SDA1C Mods started

[vulcan]

Started some mods last weekend I been wanting to do. Plan on upgrading the crossovers, installing
the steel rings from Larry, Dynamat Extreme on the drivers and PR baskets, and upgrading the
tweeters to the newer RDO-194.
Sent the crossovers to VR3Mods/Trey to rebuild using Gimpods(Tony) custom boards, which are very nice
by the way. Trey uses some quality parts for these and has been great to deal with too.
Also called Helen at Polk Audio today and ordered the new tweeters. She was very nice, professional,
took care of my order in no time.
Expect to start installing the rings and Dynamat this weekend and will post some more updates later on that.
I thought these speakers sounded great before; after all these mods I fully expect to blown away after a little break in time.
When pulling out the drivers I noticed a few weird things I wanted to share and maybe
get your opinion about. Inside the Left Channel was large magic marker written "Bad Topseam", which I hope
was some problem found during production and corrected. Also, the Stereo drivers , one is a 6511 and one is a 6510. I had the schematic and both stereo drivers were supposed to be 6511. Maybe does'nt make any difference.
The Dimensional drivers are the correct 6510s. I verified all the wiring is correct per the SDA-1C schematics.
One MW6510 date stamped Jan 3 1992, kind of newer driver, replacement? I did not see any evidence of
repairs, everything looks original and no stripped screw holes. Oh yeah, some of the Polyfill had slipped down
behind the drivers, I assumed it was originally at the top. Last thing, I had not intended to replace the tweeters
until next year, but I read the SDA Handbook and saw where the resistance of the SL2000 Silver Coil was supposed to be at 7.5 ohms, all mine read 8.7-10 ohms. One of the plastic domes had a small split in it too. Glad I read that SDA Handbook, thanks Mr. Smith for a fine piece of work.
This will be my first speaker project. Been a fun project and looking forward to hearing these great vintage speakers sing again.
Thanks for looking and feel free to offer any input.
Craig

[nspindel]

Sounds to me like someone replaced one of the stereo drivers with the wrong model. Yes, there is a difference, although I'm not clear on what that difference is. Polk sells 6511's, call Helen back and order one. They're new production, not exactly identical to what they used to look like but they're 1:1 drop-in replacements for the old stock. I'd bite the bullet now and get your four new tweeters. You don't want to run Trey's fine-sounding crossovers on SL2000's, that just wouldn't be right. Not trying to spend your money, of course

Good for you, though! I used to own fully modded 1C's, you'll be very pleased. Are you doing anything with the binding posts? You might want to think about replacing the SDA connector with a binding post, that way you can easily use speaker cable for the SDA connection, or even better build yourself a Dreadnaught.

[vulcan]

Both speakers, left and right, the stereo speakers has one 6511 and one 6510, I am inclined to
think it was done during production. I did order the four new tweeters today, yes, I agree totally.
The binding posts and SDA connector upgrade will have to be done later, about run out of money for now...
thanks

[nspindel]

If one of the drivers has a 1992 datestamp, it doesn't sound like that happened during production. You can sell the two extra 6510's to help you pay for the replacement 6511's.

[F1nut]

Both speakers, left and right, the stereo speakers has one 6511 and one 6510, I am inclined to
think it was done during production.

Nope, Polk ceased production of 1C's in 1990. The specs for the 6511 and 6510 are very different, you need to replace the 6510's.

Oh yeah, some of the Polyfill had slipped down behind the drivers, I assumed it was originally at the top.

It's suppose to be behind the drivers, not at the top.

[vulcan]

Thanks guys, appreciate the suggestions. I guess I better start looking for some replacement 6511's

[rsxman]

this should yield some really impressive sonic changes and an overall brand new listening experience for you....i cant wait for you to report back when its all done and youve had time to listen to all the new work

[nspindel]

You can get 6511's from Polk. I use them in my 4.1 TL's.

[tophatjohnny]

Wow and wowed! I am no tech guy and wish I understood all that crossover stuff. That project is 5 levels above my pay grade. Congrats and I hope they sing like you want then to when done. I'm sure they will!

[drumminman]

If you want to sell the 6510's shoot me a pm.

[chandler9a]

fun stuff. looking forward to your impressions when its all done and broken in. I'm sure you are in good hands with VR3 doing the xover parts.

[Moose68Bash]

Vulcan,

You're embarking on a fun, interesting, and rewarding journey. I just finished "fully" mod'ing my SDA SRS1.2s, and on my 1Cs I'm ready to complete virtually the same mods that you are contemplating on your 1Cs -- I'm waiting for Trey to receive the correct inductors and finish the build of the crossover mods and binding post cup mods. Going to Vr3 Mods for the crossover work was a great choice IMO.

A few observations:
1. Your pictures show that your cabinets are much "cleaner" than mine were when I opened them for the first time in their lifetime. The excess glue in mine is extreme. But, perhaps, the more aesthetically "correct" application in your case led to the comment on the inside that there was a bad top seam. I didn't have any "leaky" seams, but I did have to clean up some excess hot glue before I could apply Black Hole 5 to the sides and back of the cabinets behind the MWs and tweeters. You may want to consider applying Black Hole 5 or NoRez (Trey's preference, I believe) while you have your 1Cs open.

2. The RD0194s are a dramatic improvement over the SL2000s. I received the RD0194s before Trey was ready to work on my 1Cs' crossovers, so I installed them before any other mods. They made a very big difference. My wife, who is brutally honest about opining on my stereo system "upgrades," remarked on the difference without my even asking her. She walked in, heard the music, and said, "Wow!" -- definitely a good start to a plunge down the upgrade rabbit hole! It went a long way toward establishing credibility for future work.

3. While my SDA SRSs were "under reconstruction," I used a Dreadnought amplifier interface for those speakers with my 1Cs. I didn't have to, because the amplifier driving the 1Cs is a common ground amp. Nevertheless, the Dreadnought made another palpable improvement in the sound that I noticed and my wife confirmed. The box was a plywood prototype that I made because I was designing an aluminum one to have fabricated before I heard that Larry fabricated and sold boxes. I don't yet have an aluminum box, but even the plywood enhanced the sonic character of the 1Cs. Picture follows, with the custom cables Trey fabricated for the Dreadnought:



4. Applying Dynamat Xtreme to the MWs and PRs can be tedious. Others have given good advice about how to do it more efficiently -- e.g., measure and cut the stuff for all applications before your start. I learned one thing that helped me: Small (1/4") dowel and a short (1.5" or less) length of 3/4" metal conduit or pipe can serve as an effective "rolling pin" to smooth the stuff out and remove air pockets. Somebody advised not to get to "anal" about it, but it is more satisfying to see a smoother surface IMHO.

Welcome to Polk Club. You've got a great pair of speakers, and I wish you the best in completing your mods. The members of this Club are incredibly generous with their advice an guidance, and they've done all the heavy lifting for us newbies, as you have already discovered with DarqueKnight's manual, etc. And my experience with Trey has not only been very successful in improving the sound of my SDA SRSs, but it has also been a real pleasure.

If you want to ask me any questions about what I ran into in getting my 1Cs ready to install Trey's mods and get them back to work, please don't hesitate to PM me. Here's a picture of mine "ready and waiting":



Regards, Phil

[brgman]

Nice speakers.
Please make a mental note that if you buy "new" model MW's from Polk the rubber may well overlap the screw holes.
You MUST trim these before installing or the screw will tear the rubber and you're screwed.
Good luck.You'll love them when you finish.

[vulcan]

Thanks everyone for your comments and thanks to the other Polk members who did their upgrades
and posted them with pics so I could learn how to do all this. Took me a while though to build up
the nerve to proceed with this(and some extra money helped). I did order two MW6511s from
Helen at Polk Audio today, so I should be getting those along with the new tweeters next week.
What did yall think of sound of the replacement 6511s?
I may consider the NoRez treatment, but need to find out more about it. Yes, and there seemed
to be a lot of glue inside the cabinets, drippin down in corners with some thick chunks, but none gets in the way.
One problem area installing the rings may be near the cross brace, but Larry sez they have been pretrimmed
a little for that, and he even includes the screws too, very cool.
Good Luck with your 1C project Phil, lets see some more pics.
Craig

[brgman]

I think Polk had stock in a glue factory.I have had some speaks with more glue than wood it seemed.Just the way they did it.
The 6511's sound fine compared to old ones.Just trim your rubbers!

[nspindel]

Be careful with the glue. The glue is what's keeping the cabinets airtight.

[Moose68Bash]

Good Luck with your 1C project Phil, lets see some more pics.
Craig

Craig,

Soon, I'm going to post the "story" of my life with Perreaux electronics and Polk Audio SDA speakers. I'll include pictures of the mod process on both sets of SDAs. Because you asked, here are some more pictures of work on the 1Cs.



The first few pictures deal with laying out and cutting, then installing Black Hole 5. I finally found a way to cut the stuff neatly -- not easy.

The next pictures show the polyfill (original) ready for reinstallation, the drivers and PRs Dynamatted and treated with JB Weld, and the new PR gasket I cut from 1/4" neoprene, using Larry's rings as templates.

[brgman]

I needed a longer rule when i cut mine also.
Why the hell didn't i think to steal a road sign?!
Nicely done.

[Moose68Bash]

I needed a longer rule when i cut mine also.
Why the hell didn't i think to steal a road sign?!
Nicely done.

Thanks, brgman -- I think!

I had a couple of steel fence posts sitting around, so I decided to clamp them down on the BH5, squeeze the beejeezes out of it, and cut it with the sharpest carpet knife I could find. Worked out well. I just wish I had discovered it earlier.

Also, thank you for advising me to use the 1/4" neoprene. It was difficult to cut, but clamping a sheet of it between Larry's drilling-template and ring made the job much easier and yielded a neat gasket. And, in the SRSs, it made for a great seal.

[vulcan]

Thanks for the pics! You did a great job with the Dynamat. I think I am going to use the
Black Hole material inside my cabinets too. I am putting the Dynamat on my drivers this
weekend, so your pics were a big help. The original speaker gaskets look to be in good shape
and am going to reuse those. Also thought about using the JBWeld but the magnets are all tight.
Good Luck with your project.

[pitdogg2]

Also thought about using the JBWeld but the magnets are all tight.

Do it anyway it's cheap insurance.

[brgman]

Do it anyway it's cheap insurance.

Agreed!
Once you get these all back together you are not going to have to open it back up because a magnet dropped off.

[vulcan]

I am convinced, I already bought the JB Weld so might as well use it. The way I crank these
speakers I need a little insurance. Any way to test or check drivers while they are pulled out,
was wondering what resistance would be. Also want to ask how much of that Black Hole
material to use in each 1C cabinet?
thanks guys!

[F1nut]

The way I crank these speakers I need a little insurance.

A magnet isn't going to come loose because you're cranking it. If and I say IF one should come loose it'll be because the driver itself or the entire cabinet received a hard blow, such as being dropped. That said, it's still a good idea to use the JB Weld.

[Mike Reeter]

Also want to ask how much of that Black Hole
material to use in each 1C cabinet?
thanks guys!

I covered almost the entire inter cabinet, too much, was killing the Bass. Removed all except for the upper back behind the tweeters and the mid-drivers, plus reinstalled the original Polyfill, no material in the PR area.

Much better. Everyones results may vary somewhat, in my case, less was more.

[drumminman]

I am convinced, I already bought the JB Weld so might as well use it. The way I crank these
speakers I need a little insurance. Any way to test or check drivers while they are pulled out,
was wondering what resistance would be. Also want to ask how much of that Black Hole
material to use in each 1C cabinet?
thanks guys!

For how much BH to use go here and see Post #1 ( about half way down) and Post #16: http://www.polkaudio.com/forums/show...lack+hole+TF66

[Moose68Bash]

Also want to ask how much of that Black Hole
material to use in each 1C cabinet?
thanks guys!

In my SRSs, after considering advice from drumminman and Toolfan66 (cited above), I put one 4"-wide x 24" long strip behind each row of MWs and one 2"-wide x 24" long strip on each side wall -- none going down into the PR area. I have been pleased with the results, albeit I cannot isolate the BH5 as the cause of any particular improvement in sound because I did many mods at once.

In my 1Cs, I decided to put less. I put one 3"-wide x 24" strip behind the MWs (starting at the top of the cabinet) and one 2"-wide x 24" long strip on each side wall -- again, starting at the top and not getting down into the PR area. I'm still waiting to reinstall the crossovers and binding post cups in these, so I cannot report on sonic effects. Once again, I'm implementing a number of mods at once and still won't be able to isolate any particular effect the BH5 has on sonic performance.

Which brings me to two observations:
1) I'm a bit lazy. If I had wanted to really evaluate what mods were responsible for what improvements, I would have done them one at a time, not all at once. However, the advice and experience of other Polkies convinced me that impatience and progress were more to my inclinations than trying to do things more "scientifically." I trusted them and didn't feel I would blaze any new trails, so to speak.
2) I decided to use Toolfan66's approach rather than drumminman's with the BH5, not for any substantive reason, but largely because I found it so onerous to deal with cutting BH5 that I felt "less is better" in this case. Now that I found a good technique for cutting it as I worked on the 1Cs, I might have taken a different course with the SRSs.

[vulcan]

Finally completed all the mods and enjoyed some extended listening time. Just to recap what was done;
Trey at VR3 Mods rebuilt the crossovers, I installed the Larry's steel rings, replaced the tweeters with new
RDO-194, used Dynamat extreme on the drivers and PR. JB weld on the drivers also. Placed the NoRez
foam in the back area. I also had to replace two of the stereo drivers because they were 6510, ordered
and installed new 6511 ea cabinet.
The sound improvements were phenomenal, like totally different speakers. First thing I noticed was the
sound stage was much larger, music very detailed. Also the bass is much better; tight, powerful and punchy,
like it should be. I never had good bass response with these before. The highs are smoother now with the new
tweeters installed. Very pleased with the results and well worth the time and money.
Would like to thank Helen at Polk Audio Customer Service for helping me order the new drivers. Polk Audio
has the best Customer Service of any company I have ever dealt with. Also a big thanks to Trey at
VR3 Mods for doing the crossover rebuild. He does quality work, easy to communicate with, and has a quick
turn around time too. Those crossovers just look fantastic! Next month Trey is going to do a binding post
upgrade with a NL2 interconnect cable for me.
Now I just need more free time to sit back and enjoy these great sounding speakers.
Thanks everyone for your help and advice on doing the upgrades, I really appreciate it.
I would also like to mention the amp I am using is a Carver M500t with a Mk2 upgrade,
really drives these SDA's well. Thanks again. Here is some more pics.

[pitdogg2]

I would also like to mention the amp I am using is a Carver M500t with a Mk2 upgrade,
really drives these SDA's well. Thanks again.

I didn't think that the Carver M-500t was common ground? Is it with the MK2 upgrade?

[tophatjohnny]

great pics of the job and still snooping "like a hound doggie" for as many pics of "adding the dynamat" to the speakers as I can see. I'll be doing this and the rings in a week or so, and would love it to go as perfect as possible. Great to have members here that are so helpful and willing to help each other. So cool , thanks Craig.