Cool! Please post if you find it. I would be nice to know what it looks like alone and also alone with HP filter.
Jean-Michel was saying that it's crossed too low, which I found hard to believe, until I looked at the specs. OK! That's a small horn. And 18Sound rate it from 2.5K up. Hmmmm.........
Is it easy to import any impulse into it. What type of impulse file will it import?
I would love to see what my horn currently does.
Hello,
Been playing with Octave tonight, and so I decided to measure the horn again
I tried various HP filters to see their effect on group delay. The horn is 18sound XD125 and it's mounted on a 40cm width baffle. Measurement distance is 1m, and orientation is on axis.
The cases are:
1) 1st order at 500Hz (for protection)
2) 2nd order LR at 2kHz
3) 4nd order LR at 2kHz
4) 8nd order LR at 2kHz
First here's the windowed FFT freq responses:
- Elias
Been playing with Octave tonight, and so I decided to measure the horn again
I tried various HP filters to see their effect on group delay. The horn is 18sound XD125 and it's mounted on a 40cm width baffle. Measurement distance is 1m, and orientation is on axis.The cases are:
1) 1st order at 500Hz (for protection)
2) 2nd order LR at 2kHz
3) 4nd order LR at 2kHz
4) 8nd order LR at 2kHz
First here's the windowed FFT freq responses:
- Elias
Attachments
Maybe the difference it better seen from the group delay:
Indeed the LR12 does not add almost anything to the group delay of the horn itself. Then LR24 almost doubles the delay at 2kHz. Obviously LR48 has huge delay.
Now the question is how does this relate to Horn Honk?
What is interesting about the group delay of this horn is the fact that it's never constant but has rising slope all the time! No phase linear system possible with this horn
- Elias
Indeed the LR12 does not add almost anything to the group delay of the horn itself. Then LR24 almost doubles the delay at 2kHz. Obviously LR48 has huge delay.
Now the question is how does this relate to Horn Honk?
What is interesting about the group delay of this horn is the fact that it's never constant but has rising slope all the time! No phase linear system possible with this horn
- Elias
Attachments
Hello,
The easyness depends on who you ask from, I suppose. Octave being general purpose mathematics tool it will eat any binary, or ascii, or WAV file for example, but you need to know the file format and write your own code to analyse it. Certainly there is no "wavelet transform for impulse response" button to press.
However, if you're into hard core DIY then it might be a program for you
- Elias
The easyness depends on who you ask from, I suppose. Octave being general purpose mathematics tool it will eat any binary, or ascii, or WAV file for example, but you need to know the file format and write your own code to analyse it. Certainly there is no "wavelet transform for impulse response" button to press.
However, if you're into hard core DIY then it might be a program for you
- Elias
Hello Elias
I really do like "pretty pictures" – but to be honest, I'm not familiar with that form of visualisation.
I understand that the vertical axis shift tells us about "point of origin" in a time scale for different frequencies (obvious at first of your plots) ?
But what actually tells us different width of that "Christmas tree" (obvious at second of your plots)?
Michael
I really do like "pretty pictures" – but to be honest, I'm not familiar with that form of visualisation.
I understand that the vertical axis shift tells us about "point of origin" in a time scale for different frequencies (obvious at first of your plots) ?
But what actually tells us different width of that "Christmas tree" (obvious at second of your plots)?
Michael
Hello Michael,
I think wavelets are very handy in showing the effects which are hiding from FFT and CSD waterfall for example. Because it maximises the resolution in the frequency domain and in the time domain at the same time.
And it's very fun also As DIY should be
The interpretation is not difficult The "christmas tree" shape comes from the fact that the wavelet contains a fixed number of cycles at each frequency. Thus the time domain width gets smaller as the freq increases.
Here's a pic of two set of wavelet transforms on the right first having 3 cycles and another having 5 cycles wavelets. The colors indicate the magnitude of the envelope in dB scale. And on the left their time domain waveforms with the envelope at the lowest frequency. This is the ideal case (the response of a PC sound card).
Hope it helps
- Elias
I think wavelets are very handy in showing the effects which are hiding from FFT and CSD waterfall for example. Because it maximises the resolution in the frequency domain and in the time domain at the same time.
And it's very fun also
As DIY should be The interpretation is not difficult
The "christmas tree" shape comes from the fact that the wavelet contains a fixed number of cycles at each frequency. Thus the time domain width gets smaller as the freq increases. Here's a pic of two set of wavelet transforms on the right first having 3 cycles and another having 5 cycles wavelets. The colors indicate the magnitude of the envelope in dB scale. And on the left their time domain waveforms with the envelope at the lowest frequency. This is the ideal case (the response of a PC sound card).
Hope it helps
- Elias
Attachments
Back to the quest on Horn Honk!
Interesting things come at display when increasing dynamic range of the wavelet tranform results. Here looking at the 40dB scale. Again the same 18sound XD125 horn now measured at 50cm distance on axis.
Here's a 5 cycle transform. There is a lot of garbage on the right hand side with this horn! Compare this to the sound card response above.
Notice the first room reflection comes at 5ms (ignore that).
- Elias
Interesting things come at display when increasing dynamic range of the wavelet tranform results. Here looking at the 40dB scale. Again the same 18sound XD125 horn now measured at 50cm distance on axis.
Here's a 5 cycle transform. There is a lot of garbage on the right hand side with this horn! Compare this to the sound card response above.
Notice the first room reflection comes at 5ms (ignore that).
- Elias
Attachments
If we trade some of the frequency domain resolution into time domain resolution and select 3 cycle wavelet, we can see there are multiple consecutive reflections/diffractions at the high frequencies (see above 3kHz for example). Maybe even HOM???
Now, does this horn honk?
I don't know. But when my friend listened this horn at the first time he said "it sounds like a horn". Whatever that means??
Unfortunately I don't have a worse horn than this to explore more. I'm more into dipoles actually
Anyway I think what we need is measurements of a horn that has guaranteed honk! Then we can see how does it look like??
- Elias
Now, does this horn honk?
I don't know. But when my friend listened this horn at the first time he said "it sounds like a horn". Whatever that means??
Unfortunately I don't have a worse horn than this to explore more. I'm more into dipoles actually
Anyway I think what we need is measurements of a horn that has guaranteed honk! Then we can see how does it look like??
- Elias
Attachments
Hello Panomaniac
What conditions?? If you look at what Altec does with them they cross them over at 800Hz and 1200Hz so at least a half octave above their cut-off. Are they OK at reasonable levels and then have issues loud or is there always something there?? I have never had a pair of either at home to play with. Did you have them damped with clay?? Does the 511 ring more than the 811??
Rob
I thought the reason not to own one was obvious. Why would I want to pay for honk in my home? However, there were some good qualities such that I am trying to design one that hopefully will not honk. Still not quite there.You are listening to the wrong horns if that's the case. Which ones do you own or have owned that honked??
Rob
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Elias that wavelet seems to be a great tool in visualizing *exactly* what we are after here. We see the shift in "virtual acoustic origin" form group delay AND we see the prolongation in decay as well as mouth reflections later on - all in a very intuitively graspable form.
I actually would have asked why we can't see the quarter wave / transmission line reflections of the horn you measured - but you were even faster in that conclusions and already have shown.
Great job!
Would love to see a handy interface to usual measurement software like ARTA, SoundEasy, AudioTester or HolmImpulse - will shoot the programmers a email request if they possibly could integrate such a visualisation....
Until we get it for the "dummies" couldn't you sort of repeat the towel trick of Jack Bouska - or at least show a simple straight horn of low included angle with no round over whatsoever ? - "card board quality" would do easily for the purpose
This immediately would give us a "feeling" what those mouth reflections look like with that visualization tool.
Again thanks for bringing this up, Elias, very much appreciated!
Michael
I actually would have asked why we can't see the quarter wave / transmission line reflections of the horn you measured - but you were even faster in that conclusions and already have shown.
Great job!
Would love to see a handy interface to usual measurement software like ARTA, SoundEasy, AudioTester or HolmImpulse - will shoot the programmers a email request if they possibly could integrate such a visualisation....
Until we get it for the "dummies" couldn't you sort of repeat the towel trick of Jack Bouska - or at least show a simple straight horn of low included angle with no round over whatsoever ? - "card board quality" would do easily for the purpose
This immediately would give us a "feeling" what those mouth reflections look like with that visualization tool.
Again thanks for bringing this up, Elias, very much appreciated!
Michael
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LOL Ok you do have a point. But you can learn alot taking one that does and seeing what you need to do to make it not honk. So it sounds like you have not had too many horns at home. I have had several and Earl certainly has a point that HOM's seem to be level dependent if that is indeed the reason or a contribitor to that "sound". Some sound fine until you push them SPL wise. Some are good over a limited bandwidth, some are good at any SPL but they are a rare breed. So you can limit bandwidth and SPL to help make honkers more liveable. Some need no help at all.
Rob
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