The subject of how to EQ the higher frequencies of a speaker would need a long article unto itself, so I shall have to confine myself to a few summary remarks. First of all, since the ear/ brain is editing for direct arrival, one should eschew narrow-band ups and downs to get rid of the small room effects that arise from reflected sound. In essence, one should correct the speaker (in the higher frequencies) anechoically. Few of us have an anechoic chamber handy. But you can get quite accurate results by measuring near the speaker. As noted above, you can use the full-range sweep measurement of the DualCore for this.
Second, you should not correct things that are highly unstable with respect to variation of position. Spatially stable effects need corrections; unstable ones do not. And other things being equal, extremely narrow-band corrections are seldom needed with good speakers.
Again, experimenting is recommended, and again you have the opportunity to save “profiles” for quick comparisons.
The DualCore really opens up a world of possibilities. It can be up and running and correcting bass in just a few minutes. But you can also explore more of the possibilities. And even once you have made your system sound what to your ears is ideal, the Quicktone feature can be used in addition—on the fly, as it were—as a set of tone controls of a very effective sort. And none of this does any signal damage! Properly done digital EQ is penalty free, and properly done it is here.
To explore absolutely as far as one can go, it is a help to have the outboard viewing program, where one can pull the small screen pictures the unit itself shows you up on a computer screen. This will be available as a downloadable program from DSPeaker shortly, though at present it does not seem to be on the Web site.
Limitations Relative to Subwoofers
The DualCore is pre-eminently a device to correct a stereo system as a unit. While in principle one can drive a system with two main speakers and powered subwoofers using the two analog outputs, in practice one cannot set delays and high- and low-pass filters separately, as one would want to do for subwoofering in its ideal form. The DualCore as it stands will EQ a subwoofered system to be flat. But to use it as a crossover and time-delay device, it appears that one would need two of the units, as things now stand.
And even then, there would be the difficulty of changing the volumes of the two channels in a unified way. I understand from Tim Ryan, the USA distributor for DSPeaker, that plans are afoot for a double unit with a master/slave connection to gang the volume controls and thus offer full subwoofer flexibility. For the moment, be aware that while the DualCore will do an admirable job of flattening your overall subwoofered system, it will not really enable you to do the kind of high-pass and lowpass filtering with time delays that most subwoofer users would like to see in a DSP unit—not yet anyway! But stay tuned.
This review has so far been about theory and measurement and history. But of course the real reason for using a device like the DualCore is musical. High-end audio has long been obsessed with mids and lower treble, with “female vocals” being the standard test material. And of course the midrange is the heart of music. But bass counts and lower midrange counts, too. For too long, audio people have put up with the lower frequencies being wrong, and they have adjusted to this wrongness. The first time one hears the bass reproduced correctly is a revelation. Of course you might have had this revelation long ago, but in case you have not, let me describe what happens.
There is a simultaneous gain in both strength and precision of the lower midrange, upper bass, and on down into the depths. Organ music, as in, say, the Reference Recordings Rutter Requiem organ part, becomes a well-defined, pitch-accurate, and yet still powerful part of the music. Plucked string bass notes in, say, The Paul Desmond Quartet Live (Horizon/A&M) or Opus 3’s Tiden Bar Gaar begin to sound really like a string bass, with the combination of definition and impact of live bass pizzicatos.
Orchestral music gets its real foundational sound, impact, and definition combined. (Try my old stand-by, Dvorák’s New World on Delos). The change is profound in all music where bass really counts, even in something that does not seem bass-oriented, such as the string orchestra version of Bach’s Goldberg Variations, arrangement by Sitkovetsky.
The change here is so pervasive—so nearly universally does improving the bass radically improve music and increase both its realism and its musicality—that citing specific examples seem almost a diversion. Everything is better if there is bass in it at all.