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Old 14th January 2012, 03:55 AM   #1371
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Quote:
Originally Posted by pinkmouse View Post


Chaps, if you give me a list of relevant posts and an appropriate title, I'll move them all over into a new thread. Fascinating discussion BTW, I'll be subscribing.
Although I would encourage continued response regarding multiple cabinet response in the new thread here:

Multiple Cabinet Combined Response

my preference would be leaving this thread as is, many of the posts refer to specific points by thread post number, once that context is broken it will be hard to follow if various posts are imported.

Art Welter
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Old 14th January 2012, 04:20 AM   #1372
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Quote:
Originally Posted by weltersys View Post
(why 15?)
Hi Art,

Fifteen rather than sixteen speakers were used because "during the outdoor measurements one speaker was immediately burned out in an effort to raise the SPL level above the background noise."

The speakers used in the tests were quite small.

Kind regards,

David
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Old 14th January 2012, 04:24 AM   #1373
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Quote:
Originally Posted by weltersys View Post
Test results are in a new thread:
Many thanks Art.

Kind regards,

David
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Old 14th January 2012, 09:16 AM   #1374
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by weltersys View Post
my preference would be leaving this thread as is, many of the posts refer to specific points by thread post number, once that context is broken it will be hard to follow if various posts are imported.

Art Welter
The post can be copied out and/or transfered out.

If post references are a concern then simply copy out the relevant posts.
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Old 14th January 2012, 02:07 PM   #1375
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Quote:
Originally Posted by sebDIY View Post
Pretty good article. It mentions the effect proximity to boundaries has on the Helmholtz frequency, as I said in post 1364. It was slighly off-topic, being about bass-reflex speakers, but it is interesting, nonetheless. It shows that the "length correction" phenomenon isn't limited to horns and transmission lines.
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Old 14th January 2012, 02:53 PM   #1376
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by David McBean View Post
Hi Djim,

Not sure if I understand how to interpret the measurements correctly.
Just to clarify, are these results saying that for constant input power:
With 2 speakers connected in parallel compared to a single speaker, the gain at low frequencies is +3 dB and the gain at high frequencies is approximately +1.5 dB?
With 4 speakers connected in parallel compared to a single speaker, the gain at low frequencies is +6 dB and the gain at high frequencies is approximately +3 dB?
If so, does this then mean for constant input voltage:
With 2 speakers connected in parallel compared to a single speaker, the gain at low frequencies is +6 dB and the gain at high frequencies is approximately +3 dB?
With 4 speakers connected in parallel compared to a single speaker, the gain at low frequencies is +12 dB and the gain at high frequencies is approximately +6 dB?
If so, then the measured results would appear to be consistent with the predictions of the existing Hornresp multiple speakers model.

Kind regards,
David
Hi David,

Indeed, Voltage constant gives steps of 6dB and Power constant should give 3dB, for each doubling. In my view the problem is not the counting or even the reading from the plots, it’s about finding the right acoustic theory. As long nobody finds the responsible mechanism for the change in coupling higher up, I would think twice to change anything in HornResp. With all respect to everybody’s measurements, in my view these plots should only be used for indication and/or conformation and should not be used as assumptions for ‘fine tuning’ the ideal model of HornResp.

However, maybe a simple ‘sensitivity' button for 1W/1m response, based on the lowest impedance within the bandpass, would be very helpful.

Thanks for HornResp as I find it a very inspiring tool!

Last edited by Djim; 14th January 2012 at 02:56 PM.
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Old 15th January 2012, 06:02 AM   #1377
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Quote:
Originally Posted by Djim View Post
However, maybe a simple ‘sensitivity' button for 1W/1m response, based on the lowest impedance within the bandpass, would be very helpful.
Hi Djim,

Could the required sensitivity information be obtained as follows, perhaps?

1. Use the Maximum SPL tool with Pmax = 1 and Xmax = 99 to generate the 1W/1m response.

2. Check the electrical impedance curve to find the lowest impedance within the passband.

3. Sample the 1W/1m response at the frequency of that lowest impedance, to find the sensitivity.

Or did you maybe have something else in mind, when referring to sensitivity?

Kind regards,

David
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Old 15th January 2012, 05:28 PM   #1378
Djim is offline Djim  Netherlands
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Hi David,

I'll try to explain myself. The problem is not that I can’t find the sensitivity figure. When people compare they normally use 2,83V/m which doesn’t represent their sensitivity figures. In other words they are comparing their drivers instead of the true performance of their designs. For myself the biggest problem is, I like to design based on sensitivity figures instead of Voltage. It is very time consuming since I have to recalculate every time I change a driver. Besides that, I prefer exact numbers. When I use the electrical impedance chart in HornResp it seems to use some sort of steps, when I manually search for its lowest point. I do agree you can find a near to lowest impedance point but it doesn't seem to be exact.

That’s why I would like to see a 1W/1m capability. For example, a choice between Eg or Sf (Sensitivity figure 1W/1m) in the 'Input Parameters' screen would make it very user friendly. The Sf should use the exact figure on the lowest impedance of the bandpass of the model.

Another idea is to improve the functionality of the 'Impulse Response' by making the impulses, frequencies variable. Although you can see more frequency detail in the 'Spectrogram' it still doesn’t show as much information you can get from an Impulse per frequency plot (Pitch Shift function).

Hopefully this explains my suggestions.

Last edited by Djim; 15th January 2012 at 05:31 PM.
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Old 16th January 2012, 07:44 AM   #1379
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Hi Djim,

Quote:
Originally Posted by Djim View Post
When I use the electrical impedance chart in HornResp it seems to use some sort of steps, when I manually search for its lowest point. I do agree you can find a near to lowest impedance point but it doesn't seem to be exact.
The sampling frequency resolution and hence the calculation of impedance at a particular frequency, is limited by the width of the chart in screen pixels.

Quote:
Originally Posted by Djim View Post
The Sf should use the exact figure on the lowest impedance of the bandpass of the model.
How is "bandpass" defined, and how is it determined? The exact figure for the lowest impedance is unlikely to be available - in Hornresp it would require the frequency to be at the exact position of a pixel.

Quote:
Originally Posted by Djim View Post
Another idea is to improve the functionality of the 'Impulse Response' by making the impulses, frequencies variable.
The method used to calculate and display impulse response in Hornresp was developed by Jean-Michel Le Cléac'h. You would need convince Jean-Michel that any change was worthwhile :-).

Personally, I quite like the Impulse Response tool the way that it currently is. The less user-adjustable variables the better, as far as I am concerned :-).

Kind regards,

David
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Old 16th January 2012, 02:17 PM   #1380
Djim is offline Djim  Netherlands
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Hi David,

Since they are ¼ WL systems the 'bandpass' is between 1/4WL and full wavelength I would think. If the lowest impedance is coupled to the graphic resolution instead of exact values, it is still better than having no option for sensitivity figures :-)
Does that mean you are considering such function? :-)
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