Hi Dan,
In effect, yes.
System efficiency, sound pressure and particle velocity are now calculated at the same time as the other results - it is no longer necessary for the chart to be displayed to generate the results.
Kind regards,
David
Hi sannax,
Y is the radius in mm.
This can be readily confirmed by checking that Y at X = 0 is equal to Sqrt(S1 / Pi).
To make things a bit clearer I will change the column headings from X and Y to Length and Radius in the next release. This will then also make them consistent with the headings used for the other two Le Cléac'h horn schematic diagram export options.
Thanks for asking the question.
Kind regards,
David
Does anyone have any advice on folding up a midbass horn? The horn I created in your software is too big for my living room as a straight horn. I'm trying to figure out how to take this straight horn and make it into a La Scala type of horn. The problem I'm having is where to cut the flare such that the cut part fits into the width of the mouth of the horn. See here:
http://www.diyaudio.com/forums/multi-way/198644-folding-midbass-horn.html#post2748759
for more details.
http://www.diyaudio.com/forums/multi-way/198644-folding-midbass-horn.html#post2748759
for more details.
Is 1/4 wavelength the standard for determining "tightly coupled" in terms of 1/4 space, 1/2 space, etc? In other words, if the mouth of the horn is within 1/4 wavelength of any flat surface, then that surface "counts" as long as it's strong and basically air tight? So, if the mouth of a horn is within 1/4 wavelength of the wall of a room, and the horn is sitting on the floor, then that horn is radiating into 1/4 space?
Hi dirkwright,
For what it's worth - Hornresp assumes that there is no air gap at all between horn mouth and the surface(s) defining the solid angle 'Ang' into which the horn radiates.
Any opening will compromise the theoretical design to some degree. 1/4 wavelength seems rather large to me - I am not sure that it would be considered to be "small compared to a wavelength", which is the (somewhat ambiguous) requirement normally specified.
Kind regards,
David
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OK, now I understand why you and others recommend that horns for free standing domestic use be no smaller than 1/2 space size. I don't think all horn designers feel this way however. I'm not sure myself.
Dirk,
I think what you have stated only applies to upper bass, mid and treble horns.
When it comes to low bass horns, I firmly believe that almost everyone accepts that to give acceptable domestic size and domestic performance, that quarter space and eighth space loadings become necessary.
Taking McBean's statement
I'm pretty sure most big, low bass horns can be placed within 300mm of two boundaries to achieve quarter space loading. If the walls and floor are stiff enough.
I think what you have stated only applies to upper bass, mid and treble horns.
When it comes to low bass horns, I firmly believe that almost everyone accepts that to give acceptable domestic size and domestic performance, that quarter space and eighth space loadings become necessary.
Taking McBean's statement
and applying 1/10 wavelength to a lower bass horn going up to 100Hz then the maximum gap becomes ~ 300mm.
I'm pretty sure most big, low bass horns can be placed within 300mm of two boundaries to achieve quarter space loading. If the walls and floor are stiff enough.
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Also, I forgot to ask if the 1/4 wavelength refers to the lower or higher frequency limit of the horn? For almost all freestanding bass or midbass horns, the lower frequencies would be in the 1/4 wavelength distance from mouth to solid surfaces, but that obviously changes as the frequencies reproduced by the horn are increased. There must be a transition point when the wavelengths become shorter than the distance but I don't know what happens above that point. Does the horn become more directional at higher frequencies and thus doesn't need the other surfaces, or does it continue to need those other surfaces in order to function properly (i.e. have consistent SPL output). What determines the directivity of a horn, and the transition from omnidirectional to directional radiation patterns?
It applies at all frequencies you are interested in. The highest frequency would set the minimum distance.
It depends on your design, but if the horn becomes acoustically large enough to have directivity, then it probably doesn't need the other surfaces anymore.
The size of the horn, angle of the walls, and the frequency the horn is producing.
Thanks for your reply. I'm learning about this very fast.
So, if the horn has an upper cutoff of 500 Hz, and the wavelength of that sound wave is 27 inches, then you're saying that the mouth of the horn has to be within 1/4 of that (about 7 inches) to any solid continuous surface included in the Pi space calculation for the horn? In other words, if I design the horn for 1/4 size space, then the two perpendicular surfaces have to be within 7 inches of the mouth in order for the horn to function as designed, is that correct? If so, this is a lot harder than I realized, and basically impossible without reconstructing the walls in the listening room.
I'm working on a midbass horn for 100-500 Hz. It is too large when designed for 1/2 size space as a straight horn (1 meter deep x 74cm square, not including the rear chamber). It is far more reasonable in size if I go to 1/4 space and fold it up (like a La Scala type), but I'm hearing from you all that even then the mouth will not be close enough to the wall to function at 500 Hz. There will be a transition at about 150 Hz if the folded up horn is about 65 cm deep. What happens at the transition? Does the SPL output go way down?
I don’t understand the 150 Hz “transition” you are referring to.
Half space, 1/4 and 1/8 space increase sensitivity because they limit the angle of radiation possible.
A “small mouth” bass horn has little directivity down low, the LF waves diffract around the mouth perimeter, so LF on axis sensitivity increases with the addition of boundaries. At high frequencies, the same horn has directivity, if the directivity is greater (a smaller angle) than the wall boundary, the walls have virtually no effect on sensitivity.
At 500 Hz, the mouth size of your horn will be relatively large compared to a wavelength, as John Sheerin said “if the horn becomes acoustically large enough to have directivity, then it probably doesn't need the other surfaces anymore.”
The La Scala bass horn design does not depend on the side walls of your house for reinforcement of the upper frequencies, though corner placement will increase the low end response of that type of enclosure, just as it would any low frequency driver.
To truly use wall boundaries as part of the horn, the horn needs to be designed as such.
Also in the “a lot harder than I realized” category, parallel horn walls become a big deal when they approach a wavelength, remember Hornresp assumes a circular horn mouth.
Using parallel walls with expansion on a LF “sub” horn makes little difference in the intended pass band, but results in ragged response up in the mid range.
Art Welter
740mm is not big. That fits well in 4Pi loading, no nearby reflecting surfaces and no reliance of reflecting surface stiffness.
A question: Can a 500Hz horn be folded and still perform well up to that frequency?
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I have been here before, but if McBean says that, then where does 7" fit with his opinion?
If you have a horn that is about 65 cm deep and put it on the floor backed up against a wall, the 1/4 wave frequency from the mouth to the wall is about 130 Hz (65 cm x4 = 260 cm, the wavelength of 130 Hz). So, as I'm trying to figure out how this stuff works, I thought that the horn would "see" the wall at frequencies below 130 Hz, and then the wall would be invisible above that frequency. So, if that's the case then I was wondering what would happen if the horn was becoming directive (less than omnidirectional radiation pattern) at some higher frequency than 130 Hz. I don't even know how to figure out the directivity with frequency for a horn without Hornresp. I've used the wavefront simulator in Hornresp to investigate how these things behave with various walls, but I don't know if the simulation is accurate. Hornresp doesn't simulate folded rectangular horns either, so I don't know what happens with that.
Well, I think it's the length of over 1 meter that concerns me the most.
I wanted to do a La Scala style because it only has 2 turns in it, which possibly means that more high frequencies get through the horn than one with more turns. Each turn is a low pass acoustical filter, for sure, so this is a serious concern.