Hornresp

Hornresp Update 3120-130311

Hi Everyone,

Under certain conditions the new 'Radiation Angle' tool menu command could be enabled even when the input parameters window was not in edit mode. This anomaly has been now fixed, with the menu command only being enabled when the Ang parameter value has the focus in edit mode.

EDIT - Have just found another bug (will try to release a further update tomorrow).

Kind regards,

David
 
Hornresp Update 3120-130312

EDIT - Have just found another bug (will try to release a further update tomorrow).

Hi Everyone,

With reference to my comment above, when the Ang parameter value was changed using the new 'Radiation Angle' tool, the value would revert back to the original value when a different record was selected. This bug has now been fixed.

Kind regards,

David
 
diyAudio Moderator
Joined 2008
Paid Member
David, is the high frequency disturbance in this polar map due to mouth diffraction? Is it possible to model a conical horn like this with the intended mouth treatment added, or alternately to eliminate this diffraction from the model so I can see the directivity of the horn at these frequencies?
 

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David, is the high frequency disturbance in this polar map due to mouth diffraction? Is it possible to model a conical horn like this with the intended mouth treatment added, or alternately to eliminate this diffraction from the model so I can see the directivity of the horn at these frequencies?

Hi AllenB,

To allow me to investigate further, could you please post a screenprint of the input parameter window values that produce this result. Thanks.

Kind regards,

David
 
Does the "Horn Throat Peak Sound Pressure" reflect the pressure at S1 or the pressure in the front chamber? What I really would like to know is the pressure on the cone.

Hi Mårten,

The Horn Throat Peak Sound Pressure chart shows the pressure at S1 for a normal horn, and at S2 for an offset driver or tapped horn.

With the resonances masked option selected, the calculated pressure on the horn-facing side of the diaphragm will be the same as the pressure at the throat . With the resonances not masked option selected, the pressure on the diaphragm will be marginally higher than the pressure at the throat, but not enough to be of any concern.

To illustrate -

Attachment 1 shows the pressure at the throat S1 of the default record with resonances unmasked.

Attachment 2 shows the pressure on the horn-facing side of the diaphragm of the default record with resonances unmasked.

As you can see, the difference between the two charts is minimal.

Kind regards,

David
 

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Thanks for you explanation David

I am designing a bass horn with extremely high compression ratio. The throat pressure is double of anything else I have built. I am a bit concerned with breaking the cone. So I thought maybe I can lower the pressure by adding a big front chamber.

I would like to add calculation of pressure on the cone to the wishlist.
 
David, is the high frequency disturbance in this polar map due to mouth diffraction? Is it possible to model a conical horn like this with the intended mouth treatment added, or alternately to eliminate this diffraction from the model so I can see the directivity of the horn at these frequencies?

Hi AllenB,

Thanks for providing the additional information.

The high frequency disturbance you are seeing is not due to mouth diffraction. The directivity patterns produced by Hornresp are such that when the results for all frequencies are consolidated into a single polar map, the results as shown in your example are produced. It is not possible to readily change the model.

You may find that the normalised polar map view (where values are shown relative to the on-axis pressure) gives a better indication of directivity - see Attachment 1.

The beam width chart can also be useful in highlighting directivity characteristics - see Attachment 2, which clearly shows the constant directivity effect at higher frequencies.

Individual patterns can also be viewed at selected frequencies to further illustrate directivity characteristics - see Attachment 3.

Kind regards,

David
 

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I am a bit concerned with breaking the cone. So I thought maybe I can lower the pressure by adding a big front chamber.

I would like to add calculation of pressure on the cone to the wishlist.

Hi Mårten,

If you care to post your proposed design I would be happy to calculate the diaphragm pressure for you.

You can add the large chamber to a separate design for me to check as well, if you like.

At this stage I have no plans to add any further charts to the production version of Hornresp.

Kind regards,

David
 
I am very grateful for you help.

Hi Mårten,

You're welcome :).

Attachment 1 shows the pressure at the throat, and attachment 2 shows the pressure on the diaphragm. In each case, resonances are unmasked.

As mentioned previously, when resonances are masked the results are the same.

Kind regards,

David
 

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Hornresp Update 3130-130325

Hi Everyone,

CHANGE 1

The accuracy of the normalised polar map for a constant directivity horn has been improved at those frequencies where the off-axis pressure is greater than the on-axis pressure.

Attachment 1 shows an example where the off-axis pressure is greater than the on-axis pressure across a beamwidth of approximately 64 degrees.

Attachment 2 shows an example of the old normalised polar map.

Attachment 3 shows the new normalised polar map for the same horn system.

My thanks to AllenB for the query that prompted me to investigate this issue.

CHANGE 2

The throat sound pressure chart has been changed to a diaphragm pressure chart showing the peak sound pressure at the driver diaphragm, and the particle velocity chart has been changed to a diaphragm velocity chart showing the driver diaphragm peak velocity.

The diaphragm pressure chart can be selected from the Tools menu when the SPL response window is displayed.

The diaphragm velocity chart can be selected from the Tools menu when the diaphragm displacement window is displayed.

My thanks to Mårten (more10) for the query that prompted me to make this change.

Kind regards,

David
 

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Plug in/s etc

@ David McBean

Hi, the diaphragm pressure/velocity charts will prove Extremely helpful :) Thanks

I know you incorporated some visualisation software from another member, into HR last year. So it occurred to me that, as this is possible to do, i thought that due to the fact that many people, my self included, have requested a filter to be included in HR, this would/could be a way to achieve it = :)

Right now i don't know who could provide this Plug In, for want of a better description. But i'm sure there must be someone who could. If you agreed, at least to consider it, the word would spread & i feel sure someone would come forward & offer to assist.
 
Ah, so the old method of normalising was going up over the zero degree point in places?

Hi AllenB,

With the old method, the on-axis (zero degree) pressure was the maximum level that could be displayed. Off-axis pressures higher than the on-axis pressure were incorrectly shown to be at the same level as the on-axis pressure. Now off-axis pressures higher than the on-axis pressure are correctly displayed.

Kind regards,

David