Control elements
Setting the starting frequency for the shelving filter to adapt the frequency range to the hearing sensation.
No comb-filtering effect as with graphic EQs.
Measurement 1:
Bass = Tight
Bass-LC filter = Off
Process Level = Max
Hi-Mid Freq. =
1 / 1,5 / 2,5 / 3 / 5 / 8 / 14 / 22 kHz
The Hi-Mid Freq. control is used to set the starting frequency of a broad-band shelving filter. In line with the setting of Process Level control, all frequencies above this value right through to the end of the audio range are processed.
The control range of the Hi-Mid Freq. control is between 1kHz (extreme right) and 20 kHz (extreme left). In practice, common settings vary between 3.5 kHz and 8 kHz.
As the human ear perceives the range between 1kHz and 3 kHz particularly clearly, at all volumes between 0 and 120 phon it makes sense to adapt this frequency range. You might feel inclined to say “Yes, but I do that with my graphic EQ as well”. The main difference is that the graphic EQ really reduces the effective loudness of the frequency, i.e. cuts out the appropriate frequen- cies, thus changing the spectral content of the original signal. The Tube Vitalizer, however, relies on a more subtle method of ampli- tude-depending phase shifting. This does not involve altering the spectral composition of the signal but it does maintain the subjective impression of loudness. Moreover, graphic equalizers produce comb-filter effects because of the interaction between adjacent filters, when broad-band frequencies are raised. The Hi- Mid Freq. filter can raise the broad-band spectrum with a very linear frequency response, without colouring the signal.
Above the Hi-Mid Freq. value set, the Tube Vitalizer filters create a linear increase, i.e. one that is adapted to the human ear. This compensates any inability of our hearing as regards perceiving frequencies ranging between 5 kHz and 10 kHz. The Hi-Mid Freq. filter work with a wide bandwidth and always sounds musical, never ‘bell-like’. Gradually go down from 20 kHz (extreme left) to lower frequencies. The further down you go, the brighter the sound image becomes, as an increasing number of frequencies are included in the process.
The Hi-Mid Freq. control can also be used to tone down excessi- vely sharp-sounding material, by setting frequencies of 10 kHz or higher, and setting the Process Level control on Max. Seeing as the Process Level control is also responsible for deleting domi- nant mid frequencies, all frequencies are gradually reduced down to the application frequency, in conjunction with high starting frequencies of the Hi-Mid Freq. control.
