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dumrum 27th May 2004 07:52 AM

Speaker Workshop Question: Help please
 
I have been trying to use Speaker Workshop and measure my Driver TS parameters. But it seems my activities have reached a hard stop. The reason being that I get different values for the T/S parameters each time I redo the measurements.
I have been following the instructions provided at

http://planeta.terra.com.br/educacao...negro/english/

and have also built the Wailing Jig. The jig measurements seem very much as close as possible to the values mentioned in the Wailing jig home page.

But I followed the steps mentioned at http://planeta.terra.com.br/educacao...negro/english/

and used the RMAA to analyze my soundcard.
When I did so with different Sampling rates, I nowhere reached close to the ideal values and always kept on getting a result saying that the interchannel leakage is high or that input volume level is too low. But on using an amplifier, then it goes to clipping and if I reduce the volume again I get Inter channel leakage + low volume indication.
Then I checked my frequency response graph. It is steadily flat till about 10 Khz. Above this, the response starts to be bumpy and rolls over to 0 response at 20kHz.
My concern here is whether my soundcard is upto the mark for use with Speaker Workshop.

Another issue I face is with the input impedance measurement of the soundcard. Each time I redo the measurement with the jig, it shows different values. Could any body tell me the right way to measure and what I am missing.

When I calibrate SW , the measurement. Calibration signal shows both right and left response as flat lines( in lines with expected results). Could anyone guide me on this.

All help is appreciated.
Thanks in advance.
regards,
Linoj.

ashwin 27th May 2004 08:53 AM

Re: Speaker Workshop Question: Help please
 
Hi Linoj,

one thing to check for when using RMAA is to make sure that any sound effects supported by your sound card (like 3d sound/spatialization, bass boost etc) are all turned off. Next, it might be a good idea to mute all volume sliders in the volume control window except the one that RMAA uses. IIRC RMAA requires only the wave (and possibly SW synth) volume to be unmuted. To be sure that everything else is off, click options->properties in the volume window and enable all controls to be shown, and then mute them.

For the channel leakage problem, make sure that you've wired the left output to left input and right output to right input in your feedback cable.

One thing I noticed with RMAA was that in 192Khz sampling mode it reported channel leakage, but worked fine in lower modes.

Hope that helps.

- Ashwin

dumrum 27th May 2004 09:54 AM

Speaker Workshop Question: Help please
 
2 Attachment(s)
Thank you Ashwin.
I believe the wire connection between both left and right channels are correct.
And my soundcard is Crystal WDM soundacrd. It does not have any additional sound effects.
I have attached the frequency response graph for your reference.
How much of an effect will this kind of a response have on the SW measurements?
And can anyone answer my other doubts about the calibration and Input impedance?


Thanks and Regards,
Linoj Job.

dumrum 27th May 2004 09:55 AM

Oops ..sorry for the huge image..
Will be careful from next time onwards.....

Linoj.

UrSv 27th May 2004 10:30 AM

Looks fairly normal for some sound cards I'd say.


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