SDA SRS 2 Crossover Parts list

inspiredsports

I'm extremely pleased with the progress now at about 50 hours. That's given the RDO198-1's time to simmer down (they seem to smooth most of the way after about 30 hours). The sound is just night and day better than with all four 194's.

After about 20 hours of listening time, I had enough of a baseline and I swapped out the last 2 (bottom) RDO194-1's and inserted the remaining RDO198-1's. They are now true SRS SDA 2.1 TL's !!

With all foru 198's, I immediately noticed a very small improvement in sound quality and they only have about 24 hours on them so they will continue to smooth out a bit more with time.

All of this is being done with the 5.8uf Sonicap at only about 15% of its known burn-in requirement, but having fiddled with my SDA-2B's with the same mod, I think my assessments are accurate.

Repeating from a prior post, I think replacing the bottom two 194's with 198's is just an incremental improvement. The real gain, perhaps 90+%, came form replacing the 4.4 cap with a 5.8 and replacing just the top two 198's. The bottom line is this upgrade can be done incrementally with no problems.

Ben mentioned possible "holes" in the frequency response. Using my ears and about 40 LP's/CD's plus a test tone CD, there are none so far. This mod simply works well to vastly improve a once lackluster speaker.

I would urge anyone contemplating the upgrade to HOLD OFF until I have about 400 hours on the upgrade because I plan to cycle back through listening to two plus two 198's / 194's and all four 198's, and then perform 1 more major tweak.

I theorize Polk used the lead-in 3.5 ohm resistor in the high pass of this particular model because the original SL2000's were so harsh sounding. With the sweeter RDO194-1's, and especially the RDO198-1's, I don't think that much reduction is necessary.

When everything settles, I'm going to reassess, but believe I will replace the 3.5 resistors with 2.7 or maybe even 2.0 ohm resistors to boost the treble to bass ratio.

###########

I also briefly listened to the speakers with just the top two 198's (bottom two tweeters disconnected). I want to do this again after I boost (lower the resistor value) as the volume was just a few db's weak. Phasing, naturally was perfect, but it doesn't seem to be an issue with all four of any combination in play either.

Face

Are you using a SPL meter with the test tones.

Just so you know, except in the bass region, using your ears to determine if there are any holes in the FR is a very poor method.

Face

If you really want to measure FR, here you go.

http://www.fesb.hr/~mateljan/arta/

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=248-625

http://pro-audio.musiciansfriend.com/product/Edirol-UA4FX-USB-Audio-Capture-Interface?sku=241810&src=3WFRWXX&ZYXSEM=0&CAWELAID=26020141

If you want to measure impedance curves and T&S info: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-803

inspiredsports

Face wrote: »

Are you using a SPL meter with the test tones.

Just so you know, except in the bass region, using your ears to determine if there are any holes in the FR is a very poor method.

I'm using a calibrated Extech 407730 and a test tone CD, but I've also already done hundreds of direct A/B comparisons with my SDA-2B's.

I'm using passages of music with which I'm very familiar and switching from A to B literally in milliseconds through my NAD 7600 receiver. I also have a number of duplicate LP's / CD's in my collection that allow yet another dimension of comparison.

I've also seen this argument too many times to become embroiled in it. I like to use empirical testing as a sanity check, but I think most here in Club Polk have come to rely heavily on the "trust your ears" concept.

You're going to have to trust me on this, or do the mod yourself to refute my opinions

SDA SRS 2.1 TL's ROCK !!

inspiredsports

I'm closing in on 100 hours of continuous use. The RDO198-1's have smoothed out and the 5.8uf caps are progressing nicely.

Having listened to my SDA-2B complete crossover upgrade in December and the original SDA SRS 2 complete upgrade in January, it's interesting to note the similarities.

It seems the tweeter sound starts out nondescript and "jumbled". Specific source locations are difficult to pinpoint. As the burn in progresses, the phantom center channel magically appears. Then the sound-stage starts to widen a bit. That's where we are now.

With the prior upgrades, I'll never forget how the sound just started to creep outward from cabinets toward the sidewalls, and then down the sidewalls until it was at about 180 degrees.

I keep switching A/B to by SDA-2B's as a reference and can detect little sound quality difference. Sound quantity is a different matter with the treble from the 2B's being a bit more forward as there is less resistance built into that single tweeter circuit. I still theorize that after burn in, replacing the 3.5 ohm resistor with a 2.7 or 2.0 will be the icing on the cake with this mod and I cant wait until another 300 hours of great listening and productive burn in have passed.

I'm focusing attention now to getting more out of my vinyl collection with tweaks and upgrades to my turntables.

Disc Jockey

They're your speakers so you can do what you want with them but I would advise caution with messing around with them too much. Changing that resistor will affect the balance of the speaker. Only you can gauge whether that's beneficial or not but my it probably has a higher value than the 2B because the SRS has two tweeters and needed to be attenuated somewhat.

F1nut

Changing that resistor will affect the balance of the speaker. Only you can gauge whether that's beneficial or not but my it probably has a higher value than the 2B because the SRS has two tweeters and needed to be attenuated somewhat.

Not to mention that they are a progessive point source.

I'm using passages of music with which I'm very familiar and switching from A to B literally in milliseconds

Many, including myself, feel that the quick switch method is not the best way to judge.


Bottom line, you don't have enough time on any of the replacement items to make any sort of judgement as to the sound. Don't take this wrong, but it would have been better to finalize your mods/testing before posting about it.

inspiredsports

I apologize if anything seemed premature, but I did qualify that everything needed to burn in a bit.

I now have about 450 hours on the new 5.8uf cap / RDO198-1 combo and I am smiling ear to ear. I have done both long term listening trying to locate a fatigue point, as well as short burst A/B just to quantify the tonal quality and relative volume differences between the SDA SRS 2 and SDA-2B.

I've swapped IC's, cables and sound sources, and am fortunate to have 2 identical CD players and 4 turntables with different cartridges that I use for comparison. I'm fortunate that my listening room is attached to my my home office so I listen to music for more than 8 hours per day. I'm also extremely fortunate that I've been able to recently obtain "The Clamp" which gives me the ability to listen to extremely accurate source point music from my turntables.

I am extremely pleased with tonal quality of the SDA SRS 2 in direct comparison with the TL'd 2B's and it is essentially identical. However, my initial impression that the volume of treble in relation to midrange/bass is (just very slightly) more laid back has remained. This is definitely not a bad thing, just a very subtle difference in the 2 speaker systems. On a percentage scale comparison of the tweeter performance, using my SDA-2B "TL" as the reference, I rate the SDA SRS 2 "TL" tweeter perfomance about 2 or 3 percentage points behind.

Yes there are 2 tweeters in each cabinet contributing to total HF db output, but I still theorize that the initial 3.5 ohm resistor in the HF circuit (designed to supress the harsher SL2000) is too high for the smoother, better performing RDO198-1. The only way for me to find out for sure is to change it.

Within the next 2 weeks I will carve out the time to drop the 3.5 to a 2.7, an incremental step so as not to move too quickly. I believe the 2.7, or perhaps a future drop to 2.0, will equalize the difference I currently hear comparing the SRS 2 to the 2B.

I do need to state that with no further modification, I now prefer the overall sound coming from the SDA SRS 2's (that was not the case with just the initial crossover rebuild and RDO194-1 phase which left the overall tonality of the highs lacking). In my opinion, the height and width of the soundstage is better due to the higher and wider physical size of the cabinet. The mids are smoother and the bass is more authoritative (but definitely not overpowering), again, due to the larger physical size. The final resistor tweaking is, as someone stated above, my personal quest to match the superior mid/bottom of the TL'd SRS 2 to the (IMHO) slightly superior tweeter output of the TL'd 2B.

ben62670

Thanks for the right up. Glad to hear you are enjoying the tunes:)

inspiredsports

Thanks Ben. I forgot to mention to mention the final tweak on my list that I made was in upgrading my Blade / Blade SDA Interconnect Cables after we talked a week or so ago. I removed the male Blade / Blade connectors from the aftermarket cable I purchased from Polk (new ones are availble here: http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=248760&).

I found 50 feet of mil-spec 12 gauge (19 strand) silver plated oxygen free copper wire with kapton / teflon insulation on eBay, enough to construct better quality cables for both of my sets of Polks for about 60 cents per foot (plus $5 per end for the new male Blade / Blade connectors).

A soundstage improvement was noticed immediately, I think due to the much heavier gauge, and I believe it will even improve more over time as the silver/copper wire seasons a bit.

I may decide to replace the Blade / Blade connections with Cardas female connections in the cabinets and decent bananas on the wire in the future, but am not educated enough yet in this area to know if that additional $100 investment will yield a big bang for the buck improvement in the SDA circuit.

inspiredsports

6 MONTH UPDATE; My SDA SRS "2.1TL's" at approximately 2,000 listening hours

You might recall I upgraded the crossovers in January (2009) using the original Polk specified 4.4 bypass capacitor value and 4 new RDO194-1's. The sound quality was clearly much better than stock after 400 hours, but in comparison to my recently modded SDA-2B TL's, the sound from the SDA SRS 2 RDO194-1 tweeters left me wanting.

I was unhappy with the sound and on February 23rd, I went on a mission to learn how to integrate the RDO198-1 into the SDA SRS 2.

By late February I'd found an obscure tidbit of information published by Matt (Polk) indicating the RDO198-1 could be introduced into the SDA 1B (exact same crossover part numbers) by replacing the 4.4 bypass cap with a 5.8.

In early March I replaced the 4.4 cap with a 5.8 and replaced the top tweeter in each cabinet with an RDO198-1. Within a day or two I replaced the remaining RDO194-1 tweeter in each cabinet with the RDO198-1 (with just the top tweeter upgraded to a 198, the sound was improved, but also presented itself as just a bit unfocused or "phasey".

The sound quality was extremely improved when all 4 RDO198-1's were in place. The tweeter output was not quite as loud in relation to mid and bass as my SDA-2B's, but very, very close. I gave serious thought to changing out the 3.5 ohm contouring resistor in the high frequency circuit path with a 2.7 or even 2.0, the theory being that would squeeze out a tad more tweeter output.

I'm sure glad I took F1, GV#27 and Disc Jockey's collective comments to heart, and stopped and took some time to "smell the roses." Being patient turned out fo be a very good thing as the tweeter sound quality AND output continued to improve with time.

My SDA SRS 2.1's remain as they were on 03/03/2009 (crossover photo bottom of post #119) where the only change from original value was to replace the factory valued 4.4 cap with a 5.8 to allow for the use of 2 RDO198-1's per cabinet.

In March (after reflecting on Jesse's hint in post #131) I did a lot of searching and reading about progressive point source tweeter array theory. I decide to leave the 3.5 ohm resistor as it was.

So now, thousands of hours later, I have to share that the sound is simply exquisite.

I should warn that taking the speakers to a much higher level also opened up the Pandora's box of exposing other weaknesses in my system. the subsequent upgrades in cabling, turntable/cartridge improvements and the introduction of some tube components have yield even astounding payoffs in terms of my listening enjoyment!

Has anyone else made the leap from SDA SRS 2 to SDA SRS "2.1TL" ???

After 6 months, I firmly stand by my opinion that the SDA SRS 2 (SDA-1B also) is an ABSOLUTELY PERFECT CANDIDATE for the "TL" modification.

F1nut

Thanks for the detailed update on your pioneering mod. Good stuff.

ben62670

Thanks for sharing. I like to see Polkies getting into non supported mods. I don't encourage most people to do unsupported mods, but someone with patience, willing to dig a little deeper, and accept failure to reach for that little more is very gratifying. It was also nice to see you take your time to really let things settle in. I used to jump the gun way too quick with mods being good or bad, but guys like Joe, and Jesse have pounded into me that it takes time before you can say it's a success or not.
Thanks guys.
Ben

inspiredsports

Thanks gents,

I couldn't accomplish any of this without the great information and support I get here in CP, as well as mentoring and a little reigning in when I want to go nuts and have next months tweak ready to go yesterday!

Systems

Congrats on the sucessful outcome of your mods.

inspiredsports

GV#27 wrote: »

Congrats on the sucessful outcome of your mods.

Thanks again GV, it honestly wouldn't have happened without you!

inspiredsports

I've been keeping up with thsmith's "SDA-1C Crossover upgrade - Journey Begins" (http://www.polkaudio.com/forums/showthread.php?t=89067) and noted one detail that was skipped when my SDA SRS 2 crossovers were upgraded.

My polyswitches were removed and the gaps directly bridged with snipped off lengths of the leads of the Sonicaps used (meaning no .5 ohm resistors were inserted to replace the assumed resistance of the polyswitches).

Remembering that I tweaked the mod to accomodate RDO198-1's, and at first thought the tweeters were a bit understated (compared to my TL'd SDA-2B's), less resistance in the contouring path should be a good thing.

What prompted this post was the euphoria H9 shared in thsmiths thread in post #36 post about the synergy/sound of his system. I share that euphoria with my SDA SRS 2's as I think they sound as good as any Polks I've ever heard. . .

. . . but, I honestly don't know enough about the circuitry to know for sure what that slight overall difference in resistance is doing. Maybe they can sound even better.

Am I right that failing to account for the resistance of the polyswitch would allow a tad more volume from the tweeters in relation to the lower frequencies?

Direct link to the crossover schematic is: http://www.polkaudio.com/forums/attachment.php?attachmentid=26690&d=1186346454

Post #135 above (image) shows cap value difference (5.8uf instead 4.4uf). I guess the 3.5uf resistor should have been a 4.0?

F1nut

Am I right that failing to account for the resistance of the polyswitch would allow a tad more volume from the tweeters in relation to the lower frequencies?

That would be correct. Remember that new tweeters need to burn in for at least 48 hours as they do sound hollow or a bit understated as you noted right out of the box.

MillerLiteScott

Does the lower tweeter utilize the 5.8 uF cap or just the top Tweeter? If so.. Why?

Scott

inspiredsports

MillerLiteScott wrote: »

Does the lower tweeter utilize the 5.8 uF cap or just the top Tweeter? If so.. Why?

Scott

Hi Scott,

The image in my post #135 above shows the schematic summing up the mod in its entirety, with the exception that technically, the deletion of the .5 ohm rated poly-switch should cause you to compensate by replacing the 3.5 ohm resistor with a 4.0 ohm resistor.

I absolutely love the way mine sound based upon 6-1/2 months of up to 8 hours per day of listening with the 3.5. Note that in my opinion, in direct comparison to my TL'd SDA-2B's that use the same 5.8uf cap to upgrade to the RDO198-1, the SDA SRS 2's sound a tiny bit more laid back, and the 4.0 would suppress them even a bit more.

The SDA SRS 2 is a "progressive point source" tweeter array where the crossover points of the tweeters are staggered in an effort to maintain better high frequency dispersion (versus single point source designs). This crossover design allows different amounts of sound to be produced by the tweeters, depending upon the frequency involved (I think). The volume from the top tweeter always seems to exceed what is produced by the bottom.

Your Answer: The 5.8uf cap sets the high pass circuit to interact properly with both RDO198-1's which are a different impedance tweeter than the RDO194-1's. The 2.7 ohm resistor and .4 microhenry inductor in the path to the bottom tweeter properly roll off the frequencies that reach the bottom tweeter as designed, and no further modification is needed.

All of this was based upon the multi-post/multi-week discussion that followed post #52 containing a quote from Matt Polk about the SDA-1B. I noticed the crossover schematics for the SDA-1B and SDA SRS 2 were identical and posited the mod would work. Let me assure you, it does!

Greg

Systems

inspiredsports wrote: »

Your Answer: The 5.8uf cap sets the high pass circuit to interact properly with both RDO198-1's which are a different impedance tweeter than the RDO194-1's. The 2.7 ohm resistor and .4 microhenry inductor in the path to the bottom tweeter properly roll off the frequencies that reach the bottom tweeter as designed....

Yes the 5.8uf paralleled to the 2.7 ohm resistor provides lift to the very top octave of the top tweeters response only.Whereas the .4mh coil in series with the bottom tweet attenuates it's top end thus narrowing its bandwidth.

xsmi

So taking Drew's order from an earlier post,

Lows:
2 Dayton DMPC 100uF
2 Dayton DMPC 90uF
4 Dayton DMPC 33uF

Highs:
6 Mills resistors 2.7 ohm
2 Mills 3.5 ohm
2 Sonicaps 4.4uF
2 12uF

It would change to this?

Lows:
2 Dayton DMPC 100uF
2 Dayton DMPC 90uF
4 Dayton DMPC 33uF

Highs:
6 Mills resistors 2.7 ohm
2 Mills 4 ohm
2 Sonicaps 5.8uF
2 12uF

Xavier

inspiredsports

xsmi wrote: »

So taking Drew's order from an earlier post,

Lows:
2 Dayton DMPC 100uF
2 Dayton DMPC 90uF
4 Dayton DMPC 33uF

Highs:
6 Mills resistors 2.7 ohm
2 Mills 3.5 ohm
2 Sonicaps 4.4uF
2 12uF

It would change to this?

Lows:
2 Dayton DMPC 100uF
2 Dayton DMPC 90uF
4 Dayton DMPC 33uF

Highs:
6 Mills resistors 2.7 ohm
2 Mills 4 ohm
2 Sonicaps 5.8uF
2 12uF

Xavier

This is correct, my diagram in post #139 did not take into account the .5 ohm resistance of the removed poly-switch.

Naturally, allowable percentage tolerances come into play, so you could argue 3.5 is still OK if the removal of the .5 ohm poly-switch is not accounted for.

The 3.5 ohm resistor attenuates the circuit to a lesser degree, allowing the tweeters to produce a tiny bit more volume than if a 4.0 ohm was used (or poly left in place).

After experimenting, in my specific system, the 3.5 with poly-switch removed is the better solution.

#############################################################
--- Post #50 contains images of my high pass crossovers BEFORE MODS, and post #119 AFTER MODS.
--- Post #1 shows BEFORE MOD images, and post #30 show AFTER MOD images of my low-pass crossovers. I used a mix of Sonicaps and Aexon's for the bottom.
#############################################################

Big Dawg

Hey, I'm ordering my crossover upgrade parts. Is there any reason I shouldn't use 2 parallel 91uF Axon caps in each crossover instead of the Dayton 100uF + 90uF? Is there a preference in quality? I think that the Axon's are made by Solen?

Here's the link to the schenmatic:

http://www.polkaudio.com/forums/attachment.php?attachmentid=26690&d=1186346454

Face

How about 2 100uf Axon or Dayton caps? FYI, SCR makes Solen and Axon, among a few other brands.

Big Dawg

Thanks Mike, I thought I might be able to count on you.

Sonic Craft (Jeff) suggested Axon 82 & 100 (schematic calls for 130+55=185), which will cost a little over $50 per speaker.

Parts Connection has the 91 for $15 each, so $30/speaker

Face

Ok, I thought it said 130+55, I think it's time for some glasses.

I would use two 90/91's, it's better to split the values in half than use uneven values.

Vraad

just got done making SRS "2.1TL" and they sound SWEET, thanks inspiredsports for doing all the research

inspiredsports

Vraad wrote: »

just got done making SRS "2.1TL" and they sound SWEET, thanks inspiredsports for doing all the research

Super! Remember to give them a chance to season a bit; it takes almost one hundred hours for the RDO's to open up and maybe three times longer for the Sonicaps.

What kind of gear are you driving them with, and were you using other Polk speakers before?

Vraad

driving them with a Yamaha m-70 into a Toshiba c-15 pre, had a pair of model 10's before which are now on garage duty. was trying to get a moscode amp and Yamaha c-2x pre, but I need funds other places now. oh and man do they sound sweet