Thanks to the new level of TDA time selectivity it has now possible to evaluate loudspeaker properties in details and create a very accurate equalizer. In comparison to results of SPFR equalization, it is giving us more accurate result for „on axes” region for near field applications – studio monitors, stage monitors and more accurate result for 30 ... 50 Hz band where the time windowing of SPFR measurement reduces frequency resolution.

Examples: TDA graphs and AFR curves after and before equalization applied.


The prototype version of TDA EQ software is ready for evaluation. The software is creating FIR equalizer files for usage in APL1 unit or APL EP1 VST equalizer plugin.

Please send your inquiry for evaluation to apl (at) The article for Pro Sound Web, describing APL equalization solutions, is being prepared.