Help Restoring My AR-3a's

[Edward]

I have a pair of AR3s and it is high time to replace the caps and pots. One of the woofers also buzzes (and surrounds have disintegrated) so I will re-cone woofers and replace pots soon, but first the Xover. 

I would like some feedback on the replacement parts for the Xover that I have chosen.  Below I have listed the parameters for both the original caps and the replacement ones that I'm planning on purchasing.

Referring to the cap replacement information, I read somewhere that it is important to match closely the mF number, but the V can be higher if you cannot find an exact match.

I inspected the inside of the potentiometers and it looks as though they just need a very thorough cleaning.

Thanks ahead of time for feedback from more experienced individuals than myself.

Edited December 30, 2019 by Edward
Orig post had just too much information - not concise.

[Edward]

To all AR Guru's,

For my AR3 woofers it is time to replace the foam surrounds once again, is there a cloth surround alternative in lieu of the typical foam that seems to be the standard material.  It seems there must be a better alternative that would last longer and be compatible with the designed sonic characteristics.

Edward

[Aadams]

6 hours ago, Edward said:

For my AR3 woofers it

Edward

Your topic title is AR3a but you mention AR3 woofers.  If your woofer was originally foam then foam would be the replacement to maintain correct performance.  Your parts list for new NPE caps is good but one recommendation is to use three 50mf instead of a single 150 for the woofer.  I think the reason is the smaller value caps in that line have lower variance from spec. 

I was a pot holdout but I am now an LPad convert.  You will be better served by replacing the pots with lpads and resistors.  The 25ohm 10 watt resistor is mandatory on the mid range lpad but only recommended for the tweeter if you have the tweeter rebuilt or replaced with a HiVi QR mod.

It would help if you post pictures of fronts and backs showing drivers and serial nos as well as interior images of the crossovers so those with more knowledge might have extra helpful tidbits in case you have a model with transitional variations in manufacture.  For example I can't remember seeing a 3a with a mix of Spragues and Royalitics. 

Adams

  

[Edward]

 

I appreciate your knowledgeable input.  I'm looking at my Xover and there is an AR sticker for AR-3a (#101822, 101829).  I'm no longer unsure of what I own.  Thanks for confirming my parts list.  I'll check PartsExpress for the two 25 ohm 10 watt resistors that I will need.  I'll also check back posts for recommended lpads.

a) OK foam surrounds it is, b) to my grocery list I'll add (4) lpads, (2) 25 ohm 10 watt resistor for mid-range lpad connection, & (6) 50mf caps (instead of one 150 for each woofer).

I was able to photograph my Xover because it has been removed and on my desk. I hope the pic uploads smoothly.

I purchased my AR3 pair from my high school girl friends father for $200 back in about 1976. I knew it was a steal and a dream come true back then.  I was the odd man out because all my friends were buying R&R Cerwin Vegas for Led Zeppelin.  Her dad was the original owner and provided me with the original receipts.  I have hauled them around; college, apts., move from Chicago to So. CA, more apts, to my current home in San Diego.  The cabinets are in great shape.  I have thrown out my back on several moves - I would not anyone else carry them, not that anyone was eager to do so (!).  They are usually hooked up to my Sony separates; TA-2000 pre amp & TA-3120 power amp (50 wpc, but this number is very conservative). This has been my system for over 4 decades.  I love it.

I'll post pics of my drivers after I remove them again.

Your guidance is extremely helpful and appreciated.  Ed

Edited December 31, 2019 by Edward
fixed grammer

[Aadams]

Edward

Those look like 3a crossovers but different from what I have seen. Can you please supply a picture of the front of the speaker cabinet showing driver faces.  Also what are the serial numbers on the cabinets?  Do you know the dates on the original purchase receipts?  Does the receipt say which speaker was purchased? 3 or 3a?  Pardon the questions, this isn't idle curiosity. There are others here more expert and supplying the requested info can get you sorted out quicker.

Also the Parts Express resistor is a low inductance 1%. They no longer stock the 5% version.  

Also, even if they are working, your tweeters are severely degraded in performance compared to when you purchased them.  Now may be the time to consider having them rebuilt in which case you will need a resistor for the tweeter lpad.

Photos will help.

Adams

[Edward]

 

Adams,

AR-3a was written on original receipt with a sale date of 19 Dec 1975.  The AR manual provided also states AR-3a. Cabinet serial #s ( next to knobs on Xover board) are 101822, 101829 for "AR-3a".

Once the Xover is restored with previously discussed caps and the woofer foam surrounds replaced, I will audition the sound, prior to having tweeters rebuilt.  However, I do plan on having tweeters rebuilt, based on your recommendation, prior to sitting back and enjoying Frank Zappa, Herbie Hancock, Beatles, Dave Brubeck, Beck, Stanley Clarke, Switched-On-Back, Hendrix, Miles Davis, etc. ...

At one time I had purchased a pair of JBL 100s (with waffle grills) and did not feel they could even compare to the AR3a's.  The flat response and clean bass of these magnificent AR3a speakers provides a unique settling listening experience.  Looking forward to bringing them back to former glory.

Pictures below - the wide thin round foam previously surrounding the tweeter flaked off.

Thanks for your guidance, EE

 

[Aadams]

Those are nice really late model 3as.  If both of your tweeters are identical they do not need rebuilding, if they are working.  They appear to be the robust tweeter used in the early AR11 which means you may need a resistor on the tweeter lpad. It also may explain why the crossover appears a little different.

I think you are good to go except for definite advice on the tweeter resistor which should come from RoyC in the next day or so.  

Adams

[JKent]

I see you decided to use a film cap for the 6uF. The Solen is a fine choice, you could also use this Dayton

https://www.parts-express.com/dayton-audio-dmpc-62-62uf-250v-polypropylene-capacitor--027-427

[lARrybody]

24 minutes ago, Aadams said:

Those are nice really late model 3as.  If both of your tweeters are identical they do not need rebuilding, if they are working.  They appear to be the robust tweeter used in the early AR11 which means you may need a resistor on the tweeter lpad. It also may explain why the crossover appears a little different.

Those are some nice looking late model AR3a's. Here are my newest manufactured AR3a. The serial number is about 25 thousand earlier than yours. I think they are from 1973-74. 

 

Your tweeters and midranges being backwired must be from 1975-76, about the time AR was transitioning to the AR11, which used those drivers. I would definitely download the AR3a restoration manual and make sure you get the correct foam surrounds. Look at Vintage AR and loonytunes2001 (Rick Cobb) on ebay listings to get those. 

Before Stimpy recommends the same thing  JKent  has recommended I will also put my vote in for a 6 uf Metalized Polypropylene  Capacitor in the tweeter circuit. 

Basically new woofer foam, a few caps and some L-pads will have them singing for many more years.

[Edward]

1 hour ago, JKent said:

I see you decided to use a film cap for the 6uF. The Solen is a fine choice, you could also use this Dayton

https://www.parts-express.com/dayton-audio-dmpc-62-62uf-250v-polypropylene-capacitor--027-427

I'm going with the film caps based on what I have read in previous posts on the AR Restoration Forum, or maybe in the detailed in the, Champagne, Kantor, Luong, O’Hanlon, Thiel, Tyson (2007) Restoring the AR-3a Guide.

What artists do you play through your AR-3a s.

Thanks for your input JKent

[Edward]

1 hour ago, JKent said:

I see you decided to use a film cap for the 6uF. The Solen is a fine choice, you could also use this Dayton

https://www.parts-express.com/dayton-audio-dmpc-62-62uf-250v-polypropylene-capacitor--027-427

If Solens not in stock when checking stock I'll also consider the Daytons.

Thanks Kent

Edited December 31, 2019 by Edward

[RoyC]

This pair is a good example of the late production AR-3a...back-wired tweeter and mid, small and large Industrial Condenser capacitors along with the Sprague capacitor, and a sandcast resistor instead of the usual nichrome resistor wire in the midrange circuit.  (For those of you wringing your hands over level control power ratings, note the 5 watt rating of the resistor. :))

The tweeters are of the later type original to the AR-11/10pi models and are not original to any iteration of the 3a, so these would be later replacements. If they were replaced by a factory service shop, the tweeters should have a 3.3 uf cap in series with their negative terminal. This would adjust the tweeter's response to that of the original tweeter by placing the 3uf cap in series with the original 6uf cap, resulting in a capacitance value of 2uf. In other words the original 6uf capacitor value for the tweeter circuit is not appropriate for these tweeters IF the goal is to replicate the response of the AR-3a. (On the other hand, I'm sure there are many who would not mind the AR-11 tweeters as a drop in replacement, as is.)

Roy

[Edward]

Roy,

Holy mackerel you are correct.  When I listened to them at the home of the seller I tested them toughly and discovered that the tweeters were blown. However, since the original sales receipt was available, and they were still under warranty, I took them down to have repaired by factory authorized service shop. I only paid $200 (which I knew was a deal) for the pair in about 1976-ish.  So it appears that the tweets were replaced with an upgraded model, with further required modifications not made to correct responce.  I need to replace high caps with "3.3 uf cap in series with their negative terminal" (RoyC).  I was looking at the pictures in the "Restoration Guide" and the details provided for the drivers and was thinking that the tweeters info need to be adjusted to include the 1975 date of my speakers, but the tweeters in my speakers are not the original models.  That clears that up -- restoration guide correct.  Man-oh-man you guys are good.

[Aadams]

1 hour ago, RoyC said:

3uf cap in series with the original 6uf cap,

"3uf cap in series with the original 6uf cap"

"So it appears that the tweets were replaced with an upgraded model"

I wouldn't say upgraded just more robust.

Edward

Don't forget to ask about the tweeter lpad resistor if you are keeping these tweeters.

[RoyC]

1 hour ago, Edward said:

Roy,

I need to replace high caps with "3.3 uf cap in series with their negative terminal" (RoyC).  I was looking at the pictures in the "Restoration Guide" and the details provided for the drivers and was thinking that the tweeters info need to be adjusted to include the 1975 date of my speakers, but the tweeters in my speakers are not the original models.  That clears that up -- restoration guide correct.  Man-oh-man you guys are good.

"Forum, or maybe in the detailed in the, Champagne, Kantor, Luong, O’Hanlon, Thiel, Tyson (2007) Restoring the AR-3a Guide."

Edward,

The "C" is the first initial of my last name , which is "Champagne".  I know 3a's better than my own name.

Roy

[Edward]

40 minutes ago, Aadams said:

"3uf cap in series with the original 6uf cap"

"So it appears that the tweets were replaced with an upgraded model"

I wouldn't say upgraded just more robust.

Edward

Don't forget to ask about the tweeter lpad resistor if you are keeping these tweeters.

Aadams and others,

On that same note. So I would add a new 3uF cap in series with a NEW 6uf cap?  Or do I add a new 3uf cap in series with the ORIGINAL cap. that is presumably in need of replacement?

Also a follow up to RoyC's comment rearguarding replacement tweeters: following the figures in Champagne et al. 2007, the originals were most likely 200013-1s (for AR-3a, AR-LST) as seen in Fig. A.20, (dates 1974-1975; pg. 31), with 1200011-1s (for AR-10 π , AR-1) installed as replacements (Fig. A.24, dates 1977-1978; pg. 32; 1200011-1).  It is all making sense to me now.  The speakers were purchased by original owner on 19 Dec 1975 (on receipt) and I must have bought them sometime in 78 with blown tweeters. Under warranty I had the tweeters repaired free of charge upon purchasing them.  The replacement components had that same thin wide foam with a circle painted on it prior to it dissolving into powder.

[Aadams]

Edward

Does the black wire running from your tweeter pot have a 3.3 cap spliced near the end?  if not remove a tweeter and look on the backside negative terminal or the connecting wire. If no cap found it probably wasn’t installed. 

[Edward]

Aadams,

Not installed. Appears to have been a quick repair with, at the time, contemporary tweeters.

 

To all,

Any telling if myAR-3a's, with the later version tweeters and swap of pots for lpads, will be viewed by the  "Help Restoring My AR-3a"  group as "Frankenar's" (Frankenstein + AR's)?  Or is vintage AR tweaking typical/accepted as necessary modifications (caps, lpads)? The difference is that my pair will also contain relatively newer version of tweeters (by 2-3 years).

[Aadams]

16 minutes ago, Edward said:

Any telling if myAR-3a's, with the later version tweeters and swap of pots for lpads, will be viewed by the  "Help Restoring My AR-3a"  group as "Frankenar's" (Frankenstein + AR's)?  Or is vintage AR tweaking typical/accepted as necessary modifications (caps, lpads)? The difference is that my pair will also contain relatively newer version of tweeters (by 2-3 years).

Lpads, properly setup,  are a well accepted tweak and way better than the best used 40 year old pots.  The tweeter is not a problem either, cap or no cap, as long as you don't mod the internals to compensate.  The new 6 mf cap gets placed on the board but the additional 3.3  is placed in line with the negative terminal wire and connected to the the tweeter so the mod comes out easily if you ever install rebuilt original tweeters.   You would have to know what to listen for to ever the difference.

PS Don't forget to ask about that lpad resistor.

Aadams

[lARrybody]

Not even FrankenAR. Now replace your woofer with Radio Shack woofers and your tweeters with Peerless soft domes then maybe. You want to install new L-pads because the original aetna-pollak pots are past their life expectancy. Your 20001-1 tweeters are ferro -fluid and will handle more power.  Just do the crossover mods. If you must have the original 3/4 in. hard dome tweeters they can be found and rebuilt by either RoyC or Chris1 to like new condition. 

[RoyC]

1 hour ago, Edward said:

To all,

Any telling if myAR-3a's, with the later version tweeters and swap of pots for lpads, will be viewed by the  "Help Restoring My AR-3a"  group as "Frankenar's" (Frankenstein + AR's)?  Or is vintage AR tweaking typical/accepted as necessary modifications (caps, lpads)? The difference is that my pair will also contain relatively newer version of tweeters (by 2-3 years).

As official spokesman for the " "Help Restoring My AR-3a group", the L-pads are fine with the 25 ohm parallel ohm resistor on the mid, and a 2uf capacitor on your AR-11 tweeters.

Roy

[JKent]

So there you have it. Forget the 6uF caps and install 2uF in their place. Solen and Dayton 2.0uF caps are available from PE. They are so cheap I'd go for the 1% tolerance but even the 5% are probably spot on

https://www.parts-express.com/cat/metalized-polypropylene-crossover-capacitors/294?N=22074+4294967118+4294962702&Ne=10166&Nrpp=99999&Nrs=collection()%2Frecord[endeca%3Amatches(.%2C"P_PortalID"%2C"1")+and+endeca%3Amatches(.%2C"P_Searchable"%2C"1")]&PortalID=1

[Edward]

4 minutes ago, Aadams said:

Lpads, properly setup,  are a well accepted tweak and way better than the best used 40 year old pots.  The tweeter is not a problem either, cap or no cap, as long as you don't mod the internals to compensate.  The new 6 mf cap gets placed on the board but the additional 3.3  is placed in line with the negative terminal wire and connected to the the tweeter so the mod comes out easily if you ever install rebuilt original tweeters.   You would have to know what to listen for to ever the difference.

PS Don't forget to ask about that lpad resistor.

Aadams

That is what I'm gathering -- more about keeping the vintage usable in the 21th century -- so no unnecessary mods to internals.

Pots out and replace with lpads. And I guess now I'm conceptualizing the changes to account for my replacement tweeters; change cap as prev discussed (6mf on board), and insert the 3.3 resistor in series with negative terminal. I was a little slow picturing this arrangement.

Other caps: The interesting thing is that the caps in my 1970s Sony separates are old as well.  Our local Classic Audio Repair shop scoped my amp and found the original Elna caps were generally still OK.  He was a bit surprised but stated that Sony used quality parts in their assembly of this audio series.  However, two caps on the power supply board of preamp were faulty and were replaced.  They provide old parts in a bag upon pickup.  The set sounds great to my ears, albeit with my back-up two-way ported speakers.  My point is that after the caps on the AR board, I will still have aging Elna caps in my electronics.

Music source:  My source is a CD player. Over the course of about one year I traded in my collection of rock/pop/jazz/classical vinyl at ~6 wooden crates.  The local record shops were relativity generous when trading in for in-store credit.  I love the wide frequency range of compact discs as opposed to the compressed vinyl format and no pops or clicks !!!  I do not stream music, too compressed for me.

[lakecat]

Don't be so quick to throw away those pots. There is a double swipe in those later models...and have found them to be in pretty good shape. You have some of the last built speakers with those serial numbers.

[Edward]

24 minutes ago, JKent said:

So there you have it. Forget the 6uF caps and install 2uF in their place. Solen and Dayton 2.0uF caps are available from PE. They are so cheap I'd go for the 1% tolerance but even the 5% are probably spot on

https://www.parts-express.com/cat/metalized-polypropylene-crossover-capacitors/294?N=22074+4294967118+4294962702&Ne=10166&Nrpp=99999&Nrs=collection()%2Frecord[endeca%3Amatches(.%2C"P_PortalID"%2C"1")+and+endeca%3Amatches(.%2C"P_Searchable"%2C"1")]&PortalID=1

Thanks for the link to PE:  027-214,  Dayton Audio, 2.0 µF, 1%, 250V.

I still need to summarize this info, so my PE order includes all the changes/additions (resistor) that have been discussed today.

You guys ROCK !!!   Thanks for taking the time to guide me back to my previous world of a flat audio response.