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The caps do not represent enough volume to be a cabinet resonance issue. As time went on AR used much smaller caps in the AR-5 as well all other models. If anything at all, you may lower fc by a tiny fraction...which is not a bad thing. When we were working on the AR-3a restoration document (in this forum's Library) we conducted many measurements relative to stuffing type and amount, with and without crossover caps present. The caps were of no significance to the bigger picture. There are more important things to expend energy on. For example, be sure to keep the fiberglass stuffing you remove from each cabinet in separate bags and keep the bags with the cabinets. Stuffing amounts are pertinent to your resonance concerns.

You should also open and clean the level controls. They will become a problem even if they seem OK now.

Take a look at the 3a restoration document in this forum's Library. The 3a and 5 are very similar, and many issues pertinent to all early AR models are discussed there.

Roy

Good to know, Roy. I have been skimming through the AR3a Restoration pdf and will treat the pots while everything is opened up.

Roger

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AMEN to that!

You obviously know what you're talking about and any questions are/will be expertly answered by Roy, but I can't resist throwing in 2 cents worth ;) :

For your 2 speakers, a good value would be ... madisounds ...

Great find and a worthy restoration.

Kent

Kent, was looking through those last night. I'll get out the weegie board and make a decision :)

Roger

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AMEN to that!

You obviously know what you're talking about and any questions are/will be expertly answered by Roy, but I can't resist throwing in 2 cents worth ;) :

For your 2 speakers, a good value would be 18 of these: http://www.madisoundspeakerstore.com/surplus-capacitors/10.0-mfd-polypropylene-cap-10mfdp/tyee/

You can bundle 7 to make 70uF. No need to add another 2uf but if you do these are OK but have only 1/2" leads: http://www.madisoundspeakerstore.com/surplus-capacitors/2.0mfd/

These are easier to work with: http://www.madisoundspeakerstore.com/carli-capacitors/carli-mylar-2.2mfd-150v/

For the 4uF and to add to your 24uF bundle, these are good: http://www.madisoundspeakerstore.com/carli-capacitors/carli-mylar-3.9-mfd/

You could also go with electrolytics for the big caps. This: http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-50-mfd-electrolytic-caps/

plus this: http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-22-mfd-electrolytic-caps/

Or, if you don't want to bundle seven 10uF caps you could use this: http://www.madisoundspeakerstore.com/solen-capacitors/solen-70-mfd-fast-cap-400v/

Great find and a worthy restoration.

Kent

Kent, you rascal, I had a feeling you would mention bundling those 10uf caps. :) As you know, I like them alot and take that route quite often. When bundling 7 of these for the 72uf AR-5 cap I would definitely add a 2 or 3uf cap to bring it closer to the 72uf spec. These caps often measure on the low side of 10uf...I've measured a few as low as 9.5uf.

A word of caution regarding new electrolytic caps, based on some recent observations. I've been finding our typically recommended electrolytic caps (Bennic, Erse, and Parts Express) to consistently measure on the high side. Some have even exceeded the advertised 10% tolerance. In fact, I recently found original caps in a pair of AR-58s and LST's (Spragues in the LST's) to measure significantly better than new electrolytic caps I have of the same stated value. My latest thinking is if one can afford film caps, go with them across the board. If cost is a consideration, it makes our bundle of Madisound surplus film caps even more attractive.

Roy

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Doesn't bundling that many caps significantly lower the ESR?

Thanks for the info on the NPEs running on the high side.

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Based on cabinet serial numbers, your 5's were probably manufactured in 1971. Dates can often be found stamped on the driver magnets. I don't know the date codes for the big block caps.

Roy

Pretty Close.

The build date for serial number range 24,000-24,400 was June-July 1972, based on the 5-Year "end-of-warranty" data. AR was building around 500-600/month during this period, as best I can tell, but production figures varied hugely depending on the time of the year, so it is difficult to pinpoint the exact build dates during some periods. Production was not yet slowing significantly for the AR-5, as this was still one of the premiere speakers in AR's lineup while still at Cambridge. When AR moved to Norwood in 1973, all of these speakers changed with regard to grill fabric, Velcro grill-frame attachment, crossover capacitors and drivers to some extent. 1975 was the last year of production for the AR-5, and this ushered in the Advanced Development Division's AR-10, AR-11, etc.

It is amazing to see the surrounds still intact—and I agree with Roy that they are original—but they look somewhat fragile. AR coated these woofers (like the AR-3a woofer and some others) with a clear butyl-latex coating, and this probably helped somewhat, but it is likely that the environment in which they were placed was a factor, as well as being away from sunlight, but you never know how long these things will last. Most woofer surrounds from that period are long gone by now.

The cabinets were originally utility cabinets built from ponderosa pine plywood, and someone put a laminate on that. During the period these were built, AR made several finishes available, such as 1) glossy walnut, 2) oiled walnut (majority built in this finish), 3) cherry, 4) oiled teak, 5) birch, 6) mahogany and 7) unfinished pine. One way to quickly identify a utility cabinet is to look at the edge along the back side: it will always be multi-ply plywood, whereas veneered cabinets (except for the very earliest AR-1s) were made from an early Nova Ply-type MDF panel. At the end of US production (Norwood) in 1975, the only finish available was oiled walnut.

—Tom Tyson

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...The build date for serial number range 24,000-24,400 was June-July 1972, based on the 5-Year "end-of-warranty" data. AR was building around 500-600/month during this period, as best I can tell, but production figures varied hugely depending on the time of the year, so it is difficult to pinpoint the exact build dates during some periods. Production was not yet slowing significantly for the AR-5, as this was still one of the premiere speakers in AR's lineup while still at Cambridge. When AR moved to Norwood in 1973, all of these speakers changed with regard to grill fabric, Velcro grill-frame attachment, crossover capacitors and drivers to some extent. 1975 was the last year of production for the AR-5, and this ushered in the Advanced Development Division's AR-10, AR-11, etc.

It is amazing to see the surrounds still intact—...

—Tom Tyson

Nice overview, Tom.

I guess photos were a little unclear about the woofer status -- one survived and is tacky -- the other was disintegrated. I've attached the missing photos below.

I would not have guessed that AR sold plain pine cabinets. From your description it sounds like this box construction is stronger than the wood veneers. They certainly have aged well.

Ordering caps today for the crossovers.

Roger

post-173498-0-02359600-1407454788_thumb.

post-173498-0-13151800-1407454799_thumb.

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...................................................... the AR-5, as this was still one of the premiere speakers in AR's lineup while still at Cambridge. When AR moved to Norwood in 1973, all of these speakers changed with regard to grill fabric, Velcro grill-frame attachment, crossover capacitors and drivers to some extent. 1975 was the last year of production for the AR-5, and this ushered in the Advanced Development Division's AR-10, AR-11, etc....................................................

—Tom Tyson

Tom,

Could you please elaborate as to the capacitors. Was there an across the board change for all speakers or a certain line. What cap(s) was being used and which brand took their place?

Thanks

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...................................................... the AR-5, as this was still one of the premiere speakers in AR's lineup while still at Cambridge. When AR moved to Norwood in 1973, all of these speakers changed with regard to grill fabric, Velcro grill-frame attachment, crossover capacitors and drivers to some extent. 1975 was the last year of production for the AR-5, and this ushered in the Advanced Development Division's AR-10, AR-11, etc....................................................

—Tom Tyson

Tom,

Could you please elaborate as to the capacitors. Was there an across the board change for all speakers or a certain line. What cap(s) was being used and which brand took their place?

Thanks

Once AR moved its facilities from Cambridge to Norwood in 1973, updates were put into place. I think that AR stopped using the plastic-encapsulated Chicago Industrial capacitors and began using more conventional tubular-shaped units from Callins, Royalitic and other brands. Roy C would probably know the specifics of these brands, as he has been into many AR speakers and rebuilt crossovers. I don't know the exact details, but it is clear that newer components were put into place as these earlier speakers were brought to Norwood, and such things as Velcro-attached grill panels, new ferrite magnets on the 10-inch woofer in place of the yoke-type Alnico magnets, and so forth.

--Tom

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OK

Thanks.

I was hoping to gain info on when Sprauge caps were phased out and what speakers and time frames they were used in.

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OK

Thanks.

I was hoping to gain info on when Sprauge caps were phased out and what speakers and time frames they were used in.

Hi David,

The Sprague caps were used in the mid 70's probably beginning in late 1972 or 1973 sometime. It may very well have coincided with the move to Norwood. Large can-type Sprague Compulytic and Industrial Condenser Royalytic caps seem to have appeared together. I have no data regarding model or serial numbers. It is not unusual to find larger value Sprague or Industrial Condenser cans in the same cabinet as the older (smaller value) Industrial Condenser block caps, so there was certainly a transitional period.

Regarding your ESR question above, it probably would be reduced. Assuming your question relates to the higher ESR of original caps, lower ESR should not be an issue with large value parallel caps. In fact, I'm not convinced it is an issue at all. When we were having caps tested by John O'Hanlon with some very sophisticated measuring equipment, he speculated that the original Sprague caps probably had ESR closer to modern film caps than inexpensive modern electrolytic caps. Given the array of caps used by AR over the years, I seriously doubt ESR was ever taken into consideration, and I'm sure it varied. I believe hobbyists today are overthinking this issue. In the same vein...I read your post in another thread. 1% tolerance Dayton caps are not necessary, as the 5% version seldom stray by more than 2%, if at all. Remember, the original caps were 10%. Save your money for something significant.

Roy

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Thanks Roy. Exactly the info I was looking for. The smaller value 1% Dayton PP caps aren't a big issue money-wise. The big cost is in the 40 and 100uF for the AR91s. However, now with the info of high readings you've seen with NPEs and no ESR issues with shunt caps I need to decide if I shell out the money for the 2 big caps in PP. It probably makes sense to go that route.

BTW, I always overthink. Its my nature and I can't change it. It can drive me crazy at times and I'm sure it does to others as well. My over analytical nature did, however, served me well managing a petrochemical processing and distillation plant.

(sorry for the hijacking)

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BTW, I always overthink. Its my nature and I can't change it. It can drive me crazy at times and I'm sure it does to others as well. My over analytical nature did, however, serve me well managing a petrochemical processing and distillation plant.

Well, that IS "significant"! :)

If you really want to lose sleep, what do you think the variances are in 30 or 40 year old drivers? Lots of variables in those old things.

It doesn't make sense to me to purchase 1% film caps and 10%+ cheap npe's for the same restoration. Otoh, the odds of actually hearing a "significant" difference between of any of them are slim.

Roy

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No need to ponder any further. Thanks to your input I'll bite the bullet on the cost and go PP for all the caps. That's what I meant about : "It probably makes sense to go that route." It does make sense!

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I am planning on working on the pots today so I slipped a mirror inside the cabinet and was able to get a date on the back of the mid-range driver -- Nov 26, 1971 -- gee, I was in boot camp, Lackland AFB on that date. I pulled the other woofer and it has Dec 22, 1971 date stamp.

Well, here is a shot of one of the pots. You can see it was rather well preserved. The oxidation was easily removed with a little Simichrome polish. I don't see any need to use anything more aggressive.

Seems like these would be more reliable if they were sealed with some tape to keep fiberglass from getting between the wiper and contact plate.

Would it be advisable to pack it with silicone dielectric grease? That would keep everything else out and prevent oxidation.

I attached some photos of the original Industrial Condenser Corp caps. The case is off the double cap. This cap had drifted high while the axial cap remained stable.

Meanwhile a friend decided I should be driving these with a period amp and gave me a Fisher Studio Standard RS-1040. I always thought the AR-5s were marginal with a 60 watt amp.

Roger

post-173498-0-75838600-1407787146_thumb.

post-173498-0-96321700-1407787157_thumb.

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Would it be advisable to pack it with silicone dielectric grease?

I don't think you want to "pack" it but yes--you could smear some dielectric grease on there. See page 14 of "Restoring the AR-3a".

-Kent

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Well, I rebuilt one crossover network today. All caps were replaced. Here is a photo before the cabinet was restuffed and woofer mounted. I kept the original look. post-173498-0-50954700-1408064507_thumb.Sounds pretty good paired off with an Ohm Walsh speaker.

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"All caps were replaced."

Huh? Certainly looks original, but where are the replacement caps?

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"All caps were replaced."

Huh? Certainly looks original, but where are the replacement caps?

Well, they are in there... :)post-173498-0-14146700-1408074189_thumb.

post-173498-0-96979100-1408077444_thumb.post-173498-0-07261600-1408077459_thumb.

I bored the axial cap and put the new one inside.post-173498-0-69125600-1408074226_thumb.

I sprayed this on the pots after removing the oxidation with Simichrome polish. post-173498-0-88880600-1408074318_thumb.

Roger

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Very cool cap installation - - - stoopid me thought you had inadvertently uploaded the "before" photo. I've seen someone else do something similar to this once, but never with so many individual components. Very clever, good work! By the way, excellent pics throughout this thread are greatly appreciated.


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Very neat installation.

Similar approach is most useful with many vintage amplifiers and tuners. Stuffing 2 or 3 electrolytics in one twist lock capacitor case makes vintage amplifier or tuner look much more original, than bundling new capacitors all over the chassis.

Best Regards

Kimmo

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AR5 should probably have been called AR2axa or AR2y. That's marketing for you. During the evolution of the AR2 series it slowly morphed into an AR3a with an AR2 woofer at which point it became AR5. The dilemma AR and everyone else faces who builds mulitway speaker systems is that loudspeaker drivers are resonant devices with a usable range of only about 2 1/2 to 3 octaves while normal human hearing is10 octaves. Something has to give and in AR's design of this era for its TOTL systems it was the match between the woofer and midrange driver. In AR3 the problem was with the woofer midrange crossover at the upper end of the woofer's range. In AR3a it was the same only the problem was with the low end of the midrange driver which had been improved over AR3. In AR2 series and AR5 it was at the lower end of the woofer's range which while remarkable for its size and cost is not nearly the equal of the AR 12" woofer. However the gain was in the woofer/midrange matchup. In some ways this makes AR5 a better speaker than AR3a at least to the way some people see it. The cost is the lower part of the lowest octave and power handling. The problem persisted until AR9 blew the whole problem out of the water with a separate lower midrange and two 12" woofers. Regrettably, at the same time AR gave in to popular market demand and compromised the dispersion of the midrange and tweeter going in the opposite direction of LST. LST was an evolutionary step up from AR3a in mid and high frequency power handling and dispersion.

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Rebuilt the second AR-5 today using the same technique only I made it a little easier on myself with the lead wires. All the caps in this one were out-of-spec on the high side.

The pots were in very good shape. Here is a photo after cleaning with Simichrome. post-173498-0-12474100-1408406844_thumb.

The original assembler must have been having a bad day because the midpoints were not set anywhere close to where they should have been. I set them at six and four ohms and reinstalled. post-173498-0-75650700-1408406856_thumb.

Another problem was the lead to the midrange driver was badly damaged when the assembler put the loop twist to take up extra slack in the wires. All but a couple of strands had been severed. Here is the finished look: post-173498-0-76699400-1408406871_thumb.

I didn't want all that great beeswax from the double caps to go to waste so I used it to fill some voids in the wood. Then I ended up doing the entire sound board as it looked very dry.

Does anyone know if it is possible to remove the pasted on serial number/directions sticker on the back without damaging it? I would like to do something to the wood but I don't want to sacrifice the label.

They sound great on organ music. There is enough bass response to vibrate the kitchen counter two rooms away and I'm sure my neighbors are enjoying it also. The mids and highs sound clean -- then again my ears are not quite what they used to be; however, I bought them in the 70's because I liked the sound and they fit my budget. At this point, I wouldn't do it any different. My father once said about them, "They sound like angels singing." Well, they were playing softly at the time :rolleyes:

Will be getting new surrounds and some new cloths for them soon. Need a badge also if anyone has a spare.

Roger

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The original assembler must have been having a bad day because the midpoints were not set anywhere close to where they should have been. I set them at six and four ohms and reinstalled. attachicon.gifAR5.140806.030.jpg

Roger

Roger,

He didn't have a bad day. :) The white dots do not represent the mid points of the level controls. The notches in the crossover board are where the pot tabs are supposed to be seated. The white dots are what AR determined to be the "normal" position for most spaces. The series and parallel resistance at the dots differs between tweeter and mid, as well as from so-equipped other AR models. It is explained very well in the AR-3a restoration guide in the Library.

Roy

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Roger,

He didn't have a bad day. :) The white dots do not represent the mid points of the level controls. The notches in the crossover board are where the pot tabs are supposed to be seated. The white dots are what AR determined to be the "normal" position for most spaces. The series and parallel resistance at the dots differs between tweeter and mid, as well as from so-equipped other AR models. It is explained very well in the AR-3a restoration guide in the Library.

Roy

Still think he had a bad day, Roy. The pots are set at 6 and 4 ohms when installed. They are locked in place with the lock nut which in the process creates the notches in the mounting board, then the knobs are set to the white dot. That's my take anyway. Not sure what kind of assembly line AR was running so there may have been more than one person involved at this level of assembly.

The only variable in this equation is the assembler, hence the "bad day" label. At any rate they are back in spec and sounding great with allowances for the ebay woofer with the wrong surround. Still a work in progress... I may take the Formica off and lay on a decent veneer :D

Roger

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Still think he had a bad day, Roy. The pots are set at 6 and 4 ohms when installed. They are locked in place with the lock nut which in the process creates the notches in the mounting board, then the knobs are set to the white dot.

Roger

No...the notches were already stamped in place before assembly. The white dot setting is supposed to be 6 ohms (series) for the AR-5 mid, and the tweeter dot is less. The result is the pointers of the mid and tweeter knobs are in different places when set to maximum if they were installed properly.

Roy

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