Photos of the upgrade for the SDA 2Bs

[dcmeigs]

I came home from an evening listening to my buddy's recently moded SDA1As with a Rotel transport and DAC, a Hafler pre and a 200W Hafler amp, and guess what, my SDA2Bs didn't sound so good anymore. What's up with that?

So this morning I got off my arse and did the deed. This is what is known as the 4.1TL mod (ed. F1nut informes me it's the 2BTL) as it has the 5.8uf cap to accomodate the RD0198 tweeters.

http://i297.photobucket.com/albums/mm212/dcmeigs/SDA2BCrossoverLayout.jpg

The job on the 2B is much, much simpler than the 1A because you only have one board per speaker and the boards have plugs for all of the wiring so you don't have to remove the speakers to disconnect the wires. The 2Bs use 16 gauge wire which I am comfortable with as opposed to the 18 ga which I felt needed to be replaced in the 1As.

http://i297.photobucket.com/albums/mm212/dcmeigs/2BProfile.jpg

The 5.8uf, 12uf and 20uf caps fit in nicely but the 30 & 10 are another matter, but there is enough room in the cabinet for this arrangement.

http://i297.photobucket.com/albums/mm212/dcmeigs/SDA2BXover.jpg


The parts list is longer and more expensive than the SDA1As

http://i297.photobucket.com/albums/mm212/dcmeigs/SDA2BParts.jpg

I hope these photos will help the next guy. You would not believe me if I told you how simple this was and how quickly this happened. I did one late afternoon yesterday and another this morning. It's not even 11:00am and that includes time to photobucket the photos and make this post. Of course it took a lot longer than that to talk about it and order the parts.

Thanks to everyone on the board who took time to educate me.

Dave

[ben62670]

Very nice.
Enjoy.

[Face]

Great job! If I decide to hold onto my 2B's, I plan on doing the same thing.

[danger boy]

nice work.. let them burn in for say.. 60 - 80 hours.. and see if you hear some improvement.

at some point down the road I want to do the same to my 2B's too.

[F1nut]

This is what is known as the 4.1TL, I believe (although I don't know why), as it has the 5.8uf cap to accomodate the RD0198 tweeters.


Polk intended to upgrade the CRS+ and call it the 4.1TL. However, production ceased before that happened. Anyway, the schematic for the 4.1TL conversion was published and some of us decided to try it. Along the way, it was discovered that the same mod could be done to the pin/blade 2B. However, it can't be called a 4.1TL as that name is already taken, so we've been calling it the 2BTL.




For anyone else down the road looking at this, but planning on doing it to a pair of CRS+ speakers. You have to mount the 30uF cap vertically on top on the board and mount the 10uF under the board as there is a serious lack of real estate in the CRS+ cabinet. You can't mount them as dcmeigs has.

[dcmeigs]

Polk intended to upgrade the CRS+ and call it the 4.1TL. However, production ceased before that happened. Anyway, the schematic for the 4.1TL conversion was published and some of us decided to try it. Along the way, it was discovered that the same mod could be done to the pin/blade 2B. However, it can't be called a 4.1TL as that name is already taken, so we've been calling it the 2BTL.




For anyone else down the road looking at this, but planning on doing it to a pair of CRS+ speakers. You have to mount the 30uF cap vertically on top on the board and mount the 10uF under the board as there is a serious lack of real estate in the CRS+ cabinet. You can't mount them as dcmeigs has.

Thanks for the explaination; and for the encouragement.

After nearly 2 weeks of continuous play, the recently moded SDA1As continue to improve. It's made quite an impression on me.

On their web site, AQ discusses the capacitance of interconnect cables and describes thier run-in time. They claim that the cables return to their original state after a long period of disuse, thus requiring another run-in period. I wonder if the same applies to the polyproplyene film caps?

[F1nut]

I wonder if the same applies to the polyproplyene film caps?

In my experience, no it doesn't.

[dorokusai]

That's nice work.

[dcmeigs]

On more thing. Loose the Safetyguards. One shows 1.1 ohm resistance, the other 2.2. How's that for a balanced sound? You can always buy a new tweeter if the Huns come over and crank it up too loud.

Oh yeah, all you Huns on this board, I'm taking about the other Huns. You're OK by me.

[MillerLiteScott]

Polk intended to upgrade the CRS+ and call it the 4.1TL. However, production ceased before that happened. Anyway, the schematic for the 4.1TL conversion was published and some of us decided to try it. Along the way, it was discovered that the same mod could be done to the pin/blade 2B. However, it can't be called a 4.1TL as that name is already taken, so we've been calling it the 2BTL.




For anyone else down the road looking at this, but planning on doing it to a pair of CRS+ speakers. You have to mount the 30uF cap vertically on top on the board and mount the 10uF under the board as there is a serious lack of real estate in the CRS+ cabinet. You can't mount them as dcmeigs has.

Here is an example of what Jesse is talking about and his work.

[schwarcw]

Very nice work! It's actually a thing of beauty!

I've done that same acrobatic maneuvers with the big Sonicaps mounting on that same board. Fun stuff, I haven't done my original CRS. Too many other projects.

[F1nut]

Damn nice work there, Scott. ;)

[MillerLiteScott]

I have to agree. That's the way to do it.

[strider]

Polk intended to upgrade the CRS+ and call it the 4.1TL. However, production ceased before that happened. Anyway, the schematic for the 4.1TL conversion was published and some of us decided to try it. Along the way, it was discovered that the same mod could be done to the pin/blade 2B. However, it can't be called a 4.1TL as that name is already taken, so we've been calling it the 2BTL.



Isn't it possible to do the upgrade on blade/blade 2B like mine, if you run a ground internally from the small blade to the negative binding post?

[F1nut]

Absolutely, except you want to run that wire from the large blade.

[dcmeigs]

Absolutely, except you want to run that wire from the large blade.

I meant to ask you about the negative to large pin strap that is notably absent on the SDA2B -bb (blade-blade) design.

I decided that it was probably not needed because the negative terminals are connected through the common ground amp. Am I missing the point?

I see they are connected on the CRS+ drawing so someone must have thought it beneficial.

Fill me in, please.

[F1nut]

I'm not sure why that is on that model, but they work fine as long as you use a commom ground amp.

[ben62670]

I meant to ask you about the negative to large pin strap that is notably absent on the SDA2B -bb (blade-blade) design.

I decided that it was probably not needed because the negative terminals are connected through the common ground amp. Am I missing the point?

I see they are connected on the CRS+ drawing so someone must have thought it beneficial.

Fill me in, please.

On the blade/blade you can't just ground the ground wire. The hot of the right gets sent to the negative of the left, and vise versa.

[F1nut]

I'm not following you Ben. There should be no problem adding a wire from the large blade socket to the negative binding post. Every other SDA, be it blade/blade or pin/blade, is connected that way except these.

[ben62670]

On pin/blade the signal travels through the drivers first before being sent to the opposing channel. On Blade/blade the signal is sent directly to the opposing channel. If you bypass either blade to ground it is a dead short. Unfortunately I learned this the hard way:o

[dcmeigs]

On pin/blade the signal travels through the drivers first before being sent to the opposing channel. On Blade/blade the signal is sent directly to the opposing channel. If you bypass either blade to ground it is a dead short. Unfortunately I learned this the hard way:o

Ben,

I think you are confusing the SDA1A (with its 2 blade IC) which does as you describe with the 2B which only uses one of the two wires. The top lug is unwired. A quick look at the other bb designs show that the large blade is strapped to the (-) post.

BTW, there is a local pair of AAL-154s for almost free in good shape. Have you ever given them a listen?

[ben62670]

Ben,

I think you are confusing the SDA1A (with its 2 blade IC) which does as you describe with the 2B which only uses one of the two wires. The top lug is unwired. A quick look at the other bb designs show that the large blade is strapped to the (-) post.


Actually the the 2b b/b is the exception to the rule. Most B/B's are not strapped to the ground, but have either caps in-line, or an inductor in-line. Glad you guys caught that. Polk liked to use up stocked parts in between design changes.

[F1nut]

Yeah, I can't see any difference in the 2B b/b crossover vs the 2B p/b crossover except the missing ground wire on the b/b version. They would have added that wire to the p/b version in able to use the AI-1.

[ben62670]

Thanks F1

[Lasareath]

Dcmeigs,

Very nice Job on those crossovers, they look Great!

I like those crossovers and how much open room there is. When I did mine it was pretty tight.

Now it's time to relax and enjoy your well done work!

Sal

[george daniel]

Sal,, what are the black colored caps? Mundorf's? Nice job BTW.

Very nice work dcmeigs,,, Sonicaps and Mills ,,,music to my ears.

[Lasareath]

Sal,, what are the black colored caps? Mundorf's? Nice job BTW.

Very nice work dcmeigs,,, Sonicaps and Mills ,,,music to my ears.

Yes, Mundorf's, I fugured if I was going to add a cap to my tweeters like candy does it should be a Mundorf! ;)

[F1nut]

Make note. Do not cover the resistors in hot glue. They get hot, they have to get rid of the heat to function properly and the hot glue isn't helping.

Sal, I know you removed the hot glue. I commenting to prevent others from doing it.

[Lasareath]

Make note. Do not cover the resistors in hot glue. They get hot, they have to get rid of the heat to function properly and the hot glue isn't helping.

Sal, I know you removed the hot glue. I commenting to prevent others from doing it.

I hear you Jesse, Me and Joe went a little nutso when we did my crossovers.

I bought all new Mills Resistors and cut out those 2 week old resistors and soldered in new ones!