I remember reading somewhere, though I cant find it now, about the importance of having a balanced FR, by this meaning if one was missing some of the top octaves that one should have corresponding roll off in the bottom octaves. If I remember correctly there was even a formula quoted to work out how much bass one shouldnt be hearing..
Anyone heard of this?
Bevan
Actually, that was so popular a notion in British audiophile circles around 1975 that Hi Fi News and Record Review published a clever circuit for a box that enabled you, with a single knob, to vary the width of the "window" to be appropriate to the material or the speakers you were listening to, all the while varying HF and LF roll off in such a way as to adhere to this wonderful formula from Bell Labs:
Bell Labs ascertained that, to sound natural, the product of the HF and LF -3 dB points should be 400,000. According to this theory 20-20,000Hz sounds balanced, as does 40-10,000, 80-5,000, and so on. This also, apparently, why a telephone is capable of sounding natural in terms of preserving tonality of the source even though the nominal frequency response of the system is only 200-2,000Hz. The product is still 400,000!
This flies right in the face of mini monitor design where subs are not used and HF extension goes flat out to 20k or so. It suggests that if you cannot make it to 20Hz flat you shouldn't be hearing 20k flat, either. Come to think of it, maybe that's why speakers are so often listened to well off their frontal axes (e.g., with the speakers facing straight ahead) - the resulting HF roll off matches the LF roll off!
