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.



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.



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.




The parts list is longer and more expensive than the SDA1As



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

F1nut wrote: »

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

F1nut wrote: »

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

F1nut wrote: »

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

F1nut wrote: »

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

dcmeigs wrote: »

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

ben62670 wrote: »

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

dcmeigs wrote: »

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

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.

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.

Conradicles

How important is it that the 5.8 uf and the 12 uf caps are of the same brand?

Toolfan66

I guess I don't understand why we can't TL the 1C's and use the RDO-198. I would think if you can TL the 2B's you could TL the 1C's..

Just my thought's you guys have been at this a long time, and I am sure if there was a way it would be done..

Face

Conradicles wrote: »

How important is it that the 5.8 uf and the 12 uf caps are of the same brand?

Why would you want to mix them?

mhmacw

F1nut wrote: »

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.

no brainer!

F1nut

I know this is many years down the road, but this thread was referred to recently and I would like to point something out. In dcmeigs' pictures it shows one of the 5.8uF cap leads soldered into the bottom hole of C5 and the resistor soldered into "G" with the other end to the jumper in R2. The resistor connection is ok, but the 5.8uF cap connection is not. The bottom cap lead needs to either be soldered into "H" or if you put the 5.8uF lead into the bottom of C5, a jumper needs to be added between "E" and "H". The way dcmeigs has done it, the 5.8uF is not in the circuit.