Jump to content

AR 5 Crossover Schematic


Guest jbwebs

Recommended Posts

The AR-5 caps are 4uf (in series with the tweeter), 24uf (in series with the midrange) and 72uf (in parallel with the woofer).

The 17 ga. inductors are AR #2(.16mh), #10(3.83mh) and #11(2.3mh).

The resistor wire is 1.4ohms.

Check out the AR-3a schematics in the library. The AR-5 crossover layout is the same.

Make sure to clean those level controls while you are in there.

Roy

Link to comment
Share on other sites

Guest jbwebs

Thanks a bunch. I have already replaced the level controls with new ones. My pair of 5s is sequentially serial numbered, have new woofer surrounds, and the walnut veneer cabs have been refinished. I also have a set of the original "cross" stands. I bought a pair new back in 1968 and loved them then. Nostalgic to have another pair now. I am replacing the tweeter and midrange caps because they have changed value and are letting lower freqs get into the mids and tweeters. Anyway, thanks again.

Link to comment
Share on other sites

Guest jbwebs

Sorry to be a pest. Are the level controls in the AR5 16 ohm like the 3A or are they supposed to be 8 ohm? Also, I can't tell from the 3A crossover schematic which coil is which. Can you help me there? Thanks.

Joe

Link to comment
Share on other sites

  • 8 years later...

I have a pair of AR-5s from 1989 that had been working fine. I bought them on that auction site about three years to substitute for an old pair I had that I had gotten directly from AR back in the 1970s that need to have their woofer surrounds replaced. (I know, surround kits are also available on that same auction site.)

The problem with the pair that I am using now is that one of the mid-range speakers is not producing any output. The woofer and tweeter are indeed putting out, but not the mid-range. I have twisted the mid-range pot back and forth with no results. I have checked the mid-range speaker itself and its corresponding pot and both are working okay. I checked the chokes that deal with the mid-range and tweeter and they are okay too. I only took the mid-range speaker out of the cabinet to check it and used the resulting hole to check the crossover as best as I could. All of the components that I could check except for the capacitors were okay. So, further theories would indicate that the inline capacitor is bad, but I have not been able to figure out from the AR-5 and AR-3a schematics what may be going on. The crossover network does not seem to jive with the schematics. Any thoughts before I take all of the speakers and the insulation out (again!) to try and figure out this crossover network.

Bill

Link to comment
Share on other sites

Hi Jazz Guy, and welcome to CSP.

What you've described is a little confusing - - - to me, at least - - - first you say the mid pot control has no effect, then you go on to say that the mid and its corresponding pot are both functioning properly, so it is not entirely clear which components are working and which are not. You say you have "checked" various components, but how have they been tested or measured for functionality?

With a little bit more information provided by you about this pair of speakers (pics are always extremely helpful), I am sure you will get the helpful responses you need. Are the caps original? Have the pots ever been inspected, cleaned and measured? Also, I think it would be difficult to really assess the condition of the crossover parts by peeking in thru the small-ish midrange cut-out. Woofer hole always provides far better access.

For what it's worth, attached is an AR-5 schematic drawing.

post-112624-0-76706800-1399908315_thumb.

Link to comment
Share on other sites

Well, what I said may have been confusing. I left out some of my steps, that I thought would be implied.

I put a 1.5 volt battery across the mid-range speaker and it gives a very audible click, so it appears to be okay. The pot continuity was checked with an ohm meter, but I do not remember its value. So, I do not know whether it is an 8 ohm or 16 ohm pot. I checked the chokes with the ohm meter and they are okay. The mid-range capacitor could be a problem. It is small and has an unreadable label. So, I do not know its value, but it seems to be too small to be rated for 50 volts.

I am thinking about replacing all of the caps with Dayton Audio PMPC audio capacitors because one of them looks like it was installed when the cabinet was built. I do not have a good piece of test equipment for checking caps, except the ohm meter to check as to whether the capacitors are shorted or not. So replacing them all would seem to be the best practice.

Ra.ra: Some things you are suggesting are very sound. So, I will go back and remove the woofer and mid-range for better access, and try to take some pictures. The pots have not been cleaned, but were changed when the speaker was rebuild some years ago. I will re-check their condition and values. Thank you for the AR-5 schematic. I looked at your schematic and I see I may have additional problems: Your schematic show one resistor. My setup has two: A white ceramic resistor and a nichrome wire resistor. The wire resistor looks original. It looks like I will need to draw a new schematic when I take the speaker cabinet apart. Fun, fun, fun.

Soundminded: That is a good suggestion that I will try before I remove the woofer. I know that the pots are a common source of problems for AR speakers.

Link to comment
Share on other sites

Very same results, but here is the AR-5 schematic found in the CSP library (I just find the other diagram a bit easier to follow), and both of these have the same info that Roy noted in text of post #3. The only minor difference is resistor value (1.3, 1.35, or 1.4 ohm?) and I'll leave it to someone else to comment on any differences between these values. Since your speakers have already had some restoration work performed, then definitely post some pics and you'll most likely receive very specific feedback about what's needed to get these speakers back in tip-top shape. Those pot sweeps should provide readings somewhere near a range from 0 to 16 ohms.

FWIW, I happen to think Dayton caps offer excellent performance and a good value, but I'd be just as satisfied with the 5% tolerance DMPC versions for the tweet and mid, and maybe even use lower-priced electrolytics for Mr. Woofer. All of the more common brands are good, but the prices vary quite a bit.

http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/ar-5_schematic.pdf

Oops, I just noticed that Carl's schematic from the library notes a ceramic magnet woofer, and I am not familiar enough with the AR-5 to know if it was ever produced with the alnico magnet on the 10" foam woofer (like in my AR-2ax speakers) and if so, that might have necessitated a small tweak in the crossover circuit. Others will know better than me.

Link to comment
Share on other sites

AR-5 info:

-The pots are the same 16 ohm potentiometers found in all models of that era.

-Most, if not all, AR-5's used woofers with alnico magnets. If woofers with ceramic magnets are found, they are either later replacement drivers, or (possibly) very late production 5's. Most AR-5's used the same foam surround woofer used in the 2ax. Very early AR-5's had woofers unique to that model.

-The resistor in the midrange circuit is supposed to be 1.5 ohms. Other values posted in the past were based on measurements. An "official" AR schematic was found clarifying the issue (see attached).

-There was a change in the AR-5 crossover, which replaced the earler #6 (1.37mh) and #8 (3.00mh) coils with #11 (2.3mh) and #10 (3.8mh) coils. (Similar changes were made in other AR models around 1970.)

Roy

AR-5 schematic (from AR).pdf

Link to comment
Share on other sites

-There was a change in the AR-5 crossover, which replaced the earler #6 (1.37mh) and #8 (3.00mh) coils with #11 (2.3mh) and #10 (3.8mh) coils. (Similar changes were made in other AR models around 1970.)

Roy

This corresponded to the change in the published crossover frequency specifications for the 3a and 5 from 575 to 525 and 650 to 550 Hz respectively. I don't believe that AR actually published the spec change in their lit until around 1974, in that blue fold-out brochure. So if the actual production change took place in 1970 as Roy says, then AR's crack Marketing Department waited 4 years before they finally realized the published specs were wrong.

The 10" LST/2 started out with an erroneous published crossover spec of "525 Hz," which, of course, is the 12" x-o spec. Then, later lit changed the LST/2 to 650--still wrong, because at the time, the 5 was being spec'd at 550. The LST/2 was intro'd and made during the timeframe when the 5's x-o had already changed to 550, so there is no way any LST/2 had a woofer-to-mid x-o of "650 Hz."

The LST was intro'd with a published x-o spec of 575, but at the time of its intro in late 1971, the 3a was either being changed or about to be changed from 575 to 525. The lit for the LST changed shortly thereafter from 575 to 525, but it's not clear to me whether the change was just to accurately reflect what it had been all along (525), or if the LST did actually undergo a physical x-o modification shortly after its intro.

Steve F.

Link to comment
Share on other sites

So, is this another mystery with the history?

In both 20-page AR product catalogs that I have - - - Feb '71 (orange) and June '72 (blue), neither included here but each showing Cambridge address, each lists the AR-5 woof-to-mid x-o frequency as 650 Hz, as Steve has noted. And by Oct '74, the blue brochure (first pic) had revised this to be published as 550 Hz, just as it had in an earlier publication from Nov '73 (second pic, AR loudspeaker manual, 4 pages), both with Norwood address. One other publication, date unknown but with Norwood address, notes this frequency as 650 Hz (third pic attached).

This timeline sort of suggests to me that possibly the original specs for the AR-5 were maintained until after production had moved to Norwood, where design/production revisions were later implemented with the change of coils. Could this scenario also have possibly coincided with a switch from the alnico to ceramic magnet woofer?

post-112624-0-09960200-1400267276_thumb. post-112624-0-58324800-1400267750_thumb. post-112624-0-95651400-1400268408_thumb.

Link to comment
Share on other sites

As Roy has noted (and that also coincides with my recollection), the AR-5 never had an Alnico magnet woofer. When the AR-5 was intro'd in late '68, it was a brand-new woofer (different from the then-"old" 2ax), with the industry's first foam surround. AR heralded the foam surround as being very advanced.

The 2ax changed to the 5's woofer when the 2ax went "new" in 1970, which was before they went to Norwood. "New" 2ax's--with the 5's foam surround woofer and the 5's 8-ohm 3/4" hard-paper dome tweeter--were being made in Cambridge in 1970. I bought a pair of "new" 2ax's in Feb 1971 that were Cambridge-made. (I gave these to Tom T for his collection. The cabs, grilles, logos, and back-panel papers are pristine, and they've never been opened. They need new foam and the pots need cleaning, of course.)

So whatever the reason/timing for the 3a/5 x-o changes, I don't think they were because of the Cambridge-to-Norwood move.

I've been on the "inside" of some major US speaker manufacturers as Head of Product Development, directing eng/development/purchasing and marketing activities. From my experience on both sides of the fence ("outside" enthusiast vs. "inside" speaker co. employee), we enthusiasts give these spec details far, far more attention than the companies do themselves.

I always paid close attention to the published specs, but I can see how easy it is to let those details slip, because in the end, no one is going to buy or not buy your product because the x-o is 550 or 650.

Steve F.

Link to comment
Share on other sites

I very much agree, and will also personally attest, that I have never purchased any speaker product based on its published crossover frequency, but I most certainly cannot agree that it is "easy ... to let those details slip". Details are indeed what make a particular product attractive to discriminating consumers, and (good) details are what makes a product stand above its competition. Perhaps that laxness was overlooked within globally-respected speaker companies, but I can state with certainty that similar practice is not tolerated in all industries. I think I understand pretty well what early-70's Cambridge might have been like, but this laissez-faire response begs the question: exactly what were the AR proofreaders smoking if they let this sort of inaccurate copy pass their desks en route to the printer?

Nonetheless, my previous post was merely attempting to establish a hypothetical timeline based on widely available documents produced by Acoustic Research, and the Cambridge-Norwood move just happened to possibly fit that hypothesis, at least regarding dates of their published material. I certainly do not have enough hands-on experience with the AR-5 to challenge the accuracy of these published documents.

Steve, my reading of Roy's comment in post #11 was 180 degrees from yours - - I heard him say that most, if not all, AR-5 woofers did employ the alnico magnet. My woofer magnet comment at the end of post #10 was made simply because I noticed that Carl's schematic explicitly referred to this particular woofer for the making of his diagram, and it occurred to me that this change (alnico to ceramic) may have been the reason for the later revision to the crossover assembly (i.e. revised coils).

Link to comment
Share on other sites

You're right--I misread Roy's Alnico comment. That does put things in a different light.

It still doesn't alter the unfortunate fact that AR waited too long to change the published x-o specs to agree with what was being produced.

Re those printed details, very often, "junior" marketing people do the so-called proofing and they're not necessarily privy to the current eng details. They're just going on what's available to them, and Joe the Head Engineer probably never even spoke to Jimmy the Summer Intern.

That's just how it is in many companies, in virtually any industry.

Steve F.

Link to comment
Share on other sites

  • 4 months later...

...

Nonetheless, my previous post was merely attempting to establish a hypothetical timeline based on widely available documents produced by Acoustic Research, and the Cambridge-Norwood move just happened to possibly fit that hypothesis, at least regarding dates of their published material. I certainly do not have enough hands-on experience with the AR-5 to challenge the accuracy of these published documents.

Steve, my reading of Roy's comment in post #11 was 180 degrees from yours - - I heard him say that most, if not all, AR-5 woofers did employ the alnico magnet. My woofer magnet comment at the end of post #10 was made simply because I noticed that Carl's schematic explicitly referred to this particular woofer for the making of his diagram, and it occurred to me that this change (alnico to ceramic) may have been the reason for the later revision to the crossover assembly (i.e. revised coils).

A little more input here since I have Jan70 and Jun72 dated pairs of Ar-5s -- about 13,000 units were produced in this period judging by the serial numbers. The Jan70 pair has the old crossover with the #6 and #8 coils and the Jun72 pair has the #10 and #11 coils. I was a little hasty pulling these apart but I think one of the midranges was wired with reverse polarity which seemed strange and I wish I had taken more time to photograph.

I couldn't find the date of the Norwood move but am presuming it was 1973.

Roger

Link to comment
Share on other sites

AR-5 info:

-The pots are the same 16 ohm potentiometers found in all models of that era.

-Most, if not all, AR-5's used woofers with alnico magnets. If woofers with ceramic magnets are found, they are either later replacement drivers, or (possibly) very late production 5's. Most AR-5's used the same foam surround woofer used in the 2ax. Very early AR-5's had woofers unique to that model.

-The resistor in the midrange circuit is supposed to be 1.5 ohms. Other values posted in the past were based on measurements. An "official" AR schematic was found clarifying the issue (see attached).

-There was a change in the AR-5 crossover, which replaced the earler #6 (1.37mh) and #8 (3.00mh) coils with #11 (2.3mh) and #10 (3.8mh) coils. (Similar changes were made in other AR models around 1970.)

Roy

Roy is right here regarding the level controls, and all were 16-ohm wire-wound Aetna Pollock units dating from about 1959 or so, with some of the late-1960 versions having increased spring tension to offset the "dropout" problems that plagued this level control. Nevertheless, the controls work exactly as intended when they are working properly and are best left in place or refurbished.

All AR-5s dating from October 1968 until mid-1973 had the yoke-type Alnico-5 magnet assembly; after the move to Norwood and after the supplies were depleted, AR went to the universal 10-inch woofer for the AR-5. The very first AR-5 woofers were the best, and these woofers are characterized by the yoke magnet and the dome-shaped cloth dust cap. This woofer also had the best cone material (with the flattest response) of any of the early 10-inch woofers in that the cone was a special formulation of pulp-paper and asphalt that insured a very uniform response up to the 650 Hz crossover, and this woofer was one of the first -- if not the very first -- woofer with a urethane-polymer foam surround, the nemesis of all speaker hobbyists today. This specific woofer was not used in the AR-2ax, but the traditional yoke-magnet, stamped-basket AR-2ax (four-bolt) woofers were used in AR-5s for several years before the operation was moved to Norwood. In fact, most AR-5s have the AR-2ax-type yoke woofers.

In 1973 AR began using the ferrite-magnet woofers in both the 8-inch and 10-inch speakers, and these woofers were good, reliable performers, but not as smooth as the earliest versions. They had somewhat more rugged construction and slightly higher sensitivity than the yoke woofers. One note, too: yoke woofers are susceptible to demagnetization if excessive, prolonged high-amplifier power is applied to the speaker. The voice coil rests against the magnet and high current can demagnetize these magnets somewhat. This does not occur with standard flat or ring-type magnets.

Attached file shows the original and AR-2ax-style later woofers used with the AR-5.

--Tom Tyson

post-100160-0-96851700-1411832338_thumb.

post-100160-0-44369000-1411832941_thumb.

Link to comment
Share on other sites

Dear All

Ref alnico woofers in the AR-5

For the speakers produced/delivered in Europe, the alnico woofer was quite common in the AR-5 and in the AR-2ax as well, I have enclosed pictures of the two alnico woofers I took out of my AR-LST-2, I have no idea, what the difference is between the two, except the label. :)

BRgds Klaus

Edit: I got alnico and ceramic mixed up, see later post with correct info on alnico woofers and AR-5

post-101646-0-16039200-1411982262_thumb.

post-101646-0-29026300-1411982281_thumb.

Link to comment
Share on other sites

Dear All

Ref alnico woofers in the AR-5

For the speakers produced/delivered in Europe, the alnico woofer was quite common in the AR-5 and in the AR-2ax as well, I have enclosed pictures of the two alnico woofers I took out of my AR-LST-2, I have no idea, what the difference is between the two, except the label. :)

BRgds Klaus

Klaus,

I believe these are the more common alnico AR-5 woofers in the US. post-173498-0-14311000-1412008865_thumb.

Roger

Link to comment
Share on other sites

Sorry for screwing up the discussion with confusing info, yes my pictures are of ceramic woofers, must have been a Transitoric Ischaemic Attack of the brain :unsure: .

Nevertheless, I have a set of AR-5 with alnico woofers originally installed, they are US made (bought on the Thule Airbase on Greenland) bought by me from the original owner and serial number on one of the speakers read 000788, so a quite an early set of AR-5 speakers.

Edit: Came to think of another set of AR-5 I had in for woofer surround repair, also alnico woofers; I did not make a note of the serial number, but they were US version cabinets.

BRgds Klaus

post-101646-0-90107200-1412193121_thumb.

Woofers from my AR-5

Link to comment
Share on other sites

Sorry for screwing up the discussion with confusing info, yes my pictures are of ceramic woofers, must have been a Transitoric Ischaemic Attack of the brain :unsure: .

Nevertheless, I have a set of AR-5 with alnico woofers originally installed, they are US made (bought on the Thule Airbase on Greenland) bought by me from the original owner and serial number on one of the speakers read 000788, so a quite an early set of AR-5 speakers.

Edit: Came to think of another set of AR-5 I had in for woofer surround repair, also alnico woofers; I did not make a note of the serial number, but they were US version cabinets.

BRgds Klaus

Klaus,

No screw-up registered here. It is all grist for the mill. Congrats on your early AR-5s. Sounds like you can appreciate them.

Roger

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...