# subs facing each other across trunk ok, or a no,no?



## tomk1 (Mar 4, 2002)

is there any cancelation or is it good to go? any help would be great! http://****************.com/smile/emthup.gif


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## cheades (Oct 19, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (tomk1)*

Its not the best idea, the speakers would be fighting each other a little bit. Much better if you can just have them both aiming the same way.


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## tomk1 (Mar 4, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (cheades)*

but 2 subs facing each other will still pound WAy more than a single right?







http://****************.com/smile/emthup.gif


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## Lexi (Jun 18, 2000)

*Re: subs facing each other across trunk ok, or a no,no? (tomk1)*

No necessarily. It really depends on the amount of cancellation you get. Theoretically if the waves are in exact opposite sync they'll completely cancel one another out . That's probably not going to happen but I really wouldn't face subs against one another . At the very least angle them away from each other .


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## Non_Affiliated (Feb 12, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (Lexi)*

At a wavelength of 11.3 Ft for 100Hz, and 113 Ft wavelength for 10Hz. good luck havinging enough phase shift to cancel out the signal. The only time this becomes an issue is when the program material (Music) has the bass frequencies recorded 180 degrees out of phase, and in stereo.
Your pretty much safe placeing the subs across the trunck from each other.


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## zerind (Feb 16, 1999)

*Re: subs facing each other across trunk ok, or a no,no? (Lexi)*

You can also mess with wiring one sub out of phase so that the waves don't cancel as much. Its more or less trial and error...but mess with the phasing of the subwoofers too.


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## College Dub (Apr 4, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (Non_Affiliated)*

quote:[HR][/HR]At a wavelength of 11.3 Ft for 100Hz, and 113 Ft wavelength for 10Hz. good luck havinging enough phase shift to cancel out the signal. The only time this becomes an issue is when the program material (Music) has the bass frequencies recorded 180 degrees out of phase, and in stereo.
Your pretty much safe placeing the subs across the trunck from each other.[HR][/HR]​Well, he's got my vote







I'd go with his knowledge and say it's not a problem having the subs face each other.
-Alan


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## timmybgood (Dec 12, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (College Dub)*









its definatly not a problem


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## Alpine Mike (May 13, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (tomk1)*

Phase is a problem no matter which way the subs are facing. Just make sure that you have the speakers wired correctly. Facing the subs at each other is no problem at all. In fact by firing the subs at each other it is claimed that you get an additional 3db of output.


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## tomk1 (Mar 4, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (Alpine Mike)*

Thanks everyone...Now I can start planning my sub inclosures and not have any doubts about it being worth while or not http://****************.com/smile/emthup.gif


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## Psychoman (Oct 24, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (tomk1)*

Actually facing 2 subs at each other the reversing phase on one would be bad outcome.. that would be like one woofer goes out displacing air from its cone while the one across trunk so conviently goes in to help accept that air.. It would be a see saw of air across trunk with much audio loss.. The subs aren't gonna fight each other because of the wavelength and because of the amount of air they effect.


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## speaker (Aug 12, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (zerind)*









Zerind:
I have to take you to the woodshed on this one. If you have (2) subs in your car and you wire one out of phase* relative to the other, you will have a huge net loss in bass output. It will not sound good, it will suck. However, if you wire both subwoofers out of phase relative to the front speakers, you can sometimes improve the integration between the front speakers and the subwoofers. Perhaps that is what you meant?
As far as subwoofers facing across from each other (or facing up, away, down, to the back, one at 45 degrees and one at 60!), don't worry about it. Pressure is pressure. At the long wavelengths we are talking about here, the difference will not be noticeable. However, If you load them up facing into the rear corners of the trunk/hatch area, you will notice some significant differences in output and/or sound quality good or bad. You will also notice a lesser (but still discernible) difference as to the woofers geographic position in the trunk/hatch area. In other words, you MAY discern more output when the subs are all the way to the back or to one side than snugged up against the seat. Lastly, losses occur when the subwoofer enclosure is not anchored firmly to the vehicle. If it is a premade enclosure and it comes with brackets, use them. It it is a custom built-in, make sure it does not move around when being used. If you put enough power into a sub box to get it to move under listening conditions, some of the energy is being wasted moving the box rather than just pushing air. That is not real efficient.
What does all of this mean? In the case of relative phase, experiment with one hook-up and then the other. One may sound better. Some amplifiers have variable 0-180 phase controls. Those are even more useful because in the vehicle, phase might be 90 degrees out on the sub and there is no way to correct with 0 or 180 settings. In the case of subwoofers sounding different in different parts of the vehicle, experiment before you mount them permanently.
speaker

*For those who do not know and may not be inclined to ask, phase can refer to any number of things. Relative phase is the phase relation of one speaker to another. Electrical phase relates to how the speaker (or source) is electrically connected (wired) to the amplifier. Assuming that the source into the amplifier is in phase, if the amplifier + is connected to the speaker + and so on for the - of each, you would say that it is electrically in phase. It the amplifier + is connected to the speaker - and vice versa for the other 2 connections, you would say that the speaker is electrically out of phase. Acoustics phase is the is similar to relative phase in that you are measuring the actual sound output of one speaker versus another at an arbitrary position (driver's seat).








quote:[HR][/HR]You can also mess with wiring one sub out of phase so that the waves don't cancel as much. Its more or less trial and error...but mess with the phasing of the subwoofers too.[HR][/HR]​


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## Psychoman (Oct 24, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (speaker)*

Yeah thats what I was trying to say.. I just didn't clarify the last sentance very well..


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## illstyle (May 5, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (Psychoman)*

from my experience with comb filtering, you should be safe because any noticeable cancellation in your situation would be higher frequencies (ie: higher than your sub woofers will be playing).
you should be alright.


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## illstyle (May 5, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (illstyle)*

COmb Filtering:
Any time two speaker components cover the same area with the same program material, interference is possible.
Comb filtering is a special kind of destructive interference. When identical drivers fire identical program material, phase cancellation will occur at regular frequencies intervals. Here's a quick guessing method to determine intervals : 
1. Measure the distance between source speakers. 
2. Calculate (or look up) the frequency whose wave length is equal to the distance between the speakers. (1130/distance)
3. Divide this Freq. by 2.
4. Make a list of Freq. x 2 until you exceed 20,000.
Those are the destructive points in your audio spectrum.
Example.
2 speakers 3 ft apart.
wavelength = 3 ft
Freq. = approx 377hz (1130 speed of sound/ distance 3)
Fundamental comb filter = 188.5 (377/2)
Comb Filter Chart - holes in your audio spectrum.
188.5Hz
377Hz
754Hz
1508Hz
3016Hz
6032Hz
12064Hz
24128Hz
Now.........
2 speakers approximately 3 ft apart would not exhibit comb filtering below 188.5hz. A Sub woofer should not produce sound above 250hz. so you will have one gap in your sound spectrum.. so technically subs 3 ft apart WILL give you interference.. but, i doubt you would really notice very much unless you purposely look for that gap.
But....
Lets say two bullet tweeters are 6 inches apart.... Ha Ha Ha!

i hope that helped a bit.



[Modified by illstyle, 10:09 PM 5-16-2002]


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## Philthy-dls (May 17, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (illstyle)*

It not a problem to mount them that way... I couldn't imagine anyone playing their subs above 80hz, and anything below that is just pressure.


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## JoeBoxerVR6 (Jun 8, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (Philthy-dls)*

My subs are audiable and felt at 18 hertz, at anything lower than that, your just listening to the wind blowing. But that's a sealed box. At around 32-35 hertz, everyone's alarm is going off.


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## Non_Affiliated (Feb 12, 2002)

*Re: subs facing each other across trunk ok, or a no,no? (JoeBoxerVR6)*

quote:[HR][/HR]My subs are audiable and felt at 18 hertz, at anything lower than that, your just listening to the wind blowing. But that's a sealed box. At around 32-35 hertz, everyone's alarm is going off.[HR][/HR]​Don't take offence to this, but if you here wind in a sealed box, it's not sealed real well. Granted your gonna here a little bit due to the speaker cone s velocity, but not much.


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## philthybenz (Sep 3, 2001)

*Re: subs facing each other across trunk ok, or a no,no? (Non_Affiliated)*

I think he was referring to cone noise, (wind) and sealling your box won't do diddly for cone noise...
and you can't hear 18hz... but you sure can feel it!


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