calibrating a firewire external sound card? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 12 Old 12-30-07, 04:39 PM
jamminji
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calibrating a firewire external sound card?

Hi... I have a phonic Helix 24 MKII, 24 channel mixer that is ALSO a firewire 16 simutaneous track recording soundcard. It shows up in REW fine and iIcan do measurements, but I do not understand how to calibrate it since it does not have line in outs that go to the computer, only firewire ins/outs. I have the mic hooked up to ch 15/16. In REW it sees ch15/16 and it sees the correct main L/R out. How would I calibrate this set up?

Also i am using a SONY ECM-ms907 Stereo mic. Is there a cal file for this mic? Or Can I/How can I calibrate the mic also?

thanks... Jam
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post #2 of 12 Old 12-30-07, 05:38 PM
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Re: calibrating a firewire external sound card?


If this is what you have, you calibrate it just as the REW help files say: Feed one of the outputs into one of the inputs. Make sure any the EQ strip is set flat.

Regards,
Wayne



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post #3 of 12 Old 12-30-07, 06:28 PM
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Re: calibrating a firewire external sound card?

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Wayne A. Pflughaupt wrote: View Post

If this is what you have, you calibrate it just as the REW help files say: Feed one of the outputs into one of the inputs. Make sure any the EQ strip is set flat.

Regards,
Wayne
Yes that is it. But I am confused. This system sends the inputs signals through it's built-in firewire port, and receives signals from the computer via it's built-in firewire port not the 1/4" inputs/outputs. I must be missing something dumb here.

jam
 
post #4 of 12 Old 12-30-07, 08:30 PM
jamminji
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Re: calibrating a firewire external sound card?

This is how I have the system hooked up. Let me know where I go all wrong.

laptop running REW Helix 15/16 input and Helix main L/R output show in REW default input outputs in REW. Firewire cable to the Helix. SONY ECM-907 stereo mic running to helix channel strips 15 and 16. Helix 1/4" main L/R outs running to power amp then to JBL jrx-100 15" and horn PA speakers. I can get the output volume set to 75db using the internal REW generated tones but the only way I can find to adjust input volume is by the pre amp gains on the helix mixer and even with them turned up all the way I am still at about -40db. SO I have to turn up the volume on the amp for the mains and it get WAY to loud. Where am I falling apart?

jam
post #5 of 12 Old 12-30-07, 09:24 PM
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Re: calibrating a firewire external sound card?


That’s the correct connection scheme, but for measuring, not for calibrating the soundcard.

If you’re trying to calibrate the soundcard, you’ll need to loop a cable between the main output and the channel strip you intend to use, as indicated in Item #1 in the REW help files for Calibrating the Soundcard.

There should not be a mic connected, or a connection to the sound system, until later when you’re ready to measure.

Regards,
Wayne



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post #6 of 12 Old 12-30-07, 09:26 PM
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Re: calibrating a firewire external sound card?


Also:
Quote:
Also i am using a SONY ECM-ms907 Stereo mic. Is there a cal file for this mic? Or Can I/How can I calibrate the mic also?
You can create your own calibration file, but you’ll need a frequency response graph of the mic in order to do it.

But one thing at a time.

Regards,
Wayne



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post #7 of 12 Old 12-30-07, 11:36 PM
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Re: calibrating a firewire external sound card?

Ok got it... I hate plugging directly from ins to outs. But THANKS! ...it worked. Next problem is still the same though. When I do a measurement it tells me that the input is too low so a ctrank up the amp and the sound is piercing but it says too low, reading is about -50 to -40. I still get readings but not sure if they mean anything because of this. I will upload my soundcard graph and new plot. For some reason I get an "error on page" when I try to add an atatchment using this computer. I turned off pop-up blocker, but that did not help. And, Yes after this it is on to the mic!

jam

Quote:
Wayne A. Pflughaupt wrote: View Post
That’s the correct connection scheme, but for measuring, not for calibrating the soundcard.

If you’re trying to calibrate the soundcard, you’ll need to loop a cable between the main output and the channel strip you intend to use, as indicated in Item #1 in the REW help files for Calibrating the Soundcard.

There should not be a mic connected, or a connection to the sound system, until later when you’re ready to measure.

Regards,
Wayne
post #8 of 12 Old 12-31-07, 10:01 AM
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Re: calibrating a firewire external sound card?


Quote:
Next problem is still the same though. When I do a measurement it tells me that the input is too low so a ctrank up the amp and the sound is piercing but it says too low, reading is about -50 to -40.
Why not increase the gain and/or input slider at the channel strip the mic is plugged into?

Regards,
Wayne



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post #9 of 12 Old 12-31-07, 03:30 PM
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Re: calibrating a firewire external sound card?

I can do that too. But my question is after i get all the calibration done setting the spl to read what my spl reads (75db) and setting the volumes etc etc. Why do i have to turn up the volume for the measurement to well into the 100db+ range... I am covering my ears even with ear plugs, when the test runs. I think that I still don hae thing set right... agreed?

jim
post #10 of 12 Old 01-01-08, 08:53 AM
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Re: calibrating a firewire external sound card?

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agreed?
Agreed........
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