Bag End E-Trap

pandamonk said:
Hmm sounds interesting, but isn't the concept just the same as using EQ to sort room problems?
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It's not the same as using EQ, but it suffers from the same basic problem: It improves only one location in the room, versus passive bass traps that help everywhere. But unlike EQ, an active bass trap has the potential to improve nulls and reduce ringing.

Another limitation of this particular trap is it can be tuned to work at only two frequencies. But all rooms have problems at all bass frequencies.

--Ethan
 
as Ethan points out, its a point solution - you still need the room treatments for broadband control but if you need to deal with one particular frequency or two, and space or design considerations, the e-bag seems like a decent option if its cost effective...
 
lol, yeah I figured they had their place but wouldn't be of that much use in practice. I just thought it was an interesting device...hadn't seen one before.

Thanks for the info, Ethan.
 
Ethan Winer said:
It's not the same as using EQ, but it suffers from the same basic problem: It improves only one location in the room, versus passive bass traps that help everywhere. But unlike EQ, an active bass trap has the potential to improve nulls and reduce ringing.

Another limitation of this particular trap is it can be tuned to work at only two frequencies. But all rooms have problems at all bass frequencies.

--Ethan
Click to expand...
I meant your point that it improves only one location. I don't really understand the other part.
 
the WSDG paper showed them only using 2 in a small CR to manage a couple of frequencies that were problematic in the producer seat on the back wall - the rest of the CR was balanced by design for the mix position and at the last minute needed the change. the step-by-step adjustment process was interesting in that the location of the units versus their target areas.... didn't realize they're a grand each...

the devices can only be tuned to a given set of frequencies, they're not going to solve broadband issues. i guess in theory if you built your room out of giant electrostatic speaker panels you could have complete room control :-)
 
pandamonk said:
I don't actually understand how the E-trap works, and how it can reduce ringing.
Click to expand...

There are two basic types of bass traps - velocity absorbers and pressure absorbers. Fiberglass and acoustic foam are the former, and the absorption happens as the waves tunnel into the tiny fissures of the material and are converted to heat. A pressure absorber works on an opposite principle, and is basically a "shock absorber" for sound waves.

The Bag End trap is a pressure absorber. I haven't taken one apart, but it has a built-in microphone that senses the oncoming waves, and a panel of some sort (possibly a big loudspeaker) that sends a "counter wave" back toward the oncoming source wave. The wave sent back by the E-Trap has the correct phase and level to counteract the original wave.

So unlike EQ that is open loop (merely inserted into the signal path) and can change only the frequency response, the Bag End trap has the potential to actually damp a room's resonances because it truly absorbs the reflections.

--Ethan
 
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