1st generation SDA crossover upgrade

ardvark1

The first part of this upgrade was made several months ago by replacing the original SL1000's with the new replacement tweeters. To anyone who is still not convinced, after about 50 hours or so, these new tweeters really shine. I don't see how anyone could go back the their original tweeter after giving this tweeter a proper break-in. Just my humble opinion.

I would like to take a moment to thank darque knight and bluemdpicker, for pointing me in the right direction on this project.
Darque Knight's SRS upgrade posts and compendium proved to be an invaluable source of information. I would like to thank all the members of this forum, you make this a great place to learn, and make new friends.

After reading about the improvements with the SRS line from darque knight's posts, and similar results from bluemdpicker, I decided to apply the same techniques and components on my 1983 SDA 2's to see if I could gain the same benefits. I also used solen pb caps and mills resistors.

The SDA 2's have two separate circuit boards, the bottom board(SDA) mounts to the plastic circular binding post cover, and the top board (stereo)mounts to a large coil directly above it.
It is my understanding that some other SDA's have a similar design (I.E: SDA 1A).

I will skip ahead to the end results. IMO, to hear the full potential of your SDA speakers, the crossover upgrade along with new tweeters is the way to go.
You really do end up with a new set of speakers! The bass and definition improvements are truly amazing. The soundstage has increased, I hear notes/sounds that I have not noticed before.
Over the last month I have been going through my cd collection again, and I am blown away every day. After about 50 hours or so, just like the tweeters, the speakers come into their own.
With the soundstage/imaging improvements, if you own the Polk XM tuner its really a trip. Its one thing the play a cd your familiar with, but when you have someone else making the selections and they get into a groove you like, the speakers can really surprise you when instruments or effects appear all over your listening room. You XM owners know what I mean.

Pictures and notes to follow,,,,,,,,,,,,

ardvark1

Crossovers in the original form.

ardvark1

The top(stereo) crossover mounts on to of a coil which bolts to the speaker enclosure.
The bottom (SDA) crossover mounts to the back of the binding post, and (in my case) fuse holder plate.

The best way to approach this project is to remove all drivers and ps. Label all of your wires and pull them down to the bottom.
Their are three wires that have spade connectors to disconnect the stereo and sda cross overs, and two wires from the interconnect plug.
The sda crossover will come out the rear along with the binding post plate and the stereo crossover and coil come out through the front once you unscrew the single allen bolt in back of the speaker.

ardvark1

Top view of original crossover components.

ardvark1

New components, solen caps, mills resistors, vampire binding posts, etc.

ardvark1

I tackled the stereo crossover first since it involved the most work.
Notice the two small caps end to end. The reason for this is I wanted to use all solen caps and they did not have a 0.5uf cap, so I ran two 1.0uf in series to achieve the same value.
I reused all of the silver mica caps, they are of high quality and Polk recommends re-using them.
Using a glue gun proved a necessity, holding the caps securely in place. You will need to use lead extensions in a couple of places.

ardvark1

Stereo board, top view.

ardvark1

The circuit boards are thankfully quite simple in their configuration. Here is a shot of the back side.

ardvark1

Here is the Sda board layout.

ardvark1

Top view, upgraded SDA board.

ardvark1

The binding posts were upgraded with vampires. Now is the time to replace the binding posts when you have everything torn apart.
The glue gun came in handy once again to seal the connections to the back side of the posts.

ardvark1

Finished product, stereo and sda crossovers ready for re-installation.

ardvark1

Crossover reinstalled in cabinets.
One important note I left out. WHEN POSITIONING THE CAPS ON THE SDA BOARD, HOLD THEM IN PLACE WITH TAPE FIRST AND MAKE SURE YOU CAN WORK THEM BACK THROUGH THE HOLE IN BACK OF THE SPEAKER BEFORE YOU SOLDER AND GLUE THEM IN PLACE. DON'T FORGET THIS STEP!

VR3

Gawd Almighty!

Nice work!

ardvark1

Finished product with tweeter upgrades.
A note on tweeter installation.
Yes the new tweeters are quite abit larger than the SL1000's but don't dispair!
Simply center them and outline them with a pencil. I carefully used a razor knife and worked my way around making a groove the same depth as the original area the stock tweeter mounted.
Then I cut away that area with the knife. It took me several hours to do both speakers (four tweeters) and I then mounted the new tweeters with a small bead of silicone to seal them to the enclosure. If your knife goes astray you can touch the area up with black paint or a magic marker, not to mention your handywork is hidden behind a speaker grill.

I hope this little "how to" has encouraged some of you to give this a try. I do however recommend you have some experience, or have a friend or forum member help you with a project of this level.
I have owned these speakers since they were new, and now they are new once again, but superior to the original in every way.

BlueMDPicker

Thanks for sharing, Bill. Now, I need to hear them all broken in and pumpin'.

Dennis Gardner

What was your upgrade cost of the crossover parts?

ardvark1

Dennis, I ordered several other items and two sets of vampire posts, not to mention if you buy a pound of cardas solder, that will set you back quite a bit, but its wonderful to work with.
I don't have the invoice handy, but with the solder it was over $150 and under $200.
Hope that helps.

jcmccorm

Great work and great pictures ardvark1!!!

Cary

DarqueKnight

Outstanding!!!! Thanks for letting us know how every thing turned out.

Back in the good old days (around 1990), you could actually call Polk Audio and talk to one of their design engineers. It was one of their engineers who suggested mods to improve the performance of my SDA 1B's.

After the mod was completed, I was really surprised at the significant improvement in sound. I called the Polk engineer back and asked him why they didn't do the same mods as part of their normal design process. This is what he said:

1. Premium parts were not always available in the quantities Polk required.

2. They did not want to add additional parts cost to the speakers and "bump up" the price point.

3. Most people who would buy these speakers would be "wowed" by the SDA effect and did not care about the improved performance in detail, imaging, etc.

Tour2ma

Another one for the "reference" file...

Well done...

acdds

How hard is it to do these upgrades? I have the SDA-1B and 2.3TL. I also have no training or experience in electrical circuits or schematics but can solder. I have the compendium but are there posts (by BMDP, Darquenight or anyone else) that go step by step tjrough the process?

Just found BMPD's SRS post. Is the upgrade same in principle for the 1B's but with different parts?

DR. SNOW

Are there upgrade recomendations for SDA-CRS+? I would be very interested if someone had any suggestions on capacitor replacement fo these.

DarqueKnight

Originally posted by acdds
How hard is it to do these upgrades?

It is not "hard", if you know what you are doing, but it is tedious work. If you are not experienced in reading/following electrical schematics and in building/repairing electronic circuits, I would pass. Even with step-by-step instructions, you might run into some unforseen situation that requires some insight to solve. You may want to consider using a repair shop that also does modification work.

Originally posted by acdds
Is the upgrade same in principle for the 1B's but with different parts?

Yes.

DR. SNOW

Darque Knight I see you have done this before on the CRS+ Do you have a parts list still around. Where did you find Caps and resistors. i know they have them available at parts-express. Would this be a recomended source?

Thanks,

Chris

jcmccorm

I bought the caps and resistors for the SRS upgrade that Darqueknight documented from PartsExpress (and they were listed as a source in the original upgrade post).

Cary

DarqueKnight

Chris,

There are two versions of the CRS+: The 1986 version with the blade/blade interconnect cable and the 1989 version with the pin/blade interconnect cable. I have the 1989 version.

Schematics for either version can be obtained from Polks customer service department.

The Mills resistors and Solen capacitors were obtained from:

The Parts Connexion (not Parts Express)
866-681-9602
www.partsconnexion.com


The AudioCap (RelCap) capacitors were obtained from:

Handmade Electronics
610-432-5732
www.hndme.com

The ICW capacitors were obtained from:

DIY Cable
360-452-9373
www.diycable.com

I have not purchased any capacitors or resistors from Parts Express. Their prices were a little bit higher than other vendors at the time I was shopping for parts. I have purchased other types of parts from them and I had good experieces with them. Handmade Electronics had good prices in addition to having a 10% off sale at the time I was shopping for parts.

Take your time and shop around. You can often find deals on parts.

DR. SNOW

DarqueKnight,

Thanks for the info on sources. It was great!! I have the 1989 version with the pin/blade cable. I already have the DCR test and schematics from Ken, so i guess I will start soucing parts. I am not in a hurry to get this done so it might be a while but I'll post some updates as I pregress. Perhaps someone on the forum will be looking for the same mods in the future. I appreciate your time and assistance.:cool:

Chris

jcmccorm

Oops! Major apologies for getting the source wrong on the caps and resistors; Parts Connexion vs Parts Express. Huge difference. Sorry about that.

Cary

Tony M

I just started looking into my crs's I bought a few months ago .
Somebody's been into mine before.
Unnessesary speaker wire jumpers , burnt resistor and hanging wire. Well , I think I have them close to being right but to replace the burned res. I need an ohm rating. The cap. on top of it might not be working either. The teeter came on when I touched a fuse to the bare wires after I cut the burned combo out.This resistor combo was on the speaker hook up cross-over.Nice upgrade by the way. It looks like the combo was replaced with one long cap....Is that right?

Philpfeif

I just comleted the same upgrade on my
SDA 2's and the difference is astounding.It took a while to hit its maximum though. Like about four days of heavy listenng. I am debating buying the 2.3 TL's in Boston. I may have to do it all over again.