Basic EQ1 functions
The basic features are common to all four models, namely the seven identical parametric bands, i.e. all seven bands cover the entire audio frequency range. Each band has Boost/Cut, Frequency and Q/Slope knobs and operates in any of the following modes: High shelving, low shelving, peaking, high cut, low cut, bypass.
There are seven times three knobs in order to have “one knob per parameter” operation. The knobs are touch sensitive to switch the LCD to display the parameters of the touched band. The LCD shows the overall frequency response, the detailed parameter values and various status information.
Snapshots, MIDI, metering
Other basic features are an A/B compare memory, a 128 position snapshot bank with two additional banks for back-up (can also be dumped/recovered via MIDI), a peak meter with over indicators, MIDI control for each parameter, an overall bypass switch and an overall gain control, a channel ganging switch.
Signal processing, connectivity
The internal processing is done at 88.2 or 96 kHz in a 40 Bit floating-point format. A very low noise filter architecture optimized for audio is used. The digital input/output are in AES/EBU format on XLR connectors. The AES/EBU output can be POW-R dithered to 16, 20 or 24 Bits.
The EQ1 can be switched to M/S mode which is especially useful for the dynamic model of the EQ1. Also see the article: “Stereo Shuffling: New Approach – Old Technique” by Michael Gerzon. Other specialties are variable slope shelving filters and very high Q (up to 650) peaking filters for notching out offending frequencies.
The EQ1 can be inserted into any digital audio chain with sampling rates between 44.1 and 96 kHz. The synchronization is done via the AES/EBU input signal.
The EQ1-MK2 is the basic model with minimum phase type filters.
EQ1-LP, the EQ1-MK2 with linear phase response
The EQ1-LP has the same parameter set and features as the EQ1-MK2. In addition it can be switched between minimum and linear phase behavior. Linear phase means that the delay introduced by processing is constant across the whole spectrum, unconstrained by the EQ settings. The sound, or character, of an equalizer has been said to be influenced by phase response as for example John Watkinson mentioned in Studio Sound magazine 9/97: “… much of the audible difference between EQs comes down to the phase response.” The EQ1-LP is therefore the ideal tool for corrective amplitude adjustment, without the unwanted phase distortion added by standard equalizers.
EQ1-DYN, the EQ1-MK2 with four dynamic bands
The EQ1-DYN features four freely adjustable dynamic bands, and additionally three linear bands per channel. Setting up the dynamic bands is as easy as setting a linear band. There is just one additional parameter to be adjusted by the user, the threshold control. This makes multi-band dynamic control as easy and as versatile as adjusting a parametric equalizer. The dynamic EQ can be used as a de-esser or to give the bass an extra punch etc..
Bands 1, 2, 5 and 6 are the dynamic bands (each individually switchable to linear) and bands 3, 4 and 7 are ordinary linear bands. A dynamic band operates similar to a compressor, with two additional features:
1) The band is sensitive to signal level in its frequency range only. So when applying dynamic bass EQ, only the bass-band of the program affects the dynamic behavior. There is no cross-modulation from other bands.
2) The gain is only applied to certain frequencies, and not across the whole audio band.
3) Other modes (low-cut, high-cut, low-shelving, high-shelving) are linear (no automatic boost/cut adjustment), and behave exactly the same as in the EQ1-MK2.
The reason for choosing exactly bands 1, 2, 5 and 6 is the following: As the name implies, a dynamic band is sensitive to the level of the input signal. Sometimes it is desirable to first add some EQ, and afterwards dynamically add some more. Or vice versa, first do some dynamic corrections and afterwards add overall EQ, including in the corrected band. Because the EQ bands are connected in series, this is only possible if there are linear bands before and after the dynamic bands.
EQ1-DYN-LP, Dynamic and Linear Phase EQ in a single unit
The EQ1-DYN-LP contains both the Dynamic and the Linear Phase EQ programs. After power-up of the unit, the user can chose between Dynamic (DYN) and Linear Phase (LP) modes. The workspace storage, the snapshots and the snapshot backups are fully independent between the DYN and LP parts of the unit. This means that all setup data are retained in any case.