Thiele Small Question

[brunohydra]

Hello everyone!

I'm doing some tests with REW to get T&S parameters and I had a question about a accuracy of my measure. I think that my audio interface doesn't have the necessary gain to get a perfect curve because if I use -12 dBFS I get a curve with a lot of peaks and when I use 0 dBFS the response is quite better.

I don't have a amplifier to use in the middle (I accept suggestions).

So I will add some images of my tests:

1 - My Audio Interface, M-Audio M-Track https://www.m-audio.com/legacy/m-track.html

2 - Speaker I'm measuring, JBL 62V2A 6 inches https://www.jbl.com.br/on/demandwar...BL_62V2A_-_par_28085151_manual_portuguese.pdf

3- Soundcard levels:

4- Soundcard calibration:

5- Open Circuit Calibration:

6- Short Circuit Calibration:

7- Reference Calibration (456 Ohms):

8- First measuring using -12dBFS:

9- Second measure using 0dBFS:

10- Measure 0dBFS with added 14g mass:

11- TS result:

12- REW result side-by-side with factory measurement:

My mainly question about the measure I got is:
Is it reliable?

Thank you.

 

[John Mulcahy]

Doesn't look very reliable. You can find tips on measurement setup in the Speakerbench manual. Use a resistor closer to the range of impedances you expect to measure for the reference calibration step. The measurements are suffering from mains hum pickup and noise, rearranging the positions and layout of the test leads may reduce that. The interface headphone output may have better drive capability.

 

[sm52]

If as a result you have received almost factory TS parameters of your drivers, this confirms the correct measurement. The obstacles visible on the graphs are the result of poor contacts and network interference. The resistance of a short circuit should be much less, 0.5 om or less. But this does not cancel the result. In the factory parameters there is SD = 137 cm sq. You indicated 152 cm sq.