by Bill Heck
As music lovers with nice stereo systems, many
of us are subject to periodic fits of “upgradeitis” – the desire to change
something, anything, to tweak our systems for that next level of sonic
improvement. But looking at the many upgrade options in the audio world,
especially the front end electronics, I think that we’re aiming too low.
The prices
that we might pay certainly aren’t too low: anything but that, when the
cost of fancy versions of the most basic products soar into tens of thousands
of dollars. No, I’m dissatisfied because the rewards that these products aim for, and maybe even sometimes
deliver, are so small. You don’t need to believe that amps, preamps, or DACs,
much less cables and such, “all sound the same” to suspect that the differences
among them are mostly subtle, regardless of the sometimes rapturous reports of
certain reviewers. (Speakers are a different story; I’m talking about
everything up to that point.)
Hey, I appreciate subtle improvements as much
as the next music lover. But if I’m spending big bucks upgrading audio components,
I don’t want subtle. I don’t want something that I can identify 80% of the time
in a blind test; I want something that no one could possibly miss even once. If
we spend serious money, shouldn't we get serious returns? Not on the edges, not
tiny changes, but major upgrades, differences obvious to the most casual
listener. We try to get excited about little gains, but maybe that's because
it's been so long since we've had any big gains.
Let’s take a moment to think about why the effects of changing front end
components might be subtle. The issue is that these components are mostly
pretty doggone good already: electronics with vanishingly low levels of various
distortions and digital signal sources that already provide fidelity beyond the
limits of human hearing. Moreover, despite audio folklore, human hearing is not
particularly sensitive to the kinds of differences (distortions, if you like)
that remain at this stage of the audio reproduction chain.
So, if making the musical signal even cleaner
is not where advances lie, how do we improve matters? How about changing the signal, not accidentally
but with purpose, changing it so that the sound that arrives at your ears
better reflects that sound that the performing musicians made originally? In
other words, we can modify the signal to correct for, or adapt to, the
listening room and to recover or enhance information otherwise lost in the
recording process. Yes, that’s Digital Signal Processing (DSP).
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Legacy Wavelet II
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Enter the Wavelet II. (The original Wavelet
has been replaced by the Wavelet II, which is the one that I have and am
discussing.) This product, the result of a partnership between Legacy and
Böhmer Audio, is a rare beast in the consumer stereo market, one properly
characterized as a dedicated DSP product. Sure, there are DSP capabilities
built into other products, such as AV receivers, mostly to provide room
correction (with varying degrees of success) and to synthesize spatial effects
in multi-channel systems. In the two channel world, the aim usually is room correction
only, often as an “add on”’ for preamps and such. In contrast, the Wavelet II
is primarily a DSP processor offering a unique approach to advanced room
correction, plus features aimed at what we might call “music restoration”. The Wavelet
II is one of a very few components that does not just sneak across the DSP
frontier but bounds fearlessly past it.
To clarify, the Wavelet II does provide the
functionality of a preamp and a DAC, not to mention a multi-way crossover. But
these features come along for the ride, so to speak: the functions provided by
the Wavelet II are built on an advanced processing platform to provide a
complete front end, allowing optimization of the entire package while making
things convenient for the user. (You can get an idea of how it hangs together
from this block diagram at the Böhmer website.)
In what follows, I’ll focus on the unique
features of Wavelet II. This means that, in the interest of keeping the length
of this article under control, I’ll give short shrift to some aspects; please
excuse those omissions.
Description
As with my earlier review of the Legacy
Signatures, I won't go into the specifications that you can easily read here on the Legacy website, but a quick
summary and orientation may be useful.
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Wavelet II Rear Panel |
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The Wavelet II is both figuratively and
literally a black box. I’ve not tried to open mine; you can get an idea of the
contents by reading the description on the website. The details are
proprietary, and of course with a unit like this, the real action is in the
software.
Externally, the digital and analog inputs
are more or less typical for a preamp. The output side is more interesting:
each of the eight (not a typo) output channels sports balanced and unbalanced
connections. Why eight output channels? The short answer is crossovers: I’ll
describe their use below.
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Wavelet Controls on Android Phone
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As to the controls, there are physical buttons
and a dial for basic functions on the front of the unit; I hardly ever use
them. In addition, a small remote control for basic functions is included with
the unit; I’ve never taken it out of the box. The obvious way to control the Wavelet
II is with the browser-based app. My own daily driver is a repurposed old Android
phone; my Microsoft Surface Pro works well, too, and the Legacy folks swear by
iPads.
It was the work of a few minutes to figure out
the control app. I particularly liked the clever “fine” volume control, which
makes the kind of adjustments that you are likely to make a matter of a few
taps. Another nice touch is that the apodizing filter, room correction, and
Omnio functions (described below) are turned on or off with simple checkboxes,
all of which are located on the main dashboard page – very handy for quickly
assessing the results of each function.
Functions
Let’s walk through the major functions of the Wavelet
II.
Digital-Analog Converter (DAC): Yes, the Wavelet II includes a DAC. (Do any digital products these
days not include a DAC?) Of course, you could
connect your source to your favorite DAC and connect that to one of the
Wavelet’s analog inputs. But given that the Wavelet II digitizes analog inputs
to do its DSP thing, why bother? By the way, you can switch on the fly between
linear and apodizing filters (the latter to reduce pre-ringing) but that’s one
of those subtle effect items that I’ll not spend time on here.
Preamp: The Wavelet II functions as a preamp. Not to insult the Legacy
folks, but there are oodles of preamps on the market, a lot of them are very good,
and in real world conditions, the differences among them are, well, subtle.
(The Wavelet II does provide a neat set of “Contour” sliders that are unusual
and particularly handy. You can read about them in the Wavelet II manual.) Subtle is not what I want
to write about today, so again I’ll move on to what makes the Wavelet II
unique.
Crossover: Although electronic crossovers are hardly new, finding one integrated
into a single component with all this other functionality (preamp, DAC, DSP) is
unusual, so I’ll spend a little time on it. Of course, a crossover is relevant
only if you have something to cross over, either speakers that allow bi- or
multi-amping, or perhaps regular speakers plus subwoofers.
For those readers unfamiliar with the concept
of bi- or multi-amping, here’s a brief introduction. (You other folks can skip
ahead.)
You probably know that your speakers
contain crossovers that divide up the frequencies of music and send them to the
appropriate drivers, e.g., bass frequencies to the woofers and high frequencies
to the tweeters. In “bi-amping”, the idea is to insert an active (electronic)
low-level crossover before the
amplifier instead of relying on a passive one contained in the speakers. The
active crossover thus directs bass frequencies to one amplifier and higher
frequencies to a second amp. At the speaker, the bass amp connects to inputs
(binding posts) that feed only the low frequency section of the speaker; the
high amp connects to what remains of the speaker crossover to drive the
midrange and up. To make this work, you need three things: (1) bi-amp capable
speakers, i.e., having separate inputs for bass versus higher frequencies; (2)
an active crossover in or after the preamp; and (3) a second amp.
Why mess with the complications of
bi-amping? There are several theoretical reasons, including providing more
total power to the system; moving the stress of higher power handling to just
the bass amplifier; improving crossover accuracy and consistency; keeping
large back EMF out of the amplifier handling the higher frequencies; and
isolating distortion to low frequencies. (Details about the benefits of
bi-amping can be found on the Web.)
So with the Wavelet II, the crossover
characteristics specific to your speakers are programmed in before the unit it
is shipped to you. If you are using Legacy speakers, the Legacy crew already
knows how to program the unit for optimal performance in your system. If you
are using other speakers – and indeed you can use the Wavelet II with non-Legacy
speakers – you would need to supply information, such as crossover frequencies,
so that they can program the unit properly.
For example, to work with my Legacy Signature speakers, two pairs of channels
are set for bi-amping (L-R for highs and L-R for lows); another pair is set as
full range L-R in case I didn’t want to bi-amp; and the final pair is reserved
for subwoofers(s). Higher-end Legacy speakers, such as the Valor, would use all
four pairs of channels for the different sections of the speakers, i.e.,
multiamping. If I later trade in my Signatures in favor of some other speakers,
I can return the Wavelet II to Legacy for reprogramming as needed.
By the way, for those deep in the weeds on
crossovers, note that Wavelet II digital crossover is itself quite sophisticated,
supporting multiple parameters (slopes, delays, filters, etc.) per channel.
Room
Correction: Certainly, there are other room correction
systems (rather a misnomer, as it’s more like “room adaptation”), whether from
makers of receivers or independent ones such as Dirac, but Legacy is the only
vendor I know of offering the Böhmer system.
The Böhmer approach differs from most,
perhaps all, other room correction systems in that it is primarily based on
time rather than frequency, compensating for room effects within a 50
millisecond (ms) window. That long window – in audio processing terms, 50 ms is
a long time – allows the Böhmer analysis to “look at” and deal with the results
of multiple room reflections.
To cover the process in any detail would
take us far afield; I’ll stick to reporting the results below, and suggest that
you look at the detailed Böhmer website for more information.
Creating the correction algorithm for any
given audio system and room is computationally intensive, so during setup you
run a measurement process and the data thus collected is submitted via the internet to a high-powered
server. Within a few minutes, the calculated correction algorithms are sent
back to the Wavelet II. Although execution of the algorithms while playing
music requires less processing power than their initial construction, the load
is hardly trivial, which is why the Wavelet II contains a serious numerical
processor (an Analog Devices chip with associated hardware support components).
Other
DSP: Room correction is the most obvious form of DSP,
but the Wavelet II offers another, or rather two others: “Omnio” and “Omnio+”.
These are Legacy’s names for algorithms that “improve channel separation and
restore the directional vector relationship to depth and position cues”. As the
names imply, Omnio, which has been around for a few years, was the first
iteration; “Omnio+” is a matter of months old, having been added in the
recently released version 2.0 of the Wavelet II firmware.
Note that existing Wavelet II’s can be
upgraded with this latest firmware; in other words, the functionality of the Wavelet
II can improve after you buy it. We’re used to that with smartphones (and electric vehicles); how nice to see it in an audio product.
So what’s the result? What does advanced
DSP do for the sound? Does it improve our listening experience? Look for part 2
of this article shortly.