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Old 1st June 2013, 03:24 AM   #931
xrk971 is online now xrk971  United States
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Any pics Chaz? Are you doing 4 horns?
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Old 1st June 2013, 04:26 AM   #932
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I tried 2 horns, and I would still appreciate if you can sim that other model at some point. Having trouble getting these test cabinets to seal up right now for a proper test. probably no results until tomorrow...

By the way, no build pics because my phone cam is not working, but I'll post some finished pictures soon.


EDIT: rrrrrr, the horn output is there, down to 40hz, but way, way down in level. Like I said I'm not sure if I'm getting a good seal and the styrofoam is falling apart around the driver. I don't think the foam insulation is any good for this sort of work. I will have to make some fresh cabinets using wood baffles.
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Last edited by chazdrumzalot; 1st June 2013 at 04:52 AM.
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Old 1st June 2013, 11:41 AM   #933
xrk971 is online now xrk971  United States
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Chaz,
I should get to modeling your design later today. Are you using the extruded polystyrene (xps) which is like egg carton material or styrofoam balls brittle stuff? The xps is what you want and you need a thin plywood support around a heavy driver like the w5-1611. Good luck sealing it up.
40 hz is great if seals. The design should achieve about 10 dB of gain in bass at tuning freq.
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Old 1st June 2013, 03:37 PM   #934
xrk971 is online now xrk971  United States
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Default Sim of Chaz's rectangular double horn Cornu

Chaz,
Based on the dims you gave me for your double horn rectangular (48 in tall x 24 in wide x 4 in deep) double horn Cornu design, I built the model and ran the simulation in AkAbak using the TB W5-1611 driver (with measured T/S params as published on PE Techtalk). The design has very deep bass extension down to 40 Hz, but it is depressed compared to the output from 100 to 500 Hz. You will have really big peak at 300 and 400 Hz. The sims are for 1 watt input, 3 meters away, driver at 1.2 m above floor, horns exiting upper left, and bottom right horizontally as you requested. The black curve is total horn and driver radiator combined, red is bottom right horn (floor enhancement visible) and green is upper left horn output. The second plot shows what I tried doing to improve the performance: double the depth to 8 in and it helps to enhance the bass shelf. So one way you can save this project is to build a second set of channels on the back of your speaker, cut a hole to connect both sides and seal it up with a back plate. Additionally, you can add a simple square shaped conical horn of 11.5x11.5cm throat 20cmx20cm mouth, 7 cm deep and it will balance things out nicely.
Good luck and let me know how your measurements compare. Important to place at 1.2m height with 3 meter mic position for good comparison.
Attached Images
File Type: png Cornu-2P-Chaz-Freq-4inch.PNG (26.6 KB, 292 views)
File Type: png Cornu-2P-Chaz-Freq-8inch-Fronthorn.PNG (27.1 KB, 292 views)
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Old 1st June 2013, 03:38 PM   #935
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Thanks xrk. I think I'm just going to trash this cabinet as anyway it's just so ugly and cumbersome (and it's littering my house with little bits of styrofoam). This was a particularly inelegant way of trying to achieve 35-40hz! I would rather just construct the thing out of wood or even hardboard after this mess. If you can help me get the 2-horn design dialed in then I think I can get around to making it next week.

I made the baffles using this stuff, albeit only 1/2 inch thick:

R-Tech 1-1/2 in. x 4 ft. x 8 ft. Foam Insulation-310880 at The Home Depot

This time I'll start with a 4-pack of 2'x4' hardboard and then attach a cherry or walnut veneered baffle if the results deserve it.

EDIT: oops, I posted this while you were posting. give me a minute to digest those sims...
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Last edited by chazdrumzalot; 1st June 2013 at 03:43 PM.
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Old 1st June 2013, 03:47 PM   #936
xrk971 is online now xrk971  United States
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Chaz,
I think your design can work if doubled in thickness, or go back to 4 channel as I modeled for you earlier as 3x3 ft. You used the wrong foam (eps). What you want is the pink xps stuff here Owens Corning Foamular 1/2 in. x 48 in. x 96 in. Squared Edge Insulating Sheathing-36L at The Home Depot
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Old 1st June 2013, 06:21 PM   #937
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My conclusions are as follows: after seeing a 3'x3' panel, I don't think I could possibly pursue that option until I get a larger space. The same goes for an 8" deep speaker. Looking at the 2 horn design, let me ask some questions: would widening the horn throats help matters at all? What about constricting the horn mouth?

Can we try this? Maintain 4" depth, Expand chamber volume to ~4 liters, and remove the first two horn sections, therefore start with a 1.75" wide mouth. Segments are now:

width length
1 3/4" 8"
2" 11"
2.5" 13"
3" 16"
3.5" 19"
5" 21"

total length ~7.5ft or 1/4 37hz

any improvement, or heading in the wrong direction?
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File Type: jpg cornu 2x3 ft .jpg (703.7 KB, 288 views)
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Old 1st June 2013, 10:29 PM   #938
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Chaz,
I'll see what I can do to tweak your 24x48 double horn. It will probably have to grow to 5 in depth as 4 is just too small for a 5.5 in class driver. Are you opposed to a front horn due to WAF? Because that helps a lot.
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Old 2nd June 2013, 03:04 AM   #939
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I appreciate your help, xrk. I'm not totally opposed to a front horn, but what I'd really like is a horn that has good extension but doesn't generate such excessive mid bass. I'm not totally clear yet on what elements of the horn need to change in order to achieve this, but I don't mind adding an inch of depth.
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Old 2nd June 2013, 12:36 PM   #940
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Chaz,
I tried constricting the throat, closing off the mouth, adding a throat upstream of the mouth, changing chamber volume. Nothing will really get rid of the mid bass peaks as well as rotating speaker 90 deg, adjusting height, and adding front horn. The extension in bass goes to 35 Hz but it starts a slow falloff from 70 Hz. That's about all you can do to improve things. Final config is 5 in depth, 3 liter chamber vol, 11.5x11.5 cm thoat by 20x20 cm mouth x 7.5 cm deep front horn. Mount at 1.1 m above floor.
Attached Images
File Type: png Cornu-2P-Chaz-Freq-5inch--90deg-Fronthorn.PNG (26.8 KB, 255 views)

Last edited by xrk971; 2nd June 2013 at 12:45 PM.
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