Widerange dipole with Karlson Couplers ? - diyAudio
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Old 17th April 2012, 04:31 PM   #1
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Default Widerange dipole with Karlson Couplers ?

Some pics and quick measurements ...

From left to right:

A) Karlson Coupler from 60mm PP tube, length about 37cm
B) Burst decay, rear of driver covered with several layers of cloth, coupler slightly stuffed
C) FR and THD (Distance about 1m, 15 degrees vertical above axis
D) Group delay with device as shown
E) Group delay using a closed rear chamber

Within 5 degrees the highs are quite flat, more than 15 degrees off axis
causes noteable falling response >2Khz, radiation in highs is pretty narrow.

Lower cutoff frequency about 300Hz.

What about using 2 of such devices mounted in opposite direction and
adjusted (dipole path length) to have efficient dipole radiation down to
<=300Hz ?

Could be a pretty compact and efficient widerange device ...

Driver used experimentally is

http://www.tb-speaker.com/detail/1208_03/w2-748sg.htm

Of course some tweaking will be needed to make it acceptable quality ...
Attached Images
File Type: jpg K-Coupler_Length37cm.jpg (359.8 KB, 489 views)
File Type: jpg K-Coupler_01_BurstDecay.JPG (318.0 KB, 457 views)
File Type: jpg K-Coupler_01_FR.JPG (233.8 KB, 438 views)
File Type: jpg K-Coupler_01_GroupDelay.JPG (104.0 KB, 423 views)
File Type: jpg K-Coupler_00_GroupDelay_RearChamberClosed_15DegAboveAxis.JPG (100.9 KB, 409 views)
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Last edited by LineArray; 17th April 2012 at 05:34 PM.
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Old 17th April 2012, 05:23 PM   #2
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Original and interesting...

some interested questions :

>>>what's the profile of the tube cutting and how do you manage the realisation ?
>>>what's the efficiency gain if any ?
>>>do you have a curve of the naked driver measured in the same conditions ?
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Old 17th April 2012, 05:32 PM   #3
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Hi Radugazon,

cannot answer right now,

comparison between

"closed rear chamber only"

and

"closed rear chamber + coupler" should be possible

Output of naked driver at 300Hz is close to nothing
of course ...

Cutouts have been done "by estimaton" using metal
shears ("L" and "R" type) and sanding the slot a bit
afterwards ... no rocket science necessary.
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Old 17th April 2012, 05:57 PM   #4
IG81 is offline IG81  Canada
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Some large K-tubes were tried before, but not by me. They are great for HF. Might be a bit harder to make them work for midrange duty.

IG
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Old 18th April 2012, 01:23 AM   #5
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If no rocket science, I can give it a try.
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Old 18th April 2012, 10:28 AM   #6
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Rear of driver wrapped in cloth roll

Rear wrapped driver vs. rear wrapped driver + front coupler

No stuffing of coupler like in first post, now shows more resonant bahaviour

Pics:

A) On Axis at 1m distance

B) Same but, 15 degrees off axis (above and beside the slot)

Blue : coupler
Red : No coupler
Black: Gain

The more balanced output above lower cutoff in the first post,
is mainly achieved by stuffing.

Refinement of the slot contour may also be possible, but i guess
there will be no balanced midrange without a certain amount
of damping.

Maybe a resistive pressure chamber can give smilar effects using
a smaller diameter tube.

In current arrangement - cross section of tube equal to
membrane area - there is no gain at HF and the top end
is significanlly reduced off axis.

Effects at LF do not look too different from baffling the driver,
but the lower cutoff is steeper.
Attached Images
File Type: jpg CouplerVsBare_RearCloth_1m_00Deg.JPG (183.8 KB, 81 views)
File Type: jpg CouplerVsBare_RearCloth_1m_15Deg.JPG (186.8 KB, 58 views)
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Last edited by LineArray; 18th April 2012 at 10:57 AM.
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Old 18th April 2012, 12:01 PM   #7
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The first say 10cm are "unslotted" maybe top end
would improve, using a slot starting at the throat
of the device like in known HF designs.

What to make of it (instead dropping into the waste bin) ?

When used in dipole configuration maybe for annoucement at
railway platforms ...


Could be used in situations where a 25x25cm baffle for
dipole mids has disturbing looks.

Maybe optimize for smooth midrange >250Hz and use a
dedicated tweeter/supertweeter design (e.g. back to
back domes or dipole planars).

At least it has low profile and only little effect
on radiaton of any HF transducer mounted close to it.

3-way using a cardioid bottom woofer, this device+tweeter
elevated using a low profile "transparent" stand or "flying" ?
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Last edited by LineArray; 18th April 2012 at 12:07 PM.
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Old 18th April 2012, 12:13 PM   #8
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Well...some basic thoughts :

On the non stuffed plots, there's a resonance at 450 Hz, is your tube 19 or 38 cm long ? This would be too beautiful to be true. You have to try with a longer one to see what happens.

Look at this 180 kg wonder made in Germany :

Click the image to open in full size.

And as you are here enjoy the interactive view.. We can suppose
that there is a 1" inside, so high passed around 1500 Hz, but the tube looks very long, probably 1 meter or more, and the slot is relatively shorter than yours. It's also inclined at 12 degs. If there is some logic in the high end, maybe this design is to consider.

I have seen also in a 1960 optimist paper that the opening "approximates an exponential variation", maybe you have to make the things seriously with a template.

About the directivity, if you have such an increase off axis (on the side ?) it's then a polar in V, or a ring if we think in 3D. Not good...

Last thought, you have to try with an other pipe on the back of the driver as in your original idea. With different lengths, this could be a way of modulating the resonance, and the compound horns have some interesting properties.
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Old 18th April 2012, 12:19 PM   #9
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Quote:
What to make of it (instead dropping into the waste bin) ?
A device for blowing soap bubbles, maybe they will go out oval.
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Old 18th April 2012, 12:32 PM   #10
IG81 is offline IG81  Canada
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FWIW, some measurements I took of the Transylvania Power Company "The Tube", 1" diameter, 5.3" long. Drivers are Selenium D220Ti, P.Audio BM-D440 and BMS 4550.

Click the image to open in full size.

Such device don't really have much gain like horns do, but they are very uncolored and natural sounding IMO.

Getting good HF to be reproduced and dispersed might be hard in tubes of larger diameter.

IG
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