SDA1-C crossover mod

Zen Dragon

I had been re-reading some old posts on crossover mods on the SDA’s and it seemed to fit the bill for the next task I wanted to undertake on my SDA-1C’s. I did a lot of research on capacitors, and who sells what, and who likes what, and why this one is better than that one. I noticed many of the forum members like the Solen caps for their mods. So I purchased all the Solen capacitors necessary for the mod.
On some other forums I encountered in my subsequent research I saw a few posts from people who had the opinion that Solens can sometimes be a bit bright. Now of course everyone has an opinion that’s true, and I have not had the experience of listening to different caps in systems, but now I got this bright word gnawing at my brain. Through further reading in and out of the Polk forums I see a lot of good things on the Sonicaps including a reasonable source for them. The Sonicap Gen I has many good reviews at a reasonable price point. Hmm… http://www.soniccraft.com/sonicaps.htm
http://www.10audio.com/sonicap_oimp_multicap.htm
They are a little on the pricy side for sure, but not the most expensive by any stretch. They look like a great price vs performance capacitor. Looking at the SDA-1C schematics I see only the 4.3uf and 12uf are directly in the signal path, and in the tweeter circuits, which is where brightness would occur. I decide to order Sonicaps for these circuits and use them there, but stay with the Solens at 20 and 40uf (39uf used) in the mid and mid SDA circuit to keep costs down. Brightness should not be an issue in the mid crossover circuits.
Now the pesky 12uf has another issue. Polk has done a bypass with the 750pf silver mica cap. My best guess is the engineers used it as a bypass to improve transient frequency response at that point. There are several articles/opinions out there on bypassing capacitors to improve tonal quality or transient response. Some are for and some against. The ones that are against it make a valid electrical argument.
Bypassing was done on a lot of older gear because very high-end capacitors were quite expensive. The Mfr would often go with low or mid grade capacitors, and place a smaller value (cheaper than the big ones) higher-end capacitor in parallel (bypassing). The higher end cap has much better response than the low/mid grade main capacitor. It reacts much faster to subtle and fast changes in the music allowing the capture of quick details, or high frequency harmonics in the music. Thus the main capacitor passes the primary high frequency music, and quick high frequency information that it may have missed due to a slower response is passed by the smaller value, higher quality capacitor. There is much discussion across the net on bypassing to improve high frequency response. There is a fair amount of controversy on the subject. Imagine that…audiophiles disagreeing.
It sounds good in theory, but the problem that can occur is the faster response capacitor has a faster time constant. This can cause portions of the high frequency signal to arrive on the other side of the paralleled capacitors slightly ahead of other portions, in effect widening or smearing the higher frequency information on the other side as the entire signal does not arrive at exactly the same time. We are only talking milliseconds perhaps in difference here. There is of course more discussion on how audible this waveform smearing is. There are even high-end cap mfrs who now recommend against the bypass practice in the signal path. For example http://www.audience-av.com/auricap_application_notes.htm
This would explain why the 750pf cap Polk used has such a wide tolerance. At .00075uf bypassing 12uf, its contribution to the overall capacitance of the circuit is negligible. It appears to exist purely to pass some of the faster high frequency response the slower cap may have missed. As such its absolute value is not critical. After much research and much contemplation I have decided to try completely removing the 750pf silver mica bypass capacitor from the tweeter circuit. I will trust the higher end 12uf Sonicap capacitor to pass the high frequencies and transients that the lower quality 12uf stock capacitor needed bypass help with. In the event there is a serious degradation of the sound (which I doubt) I can always reinstall the silver mica.
I decided to leave the resistors stock as I do not want to risk too much change to the high frequency sound at this time. I believe the caps will have more bang for the buck anyway. I’ve also decided on a mid grade upgrade the binding posts.

Zen Dragon

Here are some pics
A pic of all parts used
Another pic of the Solens next to the same size Sonicaps
Pre and post crossover pics
New binding posts

dbnh

Nice, informative post. Looking forward to reading additional comments about your upgrade experience.

Dennis Gardner

Nice work! That before and after photo reminds me alot of Barry Bonds.:D

Zen Dragon

I did this mod about a week or so ago on one speaker only, and have been playing the system a lot to accomplish any break-in necessary on the new capacitors. Immediately following the mod I did a brief comparison with a couple CD’s.
First I played the system for my girlfriend simply rotating the balance controls from one to the other. She is not an audiophile, but has been involved with a few bands over her life playing bongo drums and things of the sort. She immediately said the modded speaker had clearer and brighter upper midrange, but the un-modded speaker sounded warmer. I tended to agree with her opinion, but was not ready to evaluate the sound.
I played the speakers frequently over the next week with movies, TV, and CD’s.
Over the last 2 days I have done some more critical listening comparison and here is my perceptions. First off let me describe the unusual methods I used to listen. I took my CD player and only the right channel output. I put this into an RCA splitter and sent the right channel to both inputs of my pre-amp. Now obviously I have no stereo output, but I am sure the exact same audio info is going to each speaker. I removed the SDA cable from the 1-C’s. There were 3 or 4 configurations I listened to the speakers in.
I listened with both speakers 6 inches off the wall and 6 feet apart sitting about 6-8 feet out from center. I played the same song passages over as I listened to first one, then the other speaker. I also listened with both speakers on to see if I could identify stronger sounds from either speaker.
I also listened squatted down about 2 feet in front of each speaker individually to the same song passages.
Finally I set the 2 speakers facing each other about 4 feet apart and squatted between them. I turned the balance to one and then the other, and also listened to both. Sort of like a 4 foot pair of headphones.
For source material I chose various selections of the following CD’s
Bela Fleck – Flight of the Cosmic Hippo
Yes – Fragile
Frank Zappa – Joes Garage
Cusco – Water Stories
Steely Dan – Aja
Diana Krall – The Girl in the Other Room

Here are my thoughts. First off the biggest difference completely surprised me. It is the very bottom end. There is some bass on the Bela Fleck album that best showed this off on the title track. They are not quick notes but prolonged deeeeep growling in your intestines notes. The modded speaker sounded noticeably fuller and seemed to reach down to deeper octaves. You could here and feel it was deeper. This pattern repeated on all music with deep bass.
Now I know the mid circuits saw the greatest quality upgrade in capacitors going from cheap electrolytic to the Solens, but the manner in which the caps are used in that circuit, and Polks decision to go with cheap caps certainly made it appear that they would have minimum effect on the sound quality.
Certain mids were also a little more rounded with a little more hanging in the air at the end of the note.
The least difference was on the high end where I used the better capacitors. The sound was very nearly identical, perhaps slightly crisper and cleaner on the modded speaker, but slightly warmer on the unmodded speaker. I mean this difference was extremely subtle and required extensive attention to pick up. When set up facing each other with me in the middle like a big pair of headphones I could discern little or no difference between them. Just perfectly timed and matched dual mono sound.
I believe in normal listening I would likely not be able to pick a modded pair from unmodded on the high end.
I heard no discernable degradation from removing the 750pf capacitor, which remains out of the circuit. I a week or so I will do the second speaker and let it break in. I think I will leave the 750pf cap in circuit in the second unit to see if I can hear a difference. I will also see if the deep bass sees the same improvement on the second speaker.

dbnh

I know I've used the 400 hour mark to consider new amps/PCs/ICs pretty fully burnt-in. Don't know how many hours of play time your mods have on them at this point, but I wouldn't be surprised if there were more changes down the road as burn-in time increases.

Happy listening, and please keep posting about your experiences.

Zen Dragon

A couple more pics.

The modded crossover from a diff angle showing the silicon which was used to secure all caps
The old and new posts with cables attached
The old and new posts internal view

schwarcw

Nice work Zen! And an excellent writeup, very detailed and informative.

I did a lot of research like you did before I embarked on crossover mods for my SDA-2's and my SRS-2.3's. I encountered a lot of the same issues you did concerning whether to bypass or not. I also checked out the various capacitor manufacturer's and talked to their tech reps. Jeff Glowacki at Sonicraft was a real nice guy and a great help to me in understanding the whole bypass issue. He recommended that I bypass all the caps in the tweeter circuit. Additionally, the uF values for the capacitors in the tweeter circuit that I ordered were reduced by 0.1 uF in order to maintain the original value specified by Polk. I talked with the rep at the warehouse as advised by Jeff. Since the lower values that I wanted were within the 5% manufacturing tolerance, he pulled the capacitors I wanted and measured each one to get the actual values of the caps. The caps were relabeled to show the actual values. Here is a summary of the original and replacement parts:

Original Polk Replaced With

(2) 4.4 uF (2) 4.3 uF Gen I plus (2) 0.1 uF Gen II (200 volt)
(2) 5.8 uF (2) 5.7 uF Gen I plus (2) 0.1 uF Gen II (200 volt)
(4) 12.0 uF (4) 11.9 uF Gen I plus (2) 0.1 uF Gen II (200 volt)
(2) 20.0 uF (2) 20.0 uF Gen I
(2) 40.0 uF (4) 20.0 uF Gen I (2 in parallel for 1 40 uF)
(2) 6.2 ohm (2) 6.2 ohm MRA-5 Mills
(2) 22.5 ohm (2) 22.0 ohm MRA-5 Mills
(4) 33 ohm (4) 33 ohm MRA-5 Mills

Jeff also recommended that I eliminate the polyswitches. I used a 14 ga. copper solid copper wire for a jumper. I immediately noticed more defined mid-range and bass, the tweeters were not nearly as harsh and the SDA definition was much more pronounced, maybe almost 180 degrees of sound in certain musical passages. I wouldn’t say the change was dramatic, but it wasn’t subtle either. It was immediately noticeable.

You should allow about 100 hours or more for the burn in time. Pictures of my crossover mod on the 2.3 can be found here:

http://www.polkaudio.com/forums/showthread.php?t=35837

Zen Dragon

Thanx for the input Carl. I have some questions for you.
I originally leaned heavily towards bypassing with the Sonicap Gen II's. I ultimately encounterred enough opinions at an engineering level and from high end cap mfrs that recommended against the practice due to the potential smearing from different time constants.
So, any chance you tried just the Gen I's for a while before you bypassed? I would have loved to do a comparison, but didn't want to invest the added time to do so many separate mods I suppose.
As to the poly switches I also spent some time wresting with whether or not to remove them. Due to their placement it is obvious they will have an impact on the sound in some way, although I am surprised to hear they had an impact on the mids and bass. they are directly in line with the tweets no?
I decided against it as I like to listen right on the edge sometimes, and I probably trip my Poly switches an odd 2 or 3 times a year. I never take the volume past 12:00, but so much music is recorded at too hot a level that it is occaisionally enough to trip my relays. I'd rather not fry the tweets, so for safety sake I have foregone the removal of the Polys at least for the time being.
Brian

schwarcw

Hi Brian!

Jeff Glowacki from Sonicraft (the owner) recommended the Gen IIs since I had solid state amplification. If I would have been using a tube preamp or amp, Jeff said he would use the Gen I's. He did say they was definately a difference in the Gen I's vs II's. Are you using tubes?

He also recommended the 0.1 uF bypass cap since the 750 pF as you observed would have a negligible affect.

The polyswitches are directly in the tweeter path. If you are tripping them, you may want to get replacements from Polk. Their newer ones are better than the originals. Do you have the original poly's?

Maybe your tripping them because you play loud. TURN IT DOWN!

I listen at relatively low to mid volume levels most of the time (-30 to -20 dB). I rarely go above -20 dB for music, maybe to -15 dB for movies. How much power are you putting into those SDA-1's?

I'm glad you were satisfied with the outcome. Another Forum member "Stew" used your approach, Sonicaps for the high end and Solen's for the low pass shunts. Let me know if you have any questions, and happy listening!

Carl

F1nut

A comment from a cap freak,

"I didn’t find them (Sonicaps) to mix well with other cap’s – a 50/50 mix with a standard Mundorf M-Cap gave me the funny sensation of listening to two different cap’s at the same time."

Here's the whole article, http://home.versatel.nl/geenius/Cap.html

F1nut

A couple of other comments, I wouldn't recommend using silicone as it's very acidic and will corrode any metal it comes in contact with and you need to seal the back of the binding post plate. The best thing to use for both is hot glue. If you haven't already, install the replacement tweeters, major improvement.

About your testing method, without the SDA cable connected, you're only driving half of the mid-drivers, not an accurate way to test, IMO.

Edit: I forgot to mention.....change those resistors, they're only $2.15 each and will make a difference.

george daniel

In my best Austin Powers voice,,,Mills Baby,,,Mills,,,BTW,,nice job on those x- overs:)

Zen Dragon

schwarcw wrote:

Hi Brian!

Jeff Glowacki from Sonicraft (the owner) recommended the Gen IIs since I had solid state amplification. If I would have been using a tube preamp or amp, Jeff said he would use the Gen I's. He did say they was definately a difference in the Gen I's vs II's. Are you using tubes?

The polyswitches are directly in the tweeter path. If you are tripping them, you may want to get replacements from Polk. Their newer ones are better than the originals. Do you have the original poly's?

Maybe your tripping them because you play loud. TURN IT DOWN!
How much power are you putting into those SDA-1's?

Carl

I am not using tubes. I am of the beauty over accuracy school of thought in audio. I am willing to consider the fact that if a bypass is creating a mild "smear" of the high frequency waveform, that the result as heard by the human ear may be warmth over brightness.
I have a Yamaha RX-V795A AVR. Pre-outs to a B&K EX-442 Sonata 200WPC 8 ohm 300WPC 4 ohm. Yes I know the Yammy contributes to my brightness.

I have the new Polys. I am tripping them because I play it loud! For me there are 3 listening levels.
- about 8 or 9:00 because I just want to listen to some music
- about 9:30-10:30 because I want to listen to some music loud
- 11:00-12:00 because I want to experience and be enveloped by some music

Brian

Zen Dragon

F1nut wrote:

A couple of other comments, I wouldn't recommend using silicone as it's very acidic and will corrode any metal it comes in contact with and you need to seal the back of the binding post plate. The best thing to use for both is hot glue. If you haven't already, install the replacement tweeters, major improvement.

About your testing method, without the SDA cable connected, you're only driving half of the mid-drivers, not an accurate way to test, IMO.

Edit: I forgot to mention.....change those resistors, they're only $2.15 each and will make a difference.

F1 thanx for the input. I did not know about the corrosive nature of silicon. I did use around binding posts, but I think the plastic washes are against it.

Did not test with the cable on as I would be receiving SDA correction info from the unmodded speaker on original crossover.

I have wonderred about the replacement tweeters. Isn't it like a +3DB spike in the high frequency. I wonder has anyone ever tried to put a tuned notch filter in to quell the resonant frequency?

george daniel

I'm running a belles 350a ref,to power my 1C's,(rebuilt x-overs,new poly's),I've had it @ 1-2 o'clock,,and have not tripped them yet,,and it's plenty loud.

F1nut

Did not test with the cable on as I would be receiving SDA correction info from the unmodded speaker on original crossover.

Yes, you will get the signal, but it's running thru the modded crossover.

I have wonderred about the replacement tweeters. Isn't it like a +3DB spike in the high frequency. I wonder has anyone ever tried to put a tuned notch filter in to quell the resonant frequency?

It's a 5dB spike at 12-13kHz, nasty.

Zen Dragon

George, thanx for the input. I believe my problem is the Yamaha pre-out maxes at 2.6V which is too high for amp input. I presently have 6DB RCA audio attenuators at the amp input to knock it down, but not quite enough.
It is my intention to eventually replace the Yamaha unit, liklely with a Denon AVR. Just haven't had the timing and money align on that project yet.

Zen Dragon

F1, I assumed there would be interaction between the modded and unmodded crossover through the SDA cable. I will try giving it a listen with cable on.
BTW, thanx for the excellent read on the caps in the earlier post.

Brian

F1nut

I understand why one would think that, but once the signal reaches the respective crossover, it goes thru that circuit on it's way to the drivers.

You're welcome, it is a good read and one reason I went with Sonicaps.

Zen Dragon

To re-open the bypassing discussion, I originally was going to bypass with Sonicap Gen II's in a cascade type bypass as described in the web page link below from North Creek music. It is an interesting read and was what I had planned before scrapping the bypass plan. Any thoughts?

http://www.northcreekmusic.com/Bypassing.html

F1nut

Sounds like it's worth trying. Let me/us know if you do.

I used a Gen II .1uF bypass in my CRS+'s with the SL2000 replacement tweeter (RD0194-1) and thought the high end was a little soft. I wanted to build the never built SDA SRS 4.1TL, so I added the required cap, changed the tweeters to the RD0198-1 and kept the bypass cap in place. The detail and sparkle came back, I'm very happy with the sound now.

I quess what I'm saying is, you never know until you try it.

schwarcw

Interesting Jesse. I have a pair of original CRS's that I haven't replace tweeters or done any crossover mods. Based on your experience with the 0194's and the 0198's, are you suggesting that the 0198 is a better replacement for the SL2000 in the CRS?

Are you using a tube preamp with the CRS+ setup? Thanks!

Carl

Zen Dragon

I just had a conversation with Jeff Glowacki at Sonic Craft. It was an amazing conversation really. Here he is a business owner, and he was more than happy to spend some 20 odd minutes on the phone discussing capacitors, capacitance, and how and why they do what they do at or near an engineering level. It is obvious where his passions lie.
He also offerred me a refund on the Sonicaps I had purchased based on the fact I did not hear a greatly noticeable improvement. Now I never complained, and I am not looking for a refund, but it still is nice to hear customer service and confidence in a product at that level.
We also discussed the cascade method of bypassing as outlined in the article link a couple posts ago. He is of the considerred opinion that it is an unneccesary expense and would yield little or no audible gain.
He is however an advocate of bypassing in general, and after obtaining all the info from me on what I was working with and what i had done he suggested single bypassing with Sonicap Gen II's. He also said the 20 and 40uf Solens if bypassed would likely yield a result in the high end as they shunt the high frequencies up to the tweeter circuits. He also offerred my money back on them if I go that route and am not satisfied. Again I would not return them in any case, but it was nice to hear again.
He is a friendly, passionate, and knowlegeable resource. I highly recommend his products and his services.
I will likely go with a bypass on the second speaker when I do the install, then compare original mod, vs bypass mod.

schwarcw

He is an amazing guy to talk to. I haven't checked the site lately, but he was talking about his new "Platinum" caps a couple of months ago. He said that he couldn't keep them in stock and was having trouble competing for materials with the Chinese. Tehy were buying in volume he couldn't get the supplier's attention. The Platinum cap is supposed to be very expensive also.

Carl

F1nut

Carl,

What I did can't be done to the original CRS's, so the 0194's are the only way to go. Also, I can't say 100% that my results will be the same for someone else, but I think if one were to use the same caps, etc. that I did, then the results should be the same.

Based on your experience with the 0194's and the 0198's, are you suggesting that the 0198 is a better replacement for the SL2000 in the CRS?

Yes, that is what I'm suggesting, but to use the 0198 in the CRS+'s, you have to install a 5.8uF cap in the high frequency circuit. I'm also using the .1uF Gen II bypass cap and running them off a tube pre and SS amp.

Agree, Jeff is the man. He recommended to me to use the Gen II's. Did he tell you what the differences are between the Gen I and Gen II?

Zen Dragon

F1nut wrote:

Carl,

Agree, Jeff is the man. He recommended to me to use the Gen II's. Did he tell you what the differences are between the Gen I and Gen II?

Did he tell me electrically...no
Based on some articles/info I read on the web, how and what all the Sonicaps are made of is a gaurded secret that Jeff has not shared with any who have inquired so I did not ask. One would assume they are film/foil, but you never can tell. Look at the Auricap. It is firmly seated price and performance wise in the film/foil market, yet it is a polypropylene cap. By all accounts it sounds better than many film/foils.
Sonically he said the Gen II is more colorful than Gen I, with perhaps a mild mid bloom. As I encounterred several times in my research he equated cap bypassing to cooking. You take a dish you really like and add a spice here or there to see if you like the flavor more.
Now purists would cry foul and claim the signal may be being alterred. Perhaps so, but as Jeff points out, as well as some great reading on the North Creek Music site. You start with the formulas and engineering with a computer. You design the perfect enclosure, drivers, and circuits electrically. When all that is done you put it together and give it the ear test. Then the redesigning begins as what is perfect on paper is rarely what the listener finds perfect or appealing.

F1nut

I was informed that they are film/foil, but without ripping one open I have no way to confirm that.

Sonically he said the Gen II is more colorful than Gen I, with perhaps a mild mid bloom.

Thanks for that.

Then the redesigning begins as what is perfect on paper is rarely what the listener finds perfect or appealing.

Words of wisdom!!!

If you haven't found this yet, I think you'll find it interesting.
http://ldsg.snippets.org/appdx-ec.php3#CAPRECS

Zen Dragon

I had come across that in my research thanx. This quote from the page was one of them I rememberred regarding the Sonicaps.

SONICAP is a proprietary design of Sonic Craft. These are "mystery" caps in as much as Sonic Craft has released no details other than available values, voltages and tolerances. Construction details, dielectric, and metals technology information is conspicuously absent from the Sonic Craft web site. Requests for further information are met with replies that the information is a trade secret. Still, I have heard good reports of these. They're hardly cheap, in some cases costing more than AudioCap Theta's. Are they worth it? I don't know. I do know that Sonic Craft's Jeff Glowacki knows capacitors and knows them well - and he designed these.

schwarcw

F1nut wrote:

Did he tell you what the differences are between the Gen I and Gen II?

Jeff told me if I had metal dome tweeters or solid state pre/amp to use the Gen II's. For tube electronics, Gen I's. As Zen stated, Jeff said the Gen II's are a little more "colorful". I used the Gen I's for mid and low caps. When I get around to doing the CRS's, I'll probably go the same route.

Whatever Jeff is using in the caps, the Chinese are buying a lot of it too. He was having trouble getting material earlier this year.

Carl

F1nut

From Sonic Craft's site,

"The Gen I is basically a fairly balanced capacitor. However, some find our "balanced" slightly thin and bright compared to the more lush "colored" capacitors which would include the Gen II. While the Gen II has a nice Midrange bloom, Gen I has a slight advantage on the freq extremes (top and bottom). In many applications, larger values of Gen I bypassed with smaller values of Gen II yield a very favorable result."

As the largest value of the Gen II is .82uF, one is pretty much limited to using them as bypass caps.