Did I make a good purchase? First time DIY. W12P from ApexJr - diyAudio
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Old 11th January 2006, 12:55 PM   #1
CFC is offline CFC  United States
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Join Date: Dec 2005
Location: H-Town
Default Did I make a good purchase? First time DIY. W12P from ApexJr

Hey guys,

Yesterday I bit the bullet and bought a W12P 12" woofer from ApexJr. It is a surplus from Hales Design group.
You can take a look at it over here in the middle of the page.

Here are its T/S specs:

Fs = 22Hz
Qms = 7.06
Qes = 0.374
Qts = 0.355
Vas = 4.78 cu. ft.
Xmax = 0.177"
Xmech = 0.266"
Sd = 113.2 sq. in.
Re = 3.6 Ohm
Znom = 4 Ohm
SPL = 91.37 dB (2.83V)
SPL = 87.9 dB (1W)

Modeling in WinISD Pro gave me a nice response using a QB3 alignment with an F3 around 26Hz or so and a 3 cu. ft box.
My main concern was the low Xmax, but I will be using a 70W sub amp, and again the modeling shows that it would hit just below the limit with SPL output around 100 db (much louder than I would ever hit). Was my thinking correct? That is the value I inserted in the "Signal" tab in WinISD.
Was this a wise choice for a first project? I figured I would start with something a bit more affordable to get my feet wet, but if in the process I build something decent then all the better .
What is "Xmech" by the way?

I appreciate any input.
CFC
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Old 11th January 2006, 01:25 PM   #2
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

Xmech is the mechanical limit of excursion, the driver is
linear within Xmax and then distorts its way to to Xmech.

Just my opinion but Fs is too low (Vas too high) to make
an ideal driver for reflexing, the result will not be too hot
at handling sub-sonic stuff - so if you use vinyl a subsonic
filter is a very good idea - hopefully built into the phono stage.

The driver parameters suggest its ideal use is as a sealed box
bass driver for a multiway speaker. Around 2 cuft will give a well
damped roll-off that can exploit room gain for good bass extension,
and as a low Q sealed box alignment excellent transient definition.

/sreten.
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