This one ...
Why don't you include the fundamental? You have unselected that?
https://www.diyaudio.com/community/attachments/tweeter-56-or-74-film-dist-jpg.1440806/
And you SPLs, are they calibrated? At q meter?
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Why don't you include the fundamental? You have unselected that?
https://www.diyaudio.com/community/attachments/tweeter-56-or-74-film-dist-jpg.1440806/
And you SPLs, are they calibrated? At q meter?
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That's an Overlay view where the distortion levels are compared from many measurements.
To be able to compare, all measurements shown are relative a 0dB fundamental level; a perfect EQ.
As I intend to use EQ via FIR filters, I am not that interested in distortion measurements that are not dB relative.
I'm using UMIK-2, so SPL are calibrated per se, but as these are the short test membranes I have a 4Ω series resistance so that the amplifier sees a normal load. I also have different widths and thickness of the alumunium traces so I don't really compare SPL at this stage, other than the frequency response.
How can a Q meter help in this case? What Q meter do you in that case recommend?
To be able to compare, all measurements shown are relative a 0dB fundamental level; a perfect EQ.
As I intend to use EQ via FIR filters, I am not that interested in distortion measurements that are not dB relative.
I'm using UMIK-2, so SPL are calibrated per se, but as these are the short test membranes I have a 4Ω series resistance so that the amplifier sees a normal load. I also have different widths and thickness of the alumunium traces so I don't really compare SPL at this stage, other than the frequency response.
How can a Q meter help in this case? What Q meter do you in that case recommend?
What if you make the segments overlap a little bit? Then weeding should be easier.
Good idea, but I think the cuts will overlap even more in X direction making weeding harder; the "weed" will for sure brake when I try to pull it off.
OK, sorry, now I see I wrote "q meter"... that was a typing mistake - please forgive my sloppiness. Should have been "dB meter"...
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You are forgiven:
UMIK-2 isn't the most accurate microphone even with the calibration file.
But there are so much other variables that affect the measurements, positioning, no having an anechoic chamber and so on.
And I don't know how accurate my dB-meter is either over the frequency range.
But for sure, I can do a litmus test.
UMIK-2 isn't the most accurate microphone even with the calibration file.
But there are so much other variables that affect the measurements, positioning, no having an anechoic chamber and so on.
And I don't know how accurate my dB-meter is either over the frequency range.
But for sure, I can do a litmus test.
Attachments
For the record.
I made an oversized tweeter membrane, oversized in the meaning that the aluminium trace between the magnets were wider than the perfect 3mm.
In this case I tried 8mm between and 5.5mm outside the magnets, the left one in the picture below:
The reason for doing this membrane was to see if I could get away with an easier membrane to cut and weed.
I reckon that the membrane doesn't move that much being a tweeter; at 300Hz you'll need 100 times more movement than at 3kHz.
So the non linearity of the magnetic field density shouldn't matter that much.
I got a bumpy curve but also good levels in the high end:
Distortion went through the roof though below 6kHz:
So I guess I'm stuck with the membrane to the right.
I made an oversized tweeter membrane, oversized in the meaning that the aluminium trace between the magnets were wider than the perfect 3mm.
In this case I tried 8mm between and 5.5mm outside the magnets, the left one in the picture below:
The reason for doing this membrane was to see if I could get away with an easier membrane to cut and weed.
I reckon that the membrane doesn't move that much being a tweeter; at 300Hz you'll need 100 times more movement than at 3kHz.
So the non linearity of the magnetic field density shouldn't matter that much.
I got a bumpy curve but also good levels in the high end:
Distortion went through the roof though below 6kHz:
So I guess I'm stuck with the membrane to the right.
I think that I'm stuck the Silhouette Cameo 5 machine and the membranes as they are.
I'll just make enough of them and then pick out the best four.
I've tried cut 110mm segments with Cut by layer and Cut by line.
But the configured order and pauses are not saved in Cut by layer.
In both cases the machine cuts parts of more than one segment, so the membrane goes to and fro.
So there must be pauses between each segment and then I have the re-homing issue with mis-alignments in the X direction between segments.
Also, as the membrane and the cutting mat being rather heavy, I need some sort of conveyor rolls.
But I found that talcum powder does the trick of lowering the friction. As long as I don't sneeze.
To help with hitting the resume button,
, ChatGPT helped me with this script:
Script is included.
I'll just make enough of them and then pick out the best four.
I've tried cut 110mm segments with Cut by layer and Cut by line.
But the configured order and pauses are not saved in Cut by layer.
In both cases the machine cuts parts of more than one segment, so the membrane goes to and fro.
So there must be pauses between each segment and then I have the re-homing issue with mis-alignments in the X direction between segments.
Also, as the membrane and the cutting mat being rather heavy, I need some sort of conveyor rolls.
But I found that talcum powder does the trick of lowering the friction. As long as I don't sneeze.
To help with hitting the resume button,
Script is included.
Why I asked is from own experience and REW that can end up with whatever on the y-axis depending on mic and setting on the gain knob on the audio interface.... for distortion measurements I think the playout level is important metadata.
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Well, just redid the above measurements.
Here's some overlay with the 3mm membrane as well.
SPL:
Distortion:
And there not much of a difference in both SPL and THD, even for the higher harmonics.
I guess there was a disturbance during the measurement in the previous post.
time for a cnc 🙂 oooooor a cheap laser, then remove the laser and just add a roland cutter 🙂 prefered on a linear rail. might be the cheapest way of doing it, to make a plotter table 🙂
I've considered that further, but the cost and time needed scares me; a 2.5m long CNC with the accuracy needed must be of industrial grade.
Or, as ChatGPT put it:
I've just made two of the full length mid membranes and the two tweeter membranes will soon be done as well.
I will mount them into the speaker and start the measuring and EQ loops. And do some occasional listening 😱 .
While doing that, I will make more membranes and then select the best of them, the rest will be backup; I doubt that I will be able to make membranes in the future.
Or, as ChatGPT put it:
And I don't have the space for it.
I've just made two of the full length mid membranes and the two tweeter membranes will soon be done as well.
I will mount them into the speaker and start the measuring and EQ loops. And do some occasional listening 😱 .
While doing that, I will make more membranes and then select the best of them, the rest will be backup; I doubt that I will be able to make membranes in the future.
the above is ... well not a huuuge deal 🙂 (i have a 1.3 meter long table and dont use closed loop) not more then a roller that moves a 2.5 meter long thing back and forth 🙂 (just the slightest misalignment or not perfect roller will result in a cutting matt wondering off) stiffness is not a huge thing since there is no cutting force. but anyhow.
PRO XY cutting tables use simple bearings and use steel wire to drive it 🙂 almost bought one if i could fit it... with vacuum table. but the thing itself was rather simple. (it was build like a tank but i think thats mostly because it was professional equipment) by the way most lasers dont use fancy linear stuff or servo's
but if this works !! then there is no reason to change indeed! i am still impressed what a 300 euro cutter can do to be fair
PRO XY cutting tables use simple bearings and use steel wire to drive it 🙂 almost bought one if i could fit it... with vacuum table. but the thing itself was rather simple. (it was build like a tank but i think thats mostly because it was professional equipment) by the way most lasers dont use fancy linear stuff or servo's
but if this works !! then there is no reason to change indeed! i am still impressed what a 300 euro cutter can do to be fair
Well, the Silhouette Cameo 5 is €500 here in Sweden, and it will soon cost even more due to the trade war.
I think that it will not be that easy and cheap to build my own CNC cutter that long and narrow.
I've already built two plasma CNC cutters, one cartesian and one CoreXY.
And I foresee a lot of hours building this one with the wanted accuracy (0.1mm).
I think that it will not be that easy and cheap to build my own CNC cutter that long and narrow.
I've already built two plasma CNC cutters, one cartesian and one CoreXY.
And I foresee a lot of hours building this one with the wanted accuracy (0.1mm).
aaah ok cameo 5 🙂 i did not know they where that expensive 🙁. well yeah building something yourself might get out of hand on cost (besides the fact you make insane long ones 🙂 size is an issue 🙁 ). well if you make a coil accuracy of 0.1mm (or repeatability) are both different things. after 3000 moves then go back to the original place with 0.1mm is a lot harder then following a coil patern with 0.1 accuracy. i mean ever move it makes with a few micron slop/steppers faults etc adds up over time.
anyhow looking forward to your new coils ! by the way cartesian is that with the weird belt setup ? used in some fast 3d printers ?
anyhow looking forward to your new coils ! by the way cartesian is that with the weird belt setup ? used in some fast 3d printers ?