Wayne's 12Pi sub

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Software !

I'm presuming that most, if not all, speaker design software is set by default to measure SPL @ 1M. For eg WinISD etc etc.

But 1M from where ?

I expect that it's most likely been taken as 1m from the front face of the cabinet. Or if there is no front baffle as such, eg horn, then the imagined one formed by the diagonal front edges of the cabinets circumference ?

In which case, these measurements "could" be at odds with actual 1M ones, & also ones worked back to 1M from further distances ?
 
Exactly. One meter from where? The face? The physical center of the box? Or the acoustic center?

That would be a question for the application developer.

I would expect the simple programs that calculate sealed and vented boxes from T/S specs would give a number that's relative to the acoustic center. Programs that simulate horns could probably be setup either way.

So it would be best to ask the developer, if you wanted to know for sure.
 
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:cop: Art and Wayne I think it is clear that there is no resolution here. It is time to agree to disagree. The original topic was asking whether anyone had built the 12Pi sub, not a ******* contest over who's measurements are more valid than the others.

I've not read every post in detail, but some were bordering on being personal attacks.

Please enough on the 1M vs 10M and inverse square law. I think Wayne has clearly stated his position on this, and has also said that the 1M measurements have there place, but that he prefers 10M measurements. Lets leave it at that and get back to the topic of actually building one of these subs. :cop:
 
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I've worked for a certain large nameless hifi company with a large pro division as well as a couple of smaller outfits, and with the exception of speaker systems intended for very long throw large venue/outdoor or very high Spl operation I don't recall Spl measurements ever being done at anything other than 1M.. Perhaps in the old days this was not true, but I suspect for small venue indoor applications this is now pretty standard.. I could be mistaken. YMMV

Usually 1M from the baffle..
 
That may be fine for hi-fi, but it can produce different result for horns.

DB Keele (EV, Klipsch, and JBL) published a couple of papers on the subject, they are archived on his website.

A very large manufacturer of both hi-fi and pro gear used to mount the speaker in a stairwell flush in the middle the roof, the mic was on a pole.
 
To get the sound pressure initial value, I would say the mesure at 10m and extrapolate back method should work well enough and remove any variation based on type of cabinet. You could go on and on about acoustic centers and other definitions (i'll leave that to marketing) but in the end, good enough is good enough.

SPL at 10m + 20db = SPL at 1m
 

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There's an easy formula for finding the SPL change at a distance:

newSPL = refSPL - 20 log (d1/d2)

From this, you can see that each doubling of distance makes a 6dB change, and 10x distance makes a 20dB change.

Power is calculated with this formula:

newSPL = refSPL - 10 log (p1/p2)

Increase power by 2x for 3dB increase, increase power by 10 gives 10dB increase. Increase power by 100-fold gives 20dB.
 
10 days ago I worked out a spreadsheet for calculating the Voltage & Nominal 8 Ohm Power to be equal to a 2.83V @ 1metre measurement at varying distance.
I Posted it here in post 261 http://www.diyaudio.com/forums/subwoofers/187387-waynes-12pi-sub-27.html#post2644549.
Of course being a spreadsheet it is easy to change any of the parameters to suit you own use.:)
I can see that there is virtue in using the 10 metre measuring distance. But for the majority of people, who do not have access to a vast flat area a compromise is needed. Attempting a 10metre measurement would just add too many inaccuracies due to reflections off buildings etc.
Remember 'diyAudio':rolleyes:
 
All the talk about push-pull hornsubs prompted me to reach back and resurrect this thread. I did a lot of work to optimize this horn, to allow it to take full advantage of push-pull drive and other technologies (cooling plugs, etc). So I think there is some useful information here for those contemplating basshorns using push-pull drive, especially in regards to chamber sizes, acoustic measurements, expected performance gains and so on.
 
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