Side Firing Subwoofers to go under the Finalists

[tommarra]

I am planning to build myself a pair of side firing subwoofers to go under Finalist speakers...you know for more bass output when used for HT application.

Can some one provide me with feedback on the plans.

Here is what I plan to use:

I have to use a side firing design, because I plan to have the width and depth exactly the same as Finalists (i.e. 11 inch wide and 15.5 inch deep)
Also I cannot go higher than 19 inch outside height becase otherwise the Finalists tweeter will be above my ear height in listening position.



Drivers: 2x SB Acoustics SB29SWNRX-S75 10" Subwoofer (These drivers are set in stone, as I have an existing 10 inch subwoofer using this driver. I will reuse the driver from the other woofer)



Cabinets: ~33.5 liter sealed (see drawing below)

http://sdrv.ms/17s4dlU

Amplifier: Parts Express Yung SD300-6 with 6dB boost at 30Hz. I choose this because when modeled the boost at 30 Hz gives a good deep bass extension.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=301-510

I tried to model the subwoofer using Jeff Bagby's Woofer Box Model spreadsheet for:

Link to the Excel spreadsheet: http://sdrv.ms/17s7EZO

Relative -3 dB Point 26.77 Hz
Relative -6 dB Point 23.45 Hz
Relative -10 dB Point 19.36 Hz

Also see the diagram attached.

6dB boost @ 30Hz:



No Boost:



Super imposed: Boost and No boost:



Now designing subs is new to me. So can someone please have a look at what I have done and give me feedback on the design.

Thanks in advance for your help!

[SATX]

Hi, I know this is old and not sure if it's still on your radar or if you've finished it, but I'll give it a go.

I've been considering these woofers in sealed cabs under a pair of speakers too. You need to take a look at the excursion for your design. The transfer function is nice to look at in a graph, but if you can't get any volume before you're reaching xmax then it's not worth much. Also, in room your FR chart would extend quite a bit lower (into the 20's probably even for the non boosted model).

In a box that large, you will have a Q of only about .5 which is OK if you are looking for a nice extended dry bass. Unibox is calling for a box of only 12L for a Q>.707! The problem is that, without the air spring you would get with a smaller box, you will reach xmax with less than 75W without boost. I'm not sure what the Yung's HP filter is at, probably around 19HZ, so this should help you out there. Your design will still probably be xmax limited, especially with boost.

If you were to use a smaller enclosure your power handling will improve. In a 20L box the driver will just breach xmax with 125W @ 23Hz.

Now, depending on your spl requirments and how loud you mains can play, you may be fine with the 33L box. Without bass boost and a HP filter, you would be able to reach about 102DB. Just be aware that you could damage your driver with that amp and it's boost.

With all that being said, I recently built a sub that reaches xmax with 200W when eq is applied and I'm running it with a 620W/channel pro amp. I took my normal listening levels into consideration and I've haven't run into a problem.

Hope this helps... or it turned out really nice if you've already built it.