The klippel NFS seems to do a relatively dense sampling of the pressure field over a cylindrical/spherical surfce. This fascinating thread has very well written documentation of more details about this:
https://www.audiosciencereview.com/...ner-the-mathematics-and-everything-else.9970/
It also seems to use a hybrid method where the spherical harmonics based pressure field reconstruction is used for the relatively lower frequencies and gated measurements used for the higher frequencies.
Details on the sound field separation to separate the reflections from the intended measurements are also given in above link.. 🙂
https://www.audiosciencereview.com/...ner-the-mathematics-and-everything-else.9970/
It also seems to use a hybrid method where the spherical harmonics based pressure field reconstruction is used for the relatively lower frequencies and gated measurements used for the higher frequencies.
Details on the sound field separation to separate the reflections from the intended measurements are also given in above link.. 🙂
The problem is the robotics needed to sample the points at the right place to make it work. There is no short cutting it I have discussed it with NTK as I hoped a simplified version could be found but Soundfield separation needs a measurement rig pretty much like the NFS has to function. There are other approaches that can do a similar thing to the other stages the NFS uses. So far there is no working version of those in the public domain.
I had my output and ref output set incorrectly. That somehow created an artifical gating around 4ms. 🤫
I did some prelimary measurements with the SM57 mic, just to get used to the new measurement process and the use of it in VituixCAD.
The measurements are very repeatable and the weird preringing that happened every now and then is gone. I do get weird measurements when the speaker is turned towards the wall and I guess the reflected signal gets stronger than the direct sound. That problem will go away when I do the measurements in the barn.
In VituixCAD I get nice directivity graphs for a crossover frequency from ~700Hz to ~1000Hz. It seems very forgiving. I didn't pay attention to the FR flatness as the SM57 doesn't have a flat response.
But when I enter a 400mm offset between the woofer and the waveguide, I can't get the directivity smooth.
Is there a magic knob I can turn to improve this? I've tried all kinds of parameters in VituixCAD, but I didn't succeed.
Any other remarks?
The measurements are very repeatable and the weird preringing that happened every now and then is gone. I do get weird measurements when the speaker is turned towards the wall and I guess the reflected signal gets stronger than the direct sound. That problem will go away when I do the measurements in the barn.
In VituixCAD I get nice directivity graphs for a crossover frequency from ~700Hz to ~1000Hz. It seems very forgiving. I didn't pay attention to the FR flatness as the SM57 doesn't have a flat response.
But when I enter a 400mm offset between the woofer and the waveguide, I can't get the directivity smooth.
Is there a magic knob I can turn to improve this? I've tried all kinds of parameters in VituixCAD, but I didn't succeed.
Any other remarks?
Hard to answer on a theoretical level. You could share your VCad project with measurement data.
I cannot see any proper bass response, you have not merged nearfield with far field data yet, correct?
I cannot see any proper bass response, you have not merged nearfield with far field data yet, correct?
I will. Will take some time. Keep in mind the data isn't perfect. I hope it is good enough.
Correct.
This thread might help you to understand the inherent problem
https://www.audiosciencereview.com/...lter-effects-on-the-vertical-radiation.23239/
iIRC Boxsim has the same way of defining the coordinates (be it they use a,b and c). So this is a particular thing about loudspeaker simulation apps I guess.
Hi very interesting thanks Why not test the driver mounted on a open baffle ? if i understand well the enclosure has always an impact on the driver response
I guess that data sheet are measured with the driver on a panel ?
Usually I ask the 'why' questions 🙂
The enclosure has an impact. I want the response of the driver in the enclosure.
I don't know how the data sheets are measured. "Assumptions are the mother of all ......" (my favorite quote 🙂 )
I kinda moved on, but I realise I have some loose ends.
The enclosure has an impact. I want the response of the driver in the enclosure.
I don't know how the data sheets are measured. "Assumptions are the mother of all ......" (my favorite quote 🙂 )
I kinda moved on, but I realise I have some loose ends.
Usually they are on an IEC baffle at a specified distance, but sometimes they are in a reflex box or anything else the manufacturer thinks will make the response look better. So you are right not to assume.
Measuring the driver in the enclosure you plan to use it in is exactly the right way to do it when designing a speaker.
Small update:
I've been looking into cepstrum analysis to try to get rid of echoes. I don't really understand what is the key point about them, but have tried and read enough that I'm not persuing that anymore. Not successful.
I thought it would be nice to have a small test amplifier for testing. I read the Aiyima A07 was good bang for the buck. The are indeed not expensive so I bought two, hoping that they might be good enough. However, they are quite noisy, at least with the high efficiency CD's. With a bit of volume I don't hear it anymore, but it is a bit of a disappointment. The noise is not really dependent on volume (up to a point), so maybe an l-pad could help as the CD is about 9dB more sensitive than the woofer.
I've also been listening to music. Easy listening music is very nice, including trance stuff. It's a polite speaker; it doesn't kick you in the butt. It seems to struggle with Wall-of-sound music. I don't have any reference/experience to say much more about it.
In the past I bought a Topping D10s and I recall that it sounded much better than either my laptop output or the behringer UMC 204HD (I think it was the latter). I'm not a trained listener, if I hear it, the change has to be really obvious. Could I use two separate dacs, one for each speaker? And use something like EqualizerApo for the dsp (on the computer)? Or is there some e.g. some time problem with two separate dacs?
I'm preparing for another round of (heat) insulation, that takes up quite some time.
I've been looking into cepstrum analysis to try to get rid of echoes. I don't really understand what is the key point about them, but have tried and read enough that I'm not persuing that anymore. Not successful.
I thought it would be nice to have a small test amplifier for testing. I read the Aiyima A07 was good bang for the buck. The are indeed not expensive so I bought two, hoping that they might be good enough. However, they are quite noisy, at least with the high efficiency CD's. With a bit of volume I don't hear it anymore, but it is a bit of a disappointment. The noise is not really dependent on volume (up to a point), so maybe an l-pad could help as the CD is about 9dB more sensitive than the woofer.
I've also been listening to music. Easy listening music is very nice, including trance stuff. It's a polite speaker; it doesn't kick you in the butt. It seems to struggle with Wall-of-sound music. I don't have any reference/experience to say much more about it.
In the past I bought a Topping D10s and I recall that it sounded much better than either my laptop output or the behringer UMC 204HD (I think it was the latter). I'm not a trained listener, if I hear it, the change has to be really obvious. Could I use two separate dacs, one for each speaker? And use something like EqualizerApo for the dsp (on the computer)? Or is there some e.g. some time problem with two separate dacs?
I'm preparing for another round of (heat) insulation, that takes up quite some time.
Without a way to synchronize the clocks together the separate DAC's will drift apart over time which can present issues. Whether this ends up being a deal breaker in a Left and Right split is hard to know without trying.
The magical word of course being ‘external sync’. If the DACs have that option, there should not be a drifting problem.
It's been some time...
I haven't been able to spend much time on the speakers due to various reasons. I did have some time to listen to it. I compared it to my ELAC Debut 2 shelf speakers and that has much more bass. I guess I could use the dsp to improve this.
I friend of mine bought a nice pair of speakers and I was invited to go with him and listen to several speakers. It was my first experience listening to great speakers with a switcher to listen to them without a delay. Great experience. It took me some time to hear a difference, but once you've noticed something it hard to un-notice.
I have been listening with an Aiyima A07 per speaker. The compression drivers are very efficient, which results in quite audible noise. The noise is not really dependent on the volume level. I just bought a Topping PA5 II for its low noise. It's much quieter; especially the TRS input. That noise is dependent on the volume. Would an L-pad on the CD help in reducing the noise further? I should be able deduce that myself, but I'm too tired right now....
I have to finish my isolation work soon to get my subsidy. That would mean that I might get some time for some speaker testing again.
Any remarks are welcome.
I haven't been able to spend much time on the speakers due to various reasons. I did have some time to listen to it. I compared it to my ELAC Debut 2 shelf speakers and that has much more bass. I guess I could use the dsp to improve this.
I friend of mine bought a nice pair of speakers and I was invited to go with him and listen to several speakers. It was my first experience listening to great speakers with a switcher to listen to them without a delay. Great experience. It took me some time to hear a difference, but once you've noticed something it hard to un-notice.
I have been listening with an Aiyima A07 per speaker. The compression drivers are very efficient, which results in quite audible noise. The noise is not really dependent on the volume level. I just bought a Topping PA5 II for its low noise. It's much quieter; especially the TRS input. That noise is dependent on the volume. Would an L-pad on the CD help in reducing the noise further? I should be able deduce that myself, but I'm too tired right now....
I have to finish my isolation work soon to get my subsidy. That would mean that I might get some time for some speaker testing again.
Any remarks are welcome.
I think that raising the reference level on the input of the Topping could help. A pad on the CD sure works.
Good work so far.
I'm currently working on supravox 165gmf + faitalpro hf108(16ohm) + rcf hf101.
The crossover point is 1.6k.
The box is 17liter, bass reflex.
measurement taking : 30cm between tweeter and woofer.
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