SDA 1A What to do now?

FireGuruMN

I landed a pair of SDA 1A speakers in pretty nice shape. All the drivers seem to be in good shape and they sound fairly good. But I don't think they are everything they should be. The speakers sound very "bright". The bass seems to disappear in the room somehow. I had the same problem with bass on a pair of Boston Acoustic A400's (forgive me for saying that on a Polk forum) until I angled them sideways about 20 degrees. But the SDA's loose their separation when angle them.

Here is a picture of the crossover. I pulled the tweeters and they are SL2000's even though the manual that came with them says SL1000's. I have not pulled the other drivers to see what they are.



I am powering them with a Sony STR-DA777ES and have tried a Sansui AU-X1 also. Not much difference. (forgive me Sansui lovers)

I see all sorts of posts about replacing capacitors, removing polyfuses, changing to RDA tweeters, replacing fabric but what is going to give me the best speakers? None of the posts seem to quite match my setup. And I don't recall anyone talking about the 1000pf silver mica caps that I see on my crossovers. Do those get removed all the time?

I am comparing them to RTI-A9's with PSW110 subs and hoping that "old school" sounds just as good.

mlistens03

Redo caps, and RD0-194s (if that’s the correct tweeter, I think it is, if not get the RD0-198). That should solve your brightness problem and help with your low end problem, although I think that your low end problem will be fixed by slightly adjusting room placement. When you get them working perfectly, they will probably (based on others experiences) be your favorite speakers. I’ve never heard any of the classic Polks, but most say that they are awesome, especially the SDA speakers.
P. S. If anyone else says different, I defer to them, because they are almost assuredly more knowledgeable on these speakers.
P. P. S. No big deal on mentioning another brand of speakers, there are many threads on here not even involving Polk.
Micah

F1nut

Those are not one of the better SDA speakers and I wouldn't put a dime into them, but your choices for power are all wrong. So, right now you can't blame the speakers for their poor performance.

Your Sony AVR is not rated to drive 4 ohm loads, which the 1A's are and which dip lower. I'd highly recommend not using it with the SDA's.

The Sansui, which is rated to drive 4 ohm loads is also dual mono and more than likely non-common ground. Do not use it with those SDA's.

tonyb

Aside from that ^^^, comparing them to A9's is far off base.

I see nothing wrong that sticks out on those crossovers. Sda's are not meant to be toed in either. I'd keep the A9'S and get some better amplification. The Sony on it's own is a non starter and the Sansui, while decent, the 9's still need more current.

pitdogg2

the SDA1 came with both the SL1000 and the SL2000 tweeters. there is actually 5 generations of the SDA1. SDA1, SDA 1 signature, SDA1a, SDA1b and SDA1c.

I have a set of SDA1 Signatures I went and did the XO with all Sonicaps it did make a heck of a difference but it is pricey. Mine had the best bass 4" off the back wall and spiked to the floor. I'll agree they're better SDA's to have and upgrade, but in some areas they are few and far between. You need to make sure they are air tight. If there is air leaks it will affect bass response negatively. I would also check all the drivers to make sure no one has put a different driver in the speaker. They should be all MW6501 or early models had MW6600.

To check to see how air tight they are push in on the passive radiator quickly until it stops and count how long the mid-woofers take to go back to a rest position. Mine with all MW6600 take 5-6 seconds if your's have all MW6501 it will be 3-4 seconds. The difference is the MW6600 had a felt dust cap and they held air longer.

FireGuruMN

I love a forum that has such quick replies and strong opinions!
I did the test with pushing in the passive radiator already. The drivers are still off their rest position after 30 seconds. I think the speakers are airtight based on that test.
Both the Sony DA777 is rated at 100watts into 4 ohms and has no problem powering the A400's which are also 4 ohm speakers. It's not a run-of-the-mill Sony. The AU-X1 is rated at 220watts for 4 ohms. Do I really need more power than that or is there some other specification I should be looking for? I have other amplifiers I can hook up.
I am thinking that my problem is probably room placement. I will move them out to the big room and give them a try.
I'm going to be recapping my A400's and I thought I would do the SDA's on the same order. My concern was whether I should be replacing/removing/leaving those mica caps in the circuit? It's not clicking in my head what purpose they serve and I don't see them on other SDA crossovers.
Does anyone want to throw out a parts list for caps and resistors?

FireGuruMN

Oh yes, I don't think AU-X1 is quite a dual mono amp because it shares a power common transformer between both channels. I measured the resistance between the speaker grounds and it is zero ohms. I really did not want to blow that amp up (again!).

F1nut

Sorry, the info I found only listed an 8 ohm spec for the Sony.

Power isn’t the issue with the Sansui, it's the possibility that it is a non-common ground amp, which is a no-no with your model speaker.

The silver mica is a bypass cap and should be removed when upgrading to film/foil caps.

pitdogg2

They like power period end of discussion

They start at 4 ohms and dip lower which can be hard on a receiver.

The RDO194 would be the correct tweeter.
Have you disconnected the dimensional tweeter? Most do so if you choose to get tweeters you only need 2

All the parts list you need is on the crossover. Most here use Vashay-Mills resistors. As F1nut said the silver-mica are no longer needed with better film caps. You need to get the values off the caps on yours. Looking at your tweeter circuit they also used a mica cap across the 5.8uf mylar cap and resistor combo there. Mine did not have the mica there no biggie but there may be other changes there. If you go to the vintage speaker section there should be a SDA1a schematic there to compare to yours.

FireGuruMN

AAAAHHH! I moved them out to the "big" room and connected them to a Pioneer SC-57. That sounds much better. All the bass I would expect is back. Probably more from the room than the amp change. I can flip between the RTIA9's in that room also. The SDA's certainly hold their own against the A9's but the SDA's are showing their age I suspect. Now I would say the SDA's are lacking midrange. It's always something. But like everyone always says, "Sound in the ears of the beholder". There is certainly nothing annoying about the SDA sound.

I opened up the other SDA to look at the crossover and it appears that someone has been in there making some repairs (or worse). So I think I am off to the capacitor store. Those Sonicaps are expensive! Are there other reasonable choices out there?

Schurkey

ANY film cap is going to be better than the electrolytics they replace. Even the stock Mylar HF capacitor is bettered by "cheap" modern film caps.

My SDAs have a combination of Dayton 1%, Dayton 5%, and ERSE 3% caps.