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Discussion Starter #1
So after reading the site for so many hours, and seeing great subs on here, the internet, stores it got me to thinking. Most subs are designed for convenience. Convenience of size, price and overall capabilities. I was browsing the GR Research forum on here, and the guy was talking about his 12" sub is a great overall one, and that overall everything has trade offs, which is a great point. And that topic got me to thinking. What If I build a multi sub system where it shares 1 box but has seperate chambers within the sub for each driver. I was thinking a 3 way sub system.

It would be a large box at least 95" wide, 20" Tall, and 20" Deep. At least, that would be the bare minimum I calculate needed to mount it all.

It would have a Chamber that is shared by two 18" Drivers on the edge, two 15" Drivers on inside, and one 12" driver in the center. Here is the general gist of it;

Frontal View of the speakers, or down firing, haven't made a decision.
_____________________
| |
| 18 15 12 15 18 |
|____________________ |

Top View Cutaway

_____________________
| ____________ |
| | ____ | |
| 18 | 15 | 12 |15 | 18 |
|_____|___|____|__|___|

With the ports kind of in different directions for each chamber, so there isn't overlap of sections. And each size group would have a Crossover that mildly overlaps. I was considering something like, 12" plays 80hz to 55hz, the 15's play 60hz to 30hz and the 18's play from 35hz down.

Now this is all kinda theory, and wanted some feedback on this.
 

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Discussion Starter #2
Sigh, the lines came out fine when I made the post, and when I tried to edit, but in the forum its a little wonky, hope you all can understand it....a bit at least.
 

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First off what is your budget for the speakers?

If I had to use these speakers and could only have this layout I would Hpass the woofers at their tuned port, but let them all run up to the same crossover point of 80hz or whatever. The 12 and 15 could run higher do to the location and higher tune. You could run the 15's higher if you place a main channel speaker above it also.

But that being said budget is the main question here. I myself would rather have four 18's in the corners. The 15's and twelve wont really be heard much over the 18's. And with such a narrow area of use, 35hz and down, it seems like they would be a waste. Use the 18's up to 60hz at least.

Have you tried to simulate this. The twelve seems like a waste also.

How big is your room?

With 1.5" walls your net volume is about 15cuft before drivers, bracing and ports. Sounds nice for most 18's.
 

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Discussion Starter #4
Yeah, kinda, but i was kind of referencing the GR Researches posts.

am not that interested in producing a larger version.

There is only one plus. It sweeps more air and can produce a higher SPL level in the really low frequency range around 20Hz or so.

The negative is that it has a much higher moving mass. This means more stored energy and much longer delay times involved in stopping the driver once the signal stops. And that's really the name of the game. At least for me and my customers. It is all about quality not quantity.

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That is why I was talking about a 3-way sub. Allow for low mass tight bass able, yet the depth of the 18's and have the port tuning and volume for the 18's.

Just a concept idea, not even close for refined. Demensions are based on my current sub is 12" and has a 15" box enclosure. So I just modeled it as each driver had at least 3" additional, so 18" x 2, 15 x 2, 12" x 1, plus 5 drivers with at least 3" added for each equals 93, than for additional bracing and port tubes maybe a couple inches added. Which is why I mentioned a minimum of 95" Wide, 20" Deep, 20" Length needed for minimum bracing, ports, and volume for the clearance of the driver, and magnet of them.

And budget, this is all concept so I can build it later. and pretty much at no barred costs. Dont want an IB, and dont want a sealed sub. A SVS is probably great for the money but thinking that i can do better for the same money. not in it for the profit
 

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Yes, it could be done. Honestly I don't seen the point in my mind beyond creating excessive SPL. Big drivers in big boxes can go low and loud, so HPFing a 12 or 15 in that big of a box isn't very efficient in terms of space, it would also make thermal power limits of the drivers your concern. Then the 18s would be handling the "real" bass duty. The varied driver sizes doesn't do anything for you functionality-wise.

If you want the coolness factor, then do it. If it were me and I could have a box that massive I'd consider multiple 18s and run them all the way up to 80-100Hz. You could get choosey on the looks and maybe pick a top-of-the line 15" drivers instead. You could also complete the multiple driver and different size look by using passive radiators (PRs).
 
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