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Discussion Starter · #1 ·
I stuggled placing this question in the SVS EQ thread, but didn't want to derail the discussion, since I am not an owner yet. So I decided to start a thread to gain member's (much smarter and more experienced than myself).


Okay, here's my situation. My subwoofer set up consists of four DIY sealed subs with 12" ED drivers powered by a Behringer 2500 amp. They sit behind my couch (which is on a riser) on subdudes. I am using an Antimode 8033 to EQ the sound. I have taken some basic measurements using a Rives sub signal disc and a radio shack sound meter. Plotting out a graph shows I have a null at around 30. Here are my two considerations:


1) Get another sub to place near the front of the room, or in an area in hopes filling in the null. The other benefit is a forward firing sub adding some additional ommph to the bass track. Before selling my SVS dual sub, I placed it towards the front of the room with the DIY subs in the current set up. I could "feel" the bass more with this set up. Unfortunately, the SVS was just too big for the space and didn't fit into the WAF. I am looking at the SVS SB-12 Plus (their smaller sub).


2) The other option is to sell my antimode 8033 and buy the new SVS EQ and let the EQ help cure the null. This is under the assumption, the SVS unit will be more effective than the antimode in curing the null and getting a flatter response in my system.


As you can probably tell for my thought process, I'm not a big audio guyI'm more in tune on the video side. So if my ideas are making you roll your eyes, please not hesitate in sending my another direction than what's listed above. I apperciate any and all feedback.


Thanks

Ron
 

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Quote:
Originally Posted by rboster /forum/post/16856838


I stuggled placing this question in the SVS EQ thread, but didn't want to derail the discussion, since I am not an owner yet. So I decided to start a thread to gain member's (much smarter and more experienced than myself).


Okay, here's my situation. My subwoofer set up consists of four DIY sealed subs with 12" ED drivers powered by a Behringer 2500 amp. They sit behind my couch (which is on a riser) on subdudes. I am using an Antimode 8033 to EQ the sound. I have taken some basic measurements using a Rives sub signal disc and a radio shack sound meter. Plotting out a graph shows I have a null at around 30. Here are my two considerations:


1) Get another sub to place near the front of the room, or in an area in hopes filling in the null. The other benefit is a forward firing sub adding some additional ommph to the bass track. Before selling my SVS dual sub, I placed it towards the front of the room with the DIY subs in the current set up. I could "feel" the bass more with this set up. Unfortunately, the SVS was just too big for the space and didn't fit into the WAF. I am looking at the SVS SB-12 Plus (their smaller sub).


2) The other option is to sell my antimode 8033 and buy the new SVS EQ and let the EQ help cure the null. This is under the assumption, the SVS unit will be more effective than the antimode in curing the null and getting a flatter response in my system.


As you can probably tell for my thought process, I'm not a big audio guyI'm more in tune on the video side. So if my ideas are making you roll your eyes, please not hesitate in sending my another direction than what's listed above. I apperciate any and all feedback.


Thanks

Ron

If your 30 Hz "trough" is actually a "null", no EQ will correct it. You can't correct a true null with EQ. A true null is caused by a cancellation. Two waves arrive out-of-phase with each other and cancel. An EQ can only add power to the null, providing nothing but *more* cancellation. You use additional amplifier power and driver excursion with no audible benefit. The SVS AS-EQ1 will probably not even address your problem if it is a true null. (BTW, true nulls are usually narrow and deep and limited to a small listening area. Before you do anything else, measure the response at a few locations around the listening area using a high resolution measuring system, 1/12th to 1/24th octave, (the Rives disc is 1/3 octave), to ensure you are dealing with a true null.)


If the system doesn't sound up to your expectations, the best thing to do is add another sub, placed elsewhere. Can you move one of your DIY subs up front, or are they all in one box? The second thing to do is to add bass traps, (though, to be honest, bass traps will have very little effect at 30 Hz.)


Craig
 

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Quote:
Originally Posted by craig john /forum/post/16856952


If the system doesn't sound up to your expectations, the best thing to do is add another sub, placed elsewhere. Can you move one of your DIY subs up front, or are they all in one box? The second thing to do is to add bass traps, (though, to be honest, bass traps will have very little effect at 30 Hz.)

Craig

Or change the seating position to avoid the null.
 

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Quote:
Originally Posted by Kal Rubinson /forum/post/16857002


Or change the seating position to avoid the null.

Yes, that too.
 

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Discussion Starter · #5 ·
Thanks guys. I appreciate the information/suggestions, esp. from a couple of experts like yourselves.


I may have mis-spoke in calling it a "null"...since I couldn't define what a true null is, I should have stated dip in the signal at 30hz. Unfortunately, moving my seating around (aside from a couple of inches either way) is not possible.


I may need to borrow a sub from a friend to do some experimenting with placement of another sub and it's impact. What are the considerations when adding another sub? I would assume since the other drivers are 12" and the inclosures are sealed...I should try to stay with a similar sub? Any considerations when pairing another sub?


Thanks again for taking the time to read and respond.


Ron
 

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Quote:
Originally Posted by rboster /forum/post/16857257


Thanks guys. I appreciate the information/suggestions, esp. from a couple of experts like yourselves.


I may have mis-spoke in calling it a "null"...since I couldn't define what a true null is, I should have stated dip in the signal at 30hz. Unfortunately, moving my seating around (aside from a couple of inches either way) is not possible.


I may need to borrow a sub from a friend to do some experimenting with placement of another sub and it's impact. What are the considerations when adding another sub? I would assume since the other drivers are 12" and the inclosures are sealed...I should try to stay with a similar sub? Any considerations when pairing another sub?


Thanks again for taking the time to read and respond.


Ron

If you just want to clean up the "dip" at 30 Hz, then adding an additional sub with good output at 30 Hz is all you need. Place it so it fills in the null, turn it up till you get flat response at 30 Hz and you're done. This is the "Geddes" technique, (at least as I understand it.)


However, it's never that simple. If you fill in one hole, you may create another.


If you add a second sub with less output capability, it may "bottom" before the higher output sub reaches it's limits, thus limiting *system* headroom.


If you add a second sub with less bass extension, and you calibrate their combined level to be equal to the speaker levels, you'll effectively be turning down the sub with lower extension, thereby turning down the lowest frequencies.


In general, it's best and easiest to add another of the same sub. However, that doesn't sound like what you want to do. In that case, try to find another commercial sub that has the same LF extension, SPL output and overall FR as your current sub.


Craig
 
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