AR 2-ax

[powerglide]

Thanks @ra.ra the schematic is invaluable to me at this stage. 

As mentioned early in the thread, I know sniff all about the electronic aspect of the build, once I get all the correct components together I'm having someone eyeball the layout and give me the 1/4 dollar tutorial on soldering. 

I began the restoration with the view point of upgrading the internals to get the most out of the drivers sonically, it has become apparent that I'm upgrading the internals to get the drivers to perform as they did when manufactured which hopefully is the same thing. I will be taking your advice @RoyC and using 25ohm resistors. 

Mouser's shipping is worse than PE - $24USD for a $1 part 

 

 

[JKent]

no sellers in oz? they don’t have to be special. 25 ohms 10 watts. Higher wattage is ok if there is room.

[powerglide]

4 minutes ago, JKent said:

no sellers in oz? they don’t have to be special. 25 ohms 10 watts. Higher wattage is ok if there is room.

Got to be?

 

[ar_pro]

How about these guys?

http://www.theloudspeakerkit.com/loudspeaker-components/crossovers-components/?pgnum=4

[JKent]

if there is no local store use the link gene supplied to mouser.  Be sure to check Australia 

it can be daunting. search for resistor then choose through hole. then use the filters for 25 ohms and 10 watts. 

or search for part # cp001025r00je14 that’s $1.93

or ohmite has one 40j25re for $2.87

there are others. through hole, wire wound, axial, 25 ohms, 10 watts 

[JKent]

i don’t see 25 ohms on the site pro linked but they do have 12.5 ohms 

you can use 2 in series to make 25 ohms. not elegant but.....

PS Thanks adams I missed the 25 ohms 

[Aadams]

The site reffed by ARPro sells the exact Dayton resistor for 2.25. Just click the link and. Scroll down the page.  

[powerglide]

1 hour ago, ar_pro said:

How about these guys?

http://www.theloudspeakerkit.com/loudspeaker-components/crossovers-components/?pgnum=4

 

28 minutes ago, Aadams said:

The site reffed by ARPro sells the exact Dayton resistor for 2.25. Just click the link and. Scroll down the page.  

 

Thanks and now sorted

I had come across these guys while hunting down the bass surrounds, but never went past that section of their site.

 

[ra.ra]

 

5 hours ago, powerglide said:

Thanks @ra.ra the schematic is invaluable...

Yes, that is a very good schematic diagram and I wish I could remember who produced it and shared it for common use. It appears to be very current, since it shows the resistor only on the mid but not on the tweeter. And while I do like those slender, robust green resistors, I neglected to mention that I think these are not available in the 25-ohm value, so I am pleased that Roy has clarified the need to adhere to this value for "original" replication. 

[powerglide]

Author is written in the title block 

MJT - 5 Jan 2018 

[powerglide]

Cabinets complete a few before and after shots 

missing veneer 

spliced in a new piece 

laquered 

Top and side wear 

after

Refoamed the woofers today, probably pretty standard around here but a first for me 

Not sure what the consensus is here on using a tone apt to check the cone alignment, I used it to double check but really not needed with these drivers 

L Pads arrived today, so just waiting on the resistors to be able to make up the crossovers and assembly the speakers for action 

 

[powerglide]

I've started the crossovers but still waiting on the resistors for the mid range.

One (only) of the mids had this resistor already fitted to the + Yellow lead running to the old potentiometer, any ideas why? I'm about to remove it, correct? 

 

 

Regards Powerglide 

[powerglide]

Hi All, 

after some clarification on the L pad resistor location in regards to the lt green wire running to the "T" terminal.

I found a photo from @JKent with has the resistor bridging the +/- from the speaker which reflects the wiring drawing, but the photo doesn't show the terminal wire connection point. The old ones are soldered together directly to the potentiometer, I'd like to use the mini female spade connectors (like Kent) but doubt I can get all wires into the fitting. @JKent how did you get around this? Not sure if I can connect on the other side of the resistor. Sorry for all the novice questions my first attempt, the bare wire in your photo 3 is coming from the capacitor?

 

I also struggle a bit with both negative wires of the mid and high, Lt green/black, running to the jumper terminal which is positive, the red wire for the woofer runs from the same jumped terminal, what am I missing? 

Any help would be greatly appreciated 

 

P.S. a pair of AR 3a's have just been posted on a local site here, they are in very good to excellent condition but asking crazy money, what is the going rate for OG's in this condition over there? 

Al

 

[ra.ra]

Your work on the cabinets looks terrific, and the re-foam appears very good, too. For comparative purposes only, I am including another good 2ax schematic with a few comments:

• this diagram was made to document earlier version with cloth woofer and phenolic tweeter
• see Note 1 - - 2ax woofer is meant to have opposite polarity from mid-tweet wiring
• see Note 3 - - it appears that someone else has encountered a series resistor on the mid (+) terminal - - this would not "increase output of tweeter", but rather would tame the midrange a bit to alter the output balance between these two smaller drivers 
• in order to avoid the tight fit of multiple wires into a female mini-spade at the L-pad, the alternate location for the resistor is to solder directly across the rear terminals on the tweeter, as was recommended in the previous post which provided the first 2ax schematic 

I'd be curious to know in greater detail what you are using to create multi-cap values of 4uF and 6uF. Also, in case I overlooked it, what material are you using for the new crossover panel that is so glossy? Thx. 

 

 

 

[powerglide]

Thanks @ra.ra so the newer paper woofers are opposite polarity also? 

I will get rid of that series resistor

The board I'm using is black acrylic 

I'll wait to see what Mr Kent says about how he ran to the terminal as I don't have the resistors yet anyway.

The Russian paper in oil capacitors are 4's and 2's they were given to me by a speaker builder who said to put the KP 1832 into the mix?, I've sent him a message to get the run down but I have found this on line which I think explains why he suggests including it. I know you guys are all about preservation of the original sound, in your opinion is it a bad idea? I will report back on what he has to say.       

By pass capacitors 

 

ERO KP1832 Polypropylene Film and Foil Capacitor
This "KP" series capacitor is a genuine film and foil capacitor, unlike the metalized polypropylene "MKP" capacitors. It's difficult to find a consistent source for these NOS capacitors, but they often turn up on eBay in small uF values and have long been considered excellent-sounding in DIY circles. Due to their small values, they are mostly used as bypass capacitors, and this is how I have tested them as well. So far, my favorite bypass capacitor has been the Russian FT-1 Teflons, which simply shines when bypassing certain capacitors, e.g. Russian "nude" K72 Teflons or Audiocap Theta. However, there are other capacitors that sound too different from FT-1 as to end up sounding incoherent when thus bypassed. This is where a nice polypropylene film and foil capacitor like KP1832 can come in handy. It lacks that slightly artificial glint metalized poly caps can impart while still extending the upper frequency and air. Its sound is quite natural and not showy at all, which may not give an ear-grabbing, exciting presentation, but it certainly does its job.

A good bypass cap applied correctly, with some luck thrown in, does not make the sound brighter like some may think, but it actually makes the lower-treble to upper-midrange area sound even smoother. It's almost as if some of the peakiness in that range moves over to the very high treble, which translates into more ambience and sense of space. I have heard similar effects with speakers when adding in a good supertweeter, not turned up too high of course.

An example of a good capacitor that benefits from a bypass capacitor like this is the Jupiter Beewax capacitor. This is a capacitor I have always liked due to its natural tone and plenty of lively treble presentation. When compared to good Teflon, it does seem a bit less ruler-flat through the upper ranges with some of the very top-end ambience muted. Bypassing the Jupiter capacitor with ERO KP1832 resulted in a more linear and smooth sound with better ambience and air, making a good capacitor even better. KP1832 is so promising as bypass, I hope to try them as coupling capacitors, but larger values do not seem easy to come by unfortunately.

[ra.ra]

1 hour ago, powerglide said:

so the newer paper woofers are opposite polarity also? 

The crossover pic you showed on p.2 of this thread is the later 2ax with the same woofer and tweeter as your speakers, and you can see that the colored wiring is consistent with these schematics - - - i.e., opposite polarity for woofer. 

Your crossover assembly work appears top-notch, but I have no experience with those particular cap components, and the issue of bypass caps will be met with equal measures of enthusiasm, skepticism, and scorn. Some will praise the resultant synergistic balance and airy brilliance; others will claim that "it can't hurt"; and still another crowd will refer to this practice as claptrap, rubbish, bunk, hogwash, poppycock, or flapdoodle.

You're having fun and doing great work and that's what matters - - - I am sure you'll get these speakers sounding as good as they are already looking. Keep it up and report back.    

[JKent]

18 hours ago, powerglide said:

I'll wait to see what Mr Kent says

UhOh, the pressure's on ?

Sorry for the delay. That photo is Roy's, not mine, but I frequently post it. And I'm sorry I don't quite understand the question but will attempt to answer.

The resistor can be attached to the driver itself,  in which case you can splice it into the green and yellow wires at any point. If they are connected with Sta-Kons you can attach the resistor to the wires as shown in the photo, where it is attached to the L-pad. Or, attach the resistor just as shown in the photo. Again, it goes between the yellow and green wires.

Just to be clear, in the photo the white thing on the left is the original pot and the silver thing on the right is the new L-pad. There was no resistor soldered to the original pot. As for the spade connector (actually a "female disconnect") the color coding (blue) indicates this size is for 16 to 14 AWG wire. The internal wiring is 18 AWG so the lead of the resistor will easily fit in there with the wire. For a single 18 ga wire, use the red Sta-Kon crimps.

"the bare wire in your photo 3 is coming from the capacitor?" I'm sorry. Don't know what photo 3 is. Don't go by Roy's photo because I think that L-pad is for an AR-3a. Looking at the schematic ra.ra provided, the green wire goes to pot terminal 2, yellow to terminal B and a lead from the 6uF cap goes to terminal 1. SO, on your L-pad, yellow + one end of the resistor goes to 1, green + the other end of the resistor goes to 2 and the 6uF cap goes to 3.

I think ra.ra covered this well.

"The Russian paper in oil capacitors are 4's and 2's they were given to me by a speaker builder who said to put the KP 1832 into the mix?"  So here's the thing: Discussing capacitors can be like discussing religion or politics. A lot of people like paper-in-oil (PIO) caps for crossovers. So far so good. Some people think adding "bypass caps" improves the sound. Some people believe in astrology. A bypass cap is a small value cap put in parallel with a larger value cap. A notorious capacitor comparison, http://www.humblehomemadehifi.com/Cap.html  praised the Vishay MKP1837 / 0,01uF MKP 100VDC for use as a bypass cap. If you have some on hand, why not? They cost about $1 each and I'll admit I've used them. BUT you absolutely do not "need" them and I doubt you would hear any difference (let the flames begin). IF you have them, go ahead. Couldn't hurt. But if you don't have them don't waste your time.

Kent

PS: Just looked at your photo of the crossover components and it looks like the bypass caps are 6200pf. That's 0.0062uF and that value is fine for bypassing.

PPS: For those interested in Russian PIO caps and vacuum tubes: https://tubes-store.com/index.php?cPath=35_41&osCsid=64sgpq54fdbq834f9qr5savhf6

[powerglide]

3 hours ago, JKent said:

Looking at the schematic ra.ra provided, the green wire goes to pot terminal 2, yellow to terminal B and a lead from the 6uF cap goes to terminal 1. SO, on your L-pad, yellow + one end of the resistor goes to 1, green + the other end of the resistor goes to 2 and the 6uF cap goes to 3.

Good morning Mr Kent, no pressure it's still about the music man.  I'm totally on board with the above configuration.

My question was not that clear, I'll try to simplify 

3 hours ago, JKent said:

The internal wiring is 18 AWG so the lead of the resistor will easily fit in there with the wire

There needs to be two 18 AWG wires connected to the female disconnect.  The second lt green wire (not pictured) running to the jumper terminal - question. Where was this connection in Roy's Photo? 

@ra.ra has enlightened and confused my task with the additional schematic.

first schematic -  green to 1 - yellow to 2

new schematic -  green to 2 - yellow to 1 (reflects Roy's photo)

My money is on the first schematic but to be sure -question. which way do I go? 

P.S. the enlightenment part was the new schematic shows the polarity of all drivers and external terminals, would be a good addition to the first schematic. 

sorry for being such a dumb ass, I am still having fun but itching to hear these at their best. 

  https://www.stereo.net.au/forums/topic/299191-fs-austic-research-ar-3a-speakers/

 

  

[JKent]

Sorry. It's been a while since I worked on 2ax's. Here are photos of some I did a while ago and you're right (now who's the dumb ass?) there are 2 wires going to the #1 L-pad terminals (corresponding to the #2 pot terminals).

The 2nd set was made up out of the box and may show things more clearly. If you absolutely don't want to solder, you could connect the 2 green wires (or 2 black) to a single wire, which would go to the L-pad.  That's what I did with the green wires going to the Mid L-pad. But if you look at the 1st photo, you'll see the ring terminal that goes to speaker terminal 1 has two 18 AWG wires.

btw, I think the confusion with the schematics is because one shows L-pads and the other shows pots. Look at Roy's photo of an L-pad. The terminals on the L-pad are marked, left to right, as 3, 2, 1. On the body of the pad he marked 1, B, 2. You can also see that on my 2nd pic below (ignore the marks on the 1st). So a pot terminal 1 is an L-pad terminal 3 and a pot terminal 2  is an L-pad terminal 1.

 

 

[RoyC]

3 hours ago, powerglide said:

There needs to be two 18 AWG wires connected to the female disconnect.  The second lt green wire (not pictured) running to the jumper terminal - question. Where was this connection in Roy's Photo? 

@ra.ra has enlightened and confused my task with the additional schematic.

first schematic -  green to 1 - yellow to 2

new schematic -  green to 2 - yellow to 1 (reflects Roy's photo)

My money is on the first schematic but to be sure -question. which way do I go?

Just catching up with CSP threads. I believe this one may have become more complicated than necessary.

To clarify some things based on my experience.

-The first schematic is not typical, whether it be accurate to the author's speakers or not. I have only seen the yellow wire connected to the AR-2ax  "B" pot terminals.

-Kent's photo of the pot and L-pad connections was only meant to show the comparison between pot and L-pad terminals. It had nothing to do with AR-2ax wire connections. The bare wire on the pot was simply a wire stripped of insulation.

-Late AR-2ax mids had a DCR of 9 ohms, not 6 ohms. During the transition, AR connected a series  3 ohm resistor to the earlier version. This mid was used in the later AR-2ax, which was equipped with the square modern-style ferrite magnet.

-I would be very suspicious of any AR-2ax schematic showing a  "+" symbol on the yellow wire side of the 2ax mid. I have checked the polarity on a number of these mids over the years and, without exception, the yellow dot side has been the negative side of the driver. Since the originating connection is to the cabinet's #1 input terminal, the mid's polarity would therefore not be connected in reverse to that of the woofer! I believe the person drawing the schematic assumed the yellow dot designated the "+" side of the mid, but did not remove the screen to check it. I have never seen reversed polarity connections for any AR-2ax. There is also frequent confusion due to AR's placement of the capacitors on the negative side of the circuit.

-When using L-pads, the 25 ohm resistor simply connects across the driver served by the L-pad. This can be done anywhere from the "1" and "2" L-pad terminals on up to the driver. Bear in mind "1" and "2" L-pad terminals correspond to "2" and "B" pot terminals.

The above considerations are much more important than very subjective tweaks such as by-pass caps, capacitor brands, etc, to 40+ year old drivers...which may or may not even be connected properly. The additional work and concern associated with these recommendations and opinions are not worth the effort (and confusion) for most people.

I see Kent posted some photos while I was typing this. Below are two more photos, showing the only 2ax crossover connections I have ever seen (note the yellow wire connections), and a meter reading of the later 2ax mid.

Roy

 

 

[powerglide]

OK, thank you brains trust, I'm all over it now! 

the biggest help is the first picture of your last post @JKent I have printed it out and can have it on the bench for reassurance.

you are right @RoyC it is very simple been made hard  

[JKent]

if you want a high resolution jpg via email send me a PM

[powerglide]

10 hours ago, RoyC said:

-The first schematic is not typical, whether it be accurate to the author's speakers or not. I have only seen the yellow wire connected to the AR-2ax  "B" pot terminals.

For clarity in the event of someone reading this in the future, I believe Both schematics are correct. One is numbered for new L Pads and one for old pots. 

[powerglide]

On 1/7/2020 at 10:13 AM, JKent said:

btw, I think the confusion with the schematics is because one shows L-pads and the other shows pots. Look at Roy's photo of an L-pad. The terminals on the L-pad are marked, left to right, as 3, 2, 1. On the body of the pad he marked 1, B, 2. You can also see that on my 2nd pic below (ignore the marks on the 1st). So a pot terminal 1 is an L-pad terminal 3 and a pot terminal 2  is an L-pad terminal 1.

Or ......... What he said ^ 

[RoyC]

On 1/7/2020 at 5:02 AM, powerglide said:

For clarity in the event of someone reading this in the future, I believe Both schematics are correct. One is numbered for new L Pads and one for old pots. 

Just a closer look at the schematics. I did overlook the fact that the first one was drawn around L-pads, not pots.

The second one, however, is incorrect in a number of ways, especially for cabinets with serial numbers in the 209,000 range.

-The "+" symbol is on the wrong side of the mid and tweeter

-There was no resistor in series with the mid until much later (and it was 3 ohms, not 2 ohms).

-The 1 3/8" phenolic dome tweeter was not original to the serial numbers, having been discontinued long before 200,000.

I suspect this person did not have original 2ax's to begin with, and was simply documenting a project. The notes regarding the "2a" (not 2ax) tweeter and the reason for the mid's series resistor (which is questionable in itself) do not suggest originality.

Roy