[rockadanny]

Speaking in generalities and approximations as an electronics ignoramus ...

In a speaker crossover at the capacitor, if you wish to tweak the sound a bit you can add a small bypass cap (I've been told).

1. How can a bypass cap of only 2%-5% value of the larger cap do anything?
Wouldn't such tiny cap values barely allow ANY audible frequencies through? For an 8 ohm example, 1 mfd would not allow freqs below 19kHz through, correct?

2. I've heard that if the cap is large it may have difficulties producing the highest of freqs, so a bypass is necessary to augment the higher freqs.
Yes? No?

[nlitworld]

From my limited technical understanding, having a bypass cap on a larger cap allows the snappy quick discharge and recharge of electricity which helps bring out inner details. Having different caps to instill a bit of voicing is even with the value being only 1-5% it's still something. This I have tested quite a bit, and my choices always go back to something like a Miflex cap.

As for the values affecting frequency response, when caps are combined in parallel it is electrically one solid capacitance value. If they were in series, you'd have different things all together. And the size of bypass cap being too large mostly comes down to phase shift between main cap to bypass cap. Tiny little guy doesn't have much on that, but like a 30% value would cause issues.

Again, don't ask me about the math on why these things are the case, but sonically speaking it flat-out works great. Try a 0.1uf 250v on your tweeter cap and see what you think. I believe you can still find Miflex from HiFi Collective. Hope that helps.

-Lloyd

[Early B.]

I asked this same question back in 2013 and received a bunch of insufficient technical answers. The best responses I've heard over the years were from Danny and Hobbs. I tried searching this forum, but I can't find them.

My non-technical understanding is that a large capacitor holds more energy and discharges more slowly, which can smear the signal. With a bypass cap, the electrical signal travels through the smaller cap to mitigate the detrimental effects of stored energy in the "fat cap." An analogy is a highway bypass -- they're designed to provide faster, more efficient travel and reduce traffic congestion.

Interestingly, after I wrote this, I asked ChatGPT about bypass caps in speaker crossovers, and it offered the same analogy:

Imagine your speaker crossover as a traffic manager at an intersection, directing different sounds (like bass, midrange, and treble) to different lanes or drivers (the speaker drivers). Normally, each sound type (bass, midrange, treble) is routed to its own speaker driver (e.g., a woofer or tweeter) so that it plays optimally for that driver. Now, a bypass capacitor is like a shortcut that allows some high-frequency sounds (treble) to bypass the usual traffic signals (the crossover circuit). It provides the treble a shorter path to the tweeter, helping it reach the speaker driver more directly. In simple terms, the bypass capacitor on the highs, for example, ensures that the treble reaches the tweeter without delay or unwanted interference, leading to cleaner and more accurate sound. 

[mick wolfe]

  That's a very good explanation. Thx.

[jonbee]

I've tried them on many speakers over the years. After 58 years in the hobby, I trust my ears as an arbiter, but the results only apply to me.
I've found they help clean up and open up the top end, sometimes impressively, but sometimes there is no discernible difference. Lately I put some Audyn Copper .1 mfd on the tweeter caps in my revels, and found it to be helpful. Sonicaps are often useful for less $. YMMV. Trust your ears to find satisfaction.

[FullRangeMan]

Speaking in generalities and approximations as an electronics ignoramus ...

In a speaker crossover at the capacitor, if you wish to tweak the sound a bit you can add a small bypass cap (I've been told).

1. How can a bypass cap of only 2%-5% value of the larger cap do anything?
Wouldn't such tiny cap values barely allow ANY audible frequencies through? For an 8 ohm example, 1 mfd would not allow freqs below 19kHz through, correct?

2. I've heard that if the cap is large it may have difficulties producing the highest of freqs, so a bypass is necessary to augment the higher freqs.
Yes? No?

For this reason I use Crossoverless Full Range Drivers.

I sure the right person to explain this with practical experience is Danny.

[jtwrace]

and Hobbs.

Where is he these days?

[Early B.]

For this reason I use Crossoverless Full Range Drivers.

I sure the right person to explain this with practical experience is Danny.

Danny also explained why crossoverless designs are a bad idea.

[FullRangeMan]

Danny also explained why crossoverless designs are a bad idea.

All the speakers that Danny sells have crossovers.

[mick wolfe]

I've tried them on many speakers over the years. After 58 years in the hobby, I trust my ears as an arbiter, but the results only apply to me.
I've found they help clean up and open up the top end, sometimes impressively, but sometimes there is no discernible difference. Lately I put some Audyn Copper .1 mfd on the tweeter caps in my revels, and found it to be helpful. Sonicaps are often useful for less $. YMMV. Trust your ears to find satisfaction.

Same positive experience here. As you say and I agree, if there is downside it's simply a case of nothing gained. However, my positive experiences surely outweigh the "nothing gained".

[hayden]

If they are really “faster” then it changes the arrival time of sound to our ears - no? Seems to go against the design of the crossover. Could this issue be simply nerdy audiophile confirmation bias?

[nlitworld]

Here's best example I could think of with visual representation of what I think is happening electrically.

Think of it like a square wave on an oscilloscope. Ideal is perfectly straight up with a perfect 90° angle at top, and a perfect vertical drop with no overshoot. In reality, there's a slight angle to any rise & fall and slight rounding of the corners and tiny overshoot. The "faster" bypass cap helps steepen those rise/fall and square off those corners.

Now I'm not saying that you can easily measure this in an A/B comparison on an oscilloscope, but you sure can hear it. Especially cymbals, you will likely hear more clarity and attack on the front end of a strike and clearer shimmer to the sustaining ring. Also since the small caps recharge faster, you will hear more definition to some Buddy Rich style fast cymbal roll.

[Early B.]

Yeah. The term "fast" is a descriptor of sound, not speed. The opposite is also true -- "slow" bass sounds boomy.

[rockadanny]

Thank you for the understandable description!