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Old 7th December 2012, 08:32 AM   #1871
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Quote:
Originally Posted by Matthew Morgan J View Post
Awesome! Thank you David and Epa
That clears some things up for me ... I will remember to always bump up the LE for subwoofer sims to get more realistic graphs

I absolutely LOVE your software David! Hornresponse is not only helpful but has become essential to me! I cannot imagine just how dreadful horn designing must have been back in the dark ages before you crafted your masterpiece
Hi Matthew,

Thanks for your kind words - they are much appreciated :-).

I am a bit surprised that doubling the value of Le would make a worthwhile difference to the predicted response across the desired subwoofer passband. For example, in the attached screenprint the gray trace shows a typical tapped horn with a driver voice coil inductance Le of 1.2 millihenrys, and the black trace shows the same horn with 2 x Le.

With this example, it is only above about 400 hertz that the difference in response becomes meaningful.

Kind regards,

David
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File Type: png Le.png (64.7 KB, 315 views)
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Old 7th December 2012, 08:42 AM   #1872
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Originally Posted by Djim View Post
HornResp calculates perfectly the inductance for every frequency.
Hi Djim,

Just to clarify - Hornresp calculates the reactive impedance (or reactance) of the inductance at each frequency. The value of the inductance itself (Le) does not change with frequency.

Kind regards,

David
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Old 7th December 2012, 12:18 PM   #1873
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David ,
The link i pasted in this message was an example i found of what seems to often happen when people compare their simulated graphs with their measured responses ... I know it doesn't always work out exactly this way but it does seem to frequently show this pattern as far as i can tell ...
In this example the Sim shows a slight dip, like a "saddle" between two peaks..Im talking about the first peak at just under 30hz and the other just above 70hz with the dip being centered around 40hz ..... However in the measured response the dip is diminished and the peak at around 30 is gone completely .... The results are moreso flat than the model ... People will say that this is due to various "losses" and maybe this is true but i have also noticed that i can create the same effect in simulation by simply increasing Hornresponse's LE/inductance value ..... It may be purely coincidental but it seems to work ... Sorry to "preach to the choir" because i know many people have already noticed this pattern ...

A similar thing also seems to sometimes happen when a TH simulation has a perfectly flat graph in HR but once built and measured it shows a real-world rise somewhere in the middle (maybe around 50-70 hz depending on where the TH is tuned) and a slight sagging on the lower end of the usable response falling short by a few decibels compared to the sim around the fundamental ..... This is also a scenario that can be emulated by added some LE in the simulation ...

I know it may be improper to add LE to sims but in some cases it does seem to help get you closer-ish to real world results.



http://lh3.ggpht.com/_WXjTASetbPo/S6...chy%201w1m.JPG

Last edited by Matthew Morgan J; 7th December 2012 at 12:25 PM.
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Old 7th December 2012, 01:46 PM   #1874
epa is offline epa  Netherlands
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Quote:
Originally Posted by David McBean View Post
Hi Matthew,

Thanks for your kind words - they are much appreciated :-).

I am a bit surprised that doubling the value of Le would make a worthwhile difference to the predicted response across the desired subwoofer passband. For example, in the attached screenprint the gray trace shows a typical tapped horn with a driver voice coil inductance Le of 1.2 millihenrys, and the black trace shows the same horn with 2 x Le.

With this example, it is only above about 400 hertz that the difference in response becomes meaningful.

Kind regards,

David
hi david
the black trace looks a bit flatter.
al the th i have seen so far al have a flatter responce in realety then the sim ,under 100hz.
when you double le value in that sim ,its much closer to the real thing.
i know pannelflex could play a part also.
id like to see some th comparisons between 1 watt and 100 watts,to see if amplitude plays a role here to.
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Old 7th December 2012, 04:05 PM   #1875
GM is offline GM  United States
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Quote:
Originally Posted by Matthew Morgan J View Post
FWIW, this example indicates an improper tap point WRT driver specs to me.

GM
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Old 7th December 2012, 09:05 PM   #1876
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by David McBean View Post
Just to clarify - Hornresp calculates the reactive impedance (or reactance) of the inductance at each frequency.
Hi DAvid,

Sorry, time was up to change my post. Correct me if I am wrong but as far I know is the electrical resistance of an inductor in an AC circuit called an 'inductive reactance' and in a DC circuit a 'reactance'.
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Old 8th December 2012, 06:54 AM   #1877
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Originally Posted by Djim View Post
Correct me if I am wrong but as far I know is the electrical resistance of an inductor in an AC circuit called an 'inductive reactance' and in a DC circuit a 'reactance'.
Hi Djim,

The electrical reactance (not resistance) of an inductor in an AC circuit is called an 'inductive reactance' or reactive impedance.

The electrical resistance of an inductor in a DC circuit (or in an AC circuit) is called a resistance or resistive impedance (not 'reactance').

Reactance is a measure of the opposition of an inductor to a change in electrical current. The magnetic field generated in the inductor coil by the changing current acts to resist the change. Reactance does not apply in a DC circuit.

The impedance of an inductor coil at frequency f hertz is given by:

Z = R + j * X

where:

Z = complex impedance in electrical ohms
R = resistance in electrical ohms
j = imaginary operator sqrt(-1)
X = reactance in electrical ohms

and:

X = w * L

where:

w = 2 * pi * f in radians
L = coil inductance in henrys

R is the resistive or real component of the inductor’s complex impedance, and w * L is the reactive or imaginary component.

In Hornresp, R = Re and L = Le.

Kind regards,

David
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Old 8th December 2012, 07:08 AM   #1878
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Quote:
Originally Posted by GM View Post
FWIW, this example indicates an improper tap point WRT driver specs to me.

GM
Hello GM ,
I suppose yes, That is possibility .... Its a sim/measure graph comparison for a small TH based on the the miniature Anarchy sub driver ..... I didnt make it, it was someone else's project ........
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Old 8th December 2012, 07:14 AM   #1879
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Quote:
Originally Posted by epa View Post
when you double le value in that sim ,its much closer to the real thing.
i know pannelflex could play a part also.
id like to see some th comparisons between 1 watt and 100 watts,to see if amplitude plays a role here to.

For Epa , and David and folks who are following,

I have thrown together a few of my own simulated examples of smoothing due to increased LE ..... Some examples use 2x LE , and some use more like 3x or 4x the driver's LE ....
Its a few compact compact TH cabinets (ss15 with 15tbx100 and small TH with dual 8" mcm 55-2421s) , and also for fun i included a tapped pipe (transflex) type design ...... The smoother response in these examples is accomplished with the raised LE in the simulation but if built and measured the real world results can often be just as smooth with less series inductance added, or in some cases none at all when the "saddle" dip and peaks in hornresponse are mild to begin with.....
I assume some of the more extreme cases of ripple and dips would still require some amount of added LE to smooth them out just as Mr Danley does with some of his boxes by adding inductors in series with some of his drivers..
Attached Images
File Type: jpg 15TBX100--SS15.jpg (66.6 KB, 255 views)
File Type: jpg 18LW2400--TPIPE-209L.jpg (67.6 KB, 223 views)
File Type: jpg DUAL_MCM_55-2421_TH.jpg (68.0 KB, 213 views)
File Type: jpg LOMAX18-HUGE-TH-6mh.jpg (61.8 KB, 199 views)
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Old 8th December 2012, 07:31 AM   #1880
epa is offline epa  Netherlands
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hi matthew
if one would ad a coil to the system ,one also need to include the resistance of the coil.
that resistance wil have effect on it aswel

for pa you wil need a verry heavy (expencive ) coil
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Last edited by epa; 8th December 2012 at 07:42 AM.
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