SDA 2B Upgrades/Amplifier Questions

[Stew]

I just found this forum while searching for Polk SDA. I've been a Polk fan since I bought a pair of mini-monitors in 1981. Bought my next pair of Polks (Monitor 7's) in 1988 and, after several upgrades, ended up with the SDA 2B's that I still own. I still love listening to my 2B's when I find time (4 kids) and I haven't found anything else that compares (except better SDA's).

I read several threads on upgrades including "SDA 2B Studio Crossover Upgrade" and I'm seriously thinking about the crossover upgrade and RD 0194-1 tweeters. As much as I love my 2B's, the highs sometimes sound a bit harsh and the bass could use a little more punch. Everything I've read here makes me think these upgrades will improve those issues.

My question is whether these upgrades, especially the crossover, will make a profound difference with a Yamaha AX-500U integrated amp (100w/ch with 170w/ch headroom @ 6 ohms). Plenty of volume for my taste and room size but I see a lot of people on this forum running much more expensive amps. A high end amp is not in the budget any time soon and I'm wondering if these upgrades will still make a big difference. If so, would a better amp make a big difference on top of the upgrades? Thanks in advance for the help.

Glad to find this forum. Good to know that SDA fans are still plentiful and that Polk still supports us!

Stewart

[F1nut]

Welcome to the fray.

IMO, the upgrades WILL make a difference that you will notice. Of course, a better amp will make things even better.

[TroyD]

What they grumpy guy said.

BDT

[F1nut]

Hey, I resemble that remark.

[TroyD]

In order:

Tweeters
Amp
Crossovers

That's how I'd attack it.

DDtTTS

[BlueMDPicker]

Hi Stew,

Welcome to the forum.

The tweeter upgrade will provide instantly noticable results. If you have a lot of hours in front of the speakers with the SL2000s, the first impression of the silk domes may be slight disappointment (for lack of a better term) until the new tweets break-in a bit and you become adjusted to the new sound as well.

Crossover upgrades for the 2Bs are relatively inexpensive and will provide you with a tighter, better defined bass (from my experience.)

If a new amp isn't in the cards at the moment, the upgrades to the speakers are still worthwhile IMO.

Enjoy!

Mike

[ckpiv]

Stew,

I have been running a pair of SDA IIB's since the late 80's until a couple of weeks ago when I finally upgraded to SRS 2.3's. In my experience with them, I too found the SL2000's rather harsh so I updated to the RD0194's. Wow - what an improvement! The high's are much more smooth and well defined. You should do this upgrade first. $48 a tweeter for club members will give you instant results.

As for the bass... I went from a Yamaha reciever to a Kyocera Integrated amp to a Parasound amp. with each step the bass improved. The SDA's like high current and will come alive the more you throw at them. You can pick up a nice amp at a reasonable price on ebay or on the flea market thread here. Also the placement of the SDA's are very important as well - I had mine 5.25" from the back wall which gave me a nice tight bass response. Any closer bass got muddy and farther out it would drop off so you need to experiment here. I also found the bass response was also effected by speaker cable selection so you may want to look here as well. The crossover upgrade would be my last resort IMO.

Good luck.

[F1nut]

The crossover upgrade would be my last resort IMO.


That's only because you haven't done it.

[ckpiv]

That is true. I was only giving my opinion in the steps I would take.

[Stew]

Thanks for all the advice. I think I'll go ahead with the tweeters and crossover upgrade. Crossover upgrade is fairly cheap and looks like a fun project. I looked up the parts at partsconnexion.com and current price is just over $50 to do both speakers. The 39 and 12 uF caps are available in either 400 or 630v and the 20 uF cap is only available in 400 v. Is there any advantage/disadvantage to the 400 vs. 630 v?

What about burn in for tweeters and crossover? Should this be done at normal/low/high volume? I've seen 50 hrs mentioned. Does it take that long?

If I decide to upgrade the amp down the road, what should I look for in a reasonably priced used amp? Mine is 100w/ch at 6 ohms with 2.1 db headroom. Volume is plenty in a 15 x 22 foot room but I gather sound quality and bass response would improve. Thanks for suggestions.

[McLoki]

Thanks for all the advice. I think I'll go ahead with the tweeters and crossover upgrade. Crossover upgrade is fairly cheap and looks like a fun project. I looked up the parts at partsconnexion.com and current price is just over $50 to do both speakers. The 39 and 12 uF caps are available in either 400 or 630v and the 20 uF cap is only available in 400 v. Is there any advantage/disadvantage to the 400 vs. 630 v?

Can you send me a link or PM showing what the crossover upgrade is and what it does for you? I also have a pair of SDA 1b's that I purchased new back in about 1987 and am thinking of putting back into service. I definately need the new tweets, but after about 18 years, I am sure the crossovers could use some going over as well.

Thanks,

Michael

[Stew]

Try searching the Vintage Speaker forum for "sda crossover upgrade". More parts/expense to do the 1b's compared to my 2b's. This is all new to me; others on this forum have first hand experience.

[F1nut]

I'm quessing you're going with the Solen caps, right? Just get them all the same, 400V. I prefer Sonicaps, but they are a lot more money. Don't forget to replace the resistor, get the Mills wire-wound 5 watt and replace the silver mica with a 750pF 500V.

[Stew]

Correct, planning on Solen caps. Do I need to replace the silver mica? The "SDA 2B Studio Crossover Upgrade" indicated that this is a high quality component and doesn't need replacing. By the way, www.solen.ca has some of the caps cheaper. Has anyone tried ordering through them?

[F1nut]

Solen caps are cheap enough already! Just get them from PE.

The silver mica caps that Polk used are crap, rated at 1000pF, tolerance of +/- 50%!!! Get the replacements, 750pF, 500V, tolerance of 5% or less.

[Stew]

Solen caps are cheap enough already! Just get them from PE.

The silver mica caps that Polk used are crap, rated at 1000pF, tolerance of +/- 50%!!! Get the replacements, 750pF, 500V, tolerance of 5% or less.

OK, I'm going to ask what may be a dumb question. Why change a 1000 pF cap to a 750 pF? :confused:

[SCompRacer]

OK, I'm going to ask what may be a dumb question. Why change a 1000 pF cap to a 750 pF? :confused:

Have you got a schematic for your speakers? Polk will send you one if you ask for it. 750pf is the spec value.

[SCompRacer]

In reagrds to amps, folks will have their brand preference. I've got SRS 2's in a large open room with 14' ceilings. 200 - 250 WPC @ 8 Ohms (300-350 @ 4) did nicely for me. It will depend on what you can spend too.

[Stew]

Have you got a schematic for your speakers? Polk will send you one if you ask for it. 750pf is the spec value.

Wow, Polk used a cap with a value somewhere between 500 and 1500 pF when the spec value is 750! Don't have a schematic but sounds like I need one. I'll add the 750 pF to the list. Thanks to you and F1nut for the info.

[F1nut]

Hey, I'm not going to steer you wrong.

[Stew]

Parts Connexion carries a 300v +/- 5% miconics silver mica (SMICA- 54432) for a whopping sum of $1.50 ea. Will this do the trick?

[F1nut]

The original was rated at 100V, so that'll be fine.

[Stew]

Just out of curiosity, what's the point of that 750 pF capacitor? 12 uF + 0.00075 uF is still essentially 12 uF. Does it serve some function other than very slightly increasing the capacitance?

Thanks again for all the advice. It's amazing to find this kind of interest and support for 15 year old speakers! It may be a while before I have time to do the upgrades but I'll post how it turned out when I'm done.

[F1nut]

It's a by-pass cap which operates at a different frequency.

[Stew]

It's a by-pass cap which operates at a different frequency.

I did a quick search on bypass capacitors and found the following statement on Auricap's website (http://www.audience-av.com/auricap_application_notes.htm):

"Do not use bypass capacitors in the signal path. A single capacitor for DC blocking/AC coupling creates a simple path with one time constant. The signal quality will be compromised if a bypass or multiple bypass capacitors are added to a signal path capacitor. Bypass capacitors were used in the past to bypass low quality film capacitors or electrolytic capacitors. The bypass was the lesser of two evils. With the advent of better quality film capacitors the need for a bypass capacitor was eliminated. Bypass capacitors create multiple signal paths with multiple time constants. These time constants are very short but they can still be heard as a smear or overall loss of focus."

I don't fully understand this and wondered what some of you think.

[F1nut]

I believe they are talking about power supplies, not crossovers.

The following is taken from an article on the quality of different caps.

"ERO MKP1830 0,01mF MKP 100VDC – 1% tolerance – 5,5x7x7,5mm (a.k.a. Vishay Roederstein MKP1837)
Another part of the crossover of the “Progress” speaker (it’s that very small blue block on the bottom right of the photo).

Technical Specifications: Metallised polypropylene, radial capacitor, designed for LC/RC filter circuits, coupling and decoupling at high frequencies. Very low priced cap.

Sound: I was tipped by Klaus Witte of Germany to try this capacitor as a bypass cap for the Mundorf M-CAP SUPREME. I tried them as a bypass for the tweeter series caps in my Progress speaker and I must say I am very impressed! To get straight to the point they don't change a Supreme into a Supreme Silver-Oil but they really do clear things up. I must admit I was sceptical at first as the value is only 10nF (0,01uF) - and the caps in the Progress are 12,6uF. The difference is most noticeable with classical music but also good quality recordings of jazz and fusion benefit: No change in soundstage width or depth but there is more "concert hall acoustics" that let you get into the recording more. Not as liquid as silver/oil but they take away the "grainy" edge from the Supreme's. A gain in clarity and transparency making instruments better separable from each other, the violins in an orchestra are a group of individual violins instead of one mass. Jazz drum brushes sound more like a brush than a "shush".

[Stew]

I believe they are talking about power supplies, not crossovers.

So that's what they mean by "signal path capacitor." See your point; if bypass caps help Mundorf M-CAP SUPREMEs, they should certainly help Solen Fast Caps. Thanks for the enlightenment and for putting up with all my questions! I'm looking forward to upgrading and hearing my "new" speakers.

[schwarcw]

I have been doing some research on the Forum on this topic since I have a pair of SDA-2s and have been consideing the crossover upgrades. I have upgraded the tweeters with the new silks and I found a nice improvement. I highly recommend doing this with your SDA-2Bs.

My crossover has a 750pF bypass around a 0.5 mF in the tweeter circut of the crossover. I talked with Ken Swauger via email about the by-pass. He mentioned that there is a school of thought that mixing the capacitor types may deter the performance.

I contacted both SonicCraft and Percy Audio. I gave them a schematic of my crossover and the parts I needed and asked for a recommendation. Both Jeff at SonicCraft and Michael Percy said that mixing the silver mica with the film capacitor should be avoided. Ken Swauger suggested that I use aligator clips to install the silver mica bypass and see how it affected the sound.

In Percy's catalog I was looking at the DynamiCaps and Wondercaps and these are metalized polypropylene and film. I was considering using these caps for the 0.5 mF and 750 pF portions on my crossover. The writeup on these caps states that "You may find by-passing is not required with these very transparent capacitors". It also states that "if by-passing DynamiCaps use no more that 1/100 the value of the main capacitor".

I was hoping for some feedback from the Forum. Has anyone used these caps? Do you thing the 0.5 mF and the 750 pF Wondercap is a good match?

[F1nut]

Carl,

The 0.5 is a uF, not mF.

You bring up an interesting question and one that I've been thinking about as well. But, alas I haven't had the time to investigate.

What other caps are you considering to mix with the Wondercaps?

[Stew]

Hmmmm ... What do you think of using a 750 pF metalized polypropylene cap instead of the silver mica to bypass a Solen in the 2B's? The Percy Audio catalog that schwarcw referred to shows a 750pF Wondercap for $5.95. Other than a few extra bucks, would there be any downside to using these or some other 750 pF metalized polypropylene caps?

[F1nut]

Only one way to know for sure, try it with both, then decide which one sounds better.

[schwarcw]

Jesse,

Thanks for your feedback and u vs m correction. Percy recommeded the following:


1) replace the series components to one tweeter with 0.47uF 450V Auricap
@$7.95, 12uF 200V Auricap @$27.95, 3.5 ohm Mills MRA-12 @$3.50, and replace
the 2.7 ohm shunt resistor with a 2.7 ohm Mills MRA-12 @$3.50

2) replace the 12uF to the other tweeter with another 12uF 200V Auricap, and
the 3.5 ohm resistor with another Mills MRA-12, and replace the 2.7 ohm
shunt resistor with a 2.7 ohm Mills MRA-12 @$3.50

3) replace 27uF shunt capacitors on MW6501 drivers with 27uF 250V Axon
metallized polypropylene capacitor @$7.50

[BobMcG]

Carl,

Not that it's a big deal but I'm not sure why Percy is recommending the use of 12v Mills resistors.

Any thoughts Jesse?

[schwarcw]

I'm not sure why they are recommending the 12 Volt resistors. Jeff at SonicCraft recommended the 5 volt. He said in his opinion they would be better.

Both SonicCraft and Percy recommended the higher end 12 uF capacitor. There must be some reason why this capacitor is critical in the crossover circut.

[F1nut]

They better not be recommending any resistors in volts because they are suppose to be rated in watts. The 12 watt resistors will handle more heat, but that's not of any concern here and the 5 watt resistors have less inductance, which is of concern.

My only experience with Auricaps is in a Jolida cdp that I had modded, so I don't know how they would sound in a crossover. Another thing I don't like is mixing caps. Auricap offers values up to 35uF, so I'd stick with them if that's what you go with. Besides that, Auricap is definitely better than Axon.

A little insight on Auricaps from geek site.
"Another perennial high-end favorite, Auricap has stolen a lot of the thunder of the Hovland Musicaps. This isn't too surprising since the two brands are quite similar in many respects. One non-obvious difference that Auricap downplays is that the Auricap is of metallized film rather than Hovland's film and foil construction. Still, many people prefer Auricap's to Hovland's. Values range from 0.01-35.0µF."

[BobMcG]

Sorry Jesse, Had my head on backwards..... meant watts not volts. :o

[F1nut]

Bob, I know you know what they are. My comment was an attempt at a little humor....very little. :)

[schwarcw]

Thanks Jesse! Your always there to give me and many others who are novices in this area good advice. I appreciate it!

I thought the same thing about mixing caps. I was curious that two tech reps suggested the premium cap for the 12 uF capacitor. The Sonic caps are a little (not much!) cheaper than the Auricaps. The real question is whether the additional investment of about $125 is worth it? Will I hear the difference? Which is not a question you can answer for me since so much depends on my listening style, type of equipment that I have and of course the music. But any insight you have is welcome!

[Stew]

I've been reading up a little on bypass capacitors. A little knowledge is probably dangerous but this sums up what I read:
1) typical values are around 0.5 - 1.0 % of the cap bypassed.
2) the exact value isn't critical
3) it's more art than science.
Am I in the ballpark here? If so, what do you think of using something like a 0.01 - 0.1 uF Solen to bypass the 12 uF Solen I plan to use in my SDA 2B's? I wonder why Polk used such a small capacitor (750 pF) to bypass the original 12 uF electrolytic?

[WilliamM2]

3) it's more art than science.

It's not science, and I have never understood why they call them "bypass" capacitors. Nothing is bypassed, the signal still travels through BOTH capacitors. It just adds 750pf capacitance to the circuit.

A friend of mine, an electronics repair technician, did my SDA1C crossovers for me, he was scratching his head when he saw the 750pf, couldn't understand how it would do anything. It changes the capacitance of the 12uf by only .0625%.

By the way, Polk didn't use cheap silver mica's in all the speakers, as mine had a 300v 800pf at 1% tolerance.

I did mine because of the age of the components, and noticed very little difference in the sound. If you are doing it expecting a large sound improvement, I think you will be disapointed.

[Stew]

From what I read, they're suppose to reduce hystersis or hysteretic distortion. I saw a graph somewhere and it basically just smoothed the response. I'm not expecting a huge improvement but if I'm going to do it, I might as well get the most bang for the buck. Kind of an interesting puzzle anyway. I'm expecting a bigger improvement from the tweeters but they already sound really good like they are.

[Stew]

Oops, make that Hysteresis not Hystersis.

[WilliamM2]

You will notice a great improvement with the new tweeters. I used to think the old ones sounded great, until one of the old ones failed. After installing 4 of the new tweets, I am glad that tweeter failed!

It was enough to re-kindle my fading interest in audio, and I have now upgraded everything but the SDA1C's and the Denon POA-2400 power amp that drives them.

[F1nut]

Schwarcw, you're right. I can't tell you if you'll hear a different between the two brands, but I would think you could. They are very different designs. From what I've seen the Auricaps are used more in electronic components than crossovers. Personally, I'd go with the Sonicaps..never read a bad word about them.

Stew, Bypass caps in crossovers are used to add detail by reducing hystersis and improving transient response at certain high frequencies depending on the value used. So, they do actually bypass and the value is more critical than not. I'd stick with the value spec'd by Polk.

William, Any good tech should know that bypass caps are used on power supply boards and crossover boards all the time. What caps did your tech friend use and did he replace the resistor(s) too? I believe that the level of improvement is dependent on the caps used and the level of associated gear.

[WilliamM2]

We used Solen PB's, the 1% Silver mica's from Handmade, and Mills 5W resistors.

He is a phenomenal electronics tech, but he does not work in the audio field, I had him do the job because his soldering skills are better than anyone I have ever seen, definetly better than mine.

And he knows bypass caps are used in many electronic circuits and power supplies to bypass other components, they are not usually used to bypass other caps. As I stated above, the current will flow through both caps at all times, therefore nothing is really bypassed. If it did, then the 1uf I paralleled to the 39uf would bypass the 39uf, but it doesn't, it just changes the value to 40uf.

[F1nut]

"The Art of Bypassing

Bypassing capacitors is a little like blending watercolors. With watercolors, the dominant pigment can be brightened, softened, darkened or lightened with small additions of other hues, and it takes a delicate touch to make the perfect shade.

With capacitors, the signature of the base cap can be brightened, softened, darkened or lightened with the addition of the appropriate choice of bypass capacitor. The "perfect" tonal balance can only be determined by ear.

And, like watercolors, the whole is often greater than the sum of its parts.
The bypass capacitors we have developed have very specific subjective characteristics that can be applied to improve the performance of most loudspeaker crossover capacitors significantly."

As I stated, "Bypass caps in crossovers are used to add detail by reducing hystersis and improving transient response at certain high frequencies depending on the value used. So, they do actually bypass and the value is more critical than not."

They don't mearly change the value, they change the tone at a certain frequency, hence the term "bypass."


You should have noticed an improvement in detail and clarity. Since you didn't I wonder if it's somehow gear related.

[WilliamM2]

The entire signal, ALL frequencies will go into both caps. Elecrons are stupid, they don't know which cap they are supposed to pass through. Please explain how one cap bypasses the other when the current goes through both, don't quote websites selling bypass caps (Northcreek) as I would imagine their desire to sell bypass caps might make them a little biased. I read that site a couple of months ago, and I didn't see any measurements to back up their theories.

And I didn't say that I didn't notice an improvement in clarity or detail (Didn't we already have this discussion?), I said it was very slight.

[WilliamM2]

Here is an interesting quote I found on the web:

Do bypass capacitors work?
Maybe. A bypass cap is a very small value high quality cap people put next to a cheap cap on the crossovers to improve the sound of a speaker. The theory is that good electrons going through the bypass cap are somehow going to clean up the bad electrons going through the cheap cap. Some people swear by them. Our theory is that electrons are pretty stupid and any tweak that requires electrons to have intelligence is faulty to begin with. Try it and see if you can hear the difference. A better bet would be to replace the cheap cap with a good cap.

[F1nut]

You said, ".....noticed very little difference in the sound. If you are doing it expecting a large sound improvement, I think you will be disapointed."

This has not been my experience or that of a good number of other folks I know. Hence, my comment that it may be gear related in your case.

You're nit picking over the use of the term bypass and you don't seem to be getting why that term is used by the entire industry. No one here said that one cap totally bypasses the other. I posted the quote from North Creek to try and help you understand it. Since you haven't got it yet, they are used in crossovers to TWEAK the sound (tone) and can be of benefit even when used with "good" caps.

Did your tech leave the silver mica out of your crossover when he upgraded the caps to "good" ones? No, sure doesn't look that way to me. You might want to have him remove them and see if you can tell the difference. I'd be curious to hear what you find.

[WilliamM2]

Why would he leave the mica out? I already had the parts, and he swapped ALL the parts as I requested. He also thought adding the .1uf to the 4.3uf wasn't really needed, he still did it, only takes him a second.


This has not been my experience or that of a good number of other folks I know. Hence, my comment that it may be gear related in your case.

The old "Your gear isn't good enough to hear it". My gear is fine.

Doing an A/B comparison without the cap would be interesting, but the time it takes to switch component in and out would make it pointless. If I had two pair it would be easier to do an A/B comparison.

[SCompRacer]

I've read that 'bypass' caps are used in tweeter crossover circuits to reduce hystersis distortion in the mid and high frequency ranges. It is said to 'sometimes' make an audible difference regardless of the quality of the cap it is bypassing. Since there are camps on both sides of the issue, it appears the only way to find out is try it.

[Stew]

I'd stick with the value spec'd by Polk.

F1nut - Wouldn't the value/type of bypass cap be dependent on the base cap? Polk chose a 750 pF silver mica to bypass a 12 uF electrolytic. It seems like the new bypass should be chosen to work with the new base cap (i.e. 12 uF metallized polypropylene Solen). Thoughts?

[F1nut]

See below.

[F1nut]

Ok, you guys got me curious, so after a lengthy conversation with Jeff at Sonic Craft here's what we've come up with. Replace the silver mica with a 0.1uF 200V Gen II Sonicap (if you're using Sonicaps for the entire crossover) and stick with the 5 watt Mills resistor. The only advantage to the 12 watt resistor would be if you had metal dome or horn tweeters. I've just ordered some 0.1uF caps and will report my finding asap.

[schwarcw]

Jeff basically told me the same last week. Although he didn't think the .1 uF capacitor would add anything. He also suggested that I jump the tweeter fuses. He said basically "so many people are buying expensive interconnects and speaker wires and you could probably see high frequency improvement by jumping that fuse that has a hair size wire." I said what about protecting the tweeters? He responded "How many times how you blown a tweeter fuse?" Good point, I've never blown one.

Anyone else jumping their fuses?

[F1nut]

Yep, I got schooled by the master today and it was really cool. :D When you stop learning, you're dead.

Raife bypassed the polyswitches in at least one set of his big SDA's with no reported problems. While I've never tripped mine, I'm leaving them intact just in case.

[SCompRacer]

While I've never tripped mine, I'm leaving them intact just in case.

I found I can trip mine (they are the replacement polyswitches) with one track off the Brothers In Arms CD. About 1:40 into Money For Nothing, that screaming note before the great rift. At 10:30 on the gain knob. Thats hearing loss area with sustained listening of course. Anything below is fine. Ken seems to think its a frequency thing cause it sure sounds good. Ask Norm. :D

[Normanality]

I found I can trip mine (they are the replacement polyswitches) with one track off the Brothers In Arms CD. About 1:40 into Money For Nothing, that screaming note before the great rift. At 10:30 on the gain knob. Thats hearing loss area with sustained listening of course. Anything below is fine. Ken seems to think its a frequency thing cause it sure sounds good. Ask Norm. :D

Amen Brother!

That is the most incredible audio I've heard. Them speakers are singing!

Better than front row seats at the concert! :cool:

[Stew]

I emailed Jeff at SonicCraft and got a similar response on the bypass caps. He suggested a Sonicap Gen II 0.1uF/200V to bypass the Sonicap 12 uF but said a Sonicap bypass would help very little wih the Solens. He also said that Solens in the Low Pass (20uF and 40uF) would suffice as the shunt circuit of a LP is much less critical. He said there would be an audible difference with the LP Sonicaps but no added disadvantage to mixing them. I'm think I'll use the 12 uF Sonicap with 0.1 uF bypass depending on what kind of results F1nut reports. I'm still debating whether I want to use Solens or Sonicaps for the LP. Is it worth an extra $125?

[Stew]

I think I found the article that F1nut referred to earlier (http://www.home.zonnet.nl/geenius/Cap.html). It states, "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." When they say 50/50 mix, do they mean Sonicaps in the High Pass and Mundorfs in the Low Pass? Has anyone tried using Sonicaps in the High Pass and Solens in the Low Pass?

[Kenneth Swauger]

Hello,
Remember, audio signals don't pass through any capacitor; they are not conductors, not even semi-conductors. That's why they don't have a current rating, only a working Voltage rating. Current never flows through them, they are storage devices. Two conducting plates separated by an insulating material that prevents any current charge from flowing; in fact if the capacitor is damaged it then becomes a conductor because the insulating material is no longer doing what it's supposed to.
Regards, Ken

[Kenneth Swauger]

Hello,
I believe there was a recent article in Audio Xpress about how to measure the characteristics of groups of parallel capacitors and judge which ones to place together. If anyone's interested I can research the article and send copies?
Let me know, Ken

[F1nut]

Yes please.

[DAGLJAM6]

Also, Yes please the info would be much appreciated.

[WilliamM2]

Remember, audio signals don't pass through any capacitor; they are not conductors, not even semi-conductors. That's why they don't have a current rating, only a working Voltage rating. Current never flows through them, they are storage devices.

Current never flows through them?

While capacitors are not conductors, current DOES pass through them. Capacitors store electrical energy and block the flow of direct current while passing alternating current. The audio signal is AC, and it does pass through the capacitor in the tweeter circuit.

As frequency increases, dynamic resistance of the capacitor (capacitive reactance=Xc) decreases, alowing more current to flow through the capacitor. As you know, the value of the cap determines which frequencies pass.

If you want an example, here is a simple circuit you can build to test it. If the light bulb lights, current is passing through the capacitor.

[schwarcw]

I think I rember reading on this forum that Bose or someone puts light bulbs in there speakers to bleed excessive wattage

[WilliamM2]

I read that too, but that's not a crossover, just a simple circuit to show that current (or audio signal) does pass through caps.

[Stew]

Ken, I would appreciate a copy of that article too.

Thanks,
Stew

[schwarcw]

Lots of good info and discussion. Thanks WilliamM2 and F1 for all the discussion. I was leaning towards buying the Sonicaps for my 12uF and 27 uF capacitors. I was considering getting the Dynamicap 0.47 uF, and 750 pF Wondercaps. But, as F1 and Stew pointed out mixing the cap Manufacturer could be a problem. I'm pretty convinced to go with the Sonicaps all the way around. The only question is whether to use the 0.1 uF in parallel with the 12 uF. It looks like more info is coming. This would be a more economical alternative for me. The Dynamicaps are $15.95 each (ouch) the 750 pF Wondercaps are $5.95 each. I would need 2 of the 0.47s and 6 of the 750 pFs. Using Sonicaps all around would be over $200 total for all components. But I thinks my SDAs are worth it. Love the sound!! Of course after I get this upgrade done, a pair of SRSs will come available for pickup in or around Western PA. Then, I have to do it all again!

[F1nut]

From a site I found some time ago and had forgotten about....

"When you purchase any kit, ask what kind of components are used. "No Compromise" crossover components can mean many things. It might mean good design. It might mean good/better/outstanding component quality. Most likely the components will be of the Bennec/Solen/Axon variety. These are fine, but there is better stuff. If you equipment is decent, and your ears are decent, you will notice an improvement directly proportional to the void in your wallet. I highly recommend the AudioCap products from Jeff Glowacki at Sonic Craft.

There are only a few people who can speak intelligibly about the guts of a capacitor and explain them. Jeff Glowacki is one of these people. I have tested Jeff's voodoo magic and found that it really does hold water. His components are very good. His site, like mine, is void of hoopla about this or that. His stuff is good, his words are true. Jeff told me that he listened/tested everything and decided on Audio Cap because it is the best in its class. I highly encourage anyone interested in getting a better capacitor to call Jeff Glowacki. He can address any form of question concerning this issue.

I recently performed an a/b comparison with an AuriCap and Sonicap behind my OW1 tweeters. I learned why the AuriCap indeed has a very solid following. It's a good capacitor. It has a nice lush midrange, but lacks some detail compared to the Sonicap. Overall, I found these two capacitors very good, and equal in quality. If they were the same price, the implementation decision would be a toss-up. However, the Sonicap is less expensive and the same quality - IMO. I'll keep using the Sonicap."

[Kenneth Swauger]

Hello,
This might help understand how capacitors work:
http://amasci.com/emotor/cap1.html
Ken

[Kenneth Swauger]

Hello,
Here's another:
http://www.allaboutcircuits.com/vol_1/chpt_13/1.html
Enjoy, Ken!

[WilliamM2]

Hi Ken,

You seem to be implying that I don't understand how a capacitor works, because I stated that current flows through them.

From your first link:

"Here's yet another way to visualize it. Whenever we "charge" a capacitor, the path for current is THROUGH the capacitor and back out again. The extra electrons on one plate force electrons to leave the other plate, and vice versa."

From your second link:

"To store more energy in a capacitor, the voltage across it must be increased. This means that more electrons must be added to the (-) plate and more taken away from the (+) plate, necessitating a current in that direction. Conversely, to release energy from a capacitor, the voltage across it must be decreased. This means some of the excess electrons on the (-) plate must be returned to the (+) plate, necessitating a current in the other direction."

Clearly, current does flow through a capacitor.

[Kenneth Swauger]

Hello,
No such implication was intended. My reason for bringing the subject up was to explain that the reason the subject of capacitors and what they do for audio is so important is that they are not conductors, in the "usual" sense of a conductor. Even their schematic symbol is two vertical lines separated by a gap. Unlike a piece of speaker wire, the voice coil of a tweeter or even an inductor there is not a continuous path. Think about it, you can't "block DC" and be a conductor. If you had a piece of speaker wire that "blocked DC" it wouldn't be a conductor either.
Understand, I'm not saying that capacitors don't work in audio, of course they do. I'm not saying they don't "give the same results" as if they were a conductor, (they do sort of). All I'm saying is that what they do is store a Voltage equal to the Voltage potential placed on their plates and then dissipate it. And that function is different than any other component in the audio chain.
You've heard the expression, "the best capacitor is no capacitor"? So, the goal is to think about the necessary "evils" a capacitor implies and try and make them as benign as possible. But, when I read, "electrons don't know the difference between good capacitors and bad capacitors", I beg to differ. Maybe electrons don't have a preference (they actually do, hence my offer to provide a well written article about how to measure the impedances of capacitors and how to match them) but critical listeners do. There are quite audible sonic differences in capacitors. I wish we didn't need them at all, but at today's level of audio technology we have to deal with them.
Regards, Ken

[WilliamM2]

But, when I read, "electrons don't know the difference between good capacitors and bad capacitors", I beg to differ.

But that's not what I said. I said "Elecrons are stupid, they don't know which cap they are supposed to pass through."

We were dicussing so called "bypass" caps, and although the bypass cap may cut off different frequencies, those frequencies will still pass through the OTHER cap, therefore nothing is bypassed.

[Stew]

Using Sonicaps all around would be over $200 total for all components. But I thinks my SDAs are worth it.

Ka-Ching, Ka-Ching ... That's the sound of me saving to buy all Sonicaps. You convinced me F1nut. It will cost about the same for my 2B's but I agree, they're worth it. Thanks to all for the good discussion and information.

[F1nut]

Ok guys, I just installed the .1uF Sonicaps. They only have about 3 hours on them, but right off the bat I can say that the highs are less edgy than with the silver mica's. In fact, no edge at all. Highly recommended.

[Stew]

Thanks F1nut. That settles it for me. It will be a while before I make the upgrades but, when I do, I'll post how my 2B's turn out.

[schwarcw]

Jesse,

Which capacitor did you by-pass with the 0.1 uF Sonicap?

[F1nut]

I had already upgraded the crossovers in my CRS+'s with Sonicaps, Mills resistors, new polyswitches and new silver mica's. I had also installed Cardas binding posts, added Dynamat Extreme to the steel baskets including the PR's, added four more screws to the PR frames as Polk only used four of the eight possible holes and replaced all the original #6 screws with #8. They already had the replacement tweeters installed when I bought them, so good to go there. I also upgraded the stands, but that's another story.

The results were 99% better than stock, the Sonicap by-pass cap got the last 1%.

[DarqueKnight]

Prior to doing my first speaker mod, on my SDA 1B's, the Polk engineer who advised me said that the "fair" quality 4.4 uF and 12 uF mylar capacitors in the top tweeter circuit were bypassed (paralled) with high quality silver mica capacitors in order to improve the transient characteristics of the mylars. He said that if I replaced the mylars with high quality polypropylenes (Rel-Caps), the silver micas would be rendered redundant and I could take them out of the circuit. He also advised that I could make subtle changes in the speaker's high frequency response by using different types and values of bypass capacitor.

After replacing the mylar capacitors with the Rel-Caps, I noticed no difference in the sound with the 750 pF silver micas in or out of the circuit. The vendor for the Rel-Caps, Precision Audio Supply of Downey, California, suggested I try some polystyrene capacitors. Their suggestion was that, since the polystyrene was a much faster dielectric than either polypropylene or silver mica, I would need to use a much higher value polystyrene capacitor. They suggested 0.015 uF polystyrene film capacitors to replace the 750 pF silver micas. The polystyrenes were 20 times the capacitance value of the silver micas.

The effect of the polystyrenes was a smoothing out of the upper treble similar to the change between the SL2000 tweeter and its silk dome replacement, the RD0194.

I left the silver micas in place in my SDA CRS+'s, SDA SRS's and SDA SRS 1.2TL's.

I did replace the 750 pF silver mica capacitors in my SDA 1C's with 1000 pF MultiCap brand PPMFX series metalized polypropylene capacitors. The effect was similar to that achieved when the silver micas were replaced in the SDA 1B's.

[Stew]

I was trying to understand why I'm going to spend over $200 on capacitors and Jeff at Sonic Craft was kind enough to answer my questions. Specifically, I was trying to understand why high quality capacitors are necessary in the low pass section. Thought some of you might enjoy reading this:

> If I understand how the LP works, the series inductor blocks some of the higher frequencies from the mid-woofer and the shunt capacitor passes some of the higher frequencies away from the mid-woofer to achieve a faster roll off.

That is correct. But, where are these high freqs diverted to? If you guessed that some portion of the signal feed to the tweeter comes by way of the LP shunt cap, you are correct.

> Therefore, the signal going to the mid-woofer doesn't pass through the shunt capacitor.

In order for the capacitor to serve its purpose, it must go in and out of reactance (freq dependent resistor). In order to do this, it must charge and discharge while parallel to the midbass. If this cap has errors/parasitics, it will pass signal it should not while charging (audible high freq errors). While discharging, it will create low freq errors. Not to mention phase issues. Music playback does not resemble any waveform nor is it steady state. As a matter of fact, it looks like random noise (hash). Very complex and very dynamic. Caps are in error to some degree all the time in an audio circuit. These errors will effect your midbass to some degree. If they did not, you could remove the shunt cap with no audible effect as if it were never in the circuit.

> What differences should I expect to hear between a Sonicap and a Solen for the shunt?

It is hard to be specific while never hearing your system, but it is safe to say the midrange should simply sound more "realistic".

[F1nut]

Geez Stew, just buy the damn things. :)

[schwarcw]

Good writeup. I'm with Jesse, just buy the Sonicaps! But don't let me stop you from doing more research. Have fun with the learning process. Jeff at SonicCraft is a good guy to talk to. :)

[Stew]

Schwarcw – The learning process has been fun; Now it’s time to make a decision. In my first job out of school (mechanical engineering), one of the production shops had an edited cartoon that said, “In every job there comes a time when one must shoot the engineer and begin work.” Now is that time. Good luck with your upgrade!

F1nut – I’d love to “just buy the damn things.” Unfortunately, it will be a while as I have several other priorities I need to take care of first.

As for making a decision, I’m going to use Sonicaps (12 uF and 0.1 uF) in the high pass and Solens (20 uF and 40 uF) for the low pass. There seems to be an ongoing debate on whether high end capacitors are necessary in the the low pass. North Creek Music Systems, for instance, states that “For many applications, such as woofer low pass shunt circuits …, one need not spend a fortune on capacitors.” As for the earlier discussion on mixing caps, I’m pretty sure that is only an issue when mixing caps in the same filter. The 50/50 mix referred to in the Tony Gee article seems to refer to using two equal value caps of different type in an attempt to get the sonic benefits of the better cap at a lower price. I found several discussions elsewhere on the subject. Bottom line: I’m not convinced I’ll be able to hear any difference between the Solens and the Sonicaps in the Low Pass. Maybe some of you will convince me otherwise and I’ll exchange them down the road. For now, I think I’ll be happy with the Sonicaps/Solens and the RD 0194-1 tweeters.

[schwarcw]

Sounds like a solid plan Stew. You did your research and probably have good, solid advice. I'm sure you'll be satisfied with your upgrade. Good research for a mechanical engineer! I'm a chemical engineer and lost in all these elctrons. I think in molecules!

My Sonicaps have arrived, but I'm waiting for the binding posts.

[anonymouse]

I had already upgraded the crossovers in my CRS+'s with Sonicaps, Mills resistors, new polyswitches and new silver mica's. I had also installed Cardas binding posts, added Dynamat Extreme to the steel baskets including the PR's, added four more screws to the PR frames as Polk only used four of the eight possible holes and replaced all the original #6 screws with #8. They already had the replacement tweeters installed when I bought them, so good to go there. I also upgraded the stands, but that's another story.

The results were 99% better than stock, the Sonicap by-pass cap got the last 1%.

What difference did the dynamat make? Where did you put it? On the outside ribs of the baskets?