I was planning to apply the woofer box bracing like this. Outer dimensions of the box are: width x depth x height = 52cm x 28cm x 46cm
Box to be built using 18mm birch ply with 2x18mm thickness for front baffle
Please do let me know your suggestions..
Full box
Box to be built using 18mm birch ply with 2x18mm thickness for front baffle
Please do let me know your suggestions..
Full box
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Nice looking enclosure design.
It appears to me that the bracing has a shallow profile. It looks like in the center of the rear panel, the bracing is perhaps 18mm x 18mm in cross section. This is so shallow that it will not offer much stiffness.
I understand that with a cabinet depth of 28 cm, the woofer magnet is probably very near the rear wall, so it may not be possible to increase the bracing.
See if something like this would work. Make the bracing in the corners fully triangular.... check to see if it will clear the woofer magnet.
Thanks a lot @hifijim 🙂
I significantly thickened the triangular sections but due to driver size, I am not able to make full triangular sections as you showed.
The Faital pro 15PR400 can be easily accommodated but the NERO SW800, due to its large ferrite magnet is making things difficult..
The bracing near the middle section is 20mm x 18mm (I can increase that 20mm a tiny bit more if that helps things).
Updated bracing scheme
The cabinet volume with all the bracing is about 44L now. (Driver eats 6L volume). So I am aiming for a ballpark 38 to 40L (max) with driver in the box. All simulations in previous posts were done assuming a 35ish litre cabinet volume.
I significantly thickened the triangular sections but due to driver size, I am not able to make full triangular sections as you showed.
The Faital pro 15PR400 can be easily accommodated but the NERO SW800, due to its large ferrite magnet is making things difficult..
The bracing near the middle section is 20mm x 18mm (I can increase that 20mm a tiny bit more if that helps things).
Updated bracing scheme
The cabinet volume with all the bracing is about 44L now. (Driver eats 6L volume). So I am aiming for a ballpark 38 to 40L (max) with driver in the box. All simulations in previous posts were done assuming a 35ish litre cabinet volume.
And if you make brace behind the magnet so that magnet press the brace when you screw the driver in? You leave 1 mm distance and put some rubber compund between so that driver compress it when it is tightened with screws...but you must be precise to achieve that. Ventilation hole is not covered of course...
Tannoy was doing that in some of the speakers to additionaly damp magnet because of cheap steel stamped baskets.
Just an idea....
Tannoy was doing that in some of the speakers to additionaly damp magnet because of cheap steel stamped baskets.
Just an idea....
Something to consider if you are looking for low profile braces that are effective is to use stiffer material for the braces. Plywood is OK but nowhere near as stiff as a good hardwood like white oak, hickory, merbau or whatever is available locally. Aluminium profiles or steel are alternatives. There was a good Audioholics article with some experiments and FEM simulations of bracing schemes.
The thin parts on each panel if made of a stiff enough material can do a good job of raising the resonant frequency of each panel above the subwoofers passband. In a box without much space inside there is perhaps limited value in trying to tie the corners to each other as that is already inherently the stiffest part of the box. With such a honking great magnet, making a supporting brace under the magnet with some rubber damping material seems like a really good idea to me. If the magnet is mechanically grounded it will help to stop a mass spring from throwing energy into the structure via the front baffle.
The thin parts on each panel if made of a stiff enough material can do a good job of raising the resonant frequency of each panel above the subwoofers passband. In a box without much space inside there is perhaps limited value in trying to tie the corners to each other as that is already inherently the stiffest part of the box. With such a honking great magnet, making a supporting brace under the magnet with some rubber damping material seems like a really good idea to me. If the magnet is mechanically grounded it will help to stop a mass spring from throwing energy into the structure via the front baffle.
Looks like Joseph Crowe may have got a special "reviewer's edition"
Have a look here Vineeth-
https://www.justdiyit.com/grand-comparatif-de-10-pouces-partie-1/
under the RS270-8 part.
I wonder if it a similar "feature" to this driver.
@fluid, @Sasha KC83: Thanks for the driver magnet grounding idea.. I was wondering if this huge driver is going to tear down the front baffle with its weight.. Giving a support & damping under the driver magnet might also Ahelp significantly in relieving some of that I guess..
@tktran303: Aha.. So its just some glue leftovers.. 😀
In this case, that ventilation is supposed to cool the driver or something.. as per their datasheet.. Now I am thinking whether I should remove it somehow or not.. 🤔
Maybe.. if there is any issue, it will show up in impedance plot I guess..
@tktran303: Aha.. So its just some glue leftovers.. 😀
In this case, that ventilation is supposed to cool the driver or something.. as per their datasheet.. Now I am thinking whether I should remove it somehow or not.. 🤔
Maybe.. if there is any issue, it will show up in impedance plot I guess..
And what are those 8 holes in the back of the magnet, around ventilation hole?
If you can screw the screw 🙂 inside, you could connect magnet in a very stiff way to the back panel...
If you can screw the screw 🙂 inside, you could connect magnet in a very stiff way to the back panel...
@Sasha KC83: Yes they are holes, each about 36mm deep.
But do we want to connect the magnet in a stiff way to the enclosure or create a mechanical grounding for the magnet as fluid mentioned..?
But do we want to connect the magnet in a stiff way to the enclosure or create a mechanical grounding for the magnet as fluid mentioned..?
@fluid.
I tried to draw something that resembles the mechanical grounding that you had mentioned above. Will something like this work?
The raised portion at the bottom with the black 1inch thick rubber material topping it. The driver magnet rests on this?
Here the above thing is connected to only one wall (the bottom one). Is their a need to somehow connect it to more walls?
I tried to draw something that resembles the mechanical grounding that you had mentioned above. Will something like this work?
The raised portion at the bottom with the black 1inch thick rubber material topping it. The driver magnet rests on this?
Here the above thing is connected to only one wall (the bottom one). Is their a need to somehow connect it to more walls?
Sort of. I would make the magnet brace stronger, either as a T or U shape to tie to the back and bottom panels to spread the force. It might just be a visual representation but the damping is thicker than I would look to use.
@fluid.. ok.. I had put 1inch thick rubber material in the pic above. How much thicknedd would need to be put..?
I have more very basic doubts. Are the modes described in this article
https://www.audioholics.com/loudspe... titled,acoustic output and lowering fidelity.
the same as the box modes that we get in VituixCAD in the enclosure tool, based on the box dimensions?
I have more very basic doubts. Are the modes described in this article
https://www.audioholics.com/loudspe... titled,acoustic output and lowering fidelity.
the same as the box modes that we get in VituixCAD in the enclosure tool, based on the box dimensions?
That depends on what material you can source. Something that thick would either be very stiff or super squashy. I was thinking more like 5 to 10mm sorbothane or neoprene. Enough to stop the magnet from being rigidly attached but stiff enough to transfer the load. I would also make the support follow the shape of the magnet so it supporting all the way around not just at a point.
No that article has a link to plate theory in it. Where the panels themselves are plates and have natural resonance based on their dimensions, materials and how they are supported. Something with a natural resonance in the subwoofers passband can be excited by program. Moving the natural resonances outiside the passband by supporting the plates in the right positions with bracing.
More like this calculator
https://calcdevice.com/rectangular-plate-vibration-frequency-id226.html
The Vituix calculator is more like a room mode simulator based on the distances in the cabinet internals.
Yes, small brace will do nothing. 15 incher with heavy cone will stress-the-s$#t-out-of-the-box, they are not comparable to sissy little audiopile drivers of 5 - 8 inches. 🙂
I would make ring like four braces in the back so that magnet gets tightly inside and decouple it with strips of Blue Tack or something similar...
I would make ring like four braces in the back so that magnet gets tightly inside and decouple it with strips of Blue Tack or something similar...
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Nothing exciting..
Just a 'free air' impedance measurement of the NERO 15SW800 driver (measured in probably a non-optimal position, driver facing up, with a 1m long AWG 16 wire connected to the driver). Measurement was done using the Dayton DATS V3. Driver is not "broken in"
Just because I couldn't keep myself from doing something with that new driver.. 😀
Looks close enough to the Factory measurements in terms of those accidents around 250Hz and 1.5kHz
Just a 'free air' impedance measurement of the NERO 15SW800 driver (measured in probably a non-optimal position, driver facing up, with a 1m long AWG 16 wire connected to the driver). Measurement was done using the Dayton DATS V3. Driver is not "broken in"
Just because I couldn't keep myself from doing something with that new driver.. 😀
Looks close enough to the Factory measurements in terms of those accidents around 250Hz and 1.5kHz
I would just make one at the bottom for the magnet to rest on. Magnet mounting is a real pain to get right. Making a damped support brace is much easier.
There is something a little funky just below 30Hz. Could be a measurement artefact from the test setup. Otherwise the surround and main breakup resonances are there.
Inspired by the magnet supporting ideas above, the friend who makes enclosures for me drew this bracing scheme.
The circle, after damping with 5mm neoprene holds the driver magnet. Overall, the braces are much thicker than the ones I had in my diagrams above.
The external dimensions remain the same. (W x D xH) = 52cm x 28cm x 46cm.
The internal volume after deducting all thr bracing and driver occupied volume is 36 litres
The circle, after damping with 5mm neoprene holds the driver magnet. Overall, the braces are much thicker than the ones I had in my diagrams above.
The external dimensions remain the same. (W x D xH) = 52cm x 28cm x 46cm.
The internal volume after deducting all thr bracing and driver occupied volume is 36 litres
That is an interesting bracing scheme, and it should stiffen the cabinet walls and support the enormous 20 kg diriver. I would not attempt such a complicated fabrication, but a professional woodworker might find it quite doable.
Another option is to use double the thickness of all cabinet walls, not just the baffle. This has a significant stiffening effect.
j.
Another option is to use double the thickness of all cabinet walls, not just the baffle. This has a significant stiffening effect.
j.