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<blockquote data-quote="ciaonzo" data-source="post: 8071232" data-attributes="member: 607015"><p>As I said, the key is group delay. Someday you will sit in my vehicle and have a reference for what a low group delay vented alignment sounds like. Hopefully this year, lol. Basically sounds like sealed with more balls. Here's some copypasta on group delay.</p><p></p><p>"Group delay is a measure of how sharply the phase of a signal</p><p></p><p>changes from one frequency to the next. If the group delay</p><p></p><p>remains low at all frequencies, the bass will be taut and well</p><p></p><p>controlled. But if the group delay at some frequencies is much</p><p></p><p>higher than 20 ms, the woofer is likely to exhibit poor transient</p><p></p><p>response, thickening sounds at those frequences while robbing the</p><p></p><p>woofer of clarity and impact."</p><p></p><p>Delay audibility mechanisms (this says nothing about the thresholds, just the mechanisms):</p><p></p><p>Delay skews perception of second harmonic distortion,</p><p></p><p>but amazingly, in such a way that the skew is level dependent. This</p><p></p><p>is an artifact of gross delay distortion that can easily be shown</p><p></p><p>from a steep filter. It may explain the harshness many people</p><p></p><p>talked about with old steep anti-aliasing filters.</p><p></p><p>Another point is that the non linearities in the ear itself can lead to</p><p></p><p>changes in the transfer from outer to inner ear that are phase, not</p><p></p><p>power, dependent. Some monaural phase effects can be explained</p><p></p><p>by the concept of the inner spectrum, the spectrum available to</p><p></p><p>the inner ear. This is different than the spectrum at the outer ear</p><p></p><p>due to non linearities in the middle ear and inner ear. Identical</p><p></p><p>external power spectra can lead to substantially different inner</p><p></p><p>spectra for different phase angles.</p><p></p><p>A third aspect is that reversals of phase for some</p><p></p><p>harmonics can create "beats" that change masking thresholds quite</p><p></p><p>dramatically, often up to 30 dB. There are some major implications</p><p></p><p>here for keeping tweeters and woofers in phase, keeping xover phase</p><p></p><p>on a symmetrical basis and NOT just judging success on a power</p><p></p><p>basis. Finally, I found a reference describing the threshold for</p><p></p><p>localization movement based upon group delay. I have applied it as a</p><p></p><p>group delay criteria for maintaining sharp images in multi way</p><p></p><p>speaker systems.</p><p></p><p>There's also a good paper that looked at the impact of group delay across</p><p></p><p>the spectrum, starting with 30 Hz fundamentals. The group delay</p><p></p><p>across the board impacted the ability to pick out mid-range detail.</p></blockquote><p></p>
[QUOTE="ciaonzo, post: 8071232, member: 607015"] As I said, the key is group delay. Someday you will sit in my vehicle and have a reference for what a low group delay vented alignment sounds like. Hopefully this year, lol. Basically sounds like sealed with more balls. Here's some copypasta on group delay. "Group delay is a measure of how sharply the phase of a signal changes from one frequency to the next. If the group delay remains low at all frequencies, the bass will be taut and well controlled. But if the group delay at some frequencies is much higher than 20 ms, the woofer is likely to exhibit poor transient response, thickening sounds at those frequences while robbing the woofer of clarity and impact." Delay audibility mechanisms (this says nothing about the thresholds, just the mechanisms): Delay skews perception of second harmonic distortion, but amazingly, in such a way that the skew is level dependent. This is an artifact of gross delay distortion that can easily be shown from a steep filter. It may explain the harshness many people talked about with old steep anti-aliasing filters. Another point is that the non linearities in the ear itself can lead to changes in the transfer from outer to inner ear that are phase, not power, dependent. Some monaural phase effects can be explained by the concept of the inner spectrum, the spectrum available to the inner ear. This is different than the spectrum at the outer ear due to non linearities in the middle ear and inner ear. Identical external power spectra can lead to substantially different inner spectra for different phase angles. A third aspect is that reversals of phase for some harmonics can create "beats" that change masking thresholds quite dramatically, often up to 30 dB. There are some major implications here for keeping tweeters and woofers in phase, keeping xover phase on a symmetrical basis and NOT just judging success on a power basis. Finally, I found a reference describing the threshold for localization movement based upon group delay. I have applied it as a group delay criteria for maintaining sharp images in multi way speaker systems. There's also a good paper that looked at the impact of group delay across the spectrum, starting with 30 Hz fundamentals. The group delay across the board impacted the ability to pick out mid-range detail. [/QUOTE]
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