SDA 2B Upgrades/Amplifier Questions

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.

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

F1nut wrote:

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. 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

F1nut wrote:

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.

Normanality

SCompRacer wrote:

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.

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?

[Deleted User]

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