Gino,
If you are interested in the stiff and damped enclosure approach, here's a link to a table of damping loss factors for different materials. The site is for turntable base plinths, but the basic information applies to enclosure walls too.
damping factor values : damping factors
If you are interested in the stiff and damped enclosure approach, here's a link to a table of damping loss factors for different materials. The site is for turntable base plinths, but the basic information applies to enclosure walls too.
damping factor values : damping factors
Thanks a lot for the extremely interesting link (i read great things of Vivid Audio) but this will take me all the weekend to read
and i will read it carefully for sure
Just to end for now, the nice thing is that i read one thing from a designer and the exact opposite from another, and they are both extremely praised.
So it seems that both have got it right in the end following an opposite approach
The opposite case being, if i get it right, Magico where the drivers are bolted to an extremely solid and unbelievably stiff structure, an internal frame.
The baffle is not holding the drivers and the panels just seal the cabinet like covers.
So maybe there is more than one truth
But i will read first ... i just need time
Thanks again, gino
There are allways several ways of meeting a design criteria. They differ in cost and complexity.
But what you just said about Magico is not the opposite. It's just a different version of the same. The different drivers are mounted to different internal sub structures (mass anchor) and float in regards to eachother and the outer walls?
I might be wrong as I'm no Magico expert.
Depends which Magico you are talking about.
The Q7 has the woofers bolted to the 1st baffle and the baffle bolted to the cabinet, with the mid also bolted to 1st baffle but on top of a vibration isolating layer or gasket if you will, and with the tweeter mounted from behind to the 2nd, exterior front baffle which itself is also isolated from the 1st baffle with another soft layer and with the 2nd baffle attached with threaded rods.
That's my understanding anyways.
Hi and thanks for the kind reply. Why did you get that impression ?
Yes in general to cabinet construction because i heard in some very rudimental tests the differences
Just adding some mass to the cabinet walls cleaned up the bass remarkably
So i am here to learn something more but it is difficult for me
Thanks a lot again. All reading postponed to the weekend when i will be more free, i hope
Kind regards, gino
Some links to the "heavyweights" in speaker enclosures.
Magico
http://magico.net/Technology/Enclosures/Enclosures_02.php
http://www.ultraaudio.com/index.php...-world-the-q3-loudspeakers&catid=44&Itemid=37
Rockport Technologies
http://www.rockporttechnologies.com/#/enclosures/Rockport
Perfect 8 Technologies
http://www.perfect8.com/nav/pdf/Encl...fleStudies.pdf
Von Schwikert
http://dagogo.com/a-whitepaper-the-...end-method-of-reduction-of-audible-coloration
Ascend (Bamboo Enclosure)
http://forum.ascendacoustics.com/showthread.php?2597-Sierra-The-Cabinet
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Hi and thanks a lot for the very interesting explanation.
If i understand correctly the woofer is "rigidly" fixed to the stiff structure while mid and tweeter are decoupled by means of a soft layer ?
Maybe this could be the right arrangement ? in this way the high freq vibes of the cabinet are not passed to the mid and tweeter ?
Very interesting. But still the structure is extremely rigid and the woofer is bolted to it. This is what i wanted to know in the end
And this is what i see in high end subwoofers as well.
Very rigid structure and woofer rigidly bolted to it.
In the case of a two ways of course the mid-woofer is bolted to the structure as we can see here
6moons audio reviews: Magico Mini
from what i see here i have the feeling that just a very stiff front baffle could be enough. And behind it just a decent wooden cabinet.
I believe in the importance of the execution of the front baffle more than other panels of the cabinet.
Front emission is what counts much more in the end.
And good to know that there are type of woods stiff enough to replace metal as a construction material for the baffle.
Maybe laminated ones ? anyway an extremely interesting topic. Thanks a lot to anyone sincerely for the valuable advice.
Kindest regards, gino
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Hi i have just given a look at the table ... extremely interesting.
The values for aluminium are impressive ...
damping factor 0.004
transmissibility 177.13
stiffer than steel ! it looks the perfectly rigid material ?
I cannot help but noticing that i see more and more brands adopting this material for cabinets, even if this implies huge production costs.
Maybe using a sheet of aluminium only for the extremely critical front baffle could be enough
Thanks a lot again for the very interesting link.
Kind regards, gino
SoundStage! Ultra | SoundStageUltra.com (UltraAudio.com) | SoundStage! Ultra | SoundStageUltra.com (UltraAudio.com)
The Aluminium baffle is a constrained layer construction, not just a thick piece of aluminium.
But aluminium is a material a serious DIY-er can work with (with some care). I cut my aluminium baffles with a Router. I used a sandwich construction as well.
http://www.diyaudio.com/forums/full-range/242171-making-two-towers-25-driver-full-range-line-array-42.html#post4044547
SoundStage! Ultra | SoundStageUltra.com (UltraAudio.com) | SoundStage! Ultra | SoundStageUltra.com (UltraAudio.com)
The Aluminium baffle is a constrained layer construction, not just a thick piece of aluminium.
But aluminium is a material a serious DIY-er can work with (with some care). I cut my aluminium baffles with a Router.
I used a sandwich construction as well.
http://www.diyaudio.com/forums/full-range/242171-making-two-towers-25-driver-full-range-line-array-42.html#post4044547
Hi and first of all sincere congratulations for the exceptional work done.
Really impressive and i am sure it sounds just wonderful.
Speaking instead of the baffle i see both approaches used
And i have the feeling the both can work equally well.
here is another one that also seems to work quite well and the metal sheet is single with the drivers bolted to it
i guess that a very stiff wood (maybe thicker) would give the same effect after all without the difficulty of working metal.
The same brand adopts for another even higher level model a wooden solid 6" thick baffle. So stiff and thick wood is also very good at least for the baffle.
A compromise maybe but a good one.
Congratulations again for your great works !
Kind regards, gino
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This is not true. Steel is 3 times as stiff as aluminium. But for a given mass (alu is about 1/3 as dense), alu will usually be stiffer, because the panel is thicker. And thickness is a large factor in calcuating stiffness of a panel.
What that table says is that alu rings like a bell when driven to the ressonance frequency. It needs to be damped, or the drivers must be decoupled so they don't trigger the ressonance....
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Steel is 3 times the stiffness of aluminum. Stiffness is measured by the modulus of elasticity, also know as Young's Modulus.
A short list of material stiffnesses. Multiply by 6.9 to convert to metric units (GPa).
Material.........................Modulus of Elasticity (psi)
Ceramic..........................45,000,000 - 55,000,000
Steel..............................30,000,000
Copper...........................19,000,000
Brass.............................17,000,000 - 19,000,000
Titanium.........................17,000,000 - 19,000,000
Aluminum.......................10,000,000
Glass...............................7,000,000 - 12,000,000
Marble.............................7,000,000 - 10,000,000
Carbon Fiber Composite.....6,000,000 - 10,000,000
Granite............................5,000,000 - 10,000,000
Kevlar Composite..............4,300,000
Soapstone........................3,800,000
Ipe (Brazilian Walnut)........3,200,000
Permali (Compr Plywood)...2,600,000
Concrete..........................2,500,000 - 4,400,000
Hickory............................2,200,000
Jabroc (Compr Plywood).....2,100,000
Plaster of Paris..................2,100,000
Oak.................................1,900,000
Hard Maple.......................1,800,000
Douglas Fir.......................1,800,000
Phenolic X Grade...............1,800,000
Ash..................................1,700,000
Beech...............................1,700,000
Pyrotek NAD-11 (Comp).....1,600,000
Bamboo............................1,500,000
Corian..............................1,400,000
Pine.................................1,300,000
Fiberglass Comp, Woven.....1,200,000 - 1,700,000
Baltic Birch Plywood............1,100,000
Fiberglass Comp, Mat...........700,000
HDF...................................700,000
Epoxy Resin........................450,000 - 850,000
Particle Board......................450,000
MDF...................................350,000 - 450,000
Polycarbonate......................260,000 - 380,000
Plexiglass............................250,000 - 450,000
The transmissibility deals with sound and vibration moving through the material.
Aluminum is poorly damped, with a loss factor of 0.004, so applying some form of damping would be best.
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Hi and thanks and this actually i was thinking.
Al stiffer than steel .. a little strange indeed. But i see now better.
are you sure that a bell made out of Al actually rings ?
Because i am not so sure ... i have to find something in Al and try to hit it
There is a very telling way to see how resonant is a cabinet
I have been shown by a serious speaker designer at an audio fair
The tool was something like this one ...
An externally hosted image should be here but it was not working when we last tested it.
He had of course his speakers and another one to compare
You put this mechanism on a speaker panel and action it.
If the cabinet is resonant the sound of the mechanism is amplified remarkably
On his speakers it was muted almost completely
Amazing, ultra heavy stiff and expensive speakers.
I am sure than on my speakers this mechanism would throw me out of the window for the noise ...
I will look in ebay to buy one ... very easy way to check for cabinet resonnances
Thanks again, gino
I feel we are getting a bit off topic now, but yes an alu bell or an alu tuning fork will ring... More than steel, less than Titanium if I remember correctly.
https://www.youtube.com/watch?v=altWaEyqa2c
https://www.youtube.com/watch?v=altWaEyqa2c
Try different materials together, look at this video from 5:20 on
https://www.youtube.com/watch?v=gh9n9v4bNhY
https://www.youtube.com/watch?v=gh9n9v4bNhY
You are very right ! i had not thought about it ... another clear example of metal ringing ... impressive and worrying also
https://www.youtube.com/watch?v=Yvx1Hw0Yqkg
Then i do not understand why many designers use Al for their cabinets
Just a marketing strategy ?
At least for the very bass a rigid cabinet seems the correct choice
Maybe they put something to tame the resonances i do not know
Thanks again, gino
Hi and thanks and clearly Al rings ... but then just look how popular is in high end brands ... it is surprising how many use it.
Instead this material Panzerholz .... really impressive
Do you know of anyone using it for spekars cabinets ?
I guess it is extremely rare and expensive ?
But maybe it could be a great option at least for baffles (the most critical panel i think) ?
A suitable thick baffle made out of this material should provide both stiffness and damping.
Why it is not more popular ? i guess it is much easier to work than metal.
Thanks again, gino
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Hi and again very impressive
two ringing materials bolted together they do not ring So even just a flange of the right material place in front of or behind the woofer flange could improve things remarkably ?
A material that must be both stiff and acoustically dead ?
Unbelievable ... this is great.
Maybe just two flanges of Panzerholz just for the woofers would give perceptible benefits ? ... great idea ?
Thanks again, gino
a very interesting video ... about a board of this Panzerholz
https://www.youtube.com/watch?v=P0b2gZRF1WQ
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