• 01-01-2004, 12:15 PM
    Something about 3Khz 'DIP' in old AR DIY crossovers...

    Just went through these lines on Linkwitz website and found them quite interesting and decided to share it with you guys. Maybe this is a good explanation to that 3Khz dip in the 'old' design and why some people still prefer it.

    "H - Psycho-acoustic 3 kHz dip

    Our perception of loudness is slightly different for sounds arriving frontally versus sounds arriving from random directions at our ears. The difference between equal-loudness-level contours in frontal free-fields and diffuse sound fields is documented, for example, in ISO Recommendation 454 and in E. Zwicker, H. Fastl, Psycho-acoustics, p. 205.
    Diffuse field equalization of dummy-head recordings is discussed in J. Blauert, Spatial Hearing, pp. 363, and headphone diffuse field equalization by G. Theile in JAES, Vol. 34, No. 12.
    Reference to a slight dip in the 1 to 3 kHz region for loudspeaker equalization is made in H. D. Harwood (BBC Research Department), Some factors in loudspeaker quality, Wireless World, May 1976, p.48.

    Around 3 kHz our hearing is less sensitive to diffuse fields. Recording microphones, though, are usually flat in frequency response even under diffuse field conditions. When such recordings are played back over loudspeakers, there is more energy in the 3 kHz region than we would have perceived if present at the recording venue and a degree of unnaturalness is introduced.
    This applies primarily to recordings of large orchestral pieces in concert halls where the microphones are much closer to the instruments than any listener. At most listening positions in the hall the sound field has strong diffuse components.
    I use a dip of 4 dB (x1.gif, 2760NF) to equalize for this. The circuit consists of R, C and L in series, forming a frequency dependent ladder attenuator in conjunction with the 5.11k ohm source resistor. You may choose to make the notch filter selectable with a switch for different types of recordings.

    I have found through my own head-related recordings of symphonic music that the dip adds greater realism, especially to large chorus and to soprano voice and allows for higher playback levels."

    here is the reference link: http://www.linkwitzlab.com/models.htm