DIY A1-I questions

strider

I've been waiting for the Fed-ex guy to bring me my pair of SDA 2B's like a kid waiting for the sound of reindeer hooves on the roof on Christmas Eve.

After I won them, I was informed that my Carver M500 will not work with these speakers unless I have an A1-i cable as the speaker to speaker interconnect. I found the PDF from Ken @ Polk CS on how to do this. First read through I was intimidated; subsequent readings I've become a bit more confident that I can handle the construction. Now for the questions:

I beleive I need only 1 of the listed transformers. Are any of the three listed better then the other?

What type of wire should I construct the cable from?

Any particular type of solder to make the connections?

Any words of advice?

Is it that hard to do?

madmax

It is very easy. Just cut the original cable somewhere, put the two wires from one side on the primary side of the transformer and the two wires from the other side on the secondary. It it doesn't sound right swap two wires from either the primary or secondary side of the transformer. Doesn't matter which.

Actually, it does sound too complicated. Just send the parts to me along with $500 and I will be happy to do it for you.

madmax

strider

The speakers I bought didn't include the cable, and the seller was unable to locate it. What should I use to make the cable itself?

Thanks for the offer to build, but I'm a firm beleiver in the teach a man to fish school of thought.:rolleyes:

schwarcw

The original cable is a two wire shielded type. Each wire should be 16 gauge or larger. You can use ordinary speaker wire 16 gauge or larger. I like 12 myself. Check an electric supply house, Home Depot, Lowe's, etc. You can also order some nice Belden cable from Bluejeanscable.com Look here: http://bluejeanscable.com/store/speaker/index.htm

Belden 5000UE cable (12 gauge with gray jacket) sells for $ 0.38/ft. Get say 15 or 20 ft, terminated with spades on both ends. Cut it in the middle and connect it to the transformer like Madmax described.

Good luck! Tell us what you decided to do.

F1nut

It's been said that the Stancor recommended in Ken's info doesn't work properly. Reeltrouble1 posted about it and also posted about the solution. A search for AI-1 should turn up all the info required.

Tour2ma

strider wrote:

After I won them, I was informed that my Carver M500 will not work with these speakers unless I have an A1-i cable as the speaker to speaker interconnect.

Yup... the M-500/ M-500t is the only Carver that's not common ground design.

Here's a link to Ted's thread mentioned above.
http://www.polkaudio.com/forums/showthread.php?t=23442

Good luck...

strider

Just ordered the Stancor p-6412 and the Belden cable from Bluejeanscable.com. Thanks to all for answering questions I'm certain you've answered numerous times. The link to the post regarding the issues with the 6411 really helped, I had overlooked that one during searching.

madmax

strider wrote:

Thanks for the offer to build, but I'm a firm beleiver in the teach a man to fish school of thought.:rolleyes:

Heck, for $500 I'd build your isolator AND teach you how to fish...

Good luck!
madmax

strider

My speakers have the 2 blade style connectors. Which blade, larger or smaller, takes the place of the pin?

I followed the method described here http://www.polkaudio.com/forums/showthread.php?t=23442
to build the cable, specifically post#4, assuming that the larger blade takes the place of the pin.

[Deleted User]

Hello Strider,
Thanks for posting on the Forum. Keep in mind that not all SDA-2B speakers can make use of the SDA AI-1 interface cable. Only ones that have a serial number 14115 for left channel and 14124 for right channel or higher are eligible.
Regards, Ken

strider

My speakers are both higher then the serial numbers noted, I beleive one is 15xxx and the other 16xxx. Are the blade/blade style cable connectors typically found on the speakers with lower serial numbers?

[Deleted User]

Yes, that is correct.

strider

Now I'm concerned. I'm at home looking at both speakers. The right speaker is serial number 16983, the left is 15474. It hadn't struck me as curious 'til now, but isn't that a big difference between the right and left serial #'s? Also, the right says "R SDA 2" on a silver background, the left "L SDA II" on black. Did I get speakers from two different pairs?

schwarcw

I'm not knocking Ken here, he's been wonderful to many, many of us (quite a gentlmen). But this is an area where I would like to see some more imput from the Polk engineers to jump in and make some solid recommendations on how to build this. After all, it's their product development. Since this question comes up often, I'd like to se the engineers spend a few hours to prepare a white paper "DIY" on how to build a home made A1-1 interconnect. Complete with recommeded parts, maybe some specs and assembly instructions.

Same for the pin/blade and the bass brace.

Comments anyone?

F1nut

Strider, post some pics.

Carl, sounds like a plan.

dbnh

schwarcw wrote:

I'm not knocking Ken here, he's been wonderful to many, many of us (quite a gentlmen). But this is an area where I would like to see some more imput from the Polk engineers to jump in and make some solid recommendations on how to build this. After all, it's their product development. Since this question comes up often, I'd like to se the engineers spend a few hours to prepare a white paper "DIY" on how to build a home made A1-1 interconnect. Complete with recommeded parts, maybe some specs and assembly instructions.

Same for the pin/blade and the bass brace.

Comments anyone?

"That ain't workin' that's the way you do it
Money for nothin' and your chicks for free" - Dire Straits

madmax

There are plenty of people here who could do a white paper, submit it to polk and allow them to post it. I'm sure they have a backlog of current items (which pay todays bills) which need things completed.

Maybe we should start a thread and pass around the white paper until it is complete. Each person could "quote" what is already there, add their specific info and past it back in the next reply, and so on.

madmax

strider

First, let me thank everyone for their interest in my dilemna. It's been a dream of mine since I was 10 years old, flipping through copies of my grandfather's Stereo Review, to own and listen to a set of Polk SDA's powered by a Carver amp.

When I get home this evening I'll take some shots of the back of the speakers, specifically the label on the rear and the blade/blade port config.

As for having engineers at the corporate level give their input and assistance I would, of course, be eternally grateful. I was impressed that any company rep would comment on the board. Being a member of other forums for varied interests I've noticed that most companies keep their loyal followers at arms length, maybe using a forum such as this to garner free marketing info.

Thanks again guys,

Ben

F1nut

Ben, take a shot of the fronts with the grills off.

strider

Here are the pictures of the speakers:

http://picasaweb.google.com/strider1975/SDA2B

Sorry they're not in the post. They alternate left to right throughout the series.

schwarcw

madmax wrote:

There are plenty of people here who could do a white paper, submit it to polk and allow them to post it. I'm sure they have a backlog of current items (which pay todays bills) which need things completed.

Maybe we should start a thread and pass around the white paper until it is complete. Each person could "quote" what is already there, add their specific info and past it back in the next reply, and so on.

madmax

I like your idea Max. I was also daydreaming that someone like Signal Cable or BlueJeans Cable would take the schematic, build one and offer it for sale. Even if the price were say $100, I'm guessing there would be some takers. Not many, but 20 or so a year may be worth the effort for a small company that has most of the tooling, materials and is in the audio business.

Carl

F1nut

strider wrote:

Now I'm concerned. I'm at home looking at both speakers. The right speaker is serial number 16983, the left is 15474. It hadn't struck me as curious 'til now, but isn't that a big difference between the right and left serial #'s? Also, the right says "R SDA 2" on a silver background, the left "L SDA II" on black. Did I get speakers from two different pairs?

I looked at your pics and they both look like early SDA 2B's, but those S/N's are so far apart that I'd have to say you got speakers from two different pairs. However, I don't think it'll make any difference in the end.

strider

F1nut wrote:

I looked at your pics and they both look like early SDA 2B's, but those S/N's are so far apart that I'd have to say you got speakers from two differnet pairs. However, I don't think it'll make any difference in the end.

That's cool. Now if somebody could check me on my cable construction, I'll be able to fire 'em up when I get home tonight. As posted earlier, I modeled my cable pretty much exactly like reeltrouble1's in his post. On the left side I've got the big blade attached to speaker cable, then #1 terminal on the the transformer; small blade attached the same way but to the #2 terminal. Right side is the same, big and small connected to terminals 3 and 4 respectively. I know that if it doesn't sound quite right to switch the terminals the blades are attached to on one side. Biggest question is will I fry something if I hook it up and listen?

F1nut

The smaller blade is the equivalent to the pin. Pop off the binding post plate on both speakers, you should see a blue wire connected to the smaller blade. While you are looking, is there a white wire connected to the larger blade?

strider

There's a blue wire connected to the smaller blade, nothing on the large one. So, can I hook them up without cooking anything?:D

F1nut

You know it's strange, but that blade/blade 2B seems to be the only SDA speaker that doesn't have a wire running to the blade on what would be the negative circuit. My gut reaction would be no, you can not hook them up the way you want to.

I'd call Ken and have him ask the EE's what the story is.

strider

Huh.
I didn't wait.

Hooked everything up, threw in Derek Trucks, low volume. Hit play, nothing abnormal. Sat by the rack for a bit to make certain nothing was going to happen right away, still ok. Turned it up a bit, sat down in my listening chair and drank it in. WOW. Even compared to my other Polks, it was like nothing I've ever heard before. After 4 or 5 songs I signed back on to see if anybody had replied, read the post above and shut it down. My amp didn't get even warm to the touch, no feedback, hum, burning smell, etc.

Now I need to wait 'til tomorrow to call Ken. It's going to be a long night, I need a beer.

F1nut

In that case I'd have to say you're golden. Rock on with your bad self.

madmax

You have a problem.


If only the smaller blade is connected there are only two possibilities of how the system is operating.

1. If you have the transformer wired correctly then nothing is coming from your SDA speakers and you just think you are hearing it properly. To get signal through requires a ground to the transformer which would have been supplied by the large blade but is not. Without a ground no sound is coming from the SDA speakers.

(To check to see if the transformer is wired correctly you need to unplug both sides of the cable, place an ohm meter across the large and small blades of one side. You should read a resistance. Not sure what it is but it is probably somewhere between 10 to 100 ohms. The other side of the cable should be approximately the same resistance. There should also be an open between either blade on one side of the cable and either blade on the other side of the cable.)

2. If you have the transformer wired incorrectly so that the signal is going from the small blade, through the winding of the transformer and out the other side going to the other small blade then you may be hearing sound coming from the SDA speakers. In this case what you have is the transformer coil acting as a resistor. This is not correct and is not isolated properly. Although the system works it is not working properly and is not protected.

(To check for this condition you can check with an ohm meter. Either blade on one side of the cable to either blade on the other side of the cable should be open. If you measure a resistance then you know you have it wired wrong assuming the transformer is good, which it probably is.)

You need to solve this problem before continuing on.

madmax

strider

As I was listening last night I covered the stereo driver and the tweeter and beleive I heard sound from the SDA driver. What I heard was at lower volume then the stereo driver, don't know how to describe the sound other then hollow. The SDA driver was moving, but from what I've read the driver will move due to the sealed design of the cabinet, even if it's got no signal to it.

If the transformer was acting as a resistor, wouldn't the output be lower then expected? If that's the case, especially in light of the fact that the amp wasn't even warm after 30 minutes of listening, I'm thinking that the latter of the 2 scenarios is happening.

Can someone suggest a starting point to start trying to figure this out? I'm not the best electrical fault tracer, but I do follow directions well.:o

madmax

Do you have a meter that measures ohms?
madmax