My Polk SDA 2B journey....

[Navy_Goat]

25 years ago I encountered a huge set of speakers at my buddies fathers house. They were six feet tall and three feet wide. Multiple rows of mid-range drivers and tweeters, a huge woofer (turn out it was a passive radiator). The sound they produced was overpowering, I believe they were running on a stack of Mac gear. At the time all i knew was they were big, great looking and sounded amazing. For reference I was driving a set of Infinity SMs with a Harmon Kardon AVR. I though my speakers sounded okay, that day changed my mind. Work, raising a family and a million other things stopped me from looking for similar speakers at the time.

A few months ago I set out to improve my living room rig. I could still remember that crazy set of speakers I encountered so many years ago. A little research revealed that they were definitely something from the Polk SDA line from the Late 80's or early 90's. I remember two rows of four drivers and four tweeters on each speaker. That narrowed things down a bit. They must have been a set of the TOTL SDA's. A quick search revealed that I would have to be very patient to find a set of those that were near by and affordable. Patience is not my strong suit.

At some point i saw a blurry picture on FB marketplace that maybe just might have been an old Polk. The add contained no more details. I called and asked a few pictures of the SN plate on the back. At this point I was sure they were either Polk Monitor or SDAs. I ran out to her house and picked them up. 70 bucks and I was the proud owner of a set of Polk SDA 2B. Everything worked and the cabinets were in half decent needing some TLC to get them to maybe 7/10 condition.

I got them home and put them on either side of the my TV. While they certainly sounded better than the Bic America DV64 towers they replaced, they did not sound as good as I expected. After some research on the good old interwebs i determined that the AVR i was using (Sony STR-DN850) was not able to drive them properly. At this point I found the Polk Audio forum. The information and community there helped tremendously. They quickly convinced me to swap the tweeters and think about a variety of modifications that should really bring the speakers to life. I was trained as an avionics technician, but it been years since I had my hands in any gear. I'm certainly not afraid to dig in, so that's exactly what I did. I disassembled both of the speakers, ordered the upgraded new tweeter (TL mod) and two 5.8uf capacitors, spikes, and some jb weld to keep the magnets from shifting.
Left Side:

Right Side:


I took the crossovers to work to add the caps and a jumper required for the addition of the upgraded tweeters.


Added spikes and put them back in the living room.


By this time I had picked up a second hand power amp (Parasound HCA-1500a), so I hooked them up to the HCA running off of my old HK AVR 70. I am a bit of a pack rat when it comes to audio gear (and car parts) much to my wife's dismay. The HK has preouts and an optical in (AC-3) so it worked but was far less than ideal. I eventually upgraded to a Marantz NR-1509 using the preouts which will get me by until I can find the right deal on a good pre/pro and some more power amplifiers. I also added a Monster power HTS 3600 to keep everything safe and power things up in the right order. The monster Power also sorted out a bad ground loop from a very sloppy cable install.


I also added a Polk CSi40 to better match the L/R speakers. I do have a bunch of mods that will still get done at some point:
R/R all the components on both crossovers.
R/R all gaskets
Seal the enclosure seams and the connector plate
Add sound deadening material
Dynomat the baskets
Reinforce driver connections with TNuts

Thanks for reading! Questions and comments are welcome.

-Caleb

 

[kermit z]

Nice!! What a steal!!

 

[WaynerN]

The SDA-2B was my first Polk set, bought with a Canton subwoofer. I liked the polks but thought the Canton was almost worthless, so the whole set went back to the store in a short period of time. I returned with a pair of SDA-SRS 2.3 speakers! As the speakers in boxes were being carted out with a hand cart, one of the gals at the front desk did say "those are speakers?" Yes they were and I received a similar comment when I arrived home from the wife as she looked on. The looking on came to an end when she had to help me get them into the house (I think the weight was around 125 lbs each), so was the wife. Those were the good old days.

Enjoy your 2Bs. I think they were a very unique product, with good sound and mechanical engineering. My 2.3s are gone now in favor of the very old Martin Logan reQuests. Not many homes have room for 2 sets of speakers that are 5-6 feet tall, at least mine wasn't.

 

[Navy_Goat]

Scored a pair of SDA 1C's today. 3 hour drive each way to pick them up, but it was worth it!

 

[F1nut]

Dump the Monster, it dulls the sound. I hate to tell you this, but the 2BTL is a far better speaker than the 1C will ever be.

 

[Navy_Goat]

Dump the Monster, it dulls the sound.

It is eliminating a ground loop in the sloppy cable install that was done. I also like that it turns the components on in what I believe to be the right order. The ground loop was my main motivation for picking it up. I will have to look in to other solutions and alternatives.

I hate to tell you this, but the 2BTL is a far better speaker than the 1C will ever be.

No worries and I have read that. What do you think is the reason? As I said I have read a number of opinions from experienced long time Polkies, but I don't recall an explanation. Not disputing just looking for mode detail. I certainly don't expect a long post, maybe a link?

My 2B's have the TL mod but not fully upgraded crossovers. They are a long way from fully modded, but that will change over time. Unfortunately the wood veneer is not in even good condition and the side are slightly warped. Those two things don't effect sound, but I will remain on the look out for a set in better condition.

These 1C's are immaculate. The PO said he hardly used them and I believe him. Near perfect condition. Much better for the living room. So far they sound great, but I have not had the chance to really listen to them yet.

 

[hatrack71]

Well, mine are nowhere near as nice as your 2Bs. I need to buy a mid and tweeter and redo the end caps. But hey, they were free from a buddy who was going to scrap them. I had these same 2bs in the early 90's. Remember they were very nice sounding. He even still had the phasing cable.

 

[Navy_Goat]

Finally figured out how to get a few pictures of the the 1C's

 

[F1nut]

It is eliminating a ground loop in the sloppy cable install that was done. I also like that it turns the components on in what I believe to be the right order. The ground loop was my main motivation for picking it up. I will have to look in to other solutions and alternatives.


No worries and I have read that. What do you think is the reason? As I said I have read a number of opinions from experienced long time Polkies, but I don't recall an explanation. Not disputing just looking for mode detail. I certainly don't expect a long post, maybe a link?

My 2B's have the TL mod but not fully upgraded crossovers. They are a long way from fully modded, but that will change over time. Unfortunately the wood veneer is not in even good condition and the side are slightly warped. Those two things don't effect sound, but I will remain on the look out for a set in better condition.

These 1C's are immaculate. The PO said he hardly used them and I believe him. Near perfect condition. Much better for the living room. So far they sound great, but I have not had the chance to really listen to them yet.

Are you saying you think the ground loop issue is caused by the house wiring? That should not be the case. More likely it's because you had your gear plugged into different circuits. Now, because it's all on one circuit the ground loop issue is resolved. There are far better power conditioners than Monster available that do not screw up the sound and in fact can improve it.

The 1C's can only use the SL2000 or RD0194 tweeter whereas the 2BTL can, as you have already done, use the better RD0198. The 1C's have too much mid-bass resulting in a chesty, slow sound signature, which presents an unbalanced overall sound. The 2BTL is perfectly balanced, top to bottom.

You could have taken that $400 and improved the sound and appearance of the 2BTL's with it.

 

[Navy_Goat]

Are you saying you think the ground loop issue is caused by the house wiring? That should not be the case. More likely it's because you had your gear plugged into different circuits. Now, because it's all on one circuit the ground loop issue is resolved.

I believe the Cable Coax coming from the pole is not grounded and my reading tells me it should be. When I added the Marantz AVR to the equation I immediately picked up a bad 60-100hz hum, which I attributed to a ground loop. I found that Monster FS locally for $40 so I figured it was worth a try. The hum disappeared as soon as i added it to the system. The hum was not present with the HK AVR I was using prior, but I attributed that to the fact that I was previously using the optical connection between the TV and AVR and the Cable box was not directly connected to the AVR in any way. It all added up to me at the time, but I am new to this hobby so I could certainly be making a variety of rookie mistakes.

I only have one outlet on the wall the Stereo is on so I have been using the same outlet and circuit the whole time.

There are far better power conditioners than Monster available that do not screw up the sound and in fact can improve it.

Im sure this is the case. You know where I am on this journey. I am thinking internal components on the 2BTL's and installing the rest of the upgrades I have been collecting is the next place to spend some freee coin on. HOnestly I would be perfectly happy with a decent surge supressor for protection so long as the ground hum didn't come back.

The 1C's can only use the SL2000 or RD0194 tweeter whereas the 2BTL can, as you have already done, use the better RD0198. The 1C's have too much mid-bass resulting in a chesty, slow sound signature, which presents an unbalanced overall sound. The 2BTL is perfectly balanced, top to bottom.

Thanks for the explanation. So far I am enjoying the sound, but that could be purely placebo effect. I should be able to get my money back out of them if I decide they are not worth upgrading. For now it gives me the perfect opportunity take my 2B's out of the living room to finish the upgrades.

You could have taken that $400 and improved the sound and appearance of the 2BTL's with it.

Undoubtedly true, but due to condition and my curiosity I went this way. I can sell them and put the money in to the 2BTLs, but I felt I would not get this chance again any time soon. THese 1Cs are in exceptional condition.

I don't think I have the skills, experience or equipment to significantly improve the appearance of the 2BTL's

 

[F1nut]

Ah, the cable TV issue. Very common problem caused by the installer not running a proper ground. Have your cable company come back to fix the problem as it is their responsibility.

 

[drew_t]

Scored a pair of SDA 1C's today. 3 hour drive each way to pick them up, but it was worth it!

I just scored a pair, too -- from the next door neighbor! In very nice condition other than the grill cloth evidently having done double duty as a cat scratching post at some point.

F1nut, two questions:
1. if I'm not ready to do any mods yet, should the NP electrolytics in the crossovers nonetheless be replaced just because they're 30 years old, or will it be obvious from the sound if they are bad?
2. Are you aware of any part numbers for current production isolation transformers that would work in place of the three recommended in the SDA guide PDF that is available over on the Polk forum? I know the torroid option is the more serious one, but I wouldn't mind having a more economical one just for the sake of convenience to hook up to non-common ground amps while I'm still in "playing around with new toy" mode.

 

[F1nut]

1. The original caps are way past their lifespan.
2. Only 1C's above certain serial numbers can use the isolation transformer and I don't have that info handy. That said, I have no idea if any of the 3 mentioned are available today. I can tell you none come even close in performance to the ones from Avel.

 

[Navy_Goat]

Crossover upgrades on the 2B's should be complete in a few days. All caps on hand. I will do the soldering work at work because I have access to much better equipment there. I decided to go with Sonicraft in the HP circuit and Clarity PX in the low side. I will be subbing 2 x 20uf for a 40uf in the low side and space will be tight. I have 3D printed a spacer to sit in between the two 20uf caps and I may need to find a way to secure the whole assembly. I can post pictures after I get it all figured out.

H-Nuts and gaskets went in today. Soldering work will be done early this week whenever I have some free time. Work is getting busy so I can only hope to get to it early this week.

 

[Navy_Goat]

Ah, the cable TV issue. Very common problem caused by the installer not running a proper ground. Have your cable company come back to fix the problem as it is their responsibility.

I did have the cable company come back out. The cable was not grounded properly. The "tech" that was sent out could not understand what I was talking about and didn't have any idea how to fix the problem. I determined a course of action and walked him through it. The cable is now grounded so I can remove the Monster Power HTS 3600 and see if the hum comes back.

 

[F1nut]

Pretty sad that you had to educate the guy, but not surprising.

 

[bigcaddy64]

Crossover upgrades on the 2B's should be complete in a few days. All caps on hand. I will do the soldering work at work because I have access to much better equipment there. I decided to go with Sonicraft in the HP circuit and Clarity PX in the low side. I will be subbing 2 x 20uf for a 40uf in the low side and space will be tight. I have 3D printed a spacer to sit in between the two 20uf caps and I may need to find a way to secure the whole assembly. I can post pictures after I get it all figured out.

H-Nuts and gaskets went in today. Soldering work will be done early this week whenever I have some free time. Work is getting busy so I can only hope to get to it early this week.

Do you have a shopping list for the caps installed? I was just refreshing a pair of these (SDA 2) for my neighbor but only opted to upgrade the tweeters, glue the magnets and add more stuffing for now. I made a cap list but i think he was shocked at the price, $200+, but he's happy and they sound fantastic. I was shocked at the amount of bass put out with only a radiator in each cabinet.

 

[Navy_Goat]

Do you have a shopping list for the caps installed? I was just refreshing a pair of these (SDA 2) for my neighbor but only opted to upgrade the tweeters, glue the magnets and add more stuffing for now. I made a cap list but i think he was shocked at the price, $200+, but he's happy and they sound fantastic. I was shocked at the amount of bass put out with only a radiator in each cabinet.

I kept the receipts, let me see if I can put it all together in one place....

 

[F1nut]

Do not add more poly fill. There should be none below the mid-drivers.

The SDA 2 crossover is different than the 2B.

 

[Navy_Goat]

@F1nut and the rest of the crew over a the Polk Audio forum spoon fed most of this to me. Here is everything I can remember about the specific pieces I used to upgrade and modify my 2B's.

Crossover Refresh:
2 x 12 uF (Sonic Craft) - $61.92 http://www.soniccraft.com/product_info.php/gen-sonicap-12-uf-200vdc-p-452
6 x 20 uF (Madisound) - $93.00 https://www.madisoundspeakerstore.com/px-cap-250vdc/claritycap-20-mfd-px-range-polypropylene-caps/
2 x 2.7 ohms (Sonic Craft) - $8.26 http://www.soniccraft.com/product_info.php/27-ohm-vishay-mills-mra-12-p-4636
2 x 0.47 ohm (Sonic Craft) - $8.80 http://www.soniccraft.com/product_info.php/047-ohm-mills-mra-12-p-690

TL Mod:
2 x RD0198 (Midwest Speaker Repair) - $109.90 https://www.midwestspeakerrepair.co...polk-audio-sl2500-sl3000-1-inch-dome-tweeter/
2 x 5.8 uF 200vdc (Sonic Craft) - $40.94 http://www.soniccraft.com/product_info.php/gen-sonicap-58-uf-200vdc-p-440

Misc:
2 x Dayton DSS4 Spikes (4pcs) https://www.parts-express.com/dayton-audio-dss4-bk-black-speaker-spike-set-4-pcs--240-717
H-Nuts (50 pcs) https://www.parts-express.com/parts-express-8-32-hurricane-nuts-50-pcs--081-1080
8-32 Button Head (50 pcs) https://www.amazon.com/gp/product/B00918P3S6/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
Armacell pipe tape (Home Depot)
Silver Solder (Amazon) - https://www.amazon.com/gp/product/B01LE3MANQ/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1
Mounting Tape (Amazon) - https://www.amazon.com/gp/product/B003W0R4PE/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
Zip Ties (Amazon) - https://www.amazon.com/gp/product/B07NZ5F523/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

A full parts list and a whole lot more can also be found here: http://www.gimpod.com/

A few notes:

I went with the clarity PX rather than more Sonicap because the price was less than 1/2.

I also opted to do all this with the OEM boards rather than using the Gimpod units. I hove no doubt that the Gimpod boards are great and worth every penny and I may add them in the future. For some reason I just wanted to see if I would be happy going the simplest route as using the new boards requires a lot more soldering. I am not finished with the mods so I will report back how much of a pain it was to fit everything on the OEM board.

I added the following items to improve things along the way:

Interconnect Cable BB 20ft (ebay) - $49.99 https://www.ebay.com/itm/Interconne...tUAAOSwpLNYB435:sc:USPSFirstClass!92111!US!-1
Worlds best cables 2' IC (Amazon) - https://www.amazon.com/gp/product/B01ALN2Z12/ref=ppx_yo_dt_b_asin_title_o05_s03?ie=UTF8&psc=1
Blue Jean Cable - Optical IC, replaced all HDMI and 2 x 8ft speaker wire with spades at both ends. https://www.bluejeanscable.com/index.htm

That's about all I can think of. Cheers,

Caleb