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Old 7th December 2010, 11:31 AM   #41
epa is offline epa  Netherlands
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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

Last edited by epa; 7th December 2010 at 11:35 AM.
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Old 7th December 2010, 04:20 PM   #42
jbell is offline jbell  United States
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Quote:
Originally Posted by epa View Post
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.....
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Old 7th December 2010, 04:36 PM   #43
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Jim;
Quote:
A 2:1 compression plate is a great idea
Can you explain?
Andy
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Old 8th December 2010, 09:28 AM   #44
epa is offline epa  Netherlands
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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.
Click the image to open in full size.



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
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Old 8th December 2010, 11:39 AM   #45
Xoc1 is offline Xoc1  United Kingdom
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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.
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?
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Old 8th December 2010, 12:03 PM   #46
epa is offline epa  Netherlands
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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)on the woofer to s2 its 10.5 cm *47 in the compromise version
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Old 13th December 2010, 10:32 PM   #47
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Originally Posted by epa View Post
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
Did you mean air core and 1.2mH like this one:
1.2mH 14 AWG Perfect Layer Inductor | Parts-Express.com ?
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Old 14th December 2010, 10:15 AM   #48
epa is offline epa  Netherlands
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Originally Posted by CRESCENDO View Post
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)
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Old 14th December 2010, 01:42 PM   #49
Xoc1 is offline Xoc1  United Kingdom
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Default 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!
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Old 14th December 2010, 03:03 PM   #50
epa is offline epa  Netherlands
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Originally Posted by Xoc1 View Post
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
Quote:
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!
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.
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