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Old 19th March 2011, 08:17 PM   #731
Djim is offline Djim  Netherlands
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Andrew, I made a correction of the two filter types... And as you can see it doesn't matter to the outcome. Instead of 7,5dB difference I stated earlier at 40Hz between the original SS15 and the extended, it is still would end in a 5,8dB difference in favour of the extended and that is almost twice the power...
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Last edited by Djim; 19th March 2011 at 08:34 PM.
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Old 19th March 2011, 08:57 PM   #732
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Quote:
Originally Posted by Brian Steele View Post
...and Klipsh was correct, IMO .

I'll bet that it can be modelled with Akabak. The topology looks similar to an idea I came up with for modifying a TH to remove the first notch in the output. Search for "Subwoofer Dogfood Duct" to see what I'm talking about. However, modelling it is one thing - coming up with an optimized alignment is another.

I'll bet that the shape of the exit has little to do with the overall FR in the effective passband (i.e. before massive cancellations and peaks show up in the output), and it can be replaced with an equivalent circular cutout.
Your bet would loose.
I tested many dozens of shapes, square, rectangular, "V", and "A" shapes, and varied the exit area of each shape. The differences between each shape and area were all quite measurable in their effect on frequency response both in and out of the pass band.

I did, in fact, try shapes with a close resemblance to the Karlson exit, they did not work as well as the upside down keystone shape.

The choice of the Keystone exit was by no means arbitrary, I have dozens of response curves that show the differences.

If you have more observations or questions regarding my designs, why not post them in one of the threads I started, as this discussion has little to do with the "SS15 challenge".

Tapped Horn Vs. Bass Reflex Case Study

Art

Last edited by weltersys; 19th March 2011 at 09:05 PM.
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Old 20th March 2011, 02:19 AM   #733
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by Don Snyder View Post
Need a little help, guys. I'm trying understand the finer points of how a HiPass filter affects the diaphragm displacement below the minimum displacement at 48Hz. I did a little work with HornResp and it seems to indicate that I can use a 32Hz LR HiPass on the SS15 and do minimum damage to the 40Hz signal. The d curve was plotted using the b-c intersection and the deflection at 16 Hz with 2 Watts (-24dB). I know that this could get dangerous if the SS15 deviates from the HornResp simmed values.
Don, I have checked your 32Hz about the SS15 and I found 33Hz but that is a minor difference. I modelled 3 types for safe filtering the SS15 and used Xmax as guideline for excursion.

One strange thing showed up and that is the difference between 24dB/oct and 48dB/oct Butterworth filtering. Both end up at the same frequency for the SS15 as you can see. I aspect if the cab had a lower Fs it would not longer end at the same frequency.

About the 'damage' your Linkwitz-Riley filter is causeing at 40Hz you can see in the graph in the right under corner. It shows more then 3dB 'damage' at 40Hz.

Also if you compare Linkwitz-Riley with Butterworth you’ll see the Linkwitz does harm the signal above its filter freq quiet a lot and how that results in the dropping of the excursion. However, if you are going to use eq at 40Hz for "make up for the damage" it is advisable to use higher settings as given.

I hope this answers your and maybe even more Jbells question.
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Last edited by Djim; 20th March 2011 at 02:31 AM.
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Old 20th March 2011, 03:12 AM   #734
jbell is offline jbell  United States
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Quote:
Originally Posted by Djim View Post
I hope this answers your and maybe even more Jbells question.
You know.... I never spent the time to check xmax with different HP filters... I just always assumed steepest slope at my desired cutoff. The stadiumhorn I used a LR48@40hz because it has a 40hz hump and that flattened it out, the SS15 I used a BUT48@40hz because the LR took too much of the already reduced 40hz out... But that's as much thought as I'd given it.

Looks like LR24@33hz would be a great option, and would let some of the filtered 'below 40' content add a bit to the cooling of the coil, and might be beneficial.

I think the ss15 is ending up being one of the most investigated/detailed DIY designs around.

Thanks to all.
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Old 20th March 2011, 06:11 AM   #735
Djim is offline Djim  Netherlands
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Originally Posted by jbell View Post
I think the ss15 is ending up being one of the most investigated/detailed DIY designs around.

Thanks to all.
Ending Jim? ......
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Old 20th March 2011, 07:52 PM   #736
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Forget this as SS contender (its about 1.5s), I just wanted your wisdom
regarding any benefit or penalty for starting a horn further back than the
1st tap?
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File Type: gif Box16-2.gif (165.1 KB, 853 views)
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Old 20th March 2011, 08:01 PM   #737
Xoc1 is offline Xoc1  United Kingdom
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Default Xoc 1 tweeks

I played around with the model / drawing that I posted in post 711.
This is as smooth as I can get with this layout - Horn shape emulates a quarter section of an ellipse so as usual Hornresp is an approximation
Overall height / volume is slightly more.
All parts layed out on a single sheet with no cutting allowances as Jbells
I envisage slightly deeper bass and more output from 60 to130 Hz
Have a look and see what you think!
Regards
Martin
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Old 20th March 2011, 09:37 PM   #738
Djim is offline Djim  Netherlands
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That looks like a real optimization to me Martin

(any ideas to fit the next attachment in?)

Last edited by Djim; 20th March 2011 at 09:42 PM.
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Old 20th March 2011, 09:40 PM   #739
Djim is offline Djim  Netherlands
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Hope they fix that server soon...
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Old 20th March 2011, 09:41 PM   #740
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Thanks guys, I learned lots about filters (but still have much to learn). Special thanks to EPA, Andrew & Djim. My drawing was not very accurate
but it did help define the problem.

Speaking of drawings, several people have asked for suggestions for CAD packages. I have used CADAM, UNIGRAPHICS and CATIA. In order to do
anything complex, the 2D packages require expertise in descriptive geometry. Currently, most Mechanical/Aeronautical Engineering students bypass the
descriptive geometry, and go straight to 3D CAD.

For home use, EasyCAD by FastCAD.com works for me. It allowed me to model Danley's LABHorn, including the compound flare in the throat. It is not
an easy program to master ... no CAD package is. If projections and descriptive geometry is in your field of expertise, use EasyCAD ... otherwise
look into SketchUp.
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