As noted by another poster, the links at AudioExpress no longer work.
Here are updated links, which I just tested :
http://audioxpress.com/files/kolbrek2884.pdf
http://audioxpress.com/files/kolbrek2885.pdf
If these links die, Google "An Introduction to Horn Theory" by Kolbrek
Here are the links
Kolbrek
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
Geddes
http://www.gedlee.com/downloads/horn theory reply.pdf
Regards,
WHG
Kolbrek
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
Geddes
http://www.gedlee.com/downloads/horn theory reply.pdf
Regards,
WHG
320Hz rect horn,1 inch throat, T=1/sqrt(2)
751.2354mm(W)
283.2894mm(H)
461.9914mm(D)
xyzfile
360*119=42840 points,
Hsieh W.M.
Attachments
On another tack...
Some years ago I did some work on duct noise. An engine intake pipe of around 400mm length and ~constant cross section was exciting a mode of the acoustic cavity of the air in the duct around 400Hz. The classic solutions were to add resonators or quarter wave tuners to counter the resonance, or to tune the pipe length so as to decouple the resonance from the exciting force in the operating region of interest.
The solution adopted was to drill 10 off 10mm holes in a ring around the duct and half way along the duct. This retained the DC flow practically unchanged and the resonance shifted to near double that without the holes: iy was like the duct was acoustically cut in half at these frequencies. I wonder if a similar action might apply to horns to manage the higher order modes? An extension of this might be to have a horn wall made like an absorbtive ceiling? I dont have a horn to mutilate, nor the skills to steer the software used to produce many of the plots in this thread, any volunteers?
Some years ago I did some work on duct noise. An engine intake pipe of around 400mm length and ~constant cross section was exciting a mode of the acoustic cavity of the air in the duct around 400Hz. The classic solutions were to add resonators or quarter wave tuners to counter the resonance, or to tune the pipe length so as to decouple the resonance from the exciting force in the operating region of interest.
The solution adopted was to drill 10 off 10mm holes in a ring around the duct and half way along the duct. This retained the DC flow practically unchanged and the resonance shifted to near double that without the holes: iy was like the duct was acoustically cut in half at these frequencies. I wonder if a similar action might apply to horns to manage the higher order modes? An extension of this might be to have a horn wall made like an absorbtive ceiling? I dont have a horn to mutilate, nor the skills to steer the software used to produce many of the plots in this thread, any volunteers?
@roflynn: what you describe applies to the fundamental mode of the duct, the lengthwise resonance. You effectively forced a pressure node at the middle of the duct that prevented the half-wave standing wave from forming.
In a horn, drilling holes, unless this is done close to the mouth, will effectively raise the cutoff of the horn. Olson, in the book Musical Engineering (1952) shows the effect of holes in tubes and horns as it applies to musical instruments, but similar things will happen in a loudspeaker horn.
In a JMLC horn, the lengthwise resonances are well damped due to the very good mouth termination these horns have.
The term Higher order modes, as usually applied to ducts, refers to standing waves across the duct/horn, and you can view HOMs as waves zigzagging through the horn. If you want to modify the HOMs, you would probably want to employ something that affects the HOMs more than it affects the axial propagation. Drilling holes in the horn walls will most likely rather introduce HOMs than reduce them, and at the same time do some damage to the axial propagation. Absorbing walls would be better. The idea of the Geddes foam plug is also to affect the HOMs more than the axial propagation.
-Bjørn
In a horn, drilling holes, unless this is done close to the mouth, will effectively raise the cutoff of the horn. Olson, in the book Musical Engineering (1952) shows the effect of holes in tubes and horns as it applies to musical instruments, but similar things will happen in a loudspeaker horn.
In a JMLC horn, the lengthwise resonances are well damped due to the very good mouth termination these horns have.
The term Higher order modes, as usually applied to ducts, refers to standing waves across the duct/horn, and you can view HOMs as waves zigzagging through the horn. If you want to modify the HOMs, you would probably want to employ something that affects the HOMs more than it affects the axial propagation. Drilling holes in the horn walls will most likely rather introduce HOMs than reduce them, and at the same time do some damage to the axial propagation. Absorbing walls would be better. The idea of the Geddes foam plug is also to affect the HOMs more than the axial propagation.
-Bjørn
Bjørn , Thanks for the explanation.
It took me some time to gain clarity about how modes might zig zag across a horn. The explanation was aided by a simulation animation showing a waves motion back down the horn after it reflects at the mouth - as shown in this thread at post 317 (about 6 years ago). I should read more.
It took me some time to gain clarity about how modes might zig zag across a horn. The explanation was aided by a simulation animation showing a waves motion back down the horn after it reflects at the mouth - as shown in this thread at post 317 (about 6 years ago). I should read more.
Room reflections?
I found the post about back reflections disturbing.
Could anyone suggest the ideal audio room dimensions for a roughly 1500 square foot audio room?
I would like to have the front of the room maybe 31 to 37 feet wide and expand possibly to 35 to 39 feet wide. I have thought perhaps 57 feet long to accommodate lower frequency waves.
I prefer round spherical horns. I am considering either the bass stand horn the full height of the room or perhaps a round 11 leaf style bass horn.
JMLC stated if the bass stand horn's frequency was crossed less than 50 Hz, the horn does not need to be physically timed aligned with the other drivers.
With this thought I would imagine building a round 50 Hz straight exponential/hyperbolic horn to time align physically with my other round horns would work. I could place them in front of the left and right large bass stand horn mouths.
Is there a way to simulate an audio room with these dimensions?
I know JMLC before he passed away suggested a bass stand horn. I'm concerned about parallel walls for the sides and ceiling as well as the back wall. That is why I thought the expanding walls would decrease standing waves, but am not so sure after seeing post 317 reposted.
I thought about having the front room start out 17 feet height and rise to 21 feet at the back of the room. Also thought about having a regular gabled ceiling so that there would be less parallel ceiling with the flat floor?
With the expanding walls, how would that work out with the bass stand horn?
PS I hope someone could help with the simulations before building an expensive room. [help=]%[/help]
I found the post about back reflections disturbing.
Could anyone suggest the ideal audio room dimensions for a roughly 1500 square foot audio room?
I would like to have the front of the room maybe 31 to 37 feet wide and expand possibly to 35 to 39 feet wide. I have thought perhaps 57 feet long to accommodate lower frequency waves.
I prefer round spherical horns. I am considering either the bass stand horn the full height of the room or perhaps a round 11 leaf style bass horn.
JMLC stated if the bass stand horn's frequency was crossed less than 50 Hz, the horn does not need to be physically timed aligned with the other drivers.
With this thought I would imagine building a round 50 Hz straight exponential/hyperbolic horn to time align physically with my other round horns would work. I could place them in front of the left and right large bass stand horn mouths.
Is there a way to simulate an audio room with these dimensions?
I know JMLC before he passed away suggested a bass stand horn. I'm concerned about parallel walls for the sides and ceiling as well as the back wall. That is why I thought the expanding walls would decrease standing waves, but am not so sure after seeing post 317 reposted.
I thought about having the front room start out 17 feet height and rise to 21 feet at the back of the room. Also thought about having a regular gabled ceiling so that there would be less parallel ceiling with the flat floor?
With the expanding walls, how would that work out with the bass stand horn?
PS I hope someone could help with the simulations before building an expensive room. [help=]%[/help]
This is what a bass stand horn is like.
http://www.diyaudio.com/forums/multi-way/175148-3-way-front-loaded-horn-help-2.html
http://www.diyaudio.com/forums/multi-way/175148-3-way-front-loaded-horn-help-2.html
BillWW,
If the room is considered with the mindset applied to the seakers themselves then perhaps the ideal shape might be like a Lecleach horn!
There is a lot about rooms on the Linkwitz site that might assist. He presents his preference for dipole radiation in those pages though the discussion on room characteristics presumably has broad application. The requirement for absorbtion at the back wall is consistent with the guidance of managing a reflected wave in a horn mouth.
Room Acoustics
About half way down on this page is shown guidance on room characteristics.
LX521 Description
As to simultion the software used for post 317 presumably might work?
If the room is considered with the mindset applied to the seakers themselves then perhaps the ideal shape might be like a Lecleach horn!
There is a lot about rooms on the Linkwitz site that might assist. He presents his preference for dipole radiation in those pages though the discussion on room characteristics presumably has broad application. The requirement for absorbtion at the back wall is consistent with the guidance of managing a reflected wave in a horn mouth.
Room Acoustics
About half way down on this page is shown guidance on room characteristics.
LX521 Description
As to simultion the software used for post 317 presumably might work?
Roflynn interesting links.
I'll have to study those in more detail.
Here is the famous Roggerro bass horn I'm interested in crossing down 50 Hz. My round horns I currently have when finished will be close to 9 feet tall. I want to add a 50 Hz round straight exponential/hyperbolic horn that will physically be time aligned and sit above my 9 foot tall line array of JMLC round horns. These horns will sit in front of the bass stand horn.
I'll have to study those in more detail.
Here is the famous Roggerro bass horn I'm interested in crossing down 50 Hz. My round horns I currently have when finished will be close to 9 feet tall. I want to add a 50 Hz round straight exponential/hyperbolic horn that will physically be time aligned and sit above my 9 foot tall line array of JMLC round horns. These horns will sit in front of the bass stand horn.