SDA2 Mod Advice Needed

Marty913

After reading about all of the MODS and how improved the sound is (its pretty damn good without changes), you have me thinking about it. I need some advice.

I have SDA2’s but they are “crossovers” in that they have 2-mids+1-dimensional and 2-SL2000 per side. The drivers all appear to be in great shape, and I’m not sure I would initially swap them out. The speakers sound fine and replacing 10 drivers would be expensive.

The crossover(s) on the other hand were bounced around during shipping, and of course they represent almost 22-year-old technology. Unfortunately, I haven’t soldered anything in years so that may be a challenge (re: DISASTER probably). So, in your collective opinion:

Would it be worthwhile (sonics perspective) to do the four crossovers and leave the drivers as is for now? Secondly, if I didn’t feel comfortable tackling it myself, has anyone “farmed out” that part of the job or are all of you comfortable with a Weller? If I were to blow it it’s not like 22 year-old SDA crossovers are laying around the local Shack. Northwest Florida (the Panhandle) is not exactly flush with Audio/Video specialty stores or electronic repair shops. Now if I needed a stump pulled or a deer stuffed that would be different. :eek:

Any and all advice, opinions, and criticisms are welcome.

F1nut

IMO, you don't need to change out the drivers unless there is something wrong with one or more of them. However, the replacement tweeters are a vast improvement over the SL2000's and would be a good place to start. The crossover upgrades can take the speakers to a new level and is definitely worth consideration.

Joe08867

^^^^What F1 Said^^^^

I have the same series SDA2 and the tweeters are a big help.

mpsantos

Hi, I have been poking around a bit and I am interested in checking out the Crossover mods. Where can I find this info?

Thanks in advance!

nms

mpsantos wrote: »

Hi, I have been poking around a bit and I am interested in checking out the Crossover mods. Where can I find this info?

Thanks in advance!

search for "crossover" or something along those lines. You can change the "search entire posts" option to just titles to help narrow search results.

Ricardo

If soldering is your only concern, take a look at some of these videos, and practice a bit before you do the real thing. It's not complicated at all.

http://www.tangentsoft.net/elec/movies/

mpsantos

Thanks for the reply. I have looked for several hours and find some posts that say to just replace the existing components with better quality caps, tighter tolerance resistors, new binding posts, etc. If I am not reading something wrong, there were some value changes that gave better sound quality from these speakers. I have the SDA 2, not A or B series, just the original ones with the 5 drivers and passive radiator per speaker. I haven't used mine in a really long time and I am looking to really freshen these things up. Any suggestions from anybody that has done it would be greatly appreciated!

mpsantos

One thing I forgot to mention was that the compendium I guess is out of print and this would help me with these upgrades. Anybody have a copy they care to sell?

ben62670

I disconnected the dimensional tweeters to improve the sound. The first generation used the dimensional tweeters, but the next 4 generations did not. I feel the sound stage is to wild with the dimensional tweeters. If you do disconnect the dimensional tweeter, and experience a lack of mids, and highs then you can change the 3.5ohm resistor for a 2.5, or 2.7ohm resistor. I did this mod on mine, and it improved the SQ tremendously. If you do use the silk dome replacement (RDO), and the mod you will almost surely want to decrease the resistor to 2.5ohms as they are ever so slightly less efficient than the SL2000's. I have had about 8 SL2000's altogether, and when the SL's are in good shape they sound very nice, but I have only had 2 that handled the time well. The rest were harsh.

mpsantos

Thanks again for the reply! I may just try the RDOs since I need a replacement tweeter anyway. Would you suggest replacing all the caps and resistors since they are so old? BTW, I have no problem with electrical work like this.

Marty913

ben62670 wrote: »

I disconnected the dimensional tweeters to improve the sound. The first generation used the dimensional tweeters, but the next 4 generations did not. I feel the sound stage is to wild with the dimensional tweeters. If you do disconnect the dimensional tweeter, and experience a lack of mids, and highs then you can change the 3.5ohm resistor for a 2.5, or 2.7ohm resistor. I did this mod on mine, and it improved the SQ tremendously. If you do use the silk dome replacement (RDO), and the mod you will almost surely want to decrease the resistor to 2.5ohms as they are ever so slightly less efficient than the SL2000's. I have had about 8 SL2000's altogether, and when the SL's are in good shape they sound very nice, but I have only had 2 that handled the time well. The rest were harsh.

Ben62670, did you just unplug the dimensional tweeter and leave it disconnected? Any potential damage load-wise when doing this? (please don't tell me the notes will then just fall out the wire into the floor of the case :eek:).

Ricardo, that you for the soldering link. I may take a shot at it.

F1nut, I will order the tweeters as a start. It seems like a good start.

Thanks to all for the advice.

ben62670

Yes I would defintly replace all the caps, and resistors. Yes just disconnect the tweeter, and put some electrical tape over the wire.

Edit
I also taped the disconected wire to the (white) wire I left connected to the tweeter.

avguytx

Marty913 wrote: »

Secondly, if I didn’t feel comfortable tackling it myself, has anyone “farmed out” that part of the job or are all of you comfortable with a Weller?

I don't think anyone answered this part yet but if you can't find anyone, I would be glad to help you out with that. Of course, I'm in Texas so you would have to ship them here for me to do then I could ship them back. It would only take a few hours at most to do the job. Glad to help if need be.

schwarcw

Check out this thread Here

I didn't disconnect my dimentional tweeter. I think the consensus (in my opinion) and some others is to eliminate the 750 pF by-pass capacitor. It's just not needed, and may make the high end a little harsh.

The best advice that many others have posted is to replace the tweeters with the new RDO-194 soft dome or so called silk tweeters. It will make you believe that you have a new pair of speakers.

Good luck!

ben62670

schwarcw wrote: »

Check out this thread Here

I didn't disconnect my dimentional tweeter. I think the consensus (in my opinion) and some others is to eliminate the 750 pF by-pass capacitor. It's just not needed, and may make the high end a little harsh.

The best advice that many others have posted is to replace the tweeters with the new RDO-194 soft dome or so called silk tweeters. It will make you believe that you have a new pair of speakers.

Good luck!

I agree with omitting the bypass cap (750pf) as stated:)

Marty913

avguytx wrote: »

I don't think anyone answered this part yet but if you can't find anyone, I would be glad to help you out with that. Of course, I'm in Texas so you would have to ship them here for me to do then I could ship them back. It would only take a few hours at most to do the job. Glad to help if need be.

I can't tell you how much I appreciate the offer. This forum, and the people in it are unbelievable. Unfortunately, I may need some help. I haven't had a lot of time to "get into" my SDA2's but did take some time last night and this morning. It appears the tweeters (non-dimensional) in both boxes are not working. The non-dimensional mid-woofers are. I unplugged the cable and confirmed this. The dimensional drivers are working when the cable is plugged in.

Any thoughts on how I might investigate further? Could it be the poly-switches. Seems implausible that both would go but then again very implausible that both tweeters would go out (I'll check them today but I'm pretty sure the actual tweeters are OK).

In short, I'm not sure how to proceed but I am determined to resurrect these things from the dead. They've obviously been abused and deserve a better life. I'm not sure me coming after them with a soldering iron in hand is a better life but it appears headed toward that - or perhaps avguytx coming after them.

F1nut

Your speakers do not have polyswitches. There is a fuse mounted on the binding post plate for tweeter protection.

So, everything works except the stereo tweeters, right?

avguytx

You can always take the tweeters out and hook them directly to the speaker wires that go into the speakers themselves and see if they have sound. Of course, do this at very low volume since there is no crossover on them at this point. What about a digital multi meter (DMM)? Do you have one of those?

Marty913

avguytx wrote: »

You can always take the tweeters out and hook them directly to the speaker wires that go into the speakers themselves and see if they have sound. Of course, do this at very low volume since there is no crossover on them at this point. What about a digital multi meter (DMM)? Do you have one of those?

F1nut, if you're talking about the external fuse(s) I have seen on some older Polks, I do not have them. Where else would I look, and what does a poly-switch look like.

avguytx, since the dimensional tweeters are working I will just swap that with the non-working regular tweeter. I suspect that will answer the question. By the way, here's a picture of the xover set-up.

ben62670

They have poly switches. Little blue ones.

Marty913

ben62670 wrote: »

They have poly switches. Little blue ones.

Thank you ben62670, I assume they are the really small ones (M&M size) at the top (in the picture). Well, it may not matter for now anyway.

I have swapped the dimensional tweeters for the regulars - and the regulars (former dimensional) now work as regulars. That would mean both regular tweeters went bad and the poly-switches did not. Wow. What does that mean .

Is it just a matter of time before the "now regular" tweeters fail? Makes me a little leery putting new tweeters in for a while OR re-doing the 4 crossovers first.

So far they appear fine albeit only a few minutes of music. I will use them several hours tonight at some realistic volume levels. I had planned on disconnecting the dimensional tweeters anyway and will do that now. No loss since they are now the blown ones.

Does anyone have any thoughts (conjecture) on how the two regular tweets might have gotten blown and the poly-switches did not. Could this have been just a coincidental case of two tweets wearing out over time? Any further thoughts on what you would do in this position would be appreciated.

Again, thanks to you all

ben62670

The dimensional tweeters seem to get less power than the stereo tweeters. The XO's are the same, but the SDA effect cancels out some of the power going to them. Also there is a bit of resistance from the IC cable going from one side to the other. I think it is about 1ohm.

Marty913

ben62670 wrote: »

The dimensional tweeters seem to get less power than the stereo tweeters. The XO's are the same, but the SDA effect cancels out some of the power going to them. Also there is a bit of resistance from the IC cable going from one side to the other. I think it is about 1ohm.

I do hope you're correct. Wearing out normally is definitely something I can live with. I guess it was very thoughtful of Mr. Polk to include a couple of "dimensional spares". I have disconnected the two blown ones. After an hour or so of listening, I must say the sound is great. Of course I'm not exactly sure what I'm comparing it to.

One thing that occurred to me (and this may deserve another thread) is that your recommendation to disconnect the dimensional tweeter appears so far to have little or no detrimental impact on the sound. Given that, what would be the value (if any) of using the former dimensional tweeter as a 2nd full time tweeter. Would that be a MOD worth exploring. Any thoughts.

ben62670

Marty913 wrote: »

I do hope you're correct. Wearing out normally is definitely something I can live with. I guess it was very thoughtful of Mr. Polk to include a couple of "dimensional spares". I have disconnected the two blown ones. After an hour or so of listening, I must say the sound is great. Of course I'm not exactly sure what I'm comparing it to.

One thing that occurred to me (and this may deserve another thread) is that your recommendation to disconnect the dimensional tweeter appears so far to have little or no detrimental impact on the sound. Given that, what would be the value (if any) of using the former dimensional tweeter as a 2nd full time tweeter. Would that be a MOD worth exploring. Any thoughts.

I would get 2 RDO tweeters first. Install them as the dimensionals. The reason I say this is the RDO's are slightly less efficient than the SL2000's. You may enjoy the sound stage of the dimensional tweeters. I personally don't like the dimensional tweets. High frequencies tend to bounce off surfaces enough on their own. I you do like the dimensional tweeters order 2 more. If you decide to stick with a single tweeter paint the domes of the burnt tweeters black:) Also try swapping out the resistor in line with the tweeter circuit. It should be a 3.5ohm. You can get either a 2.5ohm, or 2.7 ohm. Others may chime in disagreeing with this mod, but I have done it with very good results. The mids, and highs will be more pronounced. When I just disconnected my dimensional tweeeters it was kinda flat to me. There is a reason Polk did away with the dimensional tweeter. One other option if you decide to keep the dims you can change the dimensional tweeters resistor to 5.6ohms or so like a few of the older compact SDA's. This will help tame the wild spatial effect.