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Reduce mouth resonance in horn
Reduce mouth resonance in horn
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Old 12th December 2018, 01:01 PM   #21
Ivo is offline Ivo  Netherlands
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Originally Posted by cowanaudio View Post
If the horn is going to be infinite, just give it a 10Hz flair rate. There, no subwoofer required. It would actually be smaller than the infinite 100Hz horn too!
Eh... What does infinite mean? I know the option in Hornresp, but have not understood what type of loading that means.
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Old 12th December 2018, 02:49 PM   #22
xrk971 is offline xrk971  United States
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Reduce mouth resonance in horn
Quote:
Originally Posted by Soldermizer View Post
I was lying in bed last night and it occurred to me: the stub/Helmholtz won't solve our problem! Yes, it would be good to reduce (say) a 1000 Hz peak. But the mouth reflection issue is one of delay (time) of the entire signal leaving the horn. Per Bouska and others, the distortion is a low-passed and multiply time delayed alternately inverted/not inverted delay of the signal.
One of the most popular ways of dealing with the mouth impedance discontinuity reflections is to put the driver about 1/3 from the closed end of the horn - in effect, forming a stub to help cancel the big first reflection peak. So, it still works and works down to low frequencies even, not just kHz (which is a tiny distance).
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Old 13th December 2018, 06:47 AM   #23
David McBean is offline David McBean  Australia
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Quote:
Originally Posted by cowanaudio View Post
If the horn is going to be infinite, just give it a 10Hz flair rate.
Hi William,

That is a great idea, but why settle for just 10Hz?

Let's pull out all the stops, and make it a 1Hz flare cutoff infinite exponential horn - ruler flat down to 5Hz... :-).

Kind regards,

David
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Old 13th December 2018, 07:24 AM   #24
David McBean is offline David McBean  Australia
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Originally Posted by Ivo View Post
Eh... What does infinite mean? I know the option in Hornresp, but have not understood what type of loading that means.
As the word suggests, infinite means that the horn is infinite in size :-). It is a theoretical concept only - you cannot actually build one physically. Infinite horns are usually the starting point for any discussion on acoustic horns in the standard reference textbooks because they have simpler mathematical models than those of finite horns, and can give reasonably useful indicative results in simulations. This aspect is somewhat less important these days though, because computing power is now such that finite horns can be simulated almost as easily and as quickly as infinite horns.

The attachment compares the throat impedance of an infinite 100Hz exponential horn to that of a relatively large finite 100Hz exponential horn. As the horn length and mouth size are increased while maintaining the same flare rate, the ripples reduce in amplitude, disappearing completely in the limiting case of an infinite horn.
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Old 13th December 2018, 08:37 AM   #25
cowanaudio is offline cowanaudio  Australia
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Reduce mouth resonance in horn
Quote:
Originally Posted by Ivo View Post
Eh... What does infinite mean? I know the option in Hornresp, but have not understood what type of loading that means.
It's a thought exercise. Positive and negative infinity are used in mathematics to establish one or both ends of a continuum. All horns are compromised and being able to see what an infinite horn looks like demonstrates the magnitude of the compromise. It's an interesting feature but not one I've used often. I've never attempted to build one
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Old 13th December 2018, 12:37 PM   #26
Soldermizer is offline Soldermizer  United States
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This is getting too confusing. I am just going to stick 30 PPI foam in my ear canals* and be done with it


*I can see the future debate raging on "Tweaks" on Audio Asylum: "Is natural or paraffin better to hold in your foam ear plugs?"
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Old 15th December 2018, 12:39 PM   #27
Soldermizer is offline Soldermizer  United States
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Since this thread has perished faster than resonances in a treated Geddes waveguide I thought I would post a helpful hint. Of cheap tweaks I've discovered, only the towel tweak seems to be effective. Yet it suffers from poor appearance. Here, then, is a substitute that is much more elegant. Too, it should win acceptance from the spouse, at least during the holidays.
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“[G]enes are predicting that sweet taste in the mouth, and orgasm, are going to be ‘good’ in the sense that eating sugar and copulating are likely to be beneficial to gene survival. The possibilities of saccharine and masturbation are not anticipated…” Richard Dawkins, The Selfish Gene
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Old 15th December 2018, 06:01 PM   #28
Ivo is offline Ivo  Netherlands
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Quote:
Originally Posted by David McBean View Post
As the word suggests, infinite means that the horn is infinite in size :-). It is a theoretical concept only - you cannot actually build one physically.
Quote:
Originally Posted by cowanaudio View Post
It's a thought exercise. Positive and negative infinity are used in mathematics to establish one or both ends of a continuum. All horns are compromised and being able to see what an infinite horn looks like demonstrates the magnitude of the compromise. It's an interesting feature but not one I've used often. I've never attempted to build one
Thank you, gentlemen!
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Old 16th December 2018, 01:56 PM   #29
tapestryofsound is offline tapestryofsound  Scotland
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Originally Posted by Soldermizer View Post
Since this thread has perished faster than resonances in a treated Geddes waveguide I thought I would post a helpful hint. Of cheap tweaks I've discovered, only the towel tweak seems to be effective. Yet it suffers from poor appearance. Here, then, is a substitute that is much more elegant. Too, it should win acceptance from the spouse, at least during the holidays.
Ho-ho-ho! ......... Try sandpaper.

Shape pieces of say, 400 grit wet and dry sandpaper to fit around the lips of the mouth, using double sided adhesive tape.

I am very interested in the idea that turbulence created in the throat and amplified by the horn, can be attenuated (or ameliorated) by a textured surface. I am thinking a lot about this to factor in for my next build.

If needs be, you can always remove the sandpaper by running a drop of naphtha (zippo type lighter fuel) along the edges of the sandpaper, leave for a minute, and it should lift off without much sticky residue left behind.

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Old 16th December 2018, 05:23 PM   #30
CraigSu is offline CraigSu  United States
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Tapestryofsound mentioned “plumbers pipe lagging” in an earlier post and I agree it’s certainly worth the try as it’s inexpensive. For us Americans that translates to foam pipe insulation (https://www.lowes.com/pd/Frost-King-...723ffebce43bf2) which any hardware or big box store will carry.
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