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Dealing with subwoofer Nulls

Hi @auxinput,

You wrote:

... I have a question on the Bag End. Have you actually used the Bag End E-Traps? I have a pretty good room and do not have any major bass ringing. However, I do have a huge hole around 80hz where bass just falls out (this is a room node where I’m sitting). The Double-Bass Array (DBA) configuration that is popular in Germany would probably solve my problem, but it is just not practical for me to do in my room. I have looked at general broadband absorption, Helmholtz resonators, membrane panels from GIK, etc. I tried a pair of GIK full Soffit bass traps, but I didn’t like them -- they seemed to suck all the life/excitement out of the room. I am curious about the flex-range limiter panel on their monster bass traps and the tuned membrane. I haven’t yet looked into spending money on this problem (maybe next year). My initial thoughts were to try the flex-range-limiter option. However, this Bag End E-Trap looks really effective. There is one review where the user was able to restore a big dip in the bass area. Other feedback indicates the Bag End cannot restore big dips - it can only reduce bass peaks/ringing. Do you have any experience with this? ...

You actaully can make nulls manageable with a bass trap or active devices. I do not have personal experience with the Bag End.

I will say that I think your problem with the bass traps was your EQ didn’t go far enough. :) Usually users try to go for flat, when they should go for a declining response, about 1-1.5 dB per octave.

Before going with a second sub, have you tried inverting the sub and your chair? :) Here are the steps I recommend:

1. Put the bass traps back in
2. Place the sub where you listen, then use a measurement microphone to scout possible locations. Wherever the sub’s output is most full and even is the best place to put the sub.
3. EQ the sub so that it has a dropping response from 16-20 Hz. Approximately 1-2 dB/octave will be your ideal.

Best,


Erik
erik_squires

Showing 5 responses by erik_squires

erik_squires OP
16,591 posts
 
Hi everyone,

I'm not sure if it's clear, but the key to bass traps is that they work in combination with EQ. Not either or.

Also, I'm not sure if you meant to say it this way or not but it sounds like you placed your subs symmetrically. They probably benefit most from being assymetrically placed. Assuming one of them is near ideal, but you still suffer the 80 Hz null, try the idea of putting the second one in the listening location, and try to find the place where it produces the most fill at 80 Hz. It may be that it works best next to or behind your listening location even. :)

Best,

Erik
erik_squires OP
16,591 posts
 
And finally, now that the coffee has cut in, I would consider active room cancellors my last option. In order of my personal preference:

  1. Sub + Bass Traps + EQ
  2. Dual or Quad subs + Bass Traps + EQ
  3. Dual Subs + EQ
  4. Single Sub + EQ
  5. Active room canceller (i.e. Bag End)
The Bag End type of solution is last because A - It's another device that has to be placed properly and powered on. Why not have a second sub instead? and B - Limited in benefits to a couple of room modes. Bass traps and EQ are much broader based.

Best,

Erik
erik_squires OP
16,591 posts
 
Grrr. I cannot type cogently I guess.

By tilting I mean tilting down. So an example target curve:

16 Hz - 90 dB
32 Hz - 88 dB
64 Hz - 86 dB
erik_squires OP
16,591 posts
 
Grrr. I meant when you EQ, find your lowest reasonable output. Somewhere around 16 - 30Hz. Take that as your starting point, then EQ between that point and the upper limits of the sub's output. For me that would be 16 Hz to 120 Hz.

The tilt is up to you, but I find flat TOO flat. Somewhere around 1 to 2 db/Octave gives me the best movie and music sound possible.
erik_squires OP
16,591 posts
 
By the way, WITH and only with bass traps it becomes possible to effectively, but not completely, deal with nulls and ringing modes with a single subwoofer and EQ.

I find this the neatest (as in least messy) and most cost effective solution. However those with lots of money and space may go with 2 or 4 subwoofers to do the same. That's fine too, but it's out of my budget.

Those purists who insist that all EQ is bad haven't heard how magnificent it can be done.

Best,


Erik
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