Acoustic Horn Design – The Easy Way (Ath4)

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isitone, Very nice! did you turn it manually with some jig/template? I mean it is pretty accurate work, the measurements are really good.

May I ask how many hours of work went into it and how much experience is needed to achieve such piece? One of my relatives has suitable lathe but I don't have very high hopes turning one yet since I don't have experience and the owner is not into audio nor precision :D It could be nice if you gave a quick summary what it takes to turn such horn at home? Thanks!
 
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We need to see the impulse response to determine what the issue is. Measure at as low a level to the transducer that you can get away with, i.e. not so low that noise becomes an issue. Set mic gains etc. such that the signal that you get from the mic is nearly as large as possible. This might take some practice.

Do I do this from the same distance as before, which was about 1 meter from throat.
 
I don't want to talk about the types and models of the other brands. The picture shows a part of the selection, this must be enough information.
View attachment 953821

You've got lots of familiar horns there. I spot (2x?) B&C, RCF, SEOS, E-V / JBL-type diffraction horns (or R-H / Community clones) and the asymmetrical Limmer (021?).

I endorse your findings. While some smooth diffraction horns can sound really good when crossed high (the small RCFs, for example), I prefer a bigger horn without slot for crossover points around or below 1000 Hz.
 
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TNT, Image with thousand words :D

EQ is not relevant to see the waveguide "quality" behind the graph isitone posted. You can use any EQ and as much as you want with horn like this. Do a FIR filter with the listening axis signal and the response fixed on all axis (because the frequency response is mostly the same on all measured axis) which means there is no acoustical problems with the waveguide = as good as it gets. This particular waveguide however shows some narrowing around 1.5kHz which some of Marcel designs don't have. Still not nearly as much problems as most commercial horns available to purchase. Wanted to post it here since for example turk182 continuously questions "the quality", I thought maybe people don't understand what they are looking at in the graphs?
 

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TNT

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Sure :) I just wanted to understand if it was applied or not in this particular measurement. My view is still, except FIR et al., that the naturally smoother, the better i.e. I welcome local higher Q dips and peaks to be absent. Broader variations are none malign. I do understand that all angels follow EQ.

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Sure :D One more sentence for anybody still wondering what the heck. The dips and peaks that appear in all axis are problems of the driver, not the horn and can be EQ:d out. Use smooth driver and the response is smooth without EQ. If the lines were not tracking each other they would indicate acoustic problem in the horn which can't be fixed with EQ. Cheers :)
 
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... the cancellation of reflections at LFs which, when done, will allow for very accurate measurements in virtually any space.

I have been very interested in the theory of the Klippel Near Field Scanner ever since I became aware of it some time back.
You may remember we discussed this in the "DIY Klippel" thread.
What improvements will your work offer over the way the NFS does this?

Best wishes
David
 
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... My view is still, except FIR et al., that the naturally smoother, the better i.e. I welcome local higher Q dips and peaks to be absent. Broader variations are none malign. I do understand that all angels follow EQ.

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Remember this was a coaxial compression driver. This is about as good as it gets for that kind of device. The good thing is that there are no vertical lobes above the lower xover point - what you see is basically the complete behaviour of the loudspeaker in that band.
 
The dips and peaks that appear in all axis are problems of the driver, not the horn and can be EQ:d out. Use smooth driver and the response is smooth without EQ. If the lines were not tracking each other they would indicate acoustic problem in the horn which can't be fixed with EQ. Cheers :)

I don't believe that this is correct.

If there is a reflection at the mouth that causes a standing wave inside of the device, then these resonances will be as constant throughout the sound field as a resonance in the driver itself.