AR90 crossover re-cap: Remove board or work in situ?

[Guest nathanso]

I've just removed the woofers and was greeted by a crossover that was twice the size of what I had envisioned (AR folks, chuckle here). Anyway, the boards appear to be (at least) stapled to the speaker enclosures in numerous locations.

What is the best way to remove the boards to re-cap? Or perhaps they are best worked on through the woofer holes, without removal from the cabinets?

[ar_pro]

The staples *can* be carefully pulled out, but the adhesive used on the crossover panels could be a challenge - I'd suggest leaving the crossover in place, and working through the woofer holes.

You might also consider installing spiked feet at this time - your wooden floors will hate you, but the AR-90's will sound great!

[ar90fan]

Try to remove the boards; accordinly to my experiency, it's much more easy to work on it. The problem is that the boards are firmly fixed with grips to the MDF and removal is not easy. I tried to get it with a grip remover in the same way we do with the papers, but it didn't work. Finally, I decided to do it with a screwdriver for bending the grips, and the pliers to remove them. May be you can catch other better ideas to improve the proccess.

SAFETY RECOMENDATION: utilize rubber gloves to protect the skin of your hands, thus avoinding cuts when you strikes the edges of the woofer's holes.

Good luck !

José Cuevas, Spain

[Guest Bret]

>What is the best way to remove the boards to re-cap? Or perhaps they are best worked on through the woofer holes, without removal from the cabinets?<

Rich would have a very good perspective on this. When I was working on the ones I've been in, I remember saying several things my kids shouldn't hear - I was working through the holes and some of those way, way up top are difficult to reach at best.

On the other hand, getting a crossover board to turn loose without snapping can be a challenge; particularly when you can't SEE the staples. And one little "crunch" is all it takes to turn frustration into abject misery.

I would rather be frustrated (and sore) than miserable, so I wouldn't try to remove the boards.

Bret

[r_laski]

>> AR90 crossover re-cap: Remove board or work in situ?" <<

Nathanso,

My take:

When I rebuild crossovers, I leave the original boards attached. If you replace your original caps with polypropylene caps (recommended), the new caps will be significantly larger than those currently installed. This causes a problem with placement of the caps on the current boards.

What I do is carefully remove all the components from the original board and leave the board attached to the cabinet. I use Masonite pegboard to rebuild the crossover. This allows me to spread the components out and fit the replacement caps into the crossover. When rebuilt, I use “liquid nails” to adhere the new board to the old.

You can make the replacement boards much larger; you just need to determine the largest length and width you can fit through the woofer holes.

The AR-90 bottom board is easier to rebuild, as you just have to attach it to the original board.

When laying out the component location on the back board, you must start with the location of the binding posts and equalization switches. Position these so they will exit the existing holes in the original back board and all the other components can the positioned accordingly. (I eliminated the equalization switch network portion of the AR-90 crossovers I rebuilt, so I only had to line up the binding post holes. I plugged the switch holes with black plastic caps I found at Lowe’s).

http://www.classicspeakerpages.net/dc/user_files/337.jpg

Here is a picture of an AR-11 crossover I rebuilt on Masonite pegboard using the techniques I mentioned above. I countersink the brass screw heads and use liquid nails to permanently attach them to the pegboard. Capacitors and inductors are attached with silicone caulk. Capacitors are secured with wire ties. Those are brass (non-ferrous) screws, washers, and nuts securing the inductors.

One other recommendation,replace the binding posts. There are much better binding posts available than the screws, washers, and nuts used by AR.

Rich

[rrcrain]

Having rebuilt my AR90 crossovers, I would suggest removing them. They are glued and stapled, but the staples are short and the glue was pretty well dried out making all 4 boards very easy to remove.

[Guest nathanso]

I finished the first speaker last night, working in situ, in about 2-hrs.. no sweat. I'd rate this a 6/10 on the difficulty scale assuming you have soldering skills and a few basic tools.

Thanks to José for recommending the use of gloves. I used blue painter's masking tape around the inside of the speaker cutouts which undoubtedly saved me from nasty splinters.

I used Bennic NPE's from Madisound on the five largest caps and Carli mylars on the three smaller ones, also from Madisound. Total cost for both speakers: $30. The 350uF was replaced by a 200uF and a 150uF in parallel. The 24uF was replaced by two 12uF's in parallel. The 4uF was replaced by a 3.9uF Carli.

In the interest of maintaining originality and a backwards path to remove my mods should I ever want to -- not to mention simplifying this job -- I elected to leave the old capacitors in place and simply cut one lead from each. In the case of the axial lead caps (6) I also bent the cut lead out of the way. The big 350uF and 80uF caps now have one terminal with no wires going to it. In both cases (350 and 80) I clipped the wire from the terminal with the fewest wires going to it and then utilized the other terminal as a binding post for its existing wires and my new cap lead. Note that I needed no new wire in this re-capping job; only the leads of the new caps.

Here are some techniques that helped:

o Use a pencil style soldering iron, not a pistol style. 30W is all you need. This allowed me to reach the inner recesses of the cabinet without melting unwanted components.

o Use a hot glue gun to secure the new caps in place thus preventing unwanted vibration. I'll try to add some before/after pics of my part placement later.

o Use a small pair of flush cutting wire cutters like RS Catalog #: 64-2959.

o Place the speaker upright on a table to work on the bottom board; then lying on its back to work on the upper board. The 40uF on the upper board is accessible via one woofer hole; all the others on the upper board are best accessed via the other hole.

o Get a gooseneck lamp and shine it in the hole you're not working through.

How do they sound?! I don't know yet as my drivers are still being re-edged! I've deliberately re-capped only one speaker as I plan on A/B testing the old vs new caps before re-capping the second one. Stay tuned.

[Guest nathanso]

My AR90's are back together and sounding better than ever.

I paused between recapping speaker #1 and #2 to do an A/B test. In my listening room, an A/B test uses a Niles SPK-1 remotely actuated A/B switcher so I can be sitting in the sweet spot while I rapidly flip back and forth from A to B.

In this case I was running my pre-amp in mono, left channel into the re-capped AR90, right channel into the original capped speaker. My wife was sitting next to me for a second opinion.

It took all of 20-seconds and 3-4 switchovers to identify the re-capped speaker as sounding obviously better. It's bass was tighter, its vocals clearer, and overall smoothness better. The original speaker sounded hollow, as if it was playing through a short length of sewer pipe; its bass was loose and undefined.

Here's my shopping list from Madisound if anyone is interested:

Qty--Item#--Desc--Price

2--M3.9--Carli 3.9mfd Mylar--$1.15

2--M6--Carli 6mfd Mylar--$1.50

2--M8--Carli 8mfd Mylar--$1.95

4--M12AL--Bennic 12mfd electrolytic--$0.65

2--M31--Bennic 31mfd electrolytic--$1.00

2--M40--Bennic 40mfd electrolytic--$1.20

2--M80--Bennic 80mfd electrolytic--$1.70

2--M100--Bennic 100mfd electrolytic--$1.90

2--M250--Bennic 40mfd electrolytic--$3.60

The 3.9 replaces the original 4. The 31 replaces the original 30. The two 12's in parallel replace the original 24. The 250 and 100 in parallel replace the original 350. I used hot glue to make a capacitor Oreo cookie on those paralleled parts before installing them. Each capacitor (or glued pair) was then either hot clued to the board or hot glued piggyback style on top of the original cap it was replacing.

About 2-hrs work-time per speaker working through the woofer holes. For me, removing the boards was not the answer as it would have taken far longer. If you're not comfortable soldering in close quarters, however, my method may not be for you. With either method you should consider leaving the original parts in place (with leads clipped) as their removal seems unnecessary unless intra cabinet aesthetics matter to you.

[rrcrain]

Given the old parts were only held in place with dried out glue or some other adhesive, removing them was not an issue for me. Some might argue that you changed the internal volumn of the cabinet by leaving the old parts in place; by what factor I've no clue.

At the end the day all that really matters is that your happy with the results.

[dynaco_dan]

>My AR90's are back together and sounding better than ever.

>

>My wife was sitting next to me for a second opinion.

An excellent choice having a partner who shares in your interest and helps you as well.

>It took all of 20-seconds and 3-4 switchovers to identify the

>re-capped speaker as sounding obviously better. It's bass was

>tighter, its vocals clearer, and overall smoothness better.

>The original speaker sounded hollow, as if it was playing

>through a short length of sewer pipe; its bass was loose and

>undefined.

>

>Here's my shopping list from Madisound if anyone is

>interested:

>

>Qty--Item#--Desc--Price

>2--M3.9--Carli 3.9mfd Mylar--$1.15

>2--M6--Carli 6mfd Mylar--$1.50

>2--M8--Carli 8mfd Mylar--$1.95

>4--M12AL--Bennic 12mfd electrolytic--$0.65

>2--M31--Bennic 31mfd electrolytic--$1.00

>2--M40--Bennic 40mfd electrolytic--$1.20

>2--M80--Bennic 80mfd electrolytic--$1.70

>2--M100--Bennic 100mfd electrolytic--$1.90

>2--M250--Bennic 40mfd electrolytic--$3.60

>

>The 3.9 replaces the original 4. The 31 replaces the original

>30. The two 12's in parallel replace the original 24. The 250

>and 100 in parallel replace the original 350. I used hot glue

>to make a capacitor Oreo cookie on those paralleled parts

>before installing them. Each capacitor (or glued pair) was

>then either hot clued to the board or hot glued piggyback

>style on top of the original cap it was replacing.

>

>About 2-hrs work-time per speaker working through the woofer

>holes. For me, removing the boards was not the answer as it

>would have taken far longer. If you're not comfortable

>soldering in close quarters, however, my method may not be for

>you. With either method you should consider leaving the

>original parts in place (with leads clipped) as their removal

>seems unnecessary unless intra cabinet aesthetics matter to

>you.

Hi there;

Thank you for being so detailed with your step by step procedure.

You are not the only person, to want to, or even do what you did inside those very cramped quarters.

By providing what parts and techniques you used, and the prices it gives us all hope of being able to also make changes without breaking the bank if we should decide to proceed as well.

Thank you again.

[Guest nathanso]

Before and after pics of the top board.

http://www.n8software.com/ar/IMG_6227.JPG

http://www.n8software.com/ar/IMG_6236.JPG

[Guest David in MA]

Thanks for your detailed work. It helps quite abit as I'm about to recap my AR-9's. I gather from your list of caps you ordered from madisound, you didn't bypass any of the caps? I've been told it makes noticeable difference especially in the tweeter driver.

Also, any reason why you stuck w/ electrolytes rather than polys?

> The 31 replaces the original 30.

Just wondering if 3% cap value difference is ok with the overall crossover output. Most likely it shouldn't be a problem but if anyone can comment, that'd be great.

Thanks.

[Guest Bret]

>Just wondering if 3% cap value difference is ok with the overall crossover output.<

Should be. The original parts were +/- 10%. There was a fairly large spread possible.

If you get into the audiophilia of it all, folks will say that tiny differences do things to "imaging."

Personally? I wouldn't worry about 3%.

Hope that's helpful.

Bret

[Guest David in MA]

Bret,

Yeah, I'm not going to stress out over it.

Thanks.

BTW - what values of caps did you use in tweeter bypass? Just wondering because I can't find small enough caps for 4 and 8 uF caps...

[Guest Bret]

>what values of caps did you use in tweeter bypass?<

.22uF

Bret

[Guest nathanso]

> Also, any reason why you stuck w/ electrolytes rather than polys?

Partly due to Skepticism, partly due to price. Bret from this forum counseled me to use (at least) mylars on the smaller caps where capacitor composition makes more of a difference. I spent $30 total; All Solens would have cost $280 or so, and that's before bypassing. While I'm slowly coming around to the virtues of polypro caps over NPE's and mylars, I'm still a ways off from accepting bypassing, though others, I know, swear by the practice.

[Guest David in MA]

>> Also, any reason why you stuck w/ electrolytes rather

>than polys?

>

>Partly due to Skepticism, partly due to price. Bret from this

>forum counseled me to use (at least) mylars on the smaller

>caps where capacitor composition makes more of a difference.

>I spent $30 total; All Solens would have cost $280 or so, and

>that's before bypassing. While I'm slowly coming around to

>the virtues of polypro caps over NPE's and mylars, I'm still a

>ways off from accepting bypassing, though others, I know,

>swear by the practice.

Bret was very helpful in giving me all the in-and-outs of recaping...I settled on Solens but I couldn't find 250V solens...I didn't want to stay with 400V solens because the experiences of other in these forum. I may go your route and then upgrade later and see if there are actual differences....

Thanks.

[Guest David in MA]

>>what values of caps did you use in tweeter bypass?<

>

>.22uF

Hmmm, so do you think using 0.22 uF in || with 4 uF is ok?

[Guest Bret]

>Hmmm, so do you think using 0.22 uF in || with 4 uF is ok?<

Sure. Maybe a .1 would be better - at three times the price - but I haven't done that. Oh, I did make sure my 4uFs were 4uF. If they had been 4.35uF, I wouldn't have added .22uF.

Bret