Design Goals / Driver Selection
Curt: Jim has asked me to design some crossovers for him back in 2004.
Unfortunately at that time I was swamped with previous commitments. When
he asked again after Iowa DIY 2006, I thought I saw a clear spot on my
plate, and accepted. This design is the fruition of that commitment, and is a
collaboration of Jim, who did the driver selection and enclosure design,
Wayne Wendel, who graciously lent us his ears and sage opinions for the
voicing of the design, and myself, as the crossover guy.
Jim had some pretty ostentatious goals with this design: He made no secret
he was looking to build a system that trumped the sound of his line arrays.
(This of course put NO pressure on the crossover designer at all.) Jim
chose the Tang Band W4-1337SA for the midrange. This driver appears to
have a well designed motor, and the phase plug and titanium cone made
for a sexy looking driver. One of Jim's design requirements was the speaker
be a true full range design. Knowing the capabilities of the Dayton
RS225S-8's from previous designs, they seemed the obvious choice to hold
down the bottom end. The extended range of the W4-1337SA's enabled a
high tweeter crossover point, and an easy cross to a ribbon tweeter. The
Fountek NeoCd3.0 seemed like a great choice. All the drivers exhibit high
marks for value, which gives this design a high performance to cost ratio.
Jim: There were several criteria that were established for the project. The
speaker has to be able to achieve high SPL's so it could be used for home
theater as well as music. The design had to be extremely dynamic and
detailed with a very large soundstage that would excel at recreating the
original performance. Placement had to be flexible and not require
positioning far away from walls. The top end had to have realistic
reproduction of triangles and cymbals while extracting the ambiance of the
recording venue. Last but not least, the bass had to be as close to full
range as possible with a reasonable size cabinet and still fit into the budget
allocated for the project. Finally, we wanted a design that was fairly efficient
to minimize amp requirements and to be a 4 ohm or higher load for the
amp. A W-M/T/M-W driver configuration was selected for its symmetrical
lobbing characteristics, visual appeal and a configuration that could meet
the criteria established for the project.
Not long after the 2006 Iowa DIY event, there was a lot of discussion about
how nice the Visaton Ti100 sounded in the midrange. The Tangband
W4-1337S stood out as a very similar driver design but with a few additional
'upscale features such as a Neo magnet assembly with copper sleeves and
a curvilinear cone which smoothes frequency response. Once the W4 was
selected as the midrange the design goals began to come into focus. The
only tweeter considered for the project was the Fountek NeoCD3.0. It fit
perfectly in the over all design goals and the extended frequency response
of the W4 allowed the ribbon to be crossed at a high enough frequency to
minimize distortion. A perfect match! Bass drivers were then considered.
There are many fine bass drivers but most are extremely expensive or are
very inefficient. The Dayton Reference RS225 eight inch drivers stood out
as the best low distortion driver at an affordable price that also would fit in a
reasonable size cabinet. They are over achievers and produce deep high
quality bass that is unexpected for a driver their size.
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The RS225S-8 drivers are NLA,
but the RS228-8, the non shielded
version have been deemed a suitable
replacement. See the excerpt from
my forum post to the right:
Statement Designs and the new RS
drivers: Winds of change or status quo?
(posted 10/08/2010 on the HTGuide.com)
It would make sense that shielded drivers
would eventually be replaced now that there is
no need for them. Remember all those old
threads asking how to shield a driver? -What
was a CRT, anyway? I forgot...
The eventual supply exhaustion of shielded
RS drivers used in the Statements,
MiniStatements, and StatementCC designs,
beg the question: Do I stock up now, or will
the replacement drivers be drop in
Here is the "new guard":
Looking at the new 8-ohm, non-shielded
driver specs, they are going to be close, but
will they be close enough?
With a little back of the envelope calculating,
and comparing the published specs, it
appears that the new unshielded RS drivers
T/S parameters suggest slightly smaller
enclosures, slightly higher f3’s and (very)
slightly lower sensitivities. The good news is
that I was told by an undisclosed source that
the new drivers were Klippel optimized.
RS225 Shielded vs. Non in the Statements
The enclosure size is fine and if the tuning is
raised 3 Hz, will come very close to the
transfer function of the shielded woofer. The
maximum modeled difference in dB is less
than .5 dB, and the f3 drops by 4 Hz for the
non shielded version model. In addition, the
enclosure size could be reduced by 20%, to
80 liters, with no increase in f3 over the
original design. The ‘new’ driver sports a
slightly smaller Sd than the ‘old’ driver (which
obviously didn’t change) which is used to
calculate the SPL, so the SPL differences may
be even smaller than modeled.
RS180 Shielded vs. Non-Shielded
MiniStatements and Statement CC Initial
The ‘new’ driver will exhibit the same f3 and
f10 with the original enclosure and tuning, but
has a more of a shelving response, so will
have up to 1 dB less output for the 1/2 octave
either side of 80 Hz. A 20% to 25% reduction
in enclosure volume along with a 4 Hz higher
tuning results in a modeled response that
closely emulates the original response and
only loses about 3 Hz of extension over the
shielded driver. This may be good news for
those who think the present enclosures need
to be more svelte...
Plug and play? Well sort of… We won’t know
for sure until we do, but based on the present
data, they may very well work acceptably well
with no crossover modifications at all.