Interconnect cable and tweeter questions for SDA 2B

muncybob

Either the search function is not ideal or I just suck at using it(probably the latter).....anyways, I'm in the process of doing the TL mod. Reworked crossovers are in place(thanks again Mike!) and I'm starting the install of new gaskets and Larry's rings as soon as my Dynamat arrives.

In looking at the wiring diagram for my speakers I see just one wire connected to the interconnect post so I'm thinking of taking a stab at making a new cable and installing a binding post there.
Since my original calble seems to be in decent shape, is this a worthwhile task or should I leave it alone? I've seen how others have made their own speaker and interconnect cable and with a little practice on the soldering iron I think I could do a decent enough job. If there is a thread to doing this I'll be happy to see it!

The RDO 198's have a different size connecting tab for the wires...I guess I didn't pay enough attention to my old tweeters so I'm asking if the red tab on the 198's is the positive terminal?

One last question, appears the Meniscus spikes sold out before I could get around to ordering. I did ask to be notified if new ones become available but it's been awhile and have not heard anything. Anybody know if they are to re-offer the Polk deal from a few months ago?

Joe08867

Red tab is positive. If you do a search you will find a couple of people have done the Binding post instead of interconnect before. It works quite well and you can make any length you need for it.

drumminman

The search function here on CP is a bit onerous. Try using google and put as a prefix www.polkaudio.com/forums and then the topic you're searching for. This works much better for me.

Re: the IC cable and binding post mod, the post at this link is the best I've seen. DarqueKnight is the tweak master :cool::

http://www.polkaudio.com/forums/showthread.php?30467-Improved-SDA-Interconnect-Cables

falconcry72

Just a quick FYI: only the pin on the pin/blade cable carries a signal. The blade just helps keep it in place. Many people just use a single, good quality RCA cable, and remove the "petals" from around the pin so that it goes in the hole deep enough.

muncybob

After reading some of the posts on the cable I'm thinking I'll be in no hurry to do it...seems neglible audio benefit.
In any case, thanks for the repsonses...really looking forward to finishing the update and connecting to some decent power for these to finally shine after the 20 years that I've had them. As Mike and I discussed the other day, wouldn't know even half of what I now know in audio if it weren't for you folks.

inspiredsports

falconcry72 wrote: »

Just a quick FYI: only the pin on the pin/blade cable carries a signal. The blade just helps keep it in place. Many people just use a single, good quality RCA cable, and remove the "petals" from around the pin so that it goes in the hole deep enough.

Post #3 at http://www.polkaudio.com/forums/showthread.php?55888 contains the following SDA 2B drawings

-- SDA 2B 1987-bb Sch.pdf (P0132002 dated 09/13/1987)
-- SDA 2B 1987-pb Sch.pdf (P0132003 dated 10/26/1987)
-- SDA 2B 1989 Sch.pdf (P1032003 dated 07/26/1989)

Someone with more EE than I help me out here, but both pin/blade P0132003 drawings seem to be telling me signal DOES travel through both wires. The blade side may not be necessary, but it IS in-circuit if I'm reading those engineering drawings correctly.

I agree that the blade/blade clearly shows just one wire in-circuit.

drumminman

inspiredsports wrote: »

Post #3 at http://www.polkaudio.com/forums/showthread.php?55888 contains the following SDA 2B drawings

-- SDA 2B 1987-bb Sch.pdf (P0132002 dated 09/13/1987)
-- SDA 2B 1987-pb Sch.pdf (P0132003 dated 10/26/1987)
-- SDA 2B 1989 Sch.pdf (P1032003 dated 07/26/1989)

Someone with more EE than I help me out here, but both pin/blade P0132003 drawings seem to be telling me signal DOES travel through both wires. The blade side may not be necessary, but it IS in-circuit if I'm reading those engineering drawings correctly.

I agree that the blade/blade clearly shows just one wire in-circuit.

I'm no EE, but I recall reading here on CP that only the pin carries the signal. The blade is connected to the negative binding post and is used for stability of the connection and testing purposes.

I did notice a marked improvement when I installed the binding post and used high quality 12 awg speaker wire with spade connectors.

inspiredsports

drumminman wrote: »

I'm no EE, but I recall reading here on CP that only the pin carries the signal. The blade is connected to the negative binding post and is used for stability of the connection and testing purposes.

I did notice a marked improvement when I installed the binding post and used high quality 12 awg speaker wire with spade connectors.

The blade side of the circuit on a normally connected pin/blade is DEFINITELY and DIRECTLY connecting the negative (white) wire of each tweeter in each 2B cabinet through the length of the interconnect cable.

I believe the interconnect would act as a tiny resistor/inductor/capacitor between the negative sides of the tweeters depending upon the specific characteristics of that leg of the interconnect wire.

If you are using only pin to pin, you are not making this direct grounding connection between tweeters, and grounding only occurs through the negative side of EACH length of your speaker cables.

Whether this difference in circuitry makes a sonic difference, I don't know.

I do know that Polk changed (lowered) the impedance value of the polyswitch used between early blade/blade where the polyswitch was .50 ohm and later pin/blade models where that chunk of interconnect wire was between tweeter minuses used polyswitches with about .25 ohm polys. (perhaps taking this into account?)

gmcman

I'm also curious as to what effect connecting the blade will do.

Safe assumption that it's not only for stability? Does the speaker NEG just offset this connection or does it change the impedance enough to change the SDA effect?

gimpod

The blade being connected to the ground post is done so you can use the Polk AI-1 I.C. for non common ground amps. On ALL pin/blade SDA's the tweeter is NOT part of the SDA circuit.