fdegrove said:
Yeah? Where did I state that adding mass increases the natural resonant frequency?
But you're rather working against yourself since it's more difficult to damp low frequencies than high frequencies, no?. Personally I've found it preferable to go the opposite direction and get the resonant frequency as high as possible and then apply a material which has greater damping and less mass than lead.
se
Hi,
Well, there two schools of thought you can adhere to here: either lightweight, hence quick release of energy or heavy weight, heavy damping slow release of energy.
You seem to adhere to the quick energy release school of thought, I don't.
I don't see it as working against anything, neither have I encountered great difficulty in damping low frequency energy, which is the more bothersome in this case anyway.
What? You don't know what you post anymore good old Steve?
Yes you do remember, for you have already rephrased it so that you're covered.
Is it really that hard to admit a minor slip?
No, I won't argue about it.
Cheers,
Well, there two schools of thought you can adhere to here: either lightweight, hence quick release of energy or heavy weight, heavy damping slow release of energy.
You seem to adhere to the quick energy release school of thought, I don't.
I don't see it as working against anything, neither have I encountered great difficulty in damping low frequency energy, which is the more bothersome in this case anyway.
What? You don't know what you post anymore good old Steve?
Yes you do remember, for you have already rephrased it so that you're covered.
Is it really that hard to admit a minor slip?
No, I won't argue about it.
Cheers,
fdegrove said:
Quick release of energy? What are you talking about? A light weight system doesn't inherently realease energy any faster or slower than a heavy weight system. What exactly is it that you're equating to the speed with which energy is released?
Then perhaps your application of lead is bringing the panel resonance below typical audio frequencies so that you're not exicting its resonance in the first place in which case damping is irrelevant.
Rephrased what? You quoted me as saying:
Which is effectively saying that as you increase mass, you decrease the natural resonance of the system.
And said I had said the opposite previously. Well, the opposite of "Which is effectively saying that as you increase mass, you decrease the natural resonance of the system" would be "Which is effectively saying that as you decrease mass, you increase the natural resonance of the system."
So what did I rephrase? What else is the opposite of "Which is effectively saying that as you increase mass, you decrease the natural resonance of the system."?
Is it really that hard to answer a straightforward question with a straightforward answer?
I'd be more than happy to admit to a minor slip if you can show me where I made the minor slip instead of claiming I'd made a slip and refusing to tell me where I'd made the minor slip leaving me to either try and read your mind or go sifting through half a ton of posts trying to find it.
You made the claim. It's not my job to do your work for you.
No, I won't argue about it.
Fine with me. I'll just toss your unsupported claim into the pile along with all the other unsupported claims you've made in the past.
se
Hi,
Maybe inverted in phase...or was it polarity? Don't want to remember either.
Either way, quite a few of those : "against all laws of physics" quotes can be retrieved...
And as usual with Mr.Eddy, it's up to us to rub his nose in them.
Not that it's any help to people inventing logic as they go along anyway.
Cheers,
Maybe inverted in phase...or was it polarity? Don't want to remember either.
Either way, quite a few of those : "against all laws of physics" quotes can be retrieved...
And as usual with Mr.Eddy, it's up to us to rub his nose in them.
Not that it's any help to people inventing logic as they go along anyway.
Cheers,
Peter Daniel said:
Ah, ok. I see where the confusion is now.
What I was talking about here was the increased thickness of the material. When you increase the thickness of the material, you're not simply increasing mass, you're also increasing stiffness. In fact, the stiffness increases at a rate greater than the mass increases and the result is an increase in the resonant frequency.
So for example, if you have a panel made of a given material of a given thickness and a given area, if you double its thickness, while you double its mass, you more than double its stiffness.
I ran some numbers on this a few years ago and if memory serves, the stiffness increases as something on the order of the square of thickness.
Now read what I originally wrote which led to all this:
Mass and damping are two different things. Simply adding mass just lowers the resonant frequency, all else being equal.
The key phrases being simply adding mass and all else being equal. All else being equal meaning that stiffness remains the same (seeing as the natural resonance is just the square root of stiffness divided by mass). When I spoke of the heavy construction of your chassis, I wasn't speaking in terms of all else being equal.
And of course the whole point of my comment above was to point out that mass and damping aren't one and the same.
Perhaps instead of Frank suggesting I don't know what I wrote that he take the time to read what I actually wrote.
se
If it is true that the environmental vibration affects the amp sound, I would consider that an isolation of the chassis from the environment vibration (instead of isolation of the chips from the chassis) is the most probable treatment, applying pneumatic damping supports—e.g. http://www.newport.com/Support/Tutorials/Vibration_Control/v15.asp
jh6you said:If it is true that the environmental vibration affects the amp sound, I would consider that an isolation of the chassis from the environment vibration (instead of isolation of the chips from the chassis) is the most probable treatment, applying pneumatic damping supports—e.g. http://www.newport.com/Support/Tutorials/Vibration_Control/v15.asp
I'm using this pneumatic table top from Newport. Although it isolates the chassis from the stand, the construction details of chassis are important anyway. By that I mean if you use different material for spikes between chassis and the table, you will hear it
Attachments
Peter Daniel said:The first two statements are exactly the same, and not opposite of ea other. Unless I don't get the meaning of the word "opposite"
Actually the are opposite statements.
Increase mass is the opposite of decrease mass and increase frequency is the opposite of decrease frequency.
The problem is that while they're opposite statements, they're both correct. What I did was take the opposite of both elements (i.e. mass and resonant frequency) and didn't notice that the resulting opposite statement didn't conflict with the original statement.
Depends whether "opposite" refers to both elements or just the one element. If you apply it to one element, you end up with conflicting statements. If you apply it to both elements, you don't.
se
Steve Eddy said:
Actually, I see, that you indeed meant what you say.
So, is it better to get the resonant frequency below 20 Hz or go as high as you can, above 20K Hz? Or just don't worry about it and damp it?
I have to say that the two GC chassis I built were quite different. The aluminum was a massive one with 3/4" bars and 1/8" tubing. It is still dependant on the placement, and spikes and double acrylic platforms improve the sound somewhat.
The acrylic GC is kind of lighter structure, with combination of aluminum heatsinks, acrylic panels and some very thin aluminum fins connecting with main heatsink by a heat pipe. I was expecting the acrylic version to sound better, but it was not a case. It is even more fussy about the feet and spikes and the sound is not as good as aluminum GC.
Peter Daniel said:Actually, I see, that you indeed meant what you say.
Thank you!
Ideally getting resonance below 20Hz would be the best seeing as above resonance, you actually begin to isolate. But I don't see that it would be practical to get the chassis resonance down that low. Which is why I suggested previously coupling the chip/heatsink to the chassis via something which does have a resonant frequency below 20Hz. This would be easily doable with something as simple as some coil springs.
If you want to deal with structure-borne vibration, try the same thing here. Try some simple coil springs. Get the resonance as far below 20Hz as you can and make sure it's as resonant as possible (i.e. as little damping as possible).
Acrylic. Yeccch. Synthetic. Yeccch. Try wood.
se
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