I ordered some ‘ stuff’ from my favorite place McMaster-Carr. For speaker bracing
something that will be completely reversible.
god that online store is like a toy store for adult men. Lol
love it.
stay tuned for my experiment. Should be fun and educational. Even if it doesn’t work.
something that will be completely reversible.
god that online store is like a toy store for adult men. Lol
love it.
stay tuned for my experiment. Should be fun and educational. Even if it doesn’t work.
Andy/All
"Stiffening the baffle around the drivers is a positive thing to do because it will reduce the amount of energy transferred from the vibrating driver into the cabinet to then be dissipated via damping or radiated away as sound. However, running a rod from the middle of the baffle to the middle of the rear panel will likely make things worse. This is because it will introduce a new mode with substantial mass where the baffle moves in and out, the rod moves in and out and the rear panel moves in and out all in phase with each other.
I'm not sure I understand your reasoning for this. Am I correct in that the panel vibrations are caused by differential pressure waves within the cabinet as the driver cone moves in and out? If so, would it (on a reflex cabinet for example) be a sequence where:
Driver moves out from rest causing a partial vacuum within the cab, front panel moves inward, all other panels move inward as they are acted upon by atmospheric pressure. Air moves into the cab via the open port, equalising pressure, panels move back to starting/neutral position. When speaker cone moves backward, the reverse happens. A bit like blowing up or sucking air from an inflated balloon.
Would you agree or disagree with that?
"Stiffening the baffle around the drivers is a positive thing to do because it will reduce the amount of energy transferred from the vibrating driver into the cabinet to then be dissipated via damping or radiated away as sound. However, running a rod from the middle of the baffle to the middle of the rear panel will likely make things worse. This is because it will introduce a new mode with substantial mass where the baffle moves in and out, the rod moves in and out and the rear panel moves in and out all in phase with each other.
I'm not sure I understand your reasoning for this. Am I correct in that the panel vibrations are caused by differential pressure waves within the cabinet as the driver cone moves in and out? If so, would it (on a reflex cabinet for example) be a sequence where:
Driver moves out from rest causing a partial vacuum within the cab, front panel moves inward, all other panels move inward as they are acted upon by atmospheric pressure. Air moves into the cab via the open port, equalising pressure, panels move back to starting/neutral position. When speaker cone moves backward, the reverse happens. A bit like blowing up or sucking air from an inflated balloon.
Would you agree or disagree with that?
i plan on putting some bracing in the form of rods across the side panels.
does that sound good?
In my case, with a sealed air-supension design, your comment doesn't apply.
The bracing actually keeps the cabinet having any from any buckling or vibrations.
I would suspect that a ported cabinet would act in a similar manner.
This mode will not be coupled through the air inside the cabinet, according to the panels being tied together. When the baffle is moved by a reaction to the cone's mass/acceleration, it will be halved by sharing with the back. Furthermore it is a dipole mode from an external direct radiation point of view.
This is a great article on cabinet bracing
enjoy
https://www.audioholics.com/loudspe...abinet-bracing/finite-element-analysis-part-i
enjoy
https://www.audioholics.com/loudspe...abinet-bracing/finite-element-analysis-part-i
Wise old tech
"In my case, with a sealed air-supension design, your comment doesn't apply."
Why? What then makes the cabinet panels vibrate if it is not internal/external air pressure waves?
Whilst I can see that the mass of the cone reversing direction could cause vibrations on the front baffle how would they cause sizable vibrations on the sides or back?
"In my case, with a sealed air-supension design, your comment doesn't apply."
Why? What then makes the cabinet panels vibrate if it is not internal/external air pressure waves?
Whilst I can see that the mass of the cone reversing direction could cause vibrations on the front baffle how would they cause sizable vibrations on the sides or back?
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No. Forcing from the air pressure inside the cabinet is negligible compared to the forcing from the vibrating drivers except at the lowest frequencies. Since the lowest frequencies are well below the resonant frequencies and deep into the stiffness controlled region it becomes a non-issue with respect to radiated sound. An engineer will generally only consider the forcing from the drivers and the response from the lowest handful of resonances because these are what can become loud enough to be perceived.
Andy.
"Forcing from the air pressure inside the cabinet is negligible".
All I am doing is asking questions. It's easy for a person to categorically maintain a certain view but in this case, I cannot agree, the forces from driver reversal are in line to the sides, not perpendicular, in this direction the sides are immensely strong, even if unbraced because they in effect act as braces to the outer edges of the back and front. The only perpendicular forces as I see it are pressure waves. I'm happy to be proven wrong. As an example try to bend a bar on edge (taking care) compared to on it's face. Regarding frequency perception as one goes up the frequency range does not air and cabinet material dampening and amplitude of movement lower sound output from these vibrations?
"Forcing from the air pressure inside the cabinet is negligible".
All I am doing is asking questions. It's easy for a person to categorically maintain a certain view but in this case, I cannot agree, the forces from driver reversal are in line to the sides, not perpendicular, in this direction the sides are immensely strong, even if unbraced because they in effect act as braces to the outer edges of the back and front. The only perpendicular forces as I see it are pressure waves. I'm happy to be proven wrong. As an example try to bend a bar on edge (taking care) compared to on it's face. Regarding frequency perception as one goes up the frequency range does not air and cabinet material dampening and amplitude of movement lower sound output from these vibrations?
It is a common thing to do which might be OK but this would likely depend on the details of the forcing. It will introduce unwanted low frequency modes (and is best avoided for that reason) but, unlike the modes involving front-to-back rods which will definitely be driven, if the speaker is symmetric then that would suggest they may not be. The reason for suggests is that the speaker may have pairs of modes involving the driver rocking on the baffle so without details one cannot be adamant. For example, large dome midranges constructed like tweeters became effectively extinct many years ago due to practical problems with rocking modes despite the forcing appearing symmetric.
A resonance involves both mass and stiffness. The centre of a panel is low stiffness (compared poking the middle of the panel with the outside where it is better supported) and connecting two will indeed double this weak stiffness. But it is the mass that is causing the bigger problem since instead of light bending panel we now also have to move the mass of a heavy rod at the centre of the panel. This creates a new driven low frequency mode that is fairly likely to be the noisiest in the cabinet.
Of course one can avoid much of this by triangulating and connecting the centre of the baffle with several rods to the corners of the back panel or, more commonly, by using a panel (usually with holes) rather than a rod to distribute the connection rather than concentrating it in the centre of the baffle. Supporting/stiffening the baffle is almost always going to be beneficial so long as it is done competently. Supporting the side walls on the other hand generally does little to reduce the sound radiated from the cabinet.
It is likely to be more misleading than useful because it doesn't consider a cabinet with drivers. A box with holes and heavy drivers attached to the baffle introduces modes that are not directly related to the bending of individual panels. These modes tend to be lower in frequency and more problematic. This white paper shows what useful cabinet analysis tends to look like.
Andy as I see it, that is true if the vibrations are not caused by pressure waves. It would tend to be dependant on cone mass, does this play out in real life? Tap a tuning fork, listen to the sound, now lightly stuff the gap with anything, the sound though increasing in frequency reduces in volume.
So, in summation to all that I have said/asked, I think tie rods anywhere on the cabinet (first where deflections are greatest) would act to substantially reduce cabinet resonance, they stop the panels moving outward or inward. They would have to be a tight fit and well fixed to stop panel movement in either direction (tension and compression). These, to me at least reduce the amplitude of the movement by the greatest amount and hence panel sound output. Obviously the panel still would vibrate/flex but the closer the ties the stiffer the panel and the smaller the amplitude hence sound output. This latter condition is enacted by cross panels with holes that act as multiple ties and also reduce vibrations due to panel size reduction and dampening of the panel material itself. I don't think anybody is saying that the vibrational sound is completely removed just that it is changed/reduced to a point of being non important.
Later I will post a couple of pictures showing a crude example that I tried a couple of years ago.
Just my 2d's worth.
PS, I've just seen your post, the white paper looks great, I'll have a study. Thanks
So, in summation to all that I have said/asked, I think tie rods anywhere on the cabinet (first where deflections are greatest) would act to substantially reduce cabinet resonance, they stop the panels moving outward or inward. They would have to be a tight fit and well fixed to stop panel movement in either direction (tension and compression). These, to me at least reduce the amplitude of the movement by the greatest amount and hence panel sound output. Obviously the panel still would vibrate/flex but the closer the ties the stiffer the panel and the smaller the amplitude hence sound output. This latter condition is enacted by cross panels with holes that act as multiple ties and also reduce vibrations due to panel size reduction and dampening of the panel material itself. I don't think anybody is saying that the vibrational sound is completely removed just that it is changed/reduced to a point of being non important.
Later I will post a couple of pictures showing a crude example that I tried a couple of years ago.
Just my 2d's worth.
PS, I've just seen your post, the white paper looks great, I'll have a study. Thanks
Without the brace there won't be a low frequency mode where the centres of the two panels move together with the rest of the speaker remaining close to motionless. For the new mode the shape of the front and back panel will likely tend towards a locally deformed one with the brace punching through the panel rather than the smooth one of a single panel.