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Old 18th April 2012, 12:52 PM   #11
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Quote:
Originally Posted by Radugazon View Post

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.
I would have thought of 2 devices with own drivers first.

Although that "impedance compensation" idea using different
tubes is nice, the dipole path length might be too long, possibly
causing side lobes.

I thought of "opposite" but shifted mounting like this:

=============Driver
...........Driver==============



Concerning the "Färber" device

i cannot see any different behaviour here in principle:

http://www.faerber-acoustics.com/***...rement-big.jpg

Yes where is "on axis" (in case of my test device) ?

There seems to be a deviation of the main lobe from the
tube orientation around 15 degrees for mid frequencies
(to the slotted side), surely depending on the shape of
the slot.

The main lobe seems not to occur under same angle for
all frequencies. Main lobe for the top end seems more in
line with the tube.

My test tube is 37cm long, lambda/4 resonance seems to show
"effective acousic length" around 19cm, of course the slot
makes the pipe shorter effectively due to lowest resonance.

For better LF performance it has to grow in length, sure.
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Last edited by LineArray; 18th April 2012 at 01:14 PM.
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Old 18th April 2012, 12:58 PM   #12
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Quote:
Originally Posted by IG81 View Post
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.

...

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

Thank you for dropping the measurement, i tend to concur with your
estimation. In which frequency range do you use your devices ?

Does "uncolored" also refer to the lower end ?
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Last edited by LineArray; 18th April 2012 at 01:03 PM.
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Old 18th April 2012, 01:26 PM   #13
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Quote:
Originally Posted by Radugazon View Post

...
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.
Thank you for the link, i only had a german paper citing this one
and using the diagrams ...
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Old 18th April 2012, 01:59 PM   #14
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its interesting what could be get from bass driver in sealed box+vertical 220cm pipe with slot.. for 40-300Hz range for example.
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Old 18th April 2012, 02:09 PM   #15
IG81 is offline IG81  Canada
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Quote:
Originally Posted by LineArray View Post
Thank you for dropping the measurement, i tend to concur with your
estimation. In which frequency range do you use your devices ?

Does "uncolored" also refer to the lower end ?
I used it crossed over at both 3kHz witht the Selenium D220Ti and then 1.5kHz with the BMS 4550. Both configurations worked well, especially the 1.5kHz, but that's also because the BMS driver is really good. It was also about matching the K12 underneath.

You are correct that the highest frequencies have their main lobe on axis with the tube. However, listening with a bit of tilt towards the slotted side seems to subjectively improve dispersion. I don't know if I have data on this anywhere. I suspect a larger tube might have similar propreties, shifted down proportionally.

IG
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Old 18th April 2012, 02:10 PM   #16
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Quote:
Originally Posted by Radugazon View Post

If there is some logic in the high end, maybe this design is to consider.

http://www.faerber-acoustics.com/***...rement-big.jpg

If you compare that even to my unstuffed version out of
"poo-poo tube" - as we say here at the countryside - you may
find by far more pronounced ripple even >1Khz at the
"High End" version.

I am not very ambitious concerning my sloppy experimental design,
but accidentally the shown "High End" version's measurement uses
comparable 1/6 dB/octave smoothing ...

That thing performs grotty to say the least.

IG's measurements also strikingly show, that one can do better.

I fear they made the thing that long, because they needed
delay and are very proud on having their design "phase accurate".

Instead of compensating any delay electronically - if
necessary - they made that extra long coupler, slotted only about
half of the length.

That seems contrary to all well performing K-Coupler style tweeters
on the market.

Imposing materials often seem to hide the view on the inner
logic of a certain design.
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Last edited by LineArray; 18th April 2012 at 02:28 PM.
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Old 18th April 2012, 02:22 PM   #17
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Quote:
Originally Posted by IG81 View Post
You are correct that the highest frequencies have their main lobe on axis with the tube. However, listening with a bit of tilt towards the slotted side seems to subjectively improve dispersion. I don't know if I have data on this anywhere. I suspect a larger tube might have similar propreties, shifted down proportionally.

IG
Yes i see, tilting it down a bit or at least directing it somewhere
below your head while listening seem's preferable.

Thank you for sharing your estimation and experience.
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Old 18th April 2012, 02:38 PM   #18
IG81 is offline IG81  Canada
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Farber certainly did go for an acoustical center alignement. A longer un-slotted portion likely also provides a better load on the diaphragm. freddi has tried a Farber-style tube for the HF and liked it IIRC.

Have you though of using a Klam assymetric projector for midrange? In a way, they are akin to a stubby K-tube.

IG
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Old 18th April 2012, 02:55 PM   #19
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Originally Posted by IG81 View Post

Have you though of using a Klam assymetric projector for midrange? In a way, they are akin to a stubby K-tube.

IG
Does not seem too far from here ... do you know of experiments in
stuffing/damping such Klam devices ?

In that K-tubes it makes a big difference at LF.
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Old 18th April 2012, 03:01 PM   #20
IG81 is offline IG81  Canada
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I only remember seeing Klam-types with bare front chambers. Lining the walls could be a good idea depending on the driver's tonal balance.

IG
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