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How good is Hornresp?
How good is Hornresp?
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Old 18th November 2021, 09:03 PM   #1
peterjohnswindley is offline peterjohnswindley  United States
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Default How good is Hornresp?

How good is Hornresp?



So first off- I am aware that this software is free. So even if it's just a bit of fun I am definitely not complaining.

Also, I'm aware that this has probably been discussed a lot before, but cannot find any dedicated thread, other than David's pinned thread. If there is such a thread, please point me in the direction and I will duly delete this thread.


I'm working on tapped horns. My current attitude to using it is based on hoping that it 'probably gives a good general indication' of how a real built horn will sound. And I'm expecting to make at least a couple of mocks in MDF before making my final 'product'.

Is this a reasonable approach?

Are there any known ways in which the software (as excellent as I presume it is) cannot be expected to predict reality?
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Old 18th November 2021, 09:17 PM   #2
stv is online now stv  Europe
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If you read through the hornresp thread you will see examples of exact match between simulation and measurements. The problem is not the simulation software (it is very precise), the problem is rather how to model the loudspeaker exactly. Precise model will give precise results.
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Old 18th November 2021, 09:40 PM   #3
weltersys is offline weltersys  United States
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You can definitely expect "a good general indication" from Hornresp.
Most deviations from the simulation to the measured can be accounted for by differences between "as built" and "as simulated"- folds are not the quite same volume or length as a straight expansion, high aspect ratio rectangular shapes are not the same as a circle, exit and entrance shapes are assumed to be circular, "half space" requires one to bury the cabinet in the ground.

In addition, speaker compliance (and reduced Bl) usually progressively limits excursion past Xmax, while Hornresp (and most simulations) don't (can't) factor that in, though up to Xmax predictions should be close to measured.

Voice coil inductance can be variable, double-click on the value for Le to bring up a separate dialog box to enter the semi-inductance parameters.

The Subwoofer DIY Page - Semi-Inductance

Semi-Le_Calc: Calculator for Advanced Inductance Model Incorporating Semi-Inductance

At any rate, there are a lot of things to consider when making new designs, or even changing drivers in an old design.
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Old 18th November 2021, 10:27 PM   #4
peterjohnswindley is offline peterjohnswindley  United States
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this is very impressive to hear!
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Old 18th November 2021, 10:37 PM   #5
peterjohnswindley is offline peterjohnswindley  United States
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Quote:
Originally Posted by weltersys View Post
You can definitely expect "a good general indication" from Hornresp.
Most deviations from the simulation to the measured can be accounted for by differences between "as built" and "as simulated"- folds are not the quite same volume or length as a straight expansion, high aspect ratio rectangular shapes are not the same as a circle, exit and entrance shapes are assumed to be circular, "half space" requires one to bury the cabinet in the ground.

In addition, speaker compliance (and reduced Bl) usually progressively limits excursion past Xmax, while Hornresp (and most simulations) don't (can't) factor that in, though up to Xmax predictions should be close to measured.

Voice coil inductance can be variable, double-click on the value for Le to bring up a separate dialog box to enter the semi-inductance parameters.

The Subwoofer DIY Page - Semi-Inductance

Semi-Le_Calc: Calculator for Advanced Inductance Model Incorporating Semi-Inductance

At any rate, there are a lot of things to consider when making new designs, or even changing drivers in an old design.
Right.


I'm using the maximum SPL feature a lot- and my design does rely on Hornresp's predictions of how the sound changes at different levels of input power.

In fact, with this design, it looks like it's quite easy to have too much headroom. It only sounds the way I intend it to between 200 and 700W. Given it is intended for a live sound reinforcement purpose, I expect I will use a good deal of the wattage.
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Old 18th November 2021, 11:07 PM   #6
weltersys is offline weltersys  United States
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The "maximum SPL" feature is not indicative of "sound changes" at different levels of input power.
Start thinking in terms of voltage, not watts- and yes, you will want to use all the peak voltage available for live sound reinforcement.
Design so driver excursion in the pass band does not exceed Xmax at Pe, and you will be in the ballpark.
That said, a driver's AES Pe rating (in watts) is measured in free air at the voltage equivalent to driving it's nominal impedance to that level, but it's free air impedance will be far higher than in a TH.
For live use, long term "RMS" limiting with a time constant of longer than 500 ms (milliseconds) should generally be no more than half the AES ratings.

Last edited by weltersys; 18th November 2021 at 11:22 PM.
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Old 19th November 2021, 02:59 AM   #7
Brian Steele is offline Brian Steele  Grenada
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Quote:
Originally Posted by peterjohnswindley View Post
Are there any known ways in which the software (as excellent as I presume it is) cannot be expected to predict reality?
Hornresp does not include the effect of box losses in the TH model. As a result the actual response might look a bit "smoothed" compared to what the sim suggests it should be. You can however emulate the effect of box losses by adding a low value (1) for stuffing in each element of the sim.

Also, when the dimensions of the speaker's box come within a 1/4 wavelength of the frequencies that the speaker is trying to reproduce, there's going to be deviation from the sim, but that's true for most design programs.

Hornresp is a great tool, but it can be a bit difficult to get into it at the first. Once you learn how to use it though, you'll realize how powerful it really is. For example, do you want to model how the position of the driver and/or the position of the vent can impact the response of a vented box? Hornresp can do that...
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Old 19th November 2021, 03:50 AM   #8
NeilBlanchard is offline NeilBlanchard  United States
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I think the challenge using Hornresp, is that you need a good accurate way to draw the design, as you are doing iterations in Hornresp. As mentioned, it is the interpretation / translation of the design between Hornresp and the drawing - in both directions.

I am fairly new to Hornresp, and there is a steep initial learning curve. It is deep, and complex - and it usually can do everything; and its just a matter of finding how to do it. I used it for two mass loaded transmission line designs, and it is remarkably precise and accurate, in my experience.
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Old 19th November 2021, 02:35 PM   #9
peterjohnswindley is offline peterjohnswindley  United States
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Quote:
Originally Posted by weltersys View Post
The "maximum SPL" feature is not indicative of "sound changes" at different levels of input power.
Start thinking in terms of voltage, not watts- and yes, you will want to use all the peak voltage available for live sound reinforcement.
Design so driver excursion in the pass band does not exceed Xmax at Pe, and you will be in the ballpark.
That said, a driver's AES Pe rating (in watts) is measured in free air at the voltage equivalent to driving it's nominal impedance to that level, but it's free air impedance will be far higher than in a TH.
For live use, long term "RMS" limiting with a time constant of longer than 500 ms (milliseconds) should generally be no more than half the AES ratings.

Ah - Iím confused in that case.

Because the shape of the response in the acoustic power window does change when you adjust the max wattage and displacement parameters. And you can work this feature with only those two options engaged.

What is actually happening then?
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Old 19th November 2021, 02:38 PM   #10
peterjohnswindley is offline peterjohnswindley  United States
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Ah yes thatís what I was thinking.

So Iím guessing hornresp assumes an infinitely hard and stiff pathway, with no crosstalk between the neighbouring folds?

And plywood will tend to absorb certain frequencies, as if said infinitely stiff pathway already had some absorbent material applied.

Quote:
Originally Posted by Brian Steele View Post
Hornresp does not include the effect of box losses in the TH model. As a result the actual response might look a bit "smoothed" compared to what the sim suggests it should be. You can however emulate the effect of box losses by adding a low value (1) for stuffing in each element of the sim.

Also, when the dimensions of the speaker's box come within a 1/4 wavelength of the frequencies that the speaker is trying to reproduce, there's going to be deviation from the sim, but that's true for most design programs.

Hornresp is a great tool, but it can be a bit difficult to get into it at the first. Once you learn how to use it though, you'll realize how powerful it really is. For example, do you want to model how the position of the driver and/or the position of the vent can impact the response of a vented box? Hornresp can do that...
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