Hello!
I am building the SBA 941's from Troels Gravesen and I have a few questions regarding the cabinet construction which there seems to be very little guidance available.
I will be using a CNC machine at my local makerspace for the MDF cutouts and I have therefore made the entire cabinet in Fusion 360. I believe Troels mentioned somewhere that the cabinet construction could be improved. Therefore I have taken inspiration from here and have added another panel inside the cabinet to make the back panel removable for any future adjustments that may need to be made. The panels inside the cabinets also have 5mm deep tracks for extra rigidity and to make the gluing process easier.
The middle panel however seems to have some weaknesses and I suspect that the schematics call for the removal of too much wood which may weaken the internal structure, see the photo provided with the black arrows on the right side:
Should I make the 130 mm diameter holes smaller, and if so do you have any tips on which size would be optimal - perhaps 105-115mm? The current holes seem to be to close together and the wood in between them gets very thin which I presume may be a bad thing
My other question is that I'm not sure how the front panels should be attached to the rest of the cabinet? Preferably I would like some form of mechanical solution alongside the glue that is to be put in place.
I have added a few other images of the cabinet construction in Fusion 360, hopefully this will give you a better understanding of the cabinet structure - the only part missing is the horizontal piece linking the back panel to the middle panel which I have not added yet. I am open to any changes and improvements that can be made in order to reduce cabinet resonance. I already have quite good cabinet dampening which I hear might be as important as a good cabinet structure, however it would also be nice to have a solid cabinet.
I appreciate any help that you are willing to give, this is my first ever speaker build so I duly apologize if I have made any severe mistakes - I would appreciate if they could be pointed out if so. Thank you in advance and have a nice day!
Link to the official website here: http://www.troelsgravesen.dk/SBA-941.htm
I am building the SBA 941's from Troels Gravesen and I have a few questions regarding the cabinet construction which there seems to be very little guidance available.
I will be using a CNC machine at my local makerspace for the MDF cutouts and I have therefore made the entire cabinet in Fusion 360. I believe Troels mentioned somewhere that the cabinet construction could be improved. Therefore I have taken inspiration from here and have added another panel inside the cabinet to make the back panel removable for any future adjustments that may need to be made. The panels inside the cabinets also have 5mm deep tracks for extra rigidity and to make the gluing process easier.
The middle panel however seems to have some weaknesses and I suspect that the schematics call for the removal of too much wood which may weaken the internal structure, see the photo provided with the black arrows on the right side:
Should I make the 130 mm diameter holes smaller, and if so do you have any tips on which size would be optimal - perhaps 105-115mm? The current holes seem to be to close together and the wood in between them gets very thin which I presume may be a bad thing
My other question is that I'm not sure how the front panels should be attached to the rest of the cabinet? Preferably I would like some form of mechanical solution alongside the glue that is to be put in place.
I have added a few other images of the cabinet construction in Fusion 360, hopefully this will give you a better understanding of the cabinet structure - the only part missing is the horizontal piece linking the back panel to the middle panel which I have not added yet. I am open to any changes and improvements that can be made in order to reduce cabinet resonance. I already have quite good cabinet dampening which I hear might be as important as a good cabinet structure, however it would also be nice to have a solid cabinet.
I appreciate any help that you are willing to give, this is my first ever speaker build so I duly apologize if I have made any severe mistakes - I would appreciate if they could be pointed out if so. Thank you in advance and have a nice day!
Link to the official website here: http://www.troelsgravesen.dk/SBA-941.htm
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I guess the cutouts are made round to be easy to produce with a hand router and trammel attachment.
Using CNC means you are not restricted to round holes.
You could add material only where you think it is too thin.
Using CNC means you are not restricted to round holes.
You could add material only where you think it is too thin.
Circles are the strongest shape, as there is nothing straight to resonate. Any deflection of an arc is heavily resisted. That mostly matters with longer spans tho.
And circles are super easy to cut with a router and jig.
If you use CNC, you can cut any shape you want. Try to maintain arcs over straight cuts where you can tho for extra reinforcement.
And circles are super easy to cut with a router and jig.
If you use CNC, you can cut any shape you want. Try to maintain arcs over straight cuts where you can tho for extra reinforcement.
Use quaity plyuwood instead of MDF for starters.
I would agree there is insufficient solid between the bbrace holes. I would alsoadd a holey-brace that touches the bass driver magnet and braces it against more of the box\. particularily. the back.
Midrange sub-enclosure could be made much less rectangular.
dave
Interesting !
An easy and soundwise good solution about the cabinet is to glue 3mm bitumen plates on each opposite wall inside the speaker ( the other opposite walls untreated ) .
This way, the cabinet walls will have different resonanse frequencies because of different weight, and this will avoid any tunefork effect , noticable on records with piano music ( left hand register will sound much clearer ). This trick has , in my opinion, much more audible consequenses than trying to stiffen up the cabinet , or making it heavier by gluing bitumen everywhere. You should avoid symmetry when fighting resonanses.
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