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Old 22nd June 2011, 06:15 AM   #1981
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Hi Don,

Quote:
Originally Posted by Don Hills View Post
In summary, if I build an enclosure with the port length as specified by Hornresp, it should measure similarly to the simulated enclosure. But in AkAbak, I have to manually add one end correction to the length provided by Hornresp in order to get a correct simulation.
Correct.

When simulating a bass-reflex system in AkAbak you will need to add an "inside" end correction to the Hornresp Lpt value. The AkAbak Helmholtz Resonator tool may be of some help in this regard.

Hopefully the Hornresp prediction will be reasonably close to your measured results. You may find however that it is necessary to fine-tune your constructed system by altering the port tube length or enclosure volume slightly to get the exact Helmholtz resonance frequency as predicted by Hornresp. This is because Hornresp assumes an idealised configuration as shown in the schematic diagram, whereas in practice this is unlikely to be the case.

Incidentally, Hornresp uses a slightly more accurate model than WinISD so if you are comparing results with that program you may notice some slight differences :-).

Kind regards,

David
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Last edited by David McBean; 22nd June 2011 at 06:17 AM.
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Old 23rd June 2011, 09:43 PM   #1982
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Thanks, David.

I plan to keep the end correction as a separate term rather than merging it with the physical length. There's less chance for error when translating the design back to sawdust.

I'm already using the Helmholtz tool as part of the process:
- Simulate a standard reflex enclosure.
- Divide the box 2/3 and 1/3.
- Change the port (with the tool) to resonate the 2/3 box at the same frequency as the original box.
- Join the two boxes with one such port, and port both boxes to the outside with two more such ports.

There is a slight "fiddle factor" in the process, in that the resonance frequencies for the 2 enclosures are supposed to be slightly different than that for the original enclosure. Part of the reason for modelling in AkAbak is because I want to investigate and see if the "fiddle factor" was required because the original design process had end correction "embedded" in some way.

I'm mainly interested in DCR designs because of the fashion for tall, thin, spousally acceptable enclosures. The DCR design reduces the problem of quarter-wave resonances falling in the passband.

I've never used WinISD. I use Unibox and Brian Steele's "Ported" spreadsheets. I have noticed slight differences between Unibox results and Hornresp results.
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Old 27th June 2011, 01:05 AM   #1983
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There is no substitute for RTFM.
I have managed to summarise the rules for end correction in AkAbak. They are as follows:

- For a port (duct) connected to a duct (two ducts of different area connected),
AkAbak does not add end correction.

- For a port (duct) connected to an enclosure, AkAbak adds an end correction to the
end connected to the enclosure.

- For a port (duct) with a radiator attached to one end, the radiator element
provides the end correction for that end.

In summary, when simulating a reflex system in AkAbak using an Enclosure and a Duct (port), the specified length for the port is the physical length, as it is in Hornresp.


This highlights a possible inconsistency between Hornresp and AkAbak.

When exporting a reflex enclosure, Hornresp models it as a large duct (the enclosure) connected to a small duct (the port). The duct length specified for the port is the physical length (length used for simulation in Hornresp, minus end correction).

In AkAbak, this length is thus too short for simulation, because AkAbak does not add end correction in this case. A single end correction has to be manually added to obtain the same results as the Hornresp simulation.

If Hornresp were to export the enclosure as an Enclosure element, no additional end correction would be required. The Enclosure element does allow specifying the major enclosure length, so the length-related resonances of the enclosure are included in the simulation results.

Do I understand it correctly yet?

Last edited by Don Hills; 27th June 2011 at 01:08 AM.
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Old 27th June 2011, 02:05 AM   #1984
Mark Kravchenko --- www.kravchenko-audio.com
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Quote:
Incidentally, Hornresp uses a slightly more accurate model than WinISD so if you are comparing results with that program you may notice some slight differences
I can vouch for this as I have been comparing the two for almost a year. Hornresp tends to be more accurate when you realize exactly what you are simulating.
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Old 27th June 2011, 07:17 AM   #1985
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Quote:
Originally Posted by Don Hills View Post
Do I understand it correctly yet?
Hi Don,

Seems okay to me.

I have no plans to export "Enclosure" elements to AkAbak, though :-).

Kind regards,

David
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Old 27th June 2011, 12:39 PM   #1986
60ndown is offline 60ndown  United States
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anyone got a link to hornresp for mac?
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Old 27th June 2011, 02:49 PM   #1987
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try using one of the virtualization methods like vmware fusion on a mac to run windows. This will work for sure but requires at least a windows lizense...

Wine seems to be somewhat ported to the mac from linus, so there myght be a possibility, too, I didnīt try it out though.

One last alternative I tried a few weeks ago is reactos, wait a second, I try again...

Oh, recent reactos running under vmware seems to work with recent hornresp, at least I could simulate the default project... Interesting. This sure is something worth investigatin further - I am surprised, it didnīt work last time...

If you like, I will compile something in order to bundle a package "hornresp on any PC without any windows-license....".

Click the image to open in full size.

edit: hm,seems to crash sometimes after a few minutes.
Attached Images
File Type: png reacots0.3.13.vmawre hornresp 28.4.png (74.8 KB, 368 views)

Last edited by Sabbelbacke; 27th June 2011 at 02:57 PM.
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Old 27th June 2011, 03:10 PM   #1988
60ndown is offline 60ndown  United States
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im not good at computers.

i dont risk virus etc easily.


Quote:
Originally Posted by Sabbelbacke View Post
try using one of the virtualization methods like vmware fusion on a mac to run windows. This will work for sure but requires at least a windows lizense...

Wine seems to be somewhat ported to the mac from linus, so there myght be a possibility, too, I didnīt try it out though.

One last alternative I tried a few weeks ago is reactos, wait a second, I try again...

Oh, recent reactos running under vmware seems to work with recent hornresp, at least I could simulate the default project... Interesting. This sure is something worth investigatin further - I am surprised, it didnīt work last time...

If you like, I will compile something in order to bundle a package "hornresp on any PC without any windows-license....".

Click the image to open in full size.

edit: hm,seems to crash sometimes after a few minutes.
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Old 27th June 2011, 03:19 PM   #1989
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Running a virtual machine has nothing to do with a virus, donīt worry.

A simple "honresp for MAC" doesnīt exist.
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Old 28th June 2011, 12:42 AM   #1990
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And as of yet I have not found a cheap or free emulation package for the powerPC architecture. So far I end up having to run in Ubuntu under wine and just be careful not to use certain input screens that cause it to crash.
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