Material from the Dark side improves bass...?

[wkhanna]

KEF says they can use activated charcoal to enhance bass response in smaller cabinets....LINK

I will have some material for a project at work. LINK

If someone wants to try some experimenting, let me know, i could supply some of the material.

[deewan]

Interesting.

1) I wonder how the ACE or charcoal is placed in the cabinet? Dumped on the bottom of the cabinet? Lining the walls while in an acoustically transparent bag of sorts?
2) How much is needed? Does a tiny lining on each wall help? Or does there need to be an inch, two inches on each interior wall to help?

I always laugh when I read claims like... "In addition to the measurable parameters, the sound quality of ACE enclosures is consistently well liked by audiophiles, with a precise and detailed bass reproduction". Until I see data that proves otherwise I won't argue that the activated charcoal can help reduce the cabinet volume. But improved sound quality? Who were these audiophiles that could hear a difference and where they told which cabinets had activated charcoal? :roll:

[wkhanna]

i might suggest placing the carbon material in permeable sacks such as cheesecloth or burlap.

the sacks could be sized & shaped to fit the cabinet.

or maybe just a bunch of tube shaped sacks attached to the interior walls.....?

[JonMarsh]

What this does is similar to critically over stuffing a sealed cabinet. The basic function is to increase enclosure damping by changing the effective adibiatic ratio of the cabinet and increasing the resistive effect even though compliance (VAS) is nominally from the small volume. The charcoal is just convenient becuase it has the very small pores and passages- and the transfer of air through these provides the resistive effect. Additionally, I would expect it to work well at enclosure boundaries, where pressure is high and velocity is low, whereas conventional damping materials work better towards the interior of the enclosure where the opposite is true.

The claims for better audiophile sound would be based on the simple physics of altering or improving or maintaining the desired target Q, which ironically, was something of an issue with the Ls35a, who's small enclosure results in a bump up in the bass response in the area just above 100Hz, and higher Q, which means overhang (overshoot or outright ringing) in the transient response. Of course, most ported systems have even more overhang, and this becomes more objectionable when it's in the mid to upper bass region becuase it smears instrument transient response. This is typically the Fb area of small speakers. OTOH, reflex tuning is not as often minded by "audiophiles" when it is in the low bass, because then it produces an overhang which is more akin to room resonance, and doesn't color the primary fundamental or first overtone pitches of instruments.

For a home work assignment, you may study different LF alignments in Unibox, ported as sealed, at different Q values, and note the calculated step response from Unibox, which is pretty accurate.

Still, in the end, it's about making the boxes smaller and cheaper and easier to ship. You notice they aren't bringing up using this in the larger systems?

[wkhanna]

is there any there advantage to be gained over the use of standard OC fiberglass insulation?
would it take less (volume) carbon to achieve equivalent results?

[JonMarsh]

That's what they're claiming. OTOH, most people don't properly stuff sealed enclosures with fiberglass, either- you need to use a lot more than is necessary just for suppression of midrange reflections. You want to increase the amount of stuffing, while measuring the Fb, which as you add stuffing will continue to drop until you hit the optimum point, above which the Fb will start to rise as you add more.

All of this is ONLY valid for sealed designs, such as the bass system on the Wavecor Ardent, or my own version of the Isiris. NatP is ported, and you can't use this technique- it will effectively convert your ported system into an aperiodic, in which case you need to decrease the size of the box, and plan on less low bass output, as there is no useful output from the port.

[wkhanna]

got it.

thank you, Maestro!