SDA2 and missing midrange
sparks12kv
Posts: 5
I was fortunate enough to find a pair of original SDA2 speakers with the factory interconnect cable. I've heard lots of good things about the SDA line, and wanted to get some advice from the pros here.
All drivers are functioning, and using the interconnect cable does change the sound, but I am convinced that a significant part of the midrange is missing, to the point that they are difficult to listen to. There is no distortion, and I have tried disconnecting the outside tweeters to help focus the sound a bit, which did help. After a few hours of listening, I can become 'used to' the missing part of the audio, but a change back to any other speaker is revelatory. All related equipment is the same in these blind tests, and both polk speakers exhibit the same problem. I have also tried numerous different room placements, room is plenty big and i'm listening on the narrow side of a 24x18 room. I have the speakers set up exactly like the diagram on the back describes, and while the stereo effect changes by moving my chair closer or farther away, the midrange does not.
I would appreciate any help or thoughts.
All drivers are functioning, and using the interconnect cable does change the sound, but I am convinced that a significant part of the midrange is missing, to the point that they are difficult to listen to. There is no distortion, and I have tried disconnecting the outside tweeters to help focus the sound a bit, which did help. After a few hours of listening, I can become 'used to' the missing part of the audio, but a change back to any other speaker is revelatory. All related equipment is the same in these blind tests, and both polk speakers exhibit the same problem. I have also tried numerous different room placements, room is plenty big and i'm listening on the narrow side of a 24x18 room. I have the speakers set up exactly like the diagram on the back describes, and while the stereo effect changes by moving my chair closer or farther away, the midrange does not.
I would appreciate any help or thoughts.
SDA SRS 2.3TL (for sale)
Post edited by sparks12kv on
Comments
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Welcom to Cp
Are you using a common ground amp? Please list the gear you are using
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
Onkyo m506rs and onkyo p304 preamp. It sounded the same with an accuphase p300 as well. Both are common ground.SDA SRS 2.3TL (for sale)
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We can eliminate that possibility then.
Could be as simple as worn caps in the x-over. They are getting to be 30 years old. Electrolytics of that era are probably on their way to being dried up. If you are sure all the connections are proper that would be my guess. Most here have swapped out the old very cheap caps for new film caps and used much better Mills non-inductive wire wound resistors i the signal path with excellent, superb results.
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
I feel my stock SDA-2B lack in the midrange dept a little bit as well.
Not sure if you have a problem or not, but that is just my general observation of my stock speakers tried with a variety of different gear in different rooms. -
One thing older Polks really accel at is nice midrange bloom. Never heard a properly capped, properly fed pair of vintage Polks with the MW 65xx doped paper drivers sound lean in the midrange. It's either a gear related problem or the x-over is weaker. Also the sl2000 and sl1000 tweeters since they are brighter than the replacement RD0's tend to "mask" the midrange because the tweeters are so prominent.
It's been a very long time since I've heard a worn out bone stock pair of classic Polks. I usually can't stand them so I replace the horrid sl2000/sl1000 tweets with the new silk dome RD0's and re-cap the x-overs, delete the aging poly switch or completely bypass the fuses.
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
sparks12kv wrote: »Onkyo m506rs and onkyo p304 preamp. It sounded the same with an accuphase p300 as well. Both are common ground.
Are you sure? It appears your Onk is dual mono which generally isn't common ground. How do you know?.JPG)
"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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
According to the schem. the Onk will be fine provided the negative terminals are strapped together.
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I appreciate all the input. Good point about the Onkyo, (and a dead sexy shot of that fine beast as well) but since the speakers have the same sonic deficiency with the Accuphase, I must rule out amplification. I also swapped in another preamp, and while again the change is audible, no improvement in midrange output. I'm going to have to go with crossover problems as the next logical step.
I assume there is a handy spot with crossover schematics somewhere on this site. Anyone have any favorite components or favor a certain brand of caps for the recapping of these polks? And while I'm in there, is it alright to just leave the outer tweeter unconnected or is it better to 'adjust' the crossover to suit?SDA SRS 2.3TL (for sale) -
And you are sure the Accuphase is common ground? I can post the schematic and maybe FTGV can help confirm one way or the other.
http://www.accuphase.com/cat/p-300len.pdf
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
And you are sure the Accuphase is common ground? I can post the schematic and maybe FTGV can help confirm one way or the other.
http://www.accuphase.com/cat/p-300len.pdf
H9
Can't tell from that document. It's not a full schematic/service manual. The OP can check it easily enough if he's got a meter... -
sparks12kv wrote: »I assume there is a handy spot with crossover schematics somewhere on this site. Anyone have any favorite components or favor a certain brand of caps for the recapping of these polks? And while I'm in there, is it alright to just leave the outer tweeter unconnected or is it better to 'adjust' the crossover to suit?
Here: http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array(SDA)
It's best to also pull your x-overs to make sure of what parts/values you need. Polk made changes on the fly that didn't always show on the listed schematic. It won't be a dramatic change, but sometimes values changed or they subbed what they had on hand.
Many here use Sonicaps here:http://www.soniccraft.com/sonicap.htm
or
Clarity Cap here: http://www.madisound.com/manufacturers/claritycap/index.php
and replace all resistors with Mills wirewound non-inductive, found on the Sonicraft site as well. If budget is a concern use the Sonicaps or Clarity Caps on the high pass (tweeter circuit) and something like Solen or Dayton or Axon caps for the low pass. The Sonicaps or Clarity caps on the high pass are smoother more open than the Solen, Dayton or Axon. In the low pass it obviously doesn't make much of a difference.
There are threads on here addressing your tweeter concerns, some have left them unhooked and I think others have attempted to "modify" the parts in the cross-over to compensate. You'll have to poke around or maybe someone who has tried it will chime in.
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
http://www.accuphase.com/cat/p-300len.pdf Its strappable as long as it's in stereo mode.
Very nicely written and informative piece of lit. -
So both amps are NOT common ground. That is most likely the entire issue or part of it. Probably some worn caps as well in the x-over.
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 Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul! -
Neither amp uses a bridged output stage (when in stereo)thus can safely have their negative terminals strapped together to insure a common ground.The Onkyo has some small resistance isolating the grounds of each ch., strapping effective jumpers them.The posted schem. of the Accuphase was not specific enough to show if the grounds were tied together internally or if they are resistively isolated,thus strapping the negative terminals is recommended.
