posted
Question for the masses: If you take an isobaric multiple driver enclosure (i.e. 2 MTX RFLs which require 5 cft of airspace each) and make the air space not half which is 2.5 but make it 5 cft and run 4 MTX 1000Ds (2 to each) does that overcome that less effieciecy of 3db in that type of enclosure? So that it in turn performs as 2 RFL's in 5cft each? From what I gather the point of the enclosure is to reduce the amount of volume of airspace in the enclosure. Thus two acts as one in the space of half of one.
So my question is, can two act as two in the space one? Also will a port interfere with this type of design?
I want to do the recommended port size as well which is meant for your typical ported enclosure as per MTX. That way its performing at the right tuned level for my SPL.
Thanks for entertaining my question all. Sorry if it seems elementry but ive been out of the loop since we left for Operation Enduring Freedom.
-------------------- circuit city installer
Posts: 4 | From: san diego ca | Registered: Nov 2001
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posted
Thge problem with isobaric is that no matter what you do with the box you still only have the cone area and displacement of a single sub. You may be able to get the same output from a 5 cuft box with two as you do with one. But I would think if you maximize both boxes you wouldn't se a difference between the iso and regular.
Posts: 2575 | From: GA | Registered: May 1999
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posted
Ok. makes sense. To expand on this...if it has twice the excusion of one cone, then wouldnt the displacement be the same as two cone areas if the excusion is twice as many as one?
btw this site rocks. i actually get more replies than carsound.
-------------------- circuit city installer
Posts: 4 | From: san diego ca | Registered: Nov 2001
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posted
It doesn't have twice the excursion of one sub. There are mechanical limitations to how fow the cone will move, and putting two subs isobaric does not change that.
Posts: 2575 | From: GA | Registered: May 1999
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posted
In the simplest terms ISO mounting a pair of subs will double the moving mass that has to move. This will theoretically 1/2 the VAS of the speakers. But the down side is that in doubling your cone mass, you also decrease your efficiency by 3 db because of the increased mass the amp has to move. Basically,
If you have a single sub in a 2 foot box with 200 watts, And you want a smaller box, You can get the same output with 2 of those subs in a 1 foot box with 400 watts.
Only 1 woofer is radiating sound to the outside as far as cone area goes (excursion is pretty much irrelevent here, it will not change any significant amount). You double cone mass so you lose 3 db, but you double power and thus you have the same output in a box 1/2 the size. The bad part is that that can get expensive and many subs take boxes so small now ISO mounting is obsolete.
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