Re: Re: Re: and???
Which -- barring a bit of arithmetic gymnastics is exacty what i said.
It is not the only thing. Raising the panel resonance frequency also means that the resonance is less likely to get excited in the 1st place. Push it high enuff and the natural damping in the panel material is suffiicent.
No one is disputing that this technique is new... the paper i quoted in from 1972, and alot of this stuff was well understood decades early.
Earl's 2 points that brought this part of the discussion up, where that the vertical brace in the Fonken was oriented incorrectly and that a preferred bracing was a set of point braces, both points which are incorrect based on the research done all that time ago, and information that has been readily available for a looonnnggg time.
He did make some very good points about how MDF is not really stiff enuff to make an adequate brace, and that a brace with its centre cut-out is not as effective, yet we see MDF shelf braces all the time so it is clear that these simple guidelines have still not become pervasive.
dave
dlr said:
Which -- barring a bit of arithmetic gymnastics is exacty what i said.
It is not the only thing. Raising the panel resonance frequency also means that the resonance is less likely to get excited in the 1st place. Push it high enuff and the natural damping in the panel material is suffiicent.
No one is disputing that this technique is new... the paper i quoted in from 1972, and alot of this stuff was well understood decades early.
Earl's 2 points that brought this part of the discussion up, where that the vertical brace in the Fonken was oriented incorrectly and that a preferred bracing was a set of point braces, both points which are incorrect based on the research done all that time ago, and information that has been readily available for a looonnnggg time.
He did make some very good points about how MDF is not really stiff enuff to make an adequate brace, and that a brace with its centre cut-out is not as effective, yet we see MDF shelf braces all the time so it is clear that these simple guidelines have still not become pervasive.
dave
Re: Re: Re: Re: Re: and???
No question your boxes are dead silent, but maybe it's actually doing more than is necessary. I wasn't being sarcastic above (everyone expects that maybe) when I said I'd re-program myself. I see now what Dave has been saying.
It's so simple. With truly effective bracing, you drive resonance up to the point where, given the energy in the box at that frequency, it can't be excited.
There will be no need for extra panel damping, since there is next to nothing to damp. Brilliant, actually.
I owe Dave an apology for badgering him and not giving him enough credit.
HMM, if I didn't see that, maybe there IS something to this Enabl stuff...
Nah, I won't go THAT far.
ShinOBIWAN said:Dave the cabinets I build are more dead than anything I've seen from yourself, no doubt about it. What's funny is that yes I don't follow those simple guidelines you keep banging on about either.
Yours is the true way of course.
No question your boxes are dead silent, but maybe it's actually doing more than is necessary. I wasn't being sarcastic above (everyone expects that maybe) when I said I'd re-program myself. I see now what Dave has been saying.
It's so simple. With truly effective bracing, you drive resonance up to the point where, given the energy in the box at that frequency, it can't be excited.
There will be no need for extra panel damping, since there is next to nothing to damp. Brilliant, actually.
I owe Dave an apology for badgering him and not giving him enough credit.
HMM, if I didn't see that, maybe there IS something to this Enabl stuff...
Nah, I won't go THAT far.
Re: Re: Re: Re: Re: and???
There are many ways to skin a cat. I have no doubt that your speakers have dead cabinets.
Your methodology is near the brute force (but gourgeous) end of the spectrum, i try to play at the elegant/minimalist end.
dave
ShinOBIWAN said:Yours is the true way of course.
There are many ways to skin a cat. I have no doubt that your speakers have dead cabinets.
Your methodology is near the brute force (but gourgeous) end of the spectrum, i try to play at the elegant/minimalist end.
dave
I love MDF...it is cheap, easy to machine and available everywhere. I don't hear any huge differences just substituting baltic birch for MDF.
In my opinion, much of the dead cabinet hoopla is overrated. Its another one of those topics like cables that people will endlessly debate but there are far more important design considerations to focus upon.
I'll disagree with you on this one Dave.
In my opinion, much of the dead cabinet hoopla is overrated. Its another one of those topics like cables that people will endlessly debate but there are far more important design considerations to focus upon.
I'll disagree with you on this one Dave.
Re: Re: Re: Re: Re: and???
In designing my speakers I'm just taking advantage of the established research & experimental data from those who laid the ground work long before me.
And by talking about it, i'm pointing out that this work has all been done for anyone that might benefit.
dave
gedlee said:
In designing my speakers I'm just taking advantage of the established research & experimental data from those who laid the ground work long before me.
And by talking about it, i'm pointing out that this work has all been done for anyone that might benefit.
dave
Re: Re: Re: Re: Re: Re: and???
Thanx John. It is very fullfilling seeing someone put all the connections together and have the light go on. My on-going evangilism for plywood (or other light, stiff, damped panels) makes much more sense in light of the entire systems approach that i employ.
dave
MJL21193 said:
Thanx John. It is very fullfilling seeing someone put all the connections together and have the light go on. My on-going evangilism for plywood (or other light, stiff, damped panels) makes much more sense in light of the entire systems approach that i employ.
dave
Re: Re: Re: Re: Re: Re: and???
Then why keep saying MDF is unsuitable for loudspeaker cabinets? I'm not looking for compliments on my own work, that wasn't the point at all. The point is that success with MDF isn't rare, the data backs it up as a suitable material and it has additional benefits such as easy machining, easy to finish and cheap.
planet10 said:
Then why keep saying MDF is unsuitable for loudspeaker cabinets? I'm not looking for compliments on my own work, that wasn't the point at all. The point is that success with MDF isn't rare, the data backs it up as a suitable material and it has additional benefits such as easy machining, easy to finish and cheap.
Re: Re: Re: Re: Re: Re: Re: and???
My lights are on now, for sure. I can be a bit daft about some things at times.
In all fairness, the same results can be had with MDF as the panel material. My lack of confidence in it as a brace material hasn't changed. MDF panels with plywood bracing would be a good compromise.
I still don't believe there is an audible difference between these materials.
planet10 said:
My lights are on now, for sure. I can be a bit daft about some things at times.
In all fairness, the same results can be had with MDF as the panel material. My lack of confidence in it as a brace material hasn't changed. MDF panels with plywood bracing would be a good compromise.
I still don't believe there is an audible difference between these materials.
Re: Re: Re: Re: and???
And I believe is essentially not meaningful. That was my point.
Please explain why is it less likely. Facts and details, please, especially for the case of full-range drivers (your preference, no?) where it's highly unlikely that resonances will be pushed outside of that driver's passband.
For your latter statement the suggestion of using a light material that has less internal damping is contradictory to your belief that MDF is not a good material. If you want natural damping to be effective, you need a material that has getter damping properties. BB is not better compared to MDF from what the links presented earlier.
I don't accept that as factual at all at this point, especially when one gets into what counts, audibility. You have no data to counter Gedlee who does, unless you are going to challenge the veracity of what he says on that.
The final determinant is audibility as far as effectiveness is concerned. I haven't seen anything presented so far, yours included, that is in any way a reputable, factual analysis of audibility with respect to the various methods of bracing and at what point bracing, any kind, is of diminishing returns. Given Gedlees background I, for one, will accept his comments with regard to tests made on audibility. My own experience is as I said before, boxes are overrated. But it may be that full range drivers have this as an additional drawback in comparison to good 3-way, true full range systems since it's impossible to separate anything when using "full range" drivers alone.
Dave
planet10 said:
And I believe is essentially not meaningful. That was my point.
Please explain why is it less likely. Facts and details, please, especially for the case of full-range drivers (your preference, no?) where it's highly unlikely that resonances will be pushed outside of that driver's passband.
For your latter statement the suggestion of using a light material that has less internal damping is contradictory to your belief that MDF is not a good material. If you want natural damping to be effective, you need a material that has getter damping properties. BB is not better compared to MDF from what the links presented earlier.
I don't accept that as factual at all at this point, especially when one gets into what counts, audibility. You have no data to counter Gedlee who does, unless you are going to challenge the veracity of what he says on that.
The final determinant is audibility as far as effectiveness is concerned. I haven't seen anything presented so far, yours included, that is in any way a reputable, factual analysis of audibility with respect to the various methods of bracing and at what point bracing, any kind, is of diminishing returns. Given Gedlees background I, for one, will accept his comments with regard to tests made on audibility. My own experience is as I said before, boxes are overrated. But it may be that full range drivers have this as an additional drawback in comparison to good 3-way, true full range systems since it's impossible to separate anything when using "full range" drivers alone.
Dave
Re: Re: Re: Re: Re: Re: Re: Re: Re: and???
Hi again Earl,
No, how do you see contradiction? When I talk about bracing, I'm talking about structure again. MDF will not make as strong a brace as plywood.
The point is to effectively brace the box, then there shouldn't be an audible difference.
gedlee said:
Hi again Earl,
No, how do you see contradiction? When I talk about bracing, I'm talking about structure again. MDF will not make as strong a brace as plywood.
The point is to effectively brace the box, then there shouldn't be an audible difference.
Re: Re: Re: Re: Re: and???
I'm not Dave but...if I understand it correctly:
50% of the acoustic energy that the box has to deal with is from 350Hz down. If the resonant frequency of any panel in the box is in that region, the panel will (obviously) resonate.
The higher you go in frequency, the less energy there is to excite resonances. Less energy to excite plus minimal damping will stop it before it starts. Dave says that the plywoods damping properties are adequate at this frequency.
Dave: Feel free to correct me if I am getting any of this wrong.
dlr said:
I'm not Dave but...if I understand it correctly:
50% of the acoustic energy that the box has to deal with is from 350Hz down. If the resonant frequency of any panel in the box is in that region, the panel will (obviously) resonate.
The higher you go in frequency, the less energy there is to excite resonances. Less energy to excite plus minimal damping will stop it before it starts. Dave says that the plywoods damping properties are adequate at this frequency.
Dave: Feel free to correct me if I am getting any of this wrong.
Re: Re: Re: Re: Re: Re: Re: Re: Re: and???
Hi Ant,
It's not that simple. It's been long established that to build a box that doesn't vibrate, you brace. Not only do you brace, you damp as well. Also, it helps if the walls are massive and thick.
This is all absolutely correct, of course and works very well (I know from doing it).
What I was daft about, what I was told repeatedly and ignored, was that there is a more efficient way of reaching this same end. There isn't any reason to make the walls thick. There isn't any reason to line the box with roofing membrane, or lead sheets or carpet. CLD is unnecessary.
All you need to do is effectively brace the box so that no panel will resonate below 1KHz.
ShinOBIWAN said:
Hi Ant,
It's not that simple. It's been long established that to build a box that doesn't vibrate, you brace. Not only do you brace, you damp as well. Also, it helps if the walls are massive and thick.
This is all absolutely correct, of course and works very well (I know from doing it).
What I was daft about, what I was told repeatedly and ignored, was that there is a more efficient way of reaching this same end. There isn't any reason to make the walls thick. There isn't any reason to line the box with roofing membrane, or lead sheets or carpet. CLD is unnecessary.
All you need to do is effectively brace the box so that no panel will resonate below 1KHz.
Both if you don't completely isolate the driver from the cab, so if it vibrates from acoustic compression, rarefaction and/or standing waves, then we have the complex interaction of the 'dog wagging the tail' and vice versa, ergo at minimum there's a loss of acoustical-mechanical efficiency since the driver doesn't have a rigid work platform.
GM
GM
soongsc said:
Kinetic energy from the driver falls off with frequency also - at 1KHz it's nearly zero. As you know, a resonance can not be excited unless there is enough energy at that frequency to do so. Think of the opera singer who shatters the wine glass.
Kinetic energy from the drivers motion wants to push the baffle in opposition to the cones outward movement, therefore to resist this, the front baffle and the driver itself needs to be well braced to transfer this energy to the rest of the box.
A good question is "what happens to all of this energy?" If the box panels are not allowed to vibrate, they will not burn off any of this, where does it go?
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