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Topic: Acoustic Mirror discovery

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  1. #1

    Acoustic Mirror discovery

    I just discovered a disappointing feature of Acoustic Mirror, which I believe very much reduces its value as a \"reverb\" application.

    When you pan the input signal hard left or right (e.g. just mute the R or L channel in SoundForge) and then apply Acoustic Mirror, the output is also hard completely panned left or right. Not a single bit of sound leaks into the virtual room.

    I find this really odd; I\'d expect to hear normal stereo reflections. Is this indeed intentional behavior? Cannot imagine AltiVerb also behaves this way.

    Bruce? Ernest? Hasen?

  2. #2

    Re: Acoustic Mirror discovery

    Peter,

    This is true. My workaround for the last couple of years has been to render the completely wet impulse version to a (stereo) audio track. The impulse is applied to a temporary version of the mix that has the instrument placements significantly narrowed toward the center of the stage. I then use the resulting stereo impulse track as if it were a reverb return and adjust its level relative to the dry (and fully panned) version of the mix. Instruments panned far left and right now have reverb contributions in both channels. Experiment with the amount of narrowing in the mix you use for the rendered impulse tracks. Works for me.

    Tom

  3. #3

    Re: Acoustic Mirror discovery

    One more thing: I was assuming (in my reply) the use of a multi-track audio program in addition to Sound Forge. It can also be accomplished from within Sound Forge by making a second copy of the fully panned version of the mix, narrowing the stereo stage on the copy, applying the impulse (100% wet) to the copy and merging the resulting file with the original mix. Adjust the relative balance of the two during the merge.

    Tom

  4. #4

    Re: Acoustic Mirror discovery

    Thanks Tom, nice tips. Will check them out in Logic and SoundForge. The bottom line is indeed if it sounds good and not if the solution is correctly modelling the original hall.

    Peter

  5. #5
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    Re: Acoustic Mirror discovery

    Just to add to that, FWIW, I \'ve found that for a heavily panned (esp. solo) instrument it pays to have two wet tracks, using the same impulse, but set for different room sizes: one a little shorter, the other with reduced early reflections and darker. The shorter one you pan to the side of the instrument, but keeping it more central, the other you pan to the other side but more lateral, then tweak the relative volumes, the latter needing at least -6db.

    Although easy to overdo, this gives you a better image with a real sense of space.

    In fact I keep a time stretched copy of my favourite impulses, to use on the far side to avoid having to shorten the original impulse for the near side. I imagine this sound even better (probably no different)

    I haven\'t tried this with an instrument totally panned 100%, I can\'t imagine a situation where that would apply

  6. #6

    Re: Acoustic Mirror discovery

    The 100% lateral positioning was just to illustrate the problem, which I believe must be a serious design error. [img]images/icons/frown.gif[/img]

  7. #7
    Senior Member
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    470

    Re: Acoustic Mirror discovery

    Sorry, yes of course.

    The same happens with Room Simulator (the impulse convolver in Samplitude). If you apply any effect to a channel with no signal would you expect any output?. Or have I misunderstood the problem?

  8. #8

    Re: Acoustic Mirror discovery

    Yeah it doesn\'t happen with Altiverb. The hard pan goes through but is nowhere near as hard in the wet signal. Is this a bug with Acoustic Mirror then?

  9. #9

    Re: Acoustic Mirror discovery

    Originally posted by Beckers:
    Sorry, yes of course.

    The same happens with Room Simulator (the impulse convolver in Samplitude). If you apply any effect to a channel with no signal would you expect any output?. Or have I misunderstood the problem?
    <font size=\"2\" face=\"Verdana, Arial\">The hardware and plugin verbs I know provide at least some stereo diffusion, so that a completely lateral sound (when entered as stereo feed) results in added, wet sound on the other \"side\".

    If I put a trumpet player next to the left wall in the Concertgebouw hall (site here), and record with a stereo mic setup, I do expect to pick up a lot of signal also with the right mic...

    Now wouldn\'t we just love to have a similar effect with Acoustic Mirror (and the Gos impulse)? [img]images/icons/wink.gif[/img]

    Cheers,
    Peter

    PS: check http://www.audioease.com/IR/VenuePages/Concertgebouw.html for some cool photos of that beautiful hall. Accidentally on the AudioEase website... [img]images/icons/wink.gif[/img]

    See those chairs on the stage? Yes, you can actually enjoy a concert 1 meter away from the players, within the orchestra!

  10. #10

    Re: Acoustic Mirror discovery

    You can control this to some extent with Response Width controler. As soon as you go over 50 the signal starts to leak in the opposite chanel....

    Alex

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