My tweaks include replacing tweeter caps with Obbligato Premiun+ caps, adding a Jantzen 5.6uF Superior Z-cap to the mid range filter and replacing the two iron core inductors with air core inductors. And I will consider adding an R2 to the mid range filter. And R1 is 0.56ohms.
Replacing electrolytic caps with poly ones is not an improvement. It is a step back because you aren’t counting the ESR of the electrolytic which is way higher than in a poly cap.
Also replacing a cored with an air core coils without knowing the DCR of the original coil is altering for the worse the sensitivity of the speaker. With a 5-8 mH coil the difference in DCR can be huge. As an example with a 5.6 mH coil:
air core 1.4 mm wire, DCR 0.87 Ohm, 1 kg, 50 Euro
cored 1.0 mm wire, DCR 0.45 Ohm, 400 g, 13 Euro
IMHO you are wasting time and money. The only sensible thing to do is replace the electrolytic caps which can be off spec with equivalent ones (i.e. electrolytic), and replace ferrofluid as suggested by Steve.
Ralf
Also replacing a cored with an air core coils without knowing the DCR of the original coil is altering for the worse the sensitivity of the speaker. With a 5-8 mH coil the difference in DCR can be huge. As an example with a 5.6 mH coil:
air core 1.4 mm wire, DCR 0.87 Ohm, 1 kg, 50 Euro
cored 1.0 mm wire, DCR 0.45 Ohm, 400 g, 13 Euro
IMHO you are wasting time and money. The only sensible thing to do is replace the electrolytic caps which can be off spec with equivalent ones (i.e. electrolytic), and replace ferrofluid as suggested by Steve.
Ralf
Based on scientific test data, displayed and explained on several sites, comparing electrolytic caps with poly caps and Fe cored inductors to air core inductors I disagree with your arguments. The following are some of the findings
- Electrolytic Capacitors suffer hysteresis effects which can negatively impact audio.
- Electrolytic Capacitors suffer from high dissipation, which cannot be minimized without using multiple capacitors in parallel.
- Saturation is not a digital phenomenon - It happens gradually and the magnetic core choke increases distortions at levels considerably below those at which the cores will "Saturate".
- Magnetic core Inductors are inherently nonlinear, even before saturating.
Adding C3 will change how the system sums across the higher crossover, likely putting a dip in the frequency response. However it may still give a subjective better sound, even if technically less flat. That is because the break-up of the midrange cone drive at higher frequencies is quite likely unpleasant sounding, and why higher order (more expensive) crossovers tend to be used.
The idea it is OK to replace a poor electrolytic with a better one, but not with a film capacitor, is of course fallacious - a "better" electrolytic capacitor will simply be more like a film capacitor. Changing the electrolytic capacitors for film ones will reduce the ESR (effective series resistance) of the filter, and therefore result in slightly more HF output, a similar effect will occur from using lower ESR inductors for the bass filters. The system may need to be re-voiced by changing the value of R1 as a consequence to rebalance the highs and lows.
The idea it is OK to replace a poor electrolytic with a better one, but not with a film capacitor, is of course fallacious - a "better" electrolytic capacitor will simply be more like a film capacitor. Changing the electrolytic capacitors for film ones will reduce the ESR (effective series resistance) of the filter, and therefore result in slightly more HF output, a similar effect will occur from using lower ESR inductors for the bass filters. The system may need to be re-voiced by changing the value of R1 as a consequence to rebalance the highs and lows.
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The B&W P5 low pass filter diagram has + from the amp first going to L1 to the mid range and L2 is connected to the + line between L1 and the line to the midrange. So is the woofer seeing the seeing the combined induction values of L1 and L2? In one of the other diagrams + from the amp goes directly to L2 and L1 is connected after L2. Is this woofer seeing just the inductor value of L2.
I have no clue what you are referring to. My question was about potential differences betwen XO diagrams.
They(bower and Wilkins) make their own speakers and in this model the difference between the two, apparently from the outside, it's the membrane material. You'd want the heavier cone to reproduce the low bass and not the contrary, right?
So it's also a combination of electrical (the crossover) and acoustic properties of the material-a heavier cone has more difficulty to vibrate fast(=high in frequency) - so the analysis should comprehend many things. ..as usual!
I made a mistake in my drawing above, and put L2 on the wrong side of L1. The B&W schematic is correct for P6 (even though the drawing says P5).
Yes, the inductance is the series sum of the two coils for the lower woofer, which makes the crossover somewhere around 200Hz. Both woofers have a nominal low pass crossover slope of 6dB per octave, however the actual crossover frequency and slope is indeterminate without knowing the drivers' impedance and impulse response.
Now I don't know much about electronics but I thought if inductors are connected in series the total inductance of L1 0.9mH + L2 5mh = 5.9 mH. But I also believe the total can vary depending on the position of the two inductors. So the Fe core inductors on the PCB are shown in the sketch. Any idea, based on their positions, of what the sum of the mH value would be?
No, the woofer would roll off faster because the mid connection between the inductors disrupts them. I can arrange a basic demonstration if Henry would like.
Yes that is true, but not by very much, and the ceramic cores (especially with the discs on the ends of L2) reduce the mutual coupling by an order of magnitude as well. I would expect the effect on inductance values would be irrelevant compared to the normal manufacturing tolerance range of value of the individual inductors.
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I attempted a simple sim of this (without the necessary driver data) and unless I made a mistake the rolloff for the lower woofer approaches 12dB per octave, so AllenB is correct.
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