Why is the frequency response in the DS-4000 lower than other models?

Question: Other Olympus digital voice recorders have a wider frequency response than the DS-4000. Why is the frequency response in the DS-4000 lower? The DS-4000 is designed as an Olympus Professional Dictation Device, whose primary function is to record dictation files for transcription. Dictation recordings do not require a wide frequency response because the audio…