TD Function - Driver Polarity Check

[PhilActiveAudio]

Hi Uli,

I did not found any documentation about the Driver Polarity Check function in the Wiki, so I am asking.

The TD function - Driver Polarity Check asks for 2 inputs (Lower Sweep Frequency and Upper Sweep Frequency) and returns 2 numbers (xx / yy). I presume that the Lower and Upper Sweep Frequency are the values defined in the LogSweep Recorder while recording a driver (Sweep Start and Sweep End).
Is that correct?

What is the meaning of the 2 numbers given in return? What are the values for a positive polarity and a negative polarity?

Here is the pulse of my mid driver recorded in range 250-25000 Hz and which looks positive to me:

Capture.JPG (314.6 KiB) Viewed 2790 times

Thanks in advance.

[UliBru]

Can you please be so kind and send me the pulse response in question? Thanks.
The polarity calculation is quite tricky and it may also fail. I like to investigate a bit more.

[PhilActiveAudio]

As requested, please find enclosed the pulse response.

[UliBru]

Hi Philippe,

thanks for the pulse. It has helped me to improve the algorithm for polarity detection. I have sent you a revised version of Acourate by PM for testing it.
Indeed the detection is quite tricky whereas a visual inspection seems to be simple.

[PhilActiveAudio]

Rapid check of the updated version.
The conclusion is more understandable but I think there still is a problem (check Supravox).

Bass - Supravox 400-2000

Capture - Supravox.JPG (311.73 KiB) Viewed 2754 times

Mid - Radian 950 PB

Capture - Radian.JPG (293.07 KiB) Viewed 2754 times

Tweeter - Guigue (a bit weird whatever the measurement software is)

Capture - Guigue.JPG (255.13 KiB) Viewed 2754 times

[UliBru]

Why do you use a range 250 - 25000 for a bass driver?
If you still have problems you can send me the pulse.

[PhilActiveAudio]

The range for the bass driver is 10-25000 Hz (measurement values) but indeed the XO is at 550 Hz. I will test again with range 10-1000 Hz.

[UliBru]

Mmh, usually a bass driver is used maybe up to 2 kHz. But up to 10 kHz?

Anyway for polarity check simply measure a driver in a safe range from f1 to f2 even without XO. The limited sweep does the job already. Then use f1 and f2 also in the polarity check.

[PhilActiveAudio]

You are right. The measure was large but as I said, I am using it in the range 10 to 1 000 Hz max as the XO is set at 550 Hz with a steep slop.

[UliBru]

If the XO is a 550 Hz lowpass then run the polarity check values from 10 to 550 Hz