SDA-2 Crossover Upgrades Completed

[schwarcw]

Several weeks ago, with the help of my long time friend Bill, I completed an upgrade of the crossovers on my SDA-2’s. I used a thread by Aadvark1 as a guide for my project. Aadvark1’s thread was extremely valuable to me in this project. [thread] http://www.polkaudio.com/forums/show...tion+Crossover [/thread] Aadvark1, thanks a million! With Aadvark1’s permission I am going to use several pictures of the “before” pictures of the crossovers. I didn’t take any before shots since Aadvark1’s were so good. Aadvark1 use Solen caps and Mills resistors for his upgrade. I decided with a lot of angst to go for the more premium Sonicap capacitors. These caps represented a significantly larger investment over the Solens, which are popular among Polk members performing these mods.

I made my decision after several conversations with Jeff Glowacki at SonicCraft. Jeff immediately impressed me with his knowledge of speaker crossovers and his experience with capacitors in these circuits. Jeff’s primary message was to eliminate the fuse protection as these were viewed as the weakest link from the sound source to the crossover boards. My tweeter fuse filaments were smaller that the diameter that a typical human hair. Barely visible under light with my glasses removed to view up close. According to Jeff “Why people are spending good money on thick speaker wire, expensive cable, only to be limited by this tiny wire is beyond me. By pass those fuses with a solid copper wire and you should notice an immediate improvement”.

The other departure from the Polk schematic was to eliminate the 750 pf silver mica by pass capacitor from the 0.5 uF capacitor and the 12 uF capacitor. The 750 pF by-pas capacitor from the 0.5 uF capacitor was eliminated completely. For the 12 uF capacitor Jeff recommended replacing the 750 pF by pass capacitor with a 0.1 Gen II. The elimination of the 750 pF by-pass capacitor was also a hotly debated discussion with in the Forum [thread] http://www.polkaudio.com/forums/showthread.php?t=32685 [/thread] He recommended the Gen II over the Gen I. He felt the Gen I might be a little too transparent and the Gen II might offer a little color that you might expect from a tube amp source. Since I was using solid-state equipment, Jeff thought this might be a better choice, offering a softer cap with a little color.

I chose the Mills MRA-5 resistors and the Vampire brand binding posts. When I received the Sonicaps I was a little alarmed at the size of these caps compared to the Polk originals and the Solens. My fear was these caps would have a hard time fitting through the back of the speaker cabinet into the speaker enclosure. I decided to go for it.

I have attached several pictures depicting the comparative sizes of the original caps vs. the Sonicaps. We removed all of the speakers, carefully numbering the wire leads and the speaker terminal. Little adhesive numbers worked great for this labeling process. We had no trouble soldering the new components to the boards of fitting the newly assemble boards into the cabinet. The size of the cap left us a few blind spot for reattaching the wires to the spade lugs. Additionally, I used ring terminal to attach the main leads to the binding posts as opposed to soldering these wires to the new Vampire binding posts. I used the steel ring terminal, as I didn’t want to spend all afternoon trying to run down some gold ring terminals. All the boards and components went back together without much effort. Bill had a nice set of hobby tubes of various diameters that were very useful to compress the plastic “trees’ that held the circuit boards to the mounting blocks that attach to the speaker cabinets. These allowed effortless removal of the boards without the use of pliers or other hand tools. The whole project took about 5 ½ hours with the two of use working together. The attached pictures show the original boards, a side beside view of the original capacitors with the new Sonicaps, a picture of the SDA board assemble with the new Sonicaps, and a look inside the cabinet with the refurbished boards installed.

I notice a change in the sound of the speakers immediately. Initially, it was not profound. I noticed a wider soundstage and more punch to the bass. The midrange was more detailed. I was happy. However after more than 50 hours of “burn in” of these components, the changes are much more pronounced. Greater detail, softer detailed highs, more bass and overall a moderate improvement. I have very happy with the results. Whether or not I would have realized a similar or even beer improvement with the less expensive components is a mater of debate that I cannot offer any objective opinion. I am very satisfied with this result and would recommend these to any SDA owner contemplating this upgrade. The overall cost of this upgrade with Sonicaps, Mills resistors, Vampire binding posts, postage etc. was a little under $300. This upgrade could have been done with Solens, Mills and Vampires for about $100, or the cost of my upgrade was about three times the typical upgrade done by may other Polk owners doing the same project.

Your comments and feedback are welcome! Enjoy the pictures and happy listening!

[F1nut]

Good write up.

I think we're missing some of the pics and I'd like to point out that the Sonicaps are the same size as the Solens, that is huge, compared to the stock.

[djf]

Congrats!

I just spent 4 hours fighting what I thought was a destroyed crossover on my SDA-SRS's.

Cold solder spot when I installed the new polyswitches, gave out after about 2 hours of tunes.

I'm close to being near ready to almost decide to maybe spend 400 bux on the RDO tweeters, but have heard no objective sound reports.

[ND13]

I'm close to being near ready to almost decide to maybe spend 400 bux on the RDO tweeters, but have heard no objective sound reports.

As the Nike commercials says.........JUST DO IT!!! :D

[djf]

The silver coil SL2000's are still highly sensitive and accurate tweeters. I admit I do like a sound that is a bit brassy, somewhat harsh, but I really like the dynamic response.

Current: The Song Remains the same dvd by LZ.

I was worried because the polyswitches that got sent dont match the ones I took out, and the crossover schematic are not for the SRS's, so I was worried I fried something, but turned out OK.

But I need to put a new fuse into one of my Kenwood amps (both of these are real Kenwoods, back before they went to Hades), so now I'm only running on a measly 100WPC into 8, which is probably a good 130.

I come here because my system is a big investment, still better than any other system I ever heard, and I need technical advice on how to keep it up.

But I've been exposed to a bit too much of the "You're only running 200 wpc SS watts?" kinda attitude.

Page is beating the crap out of his guitar with the violin bow now...

[schwarcw]

I had trouble loading some of the pics I had because the file sizes were too large. I will try again later today. Any ideas for "shrinking" the file size of photo's?

[F1nut]

I'm close to being near ready to almost decide to maybe spend 400 bux on the RDO tweeters, but have heard no objective sound reports.

Do a search, plenty of feedback here.

The silver coil SL2000's are still highly sensitive and accurate tweeters.

Accurate tweeters don't have a 5dB spike at 13kHz.


I realize that you are quite use to your set up after all these years, but the fact remains, the new tweeters are a major improvement. The crossover components are cheap, worn out and need to be upgraded. You can do much better in the power department. None of these comments are a knock against you, just an effort to help you improve your music enjoyment.

What schematic did you receive?

[F1nut]

Carl,

There should be a "resize" option on your computer, but I'm not the best person to ask about that stuff.

[djf]

If the "resize: option is not there, you can use some good imaging processing software. I recommend downloading the trial version of "Advanced Batch Converter", which can translate between 55 different image formats.
Do a google on it, it's the first hit.

I'm 51 years old, I've had these now for almost 20 years, and when you get to be 51, a 5db spike doesn't hurt.

And I've heard criticism of using equalizers, and I understand that, but you get what you pay for, and my BSR EQ-3000 is a very, very, very good equalizer. I'm running almost totally flat now, with about a 2db boost at 1K, and a bit of a boost at 31.5

I had major problems (beside the cold solder point) when I did the xover work, the whole blasted thing basically fell out of the cabinet and pulled all the wires. So I had to pull the xover from the right half and figure out all the wiring.

They are all back together now, and have been since last night. I understand more power might help. But truthfully, this Kenwood stuff is very, very good.

I suspect I will order 4 of the tweeters, which give me enough to either put two in each, or swap them all out on one of the channels for an A/B comparison.

Currently: Coming up Close, A retrospective Till Tuesday w/ Aimee Mann

The xover schematic that got sent is a single board about 7 in by 5 in, one single large coil on the underside, C1-C6, labelled Polk Audio SDA Series on the right side. I think it's for the SDA 2's

[F1nut]

Hey, I'm only two years behind you and that spike made my ears bleed. Anyway, different strokes and all that.

I can email you a copy of the SRS schematic if you want. Those 20 year old caps aren't doing you any favors.

[schwarcw]

I'm 52 and that 5 dB spike makes me ill. I have my new 2.3's in the garage and won't bring them into my family room until I get the new tweeters. My crossover parts from SonicCraft have arrived. The Polk tweeters are on backorder. Ken told me they would ship 11/17. I have my new tweeters and ugraded crossovers done and the 12.3's in the family room by Dec. 1 thereabouts. I'm going to mess with the resizing option. Let see how it goes. Otherwise I'll email the pics to whoever want them. I only have about three or four good ones.

[schwarcw]

Let's see if these pics fit onto the thread.

Carl

[schwarcw]

Couldn't resist! The last one of me and my daughter was taken at her wedding this summer. It was right next to the stereo board on my piclist.

Carl

[djf]

OK! Four brand new out of the box 4amp 250v slo-blo's in the Kenwood Audio Purist, and I'm bi-amping again.

Have NOT been able yet to trip the polyswitches!

Currently, Heat of the Night - Bryan Adams

Jaw dropping!!!

[fenderlady]

Ya I found out on Monday when I called about the backorder!

Great pic of the wedding. Ya don't look 52, and your daughter was beautiful!

[schwarcw]

Thanks for the kind words Fenderlady! Ken told me the tweeters for my SRS-2.3's will ship on 11/17. So yours won't be far behind.

Carl