Hi All,
I am such a noob that I don't even know what I don't know so please forgive me these really stupid questions.
My current sub (ASW610XP) with it's 10", front firing, driver has a seizure on it's plinth every time it tries to convince me that there's a helicopter flying through my lounge (and all of that paper that I stack ontop of it falls off).
This is obviously because the driver is able to deliver enough kinetic energy to move the enclosure laterally (no carpet spikes being used to protect my damage deposit). So, to me, it makes sense that a down firing enclosure would reduce the lateral movement of the enclosure (provided that the enclosure was suitably heavy). But I suspect that the driver would still cause the enclosure vibrate, unless the enclosure is massively, massively, massively heavy.
I've seen other subs that had a plinth that was attached to the enclosure (and the driver fired down at the plinth); my guess is that this kind of setup would further reduce the vibration of the enclosure (but having never seen one up front, I really don't know)
So my questions:
1. Is there a way to make a zero vibration enclosure for a sub that I want to move prodigious amounts of air? I want to transmit absolutely no vibration at all from the driver to the enclosure.
2. LFE is radial; so if I built a down firing sub (say, into an end table or something) and closed off the front entirely, and placed it nearly against a wall, would that dramatically affect the performance of the sub? (my guess is "no" provided that the other two remaining sides are raised up sufficiently to allow for the appropriate amount of air flow, but what do I know).
3. If another [multi] speaker were to be placed relatively close to one of the two remaining open air areas, would the sub's machinations affect the performance of the multi significantly or would their relative frequencies simply not overlap enough to affect each other.
Note: I'm assuming that the sub is MDF and, so is the majority of the multi.
Cheers,
Dave.
I am such a noob that I don't even know what I don't know so please forgive me these really stupid questions.
My current sub (ASW610XP) with it's 10", front firing, driver has a seizure on it's plinth every time it tries to convince me that there's a helicopter flying through my lounge (and all of that paper that I stack ontop of it falls off).
This is obviously because the driver is able to deliver enough kinetic energy to move the enclosure laterally (no carpet spikes being used to protect my damage deposit). So, to me, it makes sense that a down firing enclosure would reduce the lateral movement of the enclosure (provided that the enclosure was suitably heavy). But I suspect that the driver would still cause the enclosure vibrate, unless the enclosure is massively, massively, massively heavy.
I've seen other subs that had a plinth that was attached to the enclosure (and the driver fired down at the plinth); my guess is that this kind of setup would further reduce the vibration of the enclosure (but having never seen one up front, I really don't know)
So my questions:
1. Is there a way to make a zero vibration enclosure for a sub that I want to move prodigious amounts of air? I want to transmit absolutely no vibration at all from the driver to the enclosure.
2. LFE is radial; so if I built a down firing sub (say, into an end table or something) and closed off the front entirely, and placed it nearly against a wall, would that dramatically affect the performance of the sub? (my guess is "no" provided that the other two remaining sides are raised up sufficiently to allow for the appropriate amount of air flow, but what do I know).
3. If another [multi] speaker were to be placed relatively close to one of the two remaining open air areas, would the sub's machinations affect the performance of the multi significantly or would their relative frequencies simply not overlap enough to affect each other.
Note: I'm assuming that the sub is MDF and, so is the majority of the multi.
Cheers,
Dave.
@Cal, but then they'd have to be out of phase, otherwise the movement of the drivers would increase the amplitude of their vibrations.
So if I wire them out of phase, what is that going to do to my room acoustics? Isn't that going to create a bunch of dead zones throughout my space?
And if they were out of phase, what would I do with the enclosure? It strikes me as a bad thing if they were sharing the same air... unless, I guess, if the enclosure volume was suitably large.
So if I wire them out of phase, what is that going to do to my room acoustics? Isn't that going to create a bunch of dead zones throughout my space?
And if they were out of phase, what would I do with the enclosure? It strikes me as a bad thing if they were sharing the same air... unless, I guess, if the enclosure volume was suitably large.
Yes so they push out at the same time. If you wired them the opposite way you would not get much output at all.
Bipolar...
Yes, moving out of the box at the same moment in time, or Bipolar.
Albeit, imnipolar, because they are bass-freqs.
Later,
Wolf
Yes, moving out of the box at the same moment in time, or Bipolar.
Albeit, imnipolar, because they are bass-freqs.
Later,
Wolf
Put them on two sides of a ceramic or metal tube ( expensive ) turn one magnet system inside out and wire them in antiphase for distortion cancelation. A tube is the most stable form after a sphere.
Thanks for the responses so far everyone; they've been really informative.
So biploar arrangements are one way; are there other ways to accomplish this? I ask because I'm looking at making this system stealth (to appease the ruler of the house) so having one speaker on each side of the enclosure isn't going to work.... unless I can put that tube inside of another enclosure or something.
That's why I was asking about maybe firing the driver toward a plinth; I was hoping that the force of the air hitting the plinth would help to counteract the movement of the driver.
So biploar arrangements are one way; are there other ways to accomplish this? I ask because I'm looking at making this system stealth (to appease the ruler of the house) so having one speaker on each side of the enclosure isn't going to work.... unless I can put that tube inside of another enclosure or something.
That's why I was asking about maybe firing the driver toward a plinth; I was hoping that the force of the air hitting the plinth would help to counteract the movement of the driver.
The trick involves counterforce from the same moving masses being driven against one another with the same signal. The driver moving mass includes the air load. You need 2 same drivers firing away from each other. A tube is not necessary, a cubic enclosure is ok. However, if you have one built for a 10, you will probably need less than 2 8's to work well in the same volume.
In any case, anything you do with the air in front of the cone can't compensate for the rest of the moving mass, which is actually the larger and therefore more problematic part anyway.
In any case, anything you do with the air in front of the cone can't compensate for the rest of the moving mass, which is actually the larger and therefore more problematic part anyway.
You could always go out and buy another identical sub and bolt them together with some all thread, nuts and washers.
Another idea. Put the woofers into a concrete case into the wall and then put a slate plate in front of the woofer ca.2cm away from the cone so it is visually totally hidden.
Andrew,
I agree with most of what you say but I'm not sure about your last sentence. Although I must admit that I might be overcomplicating this and missing something.
When I look at the relative masses of the woofer's frame, magnet, cone and lining, I'm left to think that the majority of the mass is actually attached to the enclosure itself, while the cone + coil weigh only a few grams.
If I think about putting a driver in a heavy enclosure, at rest, in a weightless vaccuum and turn it on, the whole assembly will move back and forth by the same distance of the throw of the driver, divided by the mass ratio of the cone+coil vs enclosure+speaker frame. This would, obviously, cause the overall system to "vibrate".
But if I fill that vaccum with air and turn on my speaker, it's going to continue to build up speed until it hurts someone (assuming a closed or ported enclosure rather than an open one).
That leads me to think that the majority of the low frequency vibration is causes by the displacement of the air rather than the mass of the driver, which seems to contradict your last sentence.
I guess, if I take that thought further, by providing a wall (that's attached to the enclosure), I'm counteracting (well, redirecting actually) the force of the moving air which only leaves the mass of the driver+coil (more or less).
So now that I think on it, perhaps I could use my bottom plinth and just put another speaker in the enclosure sealed mid-way inside of it's own sub-enclosure (completely sealed). Perhaps that way it wouldn't need to 'taste air'.
Am I making any sense or am I just talking rubbish (and, transitively, over complicating things, as my wife says I tend to do)?
Cheers,
Dave.
I agree with most of what you say but I'm not sure about your last sentence. Although I must admit that I might be overcomplicating this and missing something.
When I look at the relative masses of the woofer's frame, magnet, cone and lining, I'm left to think that the majority of the mass is actually attached to the enclosure itself, while the cone + coil weigh only a few grams.
If I think about putting a driver in a heavy enclosure, at rest, in a weightless vaccuum and turn it on, the whole assembly will move back and forth by the same distance of the throw of the driver, divided by the mass ratio of the cone+coil vs enclosure+speaker frame. This would, obviously, cause the overall system to "vibrate".
But if I fill that vaccum with air and turn on my speaker, it's going to continue to build up speed until it hurts someone (assuming a closed or ported enclosure rather than an open one).
That leads me to think that the majority of the low frequency vibration is causes by the displacement of the air rather than the mass of the driver, which seems to contradict your last sentence.
I guess, if I take that thought further, by providing a wall (that's attached to the enclosure), I'm counteracting (well, redirecting actually) the force of the moving air which only leaves the mass of the driver+coil (more or less).
So now that I think on it, perhaps I could use my bottom plinth and just put another speaker in the enclosure sealed mid-way inside of it's own sub-enclosure (completely sealed). Perhaps that way it wouldn't need to 'taste air'.
Am I making any sense or am I just talking rubbish (and, transitively, over complicating things, as my wife says I tend to do)?
Cheers,
Dave.
Dave,
If you are considering a down-firing driver you have to be careful that the driver can be mounted this way. Deep bass = heavy cone = sag = ruined driver over time.
The second cone idea is called isobaric loading and is usually done with an active driver. The advantage of it is that you can reduce the overall size of the enclosure by 1/2. Again you have to be careful of any down-firing as mentioned above. Easier just to mount to drivers on opposite sides and find a way to reach the all important WAF.
If you are considering a down-firing driver you have to be careful that the driver can be mounted this way. Deep bass = heavy cone = sag = ruined driver over time.
The second cone idea is called isobaric loading and is usually done with an active driver. The advantage of it is that you can reduce the overall size of the enclosure by 1/2. Again you have to be careful of any down-firing as mentioned above. Easier just to mount to drivers on opposite sides and find a way to reach the all important WAF.
@Cal - awesome, never heard/thought of 'sag'. Great advice!
/me scribbles notes in his speaker design note book.
/me scribbles notes in his speaker design note book.
I wouldn't call it rubbish but I think you're trying to complicate the issue. If you don't believe me that the largest mass of concern is the cone assembly including coil, go ahead and build a box with a woofer suspended inside it and see if you can still make it vibrate like mad.
The problem no matter what is Cancellation only occurs if both cones are pitted against one another and doing the exact same job. Not only can you not put one driver in a different enclosure, for best performance you'll have to try getting both cones loaded equivalently, like not putting one up against the wall and the other firing toward the room.
Personally, if we're talking about the inexpensive cube sub I think we are, I'd buy two and bolt them together with about 5 or 6" between the drivers. You probably don't even need that much. Hopefully you're not trying to run a very high turnover point. A little flat black paint and you'd be done. One trip to home depot. No science at all.
The problem no matter what is Cancellation only occurs if both cones are pitted against one another and doing the exact same job. Not only can you not put one driver in a different enclosure, for best performance you'll have to try getting both cones loaded equivalently, like not putting one up against the wall and the other firing toward the room.
Personally, if we're talking about the inexpensive cube sub I think we are, I'd buy two and bolt them together with about 5 or 6" between the drivers. You probably don't even need that much. Hopefully you're not trying to run a very high turnover point. A little flat black paint and you'd be done. One trip to home depot. No science at all.
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