SDA Interconnect Question

JCL

I just picked up a pair of SDA SRS 2.3's and I'm having problems with the SDA effect. Anyway I went through the test procedure that Ken faxed to me and went through it. It appears that all measurements of the posts etc are within spec.

When I performed the tests in mono several strange things happened. When performing the second test where you have the source in mono and disconnect the black terminals the speaker is supposed to actually get quiter when the balance is centered and be louder in the left and right positions. Mine actually got louder! So I checked the SDA cable for continuity. The pin to pin connection checks out as continuous but the Blade to Blade connection is null. Does this mean that the cable is bad?? If its bad can a cable be made from two seperate wires or is the cable supposed to behave this way. Also will a direct connection of the speakers on these two connections cause a problem? I'd hate to fry something!

Any help would be greatly appreciated. Thanks in advance.

BlueMDPicker

My SDA 2A (blade/blade) cables show continuity for both blades.

My take on this is that one conductor creates a common ground between the speakers, the other samples opposing channel output for crosstalk cancellation through the SDA drivers. I'll throw the VOM on the SDA SRS IC in a bit, but I think my results will be the same.

JCL

Thanks!! I'm making a cable up right now out of two spades and a pin connector. I will wait to here back before connecting it to the speaker.

bikezappa

Fix, get, or make a cable.

Hook it up and smile.

Peter

BlueMDPicker

SDA SRS cable (blade/blade) shows continuity for both pins.

My 2Bs have a pin/blade. I'll check those as well a little later.

BlueMDPicker

From and old thread by Ken of Polk CS:
"The bade and the pin are both connected to the same wire in the original SDA pin/blade cable. This was done to prevent owners from damaging their non-common ground amplifiers. All that would happen would be that there wouldn't be any SDA corrective signal present, but the amplifier wouldn't be shorted out. If the amplifier was a common-ground design it would provide the necessary left/right grounding and the SDA would be heard. So, the pin does one of the connections and the amplifier provided the second. When building a pin/blade cable there's no need to connect the blade, since the amplifier will provide the connection."

Hmmmm? If both are connected to the same wire, I can't understand how you lack continuity in the pin on your cable. At any rate, it appears you won't fry anything to have them both continuous.

JCL

Well that didn't work well. I get some pretty nasty noise and the amp protection circuit comes on after a few seconds at low volume. I'm pretty sure a carver m200t is a common ground amp. Fortunatly everything still sounds OK. Is ther any way to safly check the amp to see if its common ground?

I get continuity only with the pin to pin connection not pin to blade or blade to blade. I pulled the passive radiator and there are wires running to both connections internally.

BlueMDPicker

If you're making your own cable, even temporarily, try using a single conductor with pin on both ends. Leave the blade out of the equation (per Ken's logic above.) That shouldn't create any havoc.

Sorry, I know nothing about the design of your Carver amp.

If I may rewind a bit, were the speakers working properly for the previous owner? Was he/she using the SDA interconnect? Is it possible someone rewired the drivers for stereo operation only?

F1nut

There's nothing wrong with your pin/blade cable, so leave it alone. I still think it's in the wiring. Polk uses white or the light colors as the negative and black or the darker colors as positive.

JCL

I have looked at both crossovers and the internal wiring of both speakers and can find nothing that was changed. All of the wiring in the cabinets still has the factory glue covering all of the connections so I do not believe they were modified in any way. The previous owner said that he was using the cable in his setup. Since it looks like the connectors in the cabinet to the SDA cable are seperate I think I will call Ken again tomorrow. I'm afraid I may ruin something now.

Does anyone know if Sunfire amps are common ground? That is what I was going to buy to drive these anyway.

F1nut

Check the speaker ends to see if those wires got reversed.

You can check for continuity by using a VOM on the two negative posts. If you see zero you have a common ground amp.

JCL

I connect a VOM to the two negative connections with the amp off and I do not get zero. Which I think is good.

I have checked and rechecked the connections and if I follow the test procedures Ken sent me I have to wire one of them out of phase to get part one of the checkout procedures to work. When I try part two which is to disconnect the black terminals, play a mono signal, and move the balance from left to right. In the center there should be little to no noise present but in my case the volume actually goes up. They should be cancelling not adding unless there is a misprint in the instructions he sent me (which I doubt). This is the part that worries me.

I then checked the DCR points and all resistances seam to fall within the acceptable error provided.

I should add that when they are connected with the right channel out of phase (part one of the test) I get a much wider soundstage, but the effect does not seam to pinpoint some of the lead vocals. i remember demoing a set of these when they first came out and I do not recall hearing this.

F1nut

Can you post a pic of your speakers, grills off and one of the **** end?

disneyjoe7

Originally posted by F1nut
You can check for continuity by using a VOM on the two negative posts. If you see zero, then you have a non-common ground amp.

If you see "Zero" then you have a non-common ground amp?

Are you sure, I think if you have zero ohms between the negative posts is a common ground amp.

JCL

I will try to attach two photos. First photo:

JCL

Second Photo:

F1nut

Thank you Steve for pointing out the errors of my ways. Rule #1, never post when ragged out from a hard day.

F1nut

Ok, the fronts look like 2.3's, but I'm wondering why the back says System 2? Maybe John Strong can chime in here as I know he has the same speakers.

JCL

Judging from your previous post if the VOM is showing an open circuit when both channels are connected by their respected grounds then I assume I have a non-common ground amp. Which means I will have to get a new amp sooner than expected LOL. Hopefully that is the problem. I assume the amp should be off for this test.

F1nut

Yes, I stand corrected. It would seem as though you have a non-common ground amp and yes, you should test it turned off. Sorry for the earlier confusion.

JCL

I checked the back of the amp again and the amp has a ground shown between the + (right side) and - (left side) to the chassis. I believe this is still considered common ground but it is an inverting amp which may be causing some of the problem and explains why the terminals have to be inverted on the right side speaker for any SDA effect to be present. I will try to contact Ken today.

BlueMDPicker

Do you have another source of amplification at all to test with - even a modest powered receiver or AVR? That would quickly take the mystery out of the common ground issue. Perhaps a friend could bring a piece of gear over to help in nailing down the problem?

Sorry you're having such a time of it with your SDAs. And, I hope you solve the problem and can start enjoying them soon.

Mike

JCL

I spoke with Ken and it appears that the speaker is probably functioning correctly. The problem most likely is in the design of the amp and how the common groung and inverting is accomplished. Looks like I will be upgrading my amp sooner than expected. Any suggestions on a good quality multichannel amp??

BlueMDPicker

I'd suggest checking AudiogoN for a good used amp if you don't have a local resource to audition components in your area. As Madmax once put it "let Richy Rich pay retail for it, then buy it used for half price when the upgrade bug hits."

Popular gear includes Sunfire, Rotel, Rogue Audio, Denon, B&K, Parasound, Conrad Johnson, Outlaw and Adcom (to name just a few.) Find something that sounds interesting, with the features you want, and read as many reviews as you can find. From time to time, some nice deals crop up on the flea market here. It sounds like you're a motivated buyer at the moment, though. Have fun! The SDAs are addictive. Welcome to the illness.

Mike

JCL

Thanks for all the suggestions and help!!! I really aprerciate it. I'm familiar with Audiogon but probably wont be purchasing anything from anyone unwilling to do PayPal there. I had a very bad experience there with a preamp and ended up having to go to E-Bay to pick one up.

I've been looking at Sunfire, Rotel, B&K, EAD, and Adcom for a while. While I really want to get a Sunfire, but I have to make sure I will not have the same problem since Carver designed that and my current amp. I'll have a buddy bring one over this week and see how it sounds.

JCL

Tried a Sunfire amp last night. Wow what a differance. Everything seams to be functioning correctly. Wide and deep soundstage with pinpoint focus. So the problem was most likely with the amp design having an inverted channel.