SDA SRS How do they work ?

[redbullet]

Ok, Like to know how the SDA SRS work. I can kind of grasp the older versions with the muti-conductor cable, But how do the single wire versions?.
If memory serves me correctly, The originals would feed the left channel out of phase to the right channel and visa versa. But is this true of the late single cable versions.:confused:

[dorokusai]

SDA's all work the same.

Multi-Conductor cable?

[redbullet]

SDA's all work the same.

Multi-Conductor cable?


If I remember the early ones had three pins later used both wires Then the last pin only.

[dorokusai]

There are some odd connections on the early models but it's not important. Traditionally only one of those "conductors" or terminals is neccesary. The blade/blade connector has two terminals but only one is used, the other is for support of the cable, at the loudspeaker. The pin/blade is the same way, the pin being the active connection....the blade being the supporting terminal.

I can't comment on the construction of the DIN socket model, as I simply don't remember. One of the other Polkies can answer that.

[schwarcw]

Here's a link to a SDA "White Paper" Matthew Polk wrote. Look Here (http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf)

[lightman1]

Thanks Carl. Good read there for anyone who wants to know the idea for SDA came about.

[redbullet]

Here's a link to a SDA "White Paper" Matthew Polk wrote. Look Here (http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf)

Good reading still just trying to figure out how they do left right information across one wire.

[Joe08867]

The Din Socket worked the same also. Only one wire carries the signal. My guess is they used the Din instead of making there own plug to save early developement costs or something like that. This way if it didn't take off they would have lost more money.

I have the Din style connector on my original series SDA2's.

[dorokusai]

Thanks Joe.

[schwarcw]

Thanks Carl. Good read there for anyone who wants to know the idea for SDA came about.

You're welcome!

[lightman1]

Good reading still just trying to figure out how they do left right information across one wire.

Common ground to both speakers from the amp (?)

[DarqueKnight]

Good reading still just trying to figure out how they do left right information across one wire.

The same way a road can have traffic traveling in two directions simultaneously. I posted an explanation for this a while back. You should be able to find it with the search function.

[redbullet]

The same way a road can have traffic traveling in two directions simultaneously. I posted an explanation for this a while back. You should be able to find it with the search function.

Can't seem to find that post, I would like to read it.

[DarqueKnight]

See post #9 of this thread:

How Does SDA Work? (http://www.polkaudio.com/forums/showthread.php?t=48162)

Post #6 of the thread has a link to a white paper that explains SDA in more detail. Refer to pages 2-6 of the white paper.

[redbullet]

See post #9 of this thread:

How Does SDA Work? (http://www.polkaudio.com/forums/showthread.php?t=48162)

Post #6 of the thread has a link to a white paper that explains SDA in more detail. Refer to pages 2-6 of the white paper.

Thanks, BTW guess the Compendium is no long available?

[DarqueKnight]

The Compendium has passed on into audio lore.

[Lasareath]

The Compendium has passed on into audio lore.

It's so true! The Compendium has found its way into an elite section of my library. right next to the Bob Marley 30th Anniversary Exodus Book and the Carver TFM-35X original manual.

[SDA SRS 1.2]

The Compendium has passed on into audio lore.

My first edition sits on top of my left speaker and the second sits on the right for handy reference - I swear they make the 1.2's sound better! :)

[Marty913]

There are some odd connections on the early models but it's not important. Traditionally only one of those "conductors" or terminals is neccesary. The blade/blade connector has two terminals but only one is used, the other is for support of the cable, at the loudspeaker. The pin/blade is the same way, the pin being the active connection....the blade being the supporting terminal.

I can't comment on the construction of the DIN socket model, as I simply don't remember. One of the other Polkies can answer that.

So now I'm confused. My SDA2's (blade/blade) have two wires (blue, white) from the SDA connector to the Dimensional crossover board, and then onward to the dimensional tweeter and dimensional mid. The white is ground so the blue is carrying the difference signal. Right? Could I then assume that the "ground" is needed to complete the difference circuit path and that the second blade is not just for support (in which case it would not need any wire connected to it) but is required to ensure common ground between the two SDA crossovers. :confused:

[DarqueKnight]

So now I'm confused. :confused:

In most blade/blade SDA's, both the wide and narrow blade (called pin #1 and pin #2 on the schematics)carry a signal.

In the pin/blade SDA's, only the pin carries a signal and the blade only provides mechanical support. However, the blade connect in pin/blade models is used for testing and diagnostic purposes. The pin/blade cable does contain two wires, but they are both connected to the pin. There is no electrical connectivity between the blades of the pin/blade cable.

When Polk was transitioning from the blade/blade to the pin/blace cable, some models that were designed to use the pin/blade cable, such as the SDA 1C and the SDA 2B, were retrofitted with blade/blade SDA cable sockets and cables. This was done in order to use up parts stock.

In the retrofitted SDA 1C and SDA 1B models, the electrical connection was the same as with the pin/blade cable, in that only one blade (the small blade, pin #2) was active.

If you go to the vintage speakers section of the forum and refer to the SDA schematics for the SDA 2A, SDA 2B (blade/blade) and SDA 2B (pin/blade) you will note the following:

1. On the SDA 2A schematic, the wiring connections for the the SDA cable are different at each speaker and thus each blade carries a signal.

2. On the SDA 2B blade/blade schematic, only the small blade (corresponding to the pin in pin/blade cables) has connectivity.

3. On the SDA 2B pin/blade schematic, only the pin has connectivity.

[DarqueKnight]

Could I then assume that the "ground" is needed to complete the difference circuit path and that the second blade is not just for support (in which case it would not need any wire connected to it) but is required to ensure common ground between the two SDA crossovers.

That is correct.

In the pin/blade cable, the ground connection is provided through the common ground path in the amplifier.

[Marty913]

That is correct.

In the pin/blade cable, the ground connection is provided through the common ground path in the amplifier.

Thanks DarqueKnight, as always you have been very helpful. I know this isn't "world-affecting" stuff and I'm usually lost when it comes to electrical engineering but I was scrounging around inside my 2's over the weekend (obviously no life at all :o). I saw the two connectors and remembered the posts about only one wire needed for SDA. I figured since it was ground they must have used the amp-ground in later models. Might be why A-I doesn't work with true blade-blade. :p

Regardless, it's worth documenting here that "some" SDA's require ground between the two dimensional crossovers. I doubt any damage would occur but I'm pretty sure there wouldn't be any SDA affect. :eek:

Thanks again.

[John in MA]

My first edition sits on top of my left speaker and the second sits on the right for handy reference - I swear they make the 1.2's sound better! :)

You must have the version with the magic beach rocks sewn into the cover. :)

[Marty913]

You must have the version with the magic beach rocks sewn into the cover. :)

And all of his CD's have green magic marker stripes on them.