[lkos98]

Made some measurements with REW software, which confirmed my suspicions that the microphone doesn't have flat response. Compared are my beloved open back Koss dynamic headphones (in red), and the last designed circle ES headphones (L&R ch.). Except for the nasty peak drop around 1000 hz, the FR is much flater and looks better. Again I'm not sure about the bump at 20-100 if it's caused by the microphone or the headphones.

 

[tib8]

Made some measurements with REW software, which confirmed my suspicions that the microphone doesn't have flat response. Compared are my beloved open back Koss dynamic headphones (in red), and the last designed circle ES headphones (L&R ch.). Except for the nasty peak drop around 1000 hz, the FR is much flater and looks better. Again I'm not sure about the bump at 20-100 if it's caused by the microphone or the headphones.

Currently I have no tools for proper measurement, only a webcam, which unfortunately seems to cut above 8kHz and below 200Hz.

Ellipse (94x74mm active) with velour pads: orange, brown
Circle (87mm active) with leather pads: blue, green

Those high freq bumps likely due to the reflections from the leather pad.
Other smaller peaks also appeared/dissapeared during repeated measurements which are realted to the positioning of the headphone on the shoe box (which is also not reflexion free), which held the webcam/microphone.

There is an other pink noise measurement with ARTA: the ellipse is the orange, the circle is the green (-4dB).
And the last is a pink noise measurement with ARTA: my ellipse driver is the orange, my Sennhieser HD555 is the green (this time without my DAC + ESL amp, directly from my laptop soundcard, which increases the bass likely to get some out of its build in speakers, so again not good for real measurements).

I do not know if the above helps you. I just wanted to say that one measurement is not measurement. You need to do some averageing + take care of reflexions, positioning because your setup may be also very sensitive...

 

[lkos98]

One measurement is not enough - very true, but I made several. There was practically no difference, may be 1-2 dB in some places. I also don't think my microphone is good enough to call this a measurement. My setup is always noisy - wife's watching TV. I put the microphone on a thick cloth directly on the table and the cup on top of it aiming the center. Then I took several measurements, but they all look the same. I also tried to increase the distance with some 20mm thick rubber/foam round ring (I used it before as earpad) and the 1000Hz drop moved to 600Hz, but the overall FR remained the same. So yes, cavity resonances can cause peaks and drops. Microphone position and distance, the material of the cups, etc. By the way the free air resonance is about 100 Hz, this is the lowest I have ever managed. With all other designs I couldn't go less than 140 - instability. Overall I'm happy with the sound, I just need to increase the tension a bit more - may be 110-120 Hz, just to remove some of this overwhelming bass. It's great on songs with low bass (ELO, Alan Parsons), but try to listen to ERA or some heavy metal....I could really feel the vibrations.
Your 200-8k bandwidth looks good, but a shoe box can do a lot of damage - the volume is too big IMO and seal is almost not present. Just an idea - what about La Vache qui rit cheese box? Cut some holes bottom and top, fill with as much as possible cotton wool or something similar (without blocking the direct sound from the headphone to the mic) and seal with tape. My previous set was with a round MDF board with a microphone size hole, the phone was from one side, mic from the other and sealed. This was giving pretty good results, unfortunately I lost the board somewhere .

 

[tib8]

I saw and listened to such drivers

but i did it without a case
they need a special acoustic chamber
to make them sound

maybe someone has some idea of what it can be made of?)

There is a plastic which can be put into oven to make it hard (children toy).
From that you could form something which matches your ear.
Of course you should bake it without the driver (or at least without the membrane).

 

[KristinNelson]

It's incredible, I would also like such an amplifier. Recently, my husband got the idea to make a table that would be adjustable in height using linear actuators. He already ordered the drives and started carving the countertop
Welcome to this wonderful forum

 

[chinsettawong]

It's been a very long time since I made a new design of the headphones. With the COVID-19 lock down about to be imposed here in Bangkok, I think it's a good time to start something new. Of all the headphones I made so far, I seem to really like the JF style headphones. This time I will make the width of the diaphragm a bit narrower but keep the length to be the same.

The active area will be 60 mm x 120 mm. The tensioning of the diaphragm will be so much easier with this dimension.

The frame will be 3D printed.

Let's see how they will sound.

 

[ts8051]

Hello, thanks for your information, but he sells only 3 micron and not 2 micron.

 

[chinsettawong]

There is nothing wrong with 3 microns Mylar. I like it a lot.

 

[ts8051]

Why Stax uses < 2 micron mmbrane? The company knows something important about it. I think that 2 micron is better in high frequency reproduction.

 

[Torac]

3 micron is better at bass reproduction, 2 micron is better at detail reproduction but both marginally sacrifice the other. Personally I like the way 3 micron sounds as anything thinner sounds bass light to me.

 

[chinsettawong]

Well, if you really want to buy 2 micron Mylar, it's readily available on Ebay. Search for "electrostatic Mylar".

 

[Torac]

If it helps anyone, where I am most sellers won't ship the thinner mylars on eBay but I was able to source different thicknesses from freeflightsupplies.co.uk

 

[chinsettawong]

I was having some problems with my CNC machine since I haven't been using it for over two years. But, finally, everything is cut and ready. Hopefully I can test them before the end of this week.

 

[chinsettawong]

They sing and sound very nice too!

 

[Kerry]

Very nice