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Old 30th January 2002, 02:00 PM   #11
ucla88 is offline ucla88  Tahiti
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super, i believe you are right.

linky to adire's sealed low q alignments.
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Old 30th January 2002, 03:02 PM   #12
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A quick check with WinISD (Ok Ok not the most comprehensive but seem mostly right on target) yields an F3 of 38Hz anechoic with a 2.332 f^3 sealed box. I believe Adire's white papers incorporate 'average' room gain to arrive at the mid 20s.

regards
peter
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Old 30th January 2002, 03:46 PM   #13
ucla88 is offline ucla88  Tahiti
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peter, i suspect the answer is a bit more complicated than that.

the -3db points according to the white paper are around 30 anechoic and in the mid twenties with room gain according to the white paper for low q alignments.

anyway, on a related note, we shall see what the nearfield f3 is for a sealed tempest is in a couple of weeks when i test mine with a clio setup (i should have it in 2-3 weeks). i'll post the results and compare them with the tempest white paper results.
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Old 30th January 2002, 04:09 PM   #14
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Right you are ucla.

But I bet ya their being a tad optimistic. Anybody have empirical numbers on a sealed Shiva?

Keep us posted on the Tempest. Are the Brahmas out yet?
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Old 31st January 2002, 08:02 AM   #15
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38Hz anechoic is the theoretical (WinISD and diysubwoofers.org spreadsheet) calculated F3 for *any* sealed box for the published (not necessarily DUMAX) T/S Shiva params.

I'd like to know how Adire get between 29 adn 30 Hz for a sealed box.... also - why do they publish Fb for their sealed box designs (does Fb for sealed boxes make sense?)

Thanks,
Dave.
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Old 31st January 2002, 03:58 PM   #16
ucla88 is offline ucla88  Tahiti
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Quote:
Originally posted by Dave Bullet
38Hz anechoic is the theoretical (WinISD and diysubwoofers.org spreadsheet) calculated F3 for *any* sealed box for the published (not necessarily DUMAX) T/S Shiva params.

I'd like to know how Adire get between 29 adn 30 Hz for a sealed box.... also - why do they publish Fb for their sealed box designs (does Fb for sealed boxes make sense?)

Thanks,
Dave.
indeed, 38 is the theoretical f3. suprisingly, i've never actually seem one of them there theoretical drivers in reality, but i'd like to get my hands on one. probably never will though.

No, seriously, there are a couple reasons why the published f3 is lower than what you get plugging the numbers into the ts equations. the first, as my feeble attempt at humor shows, is that the response of a driver rarely parallels it's theoretical response curve exactly. however, i don't think this explains the difference.

Mainly, i think the difference is explained by this quote in the white paper--


Note that the frequencies are referenced to the peak output of the system, not the nominal output. Thus,
increasing any peak in the output frequency response, e.g. increasing the Q of a sealed box, can result in a
higher actual F3, not a lower F3. We choose to use this reference (peak versus nominal) because for higher
Q systems, the nominal output is not achieved until several hundred Hertz (>200 Hz). We believe this is
not applicable to subwoofers. As such, the F3 should be referenced to the highest value below 100 Hz.


is this fair? for a sub, i think so. if you were building a 3-way system and crossing over the shiva above 100 hz then their published f3 doesn't apply.
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Old 31st January 2002, 09:30 PM   #17
Ron is offline Ron
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Smile Thanks to All

Thanks to all that have taken the tome to respond to my questions.
I must admit I now have even more. Will be back in a couple days to see if I can get some clarified.
__________________
Ron
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Old 31st January 2002, 09:44 PM   #18
Ron is offline Ron
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Default F3..??

Mainly, i think the difference is explained by this quote in the white paper--


Note that the frequencies are referenced to the peak output of the system, not the nominal output. Thus,
increasing any peak in the output frequency response, e.g. increasing the Q of a sealed box, can result in a
higher actual F3, not a lower F3. We choose to use this reference (peak versus nominal) because for higher
Q systems, the nominal output is not achieved until several hundred Hertz (>200 Hz). We believe this is
not applicable to subwoofers. As such, the F3 should be referenced to the highest value below 100 Hz.


is this fair? for a sub, i think so. if you were building a 3-way system and crossing over the shiva above 100 hz then their published f3 doesn't apply.

----------------------------------------------------------------------------------

*****The above was a quote from UCLA88*******.

I screwed something up in trying to reference the above.

In referring to the Adire Sealed Application PDF they reference something as using a Dumax T/S parameter of a sealed box Q of 0.5 as having an in room F3 of 24.4 Hz. Would I be able to actually hear this?

They also site an in room F8 of 15.0 Hz...... ????

Trying my best to decifer some of this but it is one big fog right now.

Regards,
__________________
Ron
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Old 1st February 2002, 01:47 AM   #19
ucla88 is offline ucla88  Tahiti
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for a bit on dumax testing, look here .

people like to talk about in room f3's being 5-12 hz lower.

while this is true, and in some sense more accurate, you have to understand the ground rules. first, room gain varies, depending on the room. unless you've tested your room, you don't really know how much gain you'll get.

also, at any given frequency, all drivers will get the same room gain. Look, the f3 of an NHT 1259 driver in a sealed box is about 25 or so, if my memory serves me. with room gain, maybe you get extension into the high teens. so, a sealed 1259 goes lower than a sealed shiva. NHT could claim an in room f3 of 17hz (i'm guessing here).

however, most people would pick the shiva as the sub with "more bass."


The problem with many LF drivers on the market is not their ability to go low, but the spl generated. If you look here , you'll see that the spl that the shiva can generate at 20 hz beats the other drivers listed. Yes, you need to go low, but you also need decent spls-that's part of the reason these long throw drivers have become so popular.

you definitely will be able to hear and feel the mid twenties bass-more so because the spl produced will be in excess of 100 db.
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Old 2nd February 2002, 09:34 AM   #20
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The problm with stating an "in room" F3 is that you will not get a consistent results between different rooms and it seems to me like the marketing department has more to do with this than anything else (F3 of low 20s sounds so much better than 38 Hz but in most music you'll find very little below 40 Hz, except when listening to organ music where you can even find significant output below 16 Hz (64 ft pipe, though rare gives you 8 Hz) and telarcs recording of the 1812 overture has significant energy at 5 Hz). Film effects rarely venture below 30 Hz, but it does happen. BTW F3 referenced to 100 Hz isn't fair either, because you'll want to reference the F3 of the system to its rated efficiency.

Someone mentioned that speakers do not follow T/S response predictions exactly. Due to the approximate piston like behaviour at low frequencies the T/S model gives a very accurate estimation of the response (usually well within 1 dB if one uses accurate T/S measurements) but at higher frequencies the assumption of a piston no longer holds true.

On a different note, do any of you have experience with the Blueprint drivers because I am looking at getting one (the 1201) for myself though the 1503 with a Linkwitz transform sounds positively yummy ;-)
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