SDA SRS 1.2TL Crossover Upgrade

[Ricardo]

I upgraded the crossovers of my 1.2TL's, and thought of documenting a few things so that others can use this and make their life a bit easier.

The first thing I think is worth mentioning is that you do not need to be an experienced electronics technician, or even have experience soldering. What is required is that you are handy enough. In my case, I had never soldered components in a board. I am a person that likes to fix things and am not scared to learn and adventure in unknown tasks. If you are that type of person, you'll have no problem in doing it. Solder? Easy; you'll get it after a couple of attempts.

Ok. so the first thing you need to do is order the parts you need. This is the list (Amount for two crossovers); Everything from Partsconnexion.com, except for the Polyswitches that you can get from Polk CS.

Capacitors: I used Solen PB and Solen PPE; the difference being just voltage.
(2) 27 uF
(2) 13.5 uF (I piggybacked a 12 and a 1.5)
(6) 12 uF
(2) 0.25 uF (I piggybacked a 0.10 and a 0.15)

(4) 750pF Silver Mica

Resistors: I used Mills 5w
(2) 2.7 ohm
(2) 7.5 ohm
(2) 11.5 ohm (I piggybacked a 2.5 and a 9.1)
(2) 15 ohm
(2) 22.5 ohm (I piggybacked a 2.5 and a 20)

(2) Polyswitches (Polk CS)

Piggybacking: If you need to piggyback as I did, don't make the mistake I did initially..
Capacitors: connect in parallel.
http://www.physics.brocku.ca/courses/1p23/lab-manual/193/node31.html

Resistors: connect in series.
http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.intro.series.html

Thanks to Housedj for the tip!!!

[joeparaski]

Ricardo, do you think I should do this upgrade to my SRS's?...eventually that is....I'm concerned that I'll blow them up.

[Ricardo]

Once your get all the parts, you can get started.

To take the crossovers out, just remove the 8 allen screws that hold them; BE CAREFUL when you get the last one; you'll need to hold the plate, and carefuly pull it towards you until you can fit your hand in. There are three cable connectors that you will need to remove before being able to completely get the crossovers out. Once the three connectors are out, you'll need to turn the plate 90 degrees and work your way out.
The crossovers are held with four plastic "hooks" to the big inductor; You need to remove the two black wires from the inductor and use some fine pliers to get the hooks out.

Pictures: Crossovers with the plate and already removed:

[Ricardo]

The parts you bought are different than the originals; you need to identify them so you know where to put what. I made these diagrams that will help others save the time of identifying everything.

Pictures: Front of Xovers with original parts, and back showing where goes what. I found this very helpful when soldering new parts to make sure I was not making any mistake.

[Ricardo]

The process of taking original parts out is very easy; If you already started practicing your soldering skills you should know how to do it. There is though one part that requires a bit more patience....

The 0.25 uF capacitor that is "piggybacked" with a 0.4mH inductor (The blue cap that is glued to an inductor right below the words "tweeter output" in the board). You must be very careful here to avoid cutting the copper wires from the inductor. Take out all other parts first and leave this one for last; you'll have more space to work.

First, you need to take all the glue out; if you are careful you can separate the glue from the board and then start cutting it (the glue) until you take it all out. Be VERY careful not to cut the copper wires. Once the glue is out, using your solder iron you'll be able to desolder the capacitor from the inductor's copper wires.

Pictures: capacitor/Inductor before and after removing the glue:

[Ricardo]

So you have now a clean board and are ready to solder all the new parts on it. The new capacitors are a lot bigger than the originals, and I don't think there is an easy way to put everything in without getting outside of the board area; I decided to not pay attention to this and instead of mounting the crossover with the plate, I will mount the plate, and clip the crossover to the plate using the passive radiator hole...


Here are a few pictures of the piggybacked caps/resistors; I am particularly proud of the 0.25 (0.15 + 0.10) and inductor; not bad for being my first time :)

Also a picture of the finished crossover.

I hope this helps some others in rebuilding their crossovers.

[joeparaski]

Ricardo, how much $$$$ did all the parts cost??

[Ricardo]

Joe,

For the 1.2TL's it's a bit less than $120, but it will be different for other SDA's. I know there is a thread that talks about the SRS's around here; do a search and you should be able to find it.
What I can say is that it might be more expensive for the SRS's, since the highest cap value for the 1.2 TL's is 27 uF. The SRS's have a few a lot higher than that.

[F1nut]

Looks good!

One thing you might want to add is hot glue. Normally this should be done as you assemble the parts to the board, but you can add some after the fact. The hot glue helps hold the oversized caps in place and helps cut down on vibration related issues.

[pjdami]

Very good job HTrookie. Wow...you got me thinking here now about upgrading the crossovers in my CRS+. Bigtime.

[housedj]

HTrookie you should double check your 2 piggybacked resistors.

11.5ohm does not = 2.5ohm paralleled to a 9.1ohm

those 2 paralled would equal 1.96ohms!!!!! check with a meter before u play,,,you could burn your tweeters

also the 22.5ohm does not = 20ohm paralleled to 2.5ohm
that would be 2.2ohms!!

[schwarcw]

Excellent job HT! Where did the 750 pF silver mica's go? I don't see them. I agree what Jesse said about the hot glue. He gave me this tip and it worked wonders. It stiffened the whole assemblly. Especially the caps that were "floating" of the board. Check out my before and after picture. Notice the hot glue used to stabilize the big caps.

Carl

[george daniel]

The 750pf silvers mica's are in the mail,(excess from my last four x-over upgrades).Looks like you have really spent some time time with those babies,looking good. :)
One question, are you sure about the parrelled resistors? I don't recall having to do that with the 1c's or my brothers 2.3 tl's,not picking atcha :) but you might want to check that,,I'll look in my resistor bag and see if I have any,,if you need them,, just pm me--good job.

[Ricardo]

Jesse,

Thanks; hot glue will be the final "touch".

Housedj:

YOU ARE RIGHT!!!!! Resistors should go in series, not in parallel; should have checked. I just assumed this was right :o :o

http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.intro.series.html

George,

I know many people used 22 instead of 22.5 and so on; Partsconnexion does not have these values; will look somewhere else or connect in series. Where did you buy yours?

Schwarcw:,

You can see where the silver micas go in the "Front" picture of the crossover.

[george daniel]

Ricardo, let me check,I remember when we did the 2.3's, we did not have any issues with resistors,we did use the mills mra5's, I'll pm you when I get back from church,will also see what I have laying around. :cool:

[F1nut]

Housedj, good catch!!!

HT......I think said something about piggybacking the resistors (did I?) and if so that was wrong as you have discovered. They must be in series.

[schwarcw]

Nice HT! I saw where the silver mica's should go I just didn't seem them on the board. Now I know there are on the way! Did you use any tubing to cover the capacitor leads? On my installation, things started to get kind of close in there. Nothing touching, but I installed shrink tubing over some of the leads. I didn't shrink it so I could move it a little after the caps were set in place.

Carl

[schwarcw]

I have a question for Jesse or some of you guys with a background in electronics. Some of the capacitors on the original Polk crossover boards, usually the larger values, have smaller voltages and are crimped on one end. I was told that crimped end capacitors are "polar" therefore having a current "flow path". All of the Solen and Sonicaps I've seen are non polar. Is there any need to give consideration to "polar" style caps? Am I all wet with this information?

CArl

[F1nut]

Electrolytic capacitors are polar, film type (Solen/Sonicap) are not.

[Ricardo]

Housedj, good catch!!!

HT......I think said something about piggybacking the resistors (did I?) and if so that was wrong as you have discovered. They must be in series.

Jesse,
You did not say anything about piggybacking resistors; you did recommend the values to use; post # 8 here:
http://www.polkaudio.com/forums/showthread.php?t=36998&highlight=1.2+crossover

Maybe you assumed I knew they should go in series :)

[Ricardo]

Nice HT! I saw where the silver mica's should go I just didn't seem them on the board. Now I know there are on the way! Did you use any tubing to cover the capacitor leads? On my installation, things started to get kind of close in there. Nothing touching, but I installed shrink tubing over some of the leads. I didn't shrink it so I could move it a little after the caps were set in place.

Carl

No sleeves or tubing; even though it looks crowded, no risk of touching leads.
I saw your crossover is a bit different; what speakers are those?

Edit: And why do I see only one wire going to te big inductor ? :)

[F1nut]

Ah, good. I feel better now. :)

[BobMcG]

Nice job! It was fun wasn't it?

[Ricardo]

Yes, it was fun, and QUICK; in less than three hours I had finished both crossovers; it left me wanting more :)

[StarlightWk]

HtRookie, thanks for ur reply. I will ask Polk C.S. then . Cheers.

[schwarcw]

HT,

My speakers are 2.3's. The big wire (black) was the only wire with the terminal. The other was soldered to the board (underneath). I used Sonicaps on my mod. They are a little larger. Notice I piggybacked two 20 uF to get a 40 uF.

Again nice job. What are your listening impressions?

Carl