Clearwave Loudspeaker Design
______________________________________________________________________________________________________________________________ Copyright 2010 Clearwave Loudspeaker Design. All rights reserved |
| CLD |
Melodia RA7.2
Cabinet Design:
The curved top is created with a stacked lamination technique. Each
layer is cut on a CNC machine and glued together to create the curved
"shell" for the top section. Gluing multiple layers in this fashion creates
a very stiff cabinet. The lower section of the cabinet is a traditional
rectangular enclosure rabbeted together with the top section. Everything
is then heavily braced and the side walls are laminated with a sound
deadening vinyl layer to absorb cabinet wall vibration. To further
suppress vibration and absorb standing waves, the enclosure is heavily
braced every 2.5-3 inches around the woofers.
All the walls are then lined with an additional layer of constrained layer
Sonic Barrier foam and Acousta Stuf fill to absorb standing waves in the
cabinet. The result is a very smooth impedance response with a box
tuning around 37hz.
Measured Performance:
This speaker is a solid 4 ohm speaker, but the impedance stays within
3.2-4ohms for most of the frequency band, thus making it suitable for
tube amplifiers with a rating of 50 watts or more into 4 ohm loads. Solid
state will have absolutely no problem with these either! The sensitivity is
rated at 89db/2.83v/meter.
The bass extension is an F3 of 38hz as verified with nearfield port and
woofer data, as well as the impedance plot. Since bass is so room
dependent, it is safe to say with room loading the bass will extend to the
upper 30s in most environments.
This speaker uses dual Seas Excel W18NX's, which have an advanced
motor and a rated 7mm xmax. Expect these to play around
103-104db/1watt meter before running out of steam for most music--
excluding pipe organs of course! Don't play that loud or you will ruin
your hearing anyway.
The on and off axis is very flat and is +/- 1.5dbs from 200hz-10k and +/-
2dbs from 40hz-20k with a -3db point located at 38hz. The response
favors a tweeter toed in such that the off axis is roughly 5-10degrees in
the horizontal plane, but that is a personal preference. The vertical polar
response favors the tweeter pointing directly at the ear level or slightly
above ear level. This can be achieved with toe spikes to fire the tweeter
at ear level. The power response and off axis response is clean very far
off axis in the horizontal plane thanks to the ribbon's narrow element and
the pistonic nature of a 2" Accuton midrange that covers the frequencies
that most MTMs start to beam.
For these reasons, it is more than likely why the Melodia images so well
and creates a large sound stage. Also attributing to those qualities is
the narrow baffle around the midrange and tweeter. The diffraction is
very much minimized because of the narrow surface area surrounding
the tweeter and midrange. It sure would have been easier and cheaper
to build a rectangular box, but we wanted to take this one to the max!
Crossover (the heart and soul of the loudspeaker):
In the crossover development, there was a lot of consideration placed
on the FCs (frequency cutoff) to minimize over excursion of the Accuton
midrange, allow a smooth transition between the drivers, and do so with
the best power response. Each driver was tested for overall harmonic
distortion at realistic listening levels to ensure they operate in the lowest
distortion passbands. This also helped aid in the selection of the
crossover points.
Phase alignment was also considered while designing this crossover,
which was enhanced because the acoustic centers of the mid and
tweeter are very close to being on the same plane. This allowed the
desired acoustic transfer functions without worrying about the need for
overly complex electrical circuits to hit the acoustic slopes or run into
phasing problems. Therefore, the crossover design is elegant and uses
a minimum amount of components to do the job the most effectively, but
an impedance this flat does require an additional zobel circuit/s.
High Performance Passive Components:
Don't worry, the crossover uses nice components in the crossover in
addition to the top notch drivers that were selected. Air Core inductors
are used throughout, with high quality 14 gauge series inductors where
lower DCR is needed. The caps are a mixture of Clarity Cap PX for the
woofer and midrange circuits, and Clarity Cap ESA for the tweeter.
Unlike other caps, Clarity Caps were designed using actual testing and
engineering to eliminate some of the common problems that plague
common poly capacitors.
Resistors are all Mills and absolutely no electrolytics are used in the
circuit. We want these speakers to last a lifetime, and the electrolytics
CLD measured in the past were either not within close enough
tolerances, or they degraded over time. The wire used in the Melodia is
Supra Stranded 13 gauge on the woofers, and 15 gauge on the
midrange and tweeter.
Cabinet Design:
The curved top is created with a stacked lamination technique. Each
layer is cut on a CNC machine and glued together to create the curved
"shell" for the top section. Gluing multiple layers in this fashion creates
a very stiff cabinet. The lower section of the cabinet is a traditional
rectangular enclosure rabbeted together with the top section. Everything
is then heavily braced and the side walls are laminated with a sound
deadening vinyl layer to absorb cabinet wall vibration. To further
suppress vibration and absorb standing waves, the enclosure is heavily
braced every 2.5-3 inches around the woofers.
All the walls are then lined with an additional layer of constrained layer
Sonic Barrier foam and Acousta Stuf fill to absorb standing waves in the
cabinet. The result is a very smooth impedance response with a box
tuning around 37hz.
Measured Performance:
This speaker is a solid 4 ohm speaker, but the impedance stays within
3.2-4ohms for most of the frequency band, thus making it suitable for
tube amplifiers with a rating of 50 watts or more into 4 ohm loads. Solid
state will have absolutely no problem with these either! The sensitivity is
rated at 89db/2.83v/meter.
The bass extension is an F3 of 38hz as verified with nearfield port and
woofer data, as well as the impedance plot. Since bass is so room
dependent, it is safe to say with room loading the bass will extend to the
upper 30s in most environments.
This speaker uses dual Seas Excel W18NX's, which have an advanced
motor and a rated 7mm xmax. Expect these to play around
103-104db/1watt meter before running out of steam for most music--
excluding pipe organs of course! Don't play that loud or you will ruin
your hearing anyway.
The on and off axis is very flat and is +/- 1.5dbs from 200hz-10k and +/-
2dbs from 40hz-20k with a -3db point located at 38hz. The response
favors a tweeter toed in such that the off axis is roughly 5-10degrees in
the horizontal plane, but that is a personal preference. The vertical polar
response favors the tweeter pointing directly at the ear level or slightly
above ear level. This can be achieved with toe spikes to fire the tweeter
at ear level. The power response and off axis response is clean very far
off axis in the horizontal plane thanks to the ribbon's narrow element and
the pistonic nature of a 2" Accuton midrange that covers the frequencies
that most MTMs start to beam.
For these reasons, it is more than likely why the Melodia images so well
and creates a large sound stage. Also attributing to those qualities is
the narrow baffle around the midrange and tweeter. The diffraction is
very much minimized because of the narrow surface area surrounding
the tweeter and midrange. It sure would have been easier and cheaper
to build a rectangular box, but we wanted to take this one to the max!
Crossover (the heart and soul of the loudspeaker):
In the crossover development, there was a lot of consideration placed
on the FCs (frequency cutoff) to minimize over excursion of the Accuton
midrange, allow a smooth transition between the drivers, and do so with
the best power response. Each driver was tested for overall harmonic
distortion at realistic listening levels to ensure they operate in the lowest
distortion passbands. This also helped aid in the selection of the
crossover points.
Phase alignment was also considered while designing this crossover,
which was enhanced because the acoustic centers of the mid and
tweeter are very close to being on the same plane. This allowed the
desired acoustic transfer functions without worrying about the need for
overly complex electrical circuits to hit the acoustic slopes or run into
phasing problems. Therefore, the crossover design is elegant and uses
a minimum amount of components to do the job the most effectively, but
an impedance this flat does require an additional zobel circuit/s.
High Performance Passive Components:
Don't worry, the crossover uses nice components in the crossover in
addition to the top notch drivers that were selected. Air Core inductors
are used throughout, with high quality 14 gauge series inductors where
lower DCR is needed. The caps are a mixture of Clarity Cap PX for the
woofer and midrange circuits, and Clarity Cap ESA for the tweeter.
Unlike other caps, Clarity Caps were designed using actual testing and
engineering to eliminate some of the common problems that plague
common poly capacitors.
Resistors are all Mills and absolutely no electrolytics are used in the
circuit. We want these speakers to last a lifetime, and the electrolytics
CLD measured in the past were either not within close enough
tolerances, or they degraded over time. The wire used in the Melodia is
Supra Stranded 13 gauge on the woofers, and 15 gauge on the
midrange and tweeter.
