Tall and narrow 9' cab for 2269

[Mr. Widget]

Did I calculate wrong? Height would be 60", 57" internal. 22X12x57 internal yields 8.7'. So with a bit of eq i should be able to get them down to 22hz with room gain? I have a Driverack 4820 to mate with the 2269s and the U15s.

No, well, maybe, but I didn't bother multiplying your dimensions. I must have mistaken your 8 cu ft for an 8' tall column.

Regardless, the answer is essentially the same. You can make them any dimensions that work for you as long as the volume is correct. There are basic rules about standing waves etc., so avoid cubes and simple relationships of even multiples. You don't want a 1' by 2' by 4' interior dimension if you can help it.


Widget

[Ian Mackenzie]

Remember to account for the volume occupied by the port inside the enclosure.

You may have accounted for the following. But l will put the following out there for the uninitiated.

I have not simulated this particular driver.

If you look at the original JBL drawings for the 2245H Subwoofer Project that would be a good starting point to realise a practical box. You could put the woofer on one end of the enclosure or one of the sides. Mounting the port on one end will possibly give you enough port length with three 4 inch ports.

Those ports will use up in the order of 18L of enclosure volume. The woofer volume is about 8L and the bracing can be assumed to 24L. So your gross enclosure volume of say 250L ends up being 50L less of used volume. That leaves 200L of volume remaining behind the woofer.

Then allowing for the fibre glass wadding on the enclosure walls this will add around 5- 10% volume or 20L to the internal volume of THD enclosure. The net enclosure volume might look like 220L. But that’s 30L less than your target volume.

Box losses can also unfortunately impact on your net enclosure volume.

A unity box loss call QL=7 on your simulator assumes a fairly rigid box with no leaks. The rule of thumb is the bigger the enclosure the more it will typically flex, shake or leak and dissipate energy as a loss. However to much bracing will make the box impracticable to lift and move.

So your best option is to oversized the enclosure by 10-15 % and tune the ports according to your modelling for the desired low end F3.

This is just a FYI to take on board after looking at your simulations. It used to do my head in working this out. Simply over volume your box a bit after running your simulation to be on the safe side!