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post #61 of 85 Old 11-13-2010, 07:38 PM
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Originally Posted by Bill Fitzmaurice View Post
That's fine if you know the thickness and resistivity index required of the stuffing to give a desired Qa, Ql and Qp, but as far as I can tell you don't.
I don't think any of the sims are good enough to predict exactly how much stuffing you should use or where you should put it. Fiberglass, poly and cotton all behave differently and where you put the stuffing in the box makes a big difference. The best you can do is get an idea of what needs to be done and then go to work with some stuffing in the box, checking your results with SPL and impedance measurements.

Dennis H
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post #62 of 85 Old 11-13-2010, 07:41 PM
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And now the post editing begins, gonna try and alter the Wikipedia again?
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post #63 of 85 Old 11-13-2010, 07:46 PM - Thread Starter
 
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Originally Posted by soho54 View Post
what lies? I have been saying the same things the entire time, and all throughout your linked posts.

Who said they didn't contain standing waves? they do not contain even ordered resonances though.

Where in this paper you keep siting does it refer to an even order harmonic? Right at the get go with the meat of the paper he states, odd order resonances. He never takes this back , or goes against it. He does refer to a second harmonic, but that means the 3rd order harmonic. If it is only even orders then the second is the 3rd order h., the four is the 7th order h. If you look back over the posted "sims" in the paper this is clearly visible.

I'll ask again, what lies?
roflmao!!!!
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post #64 of 85 Old 11-13-2010, 08:08 PM
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Originally Posted by catapult View Post
I don't think any of the sims are good enough to predict exactly how much stuffing you should use or where you should put it...The best you can do is get an idea of what needs to be done and then go to work with some stuffing in the box, checking your results with SPL and impedance measurements.
What you're saying is that the technique allows you to predict what might be accomplished but doesn't give you the means of knowing how to accomplish it. That takes it off table as a practical design tool, at least until someone does quantify damping material performance to the level required. Gerry Koonce is the reigning expert on that scene, maybe he'll do so at some point.

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post #65 of 85 Old 11-13-2010, 08:20 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
What you're saying is that the technique allows you to predict what might be accomplished but doesn't give you the means of knowing how to accomplish it. That takes it off table as a practical design tool, at least until someone does quantify damping material performance to the level required. Gerry Koonce is the reigning expert on that scene, maybe he'll do so at some point.
I don't really see that as a deal breaker. If you think Qa should be lower, you need more stuffing in the box. If you think Qp should be lower, you need some stuffing blocking the direct path between the driver and the port. Nothing you can't work out with an afternoon of experimenting.

Dennis H
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post #66 of 85 Old 11-13-2010, 08:25 PM
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Yeah villastrangiato, your posts have been pretty funny.

Do you even know how to calculate a resonance from a set point?

Let's use 100Hz, what is the 2nd order H? What is the 3rd order H?

Now looking back over your sited paper, where is the 2nd order H?

Look he has a pipe with a driver closing off one end with a "nominal" cutoff of 109Hz, and it is .78m long. It measures 100hz, how can this be? Well on the second page of his paper he tells you, "The pipes actual fundamental resonance fo is affected by a number of additional factors, including end correction, pipe geometry, and stuffing material." this would be apposed to the "nominal" figure, as it comes from nothing more than the physical pipe length.

Now hold up you say, how can a .78m driver ended pipe have a fundamental resonance (1st order H) of anywhere near 100Hz? Well that is easy, it is a closed end air column, and as such:
f=(Harmonic# * Speed of Sound)/4 * Pipe length.
109.9Hz =(1*343)/4*.78m
(Without end correction that is, which would lower it)

Well what if it was an open ended air column? Easy!
f=(Harmonic# * Speed of Sound)/2 * Pipe length.
219.8Hz =(1*343)/2*.78m


Wow, I guess a pipe with a driver sealing one end is considered a closed end air column. That means there are no even ordered harmonics, right? Yep, now your getting the hang of it, young man.

So what would the next harmonic be for this pipe? Let's find out.
f=(Harmonic# * Speed of Sound)/4 * Pipe length.
329.8Hz =(3*343)/4*.78m


Looking back at our sample paper this is where you will find the second peak. Wow, your right! Why did you us 3 as the Harmonic# though?

Well remember Timmy, the closed end air column only has odd ordered harmonics, so the second one is the 3rd. If there was a 2nd ordered harmonic there would be a peak at 219.8Hz, and as you can see there is not.
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post #67 of 85 Old 11-13-2010, 08:40 PM
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For clarity, I think we should define both ends of the pipe when we describe them. Open-open, closed-closed and open-closed all behave differently. The pipes we're all talking about are open-closed.

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post #68 of 85 Old 11-13-2010, 08:58 PM - Thread Starter
 
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Originally Posted by catapult View Post

For clarity, I think we should define both ends of the pipe when we describe them. Open-open, closed-closed and open-closed all behave differently. The pipes we're all talking about are open-closed.

Yes Mr. Sim, clarity would be a nice thing to have. You, JohnK, AJINFLA, Martin King, and a host of others on DIY were citing a pipe that was open on both ends to ridicule me, do you remember?

You all were so certain of what you were saying and then I pointed out that you all overlooked the minor detail that a loudspeaker was closing off one end of the pipe - MINOR DETAIL!


http://www.diyaudio.com/forums/multi...laimed-22.html


You can't have cavitation without that minor detail which results in the propagation of positive and negative going pressure pulses down towards the open end of a pipe. But when I mentioned the principle of standing waves and cavitation - it was as if I was speaking Latin. Since the circle of jerks simultaneously experienced a brain fart - I had to be the incorrect one. It couldn't have been possible that they were the incorrect ones. And so here we are - several months later. The laws of physics haven't changed. But perhaps your understanding might. Ah, who am I kidding? You'll never be wrong. You know everything about everything. Standing waves, cavitation, speaker simulators - Dennis is the guy with all the answers........
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post #69 of 85 Old 11-13-2010, 08:59 PM
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Quote:
Originally Posted by catapult View Post

For clarity, I think we should define both ends of the pipe when we describe them. Open-open, closed-closed and open-closed all behave differently. The pipes we're all talking about are open-closed.

That's just it, there is no need.

If both are open it is an open ended air column.
If an end is closed it is a closed ended air column.
If both ends are sealed it isn't an air column anymore, just a sealed enclosure.


There are no even ordered harmonics in a closed ended system. Measurements show no even ordered harmonics even in his sited paper. A null is not a harmonic.
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post #70 of 85 Old 11-13-2010, 09:02 PM - Thread Starter
 
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Originally Posted by soho54 View Post

That's just it, there is no need.

If both are open it is an open ended air column.
If an end is closed it is a closed ended air column.
If both ends are sealed it isn't an air column anymore, just a sealed enclosure.


There are no even ordered harmonics. Measurements show no even ordered harmonics even in his sited paper. A null is not a harmonic.

Hey Einstein,

Have you ever heard of a pipe or duct anti resonance? Do a google search.
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post #71 of 85 Old 11-13-2010, 09:09 PM
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Originally Posted by villastrangiato View Post

Hey Einstein,

Have you ever heard of a pipe or duct anti resonance? Do a google search.

If you will re-read the section you quoted you will see that I said, "a null is not a harmonic/resonance."

I will now add an anti-resonance is not a resonance.

The second resonance in a close ended pipe is it's 3rd order Harmonic. There is a null between the 1st and 3rd order Harmonics, but it is not a harmonic itself.
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post #72 of 85 Old 11-13-2010, 09:10 PM
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Originally Posted by villastrangiato View Post

You, JohnK, AJINFLA, Martin King, and a host of others on DIY were citing a pipe that was open on both ends to ridicule me, do you remember?

Nope. As usual, you misunderstood what we were saying.

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post #73 of 85 Old 11-14-2010, 06:27 AM
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Originally Posted by catapult View Post

I don't really see that as a deal breaker. If you think Qa should be lower, you need more stuffing in the box. If you think Qp should be lower, you need some stuffing blocking the direct path between the driver and the port. Nothing you can't work out with an afternoon of experimenting.

The problem is that you have no way of knowing whether you can actually achieve a desired Qa or Qp.

Nousaine's original article with regards to stuffing IBs used incomplete data, measuring only f3 rather than a full SPL plot. That incomplete data led him to believe that stuffing could be substituted for a larger box, which caused literally a generation of builders to make their boxes too small, assuming that they could just stuff the box and get the same result as a properly sized box. That assumption was incorrect.

This is a similar circumstance, where a builder might sim a result that can't actually be realized. My preference isn't to build a box that's too small and then try stuffing to make up for its shortcomings. Rather, build the box the correct size and use stuffing to fine tune the result.

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post #74 of 85 Old 11-14-2010, 09:03 AM
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Enough of the name calling.

Please report the next post that is out of line. Offenders will be removed.

Kyser

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post #75 of 85 Old 11-14-2010, 09:31 AM
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Look at that. What a week huh?

It's like we were thrown back in time. Everyone is extra edgy, names are flying like 3rd grade, the commercial forum guys are invading, random posts disappearing, and the mods have even had to show themselves.
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post #76 of 85 Old 11-14-2010, 10:49 AM
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Just another day at the sandbox I guess.

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post #77 of 85 Old 11-14-2010, 01:59 PM
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it feels so weird to have one's identity stolen.

villa should have called himself Vas2 or just V2 for short.

according to my view of economics the existence of villa is evidence that my trolling activity has been on the decline - you know sort of like a black market is evidence of inefficiency of the market.

maybe it's time for me to retire as the trolling sensation of the internets - make some room for younger kids and get a life in the process.

getting a life is easier said than done however
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post #78 of 85 Old 11-14-2010, 02:59 PM
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Alas, I was expecting somewhat more than resignation from our resident ubermensch hero....

.
....Crank up the SIGNAL ... cut back the noise....
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post #79 of 85 Old 11-14-2010, 04:20 PM
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Alas, I was expecting somewhat more than resignation from our resident ubermensch hero....


Uhhh..yeah..

Vas go grab a couple Red Bulls, tie up your shoes real tight, but NEVER give up.
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post #80 of 85 Old 11-14-2010, 05:21 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

The problem is that you have no way of knowing whether you can actually achieve a desired Qa or Qp.

Qa and Qp of 10 are pretty easy to achieve with stuffing. That's what I used in the sim, reduced from the default of 100 for both. Below that, you're right, you might not be able to get there in the real world.

Edit: on second thought, that's not quite right. There's a lower limit to Qa but Qp can go all the way to zero if you shove a tennis ball in the port. And reducing Qp was the major part of the sim, as shown by the impedance curves.

Quote:


My preference isn't to build a box that's too small and then try stuffing to make up for its shortcomings. Rather, build the box the correct size and use stuffing to fine tune the result.

My example was a box that was too big. Granted, it's a bad design but stuffing managed to fix it without building another box.

Another thing I like about stuffing is killing standing waves inside the box. It's not really a problem with subs but it can be with the midwoofer in a main where the cabinet dimensions are in the passband.

Dennis H
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post #81 of 85 Old 11-14-2010, 07:45 PM
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Another thing I like about stuffing is killing standing waves inside the box. It's not really a problem with subs but it can be with the midwoofer in a main where the cabinet dimensions are in the passband.

You need to stuff to kill standing waves in the low end (if the box is large enough to support them) because damping becomes less effective as wavelengths grow longer. The higher the pass band the more likely standing waves are, but also the easier it is to control them.

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post #82 of 85 Old 11-15-2010, 12:35 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

The problem is that you have no way of knowing whether you can actually achieve a desired Qa or Qp.

Nousaine's original article with regards to stuffing IBs used incomplete data, measuring only f3 rather than a full SPL plot. That incomplete data led him to believe that stuffing could be substituted for a larger box, which caused literally a generation of builders to make their boxes too small, assuming that they could just stuff the box and get the same result as a properly sized box. That assumption was incorrect.

What about the effective box size increases Dickason cites in LDC?

Do you have data that actually refutes the idea?

And why is that you never address the simple fact that thermodynamic principles solidly supports the principle?

Noah
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post #83 of 85 Old 11-15-2010, 05:55 AM
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What about the effective box size increases Dickason cites in LDC?

Read the latest edition.

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post #84 of 85 Old 11-16-2010, 10:27 AM
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I just got Amazon Kindle - WOOHOO ! ! !

It's cool
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post #85 of 85 Old 11-16-2010, 11:30 AM
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Lots of ownage in this thread. Yikes.
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