SDA 2A vs SDA 2B

renowilliams

For those of you who have owned both.. is there any real difference in imaging, soundstage bass etcc.... ??

Joe08867

Wider Soundstage(sweetspot), Tighter bass, and you can TL 2b's. Which makes them superb.

heiney9

renowilliams wrote: »

For those of you who have owned both.. is there any real difference in imaging, soundstage bass etcc.... ??

yes, yes and yes. It's subtle for sure but there were always incremental improvements made in cabinets, drivers, x-overs, design tweaks from one generation to another in SDA's. My advice is to always get the newest SDA you can 1) afford 2) available in your area.

H9

pitdogg2

whoa dude you men to tell me i CAN'T TL my 2a's :eek:
that's totally jacked up


2a's for sale cheap Wnew XO's









































J/K :biggrin: carry on

audiocr381ve

Please don't go getting rid of your SDA's. You know as well as I do how much you enjoy them, especially after reading your thread a few days ago. The grass isn't green on the other side! Although their may be improvements, don't believe the lie that ultimate audio satisfaction will be had by upgrading, it's all in your head haha.

Audiophiles and discontentment go hand in hand! Be content! (I'm speaking to myself here )

heiney9

audiocr381ve wrote: »

The grass isn't green on the other side! Although their may be improvements, don't believe the lie that ultimate audio satisfaction will be had by upgrading, it's all in your head haha.

Ah, but the grass is greener if you make the right choices. ^^ that there, is a foolish statement.

H9

audiocr381ve

heiney9 wrote: »

Ah, but the grass is greener if you make the right choices. ^^ that there, is a foolish statement.

H9

danger boy

the SDA 2B's are heavier sounding to me... more bass.. but not exactly better bass... just heavier - weighty and maybe a little to bassy, if that makes sense.

had I never owned a pair of 2B's.. i would prob still have the 2A's.. both nice, but different...

Joe08867

Danger, I never noticed that but now that you said that I agree. I will say that the 2b's were more forgiving of placement than the A's were.

I know I have had my b's set up wrong a few times and they still shined the a's had to be just right.

heiney9

One of the advantages to furthur engineering is later SDA's are more forgiving about placement because of the advancement in x-over having to do with the dimensional signal. Later SDA's have better off axis response.

That's why I always suggest getting the latest SDA you can afford. People can look at specs, etc and it doesn't tell the whole story.......as usual.

H9

renowilliams

I guess by what your saying H9 then, is 3.1's would be good to get then?

inspiredsports

pitdogg2 wrote: »

. . . whoa dude you men to tell me i CAN'T TL my 2a's :eek: that's totally jacked up

Joe08867 wrote: »

Wider Soundstage (sweetspot), Tighter bass, and you can TL 2b's. Which makes them superb.

I don't see any reason you can't TL the 2A's.

The high-pass section has the same 2.7 ohm resistor (that would receive the 5.8uf bypass cap) followed by a 12 uf cap. There's an additional 2.7 ohm resistor in series with the .4 mH inductor used within the high pass to match it to the 4 ohm 6510 midwoofers (instead of the 8 ohm 6503/6511 combo used in 2B's), but I don't think that affects the move to an RDO198 and the addition of a 5.8uf bypass cap.

The 4 ohm 6510's are very good sounding midwoofers, they just require a huge amount of capacitance (2 giant 130uf's). I think the upgrade to the 6503/6511 pairing back in the day by Polk was more about switching to an easier to drive 8 ohm architecture and getting those large (expensive) caps out of the mix, versus improving sound quality.

Yes the 6503/6511 sound quality is slightly better, but the impedance issue and cost to source 2 130uf caps per cabinet was a biggie.

Anyone else have any ideas about this?

Joe08867

My SDAII have the Three 6501 Drivers per cab. These are the originals not the two drive SDA2A's.

I am a bit confused how the TL would work on them. I guess just adding the one cap to the tweeter circuit would do it but with the dimensional tweeter I am guessing something else would need to be done.

inspiredsports

Joe08867 wrote: »

My SDAII have the Three 6501 Drivers per cab. These are the originals not the two drive SDA2A's.

I am a bit confused how the TL would work on them. I guess just adding the one cap to the tweeter circuit would do it but with the dimensional tweeter I am guessing something else would need to be done.

Most models can't be TL'd, but if the high pass circuit design is + speaker terminal --> to polyswitch --> to 2.7 ohm resistor --> to 12 uf Capacitor --> to tweeter + terminal, it seems bypassing that initial 2.7 ohm resistor with a 5.8 uf cap and replacing the SL2000 with an RDO198 would work. I guess on the other hand it could lead to a FrankenPolk.

Joe08867

I don't mind a Frankenpolk as long as it sounds like a Polk still.

Do you think I would have to do the same for the dimensional tweeter? It wouldn't be hard to do just wondering if it is necessary or not.

I have a third pair of SDAII's that are definite Frankenpolks. They had four bad drivers that were replaced with aftermarket cheapo poly mids. I am still playing around with them as a side goof project. They actually sound nearly as good as my updated ones.

I may get some high end Kevlar Mids and Vifa tweets to really frankenpolk them out.

geppy1

Having had 2Bs and now 2As I do not see one as better just slightly different. Both have been tried with SL2000s and RDO194s. Both have been dynamated and mortited. Both have had a much heavier IC made but one was pin blade and one was blade blade. Both had some insulation added.

I think the sweet spot on the 2b is slightly larger but the sound stage on the 2As seems wider and deeper. Not as much of a billboard effect. Also the SL2000 seem more tolorable in the 2Bs whereas in the 2As it is more annoying. Your mileage may vary.

inspiredsports

Joe08867 wrote: »

I don't mind a Frankenpolk as long as it sounds like a Polk still.

Do you think I would have to do the same for the dimensional tweeter? It wouldn't be hard to do just wondering if it is necessary or not.

I have a third pair of SDAII's that are definite Frankenpolks. They had four bad drivers that were replaced with aftermarket cheapo poly mids. I am still playing around with them as a side goof project. They actually sound nearly as good as my updated ones.

I may get some high end Kevlar Mids and Vifa tweets to really frankenpolk them out.

This was a point of contention when I TL'd my SDA SRS 2's. It is similar in that they use 2 tweeters per cabinet, although they are in an "array" working together only on the stereo side of things. There is no dimensional tweeter in the SDA SRS 2, in fact I believe your "2's" are the only model that had an SDA tweeter.

The signal to the second tweeter in the SDA SRS 2 is diminished a bit by a second 2.7 ohm resistor in the circuit to roll off it's volume; it puts out a lot less volume (maybe 6db quieter?) than the "primary" tweeter. I looked at your SDA 2's schematic and see that while the Dimensional tweeter is separate, it is also "rolled off" behind a 3.5 ohm resistor that cuts the signal that reaches it.

The point is, and speaking to your question, I tested the second (quieter) position both ways in my SDA SRS 2's, meaning I left the second tweeter as an RDO194 (SL2000) and then TL'd it by dropping in an RDO198.

The speakers sound fine BOTH WAYS. It was splitting hairs to replace the second tweeter, only a few percentage points better, but being fanatical I did replace it with an RDO198. In the case of your second tweeter actually being in the dimensional circuit, it may have a more pronounced effect, but I doubt it.

What is beyond my pay grade is that your dimensional tweeter circuit is started off with a 3.5 ohm resistor instead of a 2.7, and that is the spot where the 5.8uf bypass would go. I'm just not sure what happens when you place the 5.8uf bypass cap over a 3.5 ohm, resistor instead of a 2.7 ohm resistor which is used in all of the models where the TL mod is prescribed.

I hope this helps, but I say give it a try on just the stereo side and see what happens. My guess is that it will improve things a bunch. If you like it, add the 5.8 and RDO198 to the dimensional side. Sell the parts you don't need after several hundred hours of listening and you'll be in business.

(I've been giving my tube rig a rest most of the week because I just received a bunch of new vinyl and have my best turntable connected to my solid state rig which is driving the TL'd SDA SRS 2's. I've been enjoying them for about the last 30 hours of listening with a big, wide smile on my face. )

heiney9

inspiredsports wrote: »

in fact I believe your "2's" are the only model that had an SDA tweeter.

If you are talking just for the model 2 SDA you are correct, but all early SDA's had dimensional tweeters

SDA 1; SDA 1A; SDA 2; SDA 2A. Of course as usual there were transitional models that were called by the same model number but were a newer generation.

I have no idea how you could "TL" a model with dimensional tweeters, doesn't seem possible since they aren't a progressive point source or single tweeter model.

H9

inspiredsports

heiney9 wrote: »

If you are talking just for the model 2 SDA you are correct, but all early SDA's had dimensional tweeters

Yes, I should have clarified within the "2" series.

heiney9 wrote: »

. . . I have no idea how you could "TL" a model with dimensional tweeters, doesn't seem possible since they aren't a progressive point source or single tweeter model. H9

I'm not clear on what you mean by this. TL was just a marketing designation to hype the material/process used in producing the newer tweeter; Tri-Laminate

TL'ing would have nothing to do with the number of tweeters involved or how they are/are not arrayed, only determining a way to properly electronically transition the circuit(s) involved from SL2000/RDO194/(and maybe SL2500) to SL3000 (RDO198).

JPSmario

heiney9 wrote: »

If you are talking just for the model 2 SDA you are correct, but all early SDA's had dimensional tweeters

SDA 1; SDA 1A; SDA 2; SDA 2A.
H9

I have the SDA2A's; one tweeter per cabinet only. This is also what the schematic in the compendium for the 2A's shows.

Jim