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AR9 restoration


Mafia1976

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Hi Matt

There are those who claim to hear improvements with expensive caps. There are also those who claim to hear improvements with high-priced spaeaker cables. And I remember when there was a digital clock marketed whose mere presence in a room produced "astonishing" results. Balderdash.

Your speakers originally used non-polar electrolytic capacitors. You could replace them with new non-polar electrolytics (NPEs) and they would work perfectly well. The advantage to film caps is that they last a long time, whereas NPEs can go out of spec in a couple of decades.

A sane compromise is to use film caps for the smaller values (say up to 20 or 30uF) and NPEs for the 50uF and up.

For my recent crossover rebuilds I've used very inexpensive surplus capacitors from Madisound: 60 cents each for 10uF and 35 cents for 2uF.

I'm not sure what caps are available in Europe but I know that Solens are well-respected, not too expensive, and made in France. I assume that EU products are more economical for you than importing them from the US.

OTOH, if purchasing from Madisound works for you I can recommend their surplus caps as being extremely economical and the Carli caps are very good buy. They also have Bennic NPEs and Solen film caps.

I do not have 9s myself and do not know what the parts list is. I did notice in your photo that there were some silver metal can capacitors. Those may very well be OK.

Good luck.

Kent

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OK. The schematic is here: http://www.classicspeakerpages.net/library/acoustic_research/ar-9_series_1978-1981/ar-9_series_schematicsservi/ar-9_schematics/ar-9_schematic.html

For the capacitors, it's the value in microfarads (uF or MFD) that counts. Any voltage is OK as long as it's at least as high as the original. So if you have an 8uF 100v cap it's fine to replace with an 8uF 400v one. Also, the uF value can vary by +/- 10% so if you need an 8uF cap and all you can find is 8.2uF that's perfectly fine.

Looking at the schematic quickly it looks like the cap values (per speaker) are:

4
(2) 6
24
30
40
80
470
2500

Better double-check that yourself. Your photo shows an 8uF, which I did not see on the schematic. Maybe there were different versions of this model.

I know trying to replace the 2500uF cap has been a major issue. So maybe others will chime in.

If I were doing these, I'd probably use these 2uF caps: http://www.madisoundspeakerstore.com/surplus-capacitors/2.0mfd/
and these 10uF caps: http://www.madisoundspeakerstore.com/surplus-capacitors/10.0-mfd-polypropylene-cap-10mfdp/tyee/

You just wire them in parallel to make your 4uF, 6uF, 24uF, 30uF, 40uF and maybe even the 80uF values.

Here is the 80uF NPE http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-80-mfd-electrolytic-caps/

This is OK for the 470 and you could one (in parallel with other caps) for the 2500 I think (but wait for others to comment) http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-500-mfd-electrolytic-caps/

or to get closer to 470 you could use one 200 + one 280

Here is the 1000 to use to make up a 2500 http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-1000-mfd-electrolytic-caps/

Hope all that makes sense but remember--I have not worked on one of these so others may give better advice, and I'm not sure about the cap values in YOUR speakers.

Kent

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OK. The schematic is here: http://www.classicspeakerpages.net/library/acoustic_research/ar-9_series_1978-1981/ar-9_series_schematicsservi/ar-9_schematics/ar-9_schematic.html

For the capacitors, it's the value in microfarads (uF or MFD) that counts. Any voltage is OK as long as it's at least as high as the original. So if you have an 8uF 100v cap it's fine to replace with an 8uF 400v one. Also, the uF value can vary by +/- 10% so if you need an 8uF cap and all you can find is 8.2uF that's perfectly fine.

Looking at the schematic quickly it looks like the cap values (per speaker) are:

4

(2) 6

24

30

40

80

470

2500

Better double-check that yourself. Your photo shows an 8uF, which I did not see on the schematic. Maybe there were different versions of this model.

I know trying to replace the 2500uF cap has been a major issue. So maybe others will chime in.

If I were doing these, I'd probably use these 2uF caps: http://www.madisoundspeakerstore.com/surplus-capacitors/2.0mfd/

and these 10uF caps: http://www.madisoundspeakerstore.com/surplus-capacitors/10.0-mfd-polypropylene-cap-10mfdp/tyee/

You just wire them in parallel to make your 4uF, 6uF, 24uF, 30uF, 40uF and maybe even the 80uF values.

Here is the 80uF NPE http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-80-mfd-electrolytic-caps/

This is OK for the 470 and you could one (in parallel with other caps) for the 2500 I think (but wait for others to comment) http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-500-mfd-electrolytic-caps/

or to get closer to 470 you could use one 200 + one 280

Here is the 1000 to use to make up a 2500 http://www.madisoundspeakerstore.com/electrolytic-cap-100vdc/bennic-1000-mfd-electrolytic-caps/

Hope all that makes sense but remember--I have not worked on one of these so others may give better advice, and I'm not sure about the cap values in YOUR speakers.

Kent

Be careful. One of the caps on the schematic is wrong, I've forgotten which one. When I recapped mine I noticed it, I used the same value as printed on the original capacitor in the speaker, not the one on the schematic. I don't know if the schematic has been corrected.

It is usually not necessary to replace the two largest metal can capacitors and if they are still okay it is not a good thing to do. Others who did realized they'd made a mistake.

While the speakers are rated to handle up to 400 watts per channel continuously for the woofers and according to the test in Stereo Review Magazine will actually handle a 4 KW per channel impulse before distorting, I've never felt it was wise to tempt fate. The HK amplifier suggested should be fine. IMO 155 WPC is more than adequate for most circumstances. 400 watts would only play those woofers about 4 db louder. I actually use a 60 wpc amplifier in a 4000 cubic foot room that's on the live side and have never had a problem with inadequate power. Good solid bass and stability with low impedance loads are more important with this speaker.

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Thanks Soundminded. Good to have consensus on those points, i.e.

  1. leave the big metal cans
  2. double-check the cap values because the schematic is wrong (see Rlowe's link)
  3. don't waste money on a bigger amp--yours is fine

Kent

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Thank you all for you input it really is appreciated. :)

Yes my 9's have the 8uf cap between the UMR not the 6uf & it's that one that is leaking.

I feel a lot happier after reading you replies & think ill use solen caps as I can replace all caps except the 2 big cans for £115.

I will try & removed the XO boards tonight when I get home. Eek!!

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A 40 watt iron from Radio Shack or Home Depot should do the job - I'm guessing about $15.00, or so.

Unless you really want to, removing the crossover boards shouldn't be necessary, as all of the caps are easily accessible, and the boards are both stapled and glued into place.

I've never seen a factory-built stand for the AR-9, only after-market mods like SHOKDU's custom granite bases.

Your Marantz is an excellent Ken Ishiwata design which can be switched from a low-wattage Class A operation to the full rated output in Class AB - it should sound great with the AR-9.

I just noticed your first photo - is the cabinet area covered by the woofer grille panels unfinished?

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A 40 watt iron from Radio Shack or Home Depot should do the job - I'm guessing about $15.00, or so.

Don't know if they have Rat Shack or Home Despot in the UK but I checked Amazon .co.uk for 40 watt soldering irons: http://www.amazon.co.uk/s/ref=sr_st?keywords=40w+soldering+iron&qid=1365106590&rh=n%3A79903031%2Cn%3A!79904031%2Cn%3A1938841031%2Cn%3A1939319031%2Cn%3A1939402031%2Cn%3A1939415031%2Cn%3A1939417031%2Ck%3A40w+soldering+iron&sort=price

They start around 5 pounds.

Gas may work IF it's designed for electronics. You want the tip to be around 600 degrees F. Saw this on Brit Ebay and if yours is similar it should work: http://www.ebay.co.uk/itm/New-Electronics-DIY-Gas-Soldering-Iron-MT-100-A-useful-practical-modern-/150989819247?pt=LH_DefaultDomain_3&var=&hash=item2327b1cd6f

Kent

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My gas soldering iron reaches 1075 F but think ill get an electric one as it exhausts a lot heat fom the side & might get too hot close to wires.

Yes i will try & leave XO boards in & work around them might be safer. :)

im not sure what you mean by unfinished panels Ar-pro? sorry, but i havent touched the cabs at all & need to replace cloth once all completed & running & i have several pieces of 1" thick granite to put them on instead of the wooden ones that came with them.

Is it worth replacing the wiring to the speakers inside while im replacing components?

i will try & upload a few more photos of them.

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I wouldn't recommend using the gas soldering iron. That get's way to hot for what you want to do. As the other guys suggested a nice little 40 watt electric soldering iron is ideal.

Both sets of 9's I've done I removed the xovers but I replaced ALL the caps and it was much easier that way. Since your only replacing the caps for the uppers probably easier to leave the boards in.

Replacing the speaker wires won't hurt but won't help much either.

Good luck. Your going love those babies!

John

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My foam kit has arrived & I must admit I'm very excited now! I just need to order caps now ready for the task of replacing them all!!

I only have a gas soldering iron with various tips will this be ok or should I get a mains variable one?

If you're talking about a small gas torch no this will not do. You will likely damage the equipment. Buy a soldering Iron suitable for use with electronic components. Use only rosin core solder. Practice soldering technique with scrap wire before you work on your speakers. There are many instruction manuals on line, surely on YouTube. Its very easy to learn the correct technique. apply the heat to the wire, and the solder to the wire. Do not try to melt the solder with the iron. You should heat the iron, clean it with a damp rag, and then tin the iron with solder before soldering. Make the mechanical connection between the leads first before you solder, don't rely on the solder to do that. Use an iron that's large enough. For this I'd probably use about a 100 to 150 watt iron. An iron that's too low in wattage will take too long to heat the wire. The iron should be fully hot first before you use it. Actually soldering should take no more than a couple of seconds. The flow of solder should be even and cover both wires. It should cool shiny, not dull. If it's dull you probably have a cold solder joint that will not be reliable. Reheat it and melt it again. The solder should create one smooth continuous flow between the two wires. Do not use too much solder it isn't necessary. Be careful of dripping solder damaging, shorting other components. I like to place something non flammable under the work. Before finishing, be sure to remove any loose small droplets of solder, pieces of wire, etc. that could cause a short circuit. Good luck with your speakers. Many people who know what they are but don't have the opportunity to acquire them would be envious.

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Thank you i will get a new iron & solder as I hope to have these speakers for a long time.

Sorry Ar-pro, what you can see is the repair that the previous owner had done.

They used industrial packing tape on all four woofers as the surrounds had rotted away!

It has taken me hours to remove it all without damaging them. I'm hoping they haven't damaged the voice coils, I have removed the dust caps & all seem to move freely & have equal resistance of 2.9-3.0 ohm using my multi meter so there is no dead short inside.

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The LF section of the crossover must cut off two nominally four ohm loads in parallel at 200 hz. As explained in the excellent write-up in the library by Tim Holl it must also keep the load impedance above acceptable limits for amplifiers it would typically be used with. The complex network accomplishes both. The use of the 12" driver as a true subwoofer IMO is a concession that a 3 way system simply cannot cover the entire audible range without compromise. Finally an AR speaker that does.

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when i purchased speakers i was given this pair of stands & told they were for the 9's?

apparently the girls farther worked for teledyne AR uk & they were supplied with them.

any thoughts or comments?

There were never any stands made by Acoustic Research for the AR9. The reason is that it would have defeated the purpose of having the woofers close to the floor-wall intersection, part of the original design of the AR9 to avoid the "notch" (now referred to as the "Allison Boundary Effect") in the lower frequencies caused by a reflection from the floor and from the back wall that bounces back out of phase with the speaker's output at certain bass frequencies. Furthermore, stands would actually hurt the low-bass capabilities of the speaker slightly by raising the woofer up away from the floor boundary, much like pulling the AR9s out from the wall.

Therefore, if someone told you that the stands were made for the AR9, that might have been true, but the stands were likely fabricated by someone else. For best sound, leave the AR9s on the floor -- at least a couple feet from the corners -- and not more than a few inches out from the front wall itself. Positioned this way, the AR9 can hold its own with just about any loudspeaker ever made when it comes to delivering low-distortion, smooth and extended bass response.

A couple of interesting historical tidbits: (1) the AR9 was principally designed by Tim Holl and was originally going to be called the "AR-25," but the name was changed to "AR9" before the final prototypes were completed; (2) some engineers at AR were hard at work on a "powered" version of the AR9, but for some reason it never saw the light of day. Nevertheless, the AR9 became one of AR's more successful high-end speakers ever, and the speaker is considered to be one of the company's top designs.

--Tom Tyson

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There were never any stands made by Acoustic Research for the AR9. The reason is that it would have defeated the purpose of having the woofers close to the floor-wall intersection, part of the original design of the AR9 to avoid the "notch" (now referred to as the "Allison Boundary Effect") in the lower frequencies caused by a reflection from the floor and from the back wall that bounces back out of phase with the speaker's output at certain bass frequencies. Furthermore, stands would actually hurt the low-bass capabilities of the speaker slightly by raising the woofer up away from the floor boundary, much like pulling the AR9s out from the wall.

Therefore, if someone told you that the stands were made for the AR9, that might have been true, but the stands were likely fabricated by someone else. For best sound, leave the AR9s on the floor -- at least a couple feet from the corners -- and not more than a few inches out from the front wall itself. Positioned this way, the AR9 can hold its own with just about any loudspeaker ever made when it comes to delivering low-distortion, smooth and extended bass response.

A couple of interesting historical tidbits: (1) the AR9 was principally designed by Tim Holl and was originally going to be called the "AR-25," but the name was changed to "AR9" before the final prototypes were completed; (2) some engineers at AR were hard at work on a "powered" version of the AR9, but for some reason it never saw the light of day. Nevertheless, the AR9 became one of AR's more successful high-end speakers ever, and the speaker is considered to be one of the company's top designs.

--Tom Tyson

It's been 35 years since AR9 was introduced to the market yet surprisingly few if any speakers at any price seem to be able to equal let alone outperform its bass. Certainly nothing remotely close to the price even allowing for inflation. How would an AR9 with 2 12" woofers stack up against Ken Kantor's NHT 3.3 with one Tonegen 1259 12" based presumably on the AR woofer although it has a plastic cone and a Vas I think about double the AR 12"? It's also a side firing woofer. Parts Express RS1200 series subwoofer seems to have also borrowed from knowledge gained in AR9. Its got 2 side firing 12" AS subwoofers, one on each side as with AR9 along with a fairly powerful plate amplifier. Any thoughts on either of these two designs? Genesis G1.1 and 1.2 refinements of the Infinity IRS in various versions seems to have 2 towers with six 12" AS woofer each. Servo control over one woofer in each tower (2 in the G1.2) is said to reduce distortion but this doesn't really seem necessary given the already inherently low distortion of high quality AS woofers.

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So instead of stands ill sit them on a piece of granite. They will be sat on carpet on a concrete floor should I put spikes on the speakers or granite or not at all? I'm also hoping to order all the caps this week & solen seem to be the best value for money. Will they be an improvement over standard?

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  • 2 weeks later...

Help!!

I'm just about to refoam the 9's & with the shims in place the cone is slightly off centre!

If I glue the foams on will they be ok as I've put the shims in place? I'd hate to mess them up.

Also caps will be on order this week so hopefully they will be up & running soon. :)

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Place your new foams on the cone exactly where they will be glued to the cone's edge and look to see if you have enough foam at the outer flat part to glue it down to the brown ring at the inner edge of the frame. 1/8 inch minimum should be enough to hold as long as you use a good, strong glue. I suggest you use the brown glue sold by Orange CTY speaker repair.

Sometimes the cones don't end up perfectly concentric with the frame at the largest diameter of the cone. The important thing is you have shims in place when you glue the foam to the frame's edge.

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