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Old 5th May 2009, 02:35 PM   #1111
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...Any resonant system that has finite Q will oscillate at the driven frequency in steady state. When the input is removed the system will respond according to its natural (transient) response from the state it was in when the input was removed and decay, ultimately oscillating at its natural frequency, if the damping is small (i.e. the system rings). ...
Hi JPV,

Actually I wasn't referring to your posts. They were just what I had considered posting. A light of sanity. I was just amused that this comes down to agreeing with what I posted 5 days ago on page 42.

That's the problem with Inet discussions. The feed back loop has too long a delay. Sitting around a table and this would have ended before it began.
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Old 5th May 2009, 02:47 PM   #1112
gedlee is offline gedlee  United States
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Originally posted by JPV


I understand. This is the difference between lumped parameters with differential equation and only influence of initial conditions and distributed one with partial differential equation that must include boundary conditions.

But at low frequencies in small rooms, the acoustical system is more like a lumped parameter one and there, don't you think that this damped resonance frequency effect is existing?


JPV
Yes, of course there is a shift, its just that this is usually not seperated out as a factor in acoustics. Its just part of what we call "resonance", which are "eigenvalues" and always contain the damping.


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Originally posted by john k...
Five days of "quién es más macho".
We all know how smart you are John and how you know all of this, but this kind of comment does nothing to add clarity to the discussion. A gentleman got confused and wouldn't let go. You added to the confusion with your comments, but you did nothing to help clear it up.
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Old 5th May 2009, 04:29 PM   #1113
xpert is offline xpert  Afghanistan
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Originally posted by john k...
Five days of "quién es más macho".

Quote:
Originally posted by john k...


Hi JPV,

Actually I wasn't referring to your posts. They were just what I had considered posting. A light of sanity. I was just amused that this comes down to agreeing with what I posted 5 days ago on page 42.

That's the problem with Inet discussions. The feed back loop has too long a delay. Sitting around a table and this would have ended before it began.
Hi all,

Mr. Geddes still won't admit his mistake (wording?) regarding the gradual shift whilst decay. There is no gradual shift. He asked for a discussion that he got. It has been shown from different perspectives that he was (is) fairly wrong.

Now courtesy of JPV we have found a new"shift". It should be emphazised that this new shift has no connection to the "shift" Mr. Geddes claimed for decaying room resonances.

I would expect appologies for in some way insultant suggestions to read the books, including the gedlee litrature. But I'm afraid it's a hopeless attempt. Style ain't a must in science, but honor is.

Thank You
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Old 5th May 2009, 05:39 PM   #1114
gedlee is offline gedlee  United States
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But I'm afraid it's a hopeless attempt.
Yes, this discussion does appear to be hopeless. Can we get back to the topic.
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Old 5th May 2009, 06:07 PM   #1115
JPV is offline JPV  Belgium
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Originally posted by gedlee


Yes, this discussion does appear to be hopeless. Can we get back to the topic.
Of course it would be better.

Coming back to my practical question.

Do you believe that limited damping in a living room is worthwhile to try to improve bass.

JPV
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Old 5th May 2009, 10:45 PM   #1116
gedlee is offline gedlee  United States
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Originally posted by JPV
Do you believe that limited damping in a living room is worthwhile to try to improve bass.

JPV
Oh most deffinately. If you read my work you will find that I believe that LF damping is the single most important thing that you can do to a room to improve its sound. Multiple subs help, but nothing truely makes the sound field smooth like damping. Its just very difficult to get LF damping, especially without incurring too much HF damping. It has to be done within the structure itself. No add-on can really do this.
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Old 6th May 2009, 08:24 AM   #1117
Pan is offline Pan  Sweden
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Originally posted by gedlee
Its just very difficult to get LF damping, especially without incurring too much HF damping. It has to be done within the structure itself. No add-on can really do this. [/B]
There are several types of solutions that works very well.

- Helmholtzabsorbers
- Quarter wave absorbers
- Resistive/reactive devices like Tubetraps
- Membrane/panelabsorbers

I have used the helmholtz and membrane type and IME the membrane type is more effective in relation to its size.

I have used eight pcs. of the RPG corner traps for many years but even two of them makes a clear difference in quality if placed in the right position. The front is 60x60cm so they are not very big.

So an add on can and will do it and do it very effective indeed.

Now if you got the means to build these function into the structures of the room that's of course nice but many can not do that and then the various kinds of bass absorbers is a very good way towards high performance audio for those who rent their appartment or setting up a temporary project studio for example.


/Peter
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Old 6th May 2009, 08:29 AM   #1118
xpert is offline xpert  Afghanistan
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Originally posted by Pan

- Helmholtzabsorbers
Hi,

from what does one know that these work?

Thank You
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Old 6th May 2009, 01:30 PM   #1119
goskers is offline goskers  United States
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JPV,

I would reference you to the works of both Geddes and Toole regarding damping and the proper way to do it. Resistive membranes which are the most common on the market attenuate the upper registers much better than the low ones. An ideal situation, like Dr. Geddes mentioned, is in structural pieces which will allow your walls to flex. If this is done you keep a live room while damping the low end. This is not what most people try to do in their rooms these days but all the evidence supports having a live room which the common absorbing materials kills.
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Old 6th May 2009, 02:01 PM   #1120
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Quote:
Originally posted by gedlee
...LF damping is the single most important thing that you can do to a room to improve its sound. ... No add-on can really do this.
http://www.rpginc.com/products/modexplate/
Based on http://www.ibp.fraunhofer.de/akustik...r/index_e.html

Best, Markus
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