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Old 23rd August 2007, 07:11 PM   #1
squib is offline squib  United States
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Default Need advice for 1st project (Aura NS3)

I'm planning to build a variation of Timn8ter's Aura PC Speakers. I've just received a pair of 3" PE drivers that look like black-coned versions of the Aura NS3-193-8A drivers, but noticed that the T/S parameters differ from the Aura specs. Fs is 100hz vs Aura spec'd 80hz and Vas is 0.03 cubic feet (0.85l) compared to Aura spec'd 1.25l.

Assuming the PE T/S parameters are generally accurate, will these drivers work reasonably well in Timn8ter's enclosure? I plan on using these for PC speakers in my office. They will be driven by a Sonic T-amp and will not be pushed very hard.

I'm attaching a couple of drawings of the enclosure I am planning on building. I've re-dimensioned Timn8ter's tall box to something a little shorter and deeper to better fit my desktop, but the gross volume is close (261 vs 264 cubic inches). They will by fashioned from 3/4" ply. Thanks for any help!

Squib
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Old 23rd August 2007, 10:22 PM   #2
squib is offline squib  United States
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Default more info

I should have clarified...Timn8er's original design was a BR enclosure measuring 12 (H) by 4(W) by 5.5(D) inches internally with a 1-inch diameter port of 3-inches in length. Here's a link - http://www.timn8er.com/Aurasound%20NS3.htm.
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Old 24th August 2007, 02:17 PM   #3
squib is offline squib  United States
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Default more drawings of my version

Here's another view of my attempted variation on the Timn8er design. My initial attempt to model my shorter and deeper variant in WINSID Pro shows a dip in output between 75 and 65 hz followed by a peak at Fb (60hz). I apologize if I rushed to post basic questions that I could answer myself. I'm struggling to contain my enthusiasm for my 1st build . I'll post a few more drawings for anyone interested in observing another newbie trying to find his sea legs...
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Old 24th August 2007, 02:20 PM   #4
squib is offline squib  United States
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Default office where the speakers will be used...

Sketchup is pretty addictive! This is a rough rendering of my office. I've posted it because of the cave-like ceiling and wall configuration that I assume will influence the low frequency output. There's just 2.5 inches of clearance between the top of my monitors and the ceiling. I'm on the third floor and the 1:1 roof pitch and low knee walls presented a lot of challenges in organizing the space. The ceiling has already been patched several times (from my taller colleagues standing up too quickly when sitting at my chair). There are some advantages to short stature.
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Old 24th August 2007, 03:21 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

It will work in a similar fashion as Qts for both drivers is apparently similar.

However the box to Vas ratio is such that you could easily use two
drivers arranged as a 4 ohm 0.5 way for baffle step compensation.

/sreten.
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Old 24th August 2007, 05:22 PM   #6
squib is offline squib  United States
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Default Thanks, sreten

Thanks for the comment. Perhaps I should consider ordering another pair of drivers and turn these into bipoles. I'm a little uncertain about the sound field from a rear facing driver, as it will be radiating directly at the 45-degree sloped ceiling rather than a vertical wall. Would placing both drivers on the front baffle be advisable? I assume that it would be preferable to roll the lower NS3 off so that only one radiator is reproducing the upper mid-range and treble...is this correct?

Squib
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Old 24th August 2007, 06:09 PM   #7
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The top driver would run full range and the lower driver would have an inductor only filter. Hard to say what the exact value of the inductor would be without doing some testing. 0.5mH perhaps?
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Old 24th August 2007, 06:37 PM   #8
squib is offline squib  United States
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Default Ahh,

"...the lower driver would have an inductor only filter. "

That's a filter I think I might be able to manage. Looks like another PE order is in my future. Too bad I didn't post these questions before placing my initial order, but I forgot to include binding posts anyways (I just noticed I forgot the binding posts on my sketchup model as well).

Thanks for the help,
Squib
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Old 24th August 2007, 11:23 PM   #9
squib is offline squib  United States
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Default 0.5 mH @ 4 ohm about 1250hz?

I'm assuming I should estimate the "crossover" frequency for the filter on the second driver based on 4-ohms. The drivers will be wired in parallel as per sreten's suggestion.
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Old 24th August 2007, 11:41 PM   #10
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Lots of assumptions without doing actual measurements. Baffle step should begin at around 2500Hz with a 5.5 inch wide baffle. The 0.5mH number was just a guess. It might be a lower value.
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