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AR9 question


DavidR

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Hi All,

I'm new to the Classic Speaker Pages but have already read many great threads here.

Since retiring I have given up a long time hobby to get back into my love for audio gear - my new hobby.

I currently have a real nice pair of AR90s, a pair of Polk RTA12C and some Bose 901s VI. The 90s outperform hands down.

I have been searching for a pair of AR9s so I can Biamp. I gave up on my idea of making my AR90s biamp capable after reading many threads here.

My question is about the change in the crossover network in the AR9s> how can I tell if what I am buying has the 2 #6 coils in the xover w/o opening the speaker up? I know that the early AR9s only had the single #6 coil. Any advice will be greatly appreciated.

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My question is about the change in the crossover network in the AR9s> how can I tell if what I am buying has the 2 #6 coils in the xover w/o opening the speaker up? I know that the early AR9s only had the single #6 coil. Any advice will be greatly appreciated.

Welcome to CSP, David...

The short answer to your question is you cannot tell what is or is not in the AR-9 crossover without looking at it. IF there were actually any crossover changes in the AR-9, they have not been verified, nor are they anything to be concerned about.

Roy

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I've read several threads (mostly here) that the early AR9s had a single #6 coil and a 2nd #6 coil was added shortly/sometime after after production began.

Perhaps its an 'urban myth' and was never true but there is a conception out there that this was the case. I just saw it in an eBay add for a pair of 9s out in California.

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I've read several threads (mostly here) that the early AR9s had a single #6 coil and a 2nd #6 coil was added shortly/sometime after after production began.

Perhaps its an 'urban myth' and was never true but there is a conception out there that this was the case. I just saw it in an eBay add for a pair of 9s out in California.

David,

It was a 6uf vs 8uf capacitor, not a coil, that was questioned, and it was most likely a matter of confusion over an unclear potion of the schematic posted here. I do some work for Ebay's "Vintage AR", and have seen a fair number of AR-9 crossovers lately. There are no "earlier" or "later" crossovers to be concerned with.

Roy.

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Hi Roy

I think I met you when Larry dropped off my AR90s a few years ago in Framingham, MA

That's great news about the xover confusion and how its steamrolled way out of proportion.

Any AR9s for sale? Larry said he had a pair of the LSi style at the time, several months ago, but I told him I wanted the Legend as I want to biamp.

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Hi Roy

I think I met you when Larry dropped off my AR90s a few years ago in Framingham, MA

That's great news about the xover confusion and how its steamrolled way out of proportion.

Any AR9s for sale? Larry said he had a pair of the LSi style at the time, several months ago, but I told him I wanted the Legend as I want to biamp.

Hi David,

Yes, I remember...a very pleasant day. :)

Larry has no AR-9's for sale. In the large speaker department, he still has the LSi's and just acquired some nice looking LST's and LST 2's.

Roy

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  • 4 weeks later...

couple of things;

You should be able to bi-amp the AR-90 - the only difference between the 90 and the 9 was that the 90 had two 10" woofers.

There are two changes to the crossover - some time after initial production (it has been suggested this change occured in 1980 in the first quarter) the mid-range dome had a #6 coil added in shunt across the MR driver - this is NOT noted on the crossover schematic - but is generally present on most AR-9s. The MR crossover section (all of the crossovers are in parallel with each other) was a very complex (and troublesome) circuit - as it was bandpass from 1200 Hz to 7000 Hz - and the MR driver itself was a "newer" driver for AR.

The other change is due to a schematic error - the original blueprint showed a 8uF capacitor in shunt across the MR driver - and this on the print looked like the number 6 - but the actual crossover value is 8 uF. I don't know of ANY original (as built) crossovers that have a 6 uF cap in that position - but a great many people (including myself) when rebuilding the crossover and referencing the published schematic installed an 6 uF cap. And as a result had a bit of a peak at or around 7 KHz.

The Nine sounds best with the extra coil in place AND the 8 uF cap.

They also have much better bass if you cut loose the 2500 uF cap in the bass crossover - that thing was only placed there to support the weak amplifiers of that era (most could NOT handle the resulting 2 ohm resonant point resistance). If you have a modern amplifier (not an vintage unit) that should be able to easily handle the low impedance of the bass units. See my post on this topic - should be in the archives.

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couple of things;

You should be able to bi-amp the AR-90 - the only difference between the 90 and the 9 was that the 90 had two 10" woofers.

There are two changes to the crossover - some time after initial production (it has been suggested this change occured in 1980 in the first quarter) the mid-range dome had a #6 coil added in shunt across the MR driver - this is NOT noted on the crossover schematic - but is generally present on most AR-9s. The MR crossover section (all of the crossovers are in parallel with each other) was a very complex (and troublesome) circuit - as it was bandpass from 1200 Hz to 7000 Hz - and the MR driver itself was a "newer" driver for AR.

The other change is due to a schematic error - the original blueprint showed a 8uF capacitor in shunt across the MR driver - and this on the print looked like the number 6 - but the actual crossover value is 8 uF. I don't know of ANY original (as built) crossovers that have a 6 uF cap in that position - but a great many people (including myself) when rebuilding the crossover and referencing the published schematic installed an 6 uF cap. And as a result had a bit of a peak at or around 7 KHz.

The Nine sounds best with the extra coil in place AND the 8 uF cap.

They also have much better bass if you cut loose the 2500 uF cap in the bass crossover - that thing was only placed there to support the weak amplifiers of that era (most could NOT handle the resulting 2 ohm resonant point resistance). If you have a modern amplifier (not an vintage unit) that should be able to easily handle the low impedance of the bass units. See my post on this topic - should be in the archives.

When I restored/recapped my AR-90s few years ago, I have used this crossover schematic:

post-101175-1200137398.gif

Updated AR9 UMR section:

post-101112-1239541090_zpscc0715c0.jpg

Compared to the "updated" AR9 schematic

(AR90 and AR9 are identical, except for the dual woofers section),

it seems that all elements of confusion are already there in the original AR90 schematics,

the second 1.37mH coil and the 8uF capacitor instead of 6uF.

So I guess I was lucky! :)

I never saw the "wrong" schematic and I was surprised to read about this confusion.

Maybe only the AR9 schematic was bad and the AR90 schematic was OK all the time?

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Maybe only the AR9 schematic was bad and the AR90 schematic was OK all the time?

To the best of my knowledge, there is no ambiguity regarding the AR-90 crossover Blueprints and Schematics that we have available on this site.

Regarding the AR-9, specifically the cap in parallel with the upper midrange, my understanding of how the misreading arose is detailed in the following thread:

The mystery has been solved

Robert_S

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Ok! Thanks! :)

For some reason, the wrong(?) schematics are still present in the library section.

This could cause lots of problems to people who are only getting the schematics from the library in order to restore their 9s, but do not follow the forum.

Updating the schematics in the library, could help the future AR9 restorers a lot. :)

There is also this topic, with the missing value for the other inductor in woofer section,

measured (blue) values only show how much the original capacitors values have drifted over the years

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4587

post-103149-1217542695.jpg

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Thanks for all the info and links. Good 'history' reading.

Can anyone tell me the proper way to eliminate the 2500uF cap in an AR9 ?

I'm able to follow a line diagram but when I look at the actual layout of the caps and wiring its not as clear to me.

On the AR90s drawing I don't believe the level switches and associated wiring are drawn correctly (on the line diagram).

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In the past we've discussed how electrolytic capacitors increase their value over time as the dielectric material degrades. Polys should be much more stable than the older cheap type NPCs. The danger this presents is to the upper midrange and tweeter for the series capacitors. When the 6 and 24 mfd caps increase, the crossover frequency to those drivers is lowered risking overdriving them at frequencies lower than they are intended to operate at. This is true to a lesser degree for the 80 mfd cap in the LMR. The shunt caps increasing in value, especially the 8 mfd across the UMR will simply roll off its high end sooner. As these drivers are difficult if not impossible to replace (not as bad as AR3/3a but not good and not cheap) it's best to replace them if they've drifted too much. 10% is probably acceptable but not much more.

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In the past we've discussed how electrolytic capacitors increase their value over time as the dielectric material degrades. Polys should be much more stable than the older cheap type NPCs. The danger this presents is to the upper midrange and tweeter for the series capacitors. When the 6 and 24 mfd caps increase, the crossover frequency to those drivers is lowered risking overdriving them at frequencies lower than they are intended to operate at. This is true to a lesser degree for the 80 mfd cap in the LMR. The shunt caps increasing in value, especially the 8 mfd across the UMR will simply roll off its high end sooner. As these drivers are difficult if not impossible to replace (not as bad as AR3/3a but not good and not cheap) it's best to replace them if they've drifted too much. 10% is probably acceptable but not much more.

Do you recommend any particular brand of metallized polypro. I know Vintage_AR recommends Dayton. Dayton seems to have the correct uF values to do the job; except for the woofer - I would probably use NPE if I knew of a good brand.

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Member SHOKDU replaced all of his AR-9 caps last year, and was very happy with the result.

I'm not sure if he ever posted the source, brands, or actual values of the caps that he used as replacement and bypass capacitors, but this is the thread:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7612&hl=%22ar-9%22+capacitors

Based on the current availability of the parts that he used, and the excellent outcome, that information could be pretty useful for anyone looking to more easily update their AR-9 speakers.

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Do you recommend any particular brand of metallized polypro. I know Vintage_AR recommends Dayton. Dayton seems to have the correct uF values to do the job; except for the woofer - I would probably use NPE if I knew of a good brand.

I never worked on an AR-9 but there is nothing magic about Dayton. They're fine. So are Erse, Carli, Solen, Bennic, etc. If I were doing it I'd shop for the best price. You'll have to use NPEs for the 470 (or is it 350?) and 2500uF. For the medium sizes (30, 40, 80uF) you could use either film or NPE or even a combination. Depending on how much room you have inside the box (I assume a lot) you could buy a pile of Madisound's 10uF "surplus" caps for 60 cents each and build up the 24, 30, 40 and 80uF values. That would be 17 per cabinet, or 34 all together for $20.40 plus the smaller values needed (I'm looking at the schematic in post #16). Or get 50 of the surplus caps and the price drops to 50 cents each.

As I said--I've never worked on the 9. Closest was the 91, which is a different beast, so don't depend on my ramblings for the values of the caps. My point is there's no need to fret about the brand you use (IMHO. Some would argue that high-price caps have magical properties that seems like hooey).

Kent

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I think many have their favorite cap and thats what they recommend.

What about the NPE cap? Is Erse a good fit? They have the correct values.

You're right. People get excited about caps. The originals were cheap NPEs and the only thing wrong with them is they tend to leak and/or drift after 2 or 3 decades. Expensive capacitors (or interconnects or speaker wires etc.) will not "improve" the sound.

Erse makes good quality products at very fair prices. If they have the correct values they should be good.

Please remember my disclaimer: I have worked on dozens of speaker but never the AR-9. I cannot comment on which schematic is correct (best bet is to see what's in there and replace with the same value, +/- 10%).

One other comment: I doubt the 9s have any 5w resistors but IF they do I would replace them with 10w. KLH used 5w resistors in their speakers and I have seen scorched, burned or even crumbled resistors in their flagship Twelve and Five speakers. Whenever I see a 5w resistor I replace it.

Good luck with your project!

Kent

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This post of mine from April May be of use. It documents my replacement of caps on my AR-90s with values, part numbers, and pricing at the time.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7881

John Falconer

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