Original SDA SRS Help Needed!

jtconnell · May 2003

I have an original pair of Polk SDA SRS speakers (the ones with eight 6503 dirvers per cabinet.) The dates on the crossovers are 10/29/86 and 1/22/87 respectively. Unfortunately, the pair I have consisted of two left speakers and Ken kindly supplied me with the wiring schematic so I could convert one of the left speakers to a right speaker.

I performed the change out and have the following issues:

1) The balance only seems to work on one side with respect to the SDA drivers. Basically, when I turn the balance all the way to the left the left speaker plays normally and the right speaker's SDA drivers play less loudly. When I turn it all the way to the right, the right speaker plays normally, but there's hardly a peep from the left side. I'm guessing that it's a crossover issue in the right speaker but what to do?

2) When I have the volume up, there is a slight, but noticable hum coming from the right speaker without any music being played. No such thing on the left side. Any ideas? They still sound good when music is played.

3) The lowest tweeter on the right speaker is blown or it's yet another crossover issue. I haven't tested it against another tweeter. The other three in the same cabinet appear to be just fine.

As a final note, the wiring diagram calls for the interconnect cable plug to be modified as follows: the left channel should have pin 1 connected to the oututs of the 130 microfarad capacitors (green wire and broad blade?) and pin two connected to 2.75 mH coil (black wire and thin blade?). The right speaker sound be the mirror image. I had to do this work during the conversion. I'm guessing that this has little to do with the problem, but perhaps I'm sadly mistaken. Honestly, which pin is 1 and which one is 2?

Finally, I noticed that the drawing was revised in 2/87 and a 92 microfarad capacitor was added in parallel to a 2.7 ohm resistor. Any thoughts why? Is it worth doing the modification? Are there any other upgrades that are worth doing to these speakers?

I'd really like some help because I'm stumped! Any assistance would be greatly appreciated!

Tour2ma · May 2003

jtc,

Wow this is a unique one, except for the guy out there who owns two right ch SRS's...

Pretty much talking over my head here, but as a fellow SRS owner I'll offer what I can until the cavalry, har or gidrah, comes along. They have both tweaked SDA's.

Best I can do is to advise you to ask Ken for a copy of the SDA troubleshooting guide. Its a comprehensive little document that walks you though all the steps to check both the basic and SDA functions of any speaker in the line using only a VOM. While youre at it ask for a copy of the owners manual also, if you dont have one.

Only condition I am even tempted to comment on other wise is #2, concerning the hum. Ive had experienced this in the past and it has always been attributable to an oxidized interconnect, usually at my power amps RCA in (not gold plated). If youre running a receiver, this cant be it, but if you have separates, try making and breaking the RCA plug on the offending channel (amp turned off) and twist it as you do.

Ill alert har to your issues, but contact Ken about the guide.

Good luck and welcome to the Club.

DarqueKnight · May 2003

JT,

I also have the SDA SRS and a copy of the schematic that notes the 92uF capacitor addition.

One thing you have to realize, is that each set of SDAs is a mirror imaged pair. In other words, if you are standing in front of your SDA SRS's and facing them, the left speaker would have the four SDA dimensional drivers along the left side of the left speaker and the four stereo drivers would be along the right side of the left speaker.

Now, you say you have two left speakers and that you converted one of the left speakers to a right speaker. Such a conversion would involve more than just a crossover modification because the driver arrangement of the right speaker must be the mirror image of the left speaker. If you are using two left speakers, you do not have a mirror image.

In order to properly convert the left speaker to a right speaker, the four dimensional drivers on the left side of the speaker must be switched with the four stereo drivers on the right side of the speaker. The crossover wiring of the "right" speaker must be reverse wired per the schematic.

Even though you have done the crossover modification, you essentially still have two left speakers.

When the crossover wiring is modified correctly and the 6-1/2" drivers in the "right" speaker are switched, you should hear the following:

1. With the SDA cable attached, if you move the balance control all the way to the left, you should get sound from all the drivers of the left speaker. The right speaker will have only the tweeters and the SDA dimensional drivers along the outer right edge playing. If you move the balance control all the way to the right, you should get sound from all the drivers of the right speaker. The left speaker will have only the tweeters and the SDA dimensional drivers along the outer left edge playing.

2. With the SDA cable disconnected, if you move the balance control all the way to the left, you should get sound from only the stereo drivers along the right side of the left speaker and the four tweeters. The right speaker should have no sound coming out of it (assuming there are no crosstalk problems with your amp or preamp). If you move the balance control all the way to the right, you should get sound from the stereo drivers along the left edge of the right speaker and the four tweeters. The left speaker should have no sound coming out of it (assuming there are no crosstalk problems with your amp or preamp).

jtconnell · May 2003

Okay, first I want to thank everyone for their kind responses. Have you ever been so close to something you could taste it, and then can't find it. I feel like I'm trapped in some kind of Pink Floyd song. It just doesn't make sense!

When I converted the left speaker to a right speaker, I also changed the positioning of the drivers and their associated wires. In other words the blue/green wires that powered the SDA effect and the Blue/White wires that powered the Stereo Effect were reversed in the cabinet. I did nothing with those wires on the crossover. Before I did the modifiaction, the amp would shut down before it got too loud with the interconnect cable connected. I figured this was due to the interconnect cable not being properly wired. Changing that solved that issue. They now play loudly, but I only get the SDA effect from the modified right speaker.

Following your advice, I took out the interconnect and, as near as I can tell, the Stereo Drivers (inboard) are playing. I don't think the dimensional drivers are, but it's hard to tell without taking them out of the cabinet since it's all sealed up.

So, to summarize my modifiactions, I:

1) Changed the interconnect cables.
2) Swithed the wires from one side of the cabinet to the other

I didn't change the drivers since they're all 6503s. I didn't see the point since they were the same.

Should I have done something else? Looking at the Xover board, I 've got the following arrangement on the modified cross over.

From the top row where the tweeter connections are, I have (ignoring the tweeters) L1 (Black and White), L2 (Blue and Green) and L3 (nothing). This is how they came originally and all connections are soldered.

One the bottom row, I have Y, R, L3 (white), L1 (black), L2 (black which I switched to green long blade) and G (green which I switched to black thin blade).

The other crossover is in it's original state. What am I missing? I'm one confused Pittsburgher!

Tour2ma · May 2003

Pittsburgh... damn that explains it. Cleveland born and raised here.

Hang in there... I'd initially forgotten about raife. As you may already be able to tell, he's an SDA afficionado and major tweaker.

Do be sure to call Ken on that troubleshooting guide. If you're close, and it sounds like you are, it will be a big help getting you home.

jtconnell · May 2003

Yeah, yeah, blah blah. I should say I'm an adopted Pittsburgher. I'm originally from the great state of Indiana and a Purdue transplant to boot which probably only lowers your opinion of me even further. Nonetheless, I appreciate the help and I won't say anything about the Browns -- for now.

I've wanted a pair of these speakers since I first saw them in 1986 and now that I've got them, my inability to get them to the state they should be in is nerve racking! The thing is, though, they still sound good even though I KNOW they're not at their best yet. It's driving me nuts!

I did follow your advice and sent Ken an e-mail. So far I haven't gotten anything but I do have a DVM that I'm ready to rock with.

DarqueKnight · May 2003

JT,

I will take a look inside both of my SRSs and see where all the wires run. I won't be able to do it until tomorrow though. At least then you will have a wiring reference.

jtconnell · May 2003

You are the man! Thanks so much for the help!:)

DarqueKnight · May 2003

JT,

One other thing I just thought about: What amp are you using? Is it a common ground amp?

Sometimes a non-common ground amp will work with SDAs provided you don't play a lot of bass-heavy music that makes the impedance drop too low.

har_navalta · May 2003

I'm kinda late in here, but anyway raife is the right person to
answer all of these problem since he has the SDA SRS also has the SDA SRS 1.2TL. He is the Original tweaker of SRS's.

I still suggest you call Ken S. at Polk, he will point you in th right direction of what to do or you can send it to them your X'over for
repair if necessary.

Har

jtconnell · May 2003

I'm using an older Yamaha RX-530 receiver as a test amp. Not a lot of power, but it's pretty clean. I use it primarily to power a pair of Polk Monitor 4s. I'll eventually be using a Luxman R-117 until I get something nicer. I think both of these are common ground amps. By the way, it seems like the stereo drivers on the modified right speaker exhibit more excursion than their counterparts. That might be a speaker wire issue, but I thought I'd thow that in.

DarqueKnight · May 2003

JT,

How did you end up with two left SRSs?

har_navalta · May 2003

They might have made a mistake when someone bought the speakers and had it delivered. It probably had two left channels when the person received it and he never noticed, that's how it probably happened.

jtconnell · May 2003

Your guess is as good as mine. What's really strange is that the dates on the cabinets are way different (one from 10/86 and one from 12/87). I'm guessing -- and it's a guess -- that when the 1.2 models came out, the original purchaser made a deal with a dealer and was none the wiser.

Even more interesting is that the drivers on one speaker have the cardboard doughnuts surronding them whilst the other speaker doesn't. All of the drivers were made in July, 1991. Care to hazzard a guess about that one? The ones with the doughnuts seem to have better excursion as I previously mentioned. I haven't a clue what the doughnuts add.

har_navalta · May 2003

Also I am guessing that the original owner have SDA SRS 2.3's with the cardboard doughnuts driver, swapping the 6503's driver to the 2.3's and the doughnuts to the one you have now.

jtconnell · May 2003

All of the drivers are 6503s. I don't think the seller has anything else and if she did, I doubt she'd know it. these came out of an estate. Also, I only thought the 6503s were used in the SDA SRS, SDA SRS 1.2, 1.2tl and 3.1tl. Besides cosmetics, what are the doughnuts used for anyway? I find it odd that I've got one with and one without.

DarqueKnight · May 2003

The "doughnuts" were used on the SRS 2.3 to enhance bass response by adding mass to only one of the drivers.

I am thinking that someone blew the original drivers for your SRSs and ordered the wrong replacement drivers.

har_navalta · May 2003

If I were you, instead of correcting all these problems, I'd tweak these SRS's to TL version instead.

jtconnell · May 2003

Being a newbie, I need to be clearer. I think I understand what you guys are saying, but it's not what I meant. If I understand you right, certain 2.3 models had cardboard doughnuts affixed to the driver cones themselves to enhance bass response. This isn't what I'm talking about nor is it what I have. All of the 6503s on my SDAs are the same.

The "cardboard doughnuts" I'm referring to are the ones that go on the outside of the butyl rubber surrounds and are flush with the mounting hardware. They cover the seam where the rubber surround is bonded to the metal frame. I don't know what they're called or what they're for, but that's what I've got. One speaker with and one without. As I previosly mentioned, the one with seems to have deeper excursion, but it could be a wiring issue and I haven't investigated any of that further.

With respect to your second point, how do I make such a conversion aside from buying 1.2TLs when they become available? I was the guy who lost the $2,400 bid on ebay. I didn't think anyone would pay that much for a set. Before I bid they were sitting at $1,900, so I really helped the seller make out. I found out later the purchaser buys $4,000 trumpets and such. I got these for considerably less albeit with a few issues that I'm hoping are fixable.

I know they're better, but really, how much better are the 1.2Tls over the original SDA SRS? Before this my speakers were Infinity SM152s and there's a considerable difference between them and the Polks. Call me a neophyte, but I had to ask the question!

DarqueKnight · May 2003

I took a look inside my SRSs. The crossover of each speaker is identical. The only difference between the left and right speakers is the mirror image orientation of the stereo and SDA drivers and the wiring connections of the SDA cable jack.

The left speaker has the green wire connected to the top slot of the SDA jack and the blue wire is connected to the bottom slot.

The right speaker has the blue wire connected to the top slot of the SDA jack and the green wire is connected to the bottom slot.

From what you have told us, it might be that one of the previous owners played around with the internal wiring a bit. If the drivers were blown and had to be replaced, some crossover components might have been damaged also.

DarqueKnight · May 2003

.

DarqueKnight · May 2003

I have been trying to attach a file to this post but it wont let me.:supermad:

DarqueKnight · May 2003

Originally posted by jtconnell
I know they're better, but really, how much better are the 1.2Tls over the original SDA SRS

It depends on what you like. The TL version has flatter, more accurate frequency response in the treble region. The SRS is a little brighter sounding than the TL version. The SL 2000 tweeter of the SRS had a tweeter resonance at 14,000 Hz. The SL 3000 tweeter of the TL version corrected that frequency response anomaly.

I use the SDA 1.2TLs in my two channel audio rig. I use the SRSs in my home theater.

Tour2ma · May 2003

Jt,
First off just tweaking your bill with the Pittsburgh comment. But since when do they use whilst in Indiana??? A little UK in your background I suspect

Reread one of your early posts after reading hars question about your amps design.

Originally posted by jtconnell
When I converted the left speaker to a right speaker, I also changed the positioning of the drivers and their associated wires. In other words the blue/green wires that powered the SDA effect and the Blue/White wires that powered the Stereo Effect were reversed in the cabinet. I did nothing with those wires on the crossover. Before I did the modifiaction, the amp would shut down before it got too loud with the interconnect cable connected. I figured this was due to the interconnect cable not being properly wired. Changing that solved that issue. They now play loudly, but I only get the SDA effect from the modified right speaker.

It sounds to me like you had an amp issue, and then undid it during the mod by somehow undoing the SDA effect from the one speaker. If you re-establish the missing SDA, you may bring back the amp problem.

A couple members have reported issues with various SDAs and Yammie amps. Seems a fair number of their amps are not common ground design, so the SDA circuitry creates a short in their output. Heres a link to one thread http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=9261

And do call Ken, or Lauren, theyll get to your e-mail, but a phone call will get their attention more quickly.

Also heres a great old thread by raife on the SRS lineage http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=7139&highlight=history it should give you a grin or two in the midst of your struggle

DarqueKnight · May 2003

JT,

I tried to attach a picture of my SRS crossover wiring diagram in the form of a downloadable file, but the system won't let me. Maybe they are out of memory space.

I will email it to you if you like.

jtconnell · May 2003

Please do! jconnell@wabtec.com

Thanks for your help! Any ideas about the "doughnuts"?

DarqueKnight · May 2003

I just sent the wiring diagram.

I spoke on the doughnuts in an earlier post. Scroll back a bit.

jtconnell · May 2003

I got the file - thanks! If I recall correctly, my interconnect cable is black and green rather than blue and green but I'll check it out.

With respect to doughnuts, please scroll up and see my answer to your post. I'm talking about the cardboard surround that covers the seam between where the rubber speaker surround joins the metal speaker frame. I have one speaker with them and one without them.

Thanks again for the drawing!

DarqueKnight · May 2003

None of my SRS drivers have the cardboard doughnut. In fact, none of my SDA speakers have this type of driver. All of mine have the rubber surround bonded directly to the metal frame.

I have no idea why this bonding arrangement would be used....unless this is a driver that had been repaired this way.

Ken Swauger in Polk Customer Service might be able to provide some information on this. His email is KSwauger@polkaudio.com.

jtconnell · May 2003

Thanks for the input! As I said before, they're all 6503s which as near as I can tell is the original equipment for the SDA SRS. It's just that the ones in one speaker has 'em and the other one doesn't. They were all built in July of 1991. Probably some previous owner modification.

jtconnell · May 2003

Well, I finally got to the bottom of it thanks to a whole lot of support and a wiring diagram from Raife! Basically the issue was this:

On the "genuine" left speaker the green interconnect cable was done properly (marked "G" on the Xover). The black wire next to it in the L2 connection (I think it should have been a blue wire, but my Xover is marked "B" only unlike Raife's which was marked "Bu'") was connected to the ground on the low frequency input. WRONG! WRONG! WRONG!

The black wire next to it (which was labeled 'L1') was connected to the interconnect socket. Again wrong! Even though the schematic shows that the two are interconnected, I switched the wires and now everything seems to be working great! The SDA drivers function when I change the balance and the stereo drivers seem to do what they're supposed to do as well. Now all I need is a single SL2000 tweeter and I'm all set! Any suggestions? I'd prefer not to have replace all eight if I don't have to.

During testing however, the drivers on the modified right channel still seem to have more excursion than the ones on the left. Not sure about this one - I'll spend some time rechecking connections. So now that I finally have a working pair of "stock" speakers, are there any easy ways to improve them, or should I just be happy with what I've got? (believe me I am regardless) Thanks for the help everybody!

Original SDA SRS Help Needed!

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