Recapping of Ar9

[Gualti]

Good morning to the whole forum.

I am the lucky owner of a pair of Ar9 that I tried to keep in the best way in all these years.

Now I want to replace the capacitors now dated, but I found myself confronted with a problem that seems simple but it is not.

I have to unstick the crossover bases, in order to replace the capacitors, but it is difficult to do so, the bases of masonite that make up the crossovers are strongly bonded to the internal base of the speakers and the space is so cramped that it can not work.

Do you have any advice on how to do it without ruining them?

I accept your advice and thank you in advance.

[DavidR]

Do them in place. There's lots of room compared to other AR speakers.

[Gualti]

Thank You DavidR, I was also suggested by others to do it on the spot, I think it's the best solution, I try! Thank you!

[valkyrie]

The LF crossover board is removable - the HF section is not.  Best to do the HF board "in place".  Read AR-Pro's comments in regards the type of capacitor that should be used in the UMR and tweeter crossover.  I have found that those capacitors should NOT be film - but instead a Mundorf NPE - the film caps seem to cause a quality of shrillness and gritty sound to recordings of instruments such as massed violins hitting high notes.

Glue your new caps in place with silicon sealer - works better than the original glue.  You might want to reorient your coils on the LF board so that they are at right angles to each other - thus reducing cross coupling between the coils - except for the one inductor which is a stacked unit.

Also - if you have a high quality modern amplifier there is NO NEED TO USE THE 2500 uF cap in the LF crossover.  That is was put in place by Holl to prevent the really low impedance of two AR 12" woofers in parallel, < 2 ohms, from causing a typical 1979 style amp to blow up from attempting to source too much current.  Modern amplifiers - NOT RECEIVERS - can easily handle a < 2 ohm load.  Pass amps will do so, as will product from Odyssey Audio.  No doubt there are other solid state amps that can handle such low load impedance.   I have used both those amps with an AR-9 that did not have the 2500 uF cap in place and had no problems at all.

I have an article on this forum - carefully moved from this section by the "powers that be" - that show an F/R plot of the before and after results of not using the 2500 uF cap - you will get more lower bass without that cap in circuit.

[AR surround]

20 hours ago, DavidR said:

Do them in place. There's lots of room compared to other AR speakers.

Congratulations on your new AR9s!   Ditto what David said about working on these speakers in-place:  If you remove both woofers, you can shine a lamp through one side while you work/solder through the other woofer opening.  Also, you might want to read through some of the AR9 recapping threads on this forum.   And heed valkyrie's recommendation about which capacitors to use on the UMR.   I went through a lot of time trying Poly caps on the UMR and nothing worked.   I finally settled on Mundorf E-Caps for the UMR with a Dayton 0.01uF film & foil (F&F) bypass capacitor.   Although the UMR sounded good with just the E-Cap, I wasn't completely happy until I added the F&F bypass.

Regarding the tweeter caps, I was successful using Dayton poly caps with Dayton 0.01uF F&F bypasses.  As DavidR can tell you, adding the F&F bypass caps changes improves the sound of the tweeter...what used to sound like a "chhhhhuh" will sound like a "shhhhhhh" as it should.   But you can dispense with fooling with Poly caps altogether and use Mundorf E-Caps with the Dayton F&F bypasses or Vishay F&F bypasses with great results.

[Gualti]

28 minutes ago, valkyrie said:

.... there is NO NEED TO USE THE 2500 uF cap in the LF crossover.  That is was put in place by Holl to prevent the really low impedance of two AR 12" woofers in parallel, < 2 ohms, from causing a typical 1979 style amp to blow up from attempting to source too much current.  Modern amplifiers - NOT RECEIVERS - can easily handle a < 2 ohm load.  Pass amps will do so, as will product from Odyssey Audio.  No doubt there are other solid state amps that can handle such low load impedance.   I have used both those amps with an AR-9 that did not have the 2500 uF cap in place and had no problems at all.....

Hi Valkyrie! My system is composed of Denon PRA 1500 Preamplifier and two Denon POA 4400A monophonic end devices, although I know they can drop a lot of impedance, I do not know whether to trust to remove the 2,500 MF cap. What would you consider to be the advantages of removing it?

Thank You!

28 minutes ago, valkyrie said:

 

 

[Gualti]

21 minutes ago, AR surround said:

... Regarding the tweeter caps, I was successful using Dayton poly caps with Dayton 0.01uF F&F bypasses.  As DavidR can tell you, adding the F&F bypass caps changes improves the sound of the tweeter...what used to sound like a "chhhhhuh" will sound like a "shhhhhhh" as it should.   But you can dispense with fooling with Poly caps altogether and use Mundorf E-Caps with the Dayton F&F bypasses or Vishay F&F bypasses with great results ....

Ar Surround thank you for this precious advice!

[lARrybody]

55 minutes ago, valkyrie said:

The LF crossover board is removable - the HF section is not.  Best to do the HF board "in place".  Read AR-Pro's comments in regards the type of capacitor that should be used in the UMR and tweeter crossover.  I have found that those capacitors should NOT be film - but instead a Mundorf NPE - the film caps seem to cause a quality of shrillness and gritty sound to recordings of instruments such as massed violins hitting high notes.

Exactly which cap in the UMR are we talking about? The 24uf cap, the 8uf cap, or the 40uf cap or all three?  The 40 and 8 go to ground so I am thinking the 24uf cap is the important one.

[DavidR]

1 hour ago, larrybody said:

Exactly which cap in the UMR are we talking about? The 24uf cap, the 8uf cap, or the 40uf cap or all three?  The 40 and 8 go to ground so I am thinking the 24uf cap is the important one.

Specifically the series cap - the 24uF

[Mez]

I just finished re-capping the HF on my AR-9s.  I pried out the Masonite panel to work on it.  The panel is glued and stapled around the edges in place.  I worked slowly around edges I could reach with a screw driver and it popped right out.

Actually, the glue didn't stick very well to the black paint on the back side of the Masonite.  It was held on mostly with the staples.

After replacing the caps, I glued it back in place with hot glue.

[DavidR]

2 hours ago, Mez said:

I just finished re-capping the HF on my AR-9s. 

What caps did you use and how do they sound?   ...........any resistor changes?

[DavidR]

@Gualti: what caps do you plan to install?

[Mez]

Dayton and Solen polypropylene, and Parts Express NPE brand.  No resister change.  Haven't worked on the woofer crossover yet.  Played some but haven't had them long enough to venture an opinion.

[AR surround]

27 minutes ago, Mez said:

Dayton and Solen polypropylene, and Parts Express NPE brand.  No resister change.  Haven't worked on the woofer crossover yet.  Played some but haven't had them long enough to venture an opinion.

Where did you use the Solen?

[Mez]

Can't remember.  But this is what I bought. I'm not an expert.

Solen 24uF 400V Polypropylene Capacitor

[DavidR]

2 hours ago, Mez said:

Solen 24uF 400V Polypropylene Capacitor

 

[AR surround]

8 hours ago, Mez said:

Can't remember.  But this is what I bought. I'm not an expert.

Solen 24uF 400V Polypropylene Capacitor

If it turns out that you do not like the sound of that 24uf Solen on the UMR, take a look at this thread:

 

[Mez]

Thanks.  I'll try those caps.

[valkyrie]

On 7/23/2018 at 11:46 AM, Gualti said:

Hi Valkyrie! My system is composed of Denon PRA 1500 Preamplifier and two Denon POA 4400A monophonic end devices, although I know they can drop a lot of impedance, I do not know whether to trust to remove the 2,500 MF cap. What would you consider to be the advantages of removing it?

Thank You!

 

Holl - the chief designer of the AR-9 clearly stated that the addition of the 2500 uF cap in the LF crossover was to allow a sufficient impedance at resonance so that the combination of TWO 12" woofers would not be a threat to the amplifiers of the time - circa 1979.   What happens is that the big cap allows the reactive capacitance to form an effective DC resistance that adds to that of the 2 woofers in parallel - which is < 2 ohms.  

Somewhere on this forum are some notes from Holl that describe his engineering perspective on using the two woofers in the AR-9.  He clearly AND UNEQUIVOCALLY STATES THAT THE PURPOSE OF THE LARGE CAP IS TO ALLOW SOME PROTECTION TO AMPLIFIERS BY PROVIDING MORE RESISTANCE.

Modern high quality amplifiers - solid state that is - can easily handle a 2 ohm load without incurring any damage.  Pass amps and Odyssey Audio amps have no problem with a < 2 ohm load. I am sure there are other amps equally capable - but the two listed I know for sure have no problem with such a load.

The gain?  Better low end response - your system will have more power in the 25 Hz region, and more power in everything above that range up to about 60 Hz.  Above that there is not an noticeable difference.  Find my earlier posts on this issue which include before and after F/R plots. I think those posts were moved to some obscure portion of the forum - perhaps the "modification" listings - because the "powers that be" did not like my approach.  From their perspective any modification of the sacrosanct original AR configuration is a grievous sin that must be punished with all haste.

How dare that some simple peasant such as myself, clearly not a member of the rarefied cognoscenti, dare to modify any AR for any reason.  These folks will also tell you to not change the wire in the internal loom - even though it is a pile of decrepit junk.

Change the wire - the factory wire was grossly under specified.  Use a lower gauge - say 14 - and double runs on the woofer feeds.  Solder all your connections - even to the drivers.  Do NOT use the junky spade clips from AR - they were there merely to facilitate production.

Make sure your LMR "can" is still attached to the cabinet face - they factory used a crummy glue which has long since hardened, cracked and come loose.  That is critical to good sound from the Mighty Nine.

AR designed and built wonderful speakers - they can be improved.  Even after 40+ years.

[DavidR]

8 hours ago, valkyrie said:

Modern high quality amplifiers - solid state that is - can easily handle a 2 ohm load without incurring any damage. 

Many amplifiers today are 'stable' with a 2 ohm load BUT without that cap you could see loads lower than 2 ohms. 

[Aadams]

9 hours ago, valkyrie said:

The gain?  Better low end response - your system will have more power in the 25 Hz region

Are you listening to ordnance disposal recordings?  There are only two western musical instruments that will sound a note lower than 32hz and few, if any,  members of this forum listen to music that features either of them playing in that range.  

Adams

 

 

   

[AR surround]

1 hour ago, Aadams said:

Are you listening to ordnance disposal recordings?  There are only two western musical instruments that will sound a note lower than 32hz and few, if any,  members of this forum listen to music that features either of them playing in that range.  

Adams 

Perhaps if the LFE channel of a movie was routed to the AR9's...that can be really low frequency, although not what these speakers are meant to handle.  (I can tell you from experience that they will handle it!!)

[DavidR]

My amps are stable into 2 ohms but I still wouldn't leave out the 2500uF cap and plan on replacing them in my 9 project.

[valkyrie]

The low C on a pipe organ is 32 Hz.  Most speakers, including a $50,000 Wilson Audio behemoth, will NOT handle a low C.  In fact I have found that the great majority of speakers rated as -3dB at 35 Hz have actually folded their sonic tents around 50 Hz and quietly gone home.

In addition with symphonic music there is an effect that I refer to as "hall lift", wherein the cavernous space in which the music is played seems to underscore the music with a low frequency quality.  Very low.

Then there is electronic music - see Zach Hemsey recordings for more information.

Regardless - it is my stereo, I tune and play it THE WAY I ENJOY IT - and what you "think" is "right" is of no possible concern to myself. If you want to leave in a tribute to ineffective engineering and semiconductor capability from 1979, e.g. the 2500 uF cap?  Then please be my guest.  Your tunes - hear them as you wish.

This is a forum for the expression and discussion of ideas - not a political indoctrination center wherein we all must follow the "one and true path". 

I got rid of that silly cap - good riddance.  YMMV.

[Aadams]

1 hour ago, valkyrie said:

The low C on a pipe organ is 32 Hz.  .................................etc

IMO you could be correct on every point.  Electronic music aside, I was wondering how increased output at 25hz improved the 32hz organ, electric bass or piano note.   It was not a challenge.  You used 25hz as a target as though it would improve the musical experience when in fact there is zero music written for 25hz unless it is electronically generated................. probably for a movie soundtrack.  Even the "very low" hall lift can't go lower than the lowest note being sounded.  

Adams