Coaxial Compression Driver DIY (CCDIY) discussion

[weltersys]

Also, the compression ratio is 8:1, which provides an airspeed of roughly 5,5 m/s at the phase plug with 91 dB, 400 Hz.

What do you think the compression ratio is on this annular diaphragm:

Any estimate of it's airspeed when the SPL is over 160dB ?

This speed through a non optimized, crudely printed phase plug could be the source. Still, It doesn't directly explain the peaks at 4 and 500 Hz.

The noise floor has those peaks, as do all the harmonics.

PS: as this design is related to the dcx464, which is patented. I'm careful with sharing details (drawings etc) which could cause indirect infringement of the patent.

Unless you plan to copy the all the patent details (annular diaphragm ect.) and sell the drivers, not much to be careful about.

Art

 

[newvirus2008]

Dear Ice cream,

You don't need to worry much about infringement unless you're planning on commercialising this work / result of yours. You could use the details in the patent for personal / research purposes without consequence.

 

[ImpatientIcecream]

@weltersys thanks for the insights.

Any estimate of it's airspeed when the SPL is over 160dB ?

Sometimes i feel like an apprentice again...

You could use the details in the patent for personal / research purposes without consequence.

True, but there is indirect infringement if i help others with my work/results to replicate the design/claims in the patent. I could share details, but it will need to be educational, not with the goal to get others to replicate the claims. For example, i cant share 3D files which can be used for manufacturing/3D printing.

Also, would love to make this work my job. I found some loopholes in the patent which could be used for a commercial product.
Before getting too lost, i need to learn a lot about R&D in acoustic design before anything else, as you might have noticed.

 

[Nissep]

Late to the discussion but, my take on a low cost coaxial compression driver is far easier.
https://renkus-heinz.com/core-technologies/

So far I have made a 1" CoEntrant adapter and a 2". Simple conical expansion from the phase plug of the compression driver to the desired exit diameter.
What i haven`t tried yet is to design for a melamine plug in the ports for the midrange. That would qualify as a impedance miss-match device.

 

[Olombo]

Hi Nissep

large midrange holes! Did you make any off axis measurements you could share? I am quite interested as you have many midrange ports but they are so close that I am curious how much they really disturb the HF.

 

[ImpatientIcecream]

Late to the discussion but, my take on a low cost coaxial compression driver is far easier.
https://renkus-heinz.com/core-technologies/

Awesome work!

That would qualify as a impedance miss-match device.

In the patent they call it the "passive low pass filter". It blocks the HF from entering the MF ports according to the patent. Im curious what the effect of your MF ports are on the HF as yours are large enough for HF to pass. Aka, do we realy need to make a "passive low pass filter"? Unity horns work without it.

 

[Nissep]

For me to investigate the holes influence I simply need to make a cone and insert it. But from memory i don't think i did this.
To be honest, I`m terrible at keeping record of these tests I do.
Short attention span, and then I move on to next test shiny thing in my mind.

But 600-20000Hz low distortion from a 6" coaxial that at the time costed ~100usd.
I did test the 2" on a JBL 2380a clone and could replicate the data sheet. But I felt something was off, getting ear fatigue and blamed the horn.
So i moved on to a 1" version to use other horns.