machead
100+ Head-Fier
- Joined
- Aug 24, 2004
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Quote:
You cannot equate crossfeed with crosstalk. To be effective, crossfeed must be both delayed and equalized to approximate the HRTF. Crosstalk achieves neither of these aims. It is true that the apparent width of a stereo image can be reduced by simply mixing a small amount of the left channel with the right and vice versa; but this works only if the signals are in phase. The crosstalk created by resistance in a common ground circuit, however, is out of phase. This distorts the stereo image in much the same way as reversing the phase of one channel.
If you look at the graphs published in journals such as Stereophile, the measured crosstalk is attributable almost entirely to capacitive coupling between the channels. This is indicated by inter-channel coupling that rises at a rate of 6 dB per octave. The common mode crosstalk is not frequency dependent and effectively sets the minimum crosstalk level at low frequencies where capacitive coupling is vanishingly small. While dual-mono contruction greatly reduces both forms of crosstalk, a well-designed stereo amplifier will have sufficiently low ground resistances that "common mode" crosstalk will be reduced to negligible levels. This is especially true if so-called "star grounding" techniques have been employed.
Individual listeners vary in their sensitivity to extreme channel separation; indeed, one may postulate that it is possible to train oneself to accommodate what is, after all, the biggest difference between headphone and loudspeaker renditions. I personally am not troubled by the "two blobs" phenomenon except for certain recordings that deliberately set out to convey that sensation. In fact, one of the most important criteria by which I assess the worth of a headphone amplifier is its ability to portray a convincing soundstage. Having found amplifiers that excel in this area, I'm happy to do the vast majority of my listening without the benefit of crossfeed. I believe that it's the job of those responsible for microphone placement and final mixdown to ensure that a sufficient level of channel blend is present to facilitate the illusion of a broad and deep soundstage.
| Originally Posted by Sovkiller Now about the crosstalk, it is a common misconception about headphone listening, that you need a completelly and isolated two channel system, very extreme separation of channels in heapdhone listening is not a very good idea, you will get the unfamous blob in the head, that eveybody are trying to avoid, and the main reason why crosfeed exists. Ideally you need some flow of information from one channel to the other to create the right natural image in front of you, IMO it is waste of time to try to get the completelly independent two channel headphone amp, you need to mix the channels at some point in some way, similar to what the crosstalk does in some way, to create a natural feel and a natural soundstage, unless you are hearing all the time binaural recordings. ... Also the unbalanced operation unless completelly dual mono, has the ground already mixed inside the amp, so running it along the cable that way, will not harm in any way the signal, it is already mixed, the crosstalk came already from the amp, and indeed it is measured most of the times on the amp, and not from the cables. |
You cannot equate crossfeed with crosstalk. To be effective, crossfeed must be both delayed and equalized to approximate the HRTF. Crosstalk achieves neither of these aims. It is true that the apparent width of a stereo image can be reduced by simply mixing a small amount of the left channel with the right and vice versa; but this works only if the signals are in phase. The crosstalk created by resistance in a common ground circuit, however, is out of phase. This distorts the stereo image in much the same way as reversing the phase of one channel.
If you look at the graphs published in journals such as Stereophile, the measured crosstalk is attributable almost entirely to capacitive coupling between the channels. This is indicated by inter-channel coupling that rises at a rate of 6 dB per octave. The common mode crosstalk is not frequency dependent and effectively sets the minimum crosstalk level at low frequencies where capacitive coupling is vanishingly small. While dual-mono contruction greatly reduces both forms of crosstalk, a well-designed stereo amplifier will have sufficiently low ground resistances that "common mode" crosstalk will be reduced to negligible levels. This is especially true if so-called "star grounding" techniques have been employed.
Individual listeners vary in their sensitivity to extreme channel separation; indeed, one may postulate that it is possible to train oneself to accommodate what is, after all, the biggest difference between headphone and loudspeaker renditions. I personally am not troubled by the "two blobs" phenomenon except for certain recordings that deliberately set out to convey that sensation. In fact, one of the most important criteria by which I assess the worth of a headphone amplifier is its ability to portray a convincing soundstage. Having found amplifiers that excel in this area, I'm happy to do the vast majority of my listening without the benefit of crossfeed. I believe that it's the job of those responsible for microphone placement and final mixdown to ensure that a sufficient level of channel blend is present to facilitate the illusion of a broad and deep soundstage.
