# dealing with radial mode resonances in midrange transmission lines, ideas?



## thadman (Mar 1, 2006)

I feel modal resonances in midrange enclosures are significant enough to warrant thorough examination as to alternatives to a traditional sealed midrange, but am currently not interested in a dipole or cardiod dispersion pattern. For a traditional sealed enclosure, the largest internal dimension would have to be 1.67" to place the first modal resonance one octave past a 2khz crossover point. This is of course highly impractical. 

This has got me interested in midrange transmission lines.

As long as the line is stuffed, the resonances along the length of the line should be attenuated significantly due to the high particle velocity at the open end of the tube...but what about the resonances that propagate along the radii? 

Is there anyway to deal with the radial resonances other than building appropriately sized diffusors in the interior? Wouldn't the particle velocity be 0 at the walls and the pressure be at maximum, thus negating any absorptive effects of foam for radial modal resonances.


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## 60ndown (Feb 8, 2007)

42..


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## thadman (Mar 1, 2006)

60ndown said:


> 42..


...?


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## 60ndown (Feb 8, 2007)

thadman said:


> ...?


http://en.wikipedia.org/wiki/Answer_to_Life,_the_Universe,_and_Everything


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## thadman (Mar 1, 2006)

60ndown said:


> http://en.wikipedia.org/wiki/Answer_to_Life,_the_Universe,_and_Everything


LOL, any serious answers?


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## 60ndown (Feb 8, 2007)

thadman said:


> LOL, any serious answers?


this place (guy) makes the most sense ive ever read

http://www.decware.com/paper13.htm

http://www.decware.com/newsite/articles.html


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## thadman (Mar 1, 2006)

I guess the real question is where stuffing is used along the standing wave, the node or anti-node. Intuitively, As long as stuffing is used at the position of the node, where velocity is highest, the standing wave should be attenuated, correct?


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## 60ndown (Feb 8, 2007)

thadman said:


> I guess the real question is where stuffing is used along the standing wave, the node or anti-node. Intuitively, As long as stuffing is used at the position of the node, where velocity is highest, the standing wave should be attenuated, correct?


beats me?

i leave 'design' up to others ,

follow their lead

and build from their plans.


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## 14642 (May 19, 2008)

60ndown said:


> this place (guy) makes the most sense ive ever read
> 
> http://www.decware.com/paper13.htm
> 
> http://www.decware.com/newsite/articles.html


BS. I read the first one. There are lots of problems. First, Thiele and small parameters help to model the low frequency roll off of the speaker in an enclosure as a high pass filter. They don't have anything to do with mid band response and because of that aren't particularly useful in designing a low pass filter. Measuring the response frequency response of the driver in its baffle at several angles and considering the impedance curve of the speaker are the best way. Two days of trial and error, jumpers and resistors is one way, but in my opinion, riding a horse on the freeway to get to the airport would be a similar exercise.


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## Oliver (Jun 25, 2007)

Andy Wehmeyer said:


> ******** I read the first one. There are lots of problems, riding a horse on the freeway to get to the airport would be a similar exercise.


expanded for clarity ^^^, [ luke tear the shrine down ], this hero worship has gone on too long


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## 60ndown (Feb 8, 2007)

measuring / listening?


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## SSSnake (Mar 8, 2007)

Ahhhhh someone else who thinks Deckert is full of ish...


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## Oliver (Jun 25, 2007)

There is only one person who in his lack of understanding, thinks this is the "End All and Be All"

Chad has tried to educate him, it is slow going though.


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## 60ndown (Feb 8, 2007)

SSSnake said:


> Ahhhhh someone else who thinks Deckert is full of ish...


you ever built one of his designs?

ive built about 10 of em, they all performed very well.



a$$hole said:


> There is only one person who in his lack of understanding, thinks this is the "End All and Be All"
> 
> Chad has tried to educate him, it is slow going though.


i know you wanted a wo32, but with your 'better understanding' managed to destroy its performance.

so who has the lack of understanding?


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## Oliver (Jun 25, 2007)

dude it is varnished !


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## 14642 (May 19, 2008)

Look, I'm not prepared to say his designs don't work or top bash anyone. However, the fact that they sound good does't necessarily prove his methods or explanations to be sufficient. 20 years ago, I built cars that sounded good and I gave decent advice to others who wanted my help. Now, I have a much better understanding and much better tools. That means I can now build them more predictably and more consistently and explain how to do it more effectively.

The suggetsion that analysis and data collection can never be as good as using one's ears isn't credible--especially when it's applied to people whose ears aren't as desctiminating as an expert's. It takes a long time and a lot of practice to be able to identify anomalies accurately and apply a competent fix if one does it by listening and trial and error application of EQ, crossover, etc. can it be done? Sure. Does it take a long time? Maybe. Can I do it, after 25 years of practice? Not reliably. 

It is NOT sufficient, however, to build a design that works and then write a paper that assumes causes and the quality of remedies with only conjecture as proof. 

Analysis tools are good, but it also takes time to learn them. The beauty of analysis tools is that they provide a visual representation for things we hear. Humans are much better at integrating using their eyes than their ears. Think about this exercise:

Let's say you were blindfolded and had a volume knob and were asked to match the output level of a pink noise signal to that of a sample. The sample is played for 1 second. You must wait 2 seconds and then a pink noise sample is played for one second. You can adjust the volume of the sample each time it's played and you can try as many times as you need to. the goal is to match the level of the sound you control to that of the original sample which is only played once, at the begining. 

To me, that sounds like a pain in the ass process that's prone to error.

Now, let's say you have a graph of the first sample. You're no longer blindfolded and each time the additional sample is played, you have an opportunity to view the measured level and adjust it with the knob. Think that'll be easier? Hmmm...my money is on the eyes.

Let's say I'm going to build a house and I need to dig a foundation. Becuse I don't have much experience with tools of any kind, I decide that my choice of tools includes my hands and an atomic bomb. I decide that the bomb will be much quicker, so I use it. Then I discover that I've created a crater the size of a city rather than a hole that's 30 feet wide, fifty feet long and 10 feet deep. Hmmm...bummer. Tools suck and hands are much better because I can control the shape and size of the hole better than I can with an atomic bomb. I conclude that tools of all kinds provide less resolution than my hands. I then write a paper explaining that resolution is the most important thing to consider in a tool. i offer the results of using my fingernails and an atomic bomb as proof of the value of resolution. Since fingernails provide better resolution when digging (compared to the bomb), then they are the most appropriate tools for the job and I show a picture of the house I built to "prove" that I'm right.


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## Oliver (Jun 25, 2007)

Andy Wehmeyer said:


> Let's say I'm going to build a house and I need to dig a foundation. Becuse I don't have much experience with tools of any kind, I decide that my choice of tools includes my hands and an atomic bomb. I decide that the bomb will be much quicker, so I use it. Then I discover that I've created a crater the size of a city rather than a hole that's 30 feet wide, fifty feet long and 10 feet deep.


Best thing to do in this instance would to be to build car manufacturing facilities.

and since you're not out the money for razing the city [ done courtesy of america ], you become the top seller of automobiles and everyone is happy


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## 60ndown (Feb 8, 2007)

Andy Wehmeyer said:


> Look, I'm not prepared to say his designs don't work or top bash anyone. However, the fact that they sound good does't necessarily prove his methods or explanations to be sufficient. 20 years ago, I built cars that sounded good and I gave decent advice to others who wanted my help. Now, I have a much better understanding and much better tools. That means I can now build them more predictably and more consistently and explain how to do it more effectively.
> 
> The suggetsion that analysis and data collection can never be as good as using one's ears isn't credible--especially when it's applied to people whose ears aren't as desctiminating as an expert's. It takes a long time and a lot of practice to be able to identify anomalies accurately and apply a competent fix if one does it by listening and trial and error application of EQ, crossover, etc. can it be done? Sure. Does it take a long time? Maybe. Can I do it, after 25 years of practice? Not reliably.
> 
> ...


im not going to contest anything you say andy, your way deeper into audio then i ever will be, 

as for steve deckert, i really dont know anything other then frequenting his forums for a few years and building several of his designs.

particularly his wo32, 

id love to see you buy the plans ($40) and have someone built it for you. or build it yourself if you want.?

(i built mine for about $250, $120 for 2 x 10" drivers, $80 wood, some screws and caulk and wire, and a day of my time.)

ive never heard a subwoofer like it, the fastest most accurate sub ive ever heard by a long way.

very odd to hear a sub get down to 20 hz with 'absolute' agility and authority, and have no varience in output between 20 and 90 hz.

no eq.

it really left me 'wanting' for nothing.

and sub 60hz is why im here in the first place


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