Hi Gorge,
I'm going to find your SoundEasy software to simulate speakers. Maybe I can mantain 1/4 wavelenght 🙂
Hi Geoff
to calculate horn expansion I used the software from Single Driver Website. But I'd try the one you mentioned, thanks.
What I've not clear is if I can cut the mouth area as calculated by the software, but mantaining one side of the mouth 1/4 wavelenght of cut off frequency.
I'm going to find your SoundEasy software to simulate speakers. Maybe I can mantain 1/4 wavelenght 🙂
Hi Geoff
to calculate horn expansion I used the software from Single Driver Website. But I'd try the one you mentioned, thanks.
What I've not clear is if I can cut the mouth area as calculated by the software, but mantaining one side of the mouth 1/4 wavelenght of cut off frequency.
thomaseliot said:
PartsExpress has it on sale now. Lots of peculiar ways of using it so it takes some time to get used to. I'm still trying to figure things out after a long time. The manuals are on line, so you can read while you're waiting for it. Also you can see if it does what you want first. I have not used the box design part extensively.
I think you might want to consider having it smaller but placing it at specific locations to extend the response using room modes.
Geoff, I would be interested in a copy too. Thanks!.
Hi
I might be wrong about this. The 1/4 wavelenght at one side of the mouth of a full scale is not the full story. The formula for a fullscale round horn is: 2*PI*r = 1/1 Wavelenght. So the horn will have a circumference of the wavelengt. This is not the same as saying that the horn has to have an opening of 1/4 wavelenght !
For a square fullscale horn you calculate the
Mouth Area = (1/4*Pi)*(speedofsound/Fo)^2
A one-eight size horn
Mouth Area = (1/32*Pi)*(speedofsound/Fo)^2
Have you read "the show horn" Bruce Edgar ? There is also an M factor for the hyperbolic-exponential calculation, don't know if these calculation still is up to date...
Best regards
Kim Olesen
I might be wrong about this. The 1/4 wavelenght at one side of the mouth of a full scale is not the full story. The formula for a fullscale round horn is: 2*PI*r = 1/1 Wavelenght. So the horn will have a circumference of the wavelengt. This is not the same as saying that the horn has to have an opening of 1/4 wavelenght !
For a square fullscale horn you calculate the
Mouth Area = (1/4*Pi)*(speedofsound/Fo)^2
A one-eight size horn
Mouth Area = (1/32*Pi)*(speedofsound/Fo)^2
Have you read "the show horn" Bruce Edgar ? There is also an M factor for the hyperbolic-exponential calculation, don't know if these calculation still is up to date...
Best regards
Kim Olesen
The reference to the perimeter being 1 wavelength at cut-off is correct according to my book "Hi-Fi Loudspeakers and Enclosures" by A.B. Cohen.
When you deviate from round to square or rectagular, other factors come into it.
From page 236 of the above ref:
For a desired low f resonse of 40 hz, theoretical cut-off of 32 hz the min short side is 7.0 ft, min long side 9.1 feet. The expansion rate 3.1% per inch or 44% per foot.
This book was copywritten in 1956, 1968. Mine is the 18th printing in 1978. The author was the Manager of Acoustics Department, Instuments Systems Corporation, and former Vice President, Engineering, University Sound, Division of LTV - Altec. (Now Altec Lansing Corporation) He was at the helm in the hay day of Altec's "Voice of The Theatre" range. Which BTW, was recently re-released due to public demand. About 6000 US$ each.
So I am not going to dispute his work!!
One other point. I asume you want to use this horn as a wide range. The spiral horn may cancel a lot of HF energy due to phase cancellation.
When you deviate from round to square or rectagular, other factors come into it.
From page 236 of the above ref:
For a desired low f resonse of 40 hz, theoretical cut-off of 32 hz the min short side is 7.0 ft, min long side 9.1 feet. The expansion rate 3.1% per inch or 44% per foot.
This book was copywritten in 1956, 1968. Mine is the 18th printing in 1978. The author was the Manager of Acoustics Department, Instuments Systems Corporation, and former Vice President, Engineering, University Sound, Division of LTV - Altec. (Now Altec Lansing Corporation) He was at the helm in the hay day of Altec's "Voice of The Theatre" range. Which BTW, was recently re-released due to public demand. About 6000 US$ each.
So I am not going to dispute his work!!
One other point. I asume you want to use this horn as a wide range. The spiral horn may cancel a lot of HF energy due to phase cancellation.
Hi Kim and Geoff,
with the software I used the mouth would be much larger than my 60cm X 250cm. What I've done is to calculate the mouth with cut off = 35hz and rectangular mouth with 60cm width. Then I cut the horn when the height of the mouth were 250cm (1/4 wave 35hz).
This is an empirical procedure. With a spiral shape I can easily have a long mouth, but as tight as possible. This way the horn can be appended to the wall leaving the floor free.
The question is what frequencies will come out from such a horn?
with the software I used the mouth would be much larger than my 60cm X 250cm. What I've done is to calculate the mouth with cut off = 35hz and rectangular mouth with 60cm width. Then I cut the horn when the height of the mouth were 250cm (1/4 wave 35hz).
This is an empirical procedure. With a spiral shape I can easily have a long mouth, but as tight as possible. This way the horn can be appended to the wall leaving the floor free.
The question is what frequencies will come out from such a horn?
Hi Geoff H
I don't have this book, but the short/long side is "min" lenght... so i quess this is a minimum size for the mouth (at fo), is there a calculation for a 1/1, 1/2, 1/4, 1/8 size horn in this book?.
The expansion rate ? is this instead of the exponential / hyberbolic calculation ?
What about W. Marshall Leach's papers ? Bruce Edgar used these calculations in "the show horn" and "monolith".
Best regards
Kim Olesen
I don't have this book, but the short/long side is "min" lenght... so i quess this is a minimum size for the mouth (at fo), is there a calculation for a 1/1, 1/2, 1/4, 1/8 size horn in this book?.
The expansion rate ? is this instead of the exponential / hyberbolic calculation ?
What about W. Marshall Leach's papers ? Bruce Edgar used these calculations in "the show horn" and "monolith".
Best regards
Kim Olesen
Hi Kim.
The expansion would be based on exponential. Hyperbolic would require more maths.
The mouth area is based on the accustic resistance of air, being 42 ohms per sq cm. If the radiator (or mouth) is less than a wavelength in
diameter, the radiation resistance goes down, we loose coupling, cones have to travel further, etc.
Just to give an idea, a 15" driver at 60Hz will have a radiation resistance of 10 ohms, so only about 20% of the available mechanical energy is transfered to the air. That loss is partially regained by extra cone travel, and the Z goes up.
The horn is nothing more than an accustical transformer. A half size horn will only do half the job. If you scale it down, you will raise the cut-off freq.
Cheers,
Geoff
The expansion would be based on exponential. Hyperbolic would require more maths.
The mouth area is based on the accustic resistance of air, being 42 ohms per sq cm. If the radiator (or mouth) is less than a wavelength in
diameter, the radiation resistance goes down, we loose coupling, cones have to travel further, etc.
Just to give an idea, a 15" driver at 60Hz will have a radiation resistance of 10 ohms, so only about 20% of the available mechanical energy is transfered to the air. That loss is partially regained by extra cone travel, and the Z goes up.
The horn is nothing more than an accustical transformer. A half size horn will only do half the job. If you scale it down, you will raise the cut-off freq.
Cheers,
Geoff
Hi Geoff H
A fullscale horn will be the best, and scale down horn will have some problems, but also it will have Wife Approval Factor
.
Bruce Edgar also calculates an M value for the Hyperbolic/Exponential horn calculation, this also has something to do with the resistance.... Do you have more info on this ? When i made my first horn ( http://www.micro-io.dk/speaker.htm ) i just did a Exp calculation (M=1, 35hz, Throat 59cm^2) . They go down to around 42hz, but has some peaks, simply because it is only 1/4 wavelenght! But maybe it could be a little better with some tweaks in the calculations.
Any idea of the placement of Throat? in the spiral horn the throat opening is mounted at 90 degress, and not as in a normal horn. Will this affect anything ?
Best regards
Kim Olesen
A fullscale horn will be the best, and scale down horn will have some problems, but also it will have Wife Approval Factor
.Bruce Edgar also calculates an M value for the Hyperbolic/Exponential horn calculation, this also has something to do with the resistance.... Do you have more info on this ? When i made my first horn ( http://www.micro-io.dk/speaker.htm ) i just did a Exp calculation (M=1, 35hz, Throat 59cm^2) . They go down to around 42hz, but has some peaks, simply because it is only 1/4 wavelenght! But maybe it could be a little better with some tweaks in the calculations.
Any idea of the placement of Throat? in the spiral horn the throat opening is mounted at 90 degress, and not as in a normal horn. Will this affect anything ?
Best regards
Kim Olesen
Hi Kim,
As you want wide range, the throat should be conventional. The compression chamber can be any shape to fill the centre of the spiral.
Don't forget to have a removable section so you have access to the driver if needed.
Have you thought about the volume of the compression chamber? IIRC you need to push the resonance up to a point in the lower octave of the horn, and the compliance should match the air mass of the horn.
I may have to oil some gears upstairs! Its a long time since I built a HF horn - 300Hz cut off, using a 5" Rola. I had all that info then.
I am wondering if the FE206E would be better in a true BR, with front horn loading. Not a ducted port. Port area is about 80% of cone area. Cabinet is sized to tune the system. Damping is adjusted with a 1.5v battery to achieve excellent transient response.
But then you want a horn.
Cheers
As you want wide range, the throat should be conventional. The compression chamber can be any shape to fill the centre of the spiral.
Don't forget to have a removable section so you have access to the driver if needed.
Have you thought about the volume of the compression chamber? IIRC you need to push the resonance up to a point in the lower octave of the horn, and the compliance should match the air mass of the horn.
I may have to oil some gears upstairs! Its a long time since I built a HF horn - 300Hz cut off, using a 5" Rola. I had all that info then.
I am wondering if the FE206E would be better in a true BR, with front horn loading. Not a ducted port. Port area is about 80% of cone area. Cabinet is sized to tune the system. Damping is adjusted with a 1.5v battery to achieve excellent transient response.
But then you want a horn.
Cheers
KimBOlesen said:
Hi Kim,
You made a very nice Cornu horn. I like the Idea of the acrylic material: what about a whole transparent horn?
Two questions. Cornu horns are rated as 70hz cut off (www.cornu.de). Your 42hz are measured?
For 1/4 wavelenght you mean the lenght of the horn? I meant the lenght of the mouth.
Hi thomaseliot
To get a WA i had to keep these speakers at 98cm x 98cm.
Transparent horn? yes, price of 4m^2 10mm acrylic was very high!!
Best regards
Kim Olesen
To get a WA i had to keep these speakers at 98cm x 98cm.
The Cornu uses a FE108 and is smaller. I used a FE168EZ, and tried calculating the total volume of a speaker so that i could keep the size at about 1mx1m. Horn is calculated as 35hz and cut at 1/4 wavelenght (throat to mouth). rolloff at 42hz is measured...
Yes... this is the smallest you get it, bigger will be better!
Transparent horn? yes, price of 4m^2 10mm acrylic was very high!!
Best regards
Kim Olesen
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