C/E/X PA Flat to 30 (FT30) PA TH Awesomeness

i disagree that the bottem piece wont acomplish much.
it stiffens the bottem shelf like a woodem beam stiffens the floor.
but only works wel if the mouth is braced properly.
a grill is a good way to do that,whitout creating problems placing the driver.
btw imo one could use thinner pieces fot bracing like 10 or 12 mm,pressure being equal both sides of the brace(again imo)

any thougts about using a slot opening at the throath vs an open baffle like the pics 2 posts back?
a slot seems 2 extend bw a bit
 
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i disagree that the bottem piece wont acomplish much.
it stiffens the bottem shelf like a woodem beam stiffens the floor.
but only works wel if the mouth is braced properly.
a grill is a good way to do that,whitout creating problems placing the driver.
btw imo one could use thinner pieces fot bracing like 10 or 12 mm,pressure being equal both sides of the brace(again imo)

any thougts about using a slot opening at the throath vs an open baffle like the pics 2 posts back?
a slot seems 2 extend bw a bit


true, with grill -- the bottom brace helps, without grill you want the front braces I drew.

A 2:1 compression plate is a great idea, especially if you are going to run it down to the absolute maximum low freq of the box. Scott runs that way in the furysub, and says it keeps the driver from unloading as quick below Fc. And this box is targeting 28-32hz.....
 
ok ,hr predicts some high extention.
the unoupling bit hr doesnt predict,good to have experiance around:)
here is the comparison.open baffle flatter,slot more bw.
baffle.jpg




pyros
compression ratio means this:
say a speaker has an sd(sq cm of the cone and surround that actually moves the air)of 1000,a ratio 2:1 =500,3:1= 333 4:1=250 ect
 
I,m really unsure if this baffle mod is necessary?
Increasing the compression gives more top end at the expense of bass extension. Shortening L12 increases the bass extension.:yinyang:
There might be a case for trying this as a development modification on a prototype.
I,m concerned about placing any extra loading on the driver.
ScreamerUSA seemed to find that the extra restriction of the baffle plate increased the power handling. In this case we are usng a more capable driver, and trying to shift more air. Is an extra restriction going to help achieve the bass response that Crescendo wants?
 
well according 2 hr it gives only extension upwards,but jbell's remarks about the unloading bit comes from experiance.
more reason to bild a test moddel 1st.:)

btw compression rate is about the same ~2.2:1
when we go perpendicular(how does one spell this:confused:)on the woofer to s2 its 10.5 cm *47 in the compromise version
 
Did you mean air core and 1.2mH like this one:
1.2mH 14 AWG Perfect Layer Inductor | Parts-Express.com ?

no ,i meant 1.2 mm dia.
converted to gauche/awg that means awg 16.


Jantzen 4.0mH 15 AWG Air Core Inductor | Parts-Express.com

this one is the only one @ parts express.

but for testing you could try awg 18
4.0mH 18 AWG Perfect Layer Inductor | Parts-Express.com
dont let the watts fool you.
this doesn't realy apply in real live situation in this configuration.
you can test it by aplying full load for an hour ,and find out how warm
the coil gets
if it gets over 80 degrees cecius its getting 2 warm
then you need thicker wire(lower awg nr):)
 
Questions, Questions?

EPA What do estimate the Le of the BMS 18N850 v2 driver to be in the passband of the TH. The spec states 0.89 mH at 1k is that likely to be more at 30 to 100 hz?
Would the 0.72 ohms DCR of the 15 AWG Jantzen coil be added to the Re value, in the same way as its inductance is added to the Le? if so this reintroduces a curved response in the passband.:(
Would the largest 14 AWG coil at 2.5mH and 0.38 ohm not give a better overall performance, assuming that the inductor is needed at all!:confused:
 
EPA What do estimate the Le of the BMS 18N850 v2 driver to be in the passband of the TH. The spec states 0.89 mH at 1k is that likely to be more at 30 to 100 hz?
yes but marginal
Would the 0.72 ohms DCR of the 15 AWG Jantzen coil be added to the Re value, in the same way as its inductance is added to the Le? if so this reintroduces a curved response in the passband.:(
Would the largest 14 AWG coil at 2.5mH and 0.38 ohm not give a better overall performance, assuming that the inductor is needed at all!:confused:
actually verry good point.
didn't sym the re of the coil with it.
so (if needed)your suggention makes sence.
so if the box is bild ,then if needed start with a lower vallu and thicker wire.
:)
 
EPA
To clarify the point I asked the best way to simulate this in the Hornresp thread. (Post 1500)
http://www.diyaudio.com/forums/subwoofers/119854-hornresp-150.html
General consensus is that the coil resistance should be added to Rg, and the coil inductance added to Le...
This does make a difference.
Screenshot shows sim in post 21 with 4uH 0.72R inductor in grey and 2.5uH 0.38R inductor in black.
Maybe a tweak to the design is in order? Assuming that Crescendo hasn,t committed anything to a build yet! :eek:
 

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EPA
To clarify the point I asked the best way to simulate this in the Hornresp thread. (Post 1500)
http://www.diyaudio.com/forums/subwoofers/119854-hornresp-150.html
General consensus is that the coil resistance should be added to Rg, and the coil inductance added to Le...
This does make a difference.
Screenshot shows sim in post 21 with 4uH 0.72R inductor in grey and 2.5uH 0.38R inductor in black.
Maybe a tweak to the design is in order? Assuming that Crescendo hasn,t committed anything to a build yet! :eek:
yes i saw the difference.
the 2.5 mh syms better.
its strange that adding resistence should interfere with the freq responce in that way,but its the general concencus.
dont think we need to tweak the design.
most of us think that responce wil be flatter anyway.
imo the coil is the last thing to worry about if needed at all.
it can always be added later.
 
i mean something like this.;)
filter%20justin.jpg

this is actually used in hifi x-over networks.
with this you wil loose amp power.
remember that loosing some db's in the middle of the passband,you gain on low and high end
you be better of using a eq. to flatten it.

again if nessecerry at all.
 
Nope, haven't committed yet. Am anxious, but I'm being patient til all is clear and the go-ahead is reinforced :)

Also, what material is recommended for the grill? Any pictures or part #'s?
how are thing's justin?

i am just anxious :emoticon:
jason and i like to see some wood chips:smash::D
what are your plans for the betabox bild.?




i got a piece of 1.8mm(.0709 inch) steel grill ,that's strong enough for some drunk ashole kicking it,and it doesn't resonate easy(provided its mounted securely).
 
how are thing's justin?

i am just anxious :emoticon:
jason and i like to see some wood chips:smash::D
what are your plans for the betabox bild.?




i got a piece of 1.8mm(.0709 inch) steel grill ,that's strong enough for some drunk ashole kicking it,and it doesn't resonate easy(provided its mounted securely).

Things are good - just preparing music for my gig on NYE.

Since I'm a novice when it comes to building prototype enclosures, I'm open to any suggestions. I'm leaning towards 3/4" birch w/proper bracing, PL adhesive (of course) and that aluminum security screen door idea sounds like somethin to check out. The 18N850v2 is $100 more than I was thinking this whole time. It'd be nice to find some lightly used drivers, but I haven't been able to locate any.
 
Things are good - just preparing music for my gig on NYE.

Since I'm a novice when it comes to building prototype enclosures, I'm open to any suggestions. I'm leaning towards 3/4" birch w/proper bracing, PL adhesive (of course) and that aluminum security screen door idea sounds like somethin to check out. The 18N850v2 is $100 more than I was thinking this whole time. It'd be nice to find some lightly used drivers, but I haven't been able to locate any.
the bms 18n850v2 is €361.- on this side of the pond.
maybe use the b&c u sugested a wile ago.
i wouldn't use a alu grill,remember its to brace the side and bottem pannel.
i think in this case 1 kilo extra shouldn't be a problem.