SDA 1C electronics upgrade questions TL Mods?

pkquat · March 2016

Will new larger caps and Mills resistors fit on the existing board ok or should I get new boards (before they are gone?) to avoid headaches? Are new inductors recommended? Would new caps and inductors fit on the stock board? I thought I saw a shopping list for 1C's at one time (non TL mod) but I can't find it now. If I should get new boards, is there only 1 board, or are there model specific ones?

This is the only reference I have found to TL mods. http://forum.polkaudio.com/discussion/91633/rdo-198s-in-sda-1cs
Has any further ground been made on this?
I plan on having four RDO198s for some 5jr's so I could at least try it. I am also confused if both tweeters are 198s or it is a combo of 198 and a 194? I stumbled across a post that I can't find again with two SL3000 tweeters in a SDA 1C.

Sometimes searching and choosing the right terms and quotes feels like pulling the handle on a slot machine.

westmassguy · March 2016

The new caps will fit on the old boards, but you need to be creative:

The New Boards are better quality, and give you a lot more room:

There is no "Sanctioned" TL Modification for the 1C, but I'm working on it.

smglbrth · March 2016

Westmassguy is the person you want to PM about the upgrade(s), he's the "goto" person for this stuff now. You can also visit his website at dhsspeakerservice.com. Welcome to the rabbit hole...

pkquat · March 2016

TY. While not impossible, I'll get new boards. It appears there is only one board for all models, correct? Would a "sanctioned" TL mod be a simple mod, at worst, ~100 for parts change, better if it is only adding parts, or might be be a major rework?

pitdogg2 · March 2016

pkquat wrote: »

TY. While not impossible, I'll get new boards. It appears there is only one board for all models, correct?

yes but it is only for single board XO's not the 2 Board XO's

pkquat wrote: »

Would a "sanctioned" TL mod be a simple mod, at worst, ~100 for parts change, better if it is only adding parts, or might be be a major rework?

The TL mod was made for the CRS+ and just happened to work for SDA2b also as they shared the same XO basically SO everything else other than those two is UN-sanctioned so to speak.

F1nut · March 2016

pkquat wrote: »

TY. While not impossible, I'll get new boards. It appears there is only one board for all models, correct? Would a "sanctioned" TL mod be a simple mod, at worst, ~100 for parts change, better if it is only adding parts, or might be be a major rework?

There is one board for certain models only. This information is listed at www.gimpod.com.

As westmassguy stated, "There is no "Sanctioned" TL Modification for the 1C" and I'll add that at this point in time any TL mod you may find for those speakers is nothing more than a hack job.

pkquat · March 2016

I've had time to poke Gimpods site more, and it is making more sense.

I've been poking around the schematics more too and trying to understand the SDA part of it. Based on the SRS2 and the 1C can I assume the inductor between the negative MW arrays is the time delay between the two to account for the speaker spacing, and possibly the rest of the circuit. The rest of the circuit is the cross over?

PolkieMan · March 2016

The boards are worth every penny. The xover and 194 tweeters made a huge difference

heiney9 · March 2016

pkquat wrote: »

I've had time to poke Gimpods site more, and it is making more sense.

I've been poking around the schematics more too and trying to understand the SDA part of it. Based on the SRS2 and the 1C can I assume the inductor between the negative MW arrays is the time delay between the two to account for the speaker spacing, and possibly the rest of the circuit. The rest of the circuit is the cross over?

The speaker spacing has to do with the average distance between a humans ears (our head). The dimensional array is feed a low level, narrow freq band of information from the opposite channel. It's a passive system.

This article explains it with graphs and pictures.

http://www.polksda.com/srsreview.shtml

H9

Schurkey · March 2016

pkquat wrote: »

Based on the SRS2 and the 1C can I assume the inductor between the negative MW arrays is the time delay between the two to account for the speaker spacing, and possibly the rest of the circuit. The rest of the circuit is the cross over?

The inductor isn't part of a time-delay that I'm aware of. The inductor allows the SDA drivers to do "double-duty" by also providing bass support for the stereo drivers. The inductor provides a filtered ground-path for the signal driving the SDA mid-woofers.

The time-delay is accomplished physically in the spacing between the Stereo drivers and the SDA drivers. Thus the stereo drivers are to the inside of the cabinets, so the phase and anti-phase signals arrive at each ear in synchronization.

The third, fourth, and fifth-generation SDA speakers put the tweeter(s) farther to the outside than the stereo mid-woofers; this would serve to time-align the treble to the midrange frequencies. Other speakers set the tweeters farther back in the cabinet so the voice-coils align with the larger drivers.

For the record, this thread pushed me over the edge. I ordered the Gimpod boards from westmassguy about fifteen minutes ago.

There is no "sanctioned" 1C / SRS 2 pin/blade "TL" mod, however I plan to experiment with that some...at whatever point I get back to my SRS 2s. They've waited a year-and-a-half with nothing more done to them than to glue and dampen the midwoofers, what's another year?

pkquat · April 2016

I looked at the SDA literature again. I always thought there was some time delay, but I see now it is simply isometric triangles. The true sweet spot location varies depending on the on the stereo/dimensional speaker width, listeners head width, and location relative to the speakers. The centerline tweeters, time alignment, and tweeter roll off, I have yet to wrap my head around. I get time alignment for standard speakers. I always wondered how the center/offset tweeter worked for SDA, much less not sounding way off without the SDA cord.

On a side note are there impedance graphs for SL200's or RDO194's and RDO198's? They may help in working out a 1C TL mod and tweeter roll off.

honestaquarian · April 2016

pkquat wrote: »

I looked at the SDA literature again. I always thought there was some time delay, but I see now it is simply isometric triangles. The true sweet spot location varies depending on the on the stereo/dimensional speaker width, listeners head width, and location relative to the speakers. The centerline tweeters, time alignment, and tweeter roll off, I have yet to wrap my head around. I get time alignment for standard speakers. I always wondered how the center/offset tweeter worked for SDA, much less not sounding way off without the SDA cord.

On a side note are there impedance graphs for SL200's or RDO194's and RDO198's? They may help in working out a 1C TL mod and tweeter roll off.

Remember the Stereo Dimensional Array's (SDA) reason for existence is to cancel the interaural crosstalk distortion inherent in Stereo loudspeaker listening. That being the fact that both ears are hearing both loudspeakers. Ideally only one ear should hear each respective loudspeaker (*left channel to left ear. Right channel to right ear*) So the dimensional array is sending out a signal "borrowed" from the opposite channel,reversed in phase and delayed just enough to arrive at each ear at the same time as the signal from the opposite loudspeaker. This way they cancel out. I always thought the delay was introduced inside the crossover,but it could also be the spacing between the drivers which introduces the delay.

gimpod · April 2016

pkquat wrote: »

On a side note are there impedance graphs for SL200's or RDO194's and RDO198's? They may help in working out a 1C TL mod and tweeter roll off.

As far as I know Polk never released that info. BTW the boards are only for 4th & 5th gen SDA's.

Besides the tweeter roll off issue. what do you do about the second tweeter, then there's phasing and balancing with the stereo and dimensional drivers. This is no easy task (if it was Polk would have done it) to get it right your basically talking about redesigning the whole crossover, with out all the specs on the tweeters, drivers, cabinets and some expensive testing gear I don't see it happening. Just take a look at the differences between the 2.3 & 2.3TL also the 1.2 & 1.2TL. JMHO upgrade the crossovers, upgrade the tweeters to the RDO-194's plus the other standard mods and call it a day. After about 200 - 400 hours of break in I'm sure you'll be pleased.

honestaquarian · April 2016

Yes
Yes
To @gimpod you listen❕
(*since the upgraded boards are his*)

PolkieMan · April 2016

And even if you did all that would you notice a difference? Mine sound awesome I would not even take $1000 for them.

gimpod wrote: »

pkquat wrote: »

On a side note are there impedance graphs for SL200's or RDO194's and RDO198's? They may help in working out a 1C TL mod and tweeter roll off.

As far as I know Polk never released that info. BTW the boards are only for 4th & 5th gen SDA's.

Besides the tweeter roll off issue. what do you do about the second tweeter, then there's phasing and balancing with the stereo and dimensional drivers. This is no easy task (if it was Polk would have done it) to get it right your basically talking about redesigning the whole crossover, with out all the specs on the tweeters, drivers, cabinets and some expensive testing gear I don't see it happening. Just take a look at the differences between the 2.3 & 2.3TL also the 1.2 & 1.2TL. JMHO upgrade the crossovers, upgrade the tweeters to the RDO-194's plus the other standard mods and call it a day. After about 200 - 400 hours of break in I'm sure you'll be pleased.

pkquat · April 2016

I'm still new, curious, and enthusiastic. Its not that I don't believe people. I'll have my 5jr's TL modded, and people are still preferring TL mods, so there must be something to it. The basic TL mod is a simple capacitor change, so there has to be knowledge of what is different and why. There are TL SDA's with 1, 3, & 4 tweeters. It would seem logical that 2 would be possible. In today's age, I like to think "we have the technology" we can build it. I am more mechanical, than electrical, and maybe don't comprehend the complexity completely. That may be part of it. I do understand it may not be possible. Although there are 1, 3, & 4 combinations, 2 could be a Tacoma Narrows bridge scenario where given the parameters available, under the required conditions it all goes wrong. Until that is known, and therefore not possible, I am keeping hope alive that a TL mod is possible.

honestaquarian · April 2016

Remember just how badly the Takoma Narrows bridge scenario went though.................

Dennis Gardner · April 2016

The TL mod could be possible, just not engineered and supported by Polk. You have to realize that a lot has changed at Polk since Matt left the scene. Nothing new has come out for support of legacy models that wasn't blessed by him in his last few years at the helm. The new guard is simply carrying forward the old directions, and I doubt any thought of spending new $$ after old tech is rare. That doesn't mean that someone with the understanding on this board couldn't make it happen, it just won't be Polk's time or money doing it.

ken brydson · April 2016

honestaquarian wrote: »

Remember just how badly the Takoma Narrows bridge scenario went though.................

TACOMA

https://www.youtube.com/watch?v=j-zczJXSxnw

BlueBirdMusic · April 2016

As I remember, the Takoma Narrows bridge problem was caused by aliens invading Earth using ray guns. At least on TV, it was.

Toolfan66 · April 2016

I say quite obsessing over the TL, and mod them as they are, the 1C 's are fantastic as is..

MrBuhl · April 2016

^^ +1 ^^ Modded 1c's are very formidable indeed despite no TL mod.

pkquat · April 2016

Toolfan66 wrote: »

I say quite obsessing over the TL, and mod them as they are, the 1C 's are fantastic as is..

I can't argue that, and not trying to argue, I'm just not quite ready to give up on it yet. As I said "I'm still new, curious, and enthusiastic", though not so much so dig out my speaker building books (just yet... I'm not sure where they are either). Like I am sure most people are, I am busy with many things. Electronic circuits are not my forte so tying to figure out what all is going on with the crossovers would take me a while, if at all. I am still getting back up to speed on some of the terminology. On the positive side there are many quick calculators out there for simple circuits, and other more robust programs now days.

That said, playing devils advocate, their are many accepted mechanical and ?minor? electrical non "sanctioned" polk modifications done to SDA and other polk speakers here (not trying to ruffle any feathers), so I am still open to the thought that an acceptable solution exists. I don't have all the history as some threads are 10 years old. Maybe the ship as sailed, but I haven't found a number of threads on the subject. I haven't done extensive searching either, so maybe its already been beaten to death.

Has anyone determined or been given info for the basis for the change from a 12µF capacitor to a 13.5µF for non SDA TL mods? That seems like a good starting point.

Schurkey · April 2016

pkquat wrote: »

Has anyone determined or been given info for the basis for the change from a 12µF capacitor to a 13.5µF for non SDA TL mods? That seems like a good starting point.

First Guess: The "starting point" is to remove the 4.4uF capacitor from the HF circuit, and replace with a 5.8uF cap.

That's my intention with my SRS 2 p/b, assuming I ever get back to working on them.

pkquat · April 2016

Schurkey wrote: »

First Guess: The "starting point" is to remove the 4.4uF capacitor from the HF circuit, and replace with a 5.8uF cap.

I would call that a later step in my plan, unless there is some prior knowledge. It is an easy try it and see what the effect is step. I think that has been tried, but IDK the background for it or results. It would be awesome if it was that simple sonically.

My step 2, if needed, was to figure out the basis for the CRS+/2b 5.85µF mod.
Step 3 (probably the easiest step) figure out the tweeter order top to bottom relative to the schematics for the multiple tweeter versions.
Step 4 compare the highest pass and lowest pass circuits. They appear similar. Maybe look at the mids as needed.
Step 5 compare the TL changes based on prior knowledge.

westmassguy · April 2016

pkquat wrote: »

Schurkey wrote: »

First Guess: The "starting point" is to remove the 4.4uF capacitor from the HF circuit, and replace with a 5.8uF cap.

I would call that a later step in my plan, unless there is some prior knowledge. It is an easy try it and see what the effect is step. I think that has been tried, but IDK the background for it or results. It would be awesome if it was that simple sonically.

My step 2, if needed, was to figure out the basis for the CRS+/2b 5.85µF mod.
Step 3 (probably the easiest step) figure out the tweeter order top to bottom relative to the schematics for the multiple tweeter versions.
Step 4 compare the highest pass and lowest pass circuits. They appear similar. Maybe look at the mids as needed.
Step 5 compare the TL changes based on prior knowledge.

The 5.8uf Cap and Resistor in parallel, are called a Contour Network. It was added to compensate for the SL3000/RDO-198s rising response as the frequency drops.
The 5.8uf Shunt Cap was added to an EXISTING 2.7 ohm resistors in the hi-pass circuit of the CRS+.
You cannot simply add it to the 1Cs circuit, and expect the same results, nor will changing the 4.4uf cap to a 5.8uf in the lower Tweeter's circuit magically make it compatible with the RDO-198.
We don't have the T/S parameters, frequency response, or impedance curves for any of the vintage tweeters, or their RDO Replacements.
Without this critical information, you're just poking around in the dark.

F1nut · April 2016

I like to poke around in the dark.

westmassguy · April 2016

F1nut wrote: »

I like to poke around in the dark.

I'm offended. I'm telling. Where's my safe place?

Gunther16 · April 2016

Don't hold up your hands and shake your head! LMAO

lightman1 · April 2016

Holy crap! Jesse IS funny! Wow!

ken brydson · April 2016

F1nut wrote: »

I like to poke around in the dark.

What was his name again?

SDA 1C electronics upgrade questions TL Mods?

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