how to brace a speaker cabinet?

how much bracing i should do, is there any limitations for it?
which sort of bracing is effective and please provide me some picture of this?
any type of wood can be used for bracing?
how should i screw brace with speaker cabinet?
if i want to build speaker with 2 woofer then how much bracing is need and which position i should brace in the cabinet?
 
You can get a lot of different answers to this question. There is no one answer to do it right. But this might help to get some ideas: http://www.duelundaudio.com/downloads/Articles_Steen_Duelund/cab,_units_and_room.pdf
It references the bracing from a B&W speaker: [IMGDEAD]https://www.bowers-wilkins.com/Images/SeriesFeature/xxxlarge/800--Tech--Matrix.jpg[/IMGDEAD] but takes it a step further.
In the end you will have to decide for yourself.
 
Look up the "basslines" build for bracing the looks like it would be very effective and doesn't take up too much volume.

Hi and sorry but could you direct me to some specific thread discussing this ?
In general i think it could be interesting to look at the cabinet of the best subwoofer around.
This is an extreme situation but could give some hints.
Cabinet construction is very important for me. And not discussed enough.
Thanks and regards, gino
 

Tattoo

Member
2014-08-14 1:21 pm
Laniakea
There's two schools of thought on cabinets.

Troels Gravesen often does braced MDF:
DIY-Loudspeakers

And there's the BBC approach of light ply with damping panels:
http://www.diyaudio.com/forums/mult...ossy-cabinet-designs-harbeth.html#post3234256

The worst thing you can do is stick battens on panels of ready built boxes. This pushes the resonances higher and creates rattles. Better to add damping. :)

Bracing shifts resonances up in frequency, making them easier to hear. This is not good.

Solutions that seem to work:
For woofers you can make a casing that has resonances so high, the woofer can't excite them.
For mid and high frequencies you need the BBC method.
 
Hi and thank you All for the very valuable input on an issue that personally i find a little overlooked in speaker design, very very wrongly.
I do not want to trivialize this important issue but i read 2 statements that sound right to me.
1) if you damp to much the cabinet the energy of the woofer is dissipated through the cabinet itself and not radiated to the room (clearly a bad thing). So a very stiff cabinet is a much better solution for a bass speaker.
2) soundstage wise, it is extremely important that the front baffle stays still, that it does not vibrate back and forth in respect to the listening position. Therefore a very thick and stiff front baffle is a must for a good soundstage rendition.
I and a friend put some lead sheets inside a speaker.
The bass cleaned up clearly but also the sound was a little muted and the emission reduced (so a mixed result, not completely convincing).
Personally i would prefer a very stiff cabinet with some light damping sheets on the sides.
I would not be very worried about lateral and rear panels vibrations.
As they are much much lower in level than the front direct signal.
Thanks again and kind regards, gino
 
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Here's an interesting discussion on the subject.
From post #181 on
http://www.diyaudio.com/forums/mult...a-speaker-based-t27s-b110s-4.html#post4159401

Hi and thanks for the interesting link.
Taken the first message again ... and given that it is correct ...

Unfortunately, thicker walls will raise resonance frequencies but do not reduce amplitude.
This has been shown time and again in measurements.
If anything, Q tends to increase as mass and stiffness go up.
Cabinet walls are essentially transparent at resonance.
The only way to reduce sound transmission is with damping

i think this is very beneficial because it should be quite easier to damp higher freq vibrations
They have less energy so even a thin good panel stick to the cabinet should work fine.
If i am not wrong the very challenging ones are low freq vibrations (i.e. high energy vibes).
To me the solution is quite clear then. A very stiff cabinet with some strategically placed damping panels to absorb high freq vibrations.
And actually the best subwoofers i have listened to they all had impressive cabinets, with extensive bracing (i.e. very stiff).
High freq vibes are very easy to tame with some thin absorbing panel.
Am i right ?
Thanks again to all, gino
 
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Hi and thanks for the interesting link.
Taken the first message again ... and given that it is correct ...



i think this is very beneficial because it should be quite easier to damp higher freq vibrations
They have less energy so even a thin good panel stick to the cabinet should work fine.
If i am not wrong the very challenging ones are low freq vibrations (i.e. high energy vibes).
To me the solution is quite clear then. A very stiff cabinet with some strategically placed damping panels to absorb high freq vibrations.
And actually the best subwoofers i have listened to they all had impressive cabinets, with extensive bracing (i.e. very stiff).
High freq vibes are very easy to tame with some thin absorbing panel.
Am i right ?
Thanks again to all, gino

For subwoofers you need a very heavy cabinet witch resonates only at frequencies high enough so they are not excited.

For normal speakers you need thin walls that resonate at low frequencies witch you then damp with stuff like bitumen. Its counter intuitive for sure.

Speaker Dave is an expert on this stuff. See post #196:
http://www.diyaudio.com/forums/mult...a-speaker-based-t27s-b110s-4.html#post4160525
 
Thanks.
No measurements unfortunately.

They use the B&W method combined with a special glue that dampens vibrations of the matrix. But no damping on the panels themselves. It will shift resonances up in frequency, so they can be more easily heard.

The glue is a damper. It acts as CLD damping... something definitely not tested in those BBC papers. Just slab on thick heavy damping does something but i.m.h.o. CLD would be a better choice. I wouldn't be surprised if it lowered the resonances of the outer enclosure. Look at CLD damping on metal sheets used in cars. It lowers the resonant frequency and damps ringing. Provided that the bracing and enclosure are separated by the flexible glue. Why would it lower the resonant frequency? Because it's adding weight and not adding stiffness.

I have read the link you provided, but those two go on and on about one method. There are more ways to good results.
 
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These sort of discussions usually go nowhere, being so many different approaches possible.

But you can separate panel damping from standing wave damping in your mind. And, of course, employ certain ratios on the sides.

Bass reflex is a very different animal from closed box. Both can be panel damped, but only closed box can be stuffed to cut down standing waves. Interestingly, Steen suggested that panel damping can as easily be applied to the outside of the box, like carpet for instrance. With reflex you can use a certain amount of eggcrate foam lining the walls, but it is only effective at frequencies approaching the quarter wavelength of the foam thickness.

Steen Duelund's "Matrix" approach is applicable to closed box. But I wouldn't fancy building it! The WLM LaScala 8" reflex MDF design looks well-considered.
 
For subwoofers you need a very heavy cabinet witch resonates only at frequencies high enough so they are not excited.
...

Hi and thanks and sorry ... you mean heavy or stiff ?
This is a fundamental point for me.
For instance lead is heavy but not stiff at all.
We tried lead sheets stick to the internal panels and they do not work properly. The bass was cleaner (for instance listening to the lower notes of a piano) but the sound was not dynamic ... quite weak.
I think that stiffness is what is required because if the cabinet is not stiff but only heavy (i.e. high mass) the energy of the woofer cone pass through the woofer frame and it is absorbed by the cabinet (read wasted energy).
If the cabinet is stiff all the energy is released to the room.
The fact the the remaining vibes are high frequency vibes this is good because they are low in energy and even very thin butyl panels can tame those quite easily and efficiently.
The sound will be highly dynamic, higly transparent and completely out of the cabinet. :eek:
In a word splendid :D
Thanks again, gino
 
The glue is a damper. It acts as CLD damping... something definitely not tested in those BBC papers. Just slab on thick heavy damping does something but i.m.h.o. CLD would be a better choice. I wouldn't be surprised if it lowered the resonances of the outer enclosure. Look at CLD damping on metal sheets used in cars. It lowers the resonant frequency and damps ringing. Provided that the bracing and enclosure are separated by the flexible glue. Why would it lower the resonant frequency? Because it's adding weight and not adding stiffness.
Thin walls with CLD is exactly what I proposed.
The matrix with green glue method only dampens at certain points. This method increases the resonance frequencies, making them more audible.

These sort of discussions usually go nowhere, being so many different approaches possible.
There's one method with peer reviewed published results that clearly works very good.

Hi and thanks and sorry ... you mean heavy or stiff ?
This is a fundamental point for me.
Stiff is what you need for subs.
Sorry for the wrong terminology.
 
Sorry, but if you are referring to the BBC paper, adding bitumen to the walls is not CLD damping. It's just damping and adding mass. CLD needs a constrained layer. Bitumen alone would not fall into that category.
I'd say try it, You're still thinking about adding stiffness braces. That's not what I am typing out here. I'm talking about another variant of damping the walls (with braces not rigidly attached to those walls).

By the way, the above method of bracing is not being advised for the subwoofer enclosure. Rather aimed at a full range speaker cabinet.
 
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