SDA2A - What does one note treble mean?

polk(2)a party

Hey guys, just picked up a bargain I couldn't resist on a pair of Polk SDA2A's. On initial listen, the mids and the passive radiator makes that little 6" woofer do amazing things. I did notice that the highs were uncomfortable though ..

The best way I can think to describe it, is "one-note highs", the way you talk about a lousy subwoofer having one-note lows. There's no dynamic there, and in percussion, even though it doesn't sound massivley wrong/distorted, it sort of hurts my ears the way someone clapping two blocks of wood together, and is very fatiguing after a very very short time.

Hopefully that description has you nodding your head instead of scratching it ..

If this sounds familiar, is this likely to be caps in need of replacement, or is this the characteristic of the SL 2000 that I have read about?

Also, I priced the poly caps in these things, and with the giant cans in the 2A, it looks like more than the speakers themselves are worth. I'm thinking of replacing with electrolytics instead - anyone had or heard of results of that?

gmcman

Could be a polyswitch that has gone bad or possibly a loose wire.

Other than that the best thing to do is pull the tweeters and check for loose wires. I believe the consensus is if you plan on keeping them then going with the RDO-194 is a prerequisite for better sound.

Along with a recap, but whatever the decision the upgrade is absolutely worth it.

polk(2)a party

Excellent, thanks, will get an order in with Helen for the RDO's this week.

Driving them with a Marantz 2238B, which probably also is due for a recap - I suppose the SDA's are a harder load than my bookshelves, so maybe that's something to look at too.

F1nut

polk(2)a party wrote: »

Driving them with a Marantz 2238B, which probably also is due for a recap - I suppose the SDA's are a harder load than my bookshelves, so maybe that's something to look at too.

48wpc @ 4ohms is not even close enough to properly drive those speakers. That and those SL2000 tweeters are nasty.

boston1450

I hooked my 2252b to my SDA2b's and at 10:30 on the dial it just down right started clipping & sounded like crap. I tried them on the Yamaha CR2040 & big difference being a receiver. Put a amp to them & bring them some power.. Welcome to CP

Schurkey

polk(2)a party wrote: »

Also, I priced the poly caps in these things, and with the giant cans in the 2A, it looks like more than the speakers themselves are worth. I'm thinking of replacing with electrolytics instead - anyone had or heard of results of that?

If I remember correctly, there's a pair of 130uF caps in each speaker, you'd need four altogether. Yes, that's going to be expensive if you buy film caps. Also huge! I needed four 91uF caps for my 1Bs, and I thought that was bad enough.

While I did buy film caps, you might want to consider ERSE electrolytics. They are NOT as wonderful as a film cap, but for an electrolytic, they're dirt cheap, and quite good. The tolerance is 5%, and the dissipation factor is great...for an electrolytic. They're not available in a 130uF version, but the 125uF should be close enough, and FAR better than what's in there now.

http://www.erseaudio.com/Products/NonPolarElectrolyticAll/ANP10A-05-125-0-PB

I needed a 120uF cap for each of my AR 93Q speakers, those are what I selected. (Haven't installed them yet.)

pitdogg2

yes you need an amp for sure they can abuse a receiver and you'll never hear what they are capable of. I did mine with Sonicaps and Axon caps for the 130uf must be creative to get it all to fit on the boards. They are well worth recapping and will just take your breath away AND GET SOME RDO194's in them.

polk(2)a party

Hey, thanks for the tip on ERSE, and thanks all for the recommendations - I have new electrolytics for all caps and a pair of RDO-194's.

After doing more reading I'm second guessing the electrolytics - maybe should have done polypro on the small values (it seems weird to replace a factory polyester (the 12uf yellow one) with a new electrolytic - could be a win or a loss..). I still think it's the way to go with the SDA circuit though, otherwise I might not get my money back out of them if I have to sell someday.

So I do have a question about the factory caps - I did not realize from first reading that the 12uf was polyester, until I dug deeper because its appearance. So I have to ask -

Are the original round caps really electrolytics too? They aren't film cap size, but they're in plastic cans and are bigger than new electrolytics

F1nut

One does not modify with the thought of getting their money back, it's done to imporove the sound for your enjoyment.

polk(2)a party

So that's what having money feels like?

westmassguy

I own 2As, which I've rebuilt, TL'd, and they're outstanding. You have to decide how much your willing to invest. Mine are well past the point of recouping even a third of what I've put into them.

polk(2)a party

DSkip wrote: »

Is this a flip project or something? You already spent the dough on new tweeters, which you'll take a loss on. Why not do the crossovers right since you're already in there?

It's not supposed to be a flip, but I live in an apt and have an unstable job. Even ignoring the broader economy, I can see myself in a situation where I need to part with these speakers, either because it turns out I just don't like the sound, they are too much speaker for neighbors, or because my life has gone to crap and I need to get rid of them so I can fit the rest of my stuff into a truck. It may be impolitic to consider such realities out loud, but IMO imprudent not to consider them.

I got one hell of a deal on the speakers from a guy who just wanted them out of his house, which is why I gave them a go - was hoping they would be "magic", but they weren't my taste. The RDO-194 is definitely less harsh, but they still don't sound sweet to me, which is why I'm stalling at the crossover. The phrase that comes to mind is "the highs are too reedy", but I'm not an audiophile, and have never done critical listening - so all I have is "I know what I like, and this isn't it".

Based on what I've read, cap problems would result in recessed highs, though, which seems it might be opposite my problem (Maybe I don't like the "Polk Sound"?).

I think I'll put the new electrolytics in on one, compare them side by side and if it seems like it has made a difference in (what I think is) the correct direction, I'll spring for the poly.

PolkieMan

Yea good question, what is your source? If it's 128k mp3 then that could be your problem. If the material is bad they will make it worse. How about placement? Did you check the drivers and the wiring to be correct. Did you refer to the SDA Handbook?

MrBuhl

At the risk of asking a really dumb question, you haven't mentioned the SDA cable, that did come with them and is hooked up right? That would definitely
account for an uninspiring listen? Sorry if I'm asking the obvious...

Schurkey

If it's like my crossover, the 12uf cap is the only cap in the entire unit that is in series. All the rest are in parallel. Therefore the 12uf is the single most audio-critical cap. It's the only one that Polk spent enough money on to get a film cap; bypassed with the silver-mica job.

Improved manufacturing has really reduced the size of electrolytic and other capacitors. I re-capped a pair of dbx 118s, even the ceramic disc caps are now 1/3 the size of the ones in there.

Check that receiver to see if it's truly common-ground. 20 ohms of resistance between the channels made my 1Bs unlistenable.

lbcgav

If I recall correctly, in the 2A, the large caps are in series. I spent a lot of money on those coke can caps in mine.

Schurkey wrote: »

If it's like my crossover, the 12uf cap is the only cap in the entire unit that is in series. All the rest are in parallel. Therefore the 12uf is the single most audio-critical cap. It's the only one that Polk spent enough money on to get a film cap; bypassed with the silver-mica job.

Improved manufacturing has really reduced the size of electrolytic and other capacitors. I re-capped a pair of dbx 118s, even the ceramic disc caps are now 1/3 the size of the ones in there.

Check that receiver to see if it's truly common-ground. 20 ohms of resistance between the channels made my 1Bs unlistenable.

Schurkey

lbcgav wrote: »

If I recall correctly, in the 2A, the large caps are in series. I spent a lot of money on those coke can caps in mine.

You're right. For some frequencies they're in series with the speaker - terminal.

polk(2)a party

SDA cable is original, and correctly wired when I tried it, but I was hearing whatever it was I didn't like about the tone without the SDA connected. Using the aforementioned marantz, but have an eye out for something else.

So I did the RDA 194's, JB Weld on the drivers, dynamat the PR, hurricane nuts all around, film on the main, and electrolytics on the sda section. Tried all electrolytics first, and accidentally swapped the 12 and the 20. I thought that one sounded better, actually, because it was more even/blended. Then I realized that was because the PR wasn't pumping out the bass like the unmodified one, go figure.

Bought the film caps and despite double checking because of my first mistake, I accidentally swapped the 12 and 20 again on one of the speakers, and had to Frankenstein them back in with their old clipped leads. You don't have to worry about me selling them after that soldering job.

Clearly I don't have golden ears - the tweeters made an improvement, but the rest didn't change anything as far as I could tell. I think maybe it's just that listening distance (6-8 feet) is too short for speakers this size. I'll try rearranging my apartment this weekend.

westmassguy

There are two critical internal connections on the 2As to check, as well as ensuring correct polarity for the woofers and tweeters. The two wires coming from the interconnect socket are reversed. It doesn't matter which way you connect them to the crossover, just make sure one is connected the opposite of the other. The second critical connection is between the lower and upper crossovers. The black and white wires must go to the proper spade connector. They're easy to identify. There's a black wire next to one, and a white wire next to the other. Connect the black and white wires from the lower crossover to the spades with the same color wire next to them.
Make sure all the drivers are wired correctly and in phase. The white wires are Negative/Ground, and the Black and Blue wires are Plus/Hot. Make sure the Stereo and Dimensional drivers are in the correct positions. Dimensional drivers are always on the outside, and stereo drivers on the inside.