[6RS]

Hi
I want to upgrade the Xover of my speakers.
There seems to be a consensus among distinguished DIYs that using bypass capacitors is beneficial. As far as I understand, a bypass capacitor is a capacitor of <1% the value of the capacitor it is mounted to in parallel.
My questions are:
a) Which capacitors in a Xover are worth bypassing in a parallel Xover? (1) All, (2) Only then ones iin the signal path, (3) Only the last one in the signal path of the tweeter etc.
b) What is the best value? (1) 1%, or (2) very small, eg 0.01 µF
c) Would you buy the best you could afford (eg. Duelund , or something cheap?
Thanks for your insight!
B

 

[amb]

Bypass electrolytic caps in the crossover, especially any in the tweeter circuit. For those caps that are already film types, you can leave them alone, or replace them with better types (e.g., upgrade from polyester aka mylar to polypropylene).

 

[Ferrari]

Agreed with amb's thought.

Assuming filters design are (more or less) optimal, I think that the quality of the serial components (RCL) in the filter sections of the mid-range(s) and tweeter determines for a lion part the final quality of the audio band which these drivers are responsible for.

Use good quality MKP for all caps that forms high-pass filters caps for the mid-range(s) and tweeter (serial caps in the positive pole of the crossover) if you can if you can afford it. The caps in the bass section are mostly large value bi-polar electrolytics due to the cost (and sometimes also the size).

Of course the cost and quality ratio of speakers/capacitors should not be forgotten.
$400 quality caps for speakers with a couple of alcheapo drivers @ $100 won't help much!

 

[6RS]

Thanks for the answers!
The speaker is an ATC SCM20SL. Tweeter is a Scan speak revelator (about 150$ each), bass/mid driver ATC's own driver, around 700$ each. Xover is relatively simple: 2 caps (10 and 5.47 µF), an inductor (0.26mH) and three resistors (2x 2.2 and 10Ω) for the tweeter, and an inductor (0.5mH), two caps (6.8µF, 10µF) and a resistor (10Ω) for bass/mid driver.
I have upgraded all the components already. For caps I used auricaps, inductors are alphacore 12awg, resistors are Duelund graphite. This made a big improvement over the decent but "nothing to write home about" components. So the consensus seems not to use any bypass caps in addition?

 

[Ferrari]

Quote:

Originally Posted by 6RS /img/forum/go_quote.gif ...So the consensus seems not to use any bypass caps in addition?

No I don't mean to say that. Paralleling caps can improve the sound, BUT... the total capacitance at a certain position in the filter should be taken into account! If you just add a small value cap into an existing cap in the filter, you are altering the corner frequency a little, and... this can (negatively) influence the sound of your speakers system.

I do paralleling caps with great results. Here are the two ~6.8µF caps (build up from a couple of small 1% caps

) which I prefer over many other good MKP caps, including Auricaps and Mundorf MKP. Your drivers are excellent, btw.

 

[6RS]

Thanks. 52 caps in parallel to build a 6.8µF - holy ****! Is this for a xover? If so, I bet your xover does not fit inside the speaker box

Cheers, B

 

[amb]

Quote:

Originally Posted by 6RS /img/forum/go_quote.gif So the consensus seems not to use any bypass caps in addition?

There is no need to bypass the already-fancy boutique caps you have in there.

As Ferrari eluded to, putting two capacitors in parallel creates the equivalent of a single capacitor with the sum of the two capacitances. In a speaker crossover, the capacitance values should not be altered significantly or you'll mess up the filter response characteristics. Adding a 1uF film bypass cap to a 100uF electrolytic is not a big deal because it's only 1% difference, but the same 1uF cap in parallel with a 3.3uF cap is a 30% increase!

 

[6RS]

Quote:

Originally Posted by amb /img/forum/go_quote.gif There is no need to bypass the already-fancy boutique caps you have in there.

There are forums where an auricap is considered a wannabe or poor man's boutique

I thought using 0.01 or 0.1 bypass. At this value one could afford the real boutique stuff like teflon V-Caps, or Mundorf silver/gold/oil

Maybe I just tinker around a little. I may end with: "Ok, I spent 100 bucks and three hours of my time, and the result is: nothing. Let's spend another couple of bucks for a beer."

 

[nspindel]

I recently did the XO's in my Polk SDA's with Sonicaps. The original caps were bypassed, but the advice I got in the Polk forums was that using bypass caps high quality caps like Sonicaps was not required, and in fact can leave unpleasant artifacts in the sound. I did not use bypass caps, and the speakers sound incredible:

Oh my, something magical has happened to my SDA's - Club Polk

 

[6RS]

Quote:

Originally Posted by nspindel /img/forum/go_quote.gif Oh my, something magical has happened to my SDA's - Club Polk[/url]

I do agree that the changes were astounding, and I am very happy with the sound! But... imagine... it could be even BETTER... some forum voices wisper, just use bypass caps

We'll see whether there is any truth to it for my application, I'll just try two bypass caps and listen.

 

[nspindel]

Try it without them first, see how it sounds. Then try using the bypass cap, see if it improves anything...

 

[Ferrari]

To my opinion, a soft dome tweeter from the calibre of ScanSpeak Revelator (or Dynaudio Isotar/Isotec) deserves something better than Auricaps. There are many better choices on the market, of course at (a bit) higher cost, but a ScanSpeak Revelator tweeter is worth it to look further.

I’m using a variant of the ScanSpeak Revelator (same spec but with smaller mounting aluminum face plate) with the caps I posted earlier in post #5. If these caps were not available (if the small polystyrene caps were not to source), I have certainly looked at something like Mundorf MCAP silver/oil.

I know, using Mundorf MCAP silver/oil for both the 5.47µF and 10µF caps in the 18dB tweeter filter section will kill your wallet, but luckily there are many other alternative available. Take a look at this thread, for example.

 

[6RS]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif I know, using Mundorf MCAP silver/oil for both the 5.47µF and 10µF caps in the 18dB tweeter filter section will kill your wallet, but luckily there are many other alternative available. Take a look at this thread, for example.

I need to get some experience what improvement we are talking about.
What do you think about V-Cap OIMPs?
Mundorf Silver/Oil would cost 370$, V-Cap OIMPs 270$.
Thanks, Bruno

 

[6RS]

What the heck.... ordered Mundorf Silver/oil for the tweeter section.
I will report whether I can hear any difference to the auricaps.