SDA 1b vs CRS+

jimbo1421

Hello everyone,

I finally got my recently acquired pair of CRS+ set up last night. I borrowed RDO-194s from my Monitor 10s and resealed all of the drivers with Mortite. However the press test only yields 2-1/2 seconds for the MWs to return. I know that I am getting some leakage through the pin/blade jack. I also reattached the crossover circuit board to the large coil. It had broken loose and been secured with zip ties by a previous owner. Now they are perched atop my SDA-1bs (too high) with an RCA cable as a temporary (and somewhat loose) interconnect. They are placed as shown in the attached floor plan. Note that the backs of the cabinets are 19" from the wall in order for the face of the speakers to be in front of the short wall between the living and dining rooms.

The task now is to pick one of these pairs as my permanent fronts and spend some time and money on upgrades and improvements on one of them. My main focus is on two channel audio, primarily vinyl, with home theater of secondary importance. I don't think it will be an easy choice.

As expected, the RDO-194s are a big improvement over the SL-2000s in the SDA-1bs. Bass response is less deep in the CRS+ (as the specifications would suggest), but seems somewhat better defined. Perhaps the CRS+, with its rear facing passive bass radiator, functions better this far away from the wall than the SDA-1b. (Note that I only use the PSW-10 for LFE)

The SDA effect is quite different however. The SDA-1b sound stage is a great deal deeper, almost U-shaped. I sometimes even hear some right channel stereo sound that appears to emanate from the right rear surround. This can be disconcerting at times. By contrast, the soundstage of the CRS+ seem flat across the space, extending a few feet beyond either speaker. The CRS+ imaging is more precise than the SDA-1b. It also seems better balanced, but that could be due to the source material. Overall, my first impression is that the CRS+ is a better fit for the space (which is only 13'-2" deep) with fewer SDA oddities.

So my wish list for each of these pairs of SDAs is as follows:

SDA-1b:
Replace 4 SL-2000s with RDO-194s.
Tighter, better defined bass.
A better balanced soundstage, less deep, with more precise imaging.

CRS+:
Deeper bass response without sacrificing definition.
A deeper soundstage without sacrificing precise imaging.

Can anyone here comment on how attainable these wishes are for each type of SDA? I expect that I will spend the next few months comparing the two before deciding.

On a side note, as a crusty old bachelor I have to supply my own WAF. I think the CRS+ will look better (less dominating than the SDA-1b) in the space.


Thanks for reading all this,

Jim

Schurkey

If you have 1Bs, forget the 194s and go directly to the 198s along with the matching 5.8uF cap in each speaker HF crossover instead of the existing 4.2uF cap.

Of course, the usual capacitor and resistor upgrades in either speaker crossover goes a LONG way; as will the usual host of repairs and modifications: pulling the interior "fluff" back up into proper position; damping material on the drivers, etc. Verify that everything is functioning as intended--proper driver polarity, correct drivers installed (all 6509s for the 1Bs) and so forth. Spikes on the cabinets if the speakers sit on carpet.

I have purchased--but not installed--iron-core inductors for my 1Bs, and am looking forward to a modest improvement in an otherwise exceptional product.

I'd hate to see you lose out on the 1Bs due to oddball SDA effects. I think they're a result of the speaker/room interface. Of course, if you're locked-in to a certain speaker placement, different speakers may be your only option.

jimbo1421

Schurkey wrote: »

If you have 1Bs, forget the 194s and go directly to the 198s along with the matching 5.8uF cap in each speaker HF crossover instead of the existing 4.2uF cap.

Of course, the usual capacitor and resistor upgrades in either speaker crossover goes a LONG way; as will the usual host of repairs and modifications: pulling the interior "fluff" back up into proper position; damping material on the drivers, etc. Verify that everything is functioning as intended--proper driver polarity, correct drivers installed (all 6509s for the 1Bs) and so forth. Spikes on the cabinets if the speakers sit on carpet.

I have purchased--but not installed--iron-core inductors for my 1Bs, and am looking forward to a modest improvement in an otherwise exceptional product.

I'd hate to see you lose out on the 1Bs due to oddball SDA effects. I think they're a result of the speaker/room interface. Of course, if you're locked-in to a certain speaker placement, different speakers may be your only option.

Thanks, Schurkey. I didn't realize the SDA-1bs could take the RDO-198s with a cap change.

My first step probably should be to make up a good interconnect. If I can't find a pin/blade cable, Allied Electronics has the jacks and plugs to make up a blade/blade cable. It looks like the jack can be swapped out in the terminal cup, but I need to take the cup out again to confirm this.

I have been told that only the pin carries the dimensional signal, but I noticed that the blade part of the jack was connected to the negative speaker terminal. What purpose does this serve?

Jim

audiocr381ve

jimbo1421 wrote: »

Thanks, Schurkey. I didn't realize the SDA-1bs could take the RDO-198s with a cap change.

My first step probably should be to make up a good interconnect. If I can't find a pin/blade cable, Allied Electronics has the jacks and plugs to make up a blade/blade cable. It looks like the jack can be swapped out in the terminal cup, but I need to take the cup out again to confirm this.

I have been told that only the pin carries the dimensional signal, but I noticed that the blade part of the jack was connected to the negative speaker terminal. What purpose does this serve?

Jim

I didn't know 1B's could be "TL'ed" either.

Schurkey

jimbo1421 wrote: »

Thanks, Schurkey. I didn't realize the SDA-1bs could take the RDO-198s with a cap change.

audiocr381ve wrote: »

I didn't know 1B's could be "TL'ed" either.

My thanks to inspiredsports for pioneering this upgrade on his SDA SRS II blade/blade; essentially the same speaker as the 1B except for the obviously larger cabinet, and larger passive radiator. There's one different resistor in the crossover. This was discussed in a multi-page thread some time ago. Here's the thread, it doesn't really get interesting until page 3 or 4.

http://www.polkaudio.com/forums/showthread.php?74946-SDA-SRS-2-Crossover-Parts-list/page5

jimbo1421 wrote: »

My first step probably should be to make up a good interconnect. If I can't find a pin/blade cable, Allied Electronics has the jacks and plugs to make up a blade/blade cable. It looks like the jack can be swapped out in the terminal cup, but I need to take the cup out again to confirm this.

I have been told that only the pin carries the dimensional signal, but I noticed that the blade part of the jack was connected to the negative speaker terminal. What purpose does this serve?

Jim

Might be true for the 1C, the SRS II pin/blade, and the newer-generation SDAs, but the 1B needs BOTH conductors in the SDA interconnect cable. If you upgrade the interconnect cable, you will need a two-conductor substitute, and two jacks at the speaker cabinet. Regarding the 1B, the SDA signal is full-voltage, full-range from one cabinet to the other. You could use an extension of your speaker cables as easily as using the SDA interconnect. Put another way: BOTH speakers receive BOTH left and right channel voltage/current. Thus the need for a common-ground amp; and why a single-conductor AI-1 isolation transformer won't work with the 1B or similar-generation speakers.

It IS possible to convert the 1B to a single-conductor cable; but the sonic results are underwhelming. Not recommended until someone with more electronic smarts that I can figure out a way to make this mod sound right. (light-weight bass) At that point--may the day soon arrive--the 1B and some other blade/blade SDA speakers will be usable with the AI-1 and therefore with monoblock or non-common-ground amps.

anonymouse wrote: »

I had the 1C's and they could NOT be TL'd.

The 1C has the same 4.2uF cap in the HF crossover as the 1B/SRS II blade/blade, although the crossover is more complex. To date, no one has ripped it out in favor of the 5.8uF, and then installed the 198s.

I don't have the mathematics background to say that this will work as a suitable crossover for the 198s...but I have a hunch (and only a hunch) that it will work just fine.

jimbo1421

jimbo1421 wrote: »

My first step probably should be to make up a good interconnect. If I can't find a pin/blade cable, Allied Electronics has the jacks and plugs to make up a blade/blade cable. It looks like the jack can be swapped out in the terminal cup, but I need to take the cup out again to confirm this.

I have been told that only the pin carries the dimensional signal, but I noticed that the blade part of the jack was connected to the negative speaker terminal. What purpose does this serve?

Jim

I should have said that I need a good interconnect for the CRS+. The SDA-1b already has one. I am still wondering why the connection from the blade socket to the negative speaker terminal.

Jim

Mr. Bubbles

anonymouse wrote: »

In the CRS+, you can safely use a single conductor cable to just connect the center pins assuming you have a common ground amp. If you are in a pinch, just hack RCA connectors which have a center pin about the same size as the center pin on the interconnect connector. You carefully remove the outer rim of the RCA and simply connect the center pin to center pin. Just be careful not to short the center pin to the ground.

Please note however, as mentioned previously in the thread, the interconnect carries full current speaker signal. Though the RCA cable will physically work, it's inner conductors are normally no where near the size needed for speaker conductor. I would recommend this only as a temporary testing solution.

It IS possible to convert the 1B to a single-conductor cable; but the sonic results are underwhelming. Not recommended until someone with more electronic smarts that I can figure out a way to make this mod sound right. (light-weight bass) At that point--may the day soon arrive--the 1B and some other blade/blade SDA speakers will be usable with the AI-1 and therefore with monoblock or non-common-ground amps.

I have worked on this with my SRS's with some promising results. It is not a simple mod by any means for the average person. The impedance of the midbass/mid in the dimensional circuit as well as the impedance of the bass in the same circuit of drivers must be addressed simultaneously to keep a balanced sound and smooth frequency response. I will not get into any further detail on this forum about this work as it caused a very ugly issue when I brought it up originally. But I will say that for those that don't have their head up their rear end it can work wonderfully.

Big Dawg

oliverbubbles wrote: »

I have worked on this with my SRS's with some promising results. It is not a simple mod by any means for the average person. The impedance of the midbass/mid in the dimensional circuit as well as the impedance of the bass in the same circuit of drivers must be addressed simultaneously to keep a balanced sound and smooth frequency response. I will not get into any further detail on this forum about this work as it caused a very ugly issue when I brought it up originally. But I will say that for those that don't have their head up their rear end it can work wonderfully.

Not sure what happened in a previous thread, but am curious about what you've done.

DracoAmericanus

I have for just testing used one conductor on the 1b's, but as others have stated full current is needed and the second pin provides part of the ground path, with out it the current for one sda array would need to go though the speaker cable and amp then to the other sda array, on my system would be dubble the signal path with out the second conductor in the sda cable, my guess is the sda effect would be changed because of this.
now for a stupid question, what effect does changing the sl-2000's out have? one of mine has a mismatched tweeter but my idea was restoring it back to all sl-2000's. i guess i need to read a bit more at it.
now i would keep the sda-1b over the CRS but for me the large size of the 1b is not a problem even though i have a smaller living room.

jimbo1421

Hello again,

I found parts to make up a blade/blade IC at Mouser Electronics. The pin/blade socket looks like it can be easily removed by drilling out the pop rivets that secure it to the terminal cup. The blade/blade socket has mounting holes the same distance apart, so it should be an easy swap out. I also ordered plugs to make up a cable. Once this is done I can run the SDA tests from the stickies (http://www.polkaudio.com/forums/showthread.php?55888-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-Stereo-Dimensional-Array(SDA)).

I am enjoying the CRS+ more & more. I think that vintage speakers that sit unused for a long time need a break in period just like new ones.

Mouser part numbers for the IC:

Socket: 538-S-302H-AB
Plug: 538-P-302H-CCT

Jim

newrival

I personally feel the CRS+ is the best SDA speaker i've heard or owned (ive owned 2b, SRS, 3.2tl, CRS+, and heard 2.3, 2.3tl, 1.2tl, 1c) It's my opinion it is the best of the entire line. They, paired with a pair of subs, like REL, are above and beyond the others in refinement. I never modded a pair, nor have I ever heard any modded SDA's, but in stock form, the CRS+'s are where the magic is at. The imaging, as you noticed, really shows off what SDA can really do. I never experienced a shallow soundstage. Quite the opposite. But this could be due tou your wall step out. I think the full ranger's lose clarity and coherence in exchange of bass extension. If the 1b's are as good as the 2b's they are some awesome speakers as well.

jimbo1421

Thanks, newrival. When I get a decent IC set up I hope that will help with the soundstage. That 19" space behind the speakers has been troublesome.

Jim

quadzilla

For smaller rooms, the CRS+, either with RDO-194s or TL'ed with the 198 is definitely the way to go. I really enjoyed mine, but my room is a bit too big.

newrival

quadzilla wrote: »

For smaller rooms, the CRS+, either with RDO-194s or TL'ed with the 198 is definitely the way to go. I really enjoyed mine, but my room is a bit too big.

a sub (preferably multiple subs) will solve that problem. I listened to mine in an L shaped room each leg was over 30' long and 20' deep. with vaulted ceilings. Fully pressurized room (all nodes activated) make a huge difference on the full audio spectrum.

newrival

jimbo1421 wrote: »

Thanks, newrival. When I get a decent IC set up I hope that will help with the soundstage. That 19" space behind the speakers has been troublesome.

Jim

Any way to pull the speakers into the room and out of the niches? As I'm envisioning your description, that seems to be a huge hinderance on soundstage. Maybe hang a heavy curtain across them? The niches, that is.

jimbo1421

Hi newrival. The space for my rig isn't really a niche, but a space between the fireplace and a short (30") divider wall between the living rom and dining room. The two rooms add up to 33'-6" x 13'-2" with an opening 7'-10" x 6'-8" shown just to the right of the right SDA. I think because of this divider/opening, the soundstage tends to wrap around to the right rear, sometimes seeming to emanate from the right rear surround (Monitor 10). The soundstage is more J shaped than U shaped. This effect is much more pronounced with the SDA-1bs than with the CRS+.

I hope this helps explain the issue.

Jim