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The Metronome ML
A family of ML-QQWTs
17_february_2012
A Metronome is an elegant quarter-wave
design closely related to an ML-V (Mass Loaded Voigt Pipe)
ML-QQWT? A Mass Loaded Quadratic
Quarter-Wave Tube. This 1st appeared on the scene in the form of the ConeHead (proposed
by David Dlugos for the RS 40-1354). As far as i know, this has not been built --
Andy Graddon has a half-finished (& abandoned) one in Australia. |
Thus remained the state of the ML-QQWT
until Stephen Cresswell decided to build a set of TQWTs. He came up with the Metronome. His is an outstanding & elegant execution
with high aesthetic appeal -- it is a beauty.
Just as with the ConeHead, he missed the fact that this is not a straight taper but
a quadratic taper (detail of graph below & right) and thus, in the strict sense,
not a TQWT.
Running across these from a post on diyAudio,
David D. determined the detail and Scott Lindgren modeled them as built as mass-loaded.
Steven performed the required modifications to convert The Metronome to an ML-TQQT
and reported much better performance. It also turns out that Martin King
models show that a QQWT performs much like a TQWT -- the big benefit a most elegant
presentation and -- hopefully -- higher WAF. |
ConeHead
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Scott & David started playing
with more drivers. Key dimensions modeled so far (most as yet unbuilt) for a number
of other Metronome ML enclosures are in the Metronome Variations Tables (with examples). These tables also have
some suggested starting points for BSC (baffle step
compensation)
Hemp Acoustics
8" (200mm) in Metronome
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FE127e Metronomes
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The wider-than-deep profile lends
itself well to a bipole, hence the Bipole FE126e. The FE167 & 207 came next and
it turns out the FE167 works in the same box as the FE207 with only a port adjustment
(and the Hemp FR8 fits too). Just as in the case of Martin King's ML-TL it looks like a number of drivers may work well
with only port (& optional filter) adjustment.
Just like a regular ML-TQWT, as long as the So & Sl (start
& end cross-section) remain the same, you are free to alter the aspect ratio
-- if you get too radical performance may be affected, but probably not before the
driver won't fit. |
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Have at them... if you build a set please report back. We will continue to add &
improve the drawings & check out more drivers.
The original FE108eS
Metronomes
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