Large sub based on 18LW2400

[OpterN]

I'm planning my first subwoofer project and would like to hear some feedback before starting the build. The sub would be used inside living room.

Idea is to use 18sound 18LW2400 4ohm driver and build a reflex cabinet for it.
Driver datasheet: http://www.eighteensound.com/Portals/0/PDFs/18LW2400.PDF

Dimensions for the cabinet would be around 40 cm x 90 cm x 110 cm giving about 400 liters for volume. There would be two reflex tubes with diameter of 19 cm and 60 cm long. Tuning would be around 24 Hz. Attached is a fast sketch. Cabinet would be build using 19 mm or 22 mm thick MDF. Some bracing is needed, but what do you think about the cabinet design and the driver?

As an amplifier I'm planning to use one of those cheap high power IRS2092 modules, at least for starters. Noob question is how should two channels (L/R) be connected to amp's one input? Source is going to be miniDSP and maybe at some point PLLXO.

All comments are very welcome and needed.

Thank you.

 

[sreten]

Hi,

Generally speaking a cabinet significantly larger than Vas of the driver
indicates a non-optimum choice of the driver for the wanted extension.
Generally speaking Vbox < Vas indicates a good choice.

A passive resistive mixer should be fine for stereo to mono conversion.

rgds, sreten.

Domestically I can't imagine anyone needing more than a pair
of LAB12 drivers in separate 100L boxes tuned to around 20Hz.
(One amp in 1 box, about 1KW into 4 ohm, 4" flared ports.)
Are you sure you need that size box and SPL capability ?

 

[OpterN]

Thanks for quick reply sreten.

I know max SPL would be over kill, but I wanted something that will never lack a punch. Originally planned building two of these, but now I'm hoping one is enough.
Driver was chosen because of price and availability in Finland (and some good reviews).

Increasing the box size seemed to extend low end frequency response, when simulated using WinISD software. Would Vbox and Vas imbalance cause serious problems?

 

[sreten]

Hi,

Its not a serious problem, its just indicative of non optimum design.
TBH I like the look of 250L tuned to 20Hz. Room gain friendly.
(Some quick modelling in WinISD.)

rgds, sreten.

 

[OpterN]

Project has been moving rather slowly, but now it is only waiting for some paint. I scaled the box a bit smaller and the inside volume ended at about 370 liters. So far I have liked the sound of it a lot.

Suggestions what I could/should have made differently are very welcome.