Kef ACE?

[JohnL]

Has anyone seen this? I would love to hear comments from the peanut gallery on this. If it works, it seems like it would be very easy to do, if you like boxes, that is. I'll let all of you talk while I run down to the local pet store and get some filter carbon for my fish tank. :B

KEF ACE Technology

[seattle_ice]

Interesting premise.

It looks like they are saying that the O2 in the air will temporarily bond under pressure to the Carbon, thereby reducing air pressure in the enclosure.

I also read their white paper on the Coincident drivers. Taking coaxial speakers to a new level, and mounting a tweeter inside the voice coil of a woofer.

The 'Ace' concept should not be hard to test for someone with the proper measurement tools.

[Dennis H]

Spendy stuff. A quick Froogle search on activated carbon came up with something like $130/cu.ft. in bulk. Since it works best below 100Hz it would be most useful in subs and you'd need quite a few cubic feet to make much difference. And then there's the problem of containing the stuff so the air gets to it but no carbon gets out.

Interesting but not worth the hassle for DIY, IMO.

[SteveCallas]

They mentioned that when going from a standard 8 liter enclosure to a 5 liter enclosure with the activated carbon, using the same driver, listening tests couldn't determine a difference in low end extension. Why not include some FR measurements as well?

For a DIY approach....someone should try using sponge :B

[seattle_ice]

For a DIY approach....someone should try using sponge :B

Sea, Loofah or Synthetic?

[Dennis H]

Why not include some FR measurements as well?

They did.

[SteveCallas]

Lol, totally missed that.

I wonder how much the difference would be when going from a standard 8 liter box to a stuffed 6 liter box - using normal stuffing.

[sokoban]

Yeah, I would be kinda skeptical about this stuff.

Activated carbon doesn't "trap" fluids or molecules such as O2 Oxygen. The way it works is by being highly porous to allow a large surface area of carbon to bind and remove from the solution more polar impuruties like dissolved Chlorine in water for example. The whole point of using activated carbon is to CHEMICALLY adsorb things, and this is exactly how they are not using it. For the purpose of dampening a sound wave any number of porous materials could probably be found that would work just as well or better. Here's a link that has a pretty good basic description about how activated carbon works. http://chemistry.about.com/od/chemis...f/charcoal.htm

[SteveCallas]

For the purpose of dampening a sound wave any number of porous materials could probably be found that would work just as well or better

So you're saying my poor man's sponge idea has a chance? :lol:

[mmoeller]

Yeah, I would be kinda skeptical about this stuff.

Activated carbon doesn't "trap" fluids or molecules such as O2 Oxygen. The way it works is by being highly porous to allow a large surface area of carbon to bind and remove from the solution more polar impuruties like dissolved Chlorine in water for example. The whole point of using activated carbon is to CHEMICALLY adsorb things, and this is exactly how they are not using it. For the purpose of dampening a sound wave any number of porous materials could probably be found that would work just as well or better. Here's a link that has a pretty good basic description about how activated carbon works. http://chemistry.about.com/od/chemis...f/charcoal.htm

The article is good, but it dosen't address the effects while under PRESSURE. Which is where Kef claims the effect to be present. Other materials are used in similar ways. There is a form of titanium that is used in pressurized hydrogen cylinders. The titanium bonds with hydrogen, under pressure, and makes it completely inert.

I wonder how much the difference would be when going from a standard 8 liter box to a stuffed 6 liter box - using normal stuffing.

According to Martin J. King's quarter-wave.com the stuffing that he used only had an effect ABOVE 100hz or so. The idea of making the enclosure larger comes from the ability to slow down the speed of sound, but at very low frequencies this is difficult. It seems Kef claims that even these low frequency pressure waves can be effectively slowed, inside the box.

I know that many people have stated that you can gain up to 40% increase in volume using stuffing, but once again at what frequencies is this really effective.

You could put your carbon in here. :P

http://www.fritzpet.com/fbags.html

[sokoban]

The article is good, but it dosen't address the effects while under PRESSURE. Which is where Kef claims the effect to be present. Other materials are used in similar ways. There is a form of titanium that is used in pressurized hydrogen cylinders. The titanium bonds with hydrogen, under pressure, and makes it completely inert.

Well, they specifically say that the effects of ther system are due to physical adsorption rather than chemical adsorption. There is no chemical bonding going on with the carbon and the atmosphere. Physical adsorption is mostly a physical property, so I would expect any similarly porous material that isn't very polar to have about the same properties as activated carbon. Crushed ceramics (unglazed, because we want as high porosity as possible) like an earthenware would be interesting to try in the place of carbon, as would really porous lava rock or pumice (I forget the geologist's name for it). These London forces that they claim are causing this adsoption really do have this kind of effect of temporarily associating molecules to one another, but are in no way unique to activated carbon. I would be interested though to see how they manage to mount the activated carbon in the enclsure.

[seattle_ice]

I think there is another factor at work here besides stuffing the enclosure for a perceived volume increase - lessening the mechanical pressure on the driver itself.

[JohnL]

Well, they specifically say that the effects of ther system are due to physical adsorption rather than chemical adsorption. There is no chemical bonding going on with the carbon and the atmosphere. Physical adsorption is mostly a physical property, so I would expect any similarly porous material that isn't very polar to have about the same properties as activated carbon. Crushed ceramics (unglazed, because we want as high porosity as possible) like an earthenware would be interesting to try in the place of carbon, as would really porous lava rock or pumice (I forget the geologist's name for it). These London forces that they claim are causing this adsoption really do have this kind of effect of temporarily associating molecules to one another, but are in no way unique to activated carbon. I would be interested though to see how they manage to mount the activated carbon in the enclsure.

So something like this might be better?
Cell pore