Recapping the bass section of the AR9

[Diamonds&Rust]

I never got back to replacing the built-up caps in the 90s with a single (or couple) of caps. The bundle was better than the originals.

<sarcasm alert>

With the built-up caps in them, they sounded so good that the owner parted-out the system before I got the chance to replace them.

<sarcasm off>

I guess you're the one who'll have to try the built-ups, listen for 100 hours, replace them with a single (or couple), listen for another 100 hours, then replace the single with the bundle and listen for another 100 hours and report back !

BTW - if you just look at it logically, the bundle ought to sound better: Lower ESR for the bundle, faster charge and discharge times, etc. Except for there are these issues of unequal charge and discharge times and unequal resistance and the possibility for oscillations and multiple resonances inside the bundle itself... comb filtering from phase problems... wow.

There are just so many things to worry about... so, what to do, what to do?

But just to re-state, again, redundantly, I've had bad luck building-up everything from an 8uF to a 2500uF and the experience is consistent across models and drivers. So, no, I haven't done the 350uF in the 90, but it stands to reason its being an exception would be exceptional.

What I don't yet know is on what to blame the failure of the bundle. It could be a dozen things or a combination of dozens - or my ears. If my ears, it's other people's ears as well.

But really, it would be very interesting to hear your take on it after you've tried it.

[Kuja]

I never got back to replacing the built-up caps in the 90s with a single (or couple) of caps. The bundle was better than the originals.

<sarcasm alert>

With the built-up caps in them, they sounded so good that the owner parted-out the system before I got the chance to replace them.

<sarcasm off>

I guess you're the one who'll have to try the built-ups, listen for 100 hours, replace them with a single (or couple), listen for another 100 hours, then replace the single with the bundle and listen for another 100 hours and report back !

BTW - if you just look at it logically, the bundle ought to sound better: Lower ESR for the bundle, faster charge and discharge times, etc. Except for there are these issues of unequal charge and discharge times and unequal resistance and the possibility for oscillations and multiple resonances inside the bundle itself... comb filtering from phase problems... wow.

There are just so many things to worry about... so, what to do, what to do?

But just to re-state, again, redundantly, I've had bad luck building-up everything from an 8uF to a 2500uF and the experience is consistent across models and drivers. So, no, I haven't done the 350uF in the 90, but it stands to reason its being an exception would be exceptional.

What I don't yet know is on what to blame the failure of the bundle. It could be a dozen things or a combination of dozens - or my ears. If my ears, it's other people's ears as well.

But really, it would be very interesting to hear your take on it after you've tried it.

Bret, thanks a lot for your patience!

I wanted to try first this large 330uF cap that I managed to find locally.

Then I discovered that it is of very low quality and that some people reported that it actually exploded in their speakers!

So I'm back with my bundle of four 82uF caps and one 22uF cap.

My goal was just to restore those AR-90s and be done with them.

I must admit that I don't find the idea of opening them every 100 hours and soldering something inside, very appealing!

I hate soldering! I got a very nasty burn on my index finger earlier today .

Best regards,

Aleksandar

[Diamonds&Rust]

So I'm back with my bundle of four 82uF caps and one 22uF cap.

My goal was just to restore those AR-90s and be done with them.

Well, like we've said a lot of times, the good original parts were +/- 10% tolerance.

My guess, and if I were in your shoes this is what I would do, I would probably forgo the 22uF cap and just live with the four 82s. I think the problem may be the large difference in values. I don't *know* that. I can't do but the worst speculation as to why it might be. The 2500uF I built-up were two 1000uF, a 400uF, and a 100uF. I think there's a problem when the large can is ten times the value of the small. But I don't know where that stops. Four times? Three? Twice?

So, do what you're going to do, be amazed at how good it sounds, and sometime when you run across a good 350uF cap, buy a pair and be amazed all over again.

If we (all of us) don't get this explained scientifically it won't be for lack of trying. Until then, all I can do is report what I hear and try not to be intimidated into not-hearing it.

I know the whole issue is a tempest in a tea cup. These are old speakers we're enjoying. Yes, they sound good, but is this capacitor issue really, ultimately, in the big scheme of things, terribly important? Nah. But doing it "righter" do make a difference.

[kkc]

I replaced the caps in my AR94si and I am in full agreement regarding the positive improvements experienced. Replacing the old AR caps with polyprops made a huge positive difference. The bass is much better defined, faster and sharper.... I love it.

I also saw a discussion elsewhere about the foams these days being a bit stiffer then what the ARs would have had originally. If one thinks about this... refoaming with the thicker less pliant foam today combined with the faster and better power handling of polyprops can still only make the overall response better - and it does based on what I have observed with my AR94s. One would expect that in such a situation, one might lose the details e.g. as a drum beat decays - the cutoff may be sooner, but compared to the situation before changing caps and refoaming.... this is not the case at all. The positives outweigh the negatives by a mile. Another way to look at this is to say that resonance will go down...a good thing...!

Once I get the AR9s.... I do intend to change all caps....PERIOD....! This is no longer a theoretical question and even subjectively.... sorry, but the improvements are just so dramatic that you can forget subjective arguments for not changing caps.

Just one caveat... changing the tweeter caps produced a more pronounced and shrill high end on my AR94si. I ended up replacing the tweeter. I spoke with a former AR dealer and also some speaker builders and they all explained to me that the old tweeters were designed to play non-digital sources. Since the advent of the CD, a lot of old tweeters have a tough time and can sound harsh. Anyway, replacing the tweeters with some modern silk domes.... well.... what can I say..... the highs are wonderfully sweet and liquid now....!

Check out: http://www.own-initiative.com/%7Eowniniti/...R94_Rebuild.htm for full details.

Good luck and have fun....!

[rrcrain]

Solen makes 150 and 200uf poly caps that will work very well in the LF of the AR90.

Been there

done that

worked very well without breaking the bank

Richard

Bret, thanks a lot for your patience!

I wanted to try first this large 330uF cap that I managed to find locally.

Then I discovered that it is of very low quality and that some people reported that it actually exploded in their speakers!

So I'm back with my bundle of four 82uF caps and one 22uF cap.

My goal was just to restore those AR-90s and be done with them.

I must admit that I don't find the idea of opening them every 100 hours and soldering something inside, very appealing!

I hate soldering! I got a very nasty burn on my index finger earlier today .

Best regards,

Aleksandar

[AR surround]

So my next adventure is to replace the giant Callins 2500uF and 470uF caps in the AR9 woofer section.   The low bass comes across as a bit "ponderous" at times compared to the tight bass of my recently recapped AR90's.  I already purchased Mundorf E-Caps (Raw) in 470uF and 680uF values and made up a bundles totaling 2510uF.   

http://www.soniccraft.com/product_info.php/mundorf-cap-raw-680uf-63vdc-23vac-p-4063

But now I am concerned that the voltage rating of the E-cap Raw at 63VDC/23VAC is too low.   The existing Callins cans say 60 volts and 50 volts but with no indication whether that is AC or DC.  My Lexicon amp is 140 watts RMS into 8 ohms.   The Lexicon tech's guidance is that it will put out at least 180 watts RMS into 4 ohms and possibly 200.   The amp is stable handling loads down to 2 ohms.   I shot out an email to Mundorf with this info and await a response.

In the meantime, any guidance from anyone here?  I do not intend on ever driving these with a larger amplifier.

Thanks.

[DavidR]

Callins seems to label them with the AC rating on other caps so probably they are AC ratings.

[AR surround]

I received a reply from Mundorf regarding the power handling capability of the 63VDC/23VAC E-Cap Raw:

"It is not simple to answer your question.   The power handling of a capacitor is dependent on the electrical position in the filter.   The important thing is how much voltage the capacitor gets at its position and on which frequency. This must not be higher than 23 Volts AC.  According to the Impedance of the connected speaker this means it can hold approximately 66W at 8 Ohms and 132W at 4 Ohm.   It is dependent on the filter design if the capacitor gets a damaging voltage or not."

It appears that the power handling capability of the E-Cap Raw is not suitable, even for my size amplifier.   Time to consider Bennics or just not fool with the big Callins at all.

 

[kkc]

Hi, I recapped/rebuilt my AR9 speakers a few years ago.  See

for the details.  I am not so clued up on voltage etc anymore, I certainly never re-calculated these numbers as I expect that for the most part given the same capacitances, things should work out and they did.  If I was in your shoes, I would just do it.  All speakers are designed to work with a wide range of amps... you just need to match impedance.  I used some physically pretty large caps, but if you want to use smaller, look at the automotive sector... they use high values, are cheap & small and sound good.

One thing I would suggest is soldering the connections.  I used screw terminals as my solder was not powerful enough given the heavy wiring.  Trouble with screw terminals is eventually you have a layer of oxide.  In fact at some stage I am planning on building a spot welder (using a consumer grade microwave power unit supply - see youtube) and using that to spot weld all contacts after de-oxidizing. 

[AR surround]

Thanks kkc.   Very nice job with your AR9's.  You specifically state on the referenced thread:

"The two big woofer caps and the one big LMR cap were replaced with Mundorf electrolytics but then bypassed with some polypropylene caps to make the driver responsiveness faster. I had to bundle four Mundorfs plus one polypropylene cap for the subwoofer circuit. Since many on the forum had expressed negative experiences, I also secured the old 2500uF in the new cross over box .... but as it tunrs out the new caps are just great and I will not need to use the old 2500uF caps."

I can see the E-Caps in the photos.   So just to be sure, can you please confirm that the caps used to replace the two big woofer caps are Mundorf 63VDC/23VAC E-Cap Raw? Thanks.

 

 

[kkc]

The 800uF & 470uF caps are Bipolar Electrolytic Capacitors, Etched Foil 63 VDC / 23 VAC  ELECTROLYTIC CAPACITORS.     

The 100uF & 82uF caps are Bipolar Electrolytic Capacitors, Etched Foil 50 VDC / 35 VAC  ELECTROLYTIC CAPACITORS. 

See the pdf for the schema and the cap details Mundorf smooth vs rough.  The pdf is linked in the post I refer to.

You can use cheap caps for bulk and parallel with 10% to 30% expensive polypropylene ones to get better responsiveness.

The Clarity Caps are good value for money.  Whatever you do, do not mix and match too much, always use equal values, same make and model when bundling up.  It will keep resonance affected sound less muddy.

Enjoy...!

    

[harry398]

I read AR pro 's experiences with recapping the Lower range circuit.

I have read a few veteran AR enthusiasts opinion on the original large can Caps.

 

how does my 80mf cap look?      

 

[Pete B]

Looks like it needs to be replaced.

[JKent]

I think the smiley indicates Harry was joking. Better question: HOW did the can get a hole in it?

[harry398]

Upon removal of those cans, I found that was not a hole.   Looks like melt from soldering the coil wire.

 

The plastic wrap around the caps helped shield a bit I guess.......

 

I recapped them, and they sound wonderful

[Pete B]

On ‎10‎/‎12‎/‎2017 at 5:11 PM, JKent said:

I think the smiley indicates Harry was joking. Better question: HOW did the can get a hole in it?

I was joking in return but any NPE that old needs to be replaced anyway.

[DavidR]

On 10/13/2017 at 11:08 PM, harry398 said:

Upon removal of those cans, ......................................................................................................................................

I recapped them, and they sound wonderful

Harry, How about a run down of what you did and what you used for the crossover rebuild?

[harry398]

Sure David

I didnt do Anything extravagant, nor do I think its necessary. 

I installed ALL NPE caps ......except on the tweeter circuit(giving that another shot since I had them sitting in a box).   I did run .01 bypass on all midrange and tweeter caps.

I did install the caps as staggered amounts, not 1 cap, except maybe in one spot.  cant remember for sure, but thats what I remember.   Ill get some pics if needed.....but its nothing special.

 

I find the AR9 is now focused, no static  and most importantly of all  SMOOOTH.   It Improved.  No Doubt.

 

I think people are over thinking and over spending on extravagent caps, NPE do Fine.  To each his own.

 

its my number one speaker, with a very close second to the ar9lsi, which is gaining on the AR9.  the lsi will get ALL new NPE dayton caps in the winter, and replace those yellow turds that are left inside.   The LSI is not as neutral nor as balanced as the ar9, but it offers Great Bass now, with Low LOWS and good SLAM if you desire it.  Overlooked Gem. Needs alot of tailoring.  The AR9 doesnt need that at all.   set up great from the factory, but the Caps needed replacement.