted July 20, 2007 Author Report Share Posted July 20, 2007 I couldn't resist... A pic of the speakers in good company!2517.txt Link to comment Share on other sites More sharing options...
KlausDK Posted July 20, 2007 Report Share Posted July 20, 2007 Hi Basso-riderCould you post a picture of the woofer from the front side?What is the number stamped on the magnet beginning with 561 XXXX read, is it 8414 or 9414?BRgds Klaus Link to comment Share on other sites More sharing options...
charger3834 Posted July 21, 2007 Report Share Posted July 21, 2007 Yes Indeed, that would be a European 2ax. That vintage 2ax would correspond with an American built unit in the 250000 range.(circa 1974) Link to comment Share on other sites More sharing options...
BassoRider Posted July 25, 2007 Author Report Share Posted July 25, 2007 Klaus, I think the number is 561 7414.Here's a picture of the woofer. Link to comment Share on other sites More sharing options...
BassoRider Posted July 25, 2007 Author Report Share Posted July 25, 2007 I fashioned new filters from Audyn and Rifa polypropylene and polyester caps. The values are 3.9 and 6.07 uF, +/- 5%. Speakers work fine! I think there is more definition in lower octaves. Link to comment Share on other sites More sharing options...
Carlspeak Posted July 25, 2007 Report Share Posted July 25, 2007 >Hi Basso-rider>>Could you post a picture of the woofer from the front side?>>What is the number stamped on the magnet beginning with 561>XXXX read, is it 8414 or 9414?>BRgds Klaus>Checked my EIA codes but couldn't find 561 on the list. Waldom Electronics EIA number is close. Could it be them that fabricated woofers for AR?CarlCarl's Custome Loudspeakers Link to comment Share on other sites More sharing options...
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