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Old 15th March 2011, 12:14 AM   #661
Djim is offline Djim  Netherlands
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JBell, concentrate on the 47-60 area (and your 40Hz rises with it). It will cost 1 or 2dB at 90Hz, but at full load you can gain 2 or 3dB around 50Hz. Two cabs together should make up the loss at 90Hz.

At hifi power your SS15 gives more low end. At PA power levels an 'mod' gives more SPL at <70Hz. In short range the SS15 gives best response, in >10m distances an 'mod' version should have a better response. The more cabs, the more the 'mod' will benefit.
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Old 15th March 2011, 12:51 AM   #662
tb46 is offline tb46  United States
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Hi Y'all,

Just fiddling with the parameters one at a time in the Wizard:

S1 - doubled = dip @ ~~160-210Hz gets larger; cut in half gets smaller; set to 1 looks best

L12 - doubled = ragged top end; halfed same area as in S1 improves; set to .1 dip @ 90Hz increases slightly

S2 - doubled = increase @ the very low end; dip @ ~~150-220 gets much larger, losses from 50-80Hz; cut in half: losses @ low end, peaking @70-80Hz, dip @~~150-220Hz gone, but peak in that area bigger

S3 - doubled = peak @ 50Hz, more output @40Hz, dip @160Hz increases, dip @210Hz decreases; cut in half: changes reverse

L23 - +50cm = better low end, lower SPL in the passband, dip @ 140Hz increases, dip @180Hz decreases (everything shifted down in frequency; -50cm = everything shifted upwards, looses more low end, dip now from ~~190Hz-280Hz

S4 - increasing area increases output in passband, but does not add to low end, improves first upper dip; decreasing area decreases output in passband, but does not affect area below 50Hz, big dip @170Hz

L34 - similar to L23

S5 - similar to S4, stays pretty even over a wide range for the SS15, e.g.: ~~1700-2500cm^2

L45 - "rotates" the dips around the first peak at ~~170Hz, longer = left dip decreases, right dip increases, shorter = left dip increasses, right dip decreases.

The 1st try at the Djim modification looks almost identical to the original SS15, maybe 1 dB lost @ 50Hz, and 1dB gained @200Hz.

Well, we are just fiddling.

Regards,
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Last edited by tb46; 15th March 2011 at 12:55 AM.
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Old 15th March 2011, 01:58 AM   #663
Djim is offline Djim  Netherlands
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Oliver, what was wrong with your mod from post # 581 ?
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Old 15th March 2011, 03:46 AM   #664
Djim is offline Djim  Netherlands
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These are my first suggestions, but I'm working on a third one with more accuracy. The left one works like this, path length extension but only for low frequencies (cause of the use of filling). You will have to experiment with the amounts of filling (density). You want only <100Hz waves using this extension.

Second one is more an experiment. If it works depends on how air molucules are behaving around the last bend. Because of the sharper bend I hope the speed will increase and waves make use of the longer path. The use of filling is like the same. You don't want >100Hz using the 'cavity' as resonators. No warranty if it will work as planned but I hope it takes away the dip upwards and change enough low freq that can benefit from the sharp corner. It could also work opposite since I have no tools to check 1/2 wave calculations. But the trick here is in the filling (probably quiet dense).

Black lines old situation, red lines mods, orange/brown acoustic filling...
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Old 15th March 2011, 06:05 AM   #665
Djim is offline Djim  Netherlands
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And here is the third one. Light grey is old situation, blue is optional. No expansion in those short distances for easy building (wont change the output anyway) Yes sir, all hand drawn with paint... bunkers!
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Last edited by Djim; 15th March 2011 at 06:07 AM.
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Old 15th March 2011, 07:03 AM   #666
Djim is offline Djim  Netherlands
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If you wanna have it more radical, this one has no 2x 90 bends facing, last bend is almost 180 degrees and you have a little more control over the last expansion. Only needs one bracing stud for the bottom panel since all other outside panels have bracing. As you can see haven't worked it out and no idea if it fits the one sheet challenge.
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Old 15th March 2011, 11:36 AM   #667
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Default If this works well...

Quote:
Originally Posted by Djim View Post
If you wanna have it more radical, this one has no 2x 90 bends facing, last bend is almost 180 degrees and you have a little more control over the last expansion. Only needs one bracing stud for the bottom panel since all other outside panels have bracing. As you can see haven't worked it out and no idea if it fits the one sheet challenge.
This would make for a very fast and easy build! Much appreciated by those of us with limited tools / skills.

Regards, Ben
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Old 15th March 2011, 01:46 PM   #668
jbell is offline jbell  United States
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Quote:
Originally Posted by Djim View Post
If you wanna have it more radical, this one has no 2x 90 bends facing, last bend is almost 180 degrees and you have a little more control over the last expansion. Only needs one bracing stud for the bottom panel since all other outside panels have bracing. As you can see haven't worked it out and no idea if it fits the one sheet challenge.
Not sure what you mean by no 2x90 degree bends??
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Old 15th March 2011, 02:01 PM   #669
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Default Isn't it...

...virtually only 90 degree bends (and multiples thereof)?

Regards, Ben


P.S. JBell - you were right, lying on their sides on the floor with bottoms touching is excellent! Seriously outperformed the first time when they were split and upright, despite being much further from walls than before!

The promoter said he finally understood why the damn things (stadium horns) were so big and heavy!

Last edited by salzburgsoundsystem; 15th March 2011 at 02:15 PM.
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Old 15th March 2011, 02:07 PM   #670
tb46 is offline tb46  United States
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Hi Djim,

Post #663: "Oliver, what was wrong with your mod from post # 581 ?"

- Nothing in particular, as I said, I like it (with and without the wiggle in the back horn section) but it is bigger than the SS15, not a single sheet box.

Post #664: "...path length extension..."

- Does not work with this driver, yours kills the region from ~~130-210Hz, does not add much below 45Hz, and looses output from ~~50Hz-80Hz. As you are indicating, with this type of construction you are back to build-test-modify, and guess again. What seems to help consistently with this driver is to reduce the L12 distance, and/or reduce S1, or couple the driver as closely as possible to the throat (S2).

I don't know if soho54 could model something like the ones in #664/665/666 in AkAbak. I did a complete fold similar to #666 to find room for a chamber to house Helmholtz resonators close to the throat, but again, that would belong into a different thread.

Keep on trying, I'll try to fire up AkAbak for the SS15, but I don't have any hope for extending the low end response within the parameters of the project.

Attached is a quick try at your modifications (driver board/throat extension) in Hornresp.

Regards,
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File Type: jpg Djim_throat_baffle_mods_2011_Mar15.jpg (32.6 KB, 332 views)
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