Shown are two full crossovers, labeled A and B, with their differences shaded in color highlighting (orange, pink, yellow, blue, green). Each crossover was designed for identical LF, MF, and HF drivers except the HF driver in B has ferrofluid (ie., the HF driver in A does not have ferrofluid).
QUESTION: Can you identify what function each of the color shaded legs are meant to provide? (E.g., the yellow leg appears to be a notch filter in the LF driver's low pass filter...it may be there to alter impedence and/or attenuate some portion of the spectrum that's passed to the LF driver.)
BONUS QUESTION: Both A and B were production crossovers. What two loudspeakers were they used in?
QUESTION: Can you identify what function each of the color shaded legs are meant to provide? (E.g., the yellow leg appears to be a notch filter in the LF driver's low pass filter...it may be there to alter impedence and/or attenuate some portion of the spectrum that's passed to the LF driver.)
BONUS QUESTION: Both A and B were production crossovers. What two loudspeakers were they used in?
In crossover A, the pink leg is a Zobel (R5 and C10) in the LF driver filter. Why did the designers delete it in crossover B?
Similarly, in crossover A, part of the green leg is a Zobel (R6 and C3) in the HF driver filter. I'd guess the designers deleted it in crossover B as the tweeter in speaker B had ferrofluid which damped the transducer's resonant frequency.
But what does L2 accomplish in the crossover A HF driver filter?
But what does L2 accomplish in the crossover A HF driver filter?
In part, the capacitor reduces the influence of the driver impedance rise. Often the remaining influence can be tuned out by adjusting the low pass filter.
A have 4-th order filters on LF and HF and 3-rd order on MF, B have 3-rd order in LF and HV and 2-nd order in MF. 4-th order filter need zobel to be accurate. B is simplified and cheaper A, made for lower total power speaker.
In crossover A, if I were to calculate the center frequency for both the Zobel in the HF filter and, again, for the Zobel in the LF filter, I'd discover the values are at, or very close to, the HF-to-MF crossover frequency and the MF-LF crossover frequency respectively?
This is all very cryptic. Can you not provide more information about this whole thing?
Due to other factors this may have no significance.
Things coincide in this region as the driver comes to the end of it's useful range. It doesn't have to be anything special.
The Post is for my education in xover design above and beyond simple x-order filters. I'm educated in control theory and a retired engineer. But electronics is more of a hobby.
I seek to better understand some secondary filter components (e.g., Zobel, notch filters, Lpad...). Furthermore, I have owned Speaker A (which has Crossover A) for many years and am considering removing the series notch filter (parallel circuit in series with the driver) in the LF xover. Hint: this was recommended in 1989 by Van Alstine for certain users of Speaker A. So learning more about it's transfer function, what frequency band it's meant to attenuate, etc is of interest to me. I may install a switch for disabling/enabling it instead of simply desoldering it altogether.
I'm not a VituixCAD or Spice user (though that may be next in my journey). Still I imagine that without many design parameters of the specific drivers in Speaker A (or B for that matter) there's not much to model/learn.
Less cryptic now?
Partially. What speaker is it? B&W? Nobody can guess the precise effects of the notch or zobel without the component values or having the response and impedance measurements of the drivers in the cabinet. Generally, in A, the rolloff will be steeper than B and a breakup peak at the far end of its range will be attenuated. If the improvement is claimed by removing these corrections, but the speaker is truly otherwise identical, I guess the thought is that it sounds better without it and the breakup peak isn't audible anyway.
You can often achieve similar results using either method.
Firstly, it’s the result that counts and secondly, we could be talking anything from minor details to a major oversight.
Firstly, it’s the result that counts and secondly, we could be talking anything from minor details to a major oversight.
The attached spreadsheet captures function (i.e., usage in the filter) and value for every component in Speaker A's crossover and Speaker B's crossover.
The third Column (from left) has various TBDs as I don't fully understand the function of those legs within the LF filter and/or HF filter (thus my initial post with color shaded components).
So, back to my original post, QUESTION: Can anyone here identify what function each of the color shaded legs are meant to provide?
Have we been too subtle? For the reasons I explained, I am reluctant to try to name sections when I know that the looks and the actions can be so far apart..
So, if you want to put names to them..
Orange=part of the low pass filter
Pink=impedance rise compensation
Yellow=bandstop filter, possibly for breakup peak
Blue=high pass filter, and an almost redundant looking part of the low pass filter
Green=part of the high pass filter plus impedance rise compensation
Do that!
Vituixcad is incredibly instructive in showing complex interaction of speakers with crossover networks.
You also need the actual driver impedances in the models for any of this to really make sense. As stated earlier, many crossover functions wind up blending together, so it gets harder to say X does exactly Y. In modern crossovers designed with simulators a lot of it comes down to the designer's preferences. There are usually many ways to achieve nearly the same result. Cost and desire for simplicity (or complexity) also come into play.
Low pass
(A) Lime 4th order LP /Violet 4th order LP+zobel / 4th order LP+zobel+notch
Midrange
(A) is a 4th order HP - 3th order HP / (B) is a 2nd order HP-LP: it's a designer's choice as he wanted shallower slopes.
Tweeter
(A) Red is a 4th order HP / Blue 4th order HP+zobel (B) is a classical 3rd order HP with a different attenuation resistance (likely).
(A) Lime 4th order LP /Violet 4th order LP+zobel / 4th order LP+zobel+notch
Midrange
(A) is a 4th order HP - 3th order HP / (B) is a 2nd order HP-LP: it's a designer's choice as he wanted shallower slopes.
Tweeter
(A) Red is a 4th order HP / Blue 4th order HP+zobel (B) is a classical 3rd order HP with a different attenuation resistance (likely).