calibration of sound card and mic preamp

[widi]

;x(
Hello friends I am new to these forums, I hope you can help me.
I am very new to the design and construction of speakers, I hope you understand me, and I am using soft LspCAD version 5.25pro, I bought a sound card Esi Juli@ mic preamp and an M-audio pre usb Moblile and a microphone Beheringer ECM8000, all these components plus a 2 x 20W amplifier to perform measurements with justMLS.
I made a box of measurements according to this post: http://www.htguide.com/forum/showthr...6&page=1&pp=35 of dlneubec to your schedule.
The problem I have is that I do not know how to calibrate your sound card to the preamp and before the SPL measurements.


Thanks in advance

Greetings to all.

[ThomasW]

Having the M-Audio Mobile Pre you don't need Esi Juli@ mic preamp

Do a 'loop-back' = output of one channel into the input of other channel input

[widi]

Thanks ThomasW's, Maybe I was wrong to tell, the mic preamp is the M-audio because juli @ sound card does not have mic input. I want to do is calibrate the preamplifier along with the sound card so that the calibration takes into account the transfer function of the preamplifier.

[ThomasW]

The M-Audio moble pre is both a USB duplex soundcard and a mic pre-amp with phantom power. This means nothing else is needed other than a microphone and computer

[widi]

But if I connect the jig to the m-audio if the output and the input is mono?.


Greetings.

[ThomasW]

Mono?

Yes that's how loudspeaker testing is done.

No jig is needed to calibrate a soundcard...Calibrating a sound card requires the output of one channel be sent to the input of the other channel. Then a sweep is run.

[widi]

I know, but if the mic is connected to only one channel and want to make the measurements in two channels, then I'm missing a channel. So using the sound card to connect the jig to another channel, in this case in the right channel.
This is not how to connect?, Or am I a mess for measurements on two channels?.

[ThomasW]

Measurements aren't done in stereo.

One soundcard channel is used to send the sweep (test sound) to the speaker or speakers, the other soundcard channel is used to record the signal coming from the mic as it's measuring what's being reproduced by the speaker or speakers

[widi]

In Correct me if I am wrong then, do the calibration in the following manner:
1st: Tapping the input / output and adjust the channel gain two, and proceed to calibrate the preamplifier.
2: connect the microphone in the canal, and a gain adjustment equal to the two channel
3: Connect the two channel output, the amplifier and the input of channel 2 is connected to the jig.

[widi]

Thanks again ThomasW, I calibrated everything correctly.
A question for measurements with the tweeter is needed to protect the condenser. What capacitance should have?.
Thanks again for your help

Greetings. :T

[ThomasW]

The value of the capacitor depends in the impedance of the tweeter and what frequency you want to use for the roll-off.

Here's a link to an online 1st order calculator

http://www.the12volt.com/caraudio/crosscalc.asp

[widi]

Thanks Thomas, I have been very good to me the website you gave.
Now to take the measurements as we have given me.

Greetings. :T