On Thu, Dec 15, 2011 at 07:19:40PM -0000, Richard Lee wrote: > Fig 3.3 shows them in the form that Ambdec uses; matched gain at LF. > > So 'order gain' at LF is 1.0 for both. > > At HF, 'order gain' is > > 3.7dB for W > and > -2.1dB for X & Y
So what this amounts to is that for normal B-format the difference between the HF gains for resp. W and X,Y is 3 dB, and for UHJ it should be 5.8 dB. The actual shelf gains (the difference between LF and HF gain for any component) don't tell the real story. Changing the LF or HF gain for all components by the same amount doesn't modify the decoding, it just results in some EQ. The Ambdec presets actually normalise for pressure at LF and for energy at HF. That means that the shapes of the equivalent shelf filters depend on the number of speakers. For example, the square decoder has order gains +3, 0 at HF, while the octagon first order one has +6, +3. In both cases the difference between W and X,Y is 3 dB, this makes the decoder max rE. The balance between the HF and LF parts (that is, the actual slopes of the 'shelf filters') can be changed at run time using the LF/HF balance control. Ambdec doesn't use shelf filters, it uses crossover filters and two independent matrices. So all the above is assuming that the two matrices are the same. They usually are for regular layouts, but not in the case of the 5.1 one. This complicates matters. Looking at the HF order gains for the 5.1 decoder it seems the ratio is close to 5.8 dB, but this doesn't mean anything as the matrices are quite different. Ciao, -- FA Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl. _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
