Hi,
I have done in fact two experiments with different goals:
1) The effect of wire ESL structure on sound coming from external sources.Like what you could expect if such an ESL was used as a mic.
I do not intend to so but it was interesting to me.
2) Try to observe partial diaphragm modes in mid range and treble and what effect the membrane tension has on this. Some people have mentioned that effects of partial modes can show up to midrange.So I wanted to collect some evidence for or against that.
Regards,
Lukas.
Bazukas,
I have been involved in a flat panel speaker development in the past and one issue that did crop up was the bending modes and resonances of a square or rectangular diaphragm. Some not very nice things were happening in that situation and though I know it is not the same as an ESL type drive with distributed drive over the membrane I would suspect that these same problems would rear their ugly heads. I often wonder why the frames have been rectangular on ESL speakers with no consideration to this phenomena, why there wasn't some large radius at least in the corners to alleviate some of the poor bending modes the diaphragm is forced to endure and the poor damping properties of the edge mounting of the diaphragm. It is not an easy problem to resolve or easy to understand some of the bending modes that are created across the frequency band.
I have been involved in a flat panel speaker development in the past and one issue that did crop up was the bending modes and resonances of a square or rectangular diaphragm. Some not very nice things were happening in that situation and though I know it is not the same as an ESL type drive with distributed drive over the membrane I would suspect that these same problems would rear their ugly heads. I often wonder why the frames have been rectangular on ESL speakers with no consideration to this phenomena, why there wasn't some large radius at least in the corners to alleviate some of the poor bending modes the diaphragm is forced to endure and the poor damping properties of the edge mounting of the diaphragm. It is not an easy problem to resolve or easy to understand some of the bending modes that are created across the frequency band.
Hi,
It is interesting. I have done a lot of experiments with my ESLs and currently the only identifiable modes seem to be at 75Hz(fundamental) and 140Hz(very reduced in level) as these do respond to external damping.
My impression is that very thin and light diaphragm can be quite effectively damped with things like low open area(<30%). Put a silk screen mesh with light cover cloth and the fundamental is just a few db above the level.
The measurements I posted before with bare membrane do not suggest resonance resonance modes in mid range and up. However to see a proper picture I would need to make the membrane same sized as a typical ESL and cover the frame with some felt to remove high frequency reflections.
Regards,
Lukas.
Last edited:
I recently performed a similar test to compare HF roll off for different diaphragm thicknesses.
Attachement shows experimental results match very well with theoretical roll off calculated based on radiation resistance(2*rho0*c) and diaphragm mass.
The -3dB point for Mylar diaphragms can be estimated by:
F(-3dB) = 93,400/t
where t = diaphragm thickness in µm.
Attachments
bolserst, I saved your graph for reference 
Do you know if the material of the diaphragm (soft, rigid) does matter? Same question for the dust covers. Also, how do you take into account the diaphragm and dust covers with different thickness together, that is three vibrating surfaces acoustically in series? Could they be modeled as one diaphragm having the combined thickness, i.e. sum of the three?
Do you know if the material of the diaphragm (soft, rigid) does matter? Same question for the dust covers. Also, how do you take into account the diaphragm and dust covers with different thickness together, that is three vibrating surfaces acoustically in series? Could they be modeled as one diaphragm having the combined thickness, i.e. sum of the three?
I'm not sure I understand your question. Do you mean high or low diaphragm tension? If so, then no, the tension does not affect the HF response and roll off. I guess you also migh be talking about the material strength of the diaphragm. The only property that determines the HF roll off is the mass. However, stronger/stiffer materials will have more pronounced higher order diaphragm resonance modes which could show up in the midrange if not properly damped.
If multiple diaphragms are driven together, as in a 3-stator 2-diaphragm arrangement like the woofer panels on the ML CLX, then combining the thicknesses for calculation of HF roll if will give you a good approximation. If only one of the diaphragms is driven, then things get more complicated as the air volume between the diaphragm and a dust cover acts like a compliance. Depending on the relative masses of the diaphragm/dust cover and the air volume compliance you can get different behaviors ranging from smooth roll off to resonance peaks of +3dB or more.
Hi!
This thread is a very interesting subject and also entertaining. Using glass make me remember an advertisement of about 45 years ago. I saw there a driver that you could use without any box or whatever! The best mounting for it was a glass panel the larger the better brick and concrete was useless . as it is acoustically dead I wonder did some of you had any experience or knowledge of them? It was apparently very good for background music. How it worked I do not know as they were too expensive for an apprentice to purchase just for inquisitiveness sake . I never heard or have seen any of them since. The same go for the poly planar speakers I read about in this thread. I did obtain one but I did go back to paper cones quickly as the sound was not that fantastic and they were brittle to handle. It did come cheap and I discovered soon why! For the glass microphone it seems to me as if this driver that worked on any stiff area would be just the thing. In the ad the other surfaces being metal etc.preferably
This thread is a very interesting subject and also entertaining. Using glass make me remember an advertisement of about 45 years ago. I saw there a driver that you could use without any box or whatever! The best mounting for it was a glass panel the larger the better brick and concrete was useless . as it is acoustically dead I wonder did some of you had any experience or knowledge of them? It was apparently very good for background music. How it worked I do not know as they were too expensive for an apprentice to purchase just for inquisitiveness sake . I never heard or have seen any of them since. The same go for the poly planar speakers I read about in this thread. I did obtain one but I did go back to paper cones quickly as the sound was not that fantastic and they were brittle to handle. It did come cheap and I discovered soon why! For the glass microphone it seems to me as if this driver that worked on any stiff area would be just the thing. In the ad the other surfaces being metal etc.preferably
Hi bolserst. Interesting measurements. I've currently made a 12 micron ESL and used the ESL_UI software (which you know well) to calculate segmentation resistors for a flat frequency response. Judging from your measurements, I need to equalize the high frequencies up to almost 9 dB with my diafragm thickness. Am I right? If so, I'd rather use different resistors to compensate for the diafragm roll off.
Thanks.
Response to this question was moved to the segmented wire stator thread.
http://www.diyaudio.com/forums/plan...r-esl-simulator-esl_seg_ui-7.html#post3540232
This however, is not the case for microphones, where response mostly depends on tension, esp. in true pressure transducers.
Best, M
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.