Audio-visual experiment with 4 speakers - Problem with more than 2 speaker stimulation

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Hi all,

I have 3 PsychPortAudio related questions. We want to use 4 speakers to simulate a moving white noise sound. We have a Soundblaster Z and Soundblaster X-Fi soundcard.

1)    Strangely, Soundblaster Z has only 2 output channel with PsychPortAudio. Does anyone know why?

2)    Soundblaster X-Fi is working, at least kind of. However, for both sound cards we have the problem that the rear speakers produce a completely different sound than the front speakers. The sound of the rear speaker seems to be reduced - meaning the sound seems to have less frequencies and it is also not as loud as the front speaker. This is also true, when you e.g. just play music outside of PTB. Is there a work around to make all speakers sound alike, or is it just impossible to use common 5.1/7.1 soundcards for multi-speaker stimulation?

3)    Is there an alternative soundcard (for more than 2 speakers) which is compatible with PsychPortAudio? We thought of buying this device:

https://www.rme-audio.de/products/fireface_uc.php

If there is no soundcard for ’more than 2 speaker‘ setups, how can we create a 4 channel output for multisensory (meaning high timing precision) experiments with PTB.


Any help is highly appreciated. Thank you for your help!

Best, Felix

PS: I know there was a related question by Falko (who’s a former colleague) but this does not solve the problem.
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Sorry, for some reason yahoo does not allow me to send message for my original post ...

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Hello elladawu,

Thank you for your fast reply. Good to hear that the sound card we have in mind is a good choice. However, do you have expierience with it and is it compatible with PsychPortAudio? This is crucial as we want to use PsychPortAudio and no 3rd party extra software. And in PsychPortAudio it should also have more than 2 output channel.

I'm just asking because it is rather expensive and all the labs we know using this card do not use PsychToolBox (do not use PsychPortAudio) but always some other software (because it's usually pure psychophysics audio labs), especially for the multi-speakers stimulation (meaning more than 2 speakers).

Best, Felix


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Hi Felix,

I would not give up on the X-Fi card yet (we are actually very happy with our X-Fi Titanium HDs providing very low latencies and jitter and well supported under linux). We had a working setup with an X-Fi Xtreme some years ago with 4 speakers using Psychtoolbox (unfortunately no longer available).

Which OS are you using? Have you tried Linux? In case Windows have you tried switching the driver to "audio creation mode“ combined with „bit accurate playback“ (different panel) and disabled all effects in the Creative audio control panel? Have you checked loudspeaker configuration (Windows control panel -> sound -> right click on Creative X-Fi -> loudspeaker configuration)?

We had very mixed experiences with external USB or Firewire cards in the past. We had problems with onset jitter in particular under moderate and high system load (too large for electrophysiology).

Best,
Andreas

> Am 12.11.2016 um 12:36 schrieb felix.ball@... [PSYCHTOOLBOX] <PSYCHTOOLBOX@yahoogroups.com>:
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> Sorry, for some reason yahoo does not allow me to send message for my original post ...
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> Hello elladawu,
>
> Thank you for your fast reply. Good to hear that the sound card we have in mind is a good choice. However, do you have expierience with it and is it compatible with PsychPortAudio? This is crucial as we want to use PsychPortAudio and no 3rd party extra software. And in PsychPortAudio it should also have more than 2 output channel.
>
> I'm just asking because it is rather expensive and all the labs we know using this card do not use PsychToolBox (do not use PsychPortAudio) but always some other software (because it's usually pure psychophysics audio labs), especially for the multi-speakers stimulation (meaning more than 2 speakers).
>
> Best, Felix
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we have used a range of RME audio interfaces over the years, over PCIe, USB and Firewire, in stereo and multichannel setups.

on a well configured system, we have had very reliable timing. most of this research has been multisensory stuff, and we always validate each experiment by concurrently recording the audio output and the video output using a photodiode.

we do avoid running stimulus presentation machines under high load.

if extremely low latencies are required, then a PCIe or Thunderbolt connected interface would be the best choice. most experiments don't require extremely low latencies however.