hi, I would like to kindly ask for any help/advice.
I have had these speakers for almost 20 years, and I'm thinking about upgrading its crossover.
Speakers are 8 Ohms and with cross-over frequency 3kHz.
I plan to use Mundorf components, 4,7uF and 10uF capacitors - I guess both are for the tweeter. These are visible on this upgrade:
I'm not sure if the existing original is the same design, I guess I will find out once I will open the box 🙂
But I'm not sure about inductors/coils. Based on calculations, I should use 1-1,5 mH inductor for the woofer and 0,4-0,5 mH for the tweeter.
I guess these values will not be marked on the existing crossover and I'm not sure if I'm correct and will not corrupt the sound.
This is how probably original crossover looks like: https://bowerswilkins.encompass.com/item/12592525/Bowers__Wilkins/ZZ10340/
thank you in advance for any input,
Tomas
I have had these speakers for almost 20 years, and I'm thinking about upgrading its crossover.
Speakers are 8 Ohms and with cross-over frequency 3kHz.
I plan to use Mundorf components, 4,7uF and 10uF capacitors - I guess both are for the tweeter. These are visible on this upgrade:
I'm not sure if the existing original is the same design, I guess I will find out once I will open the box 🙂
But I'm not sure about inductors/coils. Based on calculations, I should use 1-1,5 mH inductor for the woofer and 0,4-0,5 mH for the tweeter.
I guess these values will not be marked on the existing crossover and I'm not sure if I'm correct and will not corrupt the sound.
This is how probably original crossover looks like: https://bowerswilkins.encompass.com/item/12592525/Bowers__Wilkins/ZZ10340/
thank you in advance for any input,
Tomas
Redesigning the crossover might be worthwhile.. However if you want to keep the original circuit you could measure the inductors. On the other hand, do they really need replacing?
Lojzek I agree, but I'm afraid I will not be able to measure coils (inductors) 🙁 my multimeter does not support that
actually, if I use this calculator: https://speakerwizard.co.uk/calcs/Crossover_Calc_v2.php
then here are suggested values
then here are suggested values
Can you set the inductors in a resonant circuit and use the resonance frequency to calculate backward?
As AllenB said, a crossover redesign could be useful. However this imply (a lot of) experience. So I'd not recommend it.
The whole idea that swapping components with "better" ones will result in an upgrade is debatable, to say the least. In my opinion, is rubbish.
What you can do is to get out the crossover and simply replace all the electrolytic caps (if there are any) with equivalent ones, as the old caps are probably dried. Other components (film caps, resistors, coils), should be kept unaltered. The reason to replace electrolytic with electrolytic is that different kind of caps have different ESR (sometimes very different), and a competent designer like the ones at B&W will design a crossover taking care of the capacitor ESR. So replacing an electrolytic with a film cap is a downgrade, as you'll alter the frequency response of the speaker.
A last word about the crossover calculators/textbook crossovers. They simply don't work because they assume a constant resistance and flat frequency response over a large region around the crossover point. A real driver however has impedance that varies with frequency, and usually also the frequency response is all but flat near the crossover point.
Ralf
PS It seems that the B&W Service Manuals site is gone, so I don't know what components there are in the DM305 crossover
The whole idea that swapping components with "better" ones will result in an upgrade is debatable, to say the least. In my opinion, is rubbish.
What you can do is to get out the crossover and simply replace all the electrolytic caps (if there are any) with equivalent ones, as the old caps are probably dried. Other components (film caps, resistors, coils), should be kept unaltered. The reason to replace electrolytic with electrolytic is that different kind of caps have different ESR (sometimes very different), and a competent designer like the ones at B&W will design a crossover taking care of the capacitor ESR. So replacing an electrolytic with a film cap is a downgrade, as you'll alter the frequency response of the speaker.
A last word about the crossover calculators/textbook crossovers. They simply don't work because they assume a constant resistance and flat frequency response over a large region around the crossover point. A real driver however has impedance that varies with frequency, and usually also the frequency response is all but flat near the crossover point.
Ralf
PS It seems that the B&W Service Manuals site is gone, so I don't know what components there are in the DM305 crossover
I took that image from the diyAudio swap meet thread you linked to in post #1.
Sorry, that indeed showed an "upgraded" crossover.
However, the only information given was, "Modifications include 5% polypropylene audio capacitors with high quality ultra pure solid copper wiring."
Just to emphasise what giralfino said, when B&W designed the crossover for the DM305 they did not use a simple crossover calculator like the one you illustrated in post #7.
They used a much more sophisticated methodology to arrive at the component values that insured the optimum integration of woofer and tweeter.
Unless you are privy to their methods, you are best to limit yourself to replacing old bipolar electrolytic capacitors with fresh new ones, while leaving inductors and resistors well alone.
They used a much more sophisticated methodology to arrive at the component values that insured the optimum integration of woofer and tweeter.
Unless you are privy to their methods, you are best to limit yourself to replacing old bipolar electrolytic capacitors with fresh new ones, while leaving inductors and resistors well alone.
Yes, actually I have found this original oem part image
https://bowerswilkins.encompass.com/item/12592525/Bowers__Wilkins/ZZ10340/
Coil seems to be “air” core, so I will try to upgrade its capacitors only 🙂
https://bowerswilkins.encompass.com/item/12592525/Bowers__Wilkins/ZZ10340/
Coil seems to be “air” core, so I will try to upgrade its capacitors only 🙂
For some reason, I am being blocked when I try to open that link. Can you paste an image instead?
I am also puzzled by that novelty, not offering service manuals as they used to.
There are only two capacitors visible in that image rather than three in the upgrade image - and their values are not readable.
Let's wait and see what you find when you actually take your crossover out of the enclosure.
Upgrading caps to Mundorf would be keeping within what B&W does between their middle and top tiers. I believe at least one set of B&W bookshelves were identical except for the quality of the caps. If it's affordable for you, and simple enough sure, go ahead.
In general though it's always worth considering how well a crossover design is before doing 1:1 part replacements. Lots of times original crossovers were lacking and would benefit more from a white paper rethink than cap replacements.
In general though it's always worth considering how well a crossover design is before doing 1:1 part replacements. Lots of times original crossovers were lacking and would benefit more from a white paper rethink than cap replacements.