SDA2 Upgrade Project

Marty913

For those interested, here are some pictures & comments about the recent crossover, binding post, and interconnect upgrade on my SDA 2’s.

My intent in this upgrade was twofold. First, I had have not soldered anything in years so it was a chance to re-learn things. I have a pair of SDA 1C’s that are currently my main speakers and chose not to practice on them. The 2’s have four crossovers so I figured that would be a lot of practice. Secondly, I was curious about the “sonic” differences between the before & after and thought the “dimensional tweeter” added a nice twist.

Just so we don’t get into component quality, my basic goal was an inexpensive upgrade. Not cheap, mind you – just less expensive given the four crossovers and the inherent value of plain SDA2’s versus SDA 1C’s. For that reason, I chose Solen Caps and Mills Resistors along with parts I had laying around (banana plugs, wire, etc.). Not the cheapest upgrade but definitely not the most expensive. The goal was to cost-effectively modernize 21 year old speakers that I will eventually use as surrounds.

Yes, I will probably upgrade the tweeters next but wanted a comparison of each upgrade so it’s a one-step-at-a-time and listening thing.

One thing I did not get done (yet) is to put in a toggle switch to turn the dimensional tweeter on and off. I’m having trouble finding a toggle with a long enough shaft. I’ll get to it eventually.

My thanks to all those upgrade contributors and posters that inspired me to take a shot at this. The soldering video links from Ricardo were handy, as was the upgrade project post from DarqueKnight. A special thanks to avguytx whom I could not have done this without. He in fact even offered to “do it for me”, helped me get the right parts, and bailed my out of a couple of soldering mistakes. Also thanks to nspindel for moral support, a couple of spare tweeters, and help in getting the pictures uploaded.

Here’s basically what I did:

1. Replaced all the basic caps & resistors and eliminated the Mica’s
2. Eliminated the Poly-switches and replaced them with wire jumper
3. Replaced the Input connectors with better jacks
4. Added a set of banana jacks into the binding post cup and wired them into the SDA interconnect jack. That way I could upgrade the interconnect cable quality but still maintain the usability of the original blade/blade connector
5. Replaced a few suspect connectors, wire runs, etc.
6. Eliminated a few vibration rattles (hot glue)

There are two other posts with parts costs, and basic methodology.

Speakers in question



Original Crossovers



Close-up after removal



After pulling the right cabinet crossovers, I added the new Binding Posts for the Interconnect Cable. The new jacks allow cable experimentation but still leave the IC jack intact. New jacks get 14-gauge to the crossover.


Inside View Right Speaker (Left would be reversed)



Back to the completed Stereo crossover



Poly-switch now replaced with wire jumper



SDA crossover complete



Assembly begins, completed bind post cup



One mounted, One ready to mount



Testing and Checking for Fires

Marty913

Parts List for upgrading SDA2’s

I used Solen capacitors and Mills resistors from Part Connexion. Obviously you may choose others. Here are the qty, description, SKU, and total price for all 4 crossovers and the binding posts.

4 Solen 12.0 400v PB (51556) $22.84
4 Solen 27.0 400v PB (55885) $40.56
2 Solen 0.47 630v PPE (51544 $3.52
4 Mills 2R7 MRA-5 (64619) $8.60
4 Mills 3R5 MRA-5 (68109) $8.60
1 Pair Connex 5-way Binding posts (53466) $4.75
Total Cost: $88.87

What Else You Need
1. Usual assortment of screwdrivers, wire cutters, wire strippers, and electrical tape.
2. Soldering iron/gun (30W Radio Shack $10) and solder ($5).
3. De-soldering pump or bulb (Radio Shack for about $10).
4. Various sizes of wire connectors to replace bad ones. You can buy an assortment kit for around $10 - $15 dollars.
5. I replaced some “suspect” internal wiring plus my interconnect and binding post wires so if you do that you need some 16-18 gauge wires.
6. A Hot Glue gun ($10 or less at Wal-Mart or similar. I found this invaluable for tacking down wires, fixing broken nylon post clips, insulating binding posts, and stopping potential rattles.

Marty913

If you are thinking about upgrading your SDA2’s, this may help you. It really isn’t so much for the forum veterans, just something simple if you’ve never done it (like me).

If you need more and you can read Microsoft Excel spreadsheets, I can email you positional layouts of each crossover and the connections and the Interconnect Jack polarity swap. I also have some simple Ohm readings you can use for testing before you damage anything.

One speaker at a time and use the other for reference if you get into trouble.
1. Remove the Passive Radiator, mid-woofers and tweeters. I left the wires in each hole until I had noted where they went to on the crossover. As you unplug the crossover quick connects mark every connection or draw a picture for later reference. I also took pictures with a digital camera.
2. The stereo crossover (top one) sits on top of the inductor and is held by four nylon clip mounts. The inductor is held in by a bolt to the rear of the cabinet. I found that turning the bolt with an Allen wrench would not remove it because the nut inside the inductor was glued. If that’s your case, squeeze each nylon clip mount while gently pulling up on the crossover. Once the crossover is loose you can move it out of the way and free the inductor retaining nut. Leave the two wires from the bottom side of the crossover to the inductor attached and lift the inductor and crossover out of the cabinet.
3. The SDA crossover (bottom) is much easier (no inductor). It attaches with four nylon clip mounts to the back of the Binding Post cup. By removing the four Binding Post screws on the rear of the cabinet the entire assembly can be pulled out the rear of the cabinet.
4. Each nylon clip has two small “wings”. Squeeze them while gently pulling up on the crossover and it will come loose. I found it easier to clip the two inductor wires on the stereo crossover and separate the two. There is room to do the upgrade with the inductor attached but it gets in the way. It’s your choice. The SDA crossover has to be detached from the Binding Post cup if you are using Solen or Sonicap capacitors. Their larger size makes it difficult to pass the SDA crossover / Binding Post assembly back through Binding Post hole.
5. Remove (de-solder) all the components to be replaced (12uf & 27uf caps, .5uf Mylar cap/ 3.5 resistor, and the 2.7 resistor). Replace with new leaving out the small silver mica caps on the 12uf & the 3.5 resistor. They are not needed. I replaced the small blue poly-switches with a16 gauge sold core wire jumper. See pictures for one possible layout.
6. After doing the two crossovers, I tackled the Binding Post upgrade which is pretty straightforward because I was using similar posts. I just wanted to move to gold-plated ones so I used standard 5-way dual binding posts (Connex from Parts Connexion $4.75 a pair). The existing holes for the Polk binding posts line up fine although the Connex requires one drill bit size larger. That’s pretty much it, just slide them in.
7. Note: I also added a second set of Posts for an SDA Interconnect Cable replacement. The wiring is NOT intuitive so if you are also doing that you may want to email me.
8. Note: I did bench testing and multi-meter checks before re-assembling everything. It isn’t necessary but I figured re-assembly would require hot glue here and there. If I screwed up a solder connection, I would rather catch it before everything was back in place. As it turned out, I did screw up and found it with the multi-meter (requires hooking up drivers on the bench to created measurable load so it’s a pain). It did save me a LOT of trouble.
9. Re-assembly starts with installing the Binding Post cup (without the new SDA crossover attached yet). Pretty simple, just four screws.
10. Mount the Inductor / Stereo crossover assembly next so the Binding Post cup is available. Once again, just move the crossover off to one side, slide the inductor on the bolt and tighten the nut. Now slide the crossover back in place and push it down over the nylon clip mounts. You can route all the stereo driver wires to the appropriate holes and connect the white binding post wire.
11. Attach the SDA crossover black binding post wire to the Binding Post along with the Stereo black binding post wire. The Binding Post cup is finished now so you can hot glue it if you want (prevents shorts due to vibration).
12. Now mount the SDA crossover to the nylon clip mounts and press down to lock. Reconnect the interconnect cable leads and route the SDA driver wires to the appropriate holes.
13. Install / connect all the drivers (leave the passive radiator off).
14. Test
15. Install the passive radiator.
16. Do the other speaker.

danger boy

good work.. but hey do they sound newly refreshed?

Marty913

danger boy wrote: »

good work.. but hey do they sound newly refreshed?

They were damaged when I got them and cutting in & out so I never really heard them in all their "former glory". Right now they sound good after about 8 hours of break-in. The SDA effect seems stronger as does the overall bass. I'm not too sure about the dimensional tweeter. It may have to go. I've tested my installed IC jacks but not really done an A/B comparison on that yet.

Joe08867

Very Nice.

Enjoy them in there new found glory. And wait until you change those tweeters. Oh so Good,

I plan on doing this to my SDA2's. I have first series ones like you but I had the SL1000 tweeter. They sucked pretty bad.

Marty913

Joe08867 wrote: »

Very Nice.

Enjoy them in there new found glory. And wait until you change those tweeters. Oh so Good,

I plan on doing this to my SDA2's. I have first series ones like you but I had the SL1000 tweeter. They sucked pretty bad.

Thanks, I was pretty happy with the way they turned out. At least I didn't burn them to the ground with the soldering iron. They are sounding a lot better BUT I'm already curious about building "direct connect" crossovers for them (interchangeable components with little or no soldering). The dimensional tweeter is sort of a waste but converting it to an "array" like the 1C's - that might be interesting. I know, they're aligned the wrong way but it might beat turning it off.

One thing I don't regret is the new interconnect posts. A bargain at less than $5 and I'm using 12 gauge wire for an IC cable.

nspindel

Just noticed this thread, don't know how I missed it - great work!!!!

schwarcw

Very nice Marty! The crossover and tweeter upgrades to the SDA's are so much fun. I like the interconnect binding posts that you installed, great idea! I always wondered about building a better crossover board. Congrats and enjoy!:)