From: Marc Lavallée <m...@hacklava.net>
To: sursound@music.vt.edu
Sent: Thursday, June 2, 2011 8:04 PM
Subject: Re: [Sursound] Bass Problem in crosstalk cancellation
>But those filters were designed to work with full range speakers, so
>unless the mains are on top of the subs I suppose it is better
>not to use the filters with subs that are apart from the mains.
In my opinion and experience, there is no difference in low bass handling for
Ambio vs stereo. In the TacT processors, for example, the subwoofer crossover
comes before the crosstalk canceller, if I remember right. So the subwoofer
frequencies are not cancelled and you can put them anywhere. Even if the
crossover after cancellation or is in the subwoofer, and the subs are being
crosstalk cancelled, the effect is negligible. Indeed, in stereo, central bass
sounds are doubled because both speakers reach both ears at full level compared
to side-only bass where only one speaker reaches both ears. With RACE this
effect is reduced by about half due to the ongoing feeble but recursive attempt
to crosstalk cancel at low bass frequencies. Of course, most RACE gadgets
include a bypass control but if you use it you get back the stereo doubling.
>> I think we are splitting hairs here.
>On the contrary, it's very interesting!
Thanks. That makes two of us.
>> It is
>> incontroverible that the human ability to localize declines with
>>frequency. Based on the Bose experiments and other AES papers
>> written too long ago to remember, 90 Hz is where localization begins
>> to become difficult. This is very hard to verify because all
>> subwoofers have harmonic distortion and one localizes to that. Also
>> in the early days, and even now apparently, the crossovers were not
>> steep enough to prevent some energy over 90 Hz from reaching the
>> subwoofers. I am sure somebody did it before Bose, but as far as I
>>know he was the first to make a completly passive crossover network
>> steep enough to allow the subwoofers to remain unlocalizable to
>> anybody except Fons.
>I did a basic experiment with twos subs and a sound generation software
>(PureData with the equal_power_pan extension). I panned a bass sine
>tone from left to right and back, changing the frequency between 40Hz
>and 160Hz. I was able to localize the sine tone at certain frequencies,
>depending on my position in the room; at 70Hz the tone was very easy to
>localize. So it's definitely possible to create a sound field with
>directional bass, intentionally or not.
I admire your ability and will to do this experiment.
If you can prove this via a peer reviewed AES paper you will be an AES fellow
in no time.
But do you really believe that if you can localize at say 70 Hz but not at 80
or 60 that that makes sense?
Suppose the frequencies were 500 and 700. Selective non-localization at any
frequency below about 2000Hz to about 90 would be a new psychoacoustic
phenomena. Most things in human hearing are gradual with frequency unless the
pinna are involved.
--
Marc
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Le Thu, 2 Jun 2011 14:27:24 -0700 (PDT),
Ralph Glasgal <rglas...@yahoo.com> a écrit :
>>Obviously there is no reason not to use subwoofers with RACE, Wareing,
>> or Choueiri.
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