Normal
Re: FIR filtersIn the screenshots at the link (above) that I posted, there are two sequences of images. The 2nd sequence, without coherence, starts with a (somewhat poor) measurement of a typically 12" 2-way with a HF driver lagging the LF due to the horn depth. The loudspeaker's passive crossover has been designed to maintain a roughly flat magnitude but the LF leading the HF can clearly be seen in the time domain representation of the measurement on the "Import" tab. The "Export" tab shows the convolved result of the imported measurement with the FIR filter - which in this case is flattening the phase. Note how the impulse is improved/sharpened - I.e. the LF and HF are aligned (but at the expense of the FIR filter delay). This example shows how manipulating phase is manipulating time. The two are directly related.In the case of time domain horn correction, the LTI behaviour of the horn is a filter and can be expressed as time domain IR or a mag/phase representation. Manipulating the mag & phase of this "filter" affects the time domain behaviour and vice versa. As an aside, I'm curious to know how well David's horn correction filter method holds for different levels, given non-linear/adiabatic air behaviour in the horn at high levels.
Re: FIR filters
In the screenshots at the link (above) that I posted, there are two sequences of images. The 2nd sequence, without coherence, starts with a (somewhat poor) measurement of a typically 12" 2-way with a HF driver lagging the LF due to the horn depth. The loudspeaker's passive crossover has been designed to maintain a roughly flat magnitude but the LF leading the HF can clearly be seen in the time domain representation of the measurement on the "Import" tab. The "Export" tab shows the convolved result of the imported measurement with the FIR filter - which in this case is flattening the phase. Note how the impulse is improved/sharpened - I.e. the LF and HF are aligned (but at the expense of the FIR filter delay). This example shows how manipulating phase is manipulating time. The two are directly related.
In the case of time domain horn correction, the LTI behaviour of the horn is a filter and can be expressed as time domain IR or a mag/phase representation. Manipulating the mag & phase of this "filter" affects the time domain behaviour and vice versa. As an aside, I'm curious to know how well David's horn correction filter method holds for different levels, given non-linear/adiabatic air behaviour in the horn at high levels.
