I searched a little on google and found this.
A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration | Dagogo | A Unique Audiophile Experience
Havent read it myself, but von sweikert is building nice speakers, so there might be a chance of some goodies in the text. And its not that long
A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration | Dagogo | A Unique Audiophile Experience
Havent read it myself, but von sweikert is building nice speakers, so there might be a chance of some goodies in the text. And its not that long
Hi Tordenguden. That paper looks very interesting. One problem. I was unable to see the graphs that he referred to in the text. Any thoughts on how to access them?
EDIT: Okay. Found the same paper on his own site and they were there......all good. And thanks for the reference.
Cheers,
Jonathan
EDIT: Okay. Found the same paper on his own site and they were there......all good. And thanks for the reference.
Cheers,
Jonathan
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see from my limited experience this entire discussion depends on the size of the cabinets. Large panels definitely favour the stiffer materials like bamboo ply. tiny little braced panels really don't seem to make much difference to the overall sound when its MDF, ply or OSD.
so for what its worth, i think when you look at the costs involved, a mixture of materials is more appropriate, especially with a big cabinet. for a small enclosure where a pair can be made from 1 sheet of ply, then it really comes down to the drivers you're using. a cheap pair of drivers doesn't really warrant spending a fortune on void free bamboo ply for example in my eyes as the majority of the problems with the sound is coming from the driver anyway.
As I understand it some of the full range people say the MDF is "dead" or "takes the life out of the music"...........that is obviously a pure subjective observation....
I have a paper somewhere around here which I found very helpful. They did some very sensible tests and found that it was the length of the reverberation time from cabinet vibrations that was the most influential factor and minimizing that reduced colouration assisted audibility. They concluded that the B&W Matrix system was very good from that point of view.....
Also I think if you do a "search" in this forum you will find quite a bit of material on your question.
Cheers, Jonathan
I have a paper somewhere around here which I found very helpful. They did some very sensible tests and found that it was the length of the reverberation time from cabinet vibrations that was the most influential factor and minimizing that reduced colouration assisted audibility. They concluded that the B&W Matrix system was very good from that point of view.....
Also I think if you do a "search" in this forum you will find quite a bit of material on your question.
Cheers, Jonathan
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True, but what they are referring to is founded in basic mechanical engineering / physics. It is, however, circumstance dependent. The critical point is that it is not possible to eradicate panel resonance; all you can do under practical conditions is try to shunt them to somewhere they're less likely to be excited, i.e. down, below the functional BW of the cabinet, or up, above it. Going downward is very difficult with bass enclosures, since panel Fs only drops to ~0.707 for every doubling of thickness.
The main 'problem' with MDF is that it's dense, but not all that stiff. Typical MOE values are that you'll need between 1 1/8in - 1 1/4in panel thicknesses to ~equal the stiffness of BB ply, and slightly more for one of the top grades, e.g. apple-ply, a quality bamboo ply etc. A higher ratio of stiffness / weight generally makes it easier to push panel Fs up, above the operating BW of the box, where there is little energy available to excite it, and they can be more easily damped out. Bracing further helps with that. Since MDF isn't the stiffest material under the sun, this is somewhat harder to achieve, and it usually requires somewhat more panel damping than is commonly used. The net result that can (can) thus occur is the low-level delayed panel resonance combs with the direct output of the driver, like any other delayed source would. That's where the 'sucking the life out' business comes from. It's not invariable, but nor is it unknown, and can be measured.
The main 'problem' with MDF is that it's dense, but not all that stiff. Typical MOE values are that you'll need between 1 1/8in - 1 1/4in panel thicknesses to ~equal the stiffness of BB ply, and slightly more for one of the top grades, e.g. apple-ply, a quality bamboo ply etc. A higher ratio of stiffness / weight generally makes it easier to push panel Fs up, above the operating BW of the box, where there is little energy available to excite it, and they can be more easily damped out. Bracing further helps with that. Since MDF isn't the stiffest material under the sun, this is somewhat harder to achieve, and it usually requires somewhat more panel damping than is commonly used. The net result that can (can) thus occur is the low-level delayed panel resonance combs with the direct output of the driver, like any other delayed source would. That's where the 'sucking the life out' business comes from. It's not invariable, but nor is it unknown, and can be measured.
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Hmmm. The link on the VSA site goes directly to the DAGOGO. Did I miss something?
From all that I can gather, "life" is an exaggerated treble. Think Lowther. Any driver that has a rising response has "life". Cabinets with plywood walls that are not properly damped will add is own sound to the speaker and are "live". A properly build MDF cabinet adds nothing to the sound of the speaker and is therefore "dead". Go figure.
I've gone through the MDF stage and am now using 12mm plywood with stiffeners. Two reasons: 1) Those I am trying to sell speakers to tend to think that MDF is inherently an inferior product based of price. 2) MDF is ***** to work with.
Bob
From all that I can gather, "life" is an exaggerated treble. Think Lowther. Any driver that has a rising response has "life". Cabinets with plywood walls that are not properly damped will add is own sound to the speaker and are "live". A properly build MDF cabinet adds nothing to the sound of the speaker and is therefore "dead". Go figure.
I've gone through the MDF stage and am now using 12mm plywood with stiffeners. Two reasons: 1) Those I am trying to sell speakers to tend to think that MDF is inherently an inferior product based of price. 2) MDF is ***** to work with.
Bob
Isn't that funny Bob. I don't mind working with MDF at all. I'd never use it for loudspeakers mind you because I'm a believer that if it's dead, it should be on the grill not hooked up to my amp.
Seriously, regardless of cause and effect, I wonder how many persons have had the opportunity to listen to identical systems in an A/B test with the only difference being the cabinet material?
Turns out I prefer the coloured sound, if that's the correct name, as I too am of the ilk that MDF sounds lifeless.
Seriously, regardless of cause and effect, I wonder how many persons have had the opportunity to listen to identical systems in an A/B test with the only difference being the cabinet material?
Turns out I prefer the coloured sound, if that's the correct name, as I too am of the ilk that MDF sounds lifeless.
Scottmoose has some good observations on the sonic character of MDF. Another couple of reasons that I think it isn't the best is that most of its physical strengths as a material derive from its resin binder that basically bonds wood waste material and which proportionally influences its sonic signature, unlike plywood where the resin, used in a much smaller average quantity, only bonds the wood layers which themselves add a moderate amount of variability layer to layer due to wood differences and grain orientation.
This is not to say that MDF would sound worse than all plywoods by any means, but it prevents it from achieving an acoustic standard as high as something like baltic birch void free plywood which has higher strength, stiffness and better internal damping than MDF does, as well as a less uniform and 'plasticky' resonant tendency.
This is not to say that MDF would sound worse than all plywoods by any means, but it prevents it from achieving an acoustic standard as high as something like baltic birch void free plywood which has higher strength, stiffness and better internal damping than MDF does, as well as a less uniform and 'plasticky' resonant tendency.
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Thanks Scottmoose.
I wish I could find the article but I am pretty sure that of the MASS, STIFFNESS, DAMPING trio, they were very keen on at least increasing the stiffness and damping. Anything that reduced the length of the reverb' time was advantageous.......subjectively. And looking back I think I badly mangled some syntax in #5. It was supposed to mean "the end result was to reduce colouration".
Bob. Likewise.
I found the original on the von Sweikert own site but it was tucked in under another article and promo' for their "UniField Model Two" system The paper starts at page six of that section! Not at all obvious. This is the "Whoopee Do" version WITH graphs etc.
Cheers, Jonathan
I wish I could find the article but I am pretty sure that of the MASS, STIFFNESS, DAMPING trio, they were very keen on at least increasing the stiffness and damping. Anything that reduced the length of the reverb' time was advantageous.......subjectively. And looking back I think I badly mangled some syntax in #5. It was supposed to mean "the end result was to reduce colouration".
Bob. Likewise.
I found the original on the von Sweikert own site but it was tucked in under another article and promo' for their "UniField Model Two" system The paper starts at page six of that section! Not at all obvious. This is the "Whoopee Do" version WITH graphs etc.
Cheers, Jonathan
And there is nothing wrong with that. Everything in the chain colors the sound to one degree or another, and everyone hears different. So pick your favorite color!
[rant]
It annoys me to no end to be told by a zealot that his is the only possible way to get acceptable sound. As I am older that many members' fathers, I have had a bit of time to establish what sound right to me!
[/rant]
Bob
Amen to that.
Truth to tell, I have compared a couple of boxes in birch ply & MDF to the same basic design. No measurements alas, just going by my ears, so YMMV of course. The boxes were not especially large (small floorstanders, 5in midbass + tweeter), and had a modest amount of internal bracing. The damping was somewhat more extensive in the MDF box, and its front baffle was doubled, so they weren't quite identical, but within the context of what they were tried to get the best performance practical. The MDF box was heavier of course, so a bit harder to move about. Bigger boxes & I suspect you'd get more obvious differences without extra work with the MDF version. As far as these little floorstanders went, there weren't all that many differences. I still leant toward the plywood cabinet as having less colouration, but there was very little in it.
I have a certain liking for the Avalon approach of using extremely massive front baffles to give a solid mounting point for the drive units, and a high-stiffness carcass. It does make them a swine to move about though. I can see the appeal of the hyper-thin-wall types put out by companies such as Ocellia though (I heard an Oscellia model a couple of months back & liked it). Probably the BBC had the most neutral types of all, though tricky to achieve with larger enclosures. Name your poison gentlemen. http://www.youtube.com/watch?v=wcRSwo9bGHQ
Truth to tell, I have compared a couple of boxes in birch ply & MDF to the same basic design. No measurements alas, just going by my ears, so YMMV of course. The boxes were not especially large (small floorstanders, 5in midbass + tweeter), and had a modest amount of internal bracing. The damping was somewhat more extensive in the MDF box, and its front baffle was doubled, so they weren't quite identical, but within the context of what they were tried to get the best performance practical. The MDF box was heavier of course, so a bit harder to move about. Bigger boxes & I suspect you'd get more obvious differences without extra work with the MDF version. As far as these little floorstanders went, there weren't all that many differences. I still leant toward the plywood cabinet as having less colouration, but there was very little in it.
I have a certain liking for the Avalon approach of using extremely massive front baffles to give a solid mounting point for the drive units, and a high-stiffness carcass. It does make them a swine to move about though. I can see the appeal of the hyper-thin-wall types put out by companies such as Ocellia though (I heard an Oscellia model a couple of months back & liked it). Probably the BBC had the most neutral types of all, though tricky to achieve with larger enclosures. Name your poison gentlemen.
http://www.youtube.com/watch?v=wcRSwo9bGHQ
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Using the knuckle rap test:
Treated MDF in cheap boxes can be surprisingly dead with various resonances. It's all about keeping them out of your driver passbands.
Thick hardwoods come next, then granite and finally composite resins.
The composite resents hurt just as much as the granite to hit with a knuckle.
There is a process here where large institutions get 'rocks' made for the entrance and I want to talk the creators into making a speaker mould for a 2-way stand mounted beveled box, like a WATT top enclosure. It will be easier than I attempting to bevel cut granite!
Treated MDF in cheap boxes can be surprisingly dead with various resonances. It's all about keeping them out of your driver passbands.
Thick hardwoods come next, then granite and finally composite resins.
The composite resents hurt just as much as the granite to hit with a knuckle.
There is a process here where large institutions get 'rocks' made for the entrance and I want to talk the creators into making a speaker mould for a 2-way stand mounted beveled box, like a WATT top enclosure. It will be easier than I attempting to bevel cut granite!
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