Sub Placement

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DJGoodSteve

DJGoodSteve

New DJ
Mar 10, 2012
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Boulder, CO
While reviewing all of the subwoofer reviews out there, I occasionally ran across discussion of two subs canceling each other out. I believe the term was 12db(?) cancellation. I'm wondering if I should be worried about this when placing my (elx 118p) subs? When it was mentioned, the recommendation was to place both subs next to each other for maximum performance. If this is ideal, I wonder about all those setups where a sub is place on either side of the booth with a pole and top cabinet. Is that very common setup sabotaging the output? Thanks!
 
Recommended is to couple both subs in center of your setup and Tops on left and right side. Coupling the subs will gain an extra 3db, so I've read. You would then be running 2-way with mono subs.

If you choose to pole mount the mains on top of subs, then make sure they are at least 15-20 feet apart. I believe Houston will be coming on line as soon as he sees this thread.

Check out DBXPro.com and search for Sub Placement in the threads. There are a couple of excellent threads that talk about what you have asked.
 
Given a mean subwoofer frequency of around 50-60Hz, the wavelength of the sound is about 20 feet. If you place 2 subs about 10 feet from each other and stand in front of one of them, the two waves will hit you at 180 degrees out of phase and will cancel each other for the most part. So the trick is to place the subs where the cancellation is minimized. Spreading them farther than 10' will help as will putting them together. Some subs have a phase switch on them to adjust for this as do some crossovers (in fact some allow setting in finer increments). As Art said, putting them together MAY bump up the gain, but that also depends on sub design (not a given). I don't think you will see a lot of difference. If you plan to mount the tops on stands above the subs, go for it, just make sure you have them spread enough to minimize the phase cancellation (15-20' should be fine).
 
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The object of putting two subs together is to presumably increase the DB. If you have enough DB as it is, there is no need to squeeze out any more by coupling. Like Steve said, a nice healthy spread about 25 feet or more apart is great. If you are using poles on top of subs then that will make for ease of placement. If you are using tripods, then putting the sub in front of the tripods help reduce the likelihood of tripping.
You can also place the sub kind of inside two of the tripod legs, as than tends to lessen the footprint.
I would NOT recommend putting subs under a table with tablecloth over the whole thing. I would not recommend speakers on each end of a six foot table.
 
Great advice as usual guys. Thanks. I did a quick Google image search to prove what I constantly see... which is contrary to your advice. Apologies to these poor guys from Long Island... they have a great website and setup... but it appears they have those subs at either end of the six foot table which I see constantly. I will follow your advice and avoid this.

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Yes .. that placement is a bit close, though there are certainly times you have no choice. When speakers are that close, you can get phase issues from both the subs and the tops. As long as you understand what might happen to the sound, you can play around with both placement of the speakers and phase adjustments to minimize issues.
 
I got in late on this and have always coupled or followed the 18 foot rule. Also when coupling they dont have to touch phytsically they can be seperated minimally as in inches without losing that couple.
 
DJGoodSteve said:
Great advice as usual guys. Thanks. I did a quick Google image search to prove what I constantly see... which is contrary to your advice. Apologies to these poor guys from Long Island... they have a great website and setup... but it appears they have those subs at either end of the six foot table which I see constantly. I will follow your advice and avoid this.

View attachment 26190
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If you can for a minute picture that same setup minus the speakers, it will give for a nicer presentation, less clutter and congestion, not to mention hearing problems for the DJ. With the speakers spread out they tend to blend more into the decor. So as others are saying, you think of sound quality and aesthetics. (However, like Steve said, sometimes you have no choice)
 
I agree Canute the hearing issue is the worst part of that setup. I have hearing issues not having my speakers that close but working around loud machinery and sound before they invented the ear plugs and or regulations governing legal levels etc. I am a big advocate for protecting your valued hearing tools very important in this industry. The clutter is also a consideration along with locating proper and ultimate sound where it most likely should be contained to.
 
Great advice.

I'd like to add some old news: Bass bin placement in a room isn't critical since the longer wavelengths are onmidirectional. You can set your bass cabinets anywhere they'll be out of the way. Think of the woofer cabinet on your home theater rig. You get the lows warmth no matter where the cabinet is located in the room. :)

We used a 50' Speakon cable to feed our bass bins with a Y-connector at the end to split to the bins. Most times they were on stage, centered at our rig but on occasion we placed them off to the side.
 
Fred Wright said:
Great advice.

I'd like to add some old news: Bass bin placement in a room isn't critical since the longer wavelengths are onmidirectional. You can set your bass cabinets anywhere they'll be out of the way. Think of the woofer cabinet on your home theater rig. You get the lows warmth no matter where the cabinet is located in the room. :)

We used a 50' Speakon cable to feed our bass bins with a Y-connector at the end to split to the bins. Most times they were on stage, centered at our rig but on occasion we placed them off to the side.
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The only concern there would be the relative distance between the listener, the tops and the subs. If the distance to the tops from the listener and the distance to the subs from the listener are more than a few feet different (for example placing the sub in the back corner 20' behind your table and the tops 20' apart even with your table) you will have the issue that the sound from the tops may be out of sync with the sub (arriving at different times). Here, the proper way of dealing with it is adding delay to the tops so the sound wave arrives at the main listening area at the same time.

I need delay on my subs, even when the tops are directly above them, as they are horn loaded, effectively making the driver 7' behind the tops in arrival time, so the tops have to be delayed about 9ms to prevent the sound from getting muddy. Same principal if I move them in front of or behind the tops.
 
Due to the extremely long wavelengths, subs interact with entire room in many, it not most setups. A VERY rough rule of thumb is to either have subs against a wall, gaining another 3db of efficiency, or make sure they are more than 10 feet away from the wall. Keep them on the floor and do not put them on a raised stage. If you are setup near a corner, maximum efficiency is normally a corner loaded cluster where the 3rd boundary adds another 3db. Yes, that's a total of 9db, 3 for paired, 3 for the side wall and 3 more for the rear wall. This is not something to be ignored!

On the other side of the coin, in some situations it is better to separate the subs when you have weird room acoustics which create too much bass at certain frequencies or when you are on a stage and the "backwave" of a center cluster in front of you makes you sick. (That would typically be a room you have been in before and had problems.)

Also, not all subs are omnidirectional. Horn loaded subs are somewhat directional and help noticeably when setup in front of you. In fact, with some science you can create a fully aim-able cardioid pattern sub array.

Lastly, when the subs are not stacked under the tops you may want a means of delaying the signal to re-align the frequencies, espcailly if you are corner leading. However, the re-alignment is set at a single point and much like the infamous automated "room eq" processes, while it is "correct" at that single point, the rest of the space is not correct. You really want to set it up to get the best average sound throughout the entire space.
 
ahoustondj said:
If you can for a minute picture that same setup minus the speakers, it will give for a nicer presentation, less clutter and congestion, not to mention hearing problems for the DJ. With the speakers spread out they tend to blend more into the decor. So as others are saying, you think of sound quality and aesthetics. (However, like Steve said, sometimes you have no choice)
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I think this may be the nicest way I have seen you put it Canute. Cheers to you.

:)
 
Sub placement and the cancelling of frequencies in almost every case will never be noticed by anyone. There are 10 people in this thread including me who might come up to you and mention something about it. I've never heard the sound from a speaker disappear before so if its in the room and placed in a somewhat reasonable way it should be just fine. You can put that setup in the picture in any smaller room and be just fine. In situation where DB is critical then yes....couple, wall, or corner load. Good questions and good answers on here.
 
JT I hate to disagree with you here I have experienced it on numerous occasions. Once even with my Dynacord system. Didnt seperate them enough with the tops poled over them and NO Bass out front. Have also on occasion on a high enclosed stage well in fact there was Bass but only out the back side and absolutely lost in the room or out front.
 
Jon Tuck said:
JT I hate to disagree with you here I have experienced it on numerous occasions. Once even with my Dynacord system. Didnt seperate them enough with the tops poled over them and NO Bass out front. Have also on occasion on a high enclosed stage well in fact there was Bass but only out the back side and absolutely lost in the room or out front.
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For subs that have it, switching the phase/polarity on 1 sub would usually help.
 
Jon, did your guests notice? This is what I meant from my post..... If space allows do what's right every time. You and I agree on that. Considering the average set of ears in an average room for most wedding receptions and attendees...

600 kids in a gym is a different story.
 
likely they didnt notice but I may as well not setup the sub in that location or brought it as it had pretty much zero presence.
 
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