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C/E/X PA Flat to 30 (FT30) PA TH Awesomeness
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Old 17th May 2011, 05:31 PM   #301
m R g S r is offline m R g S r  United States
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Pyros yes this box will do a lot more damage than the one you built. When you are pumping 3kw through a powerful driver stuff is bound to vibrate!
I'm not going to be running that much power but hey ya never know What the future brings. Might as well build up the box right the first time!!
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Old 17th May 2011, 10:23 PM   #302
Xoc1 is offline Xoc1  United Kingdom
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Quote:
Originally Posted by Djim View Post
To be honest I think those 2x13mm can have more effect (positive or negative) to the LF response then all corner bracing together...
I,m having a go at putting together an AkAbak script to sim the extra area near the mouth. I,ve got the script to work with a couple of extra sections, one being a negative taper, - just need to punch in the numbers
Maybe tomorrow..... I,m too tired now!
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Old 18th May 2011, 12:08 PM   #303
4pyros is offline 4pyros
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Quote:
Pyros yes this box will do a lot more damage than the one you built. When you are pumping 3kw through a powerful driver stuff is bound to vibrate!
I'm not going to be running that much power but hey ya never know What the future brings. Might as well build up the box right the first time!!
Ya just woundering if I should put in extra bracing befor I seal up my boxs. Andy
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Old 18th May 2011, 09:51 PM   #304
Xoc1 is offline Xoc1  United Kingdom
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Default Akabak Analysis TH18

Hi
Results of 6 segment sim in akakak adding the extra area unaccounted for in the hornresp sim. As discussed in posts 292 & 293
The screengrab shows the data used and the resultant sim labelled TH18PDM
The TH18PD graph shows the 4 segment sim as exported from Hornresp - with the path length adjusted to take account of adding all the corner reflectors.
Driver is still the PD1850 but results are presented for comparison of the response curves.
The rest of the horn is as linear as I could acheive, with no great descrepancies from the horn taper.
Overall the result is a slightly smoother response - half a dB down at 45hz
and 1 dB up at 30Hz.
I suppose this is the effect that might be expected by adding a small bandpass chamber.
Regards
Martin
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File Type: jpg TH18 AkAbak 6 Segment.jpg (437.7 KB, 452 views)
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Old 18th May 2011, 10:52 PM   #305
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Xoc1 View Post
Hi
Results of 6 segment sim in akakak adding the extra area unaccounted for in the hornresp sim. As discussed in posts 292 & 293
The screengrab shows the data used and the resultant sim labelled TH18PDM
The TH18PD graph shows the 4 segment sim as exported from Hornresp - with the path length adjusted to take account of adding all the corner reflectors.
Driver is still the PD1850 but results are presented for comparison of the response curves.
The rest of the horn is as linear as I could acheive, with no great descrepancies from the horn taper.
Overall the result is a slightly smoother response - half a dB down at 45hz
and 1 dB up at 30Hz.
I suppose this is the effect that might be expected by adding a small bandpass chamber.
Regards
Martin
I think you are right there. It's only a pity Akabak doesn't have the ability to show how the design would be influenced when the driver is loaded with max power. Nice work again Martin
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Old 19th May 2011, 12:04 AM   #306
djk is offline djk
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"It's only a pity Akabak doesn't have the ability to show how the design would be influenced when the driver is loaded with max power"

What do you mean?

AkAbak models excursion.
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Old 19th May 2011, 12:41 AM   #307
Djim is offline Djim  Netherlands
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Originally Posted by djk View Post
"It's only a pity Akabak doesn't have the ability to show how the design would be influenced when the driver is loaded with max power" What do you mean? AkAbak models excursion.
Hi Djk, HornResp also models excursion but the reality shows something different (and I don't mean pwr compr).
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Old 19th May 2011, 02:05 AM   #308
djk is offline djk
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I missed the details of what you are referring to, where can I find them?
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Old 19th May 2011, 02:45 AM   #309
Djim is offline Djim  Netherlands
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Iíll try to make it more concrete for you. If you build a TH design based on a sim you will see that the LF output differs from the prediction. I donít mean the overall SPL differences (these can be explained) but specific differences in the LF part of the band pass. Often this results in less SPL at Fb (1/3WL) in return for less steep roll-off. I know the problem looks similar to Martin findings in post # 304 which is why I mentioned it. However, the models we used were optimised like Martin did but we still face the same 'problem' in reality every time again. I don't think HornResp or Akabak can model that.

But we made another observation. When you power the thing on more serious levels (3.2kW) you see the usual LF SPL drop below 2/3WL as part of power compression. However, it also looks like Fb is starting to drop in frequency a little. If we use different drivers with half AES power ratings we didnít see this 'drop'. No we are trying to figure out if it is related to:
1.) Specific drivers (problem - we only have one type that can handle such power)
2.) Some kind of logarithmic type of rising in absorption vs power trough panel flexes (this looks the most likely to me).
3.) If it is possible it has something to do with the changing of air mass by the higher pressure.

And I don't think you can model that either in Akabak Anyway, what sounds more logical to you Djk, or have you other ideas?

Last edited by Djim; 19th May 2011 at 03:14 AM.
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Old 19th May 2011, 07:57 AM   #310
NEO Dan is offline NEO Dan  United States
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40Hz horns with $700 usd drivers? If 40Hz is all you are after why not stick with more of the efficient SS15's, but use better/more cost effective drivers?

If 140dB & 30Hz extension is the goal I think you will need 4 cabinets of a different design.

Why is there no model of the 18sound driver?
Also why are the sections set to conic, that should be parabolic right?
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