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  »  New  “Why horns”, years later...  Power-to-weight...  Horn-Loaded Speakers Forum     4  43960  09-26-2010
11-23-2012 Post does not mapped to Knowledge Tree
rowuk


Germany
Posts 440
Joined on 07-05-2012
Post #: 26
Post ID: 18766
Reply to: 18763
Explaining is not meant to be criticism
fiogf49gjkf0d
Paul,
I have been working with trumpets since 1966 and horn speakers since 1975. I have built both and am pretty familiar with what they are, the similarities and the differences.

If I had to pick THE major sin when thinking about all of the horns that I have ever heard, I think disregard for the lower cut off would be in first place. This also applies for most of the PA devices too. Most designers try and use the horn as low as it can go without regard for what happens to the sound when the horn no longer loads the driver in a reasonable way. If I think about the Klipsch LaScala, they pushed the midrange horn down to 400 Hz, that was an octave lower than it should have been, but the woofer sounded ratty up higher so it was less of a comprimise. I ended up with a much larger 200 Hz wooden radial horn that actually smoothed things out quite nicely. There was no real bass, but the rest was capable of very realistic reproduction of what I listened too back then, large orchestra and chamber music. The interesting thing was that big music sounded big and chamber music was intimate. Piano was phenomenally real, I was using a Quad II pre and poweramp and had a bunch of years of being able to come home after playing a symphony concert and not be disappointed. I built that radial horn several times, out of paper, pine, oak, cement, MDF, industrial ceramics and alternating layers of materials. At intimate room levels, there was no appreciable difference, but when cranking it up, the hardest materials had the least "artifacts" and seemed to keep the orchestral texture intact. A highly polished surface always presented the greatest amount of detail. In the following years I had exposure to quite a few metal horns but never was able to get the rest to work as I thought it should. I always imagined that there was some coloration although many of my musician friends thought they were fine.

Actually, horns behave reasonably predictably. Many of the awful PA combinations can be made reasonable by changing the crossover to one better suited to the horn. That also means that often a midrange driver has to be added as the woofers don't always go high enough. For little money though, acceptable results can be achieved.

For serious listening, the horn also is not that tough to manage because of its predictability. Currently I have a very small listening room and horn LF simply does not fit. I am experimenting with various 12" woofers and cabinets for everything under 800Hz. It is work in progress, but the horns are causing me no grief.

Whenever I feel blue, I start breathing again.
11-24-2012 Post does not mapped to Knowledge Tree
rowuk


Germany
Posts 440
Joined on 07-05-2012
Post #: 27
Post ID: 18767
Reply to: 18765
Audio Crap from acoustic instruments
fiogf49gjkf0d
Romy,
I could not agree more! The only reason that I mention it is because we do see enough speakers with exactly these acoustic instrument problems: energy that leaks through the horn material, ringing from undamped material, wrong cutoffs (a trumpet uses the "wrong" cut off to make it resonate).  I have found that the words to explain how musical instruments work are valuable to explain design mistakes for audio. I have experimented with glass, steel, wood, carbon fiber, lead and ceramic trumpet bells too.

One of the most important musical instrument discoveries for me was bracing. Here we solder or screw connectors from one part to another. The results are so profound and few artisans understand this. The bracing can transmit or damp vibration. String instruments also implement bracing in the form of a sound post ( http://www.violins.on.ca/luthier/soundpost.html ). I think that there could be some advantages to looking over the edge of the audio plate to find techniques perhaps useful for audio.

Thank you for the explanation on "Hairs and Hardening". It is very interesting to get the original context.

Whenever I feel blue, I start breathing again.
11-24-2012 Post does not mapped to Knowledge Tree
rowuk


Germany
Posts 440
Joined on 07-05-2012
Post #: 28
Post ID: 18768
Reply to: 18764
Absorption is not diffusion/diffraction
fiogf49gjkf0d
Hi BE,
we may not be in disagreement at all. Sandpaper finish is not necessarily absorptive. I was more referring to popular HOM-treating methods like foam or using softer materials to build or coat the horn.

I still have my doubts about how a rough surface can work as the grain is so much smaller than even a quarter wavelength of any frequency that would be reproduced and the "speed" of sound when it runs into a wall is ZERO unless the wall is conductive (absorptive/resonant) at that frequency. If this "grain" is a factor, then micro millimeter changes in the horn SHAPE (like with a coat of anything) will change things even more. Maybe the effect you notice is due to the horn being "slightly" smaller than before the coating? Granted, improvements in sound cannot always be explained as we do not have infinite knowledge of all of the parameters at work.

My doubts are based on my "primitive" understanding of how sound waves move. the acoustic generator "vibrates" and the air molecules next to it vibrate and bump into the next molecules that vibrate, and so forth. The air molecules in front of the driver do not travel to our ears. Also the acoustic "pressure" in a horn is different than physical pressure like filling up a balloon with air. So, what are the air molecules next to the rougher surface doing differently? The distribution of the density of the sound wave? I do not know. In any case, as Romy notices his effect at lower volumes, is this causing a non-linearity in the playback based on amplitude?

Whenever I feel blue, I start breathing again.
11-24-2012 Post does not mapped to Knowledge Tree
be
Copenhagen, Denmark
Posts 86
Joined on 02-12-2007
Post #: 29
Post ID: 18769
Reply to: 18768
I dont know how, but it works
fiogf49gjkf0d
Hi rowuk.

Shark skin decreases the formation of vortexes in fluid flows over surfaces and thereby reduces drag.
Shark skin resembles fine sand paper and has actually been used as such.
Of cource there is a difference between a stady flow around a shark and the forth and back movement of the air in a horn, but it could still make a difference, but how?
I certainly can hear a difference in the sound comming from the (well designed) horns where I tried it. It is noticeable in the high mids and up, where the sound seems to be cleaned up for a some noise and dirt.
At one stage I tried to cover the conical inner surface of the compression driver throat with sand paper on a very thin base, but with different grain sizes to find what worked best. The result was that corn size 200-400 was the best, using finer ones like corn size 1000 had less effect, the thickness of these papers where quite similar, but I did not check out the possible influence of this parameter. 
11-24-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,052
Joined on 05-28-2004
Post #: 30
Post ID: 18770
Reply to: 18769
Wow!
fiogf49gjkf0d
 be wrote:
Shark skin decreases the formation of vortexes in fluid flows over surfaces and thereby reduces drag.Shark skin resembles fine sand paper and has actually been used as such.
A phenomenal association!

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
11-25-2012 Post does not mapped to Knowledge Tree
rowuk


Germany
Posts 440
Joined on 07-05-2012
Post #: 31
Post ID: 18772
Reply to: 18769
The vortexes are additional out of band noise................
fiogf49gjkf0d
Hi Be,
the thread is about the "bad" reputation horns have with "audio" people. Applying liquid dynamics gives them more fuel for the fire, that is why I avoid using stuff that really doesn't apply. We have no real flow of air or "turbulence" in a horn (it is not a bass relex port.....). We have diffraction - especially when the contour has edges like with early CD designs or when the horn is of improper design or used in the wrong band. Earl Geddes also has written about the horn throat-compression driver transition and he uses clay to make it perfectly smooth. Without the clay, he claims to have measured additional audible HOM artifacts. In fact, he uses foam in the "waveguide" to correct for these HOM. This to me means that the horn in his case is not properly designed and that the sound "wants" to do something else much different than the horn thus creating artifacts. I think that there are horn shapes that have more "problems" than others. Clay is probably a great idea though to make sure that the horn/driver transition is free of a stepped contour. http://www.diyaudio.com/forums/gedlee/122318-diy-waveguide-loudspeaker-kit-112.html   post 1112

If foam or sandpaper help with a particular design, then I guess all that counts is what comes out of the front. I just have no explanation that fits with the physics that I have learned. That should never slow someone else down though. Again, if something the size of sandpaper grains makes such a big difference, then so does a coat of paint thick enough to hold the grains. Sandpaper regardless of how thin changes the dimensions of the mouth of a compression driver in a very big way - at one of the most sensitive parts of the whole system. That will change response strictly based on decreased size/volume. The binder for the grains (paint/glue) also "damps" the surface of the horn. This also could make a big difference - with or without sand.

I do not doubt that there is a "difference" in sound with any treatment that we apply to anything audio. Trumpets sound different when they are lacquered too (When they are gold or silver plated however, I have never noticed a difference). I have never added sand to the lacquer however. I will try this sometime.

Whenever I feel blue, I start breathing again.
11-25-2012 Post does not mapped to Knowledge Tree
be
Copenhagen, Denmark
Posts 86
Joined on 02-12-2007
Post #: 32
Post ID: 18773
Reply to: 18772
Out of textbook noise.
fiogf49gjkf0d

I have actually tried to roughen the surface of a glossy horn, witch did increase the horn size, and the effect was similar to painting it with a grainy paint, therefore I am sceptical your proposal that the heard effect was due to the dimmensional alteration.
If the dimmensional change where the cause, it is very unlikely that an increase and a decrease has the same effect.

It is true that that there can not be turbulence in a horn as seen by steady flows, yet the formation of turbulence is affected by surface roughness, hence surface roughness does affect the motion of fluids over the surface, therefore it can not be dissmissed that surface roughness can have an effect also in horns.
11-13-2013 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,052
Joined on 05-28-2004
Post #: 33
Post ID: 20262
Reply to: 11270
Some Brit’s take on the Horn sound....
fiogf49gjkf0d
http://www.hifiwigwam.com/showthread.php?95128-Horn-sound

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
Page 2 of 2 (33 items) Select Pages:  « 1 2
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  An Interview With Dr. Bruce Edgar..  An Interview With Dr. Bruce Edgar...  Horn-Loaded Speakers Forum     0  70251  07-10-2007
  »  New  Horn high-sensitively around Boston..  Horn high-sensitively around Boston...  Horn-Loaded Speakers Forum     0  15153  10-29-2008
  »  New  The most interesting horn ideas to me so far..  Looking for best horn values...  Horn-Loaded Speakers Forum     4  52041  04-30-2007
  »  New  The state of High-Efficiency Loudspeakers...  Tom Danley’s brilliant law...  Horn-Loaded Speakers Forum     6  87928  02-25-2009
  »  New  Some Horns propaganda..  Old paper direct-radiation tweeters...  Horn-Loaded Speakers Forum     4  88214  07-04-2004
  »  New  Some horn writing by Thomas Dunker. ..  Some horn writing by Thomas Dunker. ...  Horn-Loaded Speakers Forum     0  53567  01-14-2006
  »  New  Macondo's Axioms: Horn-loaded acoustic systems..  A link to another thread....  Horn-Loaded Speakers Forum     120  642119  07-29-2007
  »  New  “Why horns”, years later...  Power-to-weight...  Horn-Loaded Speakers Forum     4  43960  09-26-2010
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