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Old 21st April 2013, 05:41 AM   #3401
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Default Hornresp Update 3200-130421

Quote:
Originally Posted by David McBean View Post
The Filter Wizard does not work when Eg is set to zero volts.
Hi Everyone,

To prevent a fatal error from being generated, the Filter Wizard is now disabled when Eg is set to zero, or when maximum SPL has been calculated.

Kind regards,

David
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Old 21st April 2013, 05:45 AM   #3402
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Quote:
Originally Posted by NEO Dan View Post
Is that really a bug David, it seems to me that constant velocity is to isolate what the "horn" itself is doing?
Hi Dan,

It was a bug to the extent that it created a fatal error :-).

Kind regards,

David
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Old 21st April 2013, 06:52 AM   #3403
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Hi just a guy,

Quote:
Originally Posted by just a guy View Post
What I was trying to convey is that I have about as much interest in doing a video tutorial as you have in adding more segments.
In that case, it seems that neither project has much of a chance of getting off the ground any time soon :-).

Quote:
Originally Posted by just a guy View Post
I did show you an example where a 4 segment model was in significant error simply by exporting the file and opening it in Akabak, simply due to CON vs PAR, so I don't think the need is overrated.
As I recall, you showed that there was a small difference of about 1 dB at a few frequencies when Hornresp was used to compare the SPL responses of a horn profile approximated by four parabolic segments against the same profile approximated by four conical segments.

The difference is as expected. What I don't understand though, is how this example demonstrated the need for more segments in Hornresp.

Quote:
Originally Posted by just a guy View Post
I was just giving you something to think about.
That's the last thing I need - something else to think about :-).

Kind regards,

David
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Old 21st April 2013, 02:37 PM   #3404
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Quote:
As I recall, you showed that there was a small difference of about 1 dB at a few frequencies when Hornresp was used to compare the SPL responses of a horn profile approximated by four parabolic segments against the same profile approximated by four conical segments.

The difference is as expected. What I don't understand though, is how this example demonstrated the need for more segments in Hornresp.
Here's my original post describing this error.

Quote:
Originally Posted by just a guy View Post
Hi, I agree with you in most cases it won't have much effect. But it only took me about 3 minutes to create this mess. I'm pretty sure I could show a much worse example if I spent more time on it.

Click the image to open in full size.

The only difference between these two lines is PAR vs CON segments and my lines don't overlay nearly as nicely as yours. I noticed this problem almost immediately when Hornresp allowed PAR segments. I don't remember which model caused me the most trouble but I've seen examples much worse than I've posted here.

As I pointed out originally this isn't a fatal flaw, it doesn't seem to shift the peaks right or left (which would be really bad) it just changes the amplitude a bit. Even though this isn't bad I would prefer to avoid surprises like this. In very large horns, 2 db at tuning can be a difference of hundreds of liters of enclosure size. I'd really like to be as accurate as possible when I fold.

Although I haven't studied in depth what factor is causing this, I think it's one or more very long segments that will cause this discrepancy.

(I got the mail, thanks!)
This result isn't terrible but it's certainly not accurate either; it's +1 db in one area and -1 db in another area, and the error covers most of the usable bandwidth of a sub. And I could easily show a more dramatic example. Besides, I have two other reasons this situation is nowhere near ideal.

1. Once you are in Akabak and you make changes you no longer have a Hornresp "horn data" export wizard to give csa vs length. This turns horn folding into a nightmare. A few people sent me various equations and spreadsheets to work around this and there are ways to work around it within Akabak as well but Hornresp is a better tool for this job.

2. Flexibility - more segments allows more freedom. 4 segments allows a very limited range of opportunity while more segments increases the options exponentially. This may not seem too important but I've spent way more of my life using Akabak than I'd like only to end up with inaccurate results (as outlined in the quoted post) and no "horn data" export wizard.

You can trivialize the importance of this but I don't think you can deny it would make Hornresp better than it already is. And at this point, Hornresp is so advanced that there's not many ways left to make real and meaningful improvements. With the recent addition of filters there's only 3 major potential improvements left (IMO) and this is one of them.

But I know, it isn't going to happen. I'll drop it now for another year.

Last edited by just a guy; 21st April 2013 at 02:48 PM.
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Old 22nd April 2013, 07:33 AM   #3405
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Hi just a guy,
Quote:
Originally Posted by just a guy View Post
You can trivialize the importance of this but I don't think you can deny it would make Hornresp better than it already is.
I can deny anything I like :-).

Similar to the way that a chain is only as strong as its weakest link, the Hornresp simulation model is only as good as its weakest assumption. As previously explained, there are far more significant limitations in the model than the four segment maximum. There is little point in specifying a bass horn profile accurate to the nearest millimetre when plane wavefronts are being assumed, when the sound wavelengths involved are measured in metres, and when the actual physical results can be appreciably affected by having a folded acoustic path, vibrating enclosure panels, a flexing driver diaphragm and other non-linearities not accounted for in the standard lumped-element model as used in Hornresp.

With Hornresp, I have tried to strike a sensible and practical balance between the accuracy of the predictions and the number of inputs required to achieve those predictions. In my experience, and as I think you and others have confirmed in your comments on AkAbak, the more complex the input requirements become, the more difficult it is to use the software, and the greater is the chance of getting something wrong.

Quote:
Originally Posted by just a guy View Post
I'll drop it now for another year.
Thanks - you can make that two years, if you like :-).

Kind regards,

David
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Old 22nd April 2013, 07:35 AM   #3406
Jmmlc is offline Jmmlc  France
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Quote:
Originally Posted by Kolbrek View Post
System phase response and group delay will of course change with the filter, but David doesn't show these quantities.

Bjørn
Hello Bjørn,

For the moment David doesn't show group delay but this will probably be a further improvement required...

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 22nd April 2013, 08:00 AM   #3407
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Quote:
Originally Posted by David McBean View Post
Hi just a guy,

I can deny anything I like :-).
True enough. I didn't think you would, but touche.

Quote:
Similar to the way that a chain is only as strong as its weakest link, the Hornresp simulation model is only as good as its weakest assumption. As previously explained, there are far more significant limitations in the model than the four segment maximum. There is little point in specifying a bass horn profile accurate to the nearest millimetre when plane wavefronts are being assumed, when the sound wavelengths involved are measured in metres, and when the actual physical results can be appreciably affected by having a folded acoustic path, vibrating enclosure panels, a flexing driver diaphragm and other non-linearities not accounted for in the standard lumped-element model as used in Hornresp.
Understood. But I don't see a problem with trying to be as accurate as possible.

There's not much we can do about the plane wave assumption. But the folded acoustic path, vibrating enclosure panels, flexing diaphragm and other non-linearities are all effects that are well known and these effects are accounted for outside the software to some degree by savvy designers. These effects are all well outside the scope of most simulation software and for good reason.

On the other hand, the fact that the wavelengths are measured in meters is of no consequence, the graphs are measured in db and I've shown they are not accurate in some cases. And multiple segments is definitely within the scope of simulation software if the author desires it.

Quote:
With Hornresp, I have tried to strike a sensible and practical balance between the accuracy of the predictions and the number of inputs required to achieve those predictions. In my experience, and as I think you and others have confirmed in your comments on AkAbak, the more complex the input requirements become, the more difficult it is to use the software, and the greater is the chance of getting something wrong.
Saving us from ourselves... I like it, lol.

Quote:
Thanks - you can make that two years, if you like :-).

Kind regards,

David
No problem. I wasn't planning to ever bring it up again but you practically invited it with your "never say never" comments and continuing to add other features you have historically said are not going to happen.

Anyway, if it's not clear from this discussion and others that I know you've seen, I think Hornresp is already too good to be true and I'm not trying to complain. Just pointing out there's still a bit of room for improvement. Not much room anymore but still a little bit.

So thanks again, I love Hornresp.

Last edited by just a guy; 22nd April 2013 at 08:18 AM.
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Old 22nd April 2013, 08:13 AM   #3408
Kolbrek is offline Kolbrek  Norway
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Quote:
Originally Posted by just a guy View Post
This result isn't terrible but it's certainly not accurate either; it's +1 db in one area and -1 db in another area, and the error covers most of the usable bandwidth of a sub. And I could easily show a more dramatic example.
Since you need this kind of accuracy, I assume that your designs as built match the Hornresp predictions to within significantly less than +/-1dB?

-Bjørn
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Old 22nd April 2013, 08:18 AM   #3409
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Quote:
Originally Posted by Jmmlc View Post
For the moment David doesn't show group delay but this will probably be a further improvement required...
Hi Jean-Michel,

Unfortunately, as is the case with the Loudspeaker Wizard, it would not be possible for me to retain the real-time updating of results in the Filter Wizard if phase response or group delay for the complete system (including the filter stage) was required.

I think I would prefer to continue to have the ability to see immediate changes in the results, rather than sacrifice this feature in order to add in a group delay chart :-).

Kind regards,

David
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Old 22nd April 2013, 08:24 AM   #3410
NEO Dan is offline NEO Dan  United States
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Quote:
Originally Posted by Kolbrek View Post
Since you need this kind of accuracy, I assume that your designs as built match the Hornresp predictions to within significantly less than +/-1dB?

-Bjørn
Are you kidding? Apparently you've not seen the Canadian precision lathe turning horn profiles?

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Last edited by NEO Dan; 22nd April 2013 at 08:26 AM.
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