we will know soon enough.
i made the order. And will carry out the experiment.
stay tuned
Yes and it will have a low resonant frequency because it is placing a heavy mass at the centre of a panel. If it is not driven then it won't radiate sound but it will still exist and may cause problems in the future if there are modifications. I would view it as something to be avoided unless forced by circumstances.
Steelrods for damping resonances Work well in my experience. I use thick rubber on each side of the rod ie between cabinet and rod (Rubber is the stuff you can get to dampen vibrations from dry tumbler).
Rule of thump is to place them non symmetric in the cabinet.
As other pointed out. More damping in the cabinet may shift the resonances from around 600 hz to 1500-2000 hz. I rather have them at 600.
Rule of thump is to place them non symmetric in the cabinet.
As other pointed out. More damping in the cabinet may shift the resonances from around 600 hz to 1500-2000 hz. I rather have them at 600.
It will be aluminum. Not steel.
sorry. Being exact
they will be mounted on the bitumen of the cab walls
sorry. Being exact
they will be mounted on the bitumen of the cab walls
You can make a subjective test listening with you ear close/at the cabinet, then at the same time tap the cabinet. As is now I expect more of a hollow sound.
if you mount to many rods I expect a bell like ringing.
of course there is more to it, you should also be able to actually hear music/some sound, listening with you ear right at the cabinet.
if you mount to many rods I expect a bell like ringing.
of course there is more to it, you should also be able to actually hear music/some sound, listening with you ear right at the cabinet.
I'm a little unclear of the logic around whether it does or doesn't exist. However..
What do you think about tying them together in the middle like a cross?
i did think about that of course.
but with all I read it seemed that it was better to brace just across the width
Read Geddes on bracing and examine the KEF LS50 white paper. Both sources explore bracing with built-in damping.
Btw you should brace the baffle.
Btw you should brace the baffle.
That is a bit better but only a bit because the cross rods are tied at their least stiff position in the centre. If you wish to use rods to stiffen effectively then you need to triangulate. This can get messy particularly when the magnets are in the way forcing the use of smaller more complicated triangulation. Panels with holes is likely to be the most straightforward route to effective stiffening but that is unlikely to be easy to do given the way the OP wishes to tackle things. Plus, of course, the OP's bodges aren't going to do anything worthwhile but that is for him to have fun discovering rather than listening to anonymous know-it-alls on the interweb like me.
In my RCA console restoration and modifications, I didn't want the thin side walls vibrating, because it made the bass obviously "boomy", adding a certain flavor to what the woofers sent out to my ears.
The 1/4 inch plywood with veneer when tapped, made a sound like a drum.
I didn't want the cabinet to make any contributions to the resulting tone quality that the speakers emitted.
Installing 3/4 inch pine glued on the insides, along with internal panels used for separation and component mounting, gave the whole cabinet a rock-solid, non-vibrating and non-boomy nature, which is what I wanted.
Now, tapping on the sides, it makes a "click" type of noise, well above the bassy-thump of before.
Even the front speaker baffle, now reinforced with 3/4 inch pine, is more or less "soundproof", being coupled to the inner panels.
The original style 12 inch woofers here were later replaced with a pair of high-compliance versions with massive ceramic magnets - the rear panels (not shown here) also have a slot for tuning, and the resulting effect is very very pleasing with all types of music - tight bass, deep, non-fatiguing. - Certainly not boomy.
Additionally, any "one note" bass at the resonance frequency of the woofers is thwarted by the non-identical sizing of each chamber.
The 1/4 inch plywood with veneer when tapped, made a sound like a drum.
I didn't want the cabinet to make any contributions to the resulting tone quality that the speakers emitted.
Installing 3/4 inch pine glued on the insides, along with internal panels used for separation and component mounting, gave the whole cabinet a rock-solid, non-vibrating and non-boomy nature, which is what I wanted.
Now, tapping on the sides, it makes a "click" type of noise, well above the bassy-thump of before.
Even the front speaker baffle, now reinforced with 3/4 inch pine, is more or less "soundproof", being coupled to the inner panels.
The original style 12 inch woofers here were later replaced with a pair of high-compliance versions with massive ceramic magnets - the rear panels (not shown here) also have a slot for tuning, and the resulting effect is very very pleasing with all types of music - tight bass, deep, non-fatiguing. - Certainly not boomy.
Additionally, any "one note" bass at the resonance frequency of the woofers is thwarted by the non-identical sizing of each chamber.
The energy that excites potential resonances mostly comes from the reactive force to the drivers cone movement.
This is easy to show: First, half the energy from the air mass moved goes out into the room, but all of the reactive energy gets directly injected into the box, and, with damping in the bo, the highest frequencies from the energy of the moving air will be removed, and should not be an issue at all. In a box with a hole in it, even more of that air mass energy is sent out into the room and is not available for exciting box resonances.
Andy’s suggestion that adding a brace from the baffle to the back could cause the speaker to literally do a bendy dance, makes little sense to me. We are making the box more like an i_bem than a plane panel. Rarely will this be less structurally solid.
As Allen suggested tieng the baffle to the back distributes the energy being injected into the baffle between the baffle & the back. So less energy on either panel to cause that potential resonance to get excited.
The goal of adding bracing is to push potential resonances up high enuff that they will not be excited. If they are not excited (by the music) it is s if they do not exist.
Why up? Because there will be less energy at high frequencies to excite the box, and as the frequency goes up the box material (and to a small extent the damping) will more effectively provide damping at those frequencies. If one can make the potential box resonance a high Q one, then it is even less likely to get excited as one will not get the steady input at a particular frequency to set the resonance going.
You will never get rid of potential resonances, you can only put them where they won’t get excited.
The OP is doing a band-aid bracing after the fact, it will not be as effective as more significant bracing, but it will push resonances up.There is a small chance of getting it just so that it does something bad, but that changes when you decide it needs another brace.
dave
This is easy to show: First, half the energy from the air mass moved goes out into the room, but all of the reactive energy gets directly injected into the box, and, with damping in the bo, the highest frequencies from the energy of the moving air will be removed, and should not be an issue at all. In a box with a hole in it, even more of that air mass energy is sent out into the room and is not available for exciting box resonances.
Andy’s suggestion that adding a brace from the baffle to the back could cause the speaker to literally do a bendy dance, makes little sense to me. We are making the box more like an i_bem than a plane panel. Rarely will this be less structurally solid.
As Allen suggested tieng the baffle to the back distributes the energy being injected into the baffle between the baffle & the back. So less energy on either panel to cause that potential resonance to get excited.
The goal of adding bracing is to push potential resonances up high enuff that they will not be excited. If they are not excited (by the music) it is s if they do not exist.
Why up? Because there will be less energy at high frequencies to excite the box, and as the frequency goes up the box material (and to a small extent the damping) will more effectively provide damping at those frequencies. If one can make the potential box resonance a high Q one, then it is even less likely to get excited as one will not get the steady input at a particular frequency to set the resonance going.
You will never get rid of potential resonances, you can only put them where they won’t get excited.
The OP is doing a band-aid bracing after the fact, it will not be as effective as more significant bracing, but it will push resonances up.There is a small chance of getting it just so that it does something bad, but that changes when you decide it needs another brace.
dave
Interesting, I found the opposite to be indicated. This was after isolating the driver from the cabinet via an elastomer sheet, such that it was clearly "sprung" from the enclosure mass. The rear radiation of the driver still put a lot of SPL into the inside of the cabinet. You could hear it coming through the cabinet walls. This was a cheap, commercial (KEF) 5/8" MDF box constructed of the six panels simply glued together at the edges.
Because a driver has mass, there will be some frequency eventually where the force reactions get clamped. The SPL coming off the back of the speaker doesnt diminish like that until crossover - which might be a couple kHz - and the cabinet has to contain it. How well it does that job depends entirely on material and structure.
I used the worst case possible construction in my experiment, because they're so common and expendible (I was going to throw them out anyway). There's too many speakers built like that in this world (to where I'd expect that flabby-cabby sound is what most people know) and not enough built the way dave builds them.
They used to sell this stuff you could paint the inside of your cabs with, I think it was called black hole - a quick Google search doesnt find it. Only paint for the outside of a speaker. I think the idea was to reduce panel vibration through mechanical absorbtion into the applied "paint" layer. Perhaps it was just all marketing foo - "Black Hole"; yeah, right I get it - the sound just disappears into the black hole...
If it actually worked, well too bad they're apparently out of business. I dont know what paintable material would substitute. Except to cut sheets of "sorbothane", rubber foam, solid rubber sheet - and glue it firmly across the 5 non-baffle inside surfaces. Which will change the cabinet internal volume, unfortunately.
Take an L or angle shaped piece of fiberglass (used in electrical fabrication) or aluminum, and screw it every few inches to the panel.
Even a rectangular aluminum extrusion should work, if there is room.
Should stiffen it up, and is reversible.
Even a rectangular aluminum extrusion should work, if there is room.
Should stiffen it up, and is reversible.
It has been suggested that the pressure component inside the enclosure is so low as to be almost insignificant compared with driver reaction forces. What many folks are missing is that, whilst this is probably the case, it must be remembered that very little energy is required to excite a resonant system at its fundamental frequency - think of low driver excursion at resonance in a ported enclosure, a pendulum clock, or a child on a swing.
Fundamentally, subs require high stiffness, midrange requires high damping.
Fundamentally, subs require high stiffness, midrange requires high damping.