Help with active crossover settings

[MAB]

Hi All. I've built a pair of Heissmann DXT-Mon-182, and I built the analog crossovers. They measure very well. But I also want to use my MiniDSP Flex-8 to try a DSP crossover.

Here's the problem. On Heissmann's site, he specifies the crossover as 1950hz LR 4th order. But he sent me the attached parameters for DSP, and I can't make heads or tails of the 1st and 2d order crossover notations. On the Flex-8, I can only input one high- or low-pass per driver. How do I use Heissmann's 1st and 2d order figures?

FYI, I have already input a LR4th at 1950hz, and I used the DSP parameters on the attached. For the drivers being used, the 1950hz figure falls right where it should per the mfr. spec sheets, and higher or lower tends to increase distortion for one or the other driver. My initial settings got a very good measured result except that the overall tweeter level measured a bit high when I did a near field measurement (and it sounded a bit hot, too).

The first-order at 7293 Hz is to manage the downward slope of the DXT above 6kHz. It has 6 dB/octave slope, screen captured Seas' spec and superimposed 6 dB/oct on top of it.

I hacked together the tweeter's response and the 1st order filter, it's easier to see how it removes the large hump due to the waveguide and combines with the acoustic roll-off of the tweeter to make a 12 dB/oct high-pass, at least for part of the response:

Putting the tweeter together with all of the filters:

It looks like a very competent crossover. It addresses the falling response of the tweeter at high frequency, and results in a nice 24 dB/oct acoustic slope.

If you were to do active, it might be a good idea to keep the capacitor for the 6 dB/oct filter. It will be protection against DC and other accidents and events. It will also lower the noise level of the tweeter. Here is a comparison with active vs. passive 1st order filters at 7293 Hz:

The mismatch below 1.8 kHz is due to the changing impedance of the driver interacting with the 3 uF capacitor. Retaining the L-pad in your passive crossover (R6 and R7) will further linearize the impedance and the active and passive responses will match even closer. It will decrease any hiss further.

I hope this helps with the tweeter section.

 

[suttondesign]

thank you so much. for now, I am sticking with the outboard passive analog x-overs. i could not figure out to do the dsp crossover using the minidsp flex 8 because it has only one crossover per channel. wheni used the minidsp biquad calculator, the result was strange. i figure, why mess with heissman’s passive, especially since it was pretty expensive to build. plus, i am proud that I was able to build these crossovers correctly.

 

[fluid]

i could not figure out to do the dsp crossover using the minidsp flex 8 because it has only one crossover per channel. wheni used the minidsp biquad calculator, the result was strange.

If you want to try the active values from Vituix provided you can have Vituix create the biquad coefficients for you. In the Options menu set the DSP to the MiniDSP and sample rate you are using to get the right coefficients.

You can click on each filter block individually and then right click and copy biquad coefficients

Then paste them into a separate EQ block in advanced mode

Or use shift to select all the blocks together and then right click to copy the coefficients

Which will give you multiple biquads which you can paste altogether into one block depending on whether you want any kind of individual control over the filters

This should give you exactly what was designed without any guesswork. You can then check the filter response to compare and make sure you got what was intended.

 

[Digital_Thor]

But, still I wonder how you make Vituix take the shape and size of the cabinet into the mix.
Do someone have some simple step by step to use the software, since my success with it is uphill

 

[fluid]

But, still I wonder how you make Vituix take the shape and size of the cabinet into the mix.

Far field acoustic measurements already include the effects of the cabinet. For nearfield spliced measurements you would use the Diffraction tool to simulate the baffle diffraction and combine it with the nearfield and farfield data in the merge tool.

It is possible to use Vituix to do feasibility investigations either with 2Pi manufacturer data or based on the piston size although it needs to be said that this has limitations and real measurements are much better to work with.

You might find these helpful for that
https://drive.google.com/file/d/1j9leycXJNvUmYZxQNVqg8U13mMRHh8Iw/view?pli=1

https://www.diyaudio.com/community/threads/vituixcad-simulations-with-ideal-drivers.380658/

Do someone have some simple step by step to use the software, since my success with it is uphill

The offical measurement instructions explain how to use the software with real measured data, there is a link in there to some older youtube videos that might be helpful

https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_Measurement_REW.pdf

 

[Sokel]

But, still I wonder how you make Vituix take the shape and size of the cabinet into the mix.
Do someone have some simple step by step to use the software, since my success with it is uphill

Once you start is dead easy, imagine that I modeled mine and I know nothing about design (and I resist with my life to it, we have a specialist home who would look down on me )
You just put the dimensions, angles, etc.

I would post pictures but @kimmosto has forbidden that at this site. I guess it's his right, no judgment to it.

 

[Digital_Thor]

Once you start is dead easy, imagine that I modeled mine and I know nothing about design (and I resist with my life to it, we have a specialist home who would look down on me )
You just put the dimensions, angles, etc.

I would post pictures but @kimmosto has forbidden that at this site. I guess it's his right, no judgment to it.

I got as far as drawing a square and putting some circles in it. But making slanted edges, and fiddling with coaxial drivers... I just realized that I didn't need to, since I've kinda just copied KEF's work, which made its own logical solution for me, by simply measuring the speaker and adjust the DSP to fit.