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Old 15th March 2009, 08:15 PM   #21
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Quote:
Originally posted by fwater



Jeff Bagby's Box Modeller 3.20 shows differently. In some (maybe many) cases, the f3 will appear similar in numbers, but the Qts is different for either wiring, even if you're using the same volume. The curve also appears different, the rolloff often having a hump or sometimes a more "rounded" bottom. The volume requirement for similar output isn't exactly 50%, more like 60-70. I can't recall exactly why this is, maybe someone a little more well-read will jump in.
You might want to get that clarified before assuming it is correct. If you mis-size the box you will get incorrect results that may need a rebuild to correct.

I don't have time to re-do all the math now, but I found this with a quick google search from a company that makes T/S testing kit.
See under "Multiple Driver Tests"

I see no reason for there to be a difference.
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Old 15th March 2009, 08:35 PM   #22
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Quote:
Originally posted by nukaidee i don't mind porting the sub, but i think i calculated something stupid like 0.5 inches in diameter and 2 inches length.. where am i going to find pipe like that....
A drinking straw?
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Old 16th March 2009, 01:48 AM   #23
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is a drinking straw strong enough to allow for resonance?
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Old 16th March 2009, 02:28 AM   #24
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Quote:
Originally posted by Brett

That sounds like isobaric.
I guess that depends on one's definition of isobaric, when it first appeared on the market the Mani-2 was not typically referred to as an isobaric design by reviewers because Totem had the midbass drivers mounted magnet-to-magnet in bipolar fashion instead of the more common cone-to-magnet isobaric configuration but it's not a bipolar because there is no rear baffle, the second midbass driver is sealed inside the cabinet.

So here we have both drivers bass-loading the same chamber. However this speaker is now commonly called isobaric, perhaps because there seems to be no clear definition of what constitutes an isobaric configuration.
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Old 16th March 2009, 02:35 AM   #25
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hm. i've been looking at the micromain posted up there again.. the enclosure definitely doesn't seem big enough for the 2 huge woofers.. however they said they just mounted the motors together, i thought that would cancel all the bass? that design is a whopping 3grand.. man. i think big =P
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Old 16th March 2009, 02:43 AM   #26
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Quote:
Originally posted by nukaidee
is a drinking straw strong enough to allow for resonance?
Lol I wasn't being serious, I cannot conceive of a 0.5 inch diameter port that would emit any usable bass unless you have several of them. Even though it is very possible that a vent calculation formula could yield such dimensions, these results are not always practical in reality. Such a tiny tube would have huge resistance and bottleneck air movement to such a point that the system would behave like a sealed speaker.

ProAc did use drinking straws in at least one of their models, the Response 2, but there were hundreds of them stuffed into a much larger port.
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Old 16th March 2009, 05:17 AM   #27
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Quote:
Originally posted by Willitwork
However this speaker is now commonly called isobaric, perhaps because there seems to be no clear definition of what constitutes an isobaric configuration.
Sure there is. iso-barik = constant pressure. A 2 driver arrangement where the front driver sees constant pressure (above the roll-off of the back driver), Tiefenbrun got a patent, so it is pretty well defined.

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Old 16th March 2009, 05:24 AM   #28
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Quote:
Originally posted by Willitwork


Lol I wasn't being serious,........
Just make the port larger in diameter until you have a length that makes sense
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Old 16th March 2009, 05:38 AM   #29
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no point making the port half the size i want my box to be right? and the bigger the port.. the longer the tube and .. yeah. doesn't work.

continuing on with isobarick.. i know about the constant pressure, so if i am mounting them in phase, motor to cone ... does the front or the back one need the 1/2 volume while the other one needs the smallest air possible?
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Old 16th March 2009, 05:50 AM   #30
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How small is your box really
Sounds like its VERY small
Not sure what strange things may happen when the volume between the drivers begins to be equal size of the box volume...not sure I would rely on calculations if thats the case and on that to work properly
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