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Thread: Upfront bass illusion - Follow up

  1. #21
    Member Candisa's Avatar
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    Don't worry, the Saab will be tuned to match your taste (which is approximately the same as mine, apart from the lowest half octave).
    Afterwards, I can always make an extra setting with a little more ultra-low sub-bass for when I'm on the road without you next to me

    Isabelle

  2. #22
    I was planning on a dual setting anyway with the 2nd one being with the subs tuned in a little more for when I/we want to go b00m
    Thinking outside the box is how knowledge is broadened

    Unfortunately mine doesn't look as sweet as the one in my avatar:cry:
    SAAB 900=> CLARION HX-D2, CLARION APA4300HX(x3), DAYTON IB385-8(x2), Hi-Vi M8a, TANGBAND W4-1337, DAYTON ND20fb
    Future SAAB 99=> McIntosh HU + amps and some drivers

  3. #23
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    I haven't read the whole thread yet. [I will, I promise!]

    My suggestion for pulling the bass "up front" can be boiled down to two words:

    ADD DISTORTION.

    Why do panels evoke bass directional cues when the actual sound being emitted from the panel is often hundreds of Hz? Because these high frequency sounds are correlated with the bass, that's why. This is the same reason why you can get a snare to hit you right in the chest ... your midrange speakers aren't necessarily what's doing it. Your subwoofer might be primarily responsible for that punch. Yet the snare still sounds like it's coming from the front, because the correlated high frequencies are coming from there.

    So, if you want to pull the bass up front, a logical first step might be to not only quiet the panels in the rear, but to also get panels in the front to rattle with the bass. That's kinda ugly. A more practical step could be to allow your front speakers to reproduce some of that "rattle". Higher order harmonics coming through the front speakers should facilitate the illusion of up front bass.

    I've done something similar already by going to great lengths to "correlate" my subwoofer and my center channel(s). I've done this by channel mixing them the same way, by time aligning them the same way (they're actually both overdelayed relative to the side mids), and by carefully meshing the crossover points so that they blend together. I think this works. It could be my imagination, but I don't think so.

    I plan on going the next step in a few weeks with my carPC. I'll take a low amplitude bandpass filtered bass signal and deliver it to my center channel. I'll play with the amplitude and see if I can tweak the directionality. Lots of free parameters to get it to work right without being intrusive, but I think it will be the most effective method.

  4. #24
    Senior Member cvjoint's Avatar
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    MarkZ that's genius! Adding distortion up front would surely work. But what about those few that treasure low HD over staging? I think I've found the answer.

    PLAY THE RIGHT MUSIC.

    What we really need is a lot of ... "busy" music. The trick lies in reproducing tunes that don't have any unattended bass notes. Whenever there is low frequency content there is lots of high frequency content as well virtually masking the troublesome rattles. With this method you can see that we are reproducing the material as it is intended with no added material.

  5. #25
    Founding Member Subwoofery's Avatar
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    Quote Originally Posted by MarkZ View Post
    I haven't read the whole thread yet. [I will, I promise!]

    My suggestion for pulling the bass "up front" can be boiled down to two words:

    ADD DISTORTION.

    Why do panels evoke bass directional cues when the actual sound being emitted from the panel is often hundreds of Hz? Because these high frequency sounds are correlated with the bass, that's why. This is the same reason why you can get a snare to hit you right in the chest ... your midrange speakers aren't necessarily what's doing it. Your subwoofer might be primarily responsible for that punch. Yet the snare still sounds like it's coming from the front, because the correlated high frequencies are coming from there.

    So, if you want to pull the bass up front, a logical first step might be to not only quiet the panels in the rear, but to also get panels in the front to rattle with the bass. That's kinda ugly. A more practical step could be to allow your front speakers to reproduce some of that "rattle". Higher order harmonics coming through the front speakers should facilitate the illusion of up front bass.

    I've done something similar already by going to great lengths to "correlate" my subwoofer and my center channel(s). I've done this by channel mixing them the same way, by time aligning them the same way (they're actually both overdelayed relative to the side mids), and by carefully meshing the crossover points so that they blend together. I think this works. It could be my imagination, but I don't think so.

    I plan on going the next step in a few weeks with my carPC. I'll take a low amplitude bandpass filtered bass signal and deliver it to my center channel. I'll play with the amplitude and see if I can tweak the directionality. Lots of free parameters to get it to work right without being intrusive, but I think it will be the most effective method.
    Interesting and understand your point - vibrating door panels is annoying yet draws attention to it.
    However I'm not sure it's the right way to do it. I agree with "a logical first step might be to not only quiet the panels in the rear" however I don't know how you would "panels in the front to rattle with the bass" without disturbing you when you're doing some critical listening...

    Would like to hear more about your center channel and subwoofer mixing though

    Kelvin

  6. #26
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    How disturbing it would be is a function of our perception. I'm not convinced that we'd need to add so much that it would become disturbing. Just enough to draw the bass up front, no more than that. This would take some careful tuning -- amplitudes, freq content, delay, etc.

    I have no data to support this point by the way. It's just conjecture.

  7. #27
    Founding Member Subwoofery's Avatar
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    Quote Originally Posted by MarkZ View Post
    How disturbing it would be is a function of our perception. I'm not convinced that we'd need to add so much that it would become disturbing. Just enough to draw the bass up front, no more than that. This would take some careful tuning -- amplitudes, freq content, delay, etc.

    I have no data to support this point by the way. It's just conjecture.
    ^ and control of the environment. The thing is that most cars peak around 40Hz to 60Hz and the fun part is that (I think) freqs between 40Hz to 60Hz can really excite panels and create vibrations (distorsion) --> which leads to high freq content (as MarkZ pointed out).

    Isn't that the reason why so many people X their sub lower than 50Hz (mostly 40Hz) with a slope as steep as 48dB/oct? Not having access to a powerful enough EQ or giving up with sound deadening...

    I have a hatchback and I'm using a towel (don't worry it can't be seen) between the hatchlid and the removable reardeck - that helps cancel out the transfer of vibration from my deck to the hatchlid... <-- that way I've cancelled more than 80% of my distorsion, 20% left have been "dampened" (well more like 19%)

    Are you guyz using a lower Xover point due to the ability of your midbass to cover lower freqs? Or due to the fact that you want a less muddy sound (integration & vehicle acoustic)? Or due not being able to fully reduce vibrations? Or else...

    I've seen a few competitors that were Xing their sub @ 60Hz with a 24dB slope while others X theirs @ 30Hz with a 48dB slope - 2 schools of thought really...

    Kelvin

  8. #28
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    I think people lowpass their subs so low because they're using their sub as an EQ! They want boost around 40Hz. Either because they like low freq boost or because their enclosure starts rolling off around 40Hz and they're just trying to flatten things out. So, rather than use an EQ or tune their enclosure to achieve this added output at 40Hz and down, they just cross really low and turn the gain knob up. Makes sense I guess. EQ/bass boost would also make sense, but people are scared to death of boosting with an EQ for some reason.

    Anyway, if you can flatten the sub acoustically or with an EQ, it can safely extend much higher than the 60Hz or whatever the average crossover point is. The FR of most subwoofers extend into the hundreds of Hertz, leaving the only real limitation being directionality. If this can be solved (part of the goal of this thread, as I understand it), then you can use the subwoofer to its full potential instead of as a makeshift EQ.

  9. #29
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    I believe it is a mismatch of pressure at the ears causing an uneven phasiness.

    I tired this experiment with headphones and something that can mess with the phase on each channel separately (Betabugs Phasepass). Playing low frequencies only single tone and also pink noise. The good thing about headphones is that they remove extra variables.

    With one instance it creates an attenuated null in one direction. If you use two instances of this fed into the same two channels you can create different vectors that can cause the signal to add or subtract completely. Both feel very strange and cause you to want to turn your head until it matches and you don't hear or feel a differential. Makes sense to how we have evolved to stay alive. So if it makes you want to turn your head, then it's going to pull it backwards. I think the amount of the null will tell your brain it is behind you.

    Considering in a car, the location of the midbass is located at different azimuth angles, and then the sub adds in a third or fourth azimuth angle, this will have an effect on the room and standing waves. You may not know the exact location, but the different pressures felt in the ears will make you want to turn your head. Of course there are the other reasons, but this is definitely one of them.
    Last edited by durwood; 04-07-2011 at 10:50 PM.

  10. #30
    Founding Member Subwoofery's Avatar
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    Quote Originally Posted by durwood View Post
    I believe it is a mismatch of pressure at the ears causing an uneven phasiness.

    I tired this experiment with headphones and something that can mess with the phase on each channel separately (Betabugs Phasepass). Playing low frequencies only single tone and also pink noise. The good thing about headphones is that they remove extra variables.

    With one instance it creates an attenuated null in one direction. If you use two instances of this fed into the same two channels you can create different vectors that can cause the signal to add or subtract completely. Both feel very strange and cause you to want to turn your head until it matches and you don't hear or feel a differential. Makes sense to how we have evolved to stay alive. So if it makes you want to turn your head, then it's going to pull it backwards. I think the amount of the null will tell your brain it is behind you.

    Considering in a car, the location of the midbass is located at different azimuth angles, and then the sub adds in a third or fourth azimuth angle, this will have an effect on the room and standing waves. You may not know the exact location, but the different pressures felt in the ears will make you want to turn your head. Of course there are the other reasons, but this is definitely one of them.
    Interesting... Really happy I posted this thread

    Kelvin

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