Fair enough... must have mixed up a couple of posts. (or it is what I figured I would want to do
)
I guess I remembered a post similar to this one:
Which doesn't mean he applies it to his own cross braces. My bad...
Which doesn't mean he applies it to his own cross braces. My bad...
Aha, maybe you were right after all. Some newer links..
On damping the cross brace
On tying the front and rear panels together
On choosing a cabinet ground point
On tying the magnet to the cabinet
On damping the cross brace
On tying the front and rear panels together
On choosing a cabinet ground point
On tying the magnet to the cabinet
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Yes, that first link is the one that I recalled reading.
(glad to see my memory didn't fail on me, I read it at that time)
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Old thread but some serious builders in this one so i'll ask if anyone ever tried this technique described in this patent? US5639996A - Asymmetrically resonance tuned speaker-box
- Google Patents
I've just read from some thesis (or some thread, read many hours and forgot where was it) about cabinet resonances and the measurements basically said that bracing don't kill cabinet resonance but merely pushes it up in frequency. Dampening the resonances would be better.
In the enclosure described in the patent resonances are spread out by having different mass and varying thickness per panel to get them resonate in different frequencies. Also, there is a note that without bracing the resonant energy in the enclosure walls is dampened faster. Any thoughts?
I gotta try this, if no one says it doesn't work
- Google Patents
I've just read from some thesis (or some thread, read many hours and forgot where was it
) about cabinet resonances and the measurements basically said that bracing don't kill cabinet resonance but merely pushes it up in frequency. Dampening the resonances would be better. In the enclosure described in the patent resonances are spread out by having different mass and varying thickness per panel to get them resonate in different frequencies. Also, there is a note that without bracing the resonant energy in the enclosure walls is dampened faster. Any thoughts?
I gotta try this, if no one says it doesn't work
Old thread but some serious builders in this one so i'll ask if anyone ever tried this technique described in this patent? US5639996A - Asymmetrically resonance tuned speaker-box
- Google Patents
I've just read from some thesis (or some thread, read many hours and forgot where was it
In the enclosure described in the patent resonances are spread out by having different mass and varying thickness per panel to get them resonate in different frequencies. Also, there is a note that without bracing the resonant energy in the enclosure walls is dampened faster. Any thoughts?
I gotta try this, if no one says it doesn't work
I haven't read the earlier posts in the thread and only glanced at the patent but a few points...
The lowest frequency modes in a typical cabinet involve all the panels moving together in a "whole body" motion. The resonances involving panels vibrating like panels are at higher frequencies and generally radiate less sound.
Symmetry is often good not bad when it comes to modes because it can lead to the sound radiated by some modes cancelling when a pair of panels move the same amount in opposite directions.
If you have resonances within the passband of the relevant driver/s then a quiet cabinet will need to include extra damping significantly beyond what would be provided by wood. Doing this effectively usually involves finding out which are the troublesome modes and making modifications to target damping at them or eliminate/modify them with structural bracing.
Stiffness of the front baffle is always beneficial because it reduces the work put into cabinet by the vibrating drivers. Stiffness of the other panels is less important unless the objective is to raise the frequency of the lowest resonances above the passband of the drivers (e.g. subwoofer and possibly woofer cabinets).
Mass is rarely useful for doing something constructive with cabinet vibration unless taken to extremes.
Michael Green was of the opinion that it was better to have one large resonance and damp it as best you can than to have a train of smaller resonances.
He used the example of old European concert halls.
Makes sense to me. Coloration is a fact of life. i would worry the mega mini resonances idea would sound like mud - just as when too many colors are added together.
He used the example of old European concert halls.
Makes sense to me. Coloration is a fact of life. i would worry the mega mini resonances idea would sound like mud - just as when too many colors are added together.
Since all solid bodies have an infinite number of resonances I think one safely say...
If competent attention is paid to the construction of a speaker cabinet then it's sound radiation can be made low enough to be inaudible in the presence of the sound radiated by the drivers. Sound radiation from the cabinet may be a fact of life but audible sound radiation from the cabinet need not be.
A panel is going to have the potential to ring no matter what you do. I have been taking measures to spread resonances and push them up high enuff, and with high enuff Q that they are extremely unlikely to ever get excited. This has worked extremely well.
If you are doing a multiway, it is certainly an attainable goal (for a woofer in a 3-way anyway) to pus resonances beyond the drivers bandwidth so no energy available at all for exciting box resonances.
The problem i have with trying to damp panel resonances is that the extra weight with no added stiffness both lowers the potential resonant frequencies, and broadens its Q so that it will accept more energy that might excite those resonances. Counterproductive to my mind.
dave
If you are doing a multiway, it is certainly an attainable goal (for a woofer in a 3-way anyway) to pus resonances beyond the drivers bandwidth so no energy available at all for exciting box resonances.
The problem i have with trying to damp panel resonances is that the extra weight with no added stiffness both lowers the potential resonant frequencies, and broadens its Q so that it will accept more energy that might excite those resonances. Counterproductive to my mind.
dave
The goal is to raise or lower the cab, etc., resonance above/below its pass-band, so for lower frequencies it's more efficient to brace, raising the resonance above the pass-band, then damping, which requires a lot less since sound power falls at 1/f.
If you try to push it below the pass-band you typically wind up with mutiple layers of different materials, constrained layer, stone, concrete, etc., construction, which will be both massive and stiff enough to need no damping if designed with no major reflections [eigenmodes].
Beginning around 300 Hz, mass loading becomes viable as witnessed by pioneers building with tar damped tin and later, cast aluminum, fiberglass, etc..
GM
If you try to push it below the pass-band you typically wind up with mutiple layers of different materials, constrained layer, stone, concrete, etc., construction, which will be both massive and stiff enough to need no damping if designed with no major reflections [eigenmodes].
Beginning around 300 Hz, mass loading becomes viable as witnessed by pioneers building with tar damped tin and later, cast aluminum, fiberglass, etc..
GM
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