Polk SDA-SRS 1.2/2.3TL Modifications

decatodecato Posts: 150
edited August 2010 in Vintage Speakers
Hi everyone,
I wanted to share with you some of my SDA experiences over the years. It’s a long read but hopefully informative.

I began my SDA hobby in 1997 with a used pair of 2Bs that I bought from a local shop. They replaced my Monitor 10 Series 2, which had been my primary speakers since 1993. I used the 2Bs for a few months and then stumbled across a pair of SRS 2.3s at a different local shop. The salesperson attempted to demo them for me with two Denon monoblock power amps while the interconnect cable was in place. What a display of fireworks! The grills were off the speakers when he started playing a CD, and I clearly remember seeing about a 1" excursion on all 12 drivers while they produced extremely loud popping noises. The end result was 2 blown tweeters (the main one in each channel) and one dimensional driver. It had burned so badly that the lacquer around the voice coil melted and caused the cone to become frozen in place. I purchased the pair for $300 in their less than ideal condition. Nevertheless, I ordered replacement parts and got them working in no time. However, I felt they lacked midrange clarity.

In 1998 I actually converted the 2.3 to a 2.3TL. My father played an instrumental role in helping me with this project and the others I will describe shortly, as he is skilled in working with electronics. I swapped the left and right cabinets and ordered 12 MW6510s and 6 SL3000s from Polk, new internal wiring from Home Depot, and new crossover parts from Madisound. I used Carli polyester film capacitors, standard inductors, and sandcast wire-wound resistors. After all that work, I noticed that I heard much more detail than the regular 2.3, especially in the midrange. However, it was not really pleasing, as vocals, soprano sax, and electric guitar often became harsh. It wasn't scratchy - not something that could be fixed by replacing the tweeters with the now popular RD0198-1. The problem resided somewhere within the frequencies chosen for the crossover points. Though dissatisfied, I left it like that for a while.

In 1999, I bought a pair of SRS 1.2TLs off a posting I saw on deja-news (now Google groups). They sounded great, but it bothered me that the 2.3TLs sounded so different. My next attempt was to actually use the 1.2TL crossover in the 2.3TL. So, in 2002, I again ordered all new crossover parts. The only part of the circuitry that I eliminated was that which corresponds to tweeter 4 in the 1.2TL (for obvious reasons). Not bad – getting much closer! Still the midrange seemed a bit forward, a property inherent to MW6510 drivers. So, I ordered 8 MW6503s for the stereo arrays and replaced the MW6510s. It was even closer, though I still heard “hootiness” within the cabinet on some vocal tracks, slightly above 200Hz. I also left the MW6510s in the dimensional array, as they afforded a really wide sound stage. Though not perfect, I decided to leave it alone for a while.

In 2003, I read the “Picking Capacitors” article by Walter Jung and decided to switch all capacitors in the tweeter sections of both the 2.3TL and 1.2TL with Solens. This was a significant improvement. Cymbals were clearer and had less “fuzz” around them, as did female vocals and solo reed instruments. In this round of experimentation, I also decided to modify the cabinet of the 2.3TL in an attempt to reduce the aforementioned hootiness. I added internal bracing from side to side behind the middle of the driver panel, and a 3-sided brace right below the crossover. I also added one more brace from front to back above the highest tweeter. Finally, I ordered 2 quarts of Soundcoat from Percy Audio and painted the insides of the cabinets. Wow, what an improvement! No more boxy sound! (Well, maybe just an iota on one or two particular frequencies, but it was more than acceptable.) The center image also became much more prominent.

It is during this experiment that I also learned how important it is to have the internal damping material opened and spread evenly. While replacing the tweeter caps in the 1.2TL, I noticed that the damping “fluff” was rolled up into a narrow bun. I could see the back and sides of the cabinet showing. So, I opened it up, trying to cover as much of the perimeter as possible. That change alone added some midrange clarity. However, the midrange was now better on the 2.3TL. The only difference was the use of Carli caps in the 2.3TL and stock NP-electrolytic caps in the 1.2TL. I did not think it mattered what kind of cap was used in a low-pass circuit, but I rounded up some Carli caps I had in the basement and replaced the stock caps. Wow! They do make a difference, most noticeable on any recording with acoustic guitar. It no longer seemed like the guitar was being played from behind a curtain. Individual notes could be heard more clearly and with “space” in between them.

Now comes the latest (and probably my last) experiment. Though I hardly ever post, I read this forum all the time (sorry – hopefully this makes up for it :) ). I see how everyone speaks so highly of Mills resistors, Solen caps in the low-pass section, better tolerance silver-mica caps, and the new RD0198-1 tweeters. So, I ordered all of these components for my speakers and installed them in the 1.2TL this weekend. Next week I will do the same for my hacked 2.3TL.

(Though off topic, I can confirm the inconsistency of the silver-mica caps used. My left channel used unmarked caps and my right channel used caps with a value of 560pf.)

I replaced the silver-mica caps with 750pf caps from Parts Connexion. I used 12w Mills resistors in place of the sandcast stock parts. Solen capacitors went in the low-pass section. Moreover, I also took a risk by replacing all inductors for the woofer section of the crossover, including the large 16mH. I ordered Sidewinder 1.0mH and 2.0mH chokes for the midrange and a large, custom-wound steel laminate 16.0mH choke for the bass, all with lower DCR than the stock parts. Yes, I know changing the DC resistance can change the overall Q of the speaker as well as shift the crossover points slightly. I am also intrigued how a speaker can be rated at 1000 watts while using 100 watt 20awg wire. Nonetheless, I put all the stuff together, as pictured below.

Too much bass! Something was not right. The low bass as well as the entire midrange spectrum was too forceful and masked the tweeters’ output. I liked the low bass improvements but could not tolerate how much sound was coming from the driver arrays. So I reinstalled the original inductors, but it was still unacceptable to me – too much lower midrange. I played Sarah McLachlan’s Angel and heard tubbiness in her voice when she sang lower notes. Much to my surprise, the Solen caps were responsible for this sound. I put back the Sidewinder inductors as well as the Carli caps I previously removed. This was the magical combination — excellent low bass response that blended smoothly into the midrange. In addition, the tighter tolerance resistors and new tweeters really smoothed out the treble. It sounds like a whole new speaker. I couldn’t be more pleased with it.

(I must admit that I was looking into the VMPS RM40. However, I read an article that shows the passive radiator has a foam surround and that they tweak its performance by putting a layer of Elmer’s glue on it. Look here: http://www.audiocircle.com/circles/modules.php?set_albumName=albup17&op=modload&name=gallery&file=index&include=view_album.php
Maybe it’s a great speaker, but I don’t want to spend $6000 for a pair. Besides, I can have lots of fun playing with what I already have!

Well, so much for my thesis on 8 years of experimentation. I hope it can help someone in some way.

-Brian Borowski
Post edited by decato on

Comments

  • F1nutF1nut Posts: 45,401
    edited December 2005
    Hey Brian, good to hear from you.

    I have a question concerning your conversion of the 2.3 to 2.3TL.
    In 1998 I actually converted the 2.3 to a 2.3TL. My father played an instrumental role in helping me with this project and the others I will describe shortly, as he is skilled in working with electronics. I swapped the left and right cabinets and ordered 12 MW6510s and 6 SL3000s from Polk, new internal wiring from Home Depot, and new crossover parts from Madisound. I used Carli polyester film capacitors, standard inductors, and sandcast wire-wound resistors.

    As the crossovers are very different, did you build a complete 2.3TL spec crossover including the proper inductors, the addition of silver mica's and the complete change in caps and resistors?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • aaharvelaaharvel Registered User Posts: 4,505
    edited December 2005
    i need to be educated in SDA or SRT or whatever. When i see TL i think of Acura.
    H/K Signature 2.1+235
    Jungson MagicBoat II
    Revel Performa M-20
    Velodyne cht-10 sub
    Rega P1 Turntable

    "People working at Polk Audio must sit around the office and just laugh their balls off reading many of these comments." -Lush
  • decatodecato Posts: 150
    edited December 2005
    F1nut wrote:
    As the crossovers are very different, did you build a complete 2.3TL spec crossover including the proper inductors, the addition of silver mica's and the complete change in caps and resistors?

    Hey Jesse,
    Yes, every part from the 2.3 was removed and replaced with the correct value for the 2.3TL. I think the only thing I salvaged was the 0.4mH inductor for the tweeter, but don't quote me on that, it's been a while.

    I'll try to take a picture of this jumbo bag of spare parts I have accumulated. It's simultaneously funny and sad.

    -Brian
  • F1nutF1nut Posts: 45,401
    edited December 2005
    I think the only thing I salvaged was the 0.4mH inductor for the tweeter

    That would be correct, your memory is still excellent. :)

    Great read, thanks for posting it. I still haven't tried the Soundcoat, maybe one day.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • schwarcwschwarcw Posts: 7,269
    edited December 2005
    Brian, nice write up. Good to hear your project history. I have performed crossover mds to my 2.3's, I'd be interested in seeing the 2.3TL schematic if you have one. Attached is a phot of my before and after crossover mod of the 2.3's with Sinicap capacitors and Mills resistors. I did add some additional 0.1 uF by-pass caps to all the tweeter caps, while lowering the other caps by 0.1 uF to keep the same overall value as specified in the schematic. The results were remarkable. I'm planning a post of this project in the near future. The modifications actually make the SL2000 much less harsh, still to brittle for my taste. I just installed the RD-0194s yesterday. Polk had been out of these for about a month. My 2.3's sound terrific. Attached is a photo of my 2.3 crossover (before and after). I thought my crossover looked like a futuristic geometic art study until I saw yours. I was also looking into the Soundcoat. I saw it in Percy's catalog. I'd like to hear more about it.

    Nice work!
    Carl

  • Mike ReeterMike Reeter Posts: 4,031
    edited December 2005
    Brian,Excellent summary of your experiences...I'd say you would qualify for the title of "Master Tweeker"
    SDA SRS 2.3TL's/SDA SRS 3.1TL's/SDA CRS+4.1TL's and some other stuff
  • heiney9heiney9 Posts: 24,148
    edited December 2005
    Brian, thanks for the write-up, very informative. :) .

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • scottyjacksscottyjacks Posts: 19
    edited December 2005
    Hello,
    THis is a little beyond me technically - I have an original set of 2.3tl's that are starting to give me some problems - so I am thinking refurb. The drivers/tweeters all seem to be working.
    Could you summarize for me the latest greatest mix of drivers/tweeters that you are using? Soundsl like you have moved away from original tweeters at the least. Also - the crossover is the part I am most suspect of - is there a "stock" type replacement that you would recommend, or is it time to break out the soldering iron?
    I cannot believe I'm saying this, but If I can't get this issue resolved - I may have to retire them.......
    Scooter
  • decatodecato Posts: 150
    edited December 2005
    I have an original set of 2.3tl's that are starting to give me some problems - so I am thinking refurb.
    What specifically is wrong with them?
    Could you summarize for me the latest greatest mix of drivers/tweeters that you are using?
    4 x MW6503 stereo array (only if you plan on converting it to a mini 1.2TL - otherwise keep what you have)
    2 x MW6510 dimensional array
    3 x RD0198-1 tweeters
    Is there a "stock" type replacement that you would recommend, or is it time to break out the soldering iron?
    No, Polk no longer has a replacement. If you are sure the crossover is at fault, your best bet is to take it out and replace the components on it. Besides, if you use the components that I or other forum members recommended, you can greatly improve the sound quality.

    -Brian
  • scottyjacksscottyjacks Posts: 19
    edited December 2005
    The high end seems to cut out after about an hour of what I would consider reasonably high volume. I'm driving this with an Adcom 200wpc amp, Yamaha pre-amp. When I lower the volume, the system seems to come back on-line.

    So your suggestion would be to rebuild the crossovers?
    Scooter
  • scottyjacksscottyjacks Posts: 19
    edited December 2005
    Please explain - "convert to mini 1.2tl"?
    Scooter
  • WilliamM2WilliamM2 Posts: 4,703
    edited December 2005
    Scotty,

    Your polyswitches (tweeter protection) have gone bad. Polk will send you new ones, takes about 5 minutes to swap them out.
  • decatodecato Posts: 150
    edited December 2005
    Please explain - "convert to mini 1.2tl"?
    In my long post above, I mentioned that I basically changed my 2.3TL into a 1.2TL. I now use the crossover of the 1.2TL in the 2.3TL and have changed the drivers in the stereo array to match the crossover. This is a lot of work and rather costly; therefore, I cannot recommend it for everyone.
  • heiney9heiney9 Posts: 24,148
    edited December 2005
    WilliamM2 wrote:
    Scotty,

    Your polyswitches (tweeter protection) have gone bad. Polk will send you new ones, takes about 5 minutes to swap them out.

    This is most likely true. However, I've found some TL models don't have poly switches (atleast none indicated in the schematic) call Ken @ Polk Cust Serv to find out for sure

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • F1nutF1nut Posts: 45,401
    edited December 2005
    All 2.3TL's come with polyswitches from the factory. It sounds like yours are worn out.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • george danielgeorge daniel Posts: 12,108
    edited December 2005
    I concur with Dr. Jesse's diagnosis.surgical intervention is indicated,as replacement polyswitch's are in order :) This is a relatively minor procedure ,the only side effects noticed would be that after installation, your neighbors may be prone to sonic "ATTACK" :eek: :D Live long and prosper,,errr,,,rock on :cool:
    JC approves....he told me so. (F-1 nut)
  • decatodecato Posts: 150
    edited January 2006
    Hi everyone,
    I finished up my final set of changes to the speakers. I will rescind one statement I made earlier about Carli caps. The Solens are definitely better, and I have reinstalled them in both my 1.2TL and 2.3TL. I agree with others that they may be slightly forward in the midrange, but you cannot listen to the speaker up close to make your final decision. Moreover, it's difficult to do an A/B comparison between the left and right channels with the SDA interconnect removed. It does not provide an accurate model of what the sound will be like when everything is intact.

    So, my final decision is to keep the 1.2TLs pretty much original except for modifying the crossover, replacing the tweeters, and adding one sheet of polyester damping material behind each array.

    As you know, my 2.3TL is now very unique. The changes made are as follows:
    1. Used a 1.2TL crossover design minus one tweeter (T4).
    2. Used Solen caps, Madisound inductors, and Mills resistors in the crossover, though I did not replace the 16mH inductor like I did in the 1.2TL. If the DCR becomes too low here, I feel the 2 dimensional drivers will reach their excursion limits before the stereo drivers do, thus limiting the maximum output I could ever obtain.
    4. Replaced the tweeters.
    5. Used all MW6503 drivers. The MW6510s are very pushy in the midrange. Their BL and Q are quite different from that of the MW6503. Using them in the dimensional array creates a sound stage that's larger than life, like a twenty foot wide grand piano. I really like using all MW6503s, and the good news is they are still available from Polk.
    6. Reconstructed the wiring harness.
    7. Applied Soundcoat to the inside of the entire cabinet.
    8. Added extra bracing (one shelf, one side-to-side, one front-to-back, and one for "moral" useless support behind the passive radiator :( )
    9. Added one sheet of polyester damping material behind each array.
    10. Modified the moving mass on the passive radiators. I, unfortunately, received a pair with one SW150 and one SW155 :( .
    11. Applied gloss polyurethane to the caps and replaced the grill cloth.

    Here are some pictures. I hope you at least enjoy reading this!
  • F1nutF1nut Posts: 45,401
    edited January 2006
    Impressive!
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • Toka78Toka78 Posts: 192
    edited August 2006
    Sorry to dig up an old thread, but this seemed like the best place to ask...

    decato, have you tried using all MW6503 in the 1.2TL's? Or does the MW6511 not stand out as much when compared to the '10s?
  • DarqueKnightDarqueKnight Posts: 6,673
    edited August 2006
    Thanks for digging it up. I missed this when it was first posted. Very interesting read.
    "So hot it burns Mice!"~DK
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
    "Knowledge, without understanding, is a path to failure."~DK
    "Those who irrationally rail against something or someone that is no threat to them, actually desire (or desire to be like) the thing or person they are railing against."~DK
  • decatodecato Posts: 150
    edited August 2006
    Toka78 wrote:
    Sorry to dig up an old thread, but this seemed like the best place to ask...

    decato, have you tried using all MW6503 in the 1.2TL's? Or does the MW6511 not stand out as much when compared to the '10s?

    This would not be a good idea. The MW6511s are about 3.3 ohms DCR. The MW6503s are around 6.5 ohms DCR. So, this would change the crossover point a lot and most likely degrade the overall frequency response. I do not recommend this idea.

    Since my initial post, I have played around with the dimensional drivers on the 2.3TL. I tried the three possible combinations of drivers - both MW6503, both MW6510, and one of each (with the MW6510 on top for better blending with the loudest tweeter). I guess it really depends on the source material. Right now I settled back on 2 MW6510s for the 'wow' factor. It's a small and simple project worth investigating. Note that the MW6510 and MW6503 are each about 6.5 ohms DCR, so no major shift in the crossover point occurs.
  • Toka78Toka78 Posts: 192
    edited August 2006
    decato,

    Thanks for the detailed info...the reason I brought it up in the first place was I noticed (via the Compendium) that the original SRS had all MW6503, and not MW6511 in the dimensional array as they did later. Guess the new crossover played a part. That satisfied my knowledge itch, so thank you sir! :D


    Edited to add: decato, I can't believe I didn't notice it the first time, but you mentioned the VMPS RM40 speakers in your original post...oddly enough, those are the same exact speakers I was considering (vs. picking up 1.2TL's and working them over big time). Just curious, but have you ever heard them around the same time as your 1.2's? If so, how did they compare in regards to resolution and soundstage? I must admit I'm equally interested/turned off on the VMPS, as while I'm a fan of ribbons to a certain degree the idea of peeling putty from a PR to tune the bass seems maddening to me. I'm not much of a tweaker, rather 'set it and forget it'.
  • decatodecato Posts: 150
    edited August 2006
    Toka78 wrote:
    Just curious, but have you ever heard them around the same time as your 1.2's? If so, how did they compare in regards to resolution and soundstage?

    No, I never auditioned them. I had the 1.2TLs since 1999, a few years before the RM40 was introduced.
    Toka78 wrote:
    I must admit I'm equally interested/turned off on the VMPS, as while I'm a fan of ribbons to a certain degree the idea of peeling putty from a PR to tune the bass seems maddening to me. I'm not much of a tweaker, rather 'set it and forget it'.

    I'm not thrilled with the idea of using Elmer's glue on a $6000 speaker. I'm even more displeased with a foam surround on a stamped basket. That passive radiator looks like it costs $3 to produce. I can think of better ways to spend 6 grand.
  • Toka78Toka78 Posts: 192
    edited August 2006
    decato wrote:
    I'm not thrilled with the idea of using Elmer's glue on a $6000 speaker. I'm even more displeased with a foam surround on a stamped basket. That passive radiator looks like it costs $3 to produce. I can think of better ways to spend 6 grand.


    I have to say I agree. I've always considered myself more of a 'musiophile' as opposed to an 'audiophile'...too much voodoo and BS involved with the latter. In regards to VMPS, the more I look into it the more I'm pushed away...I'm thinking fully maxed-out 1.2TL's and a pile of records is a better buy. :cool:
  • decatodecato Posts: 150
    edited August 2006
    Toka78 wrote:
    I'm thinking fully maxed-out 1.2TL's and a pile of records is a better buy. :cool:

    You will not be disappointed with the 1.2TL!
  • hearingimparedhearingimpared Banned Posts: 21,473
    edited August 2006
    decato & darqueknight, I was a rabid audiophile in the late 70's & through the 80's. Was educated in one of the best electronic tech schools in the mid 70s on electronics and I did a lot of fearless modifying, building and upgrading speakers, amps, etc. I had a pair of SDA/SRS and a very high end system until hard times hit and had to sell the SRSs and almost every other component in early 1990. It has been that long since I even thought about a soldering iron or schematics. I just recently purchased a pair of SRS 1.2tl and am rebuilding my system. I have been reading both of your modifications papers on the SRS 1.2tls and upgrade pages and really would like to do the work on my new Polks. The problem is as I said before that I haven't kept up with any electronic work in over 16 years. I noticed on darqueknight's upgrade he states at the end that the work is not for the faint of heart or inexperienced. Can either one of you guys recommend a refresher course or something to get me up to snuff so I can do these upgrades? Thanks, Joe
  • mole'mole' Posts: 3,160
    edited August 2010
    i know old, but some good info in here.

    just doing my much needed reading for my new speakers
    mole'
  • Who originally started modifications to the big ol boys?
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!