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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Riley Casey on August 13, 2013, 01:53:00 pm

Title: Sub volume ?- working backwards from truck pack
Post by: Riley Casey on August 13, 2013, 01:53:00 pm
I have several JBL 2226 drivers that I am very happy with the sound of but they are loaded into absurdly large quad 15 cabinets.  The drivers themselves are actually loaded as single enclosures with dividers in the cabinet.  Ahh from the days when the Saudis worked for us rather than we for them.   I'm looking at building several new subs to truck pack dimensions ( 22.5 x 30 is our standard footprint ) and am casting about for best ways to design boxes starting with a fixed pair of dimensions and a known driver and come up with suitable volumes and vent sizes.  Any suggestions?
Title: Re: Sub volume ?- working backwards from truck pack
Post by: Paul G. OBrien on August 13, 2013, 03:33:05 pm
How will these JBLs be used. as subs.. bass or even mid-bass cabinets? The driver works well with a range of cabinet sizes and tunings so you don't need to go as big as possible if these will be deployed as mid-bass cabs for example.
But assuming it's general use a 5 cuft box tuned to 45hz is a good place to start, you can make that box any shape you want including a cube with the only other requirements that the box be deep enough so that there is no obstruction to the ports or rear vent of the driver and that there is enough surface area on the baffle for the driver and ports.
Title: Re: Sub volume ?- working backwards from truck pack
Post by: Art Welter on August 14, 2013, 11:54:08 am
I have several JBL 2226 drivers that I am very happy with the sound of but they are loaded into absurdly large quad 15 cabinets.    I'm looking at building several new subs to truck pack dimensions ( 22.5 x 30 is our standard footprint ) and am casting about for best ways to design boxes starting with a fixed pair of dimensions and a known driver and come up with suitable volumes and vent sizes.  Any suggestions?
Riley,

The 2226 is a great sounding  driver (and sought after for home stereo use), but has only 7.62 Xmax- considerably less expensive drivers are available with double the Xmax now.
With an FS of 40, it won't perform optimally tuned much below that.
Designing for sub use there is simply no replacement for displacement, doubling displacement allows for 6 dB more output.
Design always ends up conforming with Hoffman's Iron law- Loud, Low or Small, pick two.
The Iron Law puts fixes certain relationships- to keep port vent air velocity low (like around 15 meters per second) to utilize greater Xmax speakers requires large ports, large ports tuned low become very large compared to cabinet volume, small cabinet volume "wants" higher tunings..
When you design using a program like Hornresp (free) that shows port velocity and Xmax, you can realize the best compromises for the chosen speaker parameters, cabinet volume and Fb.

With "25 Hz the new 50 Hz", I find a tuning (Fb) of around 36 Hz to be the best compromise between size and extension for most pop music- the low note on a 5 string bass is 31 Hz, last century four string basses with 40 Hz as the low note were common.

Art
Title: Re: Sub volume ?- working backwards from truck pack
Post by: Tim Weaver on August 14, 2013, 06:33:34 pm
As far as JBL is concerned, it's 4 cuft per driver tuned to 40 hz.


The cabinet can be any shape you want as long as there is 4 cuft inside.


http://www.jblpro.com/pub/manuals/enclgde.pdf

Title: Re: Sub volume ?- working backwards from truck pack
Post by: Art Welter on August 15, 2013, 03:03:12 pm
As far as JBL is concerned, it's 4 cuft per driver tuned to 40 hz.
That would be one "general purpose"  bass reflex alignment suggestion from the infinite choice of alignments available.
Title: Re: Sub volume ?- working backwards from truck pack
Post by: Richard Turner on September 16, 2013, 10:37:16 pm
As far as JBL is concerned, it's 4 cuft per driver tuned to 40 hz.


The cabinet can be any shape you want as long as there is 4 cuft inside.


http://www.jblpro.com/pub/manuals/enclgde.pdf

I've made the single 15 and dual 15 from that list before, both work well with the losted JBL drivers, 2225, e140 e145 etc. no need to re invent the wheel, good for general purpose MI band use, pre recorded playback etc.