A scalable adaptive audio encoding system, comprising: an envelope analyzer for outputting spectral envelopes on the basis of a time frame of a frequency-domain representation of a first audio signal and at least one further audio signal (E2, E3); a multichannel encoder including: a rate allocation component for determining: first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; and second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; and a quantization component configured to retrieve the quantizers indicated by the rate allocation component and to quantize the first audio signal and the at least one further audio signal using the quantizers thus retrieved, and to output signal data; and a multiplexer for outputting a bitstream comprising the spectral envelopes, the signal data and the rate allocation data, wherein the rate allocation component is configured with a first rate allocation rule, by which the first rate allocation data, the spectral envelope of the first audio signal (EnvE1) and a reference level (EnvE1Max) derived from the spectral envelope of the first audio signal using a predefined non-zero functional determine the quantizers for the first audio signal, and with a second rate allocation rule, by which the second rate allocation data, the spectral envelope of the at least one further audio signal (EnvE2, EnvE3) and said reference level EnvE1Max) derived from the first audio signal determine the quantizers for the at least one further audio signal. an envelope analyzer for outputting spectral envelopes on the basis of a time frame of a frequency-domain representation of a first audio signal and at least one further audio signal (E2, E3); a multichannel encoder including: a rate allocation component for determining: first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; and second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; and a quantization component configured to retrieve the quantizers indicated by the rate allocation component and to quantize the first audio signal and the at least one further audio signal using the quantizers thus retrieved, and to output signal data; and a rate allocation component for determining: first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; and second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; and first rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the first audio signal; and second rate allocation data indicating, in a collection of predefined quantizers, quantizers for respective frequency bands of the at least one further audio signal; and a quantization component configured to retrieve the quantizers indicated by the rate allocation component and to quantize the first audio signal and the at least one further audio signal using the quantizers thus retrieved, and to output signal data; and a multiplexer for outputting a bitstream comprising the spectral envelopes, the signal data and the rate allocation data, wherein the rate allocation component is configured with a first rate allocation rule, by which the first rate allocation data, the spectral envelope of the first audio signal (EnvE1) and a reference level (EnvE1Max) derived from the spectral envelope of the first audio signal using a predefined non-zero functional determine the quantizers for the first audio signal, and with a second rate allocation rule, by which the second rate allocation data, the spectral envelope of the at least one further audio signal (EnvE2, EnvE3) and said reference level EnvE1Max) derived from the first audio signal determine the quantizers for the at least one further audio signal.