TOPIC:

Hi all,
I have a little question....
I use a high pass filter 2nd order for sub with freq, 25Hz.
But How can I change the Q factor of this filter??
Thanks

Belardinelli wrote:

But How can I change the Q factor of this filter??

Looking at my 10x10HD plug-in ... I don't see how you can change the Q.

You could increase the filter slope, though.

Belardinelli wrote:

I use a high pass filter 2nd order for sub with freq, 25Hz.

I'm confused here by your use of "HP filter" and "25Hz" in the same sentence??

If you really do have a HP filter set for your sub ... why are you rolling off the sub's bottom end?
(Why not let it go as low as it can go?)

OTOH, if you really meant "I use a low pass filter 2nd order for sub with freq, 25Hz" ... that's a very low setting for a sub? (My sub's LP filter is 24dB @80Hz! And I roll off my mains with a 24dB HP filter @80Hz.)

Andy

Hi Andy, thanks for your reply

Yes, I use the HP filter to have a similar response to the closed cabinet

Belardinelli wrote:

Yes, I use the HP filter to have a similar response to the closed cabinet

I'm curious to understand why you think this is a good thing?

Andy

By changing the filter alignment (Butterworth, Bessel, Linkwitz Riley) you are effectively changing the Q.

If those options do not meet your needs you can also implement a HPF with any Q you wish using the advanced biquad programming functionality (see link below).

www.minidsp.com/applications#com_content_article_153

Not sure what your ultimate goal is but I read your statement of trying to achieve "a similar response to the closed cabinet" as trying to match a particular Q and resonant frequency of a sealed enclosure. If this is the case using a Linkwitz Transform (see link below) will allow you to do this.

www.minidsp.com/applications#com_content_article_152

For example my subs are in slightly undersized enclosures so prior to equalization they have a resonant frequency of ~39 hz and a Q of 0.8, by using a Linkwitz Transform I can easily change this to a resonant frequency of 30 hz and a Q of 0.7.

Michael

OK
thanks for the instruction
that's what I need
Thanks

Hi All,
I downloaded the excel sheet.
in the HPF sheet I wrote the Freq=25 and Q=2
and after I copy/paste the a0,a1, numbers in the minidsp:
a1=1,998354393856100
a2=-0,998365094298449
b0=0,999179872038638
b1=-1,998359744077280
b2=0,999179872038638

....but it says the numbers are incorrect!
I think that I don't understand very well how to write the coefficients inside the minidsp
There is a guide? Thanks

The coefficients look correct for a 48 kHz plugin, however you need to make sure they are formatted correctly. Pages 30-32 of the 10X10HD manual show the correct formatting. See below for the correct formatting of your coefficients (note the placement of periods, commas, and labeling of biquad1).

biquad1,
b0=0.999179872038638,
b1=-1.998359744077280,
b2=0.999179872038638,
a1=1.998354393856100,
a2=-0.998365094298449,

Michael