lakecat Posted December 31, 2017 Report Share Posted December 31, 2017 (Most recently I repaired a pair of 3a's used for a college "party". The engineering student owner was showing off his vintage system, which included a Pioneer SX-1250 receiver. He blew both tweeters, one midrange, and melted the plastic shafts of all (burned out) pots. The (12 inch) woofers survived.) Roy.....I have to ask what the hell did that guy do to do all that damage? Usually...the receiver shuts down when overdriven and hot. and to Michael T.....welcome to the AR club where patience is a virtue. Roy has helped more novices and experts than can ever be measured. Sharing his knowledge and time willingly has enabled me to become an AR addict....:) Thank you Roy.....well...most of the time anyways...lol. Link to comment Share on other sites More sharing options...
Michael T Posted December 31, 2017 Author Report Share Posted December 31, 2017 2 hours ago, lakecat said: where patience is a virtue Patience, as well as schedule and a bit of self confidence issues, is the reason that since Dec 11, when I purchased these speakers I have done little except purchased most of what I'll need and disassembled the cabinet as well as amassed threads in 2 forums with 4 pages of questions and advice each. As well as PMs to a few people. When I'm done, I expect I'll be a bit of an expert . Link to comment Share on other sites More sharing options...
Michael T Posted January 3, 2018 Author Report Share Posted January 3, 2018 Updated the drawing that i came up with.See later post Link to comment Share on other sites More sharing options...
Michael T Posted January 3, 2018 Author Report Share Posted January 3, 2018 On my drawing, there is a small gap in the line just above the mid, it is a mistake, it should be solid. Link to comment Share on other sites More sharing options...
ra.ra Posted January 4, 2018 Report Share Posted January 4, 2018 Michael, your drawing looks pretty good to me (although I have not double-checked the numbers on the L-pad terminals). There are two schematics I often reference for the 2ax speaker, and I am familiar with the one that you have modified. The other schematic I refer to is posted below. Since your drawing might be used for future reference, I have three small comments/suggestions: 1. You might want to comment on your specific woofer and coil combination. 2. Maybe remove the remark about capacitor options/choice? 3. I find the layout of the linework in the attached schematic to be a little easier to follow. When possible, I like to see the level control (pot or L-pad) directly behind the driver it serves. Just my $0.02. Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 Thank you for the comments and suggestions. I planned to clean up the drawing so I will take into account what you have said. I threw it together at work on break and after I converted it to .pdf I didn't save the .dwg file so ill have to start from scratch Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 1 hour ago, Michael T said: Thank you for the comments and suggestions. I planned to clean up the drawing so I will take into account what you have said. I threw it together at work on break and after I converted it to .pdf I didn't save the .dwg file so ill have to start from scratch Michael, The L-pad terminal labels are incorrect in your drawing. Regardless of the AR model, all one has to do is disconnect the pot wires and attach them to the L-pad terminals as follows. There are no exceptions. L-pad #3=Pot #1 L-pad#1=Pot #2 L-pad#2=Pot "B" The problem with making definitive statements about the polarity of the 2ax drivers is the absence of + and - labels on the tweeter and mid. Recently the "yellow" side of the 2ax mid has been shown to be the likely negative side of the driver, unlike those of the AR-3a...so the 2ax mid's polarity is probably reversed. For the vast majority of 2ax restorations, when original wiring is present, it should be consistent with the schematic posted by ra.ra. When using L-pads, the only thing that changes is the level control terminal numbers...and, possibly, the insertion of a 25 ohm resistor across #1 and #2 L-pad terminals. Roy Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 This is the reference I used to make the drawing as I did. I assumed that if 1 was common on both and 2 on the pot and 3 on the lpad were input, then the would be wired as I drew it. I don't remember where I downloaded it from. Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 1 hour ago, Michael T said: This is the reference I used to make the drawing as I did. I assumed that if 1 was common on both and 2 on the pot and 3 on the lpad were input, then the would be wired as I drew it. I don't remember where I downloaded it from. The L-pad drawing is correct...but the bottom left pot drawing notes are not in keeping with how the potentiometer is implemented in an AR speaker. Pot terminal 1 is the input (corresponding to L-pad terminal 3), and pot terminal 2 is common (corresponding to L-pad terminal 1) in AR speakers. If it is reversed, the increase/decrease rotation will be in the wrong direction. The drawing on the right is correct, showing pot terminal 2 as a "common" terminal. Pot terminal "B" as the output corresponding to L-pad terminal 2 is correct. Confusion is sometimes caused by the fact that AR capacitors are often placed on the negative side of the circuit. Roy Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 38 minutes ago, RoyC said: Confusion is sometimes caused by the fact that AR capacitors are often placed on the negative side of the circuit. Confusion is also caused by having just enough information to be dangerous . I really thought I was on to something. Oh well, at least I got the right info before I finished wiring up my crossover. And that is what this forum is about. Link to comment Share on other sites More sharing options...
ra.ra Posted January 4, 2018 Report Share Posted January 4, 2018 I am pleased to see that Roy has clarified the confusion that results from these terminal designations, and once Michael tunes up his schematic diagram, it should become a very useful reference for future restorers. Link to comment Share on other sites More sharing options...
JKent Posted January 4, 2018 Report Share Posted January 4, 2018 1 minute ago, ra.ra said: once Michael tunes up his schematic diagram, it should become a very useful reference for future restorers. Suggestion, Michael: If you post a corrected diagram please delete the original one to avoid confusion. Very nice schematic drawing btw. Link to comment Share on other sites More sharing options...
GD70 Posted January 4, 2018 Report Share Posted January 4, 2018 When I restored a set of 2a's, I also used L-pads, original pots were beyond use, and wired them incorrectly, a common mistake. Roy came to the rescue for me on that one as well. Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 As i stated earlier the masonite rings that the spider is attached to on my woofers have come loose from the basket. Would it be a good idea to carefully pry loose the masonite ring that attaches the cone to the basket so i can take the cone assembly out? This would allow me to properly clean the area that the spider ring attached to as well as check for damage to or cracks in the voice coil. I realize that I would have to be extremely careful removing the voice coil leads from the connectors and need to carefully mark the position of the masonite ring for the cones. I want to make sure the spider rings get glued properly and it looks a bit cramped in there to clean the basket with the cone still in place. Link to comment Share on other sites More sharing options...
stan461 Posted January 4, 2018 Report Share Posted January 4, 2018 13 hours ago, RoyC said: Michael, The L-pad terminal labels are incorrect in your drawing. Regardless of the AR model, all one has to do is disconnect the pot wires and attach them to the L-pad terminals as follows. There are no exceptions. L-pad #3=Pot #1 L-pad#1=Pot #2 L-pad#2=Pot "B" The problem with making definitive statements about the polarity of the 2ax drivers is the absence of + and - labels on the tweeter and mid. Recently the "yellow" side of the 2ax mid has been shown to be the likely negative side of the driver, unlike those of the AR-3a...so the 2ax mid's polarity is probably reversed. For the vast majority of 2ax restorations, when original wiring is present, it should be consistent with the schematic posted by ra.ra. When using L-pads, the only thing that changes is the level control terminal numbers...and, possibly, the insertion of a 25 ohm resistor across #1 and #2 L-pad terminals. Roy Thanks Roy. Simple enough for me. "and, possibly, the insertion of a 25 ohm resistor across #1 and #2 L-pad terminals." Is that 25 ohm resistor insertion for both tweeter and mid or just for the mids? Thanks for any clarification. Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 6 hours ago, Michael T said: As i stated earlier the masonite rings that the spider is attached to on my woofers have come loose from the basket. Would it be a good idea to carefully pry loose the masonite ring that attaches the cone to the basket so i can take the cone assembly out? This would allow me to properly clean the area that the spider ring attached to as well as check for damage to or cracks in the voice coil. I realize that I would have to be extremely careful removing the voice coil leads from the connectors and need to carefully mark the position of the masonite ring for the cones. I want to make sure the spider rings get glued properly and it looks a bit cramped in there to clean the basket with the cone still in place. I usually remove the entire cone assembly. I use the same shims used for re-foaming woofers when re-gluing the rings in place to prevent voice coil rubbing. Roy Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 2 hours ago, stan461 said: Thanks Roy. Simple enough for me. "and, possibly, the insertion of a 25 ohm resistor across #1 and #2 L-pad terminals." Is that 25 ohm resistor insertion for both tweeter and mid or just for the mids? Thanks for any clarification. I only use it for the mids. The L-pad results in a bit more output and lowers the crossover point slightly, and the resistor compensates for these effects. The old tweeters, however, often suffer from degraded output, and the L-pad without resistor can help in this regard. Roy Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 On 12/31/2017 at 10:43 AM, lakecat said: (Most recently I repaired a pair of 3a's used for a college "party". The engineering student owner was showing off his vintage system, which included a Pioneer SX-1250 receiver. He blew both tweeters, one midrange, and melted the plastic shafts of all (burned out) pots. The (12 inch) woofers survived.) Roy.....I have to ask what the hell did that guy do to do all that damage? Usually...the receiver shuts down when overdriven and hot. The amp was fine. The speakers simply suffered from being driven at excessive volume for an extended period of time. One thing common to many of these stories involving novice owners of vintage equipment is the misunderstanding and misuse of the "loudness" function on the receiver. Roy Link to comment Share on other sites More sharing options...
genek Posted January 4, 2018 Report Share Posted January 4, 2018 On 12/31/2017 at 7:43 AM, lakecat said: I have to ask what the hell did that guy do to do all that damage? Usually...the receiver shuts down when overdriven and hot. "Speaker protection" generally triggers when a short or DC current is detected across the speaker connections, while "amplifier protection" generally triggers when the amp gets too hot. Neither of these will protect speaker components that are unable to withstand the normal output of the amplifier the speaker is connected to. Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 K Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 Boy I'm glad we got the melted speaker mystery solved. Link to comment Share on other sites More sharing options...
RoyC Posted January 4, 2018 Report Share Posted January 4, 2018 2 hours ago, Michael T said: Ok guys, I think I got the drawing right this time, let me know if you find anything wrong. AR-2ax L-Pad2.pdf Michael, If this is for general reference, the 3.9uf capacitor you used in your project should be shown as the original 4.0uf. Additionally: -The capacitors do not need to be film caps. -the AR #5 coil is 1.187 mh. -The 2ax mid is 3 1/2 inch For the record, I belatedly lobbied to not include the "non-inductive" recommendation for the 25 ohm resistor in the L-pad section of the 3a restoration guide. In this application .0005+/- mh difference is not at all significant. Any 10 watt (or greater) 25 ohm resistor will do the job, "non-inductive" or otherwise. Roy Link to comment Share on other sites More sharing options...
Michael T Posted January 4, 2018 Author Report Share Posted January 4, 2018 42 minutes ago, RoyC said: he AR #5 coil is 1.187 mh. I was going by the drawing that ra.ra posted above. 44 minutes ago, RoyC said: -The 2ax mid is 3 1/2 inch Typo. I was trying to be helpful but it seems that between my propensity to make small oversights and the large number of documents available, some with oversights as well, i should leave this stuff to others. Link to comment Share on other sites More sharing options...
RoyC Posted January 5, 2018 Report Share Posted January 5, 2018 41 minutes ago, Michael T said: I was going by the drawing that ra.ra posted above. ...which upon closer examination turned out to be incorrect. It is probably worth the effort to play around with these things, as it forces us to understand and discuss details. Either way, most people are simply going to replace the caps and level controls in kind and not worry about it. Below is an AR coil chart provided by Tom Tyson awhile back. The "Used On" column is not complete, but it is a good resource. Roy Link to comment Share on other sites More sharing options...
Michael T Posted January 5, 2018 Author Report Share Posted January 5, 2018 Again, I need to stick with asking questions and let the pros answer questions. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.