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Multi-Way Conventional loudspeakers with crossovers

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Old 5th June 2008, 03:34 PM   #1
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Default Ribbon Bookshelf Speaker

Hi there,

this is an old project of mine, which i'd like to introduce.
Since the self developed ribbon tweeter attracted some
people i posted some pics of the 2002/2003 project.

Cheers Oliver
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File Type: jpg summary_small.jpg (14.8 KB, 377 views)
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Old 6th June 2008, 09:36 AM   #2
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great work, awesome looking speaker.

is that a port in the side?
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Old 6th June 2008, 11:38 AM   #3
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Hi rustlabs,

thank you. The slots in the side are resistive leakages.
I was inspired by some "Amphion" models from Finland at
that time.

There are some cloth layers behind the slots ...
A reflex port is placed in the back of the cabinet.

The mid-bass (Visaton AL 130) is coupled via a small ported
chamber behind the driver into a biggger main chamber.
That bigger chamber works like a usual BR cabinet.

The smaller chamber with port lowers the resonance of the
driver simply by adding mass. Above approx. 150 Hz the main
chamber is decoupled by the mass load of the inner port and
the compliance of the chamber behind the driver.

So above 150Hz the drivers "cone" looses mass and efficiency
increases ... that is compensated for in the crossover.

The leaks in the small chamber introduce a cardioid shape in
midrange distribution pattern. This way less sound is radiated
to the sides and to the rear. This works only if the sides are
not covered. It should be placed freely, even on a shelf.

The Bass goes rather deep, as i remember the cab is tuned to
approx 35 Hz, but overall efficiency is rather low. Dynamics
can be improved greatly by crossing with a subwoofer.

So it is no "play it loud" speaker, but to me it was sufficient
for most days ...

Crossover is at 950 Hz. To that frequency the AL 130 cone does
not suffer from breakup and the transition to the ribbon is
very smooth and (to most ears) undetectable.

It is a fairly complex design, but i think the best is the
tweeter. I am currently developing a new transformer for it.
For that bookshelf speaker the efficiency of the old
transformer/crossover circuit was sufficient, but i want some
more to be able to use the tweeter in different designs ...

I have attached a pic with top cover removed. You can see the
crossover with Transformer (top right), the backward chamber
for the ribbon tweeter (it is a dipole if not placed in a chamber,
stuffing has been removed partly for the foto) and the main bass
chamber with white curved plastic port.

Cheers ... Oliver
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File Type: jpg bookshelfspeakerwithribboncoverremoved_small.jpg (21.6 KB, 286 views)
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