SDA SRS 2.3TL Schematic vs. earlier 2.3

SciFiTom

Folks, first-timer, here. I recently acquired a pair of SDA SRS 2.3 speakers. One was slightly damaged when I got it, and the idea of ancient electrolytics is scary, so I'd like to update the tweeters to RDO-198's and the TL XO schematic. I was thinking I'd leave the bottom end alone, other than to re-cap it, so as not to have to replace ALL the drivers, and the XO, too.

However, the schematic I acquired from Darque_Knight's "book" seems to be quite different between the two versions, to the extent that the tweeter phasing is reversed, as well as different tweeters connected to a given circuit element.

Not to offend anyone, but how trustworthy are these schematics, may I ask?

F1nut

The schematics are spot on. The two speaker models are so different that trying to make the TL version from the non-TL version is not practical in the lest.

Mike Reeter

^^^^ All true ^^^^ I would upgrade all the caps and resistors, install RDO-194 Tweeters, binding posts and several of the other mods that can be done to your 2.3's and enjoy them, they are a very good model of the SDA lineup.

heartystatue

Hey SciFiTom, Welcome to CP! What F1 and Mike Reeter say are spot on. The non TL version of the 2.3 is completely different from the TL version even the driver banks are switched. I have the non TL version and have upgraded everything on them. I had a fellow Polkie here build new crossovers for them as a lot of other's here have done. Check out VR3 mods website. Trey has a lot of experience as well as others here and can get you where and what you need. I can also say adding spikes to the bottom, adding Larry's Rings, and resealing the inside of the cabinet with Loctite Power Grab is a cheap upgrade. Also you have to use a common ground amplifier with these. If your amp is not common ground you will have to build a Dreadnought. Get your read on. There is plenty of info on the forum on all these upgrades. Again welcome to CP.

drumminman

Welcome to CP SciFiTom.

Lots of knowledgeable folks here on the forum, several of whom have responded in this thread. Good luck with your rebuild.

SciFiTom

Gentlemen,

I am impressed by the rapid, and cogent, responses, given the age of these speakers. Thanks for that, and the welcome messages.

As usual, no doubt, there are a number of issues beneath the surface. I moved from Magnepan 3.6s to the Polks, because I just couldn't get the bass to work in my room with vaulted ceilings going the wrong way, and other impediments. I do miss the clarity, though, especially since I'm an old guy with tinitus, and generally poor hearing compared to my youth (someone beat me to the user name of "hearingimpaired" [grin]). I have read many of the posts on this subject, so have learned about VR3, Larry's rings, various damping treatments, et numerous al. The rings seem almost a necessity for mechanical reasons, given how often some of you guys seem to take your speakers apart, but I thought I'd wait a bit on that.

I was taken with the notion that the 198 tweeters are supposed to have a flatter response curve. I may very well hate it, but I intend to try the TL tweeter approach (since I have already got the parts) at least on one side. I still have some vector board left over from the days when I did more electronic projects, so I'll build the tweeter section on that, and leave the original XO alone. That'll make it easy to reverse the change if I can't make it work. So, I'll rewire the output connector to match the older version. Likely, you folks are correct, and I'll RUN for the 194s, but it seemed an interesting experiment, and not terribly expensive as audio goes. I will add damping material to the baskets while I'm at it, which is rumored to exacerbate tweeter brightness. I did add a bit of "R" to the front end of the XO, and if it just needs attenuation, that's easy enough (bet that won't do it - particularly as heartystatue reminds me that the driver banks are swapped, and I did notice comments about added internal bracing).

It's a science experiment at this stage, and won't be a big problem to head the right direction. I've not heard about the Loctite reseal, though, perhaps someone could provide a link, or more data on that point?

Thanks again for the comments,
Tom

SciFiTom

Oops, forgot to mention that I looked at this forum some before I bought the speakers. My amp is bridgeable, and the commons measure effectively zero ohms DC between the posts. I seem to be fine on the common-ground front. Thanks for the warning.

Schurkey

SciFiTom wrote: »

Oops, forgot to mention that I looked at this forum some before I bought the speakers. My amp is bridgeable, and the commons measure effectively zero ohms DC between the posts. I seem to be fine on the common-ground front. Thanks for the warning.

But are you USING the amp(s) in it's "bridged" mode?

If so, you MUST have the isolation transformer in the SDA interconnect, or leave the cable disconnected.

chandler9a

I have to second what others have said about keeping them non-TL. You are going to have to buy new drivers, redo wiring, and if it doesn't work, it will not be cheap to reverse.

Both are great speakers, a modded pair of regular 2.3's is going to sound amazing, it just isn't worth trying to TL them IMO.

Mike Reeter

chandler9a wrote: »

I have to second what others have said about keeping them non-TL. You are going to have to buy new drivers, redo wiring, and if it doesn't work, it will not be cheap to reverse.

Both are great speakers, a modded pair of regular 2.3's is going to sound amazing, it just isn't worth trying to TL them IMO.

Very true, Replacing eight of the mid-drivers is not an inexpensive adventure, when coupled with the price of six new tweeters.

DarqueKnight

SciFiTom wrote: »

I moved from Magnepan 3.6s to the Polks, because I just couldn't get the bass to work in my room with vaulted ceilings going the wrong way, and other impediments. I do miss the clarity, though, especially since I'm an old guy with tinitus, and generally poor hearing compared to my youth.

Larry's rings significantly improve clarity. After installing rings, the clarity of my SDA 1.2TL's exceeded that of my Magnepan MG12s, whereas prior to the rings, the clarity of the Magnepans was better.

heartystatue

The power grab is avail at Home Depot for about 4.00. No silicone, dries clear, easy clean up. I used my fingers quite a bit in the tight spots. Again, cheap and easy. I used the caulking gun size. 1 tube did both.

Toolfan66

There is no reason to venture into tl'ing these speakers..

The 2.3's are fantastic just the way they are, do the upgrades and be very happy with them. I have been fortunate to hear the 2.3's and 2.3tl's side by side, and both kick **** IMO..

I think the TL version's get too much hype that the other models get over looked at being a great speaker, NEWS FLASH the 1.2's/2.3's/Original SRS's, and CRS+'s,and the 2B's with out being tl'ed are a GREAT Speaker standing by them selfs...

Just my honest opinion, with that said, when one is going to upgrade the CRS+'s/2B's, and the 1.2's one might as well TL them as the cost is minimal since most will upgrade to the RDO's anyway..

With the 2.3's it's just not worth the time and money. Upgrade the xovers, and tweeters to the RDO-194's and be happy!! You can add the smaller tweaks later if you want..

SciFiTom

Hmm. A number of folks recommending against the 198s. I don't want to alienate anyone, but since we had snow days here last week, I've ordered and received the parts, and I still have some old Vectorboard equivalent from earlier times when I did more electronics projects. Having not seen any posts of someone having the same hair-brained scheme (did I miss some horrible experience?), I'm inclined to perform the experiment (and then likely RUN for the 194s). My room situation is really odd though, and stuff you wouldn't expect to work sound good to me (remember the bad ears, too). If 180 degree phasing or tweeter AMPLITUDE problems occur, that could easily be rectified outside the cabinets by swapping the leads, and/or adding some "R". Hey, at least I'm not talking about replacing the PRs with woofers, and if I build the tweeter XO separately, it should be very easy to return the speakers to stock, and/or head for the 194s. I would be inclined to change the 2.3tl XO connector wiring to agree with the earlier version, so the tweeter connector would plug in either board without modification.

Thanks for the comparison to the MG-12, DarqueKnight, and sorry about the added underscore the last time I mentioned your "name." I'd be pleased to be able to obtain a set of Larry's rings, especially if I need to pull the drivers out more than once. However, I have the impression that they are not currently available.

I imagine that tightening torque may play a role in the varied responses in posts referring to this mechanical solution. It looks like they incorporate PEM studs pressed into the rings. If so, I would think one could obtain data to support a reasonable torque value that might alleviate the differences there, though the various Moretite, and foams used would be an influence. Presumably, on the 2.3s, the lack of access via a XO plate means some interesting contortions to install the rings for the upper drivers, or is there a trick? Does anyone know if I'd encounter bracing that needs to be modified, or that would prevent access? I expect one must cut the ring for the PR to install it? I'd think a pair of cuts near adjacent studs generating a gap in the ring would be the best answer. That way, the geometry wouldn't be disturbed, and reduce the likelihood of rattles.

Failing that, I've gotten the impression that the use of Armacell tape has a similar effect to the use of the rings, as long as the screw holes haven't been stripped. I would prefer the rings, as there is then no dependence on the particle board baffle, I'd think. Out here in western Oregon, humidity changes are a fact of life, and can't be a good thing for the stability of the board.

SciFiTom

I seem to have lost a posting. [Gee, and this helps get my meager count up too!] In it, I responded to Schurkey with thanks, and said not to worry about the amp. I'm using it in normal stereo mode, so the ground is common. Should I need it, I have the stock isolation transformer for temporary use.

Presumably ToolFan66 (of ring fame?) with the Wyred4Sound amp needs an isolation transformer? I have been interested in that series, but it looks like the B&O bricks, or some such, which I would not expect to have a common ground.

Heartystatue, are you applying the Power Grab to the interior corners or cuts, to assure an airtight seal, or am I missing something? I should think that, barring damage, the dust covers of all those drivers would allow more air movement than small cracks. I'll look at the datasheet for the Power Grab.

Thanks yet again, all,
Tom

F1nut

One issue with using the RD0198-1's and the appropriate circuit is that it will not be tuned to the 2.3 bottom end.

I imagine that tightening torque may play a role in the varied responses in posts referring to this mechanical solution. It looks like they incorporate PEM studs pressed into the rings. If so, I would think one could obtain data to support a reasonable torque value that might alleviate the differences there,

What varied responses? You torque the crap of them, period.

though the various Moretite, and foams used would be an influence.

I stand firm in my belief that if the stock gaskets are not damaged, there is no reason the replace them.

Presumably, on the 2.3s, the lack of access via a XO plate means some interesting contortions to install the rings for the upper drivers, or is there a trick?

You remove each driver and feed the rings up thru the now removed PR. It's easy.

Does anyone know if I'd encounter bracing that needs to be modified, or that would prevent access?

Each speaker bracing tends to be slightly different, so you may need to make adjustments.

I expect one must cut the ring for the PR to install it? I'd think a pair of cuts near adjacent studs generating a gap in the ring would be the best answer.

Do NOT cut the PR ring. There are 2 cuts already in the ring, just bend until it fits thru the hole.

I've gotten the impression that the use of Armacell tape has a similar effect to the use of the rings

NOT even close.

SciFiTom

Dear F1nut,

to take your responses in order (I've not figured out how folks attach parts of prior text so neatly):

Agreed, and understood. Clearly, I'm spitting in people's holy water. The voicing should be different, and I expect the balance will be off. Again, an experiment. I'm curious (perhaps in more ways than one), and it seems like a fun thing to try since I have already acquired the parts. If everything sounds like a beginning violin student, I'll know that I need to return to the path of righteousness (or get back up out of the rabbit hole - see Lewis Carrol), and there should be no harm done other than wasting my time, and money. Please believe that I am listening to what the folks who have taken their precious time to help me are all saying, and had I not already gotten the pieces, I would follow such overwhelming evidence without further ado. P.S. I believe I did see a post somewhere that suggested about 2uF in series worked to provide that balance. One man's opinion, phase shift notwithstanding. This is the internet, no guarantees.

I was referring to different posts I've seen with varying opinions on the effectiveness of Larry's rings when I suggested torquing them down to a particular value. I certainly see your point, but the next phrase about the different gasket materials that have been used was strictly intended to note that the needed torque would differ between the types of gasket employed, and the baffle coupling desired. In the case of foam, and such, the applied torque would vary over time as the material "settles."

I'm inclined to agree with you about not replacing the stock gaskets, with the possible exception of DarqueKnight's post about using Armacell tape to gasket the tweeters. I could imagine that resonant frequencies in the range of interest could exist on the tweeter housings, such that damping may be beneficial, a la the basket spiders.

On the 2.3s I have, the distance between the PR hole, and the top driver is well over two feet (slightly longer than my arm, while retaining control over the ring, I fear). Not insurmountable, just not ideal. Another case where two people would be preferred for the work.

I'm not too surprised that there may have been "continuous improvement" in play during the construction of these speakers, hence I asked about personal experiences regarding bracing v. rings. I take your meaning as, "see what you run into." OK.

Thank you very much for this information. I haven't seen other than pictures of the group of rings, so I didn't note that there was already a provision for getting the PR ring through the hole. Logical, and practical, presuming the ring isn't constructed of 1/4 inch steel plate. [grin]

Lastly, not too surprising that the tape and the rings do not provide equal effect. I bow to your greater experience.

Best Regards,
Tom

SciFiTom

SciFiTom wrote: »

(I've not figured out how folks attach parts of prior text so neatly):

Ah, perhaps I've figured this out...

F1nut

Tom,

By all means, have fun.

to take your responses in order (I've not figured out how folks attach parts of prior text so neatly):

At the top of the reply box, second from the right end. Click on that icon to quote.

P.S. I believe I did see a post somewhere that suggested about 2uF in series worked to provide that balance.

I believe you are referring to comments made by a complete whack job that is now banned from here. He had some silly noton that adding a 2uF cap would tame the 5dB spike in the SL2000 tweeter. It not only tamed it, it caused something like a 20dB drop. If you're referring to something else, I haven't seen it.

I certainly see your point, but the next phrase about the different gasket materials that have been used was strictly intended to note that the needed torque would differ between the types of gasket employed, and the baffle coupling desired. In the case of foam, and such, the applied torque would vary over time as the material "settles."

That's true. If one replaces the stock gaskets they will have to continue to torque the screws over a period of time.

I'm not too surprised that there may have been "continuous improvement" in play during the construction of these speakers, hence I asked about personal experiences regarding bracing v. rings. I take your meaning as, "see what you run into." OK.

No, that's not it. Let's just say that things were not always glued up in the same position from speaker to speaker.

F1nut

SciFiTom wrote: »

Ah, perhaps I've figured this out...

Or you can hit the "Reply With Quote" if you want to quote the entire post.

SciFiTom

F1nut wrote: »

Or you can hit the "Reply With Quote" if you want to quote the entire post.

Yes Sir,

I finally noticed that (I don't do many forums).

Thanks.

F1nut

SciFiTom wrote: »

Yes Sir,

I finally noticed that (I don't do many forums).

Thanks.

There's folks that have been here for years that still haven't figured out how to work the quote feature. You catch on quick.

SciFiTom

Hi F1nut,
Mars must have a peculiar time reference. It's pretty late where I am. If you're much further East, your schedule is worse than mine.

F1nut wrote: »

By all means, have fun.

The various comments have caused me to notice that I mis-read some of the values between the schematics. I ought to look further in to the tweeter characteristics, and re-evaluate my position. Of course, I do still have those parts...

F1nut wrote: »

At the top of the reply box, second from the right end. Click on that icon to quote.

Let's see whether I've got the hang of the XML-like syntax. I'm just typing the codes in. I see the Reply with quote button, but the other one you refer to continues to escape my attention. Hmm. Given the schematic dyslexia, maybe I just need new glasses.

F1nut wrote: »

I believe you are referring to comments made by a complete whack job that is now banned from here. He had some silly noton that adding a 2uF cap would tame the 5dB spike in the SL2000 tweeter. It not only tamed it, it caused something like a 20dB drop. If you're referring to something else, I haven't seen it.

Yes. I re-read that post, and agree with you wholeheartedly. Just the series impedance is 8 ohms at 10kHz.

F1nut wrote: »

No, that's not it. Let's just say that things were not always glued up in the same position from speaker to speaker.

I was being kind to Polk. After all, it is their forum. Sorry, my dry sense of humor doesn't always translate to electrons.

I very much appreciate your patience, and good heart,
Tom

F1nut

Yes, the sun will be rising soon....time to crawl into my coffin.

Good to have you here. :cool:

PolkieMan

Tom I am waiting with much interest to see how your 2.3 "TL-ed" project unfolds, welcome sir!

TennMan

SciFiTom wrote: »

... On the 2.3s I have, the distance between the PR hole, and the top driver is well over two feet (slightly longer than my arm, while retaining control over the ring, I fear). Not insurmountable, just not ideal. Another case where two people would be preferred for the work...

Best Regards,
Tom

Tom, Welcome to the Club Polk!

I haven't saw the inside of the 2.3s but wouldn't it be possible to remove all the drivers and PR, put a ring for the MW through the PR hole and move it to the top position by reaching your hands through each MW hole and maneuvering the ring to the top? Repeat that process as you go down each column until you get to the bottom drivers which can be easily reached from the PR hole.

No need to grow longer arms just to install a set of Larry's rings.

cincycat13

Tom...welcome to the forum!

I will post a link to my 2.3 XO mod at the bottom of the reply. I studied doing exactly what you are trying when I did mine as it wasn't going to cost that much more to just change the tweeter section, or tweeter and mids. I got the same type of information you are getting and did not bother. I know simpler can be better in audio...but when you compare the 2.3 to the 2.3TL on paper, the 2.3 is more complex and harder to manufacture.

For example, you have to inventory 3 mid drivers for the 2.3 and install them in specific positions where the 2.3TL has only one part that goes in all positions. I have never heard the TL version so it could be an evolution in sound improvement. On paper it looks like an accountant streamlined the manufacturing process. I do have the RDO-198 in some RTA-15TL, but my ears and set up are not fine enough to hear the subtle differences.

I look forward to following your testing. It looks like almost 3 years have flown by since I reworked mine, and have not second guessed the path I took.

http://www.polkaudio.com/forums/showthread.php?118701-gimpod-SDA-boards-for-2.3

heartystatue

SciFiTom wrote: »

I seem to have lost a posting. [Gee, and this helps get my meager count up too!] In it, I responded to Schurkey with thanks, and said not to worry about the amp. I'm using it in normal stereo mode, so the ground is common. Should I need it, I have the stock isolation transformer for temporary use.

Presumably ToolFan66 (of ring fame?) with the Wyred4Sound amp needs an isolation transformer? I have been interested in that series, but it looks like the B&O bricks, or some such, which I would not expect to have a common ground.

Heartystatue, are you applying the Power Grab to the interior corners or cuts, to assure an airtight seal, or am I missing something? I should think that, barring damage, the dust covers of all those drivers would allow more air movement than small cracks. I'll look at the datasheet for the Power Grab.

Thanks yet again, all,
Tom

Hey Tom, You are correct I used it to reseal the complete inside cabinet and the crossbraces. Took me about half an hour for each speak.

leftwinger57

As many here will tell you I originally DID NOT want to get into mods at all. The set of speakers I got sounded great to begin with and the only thing wrong with them was cosmetic. So for $50 and the cable included I just had to buy them and was the sale of 2013. With F-1s hepl I now have beautifully bleached and stained walnut tops. Now if these guys say and do not do the TL mod I would listen, these guys have more knowledge of vintage SDA than the present day engineers at Polk. I was a true skeptic and after doing 1 mod at a time with positive results I was onto something here to be heard. I would not hesitate to ask for hepl or adsvice and oncew given if ignored or done in a way that does not fit the spec then you get hammered on , mostly desevedly so. Great score beautiful speakers and it does seem to be SDA picking season with all versions showing up all over. Good luck w/ your project ....Lew

SciFiTom

TennMan wrote: »

No need to grow longer arms just to install a set of Larry's rings.

Sigh, some days I'm just stupid. Thanks for the tip.
Now all I need is for "Larry" to pass through here to say, "Here's how you get them."

Toolfan66

I'm trying to get the time to run some more rings, I have the passives, I just don't have any driver rings or tweeter brackets..

I'm going to echo what I said earlier, leave them as 2.3's, don't try and make them a TL version. If you do try and do it remember your left speaker will become your right speaker, and your right speaker becomes your left speaker...

I'm telling you the 2.3's are awesome speakers, no need to go down that road..