Question is, why bypassing?
And what are the differences when bypassing the crossover caps; are there differences in soundstage, maybe more or less detail, more warmth or less hardness in the treble?
The Vishay MKP 1837 0,01uF seems to be very popular.
Is the anyone who has experiences with bypass caps in crossovers?
Bypass caps are high-pass filters that let frequencies above their knee avoid the resitive component of the XO. Ideally, the 'boost'' picks up where your driver begins to fall. Requisite for constant directivity horns.
As for quality, just make it "better" than the cap it bypasses.
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One example of this might be to use an L-pad and/or resistor along with a 15uf cap to reduce the intensity of a constant directivity horn and match the horn to a woofer. Next you could use a 1uf cap to
bypass the L-pad, resistor and 15uf cap.
This would allow higher frequencies to pass on to the horn unattenuated and possibly give a warmer sounding signature. (subject to personal preference of course)
Originally Posted by bfish
Thanks,
I used bypass caps in my crossover, my intention was; less dynamic and warmer sound, or maybe because the sound was a little warmer it looked like there was a little less dynamic in the sound.
I asked this question on this forum, because maybe there are some other people here who had the same experience.
I think there are two different meanings to the word "bypass" in use here. In the first, a small value, high quality cap is installed in parallel with a much larger value cap of dubious sonic merit to improve the sound at modest cost. This used to be done a lot, often to overcome the lousy sound of electrolytic caps. Haven't kept up with audio tweaking in recent years, but I think the wide availability of quality oil and film caps at good prices has lessened the need for bypassing bad sounding ones.
In the second use, a compression driver often needs to be padded down 10dB or more to match output with a direct radiator woofer. This knocks down the response of the driver over its entire bandwidth. A small cap of the right value paralleling the pad will allow the highest frequencies to escape the pad, effecting an EQ boost on top that can correct for the rolloff in power response above the mass corner, as both are basically 6dB/octave slopes. I do this all the time and it works great.
To complicate the subject further, I have had success with a method employed by JBL in recent years in several of their hi fi speaker passive crossovers. It is called "charge coupling", and involves biasing the crossover capacitors with batteries. It seems that capacitors are highly nonlinear near their zero voltage regions, just as transformers are. Biasing the crossover with a battery places small signals up in a highly linear region. The technique requires four times the total capacitance of a non-biased circuit, though I suppose it could be argued that less costly caps could be employed. Anyway, I have found that it works well... always something new to try.
what Steve says, is quite accurate, with regards to audio.
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I had communications with Zilch and proposed a listening test to determine if either of us could hear a change when some Magic "Vs" 0.01s were paralleled with the standard XO caps. I paralleled six large caps 16 down to 0.66uF in my Low pass section. The Low section was modified by adding relays to switch in/out the 0.01 caps. This way the only thing changed was to add the caps. I did the same thing to the Hi freq section and proceeded to listen. My listeners and I could A/B adding 0.01uF caps to the low section , the high section , or both. We could not hear a difference . Neither good or bad. I never got to include Zilch in this test. My impression was that he did not expect to hear a difference.
Since most of the caps I use are made up of a large cap and a small one ( 7.27 = 6.8+0.47 ) to get the value I want, one could argue that they are already bypassed.
Don
Not really. Bypass was intended to be a small cap connected in parallel with a large one, to take care of the high freqs.
A good example is a power supply electrolytic say 100 uF. The way it is made is to wind up long strips of insulated foil and connect to one end of the long strips. This "coil" of foil is a cap, but by coiling it up, it has inductance too . The way a small mylar or poly is made, is also a coil of insulated foil but with exposed foil on two edges of the foil and that becomes the coil, allowing a continuous connection to the foil. The edges are soldered to lead wires, making the connections, the solder shorts out the coils and eliminating the coil effect.
Don
Yes, I think this would be bypassed according to Steve's first definition but not according to his second definition of bypassing.
Also, in the second definition of bypassing, if I wanted to know the effects of the bypass cap such as a .47uf, I would first connect it dirrectly to the HF driver without anything else in the circuit.
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