|The U786 is a Stereo Mastering Compressor with a very special feature set. In addition to the operation as 'normal' stereo compressor, it can be used as Bass Compressor for special, separate dynamics treatment of the low frequency range or as part of a Multiband Compressor combination of several U786 modules. Integrated matrix sections and additional controls allow also operation as M/S Compressor.
In addition to the special features for the different operations modes, the device has an extensive assortment of controls for massive loudness gain, colorisation, and the compensation of negative side effects of strong compression.
The U786 Bass Compressor is the result of many discussions with mastering customers about the advantages and disadvantages of multiband compression.
The bass compressor is the solution for a common problem when using compression of stereo mixes. Usually a setting that is appropriate for the mid and high range is not the best setting for the low frequency range and vice versa. If the setting of a wide band compressor is optimized for the mid and high range, the bass range could use a tighter compression to maintain a stable bass fundament. Such a setting would result in a compression that is too hard for the mid and high range. In addition, the tight LF compression would propably result in a setting that modulates the mid range with each kick of the kick drum and/or each tone of the bass guitar. Bringing down these effects will result in settings with low gain reduction and poor loudness gain.
Using a second compressor with a side chain equalizer is possible to avoid these disadvantages and add stronger compression in the bass range. However, a second compressor with the side chain equalizer also treats the mid high range, and only the EQ setting results in a regulation is focussed on the bass range. The modulation is lower with appropriate settings but still exisiting. This is more a compromise than a real solution. The second way out is a multiband compressor. However, this way is also not free from problems. The split frequencies of the different bands must match the spectrum of the mix or different regulation of the bands will cause strange effects by treating the harmonics of an instrument different from the respective base frequencies. In addition, all the time the multiband compressor starts working, it also changes the levels in the frequency bands differently, which results in a dynamically controlled change of the frequency response - just like a 3 or 4 band EQ that changes boost or cut with random values. The multiband compressor needs to have a full set of controls for each band and variable but phase corrected split frequencies with appropriate ranges. The setup process is complex and requires a lot of time; a solution, but an extensive one in every respect.
The bass compressor offers a different solution. It is not a multiband compressor, even though several U786 modules can be combined to multiband system. It can treat only the bass range, has a full set of controls for high flexibility and an assortment of additional functions to cover the common problems of a strong compression. Since the mid/high band is available on the insert, another compressor can be used to process to the mid high band differently. Alternatively a wide band compressor can be used pre the bass compressor for the general compression while the bass compression adds only some pressure in the low frequency range.
The Bass & M/S Compressor U786 is an uncommon tool for dynamics treatment that be used in many different ways.
Wide Band Compressor
As long as the SPLIT MODE switch is not pressed, the U786 is a 'normal' stereo compressor with an assortment of special features for the compensation of negative side effects of dynamics treatment. The insert section is a normal side chain insert in this mode.
The SPLIT MODE switch inserts a phase corrected split filter with a sweep range from 60 Hz to 300 Hz pre compressor and M/S matrix section. The two outputs of the filter are treated differently. If DYN TO HI is not pressed, the low frequency band feeds the compressor section and the compressed signal feeds the output mixer. The mid/hi band passes the compressor but is routed thru the insert section. The insert return feeds the output adder. Only the low band is compressed, while mid and high are mixed to the output.
If DYN TO HI is pressed, both bands are reversed. Now the mid/hi band is treated by the compressor while the low band is available on the insert. The sweep range from 60 Hz to 300 Hz can be changed to the needs of the customer.
The design of the U786 makes possible to combine any number of U786 modules to a multiband compressor. The band that is not processed by the compressor passes the insert section before it is added to the compressed band. When using the device as bass compressor, the mid/high range is available at the insert.
The insert can be used to include another U786 that has a different, custom frequency control range. Since the 2nd module also routs the unprocessed band, which is no everthing above the split frequency of the second compressor, to its insert, a third module can be installed there to process another frequency range. Actually, the number of modules - and therefore also the number of bands of a multiband combination - is not really limited. Any U786 can be upgraded to a multiband compressor at any time; however, already the first device is useful due to the universality and flexibility of this device.
- go to M/S Compressor
- go to additional Compressor Features:
dynamic Release Time Modulation