C/E/X PA Flat to 30 (FT30) PA TH Awesomeness - Page 4 - diyAudio
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Old 4th December 2010, 06:05 PM   #31
Xoc1 is offline Xoc1  United Kingdom
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Crescendo
I see that you would like a width of 24" external. I assume that you would be using 18mm (3/4") birch ply for a PA cabinet so this would give an internal width of 572mm (22.5 in). Also I see that the you have a preference for the 550 litre cabinet. Please note that in practical terms the real cabinet might have a lower response and efficiency due to the volume of the driver in the horn mouth, which is something that is probably not completely taken account of in the sims.
I,m not completely convinced about using an inductor to flatten the passband response. I think we will struggle to find an inductor that will be satisfactory at the sort of power levels your looking at.
BTW would you be using the QSC PLX RMX amplifiers in 4 ohm bridge for a pair of 8 ohm drivers? This gives 1700W per driver for the PLX3402 and 1200W per driver for the RMX2450.
I assuming that this is the way that you want to go forward with this and that you are probably looking at a pair of cabinets to start with.
I think we need to nail your requirements before setting out a final folding scheme. Once that is complete a physical prototype might be in order
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Old 5th December 2010, 09:29 AM   #32
epa is offline epa  Netherlands
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he back again.as expected infection was spread severly and they had to remove my hearbones,meaning my hearing is not getting better(one side)
it wasn't good anway,but stil a dissapointment.
stil a lot of pain and groggyness.but i wil be ok again.

i agree wth xco1 bilding a test moddel.
looking at the ss15 th of jbel id say use 15 mm birch ply for the actual moddel,just use bracing in the mout bit and the flappy ends.
u can always put a coil in series later if u want but you must use an aircoil(no ferrit coil)1.2 mm minnimum.
time for sawdust
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Old 5th December 2010, 11:52 PM   #33
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"I see that you would like a width of 24" external"

24" width external or less (two cabs side by side equaling 48") or 48" tall external or less (loading the cabs sideways in the truck) are just optimal dimensions as they will be less hassle to take in an SUV.

"I assume that you would be using 18mm (3/4") birch ply for a PA cabinet"

Xoc1, what do you think about using 15mm birch w/bracing?

"Please note that in practical terms the real cabinet might have a lower response and efficiency due to the volume of the driver in the horn mouth, which is something that is probably not completely taken account of in the sims."

What would you recommend - or is this just a heads-up?

"BTW would you be using the QSC PLX RMX amplifiers in 4 ohm bridge for a pair of 8 ohm drivers?"

I will be using whatever amp is suitable for the cabs; but, yes - the plan was to wire the cabs parallel and run the amp(s) 4 ohm bridged.

"I think we need to nail your requirements before setting out a final folding scheme."

Let me know if there's any more info you need

"he back again"

Glad to have you back - safely. Too bad to find out they had to be removed. Hope the pain reduces quickly.

"i agree wth xco1 bilding a test moddel."

I'm all for building a test model. Would I be building the enclosure like normal (with poly adhesive), just minus the braces?

"looking at the ss15 th of jbel"

What ss15??

"u can always put a coil in series later if u want but you must use an aircoil(no ferrit coil)1.2 mm minnimum."

I'll start the coil research

Last edited by CRESCENDO; 6th December 2010 at 12:00 AM. Reason: clarity
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Old 6th December 2010, 06:33 AM   #34
epa is offline epa  Netherlands
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feeling better 2day
ss15 =single sheet tapped horn of jbell.
he uses 12 mm wood(dont know if its birch ply).
this is why i think 15 mm will do fine wih some bracing.
also 15 mm is 20% lighter than 18 mm.
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Old 6th December 2010, 01:12 PM   #35
Xoc1 is offline Xoc1  United Kingdom
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JBells Large TH used 18mm (3/4") Ply.
As was Wood1y,s RCF 15" TH....
Dare I say that a Danley TH118 is 18mm Birch Ply
I think that ScreamerUSA Furybox is also 18mm (But failed to find a specific reference)
As this project is about reaching 30Hz and high power levels, I would say that 18mm might be prudent. 15mm might be possible dependent on your cabinetry skills, and how much time you are prepared to dedicate to bracing the cabinet without causing any adverse effects.
I know of a double 15" FLH design that works well in 15mm birch ply, but it is far more complicated than this TH, and the double horn construction avoids having an unbraced side to the horn mouth.

epa
wishing you a speedy recovery from your operation.
My partner had a similar procedure on one of her ears a couple of years ago, and despite the hearing loss still appreciates good music, and the differences when I improve our home soundsystem using the fantastic amount of knowlege available here on Diyaudio
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Old 6th December 2010, 01:49 PM   #36
jbell is offline jbell  United States
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fast healing epa.

The ss15 isn't a 30hz box, it's a 45hz box. It is loud and a great PA performer, and makes 40hz with authority in pairs. A few mods could get it to about 35hz, but I think solid 28hz, and 32hz d&b notes are non starters for this design. With a grill, the ss15 really doesn't need any additional bracing, even though it is built with 1/2" ply. My personal rule of thumb is that any panel over 12" -- needs some kind of bracing. In the ss15, that only applies to the top, back, and bottom panels. My limited bracing accomplishes everything needed except for the mouth.

The 'compromise' plan from earlier in this thread looks good. Basically an extra fold for the stadiumhorn. I find that the TH's I build play just a bit lower than I expect, so the compromise design that doesn't quite get to the desired low end cut -- is usually right on target.
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Old 6th December 2010, 02:38 PM   #37
epa is offline epa  Netherlands
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thnx all
i have no ideer what 2 expect from a hearing aid,but if your partner hears improvements,thats a bit comforting i gues tnx.

for thicknes one could use 15mm and use more bracing,or use 18 mm with less bracing.i think its up to the constructor.
i think jbells argument of max 12"spacing makes sence .
in our "compromise" moddel that means top, back and bottem
its up to justin now to choose a design and thicknes,knowing that the actual design wil be a few hz lower and less efficient then predicted in hr.
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Old 6th December 2010, 03:23 PM   #38
epa is offline epa  Netherlands
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bracing like this??Click the image to open in full size.
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Old 6th December 2010, 03:31 PM   #39
jbell is offline jbell  United States
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hollow out your bracing. (big holes) Solid bracing reduces low end output (in cabinets I've built) I don't think your 'bottom' brace will accomplish much, better to grill or put a couple of vertical braces and a horizontal brace right at the mouth opening
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Last edited by jbell; 6th December 2010 at 03:45 PM.
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Old 6th December 2010, 03:38 PM   #40
epa is offline epa  Netherlands
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Quote:
Originally Posted by jbell View Post
hollow out your bracing. (big holes) Solid bracing reduces low end output (in cabinets I've built) I don't think your 'bottom' brace will accomplish much, better to grill or put a couple of vertical braces and a horizontal brace right at the mouth opening
done
a strong gril like your ss15 is a good ideer

Last edited by epa; 6th December 2010 at 03:40 PM.
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