New Light weight Vs Heavy Cabs

[JTUK]

We looked into this very carefully when buying P.A ...and there was no doubt that a wooden cab beat the composite cab hands down on sound.
Try the QSC K12 and K12W. for example.

[stevie]

[quote name='Mr. Foxen' timestamp='1377720598' post='2190937']
All of this doesn't ring true. You absolutely can compensate for the reduced self damping of thinner materials, changing the ply composition can do that. additionally all the stiffness stuff doesn't work, half the panel thickness and brace across two opposing panels will happily give most of the stiffness of an unbraced full thickness one, along with massively reduced resonance/raised resonant frequency. Observing any engineered structure shows specific reinforcement is employed over plain mass, any large concrete structure isn't just made of masses of concrete, it is made of reinforced concrete, with an interior framework giving strength with concrete over it. Bridges are not made of a solid mass, but a framework of supports.
[/quote]

You know what doesn't ring true? The idea that you can keep making material thinner and thinner and by adding bracing maintain the same properties as thicker material. It's b*llocks. Otherwise, we'd all be using cabs made out of 3mm MDF.

What does changing the ply composition mean? And yes, bridges are designed for rigidity. But they are made from strong materials to begin with, i.e. reinforced concrete or steel. You don't design a bridge by making a structure that is as light as possible and then reinforcing it with bracing, now do you?

By the way, have you any idea how stiff a church bell is?

Edited August 28, 2013 by stevie

[stevie]

[quote name='redstriper' timestamp='1377720809' post='2190944']
I'm sure they shouldn't sound so good on paper, but they work for me and all those who have used them - that's not to say they would suit everyone.
[/quote]

If they are a plywood sandwich with foam in the middle, that does sound good on paper.

[redstriper]

[quote name='stevie' timestamp='1377721873' post='2190983']
If they are a plywood sandwich with foam in the middle, that does sound good on paper.
[/quote]

I'm surprised no one else is using the idea.

[Kevin Dean]

my 1st trade was as a shipwright & I remember having radiused corners on bracing & ports made a huge difference on strength a transfer of vibration & I guess the same would be true with bass cabs .& working out how strong you actualy need it , what's the point in having something ten times stronger than it needs to be ?

[stevie]

Wharefdale in its original incarnation made some hi-fi cabinets with foam cores in the 1970s using formica, I think, as the outer panels. They worked really well but were difficult to make because they had to be epoxied, which was problematic at the time. That is the only reason they discontinued them.

Edited August 28, 2013 by stevie

[Mr. Foxen]

[quote name='stevie' timestamp='1377721718' post='2190975']
You know what doesn't ring true? The idea that you can keep making material thinner and thinner and by adding bracing maintain the same properties as thicker material. It's b*llocks. Otherwise, we'd all be using cabs made out of 3mm MDF.
[/quote]

The whole point is thinner doesn't have the same properties as thicker. Properties like weight. The other properties you engineer to be how you want.

[quote name='stevie' timestamp='1377721718' post='2190975']
What does changing the ply composition mean? And yes, bridges are designed for rigidity. But they are made from strong materials to begin with, i.e. reinforced concrete or steel. You don't design a bridge by making a structure that is as light as possible and then reinforcing it with bracing, now do you?
[/quote]

Changing ply composition is how you achieve the desired properties, there are a wide variety of different woods you can make ply form, as well as other materials that can be laminated into it. Kind of figured that was common knowledge.

And yes you do start out by making a bridge light, that way you don't need excessive amounts of material engineering to support the needless weight.

[quote name='stevie' timestamp='1377721718' post='2190975']
By the way, have you any idea how stiff a church bell is? Ding dong
[/quote]

Very stiff indeed. And with a narrow resonant band, in which they are very resonant, that's one of those engineered properties, you know how they achieve bells of different notes although the material is the same? Its engineering. MDF is a very different material that is very non-resonant, but it is very flexible. Starting to understand how material composition affects its properties now?

[Mr. Foxen]

[quote name='redstriper' timestamp='1377723068' post='2191020']
I'm surprised no one else is using the idea.
[/quote]

It is used, you can get Fearful/fearless cabs made like that. Also Nidacore ones. And the barefaced ply is dual density, so has different engineering properties from standard ply.

[redstriper]

[quote name='Mr. Foxen' timestamp='1377723671' post='2191042']
It is used, you can get Fearful/fearless cabs made like that. Also Nidacore ones. And the barefaced ply is dual density, so has different engineering properties from standard ply.
[/quote]

Great - can you post links to the other manufacturers making cabs from un-braced foam core panels please?
I can't find anything on line, but I'm very interested to see anyone else doing it, especially in the UK.

[Mr. Foxen]

[quote name='redstriper' timestamp='1377724754' post='2191070']
Great - can you post links to the other manufacturers making cabs from un-braced foam core panels please?
I can't find anything on line, but I'm very interested to see anyone else doing it, especially in the UK.
[/quote]

There were a bunch of builds if the Fearful threads on another bass forum. Years ago, and threads were huge.

Heres a googled one: [media]http://www.youtube.com/watch?v=fE3HE-T5R1Q[/media]

Dunno if unbraced. More is more with stuff.

Edit: Thread on the nidacore one, as I recall there was development of technique in it: http://www.talkbass.com/forum/f15/composite-nidacore-fearful-15-6-1-build-732771/

There was a fiberglass over foam one too, but it ended up looking pretty rough.

Edited August 28, 2013 by Mr. Foxen

[redstriper]

Thanks Mr. Foxen, some interesting reading there.

[alexclaber]

[quote name='stevie' timestamp='1377715518' post='2190826']Whilst theoretically possible in an ideal world, getting a 12mm panel as stiff as an 18mm panel requires some serious bracing – enough to make the box nearly as heavy as making it out of 18mm in the first place. The way I remember it, if you reduce the thickness of plywood by 3mm you reduce its stiffness by 50%. So a 15mm panel is half as stiff as an 18mm panel and a 12mm panel is half as stiff again. An 18mm panel is actually 8 times as stiff as a 9mm panel – and it's a lot worse if you're also using lighter materials like softwood ply.[/quote]

For someone with such strong opinions on this you're remarkably good at getting the facts wrong!

Some points to consider:

1. Panel stiffness is proportional to the square of the thickness, not the cube.
2. The resonant frequency of a panel is proportional to its stiffness divided by its mass - halve the mass and you double the resonant frequency
3. A braced panel has numerous different resonant modes - if you vary the bracing distance and methods all these frequencies can be made non-coincident
4. By having lots of different resonant modes you can easily lower the Q of all these resonances
5. Surface coatings and internal damping can significantly attenuate such low Q higher frequency resonances
6. Plywood varies hugely - for instance, baltic birch is stiff for its thickness but has poor self-damping

Here's an example of how we do bracing:

[discreet]

Wow - THAT is proper bracing.

[redstriper]

Alex, have you considered using foam core ply like that used in the Flite cabs?
I'm not questioning your production methods which are well renowned, I just wonder if you have looked at alternatives and whether you are aware of the foam core models.

[wateroftyne]

[quote name='alexclaber' timestamp='1377775016' post='2191573']


For someone with such strong opinions on this you're remarkably good at getting the facts wrong!

Some points to consider:

1. Panel stiffness is proportional to the square of the thickness, not the cube.
2. The resonant frequency of a panel is proportional to its stiffness divided by its mass - halve the mass and you double the resonant frequency
3. A braced panel has numerous different resonant modes - if you vary the bracing distance and methods all these frequencies can be made non-coincident
4. By having lots of different resonant modes you can easily lower the Q of all these resonances
5. Surface coatings and internal damping can significantly attenuate such low Q higher frequency resonances
6. Plywood varies hugely - for instance, baltic birch is stiff for its thickness but has poor self-damping

Here's an example of how we do bracing:


[/quote]

KA-POW!

[stingrayPete1977]

Now if you could make transparent outer cases Alex you would have the coolest cabs out there!

Edited August 29, 2013 by stingrayPete1977

[RandomBass]

Reminds me of my bracing model.....

[Lozz196]

[quote name='stingrayPete1977' timestamp='1377797109' post='2192033']
Now if you could make transparent outer cases Alex you would have the coolest cabs out there!
[/quote]

And no wonder that, despite their looks, they`re so tough.

A transparent one would be nice - very 70s, like the clear perspex drum kits.

[JTUK]

If you can do woodwork like that, why can't you build a cab that doesn't look like it was knocked up by a blind man in a garden shed...!!

[mildmanofrock]

Strange thing to post. I think they look superb.

[wateroftyne]

[quote name='JTUK' timestamp='1377800364' post='2192116']
If you can do woodwork like that, why can't you build a cab that doesn't look like it was knocked up by a blind man in a garden shed...!!
[/quote]

Way wrong.

[PauBass]

Wow, very interesting stuff coming up on this thread, things I had no idea about

[size=4]Well I'm going to give Barefaced a try, Alex has been very helpful and as soon as the cab is ready I'll go down to their headquarters and check it out...looking forward to it![/size]

Edited August 29, 2013 by PauBass

[sk8]

[quote name='JTUK' timestamp='1377800364' post='2192116']
If you can do woodwork like that, why can't you build a cab that doesn't look like it was knocked up by a blind man in a garden shed...!!
[/quote]

[discreet]

[quote name='mildmanofrock' timestamp='1377800541' post='2192121']
Strange thing to post. I think they look superb.
[/quote]

Me too.

[stevie]

[quote name='Mr. Foxen' timestamp='1377720598' post='2190937']
additionally all the stiffness stuff doesn't work, half the panel thickness and brace across two opposing panels will happily give most of the stiffness of an unbraced full thickness one, along with massively reduced resonance/raised resonant frequency.
[/quote]

That's wishful thinking, as anyone who has ever braced a speaker cabinet will tell you. If it were as simple as this, nobody would make cabinets with thick walls. They would simply use material that is half as thick and stick in a cross brace. Job done!

A cross brace adds stiffness at the point of contact but that stiffness quickly declines as you move away from that point. There is a formula for maintaining stiffness by bracing as you reduce panel thickness but, as I have tried to explain, you cannot keep making materials thinner ad infinitum. With a 12mm panel (birch) there is some weight saving to be made compared with a thicker unbraced panel, but if you try to make a 9mm panel as stiff as an 18mm one, you are likely to end up with something that is as heavy as an 18mm one. Quite where the point of diminishing returns lies is up to the designer, I suppose. Personally, I wouldn't want to go below 18mm to start with, not for bass anyway. But that is my opinion and I use a trolly.

Comparing a braced thinwall cabinet with an unbraced cabinet made of 18mm material is all well and good. But this assumes that companies using 18mm ply for their boxes never brace them - which is not the case.

[quote name='Mr. Foxen' timestamp='1377723525' post='2191037']
Changing ply composition is how you achieve the desired properties, there are a wide variety of different woods you can make ply form, as well as other materials that can be laminated into it. Kind of figured that was common knowledge.
[/quote]

If it's common knowledge, then do tell us what this material is and who is using it.