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Old 3rd October 2012, 11:17 PM   #2871
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Quote:
Originally Posted by schmeet View Post
SS, looking at the attachments in your post with the Bass Box Pro design. You do have a box that is 104 litres.

However, unless I'm reading it wrong, you also seem to have a port that is 4936mm long with a diameter of 274.2mm. This is an extra 291 litres of port
I believe you are reading that correctly, but that is only if you are trying to reach Xmax you need a port that size, if you look at the attached pic you will see that you can achieve decent SPL with a much smaller port, that probably only adds 4cms to the height and length.

You will also notice in post 2856 at 30Hz (280 litres) I had a SPL of 110dB, where as in post 2863 you will notice NEO Dan went up to 326.5 litres to achieve 20Hz with an SPL of only 92.5dB (both using the Pro 5100)

But here's the catch... even though HR models a much larger box, no matter how much volume I throw at the BR in BBP it wont go as low as the model in post 2866.

So until such time as BBP adds horn functions to its products I have to look at alternatives even if they are less user friendly.

I am finding it easier to use, but still feel like I am twiddling knobs with understanding why, would still like to see a more comprehensive and modern help file that explains what takes place when I alter this slider or that slider.

A 500 litre box may not even be that big of an issue. I am looking to build the sub into a couch or chair to hide it in the room.
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Old 3rd October 2012, 11:49 PM   #2872
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Originally Posted by just a guy View Post
Sure, it's possible and not even that hard, but are you really voting against more segments?
No, far from it. I've had occasions where I could have done with one or two more segments in Hornresp.

Quote:
Originally Posted by just a guy View Post
While not terribly difficult, the method you describe requires quite a bit of time, every time, for every segment of every model. ...
Not if you have a utility for calculating the segments. I should port it to a spreadsheet for ease of use.
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Old 4th October 2012, 07:18 AM   #2873
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Originally Posted by just a guy View Post
please let us have more segments.
Hi just a guy,

The way that Hornresp is structured, the addition of more segments would require a complete re-write of the program. This is not something that I am in a position to do.

It is important to keep things in perspective, though. For bass horns, it is possible to get a pretty good indication of performance by approximating any design using the four segments available in Hornresp. The wavelength at 100 hertz is 3.44 metres, and differences of a centimetre or two from the desired profile are unlikely to have a significant impact on predicted response. A number of users have commented on how closely Hornresp results compare to AkAbak predictions even when many more segments have been used in AkAbak to define the profile.

Kind regards,

David
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Old 4th October 2012, 07:46 AM   #2874
Kolbrek is offline Kolbrek  Norway
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Quote:
Originally Posted by David McBean View Post
For bass horns, it is possible to get a pretty good indication of performance by approximating any design using the four segments available in Hornresp. The wavelength at 100 hertz is 3.44 metres, and differences of a centimetre or two from the desired profile are unlikely to have a significant impact on predicted response.
As an example of this, see the attached plot. Both are for a 40Hz exponential horn, S1 = 95, S2 = 31000, L12 = 441, ANG = 2 pi. The gray curve is the response when the horn is approximated by 50 conical elements. The black curve is for the same horn approximated by two conical elements. The deviation is at most 3.5dB. This would depend on the driver, though, but the differences between the actual profiles are quite large.

-Bjørn
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Old 4th October 2012, 01:09 PM   #2875
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Quote:
Originally Posted by David McBean View Post
Hi just a guy,

The way that Hornresp is structured, the addition of more segments would require a complete re-write of the program. This is not something that I am in a position to do.
Thanks for the answer, I guess that's the end of that.

Quote:
It is important to keep things in perspective, though. For bass horns, it is possible to get a pretty good indication of performance by approximating any design using the four segments available in Hornresp. The wavelength at 100 hertz is 3.44 metres, and differences of a centimetre or two from the desired profile are unlikely to have a significant impact on predicted response. A number of users have commented on how closely Hornresp results compare to AkAbak predictions even when many more segments have been used in AkAbak to define the profile.

Kind regards,

David
Hornresp does a lot better than "a pretty good indication".

But in reality there's only 3 usable segments to define the horn shape. Most (all?) bass horns are offset so a segment has to be wasted as a location placeholder for the driver.

If there was a way to gain back even just that one segment by defining driver position in a different way than using a segment, even that one segment would help.

But I'll let the segment dream die now, there's always Akabak and I still love Hornresp.

Thanks.

Last edited by just a guy; 4th October 2012 at 01:11 PM.
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Old 4th October 2012, 01:44 PM   #2876
schmeet is offline schmeet  United Kingdom
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Quote:
Originally Posted by Kolbrek View Post
As an example of this, see the attached plot. Both are for a 40Hz exponential horn, S1 = 95, S2 = 31000, L12 = 441, ANG = 2 pi. The gray curve is the response when the horn is approximated by 50 conical elements. The black curve is for the same horn approximated by two conical elements. The deviation is at most 3.5dB. This would depend on the driver, though, but the differences between the actual profiles are quite large.

-Bjørn
I'm not sure about this. A 40Hz exponential horn can be completely defined by 1 segment. 50 segments adds no extra information?

Or am I missing something here?

You need more segments if you want to model things like expansion chambers, or straight parts of the pipe, or at a bend in the enclosure (where you would model a slight expansion), or experimenting with putting stuffing in some sections and not others. Etc. etc etc.
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Old 4th October 2012, 01:48 PM   #2877
Kolbrek is offline Kolbrek  Norway
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Quote:
Originally Posted by just a guy View Post
If there was a way to gain back even just that one segment by defining driver position in a different way than using a segment, even that one segment would help.
Suggestion: The throat adapter is in effect a 5th segment. It is always conical, but that should be a minor issue. If it was possible to specify that the throat adapter should be the first segment in an otherwise offset horn, we would gain back that first segment for use in the main part of the horn.

-Bjørn
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Old 4th October 2012, 02:01 PM   #2878
Kolbrek is offline Kolbrek  Norway
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Quote:
Originally Posted by schmeet View Post
I'm not sure about this. A 40Hz exponential horn can be completely defined by 1 segment. 50 segments adds no extra information?
True, an exponential horn can be completely defined by a single exponential segment (or element). In the example shown, however, the exponential profile is approximated by 50 conical segments in one case, and 2 conical segments in the other. The idea was to show that even the extremely coarse 2-segment approximation was not that far off. (50 conical segments is very close to a single exponential).

Quote:
Originally Posted by schmeet View Post
You need more segments if you want to model things like expansion chambers, or straight parts of the pipe, or at a bend in the enclosure (where you would model a slight expansion), or experimenting with putting stuffing in some sections and not others. Etc. etc etc.
That is correct. And there are other reasons for using many conical elements instead of a single exponential as well. One case is where you don't want to use the plane wave assumption, which is inherent in the equations for finite horns given by for instance Olson. Instead you use a series of elements where the lengths and areas are based upon the expansion of the curved wave front.
Another case is when you want to model horns that do not have (simple) analytic expressions for pressure and volume velocity, like the LeCleac'h or tractrix horns.

-Bjørn
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Old 4th October 2012, 02:03 PM   #2879
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Kolbreck,
Sorry to interupt,but do you have details of your latest horn that replaced Azura 425. Did not see build info on your page. Sorry for OT.
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Old 4th October 2012, 10:53 PM   #2880
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Related to the recent discussion about parabolic profiles, the attached picture shows two superimposed schematic diagrams from Hornresp. One of the horns is a single parabolic segment. The other curve is the same horn made from 4 conical segments. In summary, "close enough for rock'n'roll".
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