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Old 5th May 2005, 08:10 PM   #1
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Default Anyone measure the Atlas 12 yet

OK ordered four Atlas12 and can't wait to install them in my pair of dipole cabinets.

Does anyone know how high in frequency these Atlas 12 can be used.
With the light cone and low Le, I would think they could be run up to 250 hz easily unless there is a cone breakup mode.

I will be using these Atlas 12 with a Fostex FX120 or Adire WR125s fullrange driver on an open baffle and would need to crossover in that range.

JM
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Old 5th May 2005, 08:18 PM   #2
simon5 is offline simon5  Canada
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I know he must be busy, but you should call Chad to ask about that. I think it will be ok to crossover at 250 Hz.
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Old 5th May 2005, 08:36 PM   #3
DcibeL is offline DcibeL  Canada
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Yes I'm sure 250Hz would be just fine, but why?
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Old 5th May 2005, 09:22 PM   #4
Tweeker is offline Tweeker  United States
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The red line on the chart is the closest one to your situation, is the .52 qts in a very large 11.4cu foot sealed box. This is alignment has a box volume over 2.5 * vas, well on its way to infinite baffle, especially given the frequency. Be sure your cabinets dont act as transmission lines at these frequencies, it can lead to very lumpy response.

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Old 6th May 2005, 12:32 AM   #5
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I was just wondering if anyone has actually measured the response (not simulated) above 100 hz to know if there are cone resonances.
My dipole cabinets are half way between an H frame and U frame. The backs are heavily stuffed with fiberglass to hopefully damp resonances like Tweeker warned of.

I will post a pict when I get the drivers.

My plan is to use the dipole cabs from about 250 hz down to 50 hz and use a conventional sealed or vented box from 50hz and below.
I think Linkwitz also suggests this on his site.

I need to run the woofers up high enough to avoid stresssing the full range driver also planned for an open baffle.

JM
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Old 6th May 2005, 01:31 AM   #6
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Quote:
With the light cone and low Le, I would think they could be run up to 250 hz easily unless there is a cone breakup mode
Our testing indicates that the Le is almost 3 times higher than the published spec.
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Old 6th May 2005, 01:53 AM   #7
simon5 is offline simon5  Canada
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Interesting... I hope Chad will be available soon to comment this.
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Old 19th May 2005, 09:16 PM   #8
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Well I got my four Atlas 12's and put a pair each into my 3 cf sealed boxes.
The walls of the boxes are lined with high density fiberglass glued on with silicone. The cavity is not stuffed. I hooked them up in parallel and drive them with my adcom amp. They are fed from an active crossover off my receiver's preouts. I cut them off at 90hz.

What I heard was muddy, one note bass. Very dissapointed. They are not nearly as good as single NHT 1259 for comparison. I also compared them to a pair of 10" audax drivers that were originally in the same cabinets and the Audax were cleaner and more musical, but did not have the xmax needed to play as loud.

I tried the different Q configurations which you can adjust with the second VC, but this did not clear up the 1-note sound. I also tried to load them aperiodically by drilling some small holes in the box, but no improvement. I also tried them in a dipole cabinet, but the 1 note sound persisted.

Maybe these drivers are better suited as a car subwoofer (thumper)? They are very attractive drivers and appear well made, but they seem to have a very stiff suspension to my manual prying.

I was hoping to use them up to 200hz but this would be out of the question from what I heard.

I hope that I can return these.


JM
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Old 19th May 2005, 09:37 PM   #9
SY is offline SY  United States
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Yow! Two of these stuffed into a 3 cu ft cabinet seems excessive. The Vas is about 128 liter (call it 5 cu ft). For two drivers, that's nearly 10 cu ft. With a Qts of 0.5, that makes your Qtc...

I think I know why they're boomy.
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Old 19th May 2005, 10:28 PM   #10
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In low Qts mode they are suppose to have a Qts of .33 per the website, Vas 128.5l, Fs 23.2
with 3 cf I should be somewhere around .7 for system Q unless my calcs are way off ?

Even if I fracked up my Q calc, this would not explain why they sounded poor in a diploe cabinet also.

JM
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