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Old 24th January 2009, 01:27 PM   #21
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by inertial
dear mine friend, 8,6x8,6 is not FAT, it is little!

In a bandpass the pipe must be really big, up to 50% of Sd in order to not have "wind"-turbolence from excessive air speed.

This is rilevant at high SPL, of course, so I assume you put in crises the Visatons before.........

friendly,
Paolo
Hi Paolo,

Depends on sound level what air speed will occur. Bigger would mean very long pipes and also more losses.

But explain your self pipes of 50% of the Sd I never see.

Or your mistaken them for a bass reflex and you where looking at a TL.


Theory please foundations of the claim your making Paolo. ( there no such thing as the perfect system it is always a compromise)



Today experimented with placing of the speaker.

40Hz clear audible at normal level 30Hz i bit softer 20 Hz I hear nothing bit I can hear the door vibrate with it
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Old 24th January 2009, 01:53 PM   #22
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Hey Helmuth , this is not a law court!

And no, i am not mistaking from TL .
BR are one thing ( direct radiator), bandpass are more critique ( indirect radiator).
I have published 20 years ago in my country a program for double-reflex. same problem: the tubes , when correct sized, do not enter in the proper volume!

So, empirycal evidence showed to me that 25% of SD are not sufficent, you need 40% at least, 50% better.
Very simply : one blowing, the other not.
This is the reason to make pipes exponential, to save lenght.

I think there are sure some papers in the AES , who knows?

Cheers,
Paolo
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Old 24th January 2009, 02:04 PM   #23
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by inertial
Hey Helmuth , this is not a law court!


How says.

Quote:
And no, i am not mistaking from TL .
BR are one thing ( direct radiator), bandpass are more critique ( indirect radiator).
I have published 20 years ago in my country a program for double-reflex. same problem: the tubes , when correct sized, do not enter in the proper volume!

So, empirycal evidence showed to me that 25% of SD are not sufficent, you need 40
% at least, 50% better.
Very simply : one blowing, the other not.
This is the reason to make pipes exponential, to save lenght.
I don't believe this.

Quote:
I think there are sure some papers in the AES , who knows?

Cheers,
Paolo
O.K show me Paolo and do not claim things you can't explain. Other wise this is a empty discussion.
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Old 24th January 2009, 02:17 PM   #24
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OK Helmuth, you are right, your 10" woofer at 14 mm Xmax peak to peak ,with a little port of about 75 cmq ,do not blow, never.
Ask a new patent, because it is a technical miracle!

You can of course believe what you want, I have made my experiments.
But I do not understand your "stiffness", mine friend.





Paolo
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Old 24th January 2009, 03:06 PM   #25
Helmuth is offline Helmuth  Netherlands
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Quote:
Originally posted by inertial
OK Helmuth, you are right, your 10" woofer at 14 mm Xmax peak to peak ,with a little port of about 75 cmq ,do not blow, never.
Ask a new patent, because it is a technical miracle!

Thanks

The X max is 6mm far as I know.

Quote:
You can of course believe what you want, I have made my experiments.
But I do not understand your "stiffness", mine friend.





Paolo
I want to learn some thing Paolo.

Every bassreflex has a pipe around 36cm^2. Half the area of mine fat tube.

The pipe radiates al the sound on Fo (the tuning frequency of the port) and the membrane almost stands still. See the cone extrusion on Fo by a simulation.

My simple conclusion every bassreflex has a big problem when your right.
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Old 24th January 2009, 03:31 PM   #26
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Yes, you are right about BR sizing.
Takes B&W for example. Models 800, 801 Nautilus: they have found that port are source of important measurable and audible distortion
Thus they have developed huge "strange" pipes towards the floor.
Do you think they are exxagerating?

About bandpass, you can take for example Dr. Geddes subs ULF15:
to my eyes they are very generously sized about pipes area.
You can see it at Ai website.

Cheers,
Paolo
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Old 24th January 2009, 03:45 PM   #27
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forgot this:

http://www.ai-audio.com/products_ulf15.html

Paolo
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Old 24th January 2009, 04:14 PM   #28
Helmuth is offline Helmuth  Netherlands
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Quote:
About bandpass, you can take for example Dr. Geddes subs ULF15: to my eyes they are very generously sized about pipes area. You can see it at Ai website.
I have calculated it for ya Paolo, area pipe compared to Sd is (208/1133) 1/5 and pipe length 20cm.

The FATBOY has 14cm long pipe and a pipe/piston area difference of (74/337) 1/4,5 .

Not a Big difference and de Fat boy is even better because I use also a shorter pipe.

Still no satisfying comment Paolo IMO.
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Old 24th January 2009, 04:23 PM   #29
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Oh, maybe I need glass on my eyes
1-0 for you.

Mmmmmmh, what about B&W ? Sure do you have some magazines where the port is visible.......

Paolo
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Old 24th January 2009, 06:50 PM   #30
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just to add another noble example, Dynaudio Evidence has really big
diameter ports on the back
Hoping my memory is better this time

I am not capable to remember where I have read that "formula"

Cheers,
Paolo
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