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  1. #1

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    Default SRS inductor placement

    Well, I am about finished with my SRS upgrades. All has gone well and the SQ improvement is truly astounding. I will report in much more detail once the job is complete and I've had an opportunity to do some good critical listening. Well, yesterday the last item was to change the large 16mH inductor as reported on by DarqueKnight. When I first powered them up with the new NorthCreeks I could immediately hear a significant difference in the bass response which was more tactile and very clean. I also think I get at least another 1/2 octave out of the PR than before. BUT, my soundstage has shrunk dramatically . On one track in particular where there should be music at almost 90 degrees to my listening position it has moved almost all the way back to the speakers. Most musical content is now confined between the 2 speakers ? not very SDA like . I have used aluminum hardware to mount these on the brace that separates the dimensional from the stereo drivers (brace runs down the middle of the cabinet from the top almost down to the XO?r) midway between the front and back of the cabinet. My thought was to mount it as much as possible in ?no mans land?. This inductor is heavy and needs a significant mount, which doens't leave a lot of options. Either these need to burn in A LOT, or I need to move them somewhere. I?ve even thought about drilling a couple of holes and mounting it external. If I can?t find a fix I?ll go back to the stock inductors and I?ll have pretty cool looking pair of very heavy and expensive paper weights. Any ideas would be appreciated.

  2. #2

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    You need to let the new caps burn in for at least 200 hours. After that, see if the sound stage is still an issue.
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  3. #3

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    Something is wrong. Since you reported getting more bass, the inductors are in the circuit and passing current to the DA's but you've lost the stereo difference signal between them. I think you've lost it at the connection to the IC someplace inside the speaker. Note how pin-2 on the IC plug connects to one side of the 16 mH inductor via pin-1 of plug-1 on the XO board. Double check those connections on both speakers.

    Burn in will not fix this.
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    Seems like you may have some polarity reversals somewhere. It is easy to get the colors mixed up. Make sure the connections are correct at the speaker and amp binding posts and at each individual driver and tweeter.

    There is an SRS wiring diagram in post #5 of the SDA Schematics area of the Vintage Speakers sub-forum.

    Also, as OldmanSRS suggested, make sure something has not come loose inside the speaker at the SDA IC jacks. Faulty SDA IC connectivity will definitely shrink the sound stage.
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    Quote Originally Posted by OldmanSRS View Post
    Something is wrong. Since you reported getting more bass, the inductors are in the circuit and passing current to the DA's but you've lost the stereo difference signal between them. I think you've lost it at the connection to the IC someplace inside the speaker. Note how pin-2 on the IC plug connects to one side of the 16 mH inductor via pin-1 of plug-1 on the XO board. Double check those connections on both speakers.

    Burn in will not fix this.
    My troubleshooting suggestion was specific to the 1.2 or 1.2TL. SRS's have different wiring.
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    Dcoil,

    Do you have SRS's, SRS 1.2's or SRS 1.2TL's? I thought your question was about SRS's.

    No matter the version, it is a good idea to check the IC connections and driver and tweeter connections.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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    First, I really appreciate the suggestions to help fix my problem. This CP forum is really First Class! When I did my XO'r upgrade I simply attached some 'quick connects' to the original 16mH inductor and mounted the new NorthCreek inductors (unconnected) inside the cabinet as stated. I used the schematics from DarqueKnight's 'Compendium' to make sure I had everything connected properly. I let the XO'v burn in for several weeks so I could appreciate the sound from the Soncicaps and Mills upgrades w/ the original 16Mh inductor connected. After 'burn-in' the speakers really sounded fantastic! Then I simply removed the allen screws holding in the XO'r and pulled it out enough to disconnect the original 16mH inductors and connected the new NorthCreeks. These are the original SRS (not 1.2 or 1.2TL's). As stated, the punch and depth of the bass is significantly improved, but the sound stage also collapsed dramatically.

    So, with the above info (sorry, I should have included much of this in my original post...) what is the diagnosis??
    So, with the above info (sorry, I should have included much of this in my original post...) what is the diagnosis??

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    Just to make sure I understand:

    1. The sound stage is fine with the stock inductors.

    2. When the stock inductors are disconnected and the Northcreek inductors connected in their place, the sound stage collapses.

    3. The inductors are mounted vertically on the brace between the stereo and dimensional drivers, in close proximity to the steel baskets of a driver.

    I found that vertically mounting the Northcreek inductor on the cabinet wall behind the passive radiator resulted in the worst sound. See fig. 13 in this thread: Northcreek Mod for 1.2TL.

    Are you able to mount the inductor as shown in fig. 6 of this thread: Northcreek Mod for SRS? I drilled the mounting bolt hole from the underside of the brace by accessing it through the passive radiator hole.

    Do you have, or have access to, and LCR meter to measure whether the inductors are within spec?
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    I have to agree with F1Nut on this. Give the caps a chance to burn in. I lost some staging when I first did the crossover in my 2's and it snapped back into place after about 100hrs or so.

    If you fiddle to much with placement you aren't playing them to burn in the caps. Give it a chance to ease up on its own.
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    He said the sound stage shrank after he changed the 16 mH inductors and that he had already let the caps burn in for several weeks prior to changing the inductors.

    Quote Originally Posted by dcoil View Post
    . I let the XO'v burn in for several weeks so I could appreciate the sound from the Soncicaps and Mills upgrades w/ the original 16Mh inductor connected. After 'burn-in' the speakers really sounded fantastic! Then I simply removed the allen screws holding in the XO'r and pulled it out enough to disconnect the original 16mH inductors and connected the new NorthCreeks. These are the original SRS (not 1.2 or 1.2TL's). As stated, the punch and depth of the bass is significantly improved, but the sound stage also collapsed dramatically.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  11. #11

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    Quote Originally Posted by DarqueKnight View Post
    Just to make sure I understand:

    1. The sound stage is fine with the stock inductors.

    2. When the stock inductors are disconnected and the Northcreek inductors connected in their place, the sound stage collapses.

    3. The inductors are mounted vertically on the brace between the stereo and dimensional drivers, in close proximity to the steel baskets of a driver.

    I found that vertically mounting the Northcreek inductor on the cabinet wall behind the passive radiator resulted in the worst sound. See fig. 13 in this thread: Northcreek Mod for 1.2TL.

    Are you able to mount the inductor as shown in fig. 6 of this thread: Northcreek Mod for SRS? I drilled the mounting bolt hole from the underside of the brace by accessing it through the passive radiator hole.

    Do you have, or have access to, and LCR meter to measure whether the inductors are within spec?
    Ray, the answer to questions 1, and 2 is 'yes'. But 'no' to question 3 as it is mounted as far away as geometrically possible from other metal and still have something study enough to mount them on. And I read your excellent review about how sensitive these inductors were to placement and the resulting sound quality. I tried to pick a spot not close to the PR, the XO'r, either the dimensional or stereo driver, or the binding posts. It is however in a vertical orientation which you mentioned in your review may contributing to 'sonic deterioration'. I guess I just didn't believe that vertical vs horizontal could affect sound quality to this extent. I should have listened to those that are a bit more knowledgeable in this area than I am. I also read your review of your SRS inductor mod and the position behind the XO'r. I thought this location was fairly close to the large PR basket, and it is immediately behind (and down) from the XO'r. But this is where I will re-locate them . As I have stated, the extra punch from the Northcreek is Very nice. Stay tuned as I will report back after the re-positioning!

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    Quote Originally Posted by DarqueKnight View Post
    Just to make sure I understand:

    1. The sound stage is fine with the stock inductors.

    2. When the stock inductors are disconnected and the Northcreek inductors connected in their place, the sound stage collapses.

    3. The inductors are mounted vertically on the brace between the stereo and dimensional drivers, in close proximity to the steel baskets of a driver.

    I found that vertically mounting the Northcreek inductor on the cabinet wall behind the passive radiator resulted in the worst sound. See fig. 13 in this thread: Northcreek Mod for 1.2TL.

    Are you able to mount the inductor as shown in fig. 6 of this thread: Northcreek Mod for SRS? I drilled the mounting bolt hole from the underside of the brace by accessing it through the passive radiator hole.

    Do you have, or have access to, and LCR meter to measure whether the inductors are within spec?
    Ray, the answer to questions 1, and 2 is 'yes'. But 'no' to question 3 as it is mounted as far away as geometrically possible from other metal and still have something study enough to mount them on. And I read your excellent review about how sensitive these inductors were to placement and the resulting sound quality. I tried to pick a spot not close to the PR, the XO'r, either the dimensional or stereo driver, or the binding posts. It is however in a vertical orientation which you mentioned in your review may contributing to 'sonic deterioration'. I guess I just didn't believe that vertical vs horizontal could affect sound quality to this extent . I should have listened to those that are a bit more knowledgeable in this area than I am. I also read your review of your SRS inductor mod and the position behind the XO'r. I thought this location was fairly close to the large PR basket, and it is immediately behind (and down) from the XO'r. But this is where I will re-locate them . As I have stated, the extra punch from the Northcreek is Very nice. Stay tuned as I will report back after the re-positioning!

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    Quote Originally Posted by dcoil View Post
    It is however in a vertical orientation which you mentioned in your review may contributing to 'sonic deterioration'. I guess I just didn't believe that vertical vs horizontal could affect sound quality to this extent !
    The steel baskets and magnets of the drivers are probably having a greater effect than vertical or horizontal orientation.

    I don't fully understand what is going on with these inductors with regard to placement issues. The manufacturer said they aren't sensitive to placement but my ears heard different things at different positions in the cabinet.

    With regard to vertical placement, the Northcreek inductors are oriented vertically in two of my of CRS+ pairs and the sound is excellent. However, the inductors are not directly behind or very close to either the passive radiator or the drivers. They are in an upper rear corner of the cabinet above and behind the drivers and above and to the side of the passive radiator.

    CRS+ PCB and SDA Inductor Mod
    Last edited by DarqueKnight; 03-08-2011 at 08:40 PM.
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    It is probably an issue due to the Magnets on the drivers. I have seen this more with iron core but I would guess that is the issue. You have them vertical between the drivers yes? It could be a polarity thing. The Magnets are sending out dissimilar signals and the coil is getting caught in the crossfire.

    I would place them as far as I could from the drivers.
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    Well, first let me sincerely apologize to everyone . After all of the discussion on my shrunken soundstage after the inductor 'upgrade' I was prepared for a long night. Drill in hand, allen wrenches, other tools, etc. I took off the PR on the left speaker and low and behold I had a wire dangling with a stock connector that went to the PCB . Of course, this wire is from the dimensional speakers. So, I re-connected it, the PR, and voila - I HAVE THE SWEETEST SOUNDING SPEAKER I'VE EVER HEARD! .

    OldmanSRS had diagnosed it early - bad wiring. Boy, do I feel stupid! I had purposely positioned the new inductor based on the reviews by DarqueKnight on how sensitive the sound quality was in regards to orientation/placement! I even routed the wiring from both the dimensional and stereo drivers to the outside of the cabinet away from the inductor. Magnetism from the drivers decays at a rate of 1/r squared, which means that the driver magnets should not have much, if any, affect on the inductor in this position. The PR and XO'r were also at maximum distance to the inductor placement (while still keeping the inductor inside the cabinet). But I made a basic mistake, and assumed the worse. And even though my bottom end was fabulous, with the collapse of the sound stage I thought the inductor upgrade was not worth it. Oh ye of little faith....

    Well, bottom line is that the placement (I'll post pics later) that I chose, based on DK's review, was pretty good! I'm not a big time audio guy, and I am learning A LOT from this forum - which has some FANTASTIC members. As a result, I now have a pair of speakers which simply do not compare to anything that I have ever heard! Granted, I have not strolled into the really high $ audio store. And I know that everyone has their own particulars 'preferences' in what they consider 'good audio'. But I have listened to $10K - $15K speakers. And seriously, if someone wanted to trade me a pair of anything that I've heard to date - "NO DEAL"!

    I spent the evening listening to Dave Koz - 'Saxophohic' which I think was mastered for SDA speakers ! Also my 'reference' CD's include 'The Dance' also by Dave Koz, and a couple of Peter White selections (including Confidential). These are not recent releases, but they are something that 'I KNOW'. And I can use as a 'reference' anytime I change anything in my system. And honesly, I've never heard them sound so good. I actually went to see if my sub was turned off! Yes, the inductor upgrade is that potent!

    In summation, and as so eloquently stated by 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

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    Glad you found that loose connector. I'm interested in your opinion on how the bass is affected specifically; is there any hint of muddiness, or too much bass - boomminess, etc.

    This mod removes 4 Ohms of DCR from the DA circuit which essentially doubles it's bass output even surpassing the bass output of the SA by 42%. My brain tells me this is not keeping true to the sound of the speaker as designed but I'm keeping an open mind and want to hear your opinion.

    I've heard others liked it. What's your take, details please.
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    To answer your question OldmanSRS, from DK's review (link above in his post #12) the direct current resistance (DCR) of the modified SRS's decreased from 4.7 ohms each to 4.4 ohms each with the new 16 mH SDA inductor. I have not had a chance to use my reference cd with tone generator with my SPL meter to see if there is any 'bloat'. I would say there may be a slight amount, but if there is it's not mid-bass, it's bass. In the analysis that DK did, he thought the amount of bass actually slightly decreased, but thought it was much cleaner and had more 'punch'. This may be what I am hearing also. No doubt I have picked up at least a 1/2 octave, and maybe much more. I had them hooked up to my HT rig last night, and even though I was in 'pure stereo' mode, I actually got up and made sure my sub was not on! I had adjusted the crossover on the sub to blend in with my SRS before I started any of the mods. It worked smoothly to cut-in the sub just under 50Hz, and was helping quite a bit by 30Hz. But now I really don't think I will miss the sub for my 2 channel listening. I am really impressed with this mod.

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