specifications - Mastering Mansion

EQUIPMENT Review
EQUIPMENT Review
s ervo c ontrol s ys tem s ends
feedbac k to the proc es s ing
unit, whic h c alc ulates variation
and injec ts a variation (feedbac k) s ignal to the amplifier to
c orrec t for c one errors . E ven
at high volume levels with full
s ervo c ontrol, the dis tortion is
kept quite low for a s ubwoofer.
In my relatively s mall primary
referenc e room, I didn’t feel
the need to lower the s ervo
s etting beyond its highes t
value (8) for minimal dis tortion.
Velodyne
DD-15
15-Inch Digital Drive Subwoofer System
Unique Power
Amplifier
Topology And
Connectivity
Figure 1
John Kotches
S P E C I F I C AT I ON S
Introduction
I’m sure that all of our Widescreen R eview readers are familiar
with Velodyne’s advertis ements touting their c ompany as being
number one in subwoofers. C ertainly that’s a bold claim, and one
that’s well worth inves tigating. We’ll be doing jus t that as we go
through this review. Velodyne is one of the longes t es tablis hed
c ons umer elec tronic s c ompany that provides s ubwoofers ––
although they did have a brief foray into c omplete louds peaker
systems. Founded in 1983 by mechanical and electrical/electronics
engineer David Hall, the c ompany is s till run by David and his
brother, B ruce Hall. Together they drive the company’s subwoofers
with their unique blend of talents; David handles subwoofer driver,
s ervo, and digital audio proc es s ing tec hnology development
while B ruc e handles the s ophis tic ated s oftware that c omes with
the Digital Drive s eries of produc ts .
One DSP To Rule Them All
A s ingle Digital S ignal Proc es s or (TI TMS 320C 2407) is us ed
for all digital processing functions in the Digital Drive subwoofers.
Als o inc luded with this partic ular DS P is a 10-bit A/D c onverter,
whic h is inadequate for the task. Velodyne uses a c ustom 20-bit,
48 kHz part for this task. This DSP is responsible for the eight-band
graphic or parametric equalizer filters, low and high pass crossovers
(if required) s ubs onic filters , and other func tions s uc h as a preset frequency contour, night mode, and serial communications. In
addition, several interrupt based routines are run as well. These
are the s ervo c ontrol and dis play, with a c ommon frequenc y of
15.75 kHz, as well as pas s ing c ommands down to any s lave
s ubwoofers in a multiple Digital Drive s ubwoofer environment
that is c orrec tly c abled between the R S -232 DB -9 ports .
E arly on in the development of the Digital Drive s oftware, the
dec is ion was made to utilize a s ys tem that s hares a c ommon
frequenc y to drive the s ervo and the NTS C ras ter s c an rate. B y
doing so, the task of setting up Digital Drive becomes a dramatically
s impler tas k––you get the benefits of a G raphic al Us er Interfac e
(G UI) ins tead of an arc haic and muc h more c omplex C ommand
Line Interface (C LI). While I make my living as a software engineer
and prefer the robus tnes s of a C LI for my partic ular applic ation,
I c an apprec iate the eas e of us e and s hort learning c urve as s ociated with a G UI for this particular application. It’s really a matter
48
Driver: 15-in multi-layer res in laminate, pus h-pull
dual voic e c oil, 1-1/4-inc h exc urs ion
Magnet: 23.75 pounds
E nc los ure: 1-inc h MDF, video s hielded, s ealed
(ac ous tic s us pens ion)
Amplifier Power: 1275 Watts R MS , 3000 watts
peak
Amplifier Features : Digital Drive s oftware, Digital
G raphic or Parametric E Q, Auto E qualization,
Mas ter/S lave for multiple s ubwoofer c ontrol, video
driver, analog L/R outputs for s ys tem c alibration,
B alanc ed Inputs , variable and defeatable
c ros s over in 1 Hz inc rements , variable phas e in
15 degree inc rements
Figure 1
Dimens ions (WHD In Inc hes ): 18 x 20 x 17.75
Weight (In Pounds ): 94
Pric e: $3,999
Manufactured In The USA By:
Velodyne Ac ous tic s , Inc .
345 Digital Drive
Morgan Hill, C alifornia 95037
Tel 408 465 2800 / Fax 408 779 9227
www.velodyne.c om
"The DD-15 c arried this off with a
remarkable ease , regardless of how
loud I had the volume setting,
exceeding 100 dB SPL."
Widescreen Review • Issue 103 • December 2005
Page 1/4
of s elec ting the right tool for the right job,
and there’s s imply no way a C LI is the right
tool for this job. Without the G UI, s etup for
the various Digital Drive parameters would
take far too long, or require vas t bac k panel
real es tate, and would be quite intimidating
to any us er to s ay the leas t.
There is a “s plit pers onality” on the main
c ontrol unit, with DS P interrupts going to
accelerometer/servo control and screen raster.
If you’re expec ting a gorgeous pres entation
on the G UI as you s ee on a typic al modern
operating s ys tem, you’re going to be dis appointed––it’s a two-c olor s c heme, blue and
white. G oing beyond this is too dear in both
C PU c omputational c yc les and memory;
both res ourc es are s c arc e in the DS P platform c urrently in us e.
What about the s ervo? It is c ompris ed of
a few pieces. One is an accelerometer, which
monitors c one motion and provides digital
feedbac k to the servo c ontrol system. In a
servo control system, the higher the feedback
rate the higher the gain is c ons idered to be
and hence (at least theoretically) the lower the
potential distortion. In the Digital Drive series,
it is very high gain, with feedbac k as high
as 15.75 kHz depending on s ettings . The
50
The amplifier included in the
Digital Drive line of subwoofers
is yet another Velodyne design.
R ather than go with an off-theshelf solution Velodyne designed
their own s witc hed mode
(C las s D) power amplifier. This
des ign is c overed by two
patents and has a unique
energy rec overy c irc uit, whic h
allows the amplifier s tage to
ac hieve elec tric al effic ienc y in
the area of 97 perc ent. This is
quite s imply as tonis hing performanc e. At maximum, the
1250-watt R MS amplifier
would not even draw 1300 watts , in other
words les s than a 15 ampere c irc uit. G iven
that only 3 percent of wall draw is radiated as
heat, the amplifier s hould remain at ambient
temperature, rather than heating up.
The plate for the amplifier is one of the
bus ies t around and features s everal unique
connections. I’ll start with video outputs––to fully
realize the potential of Digital Drive, you use a
video monitor, which is driven by the processor mentioned above with c ompos ite and S video outputs both s imultaneous ly ac tive. In
addition, a mic rophone input for the Digital
Drive E Q s ys tem is on the plate. A pair of
left and right R C A outputs is provided for
connection to your home theatre processor for
“auto” and manual equalization func tionality.
An R S -232 input and output is provided,
and these require a little explaining. The RS-232
input can be used for several functions. It can
be us ed to update the Digital Drive s oftware––and any c ustomer with a Digital Drive
future vers ions ) free of c harge. The R S -232
input can be used by a high-end remote control
s ys tem to c ontrol the s ubwoofer without a
s tandard infrared c ontrol. Finally, if you are
running multiple Digital Drive subwoofers, the
R S -232 input is us ed on s lave s ubwoofers
from the master or other slave subwoofers in
the chain. The R S -232 output is used from the
mas ter to a s lave s ubwoofer, or from s lave
to slave subwoofer, in a multiple Digital Drive
subwoofer configuration. This is true regardless
of whether you are feeding a dis c rete s ignal
or identic al s ignals to the s ubwoofers .
C onfiguration of a Digital Drive s ubwoofer requires the us e of a video dis play
and given the pric e, it is not unreas onable
to expec t or demand the as s is tanc e of your
dealer in s etting one (or more) up.
How Do I EQ Thee?
Let Me Count The
Ways
With sincere apologies to the great bard, I
s imply c ouldn’t pas s up the opportunity to
borrow that line––it was jus t s itting there
waiting to be used in a review and this was the
time. One of the principle features of the Digital
Drive s eries of s ubwoofers is the integrated
digital parametric equalization system. There’s
that digital word jumping out at us, and I can
tell you that these subwoofers do in fact sample at a 20-bit depth, with a 48 kHz sampling
rate. G iven that your s ubwoofer is (for all
prac tic al purpos es ) going to be bandwidth
limited to s ignals below 300 Hz, this is more
than adequate. When looking at the 20-bit
depth, it might seem a little shy when considering peaks of the Low Frequenc y E ffec ts or
Enhancement (LFE) channel at reference level
are 115 dB (that’s roughly 19 bits of resolution).
In the real world, even a very quiet room will
have a noise floor in the 25 dB range, so the
20-bit part will have sufficient dynamic range
to handle the available dynamic range.
B y default, Digital Drive is a one-third
oc tave graphic al equalization s ys tem. Finer
granularity c an be ac hieved if you us e full
manual c ontrol (c overed a little later). E ac h
band of E Q can utilize up to six decibels (6
dB ) of gain, or twelve decibels (12 dB ) of cut.
Let’s s tart with the s imples t of the three
available equalization methods, SelfEq. It really
c ouldn’t be eas ier to us e. You don’t need a
display to use it; simply put the included calibration mic rophone in the s weet s eat, hit the
R E S E T button on the remote control followed
by the keys 321, and the s ubwoofer begins
emitting a series of calibration tones to begin
equalizing its elf for the room it is plac ed in.
The goal is to get the response to within plus
or minus three decibels for the subwoofer alone.
It’s designed for simple “fire and forget” type
ins tallations . I have inc luded two graphs to
s how s ubwoofer res pons e with no c orrec tion from Digital Drive E Q or MR C in Figure
1. Figure 2 s hows the c orrec tion from
S elfE Q over the c orrec tion of S elfE Q with
MR C added on the bottom. You c an s ee the
improvements from the firs t graph for eac h
Widescreen Review • Issue 103 • December 2005
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EQUIPMENT Review
c as e s howing that the Digital Drive E Q
makes worthwhile improvements and allows
MR C to further improve res pons e.
AutoE Q goes a bit farther. To engage
AutoEQ, you take the left/right output from the
s ubwoofer and play this bac k through your
primary audio/video processor with bass management engaged. Here, the Digital Drive
system is equalizing the response for flatness
of the primary louds peakers plus the s ubwoofer, with the same target flatness of plus or
minus three decibels (3 dB ); however the goal
is to get the integration of the main louds peakers and the s ubwoofer(s ) as s eamles s
as pos s ible. When us ing AutoE Q, you c an
ac tually s ee the parametric s liders in ac tion
as it equalizes for flattes t res pons e.
Finally, you have the option for full manual
equalization. With full manual equalization, you
are in complete control of the parametric E Q,
and you c an us e the default bands as is , or
you can engage your own parametric filters to
custom equalize the subwoofer to your taste.
You c ould even us e Digital Drive to build a
hous e c urve or s tac k filters on top of one
another, if this is what you desire. And you are
also able to stack filters together. My goal was
flat response, and one of the benefits I achieved
with the c ombined tag team of Digital Drive
and Meridian R oom C orrec tion® was that
MR C was allowed to c onc entrate on frequenc ies with lower res pons e aberration for
its c orrec tion duties , res ulting in a flatter
overall in-room s ubwoofer res pons e.
Figure 3
Figure 4
EQUIPMENT Review
multi-layer res in laminate c one to minimize
flexing and resonanc es. In an unusual move,
the dual voic e c oils are des igned to operate
out of phase, in a push-pull configuration with
two magnetic gaps suspended by dual spiders.
The payback for this, according to Velodyne,
is improved driver linearity. The pus h-pull
concept is similar to the operating principle of
a planar magnetic driver. The motor is designed
for more than 1 inc h of linear motion, with a
mechanical limit of nearly 2 inches. In the case
of the DD-15, the pis ton is 12.7 inc hes in
diameter, and the magnet its elf weighs in at
over 30 pounds . In s hort, the driver is mas s ively c ons truc ted.
I think the mos t s urpris ing as pec t of this
design is that the cabinet is relatively small in
c omparis on to the s ize of the driver, with the
reviewed DD-15 c abinet having les s than
four c ubic feet in volume and no larger than
20 inc hes per s ide. The s ealed c abinet has
a tuned frequency on the order of 60 Hz, but
once powered up and with the servo engaged,
this bec omes s omething c los er to 200 Hz.
While it c ould be problematic , the inc luded
power amplifier with more than one kilowatt
of R MS power ins ures that the driver will not
be wanting for power during us e.
If it s eems that I’m giving too little attention to the amazing driver that is inc luded in
this s ubwoofer, it is n’t intentional––there’s s o
muc h tec hnology pac ked into this s ubwoofer, and I c an only c over a portion of it.
Graphical User
Interface
The Room Is Alive
With The Sound Of
Music
The complexity of the Digital Drive series of
subwoofers is tamed somewhat by the relatively well laid out G UI. While it won’t win beauty
c ontes ts , you have to keep in mind that it
shares the C PU used for servo control and as
such it is very well executed. At startup, you’re
greeted with the Velodyne s plas h s c reen.
[Figure 3] To go to the E Q S etup sc reen used
for Auto and Manual E Q the key s equenc e
12345 is us ed. At this point, the E Q S etup
S c reen is s hown with a graph of s ys tem
res pons e. [Figure 4] You c an us e the arrow
keys to toggle between Auto and Manual E Q.
From here, the NE XT button takes you to
the S ys tem S ettings s c reen where you have
full access to the parameters for each of the six
(gulp! ) pres ets . [Figure 5] E ach preset has
fields for low pass crossover frequenc y (off if
your proc es s or handles it), low pas s
c ros s over s lope (ditto), s ubs onic frequenc y
(frequenc y the s ubs onic filter kic ks in), s ubs onic s lope (c ros s over s lope for filter),
phas e (0 to 180 in 15 degree inc rements ),
polarity (+ or -), volume (1 to 99), c ontour
frequenc y (allows you to define a bump at a
partic ular frequenc y), c ontour level (s ets the
One of the things I learned during s etup
and equalization is that although I preferred
the envelopment afforded by us ing a 50 Hz
c ros s over, I was able to ac hieve a flatter frequenc y res pons e with a 70 Hz c ros s over.
All evaluations for mus ic and movies are
bas ed on this 70 Hz c ros s over. I’m of the
minds et that regardles s of whether it is
mus ic or movies , your s ubwoofer s hould be
c alibrated flat. In other words , S PL levels
(via c alibration tones ) s hould be equal to
main louds peakers with no additional gain
added. By utilizing this setting you maintain the
levels the s ound des igner or mixing engineer intended, depending on the content.
As a short demo track I pulled out an older
Telarc disc and used an electronic selection,
Don Dorsey’s “Ascent From Time Warp” (Telarc
C D-80106). This is used as a prelude to “Also
Sprach Zarathustra” with tremendous dynamic
range and frequenc y extens ion. During a
section, which closely resembles a procession,
the s ynthes ized bas s drum is delivered with
authority and c ontrol––and totally indis tinguishable from my main loudspeakers. At the
c los e of “As c ent,” a low-frequenc y rumble
52
Figure 5
level of the bump for the previous field),
and finally theater/mus ic (value 1 to 8).
Theater/mus ic s ets the amount of gain on
the s ervo, the lower the number the lower
the s ervo gain, and thus the higher the
amount of dis tortion the s ervo will allow.
S inc e I was us ing dual DD-15s in a s maller
room, I s et all pres ets to 8 (maximum s ervo
gain), as I did not need the extra S PLs
afforded by the lowered s ervo gain.
Digital Driver (And
Cabinet)
Now we finally c ome to the heart of any
subwoofer, the driver. Even if we ignore all the
other tec hnology that c omes with the Digital
Drive s ubwoofers the driver its elf is quite
impressive. All models in this series feature a
Widescreen Review • Issue 103 • December 2005
Page 3/4
s erves as the bas e for the opening to “Als o
Sprach Zarathustra,” and the DD-15 didn’t bat
an eyelash as they faithfully delivered this
material to my listening position without hesitation.
Tubulums , PVC “Xylophones ,” Wiper Air
Poles, and B ig Drums are low frequency tools
of the trade for the Blue Man G roup, and I prefer their initial releas e Audio on s urround
DVD-Audio (Virgin 7243 4 77893 8 7) as it has
minimal dynamic range compression allowing
for a more intense experience than their later
releas e. On the trac k “PVC IV,” in what is for
lac k of a better term, the “B ” s ec tion, there’s
a portion where the main melody is oc tavedoubled, and the low octave PVC is designed
to add a tuned weight and pres enc e. The
DD-15 carried this off with a remarkable ease,
regardles s of how loud I had the volume
s etting, up to and inc luding peak readings
exc eeding 100 dB S PL on my meter. On the
following trac k (“TV S ong”), downward glis s andos on bas s guitar and baritone guitar
lines des c ended pas t the c ros s over region
with no detectable timbral change, indicating
that the DD-15 did indeed do its job, delivering
a low dis tortion s ignal, whic h is what allows
the s eamles s pres entation and blend from
main louds peaker to s ubwoofer to oc c ur. At
about the 2:20 mark there is a section where
big drums are pounded merc iles s ly, and
onc e again the DD-15 delivered this with
nary a c omplaint. It’s really hard to des c ribe
low dis tortion from a s ubwoofer. You end up
lis tening a little louder than you did previous ly and you’re als o les s apt to turn the
volume down a few c lic ks on pas s ages that
you would otherwis e find yours elf frantic ally
reac hing for the volume c ontrol on.
J ames Taylor’s Hourglas s is one of my
“go to” evaluation S A-C Ds for s everal reas ons ––it’s enjoyable c ontent, with an outs tanding mix and s everal unique mix elements that I c an us e for s ys tem evaluation.
There was always a little annoyanc e with
the bas s line on “G aia,” where a c ertain run
has the opening notes a little de-emphas ized and the remainder at full volume. I
had always figured that it was played that
way by the bas s is t, but it was a very s light
frequenc y res pons e aberration that the
equalization s ys tem allowed me to defeat.
S o now J immy J ohns on’s bas s line rang
through c lear and true, with no under or
overemphas ized notes . In returning to the
vers e after c oming out of the bridge, the
drum fills and low frequenc y rumble are
mos t impres s ive, with the c ombination of
Digital Drive equalization and Meridian
R oom C orrec tion bringing improved definition and artic ulation with every s mac k of the
drum and rumble from the bas s . It’s not
often you get to dramatically improve a known
pers onal referenc e, but the additional layer
of trans parent equalization does jus t that.
Page 4/4
Several Nights At The
Movies
My wife and I are avid moviegoers , and
it is typic al for us to s ee a movie firs t run in
the loc al theatre and later purc has e the
DVD for home viewing. S ometimes we find
we enjoy the film muc h more in our home
theatre than on the large s c reen. S uc h was
the c as e with The Forgotten. There were a
few moments in this thriller where the DD-15
was given a mos t intens e workout. I’m s orry,
I didn’t have c hapter referenc es handy at
the time I made thes e notes ; I was far too
engros s ed in the film to jot down the c hapter numbers . In the firs t referenc ed s c ene (a
c ar c has e s c ene), out of the blue the protagonis ts ’ c ar is s ide s wiped––the energy of
the impac t is depic ted with a burs t of low
frequenc y energy. Here, the DD-15 is as ked
to energize the room with a loud and hars h
metal on metal impac t of two vehic les
impac ting and you aren’t let down. The
phys ic al forc e energizes the room, and I
found mys elf c ompletely s atis fied with the
performanc e of the DD-15 in my relatively
s mall room.
C ontac t c ontains s everal exc ellent
s c enes , mos t notable in C hapter 33, as E llie
travers es the s eries of wormholes with c ontent in the 20 Hz range, and the DD-15 didn’t bat an eyelas h. There was s uperb extens ion, never a s ens e of s train even at referenc e level––with no driver overhang (exc es s ive ringing or res onanc e of the driver and
c abinet). As the s uc c es s ive wormholes
bec ome more violent, the low frequenc y
energy gains more impac t and even the
s tops bec ome more s udden, and the DD-15
gives you that s ens ation of going to the
edge of the c liff and s topping jus t s hort of
going over. This is part of what draws you
into the experienc e of the movie; the reproduc tion of the s oundtrac k in a way that
engages the s onic s ens e to s us pend your
dis belief and help trans port you into the fic tional events of the movie you’re enjoying.
The DD-15 did a firs t rate job for me in
bringing me into that world.
C ons tantine has a number of s c enes
with s ignific ant low frequenc y c ontent, but it
is an early one (C hapter 2) that got my
attention. As C ons tantine exits the c ab he
drops a c igarette, and an unnatural low frequenc y ec ho ac c ompanies the initial impac t
and rebound as it hits the pavement. This
unders c ores the heavy pric e that he pays
for his c hain s moking habit (lung c anc er).
Later (C hapter 12), as the demons make a
mas s attac k on C ons tantine, the c latter and
rumble as they pas s outs ide his apartment
building is a prelude to the c oming intens e
but brief s haking as he inc inerates them at
the c los e of the c hapter.
E ric C lapton’s One More C ar, One More
R ider c ontinues to be my c urrent referenc e
c onc ert DVD in s pite of its overus e of
dynamic range c ompres s ion. For this partic ular review I us ed “B ell B ottom B lues ”
where I was mos t c onc erned with two
things , blend on the bas s guitar above and
below the c ros s over region and impac t of
the kic k drum, es pec ially in the c horus . In
both c as es , I was very impres s ed, as the
DD-15 did not dis appoint with its performanc e. Wherever Nathan E as t roamed on his
ins trument it was impos s ible to detec t,
whether the s ound emerged from the main
louds peaker or the s ubwoofer, tes timony to
the c larity of the DD-15. I c heated from time
to time by either plac ing my finger gently on
the driver, or watc hing where his fingers
were on the bas s to determine where the
s ound s hould be c oming from. C ros s overs
aren’t bric k walls ; there is s till output for
both louds peakers above and below the
c ros s over frequenc y. S teve G add’s bas s
drum als o burs t forth with as muc h c harac teris tic mus c le as pos s ible given the utilization of dynamic range c ompres s ion. I’d love
to hear this with a little les s aggres s ive us e
of c ompres s ion!
Conclusion
I’ve s pent the vas t majority of this review
dis c us s ing the tec hnic al as pec ts of the
Velodyne DD-15 s ubwoofer for good reas on. The tec hnic al ac hievements in this
produc t and the res t of the Digital Drive
lineup are s tate-of-the-art for the s ubwoofer
market. Utilizing the inc luded E qualization
s ys tem, whether you have one or multiple
s ubwoofers , allows you to blend the Digital
Drive s ubwoofer s o muc h that it bec omes
what a s ubwoofer s hould be; the low frequenc y extens ion of your exis ting s ys tem
with little dis tinguis hing s onic c harac teris tic s of its own. For thos e who want to experienc e the equalization s ys tem without purc has ing the Digital Drive s ubwoofer,
Velodyne is bringing to market the S MS -1.
B ut it is n’t a “Digital Drive In A B ox”––for
that you need the S ervo s ys tem with its very
low dis tortion c apability, plus the high
power amplifier that is des igned to provide
adequate power taking into ac c ount the
s ervo, equalization, and s ize of the c abinet
without c lipping.
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