spirovious
Well-Known Member
Anyone mentioned it?
Avepa - Zypher's Z-21 Active Subwoofer
- Thread starter hifiashok
- Start date
hifiashok
Well-Known Member
Since Kanwarji is on this thread, best for him to comment (IMHO)?
Even if they are all playing in phase!!
theironhorse
Well-Known Member
some one mentioned earlier that it will be close to SVS-PB12
Do you expect placing the two subs in opposite direction to each other and still maintaining the phase..... ????
In that case we need to reverse the phase of one of the subs.
In non stacking mode in front firing, alot depends on the room itself. Ripple effect is prominent.
Why don't FM's who intend to buy such a sub contact Kanwarji directly, instead of asking others who themselves don't know the answer
If anyone interested, he/she can PM me.
If the sound signal is reaching both the subwoofers at the same time and the phase settings on both the subs are similar and the drivers are firing at the same time, of course I would expect them to maintain phase. Why not?
How will the distance affect the phase of the sound wave?
As per my understanding, sound propagation itself is through ripple effect. What is the ripple effect you are referring to?
Edit: Kanwar hope you wouldn't mind some OT. If you feel my posts are cluttering this thread, we can take the discussion offline or via PM.
If the subs have the same phase settings, and if they are facing each other, there would be a cancellation, I think.
If they are facing away from each other, I'm sure the bass would sound "confusing" (bass going <------- and ------->), even though bass is supposed to be non-directional. I don't know how to express this in a technical way
Reversing the phase of one of the subs would keep them both in the same phase, and the bass should sound coherent.
@Kanwar Do keep the posts here, if hifiashok is ok with it, or please move them to a different public thread. This is interesting information
If they are facing away from each other, I'm sure the bass would sound "confusing" (bass going <------- and ------->), even though bass is supposed to be non-directional. I don't know how to express this in a technical way
Reversing the phase of one of the subs would keep them both in the same phase, and the bass should sound coherent.
@Kanwar Do keep the posts here, if hifiashok is ok with it, or please move them to a different public thread. This is interesting information
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The vibration of the subwoofer cones would produce sound. The forward movement of the cone pushes the air molecules in front of it which in turn push those in front of them so on and so forth. Likewise, the backward movement of the cone would pull the air molecules in front of it which would in turn pull those in from of them. This whole process would create waves carrying sound energy. The forward movement creates the wave (of higher pressure in relation to the air around it) and the backward movement would create a trough (of lower pressure in relation to the air around it) Thus the sound gets propagated through the air.
In an open area, the amplitude of these sound waves get progressively weakened as they keep losing energy in the process. Hence sound can travel only a finite distance and the loudness gets reduced gradually and gets fizzled out eventually. However in an enclosed space, these, especially the LF sound lingers on, reflected back and forth by the room boundaries.
Now lets come to the issue. The vibrating cones of the two subs facing each other receiving the same musical signal and operating in phase would produce the sound waves in phase but from opposing directions. When these meet in the air, they both would push against each other thereby weakening in the process. However they would not be cancelling out each other. That would happen only if the subs are playing 180 degrees out of phase.
Hope my point makes sense to you.
Yes Capt., it does. What I was confused about is this:
If two subwoofers are facing each other & firing at each other (S1----><----S2), and both have the same phase setting, aren't they effectively 180 degrees out of phase (= playing in opposing phase)?
Shouldn't we reverse the phase of one of the subwoofers (say keep one at 180 degrees & keep the other at 0 degrees), while keeping them facing each other, so that they are both in phase?
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I don't think so. Look at the following illustrations:
Subs in phase and in opposite directions: [] ) ) ) ( ( ( []
Subs out of phase and in opposite directions: [] ) ) ) ) ) ) []
In the first illustration, when the sound waves meet, they would not cancel out each other but push each other. However since they are of same amplitude but in opposite directions, this pushing would result in dissipation of energy (to an extent) and they continue in their paths with reduced amplitudes.
In the second illustration, since they are 180 degrees out of phase to each other, when the sound waves meet, they cancel out each other. This results in null point at this particular location.
If the sound signal is reaching both the subwoofers at the same time and the phase settings on both the subs are similar and the drivers are firing at the same time, of course I would expect them to maintain phase. Why not?
How will the distance affect the phase of the sound wave?
As per my understanding, sound propagation itself is through ripple effect. What is the ripple effect you are referring to?
The ripple effect i am talking about is this: Think of throwing a single stone in the pond, the circular ripples will emerge moving outwards, now think of throwing 2 similar stones at same time, at certain point they tend to cancel the the ripple effect from each other, hence cancellation. This analogy is just for understanding of non stacked subs and it holds good for open space mostly, because in open areas you need stacking of multiple subs whereas in an enclosed area things change considerably due to the presence of room modes.
Intensity of wave changes with distance not the phase, phase either adds up or gets subtracted.
When the 2 waves of same phase collide from opposite direction, cancellation does happen which is evident from the fact that the SPL level at that point actually decreases, because energy of the waves get disperesed. I have experimented this alot in real world, the decrease is sometimes as much as 6dB in open space, but when same thing you do in closed spaces such as in room, the scenario changes due to the excitation of room modes .
Recently i have done experiments with stacked subwoofers vs multiple subwoofers. There are lot of pointers in play which are deciding factors for multiple subs placed at different position vs stacking at one location. Each has its own benefits and drawbacks aswell. With stacking you get SPL boost and with multi position placement you get better rejection of excited room modes but it drastically reduces the SPL.
For music listening, a single or pair of subs is more than enough. Again it depends on the personal preference also + room size and shape.
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Ideally one should reverse the phase in order to get full boost and minimum cancellation in open space. In reality in closed spaces, the presence of room modes makes the situation a complete mess. Also the amount of cancellation in same phase operation of subs depends on the distance between them. More the distance lesser the cancellation but more the suppression of room modes. If you reverse the phase, you get the SPL boost but same time can get equally boomy due to room modes adding up to the response as well.
Ok you are terming it "Cancellation" and I'm terming it "Weakening" but we are both saying the same thing. Your experiments also corroborate what I meant by weakening i.e. reduction in amplitude.
IMHO the term "cancellation" would be apt to describe the phenomenon of two sound waves,180 degrees out of phase, colliding with each other. That would result in annihilation of the sound itself, the way it gets done in 'Noise Cancellation Headphones"
I was going through a link provided by Thad on the other thread: Bass Trapping Ideas for Non-Ideal Spaces | Audioholics
Quoting from the article:
This is what would cancellation be referred as.
let me clarify a bit more:
Best example of cancellation would be two subs placed next to each other (side by side) and driven out of phase. This will result in almost greater than 12dB of reduction in bass.
Next comes the scenario of two subs facing each other driven in same phase. Here the cancellation will occur but at much lesser extent, its more like dispersion of energy and filling the empty pockets. You will get 3-6dB decrease in SPL depending on the distance as compared to stacking the subs at one point which can boost the SPL.
Best example of cancellation would be two subs placed next to each other (side by side) and driven out of phase. This will result in almost greater than 12dB of reduction in bass.
Next comes the scenario of two subs facing each other driven in same phase. Here the cancellation will occur but at much lesser extent, its more like dispersion of energy and filling the empty pockets. You will get 3-6dB decrease in SPL depending on the distance as compared to stacking the subs at one point which can boost the SPL.
We are on the same page Kanwar.
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anm
Well-Known Member
^^^ did you mean on the same "phase"?
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