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Positioning subwoofer
Old 28th January 2007
  #1
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Positioning subwoofer

Does anyone have any tips or links for positioning a subwoofer? When I first positioned my NS-10's and sub the bass was thumping pretty well. Then I rearranged my room, moved everything to different spots, but eventually went back to where I started. Now I can't hear the sub as well and I'm pretty sure I'm having a problem with phase. Thanks!
Old 28th January 2007
  #2
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Bob Katz wrote an excellent article in the back of my Avocet manual. Take a look at that.

Crane Song Avocet

Regards,
Bruce
Old 28th January 2007
  #3
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Make sure that the sub is not interacting with the bottom of a desk or the console. The closer it is to a wall will boost the low end. Also, run a few different low frequency sine waves and walk around the room with a dB meter. You will find nodes and antinodes. Move the sub until you get the best compromise for your mix position. Tune the room with bass traps. Low frequencies are a beeotch to tame, but you must if you are going to rely on that room for mixing anything.

2 subs are much better than one. Here are Floyde Toole's preferred positions for subs:
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Positioning subwoofer-subs.jpg  
Old 28th January 2007
  #4
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Hi.

Read this thread and its links. It was very helpful for me!

https://www.gearslutz.com/board/so-much-gear-so-little-time/91113-hi-all-acoustics-physicists-im-getting-paranoid.html
Old 29th January 2007
  #5
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How do I know if my desk is interfering with the sub? Right now its on an Auralex Gramma sub riser. I have 5 bass traos placed around the room and the bass is somewhat under control. Although the bass is screwey now, I know it's in an ok spot in the room (since it sounded much better before I moved everything). My new situation has the desk in roughly the same spot, but the speakers are wider apart than before. Will check out those articles now. Thanks, everyone!


Also, when I did a quick test using a pink noise generator filtering everything above 150. my rat shack db meter showed 83db at ear level and 97db around mid-calf pointing right at the subwoofer
Old 29th January 2007
  #6
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Ethan Winer's Avatar
 

Quote:
Originally Posted by Hope209 View Post
Does anyone have any tips or links for positioning a subwoofer?
When I bought a Carver Sunfire for my home theater a few years ago, I tried a variety of places. Then I looked in the manual heh and it said to put it in one of the front corners. Bingo, that was clearly the best place. More recently I got an SVS PB12-Ultra/2 subwoofer and noticed that its manual also said a front corner is best. By then I didn't even need to experiment. I put it there and it's even more fabulous than the Sunfire.

That said, a front corner is clearly the loudest location, but it won't be the flattest unless you have a fair number of bass traps. Loud works for me <smile>, but I also have 40 traps in my living room home theater and they reduce the problems (peaks, ringing) you get with corner placement.

The only way to know for sure which place is best is to measure the response. But you need to measure to a high resolution such as 1 Hz intervals. This can be time consuming because moving the sub even an inch or two can make a real difference. So you end up measuring, moving, measuring, moving, and so forth for the better part of an evening.

One useful method is to put the subwoofer at the listening position on a chair, then play some bass-heavy music and crawl around on the floor listening for where the bass is the most even. Once you find the best place by ear, put the subwoofer there. One problem with this is the key of the music affects what you hear. If the music has tones that align with the room's modes, then this method can work pretty well. But if the music is in a key that doesn't excite the room modes, then other music that does excite the modes may sound unbalanced. One solution is to use pink noise instead of music. This short article on my company's web site explains this in more detail, and there's a low frequency filtered pink noise MP3 file you can download:

www.realtraps.com/lf-noise.htm

But again, the only way to know for sure where the low frequency response is flattest is to measure.

I hope this helps.

--Ethan
Old 30th January 2007
  #7
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Sub-bass is non-directional, right? But don't I want it in the center of my stereo image? How does this work if the subwoofer is in a corner of the room?

The info on that Crane Song manual was very helpful but I still don't quite know what I'm doing. I moved my NS-10's closer together by 5'' and it was a very big improvement. I can hear the bass much better, but it's REALLY thumping a little over four feet to the left of my chair (the rest of the room is very even, though). I set up the angle of the tweeters to the chair solely on how it sounded, it isn't set up in an equilateral triangle. Basically I just want to grab that bass and shift it over four feet to the right...how would that be possible?

Since the bass sounded very good before I moved everything around I think it's in an OK spot in the room. Plus, when I moved NS-10's just a few inches closer together I could hear the bass much more clearly
Old 30th January 2007
  #8
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Ethan Winer's Avatar
 

Quote:
Originally Posted by Hope209 View Post
Sub-bass is non-directional, right? But don't I want it in the center of my stereo image? How does this work if the subwoofer is in a corner of the room?
If it's non-directional, then by definition you can't tell that it's over in the corner!

Quote:
when I moved NS-10's just a few inches closer together I could hear the bass much more clearly
Again, the frequency response of any sub in any room changes drastically with placement. This is the real issue.

--Ethan
Old 30th January 2007
  #9
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Quote:
Originally Posted by Ethan Winer View Post
If it's non-directional, then by definition you can't tell that it's over in the corner!
Just to a quick comment...

...It is important to point out that subwoofers are not "non directional" they are omni directional.

Here is a link to an article on our website which explains how we perceive bass and how our brains processes location cues from our ears.

http://www.abluesky.com/asp/catalogu...asp?linkid=114

Cheers!
Old 30th January 2007
  #10
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Ethan Winer's Avatar
 

Hi Pascal,

Quote:
It is important to point out that subwoofers are not "non directional" they are omni directional.
Excellent point, thanks for clarifying.

Also, subwoofers and low bass sometimes can seem directional, but it's usually either distortion or rattles and buzzes in the room.

--Ethan
Old 30th January 2007
  #11
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Quote:
Originally Posted by Ethan Winer View Post
Hi Pascal,



Excellent point, thanks for clarifying.

Also, subwoofers and low bass sometimes can seem directional, but it's usually either distortion or rattles and buzzes in the room.

--Ethan
True. This is something I mention in the article linked above...

Cheers!
Old 30th January 2007
  #12
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Cojo's Avatar
 

Quote:
Originally Posted by Ethan Winer View Post
Also, subwoofers and low bass sometimes can seem directional, but it's usually either distortion or rattles and buzzes in the room.

--Ethan
I've also noticed that low bass from a sub can seem directional because of the fact that the bass gets louder as you gets closer to the sub. If the sub is centered this is not a problem but if it's of center then it can feel unnatural if you move around ever so slightly.

I've also noticed that this "of center effect" got reduced when I put some traps in my room.
Old 31st January 2007
  #13
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Thanks for all the great advice, everyone! I actually have one extra RealTrap that I could place in my room....I tried moving it to the bass-heavy spot last night but didn't experiment too much.

So is there a way to move the sub in correlation with the NS-10's to shift the bass to the right? When you change the angle of nearfields it adjusts the phantom image that "appears" in front of you, right? So is it how the nearfields and sub are interacting that is making the powerful bass to the left of my desk, or is it the room and desk interacting with the sub? Sorry if this doesn't make sense...
Old 31st January 2007
  #14
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you're kidding right?

Quote:
Originally Posted by Ethan Winer View Post
there's a low frequency filtered pink noise MP3 file you can download:

www.realtraps.com/lf-noise.htm
You would be better off getting an uncompressed pink noise file. I don't even want to think about how MP3 compression mauled the necessary and true nature of a pink noise generator.
Old 31st January 2007
  #15
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Ethan Winer's Avatar
 

Quote:
Originally Posted by hociman View Post
You would be better off getting an uncompressed pink noise file. I don't even want to think about how MP3 compression mauled the necessary and true nature of a pink noise generator.
For the purposes of that article there's no problem using an MP3 file. All that matters is having uniform frequency content, versus trying to use a music CD which has only those frequencies in the key of the song.

--Ethan
Old 31st January 2007
  #16
Sub placement according to Genelec

I listen to a surround talk with people from Genelec speaking a few years back and the main advice was to put the sub, next to a wall or 5m from any wall! I guess it´s down to wave lenghts and the need for big rooms or to quote Phillip Nowell? "A big boxer usually beats a small one" for reproduction of lows. /Toby
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