Anyone measure the Atlas 12 yet

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Here is Simon5's thread re: TS parameters.

He also back-calculated TS based on Qts.

This is fine, but I would like to see real, accurate TS measurements. I think the original ones were wrong due to back-calculating as opposed to measuring, and I suspect the Le discrepency is the result of applying a formula as opposed to measuring. Either that, or the build shop did not build to spec.

I don't really care about the effect of Le on impedance because I have a lot of EQ at my fingertips. What does concern me more is that higher Le may indicate inadequate shorting rings, which could mean higher distortion.

I think everyone should keep things in perspective though. The Atlas may not be a $400 driver, but it certainly looks like it could be a great $100 driver, and that's what it costs at the moment. I won't have time for a while to do any real testing, but my initial tests seem to indicate that it perhaps gets a little more excursion than Shiva before making that wonderful "thwap thwap" sound, and at 15" it is moving a LOT more air.
If Simon5 want to fantasize about the T/S parameters, that's fine by me.

Our goal was distortion testing, so we didn't run a full set of T/S parameters. We ran the Le for since the distortion numbers indicated an Le that was quite a bit higher than the published specs.

For most people this isn't a problem. It could/would be a issue if one wanted to run the driver above a standard 80Hz XO point.
simon5 said:

I don't want to fantasize, I'm trying to help.

johnmark, if you didn't return the drivers already, I think you should try one driver per 3 cu.ft box with lowQ. I would like to hear your opinion on this.
that's what the forums are for to help each other as, no one person can have all the answers! i appreaciate all the help i've got. keep up the good work! crippledchicken

Sent them back.
Decided to stick with the single NHT 1259 per side and use a lower cut-off freq. The suspension of the Atlas 12 seemed very stiff to me but probably needed some extended run-in time. I am not able to leave my subwoofer running all day for several days however.

ThomasW said:
We measured 2 different samples of the Atlas 12" driver. Stated Le is .86 mH.

The 'nominal' Le measured with VC #2 open, 2.45mH

Hey Thomas,

Do you recall at what frequency you had measured this?

What many might not be considering is that in the vast majority of loudspeakers, inductance falls with increasing frequency. Some programs allow to better model the nature of this shorted inductance. Note that almost all manufacturers list the Le as a calculated Le at 1kHz, not a curve fit. With the common specification given this way, the ONLY way I would expect to see more accurate numbers would be with an additional spec at some lower frequency. Due to the interactions with lower frequency impedance resonances, the best method is by curve fitting rather than discrete measurements.
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