Hornresp

[tb46]

Posts #3077 and 3078

Hi David,

Thanks for taking a look at it. I was just hoping, that because you had already done something similar with the CH simulation model it might not be too involved, but here I am talking like the blind man about colour.

I have been using AkAbak for this, my only problem is, that there are no schematic diagrams or other forms of feedback in that program, and the more complex the simulation, the more difficult to know if I'm actually simulating what I'm trying to simulate (unless I already know the end result). I'll just have to spend more time with AkAbak.

Regards,

[David McBean]

Originally Posted by ßart West-VL.

I noticed some kind of 'sudden jump' when sliding Vrc and the appearance of 'Helmholtz freq' in the lower right corner. (red color)
The graph suddenly changes a lot too.

Hi Bart,

When a Helmholtz frequency is shown in Hornresp, it means that the dimensions of the vented-box enclosure and the associated port tube are such that the air in the tube (including appropriate end corrections) can be treated as an acoustic mass, and that the system acts as a pure Helmholtz resonator.

When a Helmholtz frequency is not given it means that the port tube is relatively long, and that it acts as a cylindrical horn rather than as a simple lumped acoustic mass. Rather than being a bass-reflex speaker, the system in effect becomes a back-loaded horn with a very large throat chamber. This can be readily confirmed by actually modelling the system as a back-loaded horn - the combined response results will be identical.

It just so happens that in your particular example, increasing the enclosure volume from 273.8 to 273.9 litres changes the port tube from the cylindrical horn model to the acoustic mass model. This is the reason for the 'sudden jump' in the combined SPL response. Very few bass-reflex speakers would normally have a port tube 1.1 metres in length, so the discontinuity seen at the model change threshold is unlikely to be a material issue when using Hornresp to analyse a practical bass-reflex design.

Kind regards,

David

[David McBean]

Originally Posted by tb46

Posts #3077 and 3078Thanks for taking a look at it. I was just hoping, that because you had already done something similar with the CH simulation model it might not be too involved, but here I am talking like the blind man about colour.

I have been using AkAbak for this, my only problem is, that there are no schematic diagrams or other forms of feedback in that program, and the more complex the simulation, the more difficult to know if I'm actually simulating what I'm trying to simulate (unless I already know the end result).

Hi Oliver,

Rest assured, if it was not difficult to fully integrate the functionality, I would have included it in a heartbeat :-).

As far as AkAbak is concerned, I find it quite helpful to draw network diagrams (with numbered nodes) for the more complex system configurations (in effect an extension of the simple diagram included in the Hornresp exported script). It makes it much easier to keep track of things.

Kind regards,

David

[ßart West-VL.]

Thank you David.
The long port is to have a port surface as big as possible while staying under a quarter wave lenght of the highest frequency the box has to provide.(±80hz)
It has been a balance between first port resonance and largest possible port.
I hope this doesn't mean my box works wrong or with artefacts because of other reasons unknown to me.

[David McBean]

Originally Posted by tb46

When simulating OD horns I'm using Ap1/Lpt to control the entry into the horn at the S2 location, and this seems to work. I would like to additionally have the ability to simultaneously provide a vent for the rear chamber, similar to the way you solved this for CH, by using S4/S5/L45 for the rear chamber port/horn.

Hi Oliver,

Further to my earlier comments...

For your OD design, use Ap and Lpt to specify the vented rear chamber port rather than Ap1 and Lpt to specify the throat chamber port. Not having the throat chamber port in the simulation model will make very little difference to the combined SPL response predicted results.

If you really want to take into account the minimal effect of the throat chamber port, then export the AkAbak script for the OD horn with Ap and Lpt specified, and manually add in an extra Duct element after the existing throat chamber duct to represent the throat chamber port.

Kind regards,

David

[David McBean]

Originally Posted by ßart West-VL.

I hope this doesn't mean my box works wrong or with artefacts because of other reasons unknown to me.

Hi Bart,

The Hornresp predictions should be reasonably accurate. It may be worthwhile calculating the results with resonances unmasked though, to avoid any nasty surprises.

Kind regards,

David

[tb46]

Hi David,

Thanks again.

Regards,

[grindstone]

Every time I catch some idea and start simming again, I visit this thread only to find out I'm another few revs behind and there are gifts of new features & bugfixes (and it still runs in wine!). David, I can't thank you enough--sincerely. I've had so much fun messing in your program over the years and I've learned a great deal.

[David McBean]

Originally Posted by grindstone

Every time I catch some idea and start simming again, I visit this thread only to find out I'm another few revs behind and there are gifts of new features & bugfixes (and it still runs in wine!). David, I can't thank you enough--sincerely. I've had so much fun messing in your program over the years and I've learned a great deal.

Hi grindstone,

Many thanks for your kind comments - you have made my day :-). I am particularly pleased to hear that Hornresp has proved to be a helpful and enjoyable-to-use learning tool for you, as that is exactly what I wanted to achieve with the program.

Kind regards,

David

[maxmercy]

David,

I wish to echo that sentiment. Hornresp is a wonderful tool and gives me nearly WYSIWYG results when designing front loaded bass horns.

Thanks!!

JSS