Resistive port cardioid active speaker insipired by D&D 8C

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#621
tmuikku said:
paalj, thanks for the link! It is hard to remove stuff from the Internet 🙂



Yeah the measured pattern is probably influenced by the enclosure, my proto is lots smaller than 8c and port is closer to front so must be difference without even knowing whats inside.

The dipole pattern is just out of band, I used the results on the left of that image (8pr155) in the system, xo is about 300Hz where DI dips a bit. It was better match a bit higher up to DI of the woofer but the woofer box starts to have its own sound going on that high, it was designed for another system. I was happy when I saw the DI in the proto, pattern widens towards the woofer and narrows towards the treble which (sth100) also has rising DI and the result is smoothly rising DI without hickups. Not text book stuff with constant directivity but still a nice sound. DSP and c-c is tuned for smoothest DI and early reflections.

Anyway, found some measurements here Dutch & Dutch 8C Quasi-Anechoic Spinorama and Measurements | Audio Science Review (ASR) Forum . My system sim result is not nearly as perfect as 8c measurement but not that far away for a weekend experiment so gotta be happy!😀

I've been so excited about the new prototype it has been almost two years from previous one. Sorry being a bit arrogant today, hopefully I don't appear always like that 🙂 Loads of fun though, more smilies than usual.

Attached is VituixCAD project to test the simple cardioid emulation if anyone wants to tinker what lowpass, attenuation, delay and distance of the back side (Z) does. Try to get max attenuation to 180 degrees for cardioid. Widest bandwidth and highest DI seems to be found towards dipole / hyper cardioid stuff where strongest null is more to the side and some output at the back. Lots of stuff to think about, how to implement into a system, how to build etc. Tried to tinker with it and could find situation where delay or attenuation would help, maybe one or two db attenuation was helpfull to get the null exactly to the back side. Maybe the resistance stuff is relevant with cardioid subs?
Click to expand...

How does one make those digital delays?

I've looked on YT, I've read the manual, I read the thread on htguide.

I can create a digital delay by taking your model and copying your digital delay block into my design, but can't figure out how to insert one any other way.
 
#628
Simply put, Thiele Small (TS) parameters other than Sd (surface area of the driver) don't have any effect on a speaker's directivity control.
A driver with a smaller Sd theoretically has wider dispersion than one with a larger area.
The Sd parameter assumes the driver to be pistonic, while in reality it is not, so even that TS parameter is of little use regarding it's DI (directivity index).
 
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#630
I doubt it can't be measured if it produce something you hear.
That said i've been asked myself about QES too: if choosing drivers initialy developed for open box is not better. In fact as cardio is a mix between OB and sealed it might not been an issue depending on frequency range to be reproduced ( i think for low freq it can maybe make a difference but for high mid i doubt given the number of working projects based on 'regular' bass reflex designed drivers).
 
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