Got a pair of Polk Audio SDA CRS

cortico

Hi, I have win this pair of speaker on a auction, I wonder which model is this and if they are a good improvement over my monitor 5B... In any event I always been curious about sda effect, this may be a good start.

I may have to do some work on them, seller mentioned that only one tweeter is working...
here are a couple pics.

F1nut

Those are the original SDA CRS with the dimensional tweeter. Most find that disconnecting that tweeter results in a more coherent sound stage.

cortico

Thanks! Sounds good, I'll check the tweeter. Which ones are the dimensional, inside or outside ones?

I just downloaded the schematics and will save some cash to recap them, I'll probably start by replacing the poly switch with a resistor... Any advices?

Oh my...

westmassguy

Those are the original, 2nd generation CRSs from 1984. As mentioned, without the interconnect, the dimensional circuit won't function. That includes the outer tweeter and woofer in each cabinet. Once you have the interconnect in place, test to make sure all the teeters and woofers are functioning, then listen to them with and without the dimensional tweeter connected. Most, myself included, prefer the early SDAs with the dimensional tweeters disconnected. Polk did too, they were eliminated by the 3rd generation.

cortico

Thanks for the answers. I will start by getting a nice pair of stands made and start from there. Then I will need an amp to drive them, but can't spend much.

boston1450

I use a Yamaha cr2040 on my CRS+'s in our bedroom & enjoy them alot. I upgraded the tweeters & resealed cabinets & refreshed the cabinets. I havent done crossovers yet but someday i hope to be doing them too. Enjoy your new to you speakers

cortico

I gave the SDA CRS a careful listening over the weekend and felt in love it them. However, I find the CRS sound more fatiguing than the smooth sound of my upgraded Monitor 5Bs.

In any event, I think they're a keeper and deserve a recap and most likely new tweeters.

Since fully upgrade (caps, resistors and tweeters) will be a big expense, I am thinking in fazing it out. I hope you can give some guidance in what should earn priority in the first round:


1- New RDO-194 tweeters (4) + better/shorter interconnect cable.
or
2- Replace only electrolytic/hi-freq capacitors and resistors using (Sonicaps or Clarity ESA and Mills).

Thanks!

boston1450

Do both in the order you listed. Like you Monitors-they will sound better after. Did you happen to do as F1 & WMG suggested ? I replaced my tweeters & noticed a big difference

boston1450

Its those tweets

cortico

Definitely, I think the CRS would smooth with the new tweeted.

Is there any special procedure to disconnecte the SDA array tweeters? What should be done with the -/+ leads, isolate it from each other?

westmassguy

Nothing special, remove the tweeter, tape off the connectors on the wire leads, then put the tweeter back in. When you eventually start doing some work internally, you can roll up the tweeter harnesses, and make it neat.

machone

I have a pair of 1As that came with the dimensional tweeter. Per this forum I deleted them with great results.

cortico

Got it, the dimensional -/+ tweeter leads will be disconnected and isolated from each other.

If the dimensional tweeters are disconnected, I won't have to replace the hi-freq caps on the dimensional crossover and save a few bucks...

Can you tell me what is the fiction of the little yellow cap bellow the electrolytic on the stereo crossover?

Current setup:


Stereo crossover:


Dimensional crossover:

westmassguy

A Capacitor and Resistor in parallel, form a Contour Network.
http://www.diyaudioandvideo.com/Calculator/ContourNetwork/Help/

cortico

Thank you very much! I will add it to the sonicap order list. I have decided to replace one tweeter pair and will do the stereo arrays crossovers first.

Tweeters
2x RDO-194, (other par will be disconnected)

Capacitors
2x .5uF
2x 20uF
2x 27uF

Resistors
2x 0.5ohm 10w
2x 5.6ohm 10w
2x 2.7ohm 10w

F1nut

NM

Toolfan66

F1nut wrote: »

NM

I'm not sure what you posted, but I have a good idea.. only because I think I was thinking the same thing..

cortico

please say. don't let me do anything silly!

Nightfall

Do you move the coffee table while listening?

westmassguy

Might as well do the Dimensional Lo-Pass while you're in there, two more caps.

cortico

Nightfall wrote: »

Do you move the coffee table while listening?

That placement is temporary and not ideal, I actually ordered taller stands... Would it help if I rotate the table 90 degrees?

boston1450

Those speakers look very nice & i like the stands. Understand the temp placement thing

westmassguy

cortico wrote: »

Nightfall wrote: »

Do you move the coffee table while listening?

That placement is temporary and not ideal, I actually ordered taller stands... Would it help if I rotate the table 90 degrees?

Until you get the new stands, don't knock yourself out. The stands you have appear to be back pitched, which is not good. The CRSs should be perfectly level, and parallel with each other, with no toe-in. The Tweeters should be at or close to ear height when seated.

cortico

I forgot the 12uf caps on my list:

Capacitors
2x .5uF
2x 12uf
2x 20uF
2x 27uF

Resistors
2x 0.5ohm 10w
2x 5.6ohm 10w
2x 2.7ohm 10w

As westmassguy mentioned I might add dimensional low pass caps as well. I will to see how it turns out with the new tweeters before I place the caps order.

cortico

westmassguy wrote: »

cortico wrote: »

Nightfall wrote: »

Do you move the coffee table while listening?

That placement is temporary and not ideal, I actually ordered taller stands... Would it help if I rotate the table 90 degrees?

Until you get the new stands, don't knock yourself out. The stands you have appear to be back pitched, which is not good. The CRSs should be perfectly level, and parallel with each other, with no toe-in. The Tweeters should be at or close to ear height when seated.

Unfortunately, placement will never be ideal on my room... You know micro NYC appartment. However, the seating is low and located on the speaker's oposite wall, not shown in the picture.

The other stands are identical (steel tube filled with sand) but higher, bottom of speaker will be apoximatly at 16" above floor. I can't go heigher in height, but stabds have pins in the back to adjust angle to compensate it somehow...

westmassguy

That's still low. That puts the tweeters at about 26" above the floor. In a normal seating position, your ears are usually between 32-38" for most people. That's the target height for the centerline of the tweeters above the floor.

F1nut

Agreed, way too low and angling them up simply does not work with SDA's.

cortico

Got it! I will work a solution out. These may work better, shelf height is 18" and has adjustable spikes at the base...

westmassguy

You're still only 28"-29" to the tweeter, even with spikes. Ear level.

boston1450

I like SPIKES

westmassguy

boston1450 wrote: »

I like SPIKES

Most New Englanders do............