upgrading crossover caps

[dsavitsk]

Out of curiosity, I opened up my old speakers (B&W DM630 from about 1993) today to see what the crossover looked like. There are 3 coils and 3 caps that all say bennic bi-polar on them as well as things about MFD and WV. Are these something that can be easily upgraded? and is it worth doing? Any advice would be graciously accepted.

-d

[wigginjs]

Yes, they can be easily upgraded. No, it's probably not worth doing. The Bennic caps that are being used are of good quality (big, yellow ones?) and you'd end up spending a fair amount of money for very little or no improvement.

[Soulwax]

There are a number of modifications you can make to your crossovers d that subjectively you may find will bring an improvement to sound quality.

The bennic bi-polar capacitors are electrolytic types. Many high quality audiophile crossovers specify polypropylene types as an alternative. There are plenty of brands to choose from if you wish to replace the capacitors. The coils can also be replaced with air-core types, again often a preferred choice for high quality crossovers, this however is not so easy to do without knowing the values of the existing coils. An LCR meter is required to measure the values of the coils if you’re unable to establish this by other means.

The thing to note is that the crossovers will have been voiced with the existing components therefore replacing like for like component values may still result in a subtle shift in tonal presentation. I’d suggest you replace the series tweeter capacitor with a polypropylene type to begin with – SCR is as good a choice as any.

Other than this try removing the crossovers to external enclosures. This I find consistently improves the performance of loudspeakers particularly in terms of high frequency detail.

[dsavitsk]

Originally posted by m0tion
The Bennic caps that are being used are of good quality (big, yellow ones?)

They are definitly electrolytics.

Originally posted by Soulwax
The bennic bi-polar capacitors are electrolytic types. Many high quality audiophile crossovers specify polypropylene types as an alternative. There are plenty of brands to choose from if you wish to replace the capacitors.

It looks like the values are small enough that I could use solens all around and not spend more than about $30. Considering that the speakers weren't super cheap, I am a bit surprised B&W didn't do this in the first place ... on second thought, not I'm not.

It's funny, when buying new equipment, one wants to find ony top quality parts. Otoh, when moding it, it is better if there is garbage.

Originally posted by Soulwax
The coils can also be replaced with air-core types, again often a preferred choice for high quality crossovers, this however is not so easy to do without knowing the values of the existing coils. An LCR meter is required to measure the values of the coils if you’re unable to establish this by other means.

This is probably more than I am going to do in the short run.

By air core, does this just mean that the inside is hollow, i.e., that I can see through it? If so, they are air coils. If not, well then they're hollow.

Originally posted by Soulwax
The thing to note is that the crossovers will have been voiced with the existing components therefore replacing like for like component values may still result in a subtle shift in tonal presentation. I’d suggest you replace the series tweeter capacitor with a polypropylene type to begin with – SCR is as good a choice as any.

Well, if voicing changes for the worse, I guess it will be time to tinker a bit more. Is it worth paralleling a small oil cap or something boitiquey with a solen, or just stick with the polyprop for the series tweeter?

Thanks for the help.

-d

[Thomas001]

Don't forget to solder the internal wire to the drivers .. and may be the upgrading the resistor to the tweeter.

[Madmike2]

Originally posted by dsavitsk



Is it worth paralleling a small oil cap or something boitiquey with a solen, or just stick with the polyprop for the series tweeter?

Thanks for the help.

-d

Oil caps are good ? hmmmm active surplus had loads of them in different values. I thought the dude was pulling my leg when he said they were amazing for crossovers. These things were the size of Liquor flasks and then they got progressively smaller.

[Soulwax]

By air core, does this just mean that the inside is hollow, i.e., that I can see through it?

Yes.

I wouldn’t be concerned with using a small value bypass capacitor. However, if possible, damp the series tweeter cap by rolling it in a sorbothane strip or similar, securing with a tie wrap, and using copious amounts of epoxy to secure.

I’d also advise caution if soldering wires directly to tweeter connection tags as the transmission of heat can cause damage to the tweeter.

[Danny]

As one of the services we offer is speaker upgrades, I have been into and modded a lot of commercial speakers, including several B&W's.

Most of their speakers use just about the cheapest components out there and they have in the past sourced out their complete crossover assembly to Bennic.

There is much improvement ahead by upgrading the parts quality.

The biggest improvement is in the caps. If it uses the Bennic electrolytic caps then just about anything you put in there will be an improvement.

Even some cheap poly caps like Solen or Axon (made by SCR) will be a nice improvement. Further and even more significant improvements can be obtained with various high end caps.

On a budget good results can be obtained by by-passing a Solen or Axon with a high end cap in the .1uF range and still not spend much money.

Changing out the inductors to air cores will be a nice improvement too, but you really need to measure the DCR of the ones that are on there and try to match that value. You will need to go up in wire gauge on the inductors to do that.

Also, they typically use the Bennic sand caste resistors. Get ride of those and upgrade them to. Those are bottom of the barrel on the performance scale. Even a really inexpensive film resistor from Links sounds better.

Keeping the values that you swap out the same will not change the tonal balance of the speakers either.

Good luck, and if you need specific help in needing to know anything feel free to shoot me an e-mail and I'll tell you all that I can.

[playazinc]

I noticed great improvement in my tweeter sound when i swapped my solen cap for a Hovland musicap, i would go so far as to say that it made all the difference between good sound and high end sound, only use air core inductors. Bennics are just as good as solens but between those two and the hovlands and some for the mundorfs thwere is no comparison.

[Soulwax]

Also, they typically use the Bennic sand caste resistors. Get ride of those and upgrade them to. Those are bottom of the barrel on the performance scale. Even a really inexpensive film resistor from Links sounds better.

I find that MOX resistors add a layer of high frequency hash and are best avoided. Preferable are non-inductive wirewound resistors, although sometimes difficult to source.

Keeping the values that you swap out the same will not change the tonal balance of the speakers either.

Substitution of like for like component value but of differing component type has the potential to cause subtle change in the frequency response of the crossover. This at least is my experience of modifying crossovers.

I've not noted any obvious subjective differences between various polypropylene capacitors of comparable quality; I think this is more wishful audiophile thinking. Certainly there are audible differences between bi-polar electrolytic and metallised polypropylene capacitors when used in loudspeaker crossovers.

Still, the larger gains are to be had by structurally de-coupling the crossover from the loudspeaker enclosure in some manner.