RDO 198s in SDA 1Cs

inspiredsports

geppy1 wrote: »

OK so is this true?? The 5.8 cap and 2.7 resister have to go inline after the crossover and only to the top tweeter??? keith

Hi Keith,

In a nutshell, yes.

Summing up the 2 most decisive posts in my original thread at . . .

http://www.polkaudio.com/forums/showthread.php?t=74946

- - - Posts # 85 by GV#27 and #90 by Disc Jockey led me to the conclusion depicted in my image at the bottom of Post #135.

##############################

If you study the the schematic of your 1C available here on CP and compare it to my image in my thread's post #135, you will see why most do not believe the 1C can be TL'd according to the principles discussed in posts 85 and 90 cited above.

Anyone following the mod Ben described above would mistakenly be boosting frequencies Polk did not want to be boosted, and would additionally be boosting the lower tweeter signal which is to be rolled off, NOT boosted.

Additionally, there are numerous unpublished back stories to this process. I even went out and bought a beat up SDA-1B which is identical to the 1986 SDA SRS 2 in drivers and crossover with the exception of 1 resistor value. I changed the resistor to the proper value, and then went on to use this backup crossover to experiment with different values in different spots to prove the mod I ended up publishing.

Greg

inspiredsports

Last point, but the one that drew me to this thread in the first place and I forgot to mention is that I want to own TL'd 1C's myself and have been following this train of thought since November of '08. when I set out to TL my 1986 blade/blade SDA SRS 2's.

If there is a way to run the 1C with RDO198-1's, I aim to find it.

F1nut

geppy1 wrote: »

OK so is this true?? The 5.8 cap and 2.7 resister have to go inline after the crossover and only to the top tweeter??? keith

The problem that I see here is what do you do with the second tweeter? If you keep the RD0194-1 in that position it's not going to sound right with a RD0198-1 in the top position. Replacing the second tweeter with a RD0198-1 isn't going to work either as that circuit isn't designed for it even considering the rolled off response.


Greg, bring me up to speed. What did you do about the second tweeter in your SDA SRS 2's?

geppy1

Interesting point. Keith

inspiredsports

F1nut wrote: »

The problem that I see here is what do you do with the second tweeter? If you keep the RD0194-1 in that position it's not going to sound right with a RD0198-1 in the top position. Replacing the second tweeter with a RD0198-1 isn't going to work either as that circuit isn't designed for it even considering the rolled off response.


Greg, bring me up to speed. What did you do about the second tweeter in your SDA SRS 2's?

After replacing the 4.4uf cap with a 5.8, I tried it both ways. Meaning always an RDO198-1 on top, and at first with RDO194-1's on the bottom for about 120+ hours, and then with RDO198-1's that have remained there since.

The tone testing I did was good with either variety in place in the bottom position (meaning an essentially flat curve). A bit more treble is produced with the RDO198-1's (approx. 3db if I recall correctly) , but the biggest factor is that (in my opinion) the 198's sound clearer and cleaner.

RDO198-1's in all positions is my strong recommendation (and caused the SDA SRS 2's to sound the closest to my TL'd SDA-2B's).

I'd love to solve the mystery of TL'ing a 1C, but I honestly don't see how it can be done.

AustinGold

If you are still interested in selling those RDO198's please send me a pm with your contact info. Since, I am new to the forum it will not allow me to send a PM to you till I have 10 posts to my name. Thanks.

F1nut

You can buy them directly from Polk Audio....give'em a call.

Big Dawg

inspiredsports wrote: »

RDO198-1's in all positions is my strong recommendation (and caused the SDA SRS 2's to sound the closest to my TL'd SDA-2B's).

Should I read this as "closest, with all the benefits of the SRS2s' wider sound stage and deeper bass, yet still not quite as nice"?

Vette C6.r

JohnLocke88 wrote: »

I don't get how this is "guess" work. the 4.1 TL mod consists of this for the CRS+ and the 2B. Both of those run SL2000 tweeters as well. Unless having two tweeters in the HF circuit would wonk this up.

I'd trust Ben on this one though.

Not to thread-jack but what the heck are 4.1's.

Did they ever make production ???

F1nut

Not to thread-jack but what the heck are 4.1's.

The 4.1TL was a Polk planned upgrade to the CRS+ pin/blade. It added a 5.8uF cap in order to use the SL3000/RD0198-1 tweeter.

Did they ever make production ???

I have seen a military sales brochure that listed the CRS+ as a 4.1TL, but it does not appear that any were actually sold as the production of SDA's ended at that time.

The upgrade is easy to do and many here, including myself have done it. I first changed the SL2000 to the RD0194-1 and was not happy with the sound. I then performed the TL upgrade and I'm very pleased with the results.

madmax

george daniel wrote: »

Gotta disagree,, they are very smooth and laid back in my system.

Agree, very smooth.
madmax

george daniel

So,, I am under the impression that there is not a "Polk sanctioned" mod/upgrade for the tl'ing of 1C's.Have we not been over this before?IIRC a few people have completed/had this mod performed--with mixed results,,the more appealing mod/tweak at the moment,at least for me,is Larry's cabinet dampening.

F1nut

So,, I am under the impression that there is not a "Polk sanctioned" mod/upgrade for the tl'ing of 1C's.

Correct.

bigaltx24

Has anyone tried the RDO-198s in a pair of 1Bs? I had been thinking about replacing the SL-2000s with the 194s, now I might have to consider doing the TL mod.

hearingimpared

bigaltx24 wrote: »

Has anyone tried the RDO-198s in a pair of 1Bs? I had been thinking about replacing the SL-2000s with the 194s, now I might have to consider doing the TL mod.

I would definitely do the TL mod, it really isn't that hard and the 198s are much better sounding than the 194s.

Schurkey

bigaltx24 wrote: »

Has anyone tried the RDO-198s in a pair of 1Bs? I had been thinking about replacing the SL-2000s with the 194s, now I might have to consider doing the TL mod.

Yup. I followed inspiredsports (Thank you!) lead with his SRS-2 blade/blade upgrade.

I installed the added capacitance, and put 198s in the upper positions. Still have SL2000 in the lower positions.

The only "catch" is trying to find push-on connectors small enough to fit the one terminal of the 198s. The other terminal is the same as what's on the 2000s.

I did a bunch of mods in a fairly short period of time; the end result is that I was MUCH happier with the sound after re-capping the crossovers, replacing a defective tweeter, sealing all the drivers to the cabinet, and damping the MWs and passive radiators. Nevertheless, I still thought the treble was lacking.

I suppose "someday" I'll add another pair of 198s in the lower positions. At this point, I've got a small quasi-ribbon "supertweeter" mounted on top of each cabinet, crossed in at ~11Khz with a simple, one-capacitor filter. The Q-ribbon is giving me the treble I've wanted--but didn't have--from these speakers since they were new.

I also added a 1C-style interconnect cable terminal, bypassing the 185uf capacitance in each crossover; it's set up so I can use either the stock 1B-style interconnect along with the capacitance; or use the 1C style, so it's compatible with an AI-1. Listening with the 1C style interconnect has been a bit of a disappointment, though. There isn't as much SDA effect as the stock wiring.

inspiredsports

bigaltx24 wrote: »

Has anyone tried the RDO-198s in a pair of 1Bs? I had been thinking about replacing the SL-2000s with the 194s, now I might have to consider doing the TL mod.

Yes. Remove the 4.4uf cap and insert a 5.8uf cap in that spot. That's all that's needed to allow the RDO198-1 to work properly in the top tweeter spot.

inspiredsports

Schurkey wrote: »

Yup. I followed inspiredsports (Thank you!) lead with his SRS-2 blade/blade upgrade.

I installed the added capacitance, and put 198s in the upper positions. Still have SL2000 in the lower positions.

The only "catch" is trying to find push-on connectors small enough to fit the one terminal of the 198s. The other terminal is the same as what's on the 2000s.

I did a bunch of mods in a fairly short period of time; the end result is that I was MUCH happier with the sound after re-capping the crossovers, replacing a defective tweeter, sealing all the drivers to the cabinet, and damping the MWs and passive radiators. Nevertheless, I still thought the treble was lacking.

I suppose "someday" I'll add another pair of 198s in the lower positions. At this point, I've got a small quasi-ribbon "supertweeter" mounted on top of each cabinet, crossed in at ~11Khz with a simple, one-capacitor filter. The Q-ribbon is giving me the treble I've wanted--but didn't have--from these speakers since they were new.

I also added a 1C-style interconnect cable terminal, bypassing the 185uf capacitance in each crossover; it's set up so I can use either the stock 1B-style interconnect along with the capacitance; or use the 1C style, so it's compatible with an AI-1. Listening with the 1C style interconnect has been a bit of a disappointment, though. There isn't as much SDA effect as the stock wiring.

I am in the process of listening critically again to both my TL'd SDA 2B's and TL'd SDA SRS 2's side by side and agree with Shurkey's comments above that the SDA SRS 2 treble is still a touch understated even after modding. It's not a bad thing, just a bit less treble in relation to bass than the 2B. I also felt the treble was a bit weak in unmodded form.

My thoughts are that the 3.5 resistor in this crossover was chosen as the original SL2000's in this cabinet were a bit harsh. I also note that the nearly identical SDA-1b uses a 2.0 resistor in this spot and it is a SMALLER cabinet which goes against expectations. HOWEVER, the SDA SRS 2 came off the drawing board in Nov 1985, and the SDA-1B a year later in Nov 1986 so I'm guessing it was a refinement made to improve the treble balance.

I now have my NAD 7600 Receiver on the SDA SRS 2's which allows for 0-6 db boost at 12 kHz. Somewhere between just below the full 6 db of boost at 12 kHz makes the treble balance (treble level in relation to bass level) sound perfect to me.

I have been wanting to replace the 3.5 resistor with a 2.7 for a long time and am finally going to give it a try to see if this brings the treble level up a few db.

bigaltx24

Yes. Remove the 4.4uf cap and insert a 5.8uf cap in that spot. That's all that's needed to allow the RDO198-1 to work properly in the top tweeter spot

.

Can I put 198 in both spots, or just one in the top, leaving a SL2000 in the bottom spot?

Schurkey

bigaltx24 wrote: »

.

Can I put 198 in both spots, or just one in the top, leaving a SL2000 in the bottom spot?

Inspiredsports tried it both ways, prefers 198s in both locations.

My 1Bs have 198s in the top, and SL2000 in the lower position. It works, and is better than 2000s in both locations, but doesn't provide enough treble for me. That's why I added the quasi-ribbon supertweeters.

inspiredsports

bigaltx24 wrote: »

.

Can I put 198 in both spots, or just one in the top, leaving a SL2000 in the bottom spot?

RDO198's in the bottom spot made my treble quality clearer and cleaner, but not discernibly louder. From an electrical standpoint the crossover does not care which tweeter occupies the lower spot. As noted above, I will be lowering the value of the first resistor in my crossover to raise the overall tweeter volume a bit.

plastic_avatar

inspiredsports wrote: »

ben62670 wrote: »

It's an easy mod. All you have to do is parallel a 5.8uf cap with a 2.7 ohm resister where the poly switch is located.

]

The 1C circuit is entirely different than the 1B, 2B, CRS and SRS 2 circuits that can take the mod in that there is no 4.4 already in play in the right location to be replaced. The 5.8 in the 4.4 spot to allow for the substitution of the RDO198-1 was suggested by Matthew Polk. Placing it anywhere else would be speculative.

Well, let's see who's still around who can answer this decade+ long question:

Did anyone figure out how to run the 198 in a 1c?

I hear from some astonishingly clever modders that it's a fool's errand to chase this goose.

I came across this thread and thought:

'Maybe there's new knowledge about this seemingly impossible mod? I'll go ahead and ask... even though it makes me feel like that guy who brought a snowball to Congress while he tried to argue that the climate isn't changing.'

And just to be clear, climate change is real.

And I fear a 198 to 1c mod is that snowball.

F1nut

Can't be done, at least not properly.

xschop

Would it be feasable to put a factory RD0198 in the top spot and rebuild the lower tweeter with a silk dome (@7 ohm IIRC)?

xschop

Edit... 6.5 ohm silk dome in the bottom spot.

Gardenstater

RDO-194 are 6.60 Ohms so that certainly is pretty spot on (almost dead on balls accurate as Mona Lisa Vito would say if she were here). Le = 0.066 mH @ 10 kHz. Does anyone have an inductance meter to test one of these Made in China Silk Dome voice coils?

Reference:

The Tale of 5 Tweeters https://forum.polkaudio.com/discussion/182943/the-tale-of-5-tweeters-sda-tweeter-replacement-guide/p1

F1nut

I hate repeating myself, but...
Can't be done, at least not properly.

xschop

F1nut

Give it up.

xschop

My Fluke has them at 6.4 ohm