Should the back of the bass driver(s) rest firmly on the internal bracing of the cabinet?
Are there any pros and cons of that in general and in my case?
In may case (slim 3-way) there are two stiff 5.5in high-excursion drives, on the same baffle (not opposing push-push). I have the option of placing some of the internal bracing on the back of the bass drivers. The drivers are 4kg each. The front baffle is 31mm, side walls 21mm, back wall 31mm. Heavy cabinet.
And what about the midrange?
Are there any pros and cons of that in general and in my case?
In may case (slim 3-way) there are two stiff 5.5in high-excursion drives, on the same baffle (not opposing push-push). I have the option of placing some of the internal bracing on the back of the bass drivers. The drivers are 4kg each. The front baffle is 31mm, side walls 21mm, back wall 31mm. Heavy cabinet.
And what about the midrange?
Last edited:
The primary use of internal cabinet bracing is to stiffen panels, reducing their vibrations which may "color" the sound when in or out of phase with driver output.
A driver resting firmly on internal bracing would tend to transmit it's mechanical motion to the exterior panels, generally not a desirable outcome.
It is more likely for slim cabinets to be tipped over, one positive aspect might be reducing the chance of a driver's frame or magnet structure breaking on a hard drop.
A driver resting firmly on internal bracing would tend to transmit it's mechanical motion to the exterior panels, generally not a desirable outcome.
It is more likely for slim cabinets to be tipped over, one positive aspect might be reducing the chance of a driver's frame or magnet structure breaking on a hard drop.
As a launching pad, the woofer motor (eg magnet) should connect with the centre of mass of the cabinet. In that respect you should ensure the cabinet is brought together at that brace as though it were an Earth (ground) point.
On the other hand, should doesn't always mean must. An awareness of things that would be audible problems is what tends to drive cabinet construction. Sound is transmitted through mechanical contact, so research soft mounting methods and ways to damp panels.
On the other hand, should doesn't always mean must. An awareness of things that would be audible problems is what tends to drive cabinet construction. Sound is transmitted through mechanical contact, so research soft mounting methods and ways to damp panels.
I am a firm believer in bracing to the enclosure.
Shares the reactive force of the basket with the back (and top & bottom) instead of the baffle dealing with it all. Makes the driver a part of an i-beam structure instead of sitting in the “middle” of a “floppy" baffle. The reactive force force now loads directly into more material, reducing the likelihood of exciting potential box resonances. A side benefit is often increased DDR — especially in wide range drivers.
Tricky to get right.
dave
Shares the reactive force of the basket with the back (and top & bottom) instead of the baffle dealing with it all. Makes the driver a part of an i-beam structure instead of sitting in the “middle” of a “floppy" baffle. The reactive force force now loads directly into more material, reducing the likelihood of exciting potential box resonances. A side benefit is often increased DDR — especially in wide range drivers.
Tricky to get right.
dave
That statement in general isn’t true. Mechanical motion/forces of the driver must end up somewhere and the baffle is more not than often the best place for that…
So, looks like, in general, the driver needs to be fixed onto a structure (a given) and the heavier that structure the better - how heavy and damped is that structure is the primary consideration (assuming the connection is made well). The heavier the better and the better damped the better.
Then, the secondary consideration is how exactly that 'resting' is achieved - via the baffle, via the back of the driver or a combination of both (again, assuming the connection is made well).
This means that in my case:
The mid driver will only rest on the front baffle - as it is heavy enough and damped enough.
The two bass drivers would benefit from being connected to both the baffle and the cabinet. As the cabinet is relatively heavy compared to the driver (and the baffle not enough) and that connection is not far from the cabinet center of mass. The connection to bracing needs to be structurally strong to realise the benefit while also minimise transmission of vibration.
Action: install strong bracing behind the two bass drivers so the driver rests firmly on the bracing. (the bracing there is already planned anyway). Maybe add damping material between driver and brace or between brace and cabinet walls.
Then, the secondary consideration is how exactly that 'resting' is achieved - via the baffle, via the back of the driver or a combination of both (again, assuming the connection is made well).
This means that in my case:
The mid driver will only rest on the front baffle - as it is heavy enough and damped enough.
The two bass drivers would benefit from being connected to both the baffle and the cabinet. As the cabinet is relatively heavy compared to the driver (and the baffle not enough) and that connection is not far from the cabinet center of mass. The connection to bracing needs to be structurally strong to realise the benefit while also minimise transmission of vibration.
Action: install strong bracing behind the two bass drivers so the driver rests firmly on the bracing. (the bracing there is already planned anyway). Maybe add damping material between driver and brace or between brace and cabinet walls.
Not necessarily the bass speakers and often the mid speakers. You first would have to acquire info on the resonant behavior of the panels of your enclosure. Those resonances often appear in midrange frequencies, from 150Hz to -take or leave- 1kHz. Then you’d decide on decoupling bass or mid drivers, of course in relation to the crossover frequencies.
You could go half way, and wedge a bit of foam in-between, to act like a damper - even experiment with two wooden wedges for a more solid structure.
My LF chamber will work in the 30-300Hz range.
The mid/HF chamber will work in the 300-3k-20k range.
The mid/HF chamber will work in the 300-3k-20k range.
Radiant Acoustics uses a porous material to rest the magnet against the bracing in their Clarity speakers.
Something like Sorbotane. If this is worth the effort? I don't know.
Something like Sorbotane. If this is worth the effort? I don't know.
Yes, it is. A type of viscoelastic junction between basket/magnet and brace would help reducing vibration transmission.
But you want to maximize the energy transfer beween driver and the rest of the box to minimize the amount of energy fed into the baffle. A “damper" would be counter-productive.
dave
dave
Decoupling the driver from the baffle is the idea. Using some closed-cell foam with a bit of plastic behavior as gasket and the right elastic-plastic washers under the screw or bolt heads should do the trick. I still envy how KEF constructed the mid-high assembly of the RR104.2 though… elegant and effective.
Couldn’t resist that 😊
Couldn’t resist that 😊
If you are of the opinion that transmission of the driver's mechanical vibrations to multiple cabinet walls is a benefit, yes.
If you are of the opinion that decoupling the driver's vibrations is a benefit, then don't connect them, or add damping material between the braces.
Either way, it won't make a difference considering your front baffle is 31mm, side walls 21mm, back wall 31mm and the walls are braced.
When they went from R300 to R3, the uni-q was someone stuck to bracing behind it.
My tannoy 6s (the 6 sides boxes) used blue-tac (poster tac)
KEF has a habit of bracing drivers from at least the eighties on. You can see the braced and damped (the red stuff) magnet in the LS50 and the rather lightweight baffle. It actually is quite basic engineering. Very effective though. I think every other serious manufacturer has at least experimented with such approaches. Getting it right in a production chain is another challenge...
Source is -of course- the white paper.
Source is -of course- the white paper.
Maybe it's crazy, but based on the question voiced in this thread, I would screw a metal pin between the speaker and the nearest spacer.
I can't see the back of the Dayton Audio Epique, maybe the middle hole is for cooling, and the purpose of the other three is unclear. It depends on how the pin can work - to stretch or compress the speaker housing.
In any case, it will be beneficial, but not cardinally. Perhaps it will not even be noticeable by ear, but it will add strength.
IMHO
I can't see the back of the Dayton Audio Epique, maybe the middle hole is for cooling, and the purpose of the other three is unclear. It depends on how the pin can work - to stretch or compress the speaker housing.
In any case, it will be beneficial, but not cardinally. Perhaps it will not even be noticeable by ear, but it will add strength.
IMHO
Bracing is beneficial and for the DIYer is a pain to achieve without precision machine cuts!
I am documenting my solution on my hobby Website. All are welcome to use my method, without guarantee, for non professional use [ https://www.terrysweb.link/audio/loudspeaker]. My demo has twin drivers but can be adapted for a single driver.
It takes the energy from the transducer's rear and returns it to the baffle - like NFB.
It also has scientific roots in Single Degree of Freedom....