This side project is geared more toward the people who use their cabinet as an arcade jukebox from time to time. Most MAME games with an exception of a few will not benefit through this procedure.
I've been working in car audio and home theater setups for many years and I wanted to obtain some better midbass from my speakers. You see in the real world speakers can be run free air (like in a cabinet) but that leaves them short of what was really intended. You see in a free air setup you can drive the speaker past its mechanical limits easier then one that is in a box. With small 5 1/4 speakers your best bet is to go sealed. Ported is pretty unrealistic and difficult to do with the small space issue and would be more trouble then it's worth. I came up with a really simple solution that requires zero woodworking skills and provides an amazing air tight seal:
SET YOURSELF UP WITH THE GOODS!!
First go to any supermarket or retail outlet that sells Tupperware. Locate a decent size bowl that looks around 5 inches wide and contains around .20-.100 cubic feet (2-6 inches high) of air space. I have mine in 5 x 3 which nets .55 internal volume after driver displacement. Make sure this bowl will be able to fit around the magnet behind the speaker installation zone. I find a bigger lip around the open edge of the bowl gives better surface contact for easier mounting. The color is non essential but I must stress that a black bowl will direct light through a visible area much better then a clear one. So if you are using LED's to light your speakers use a dark colored bowl so all light output goes through the front and isn't lost through the back or shown in the marquee.
START THE PROCESS
Next thing you want to make sure of is that both speakers have an air tight front seal in its recommend volume. Place silicone sealant between the front surround edges that meet the wood. Don't worry it just peals off if you ever want to remove it. This may be pretty tricky to do if you have a speaker grill that shares the same screw holes. Just have someone hold it from behind or tie it off to a stationary object and seal it from the front. If you somehow went through the back of the speaker wood with long screws make sure to dab a few drops on top of the screw holes. You do not want air to escape the "chamber" this reduces efficiency
Drill out a couple small holes in the bowls you purchased and shimmy the wires that are needed inside to power or light your speakers. I installed 4 super bright LED's in each and glued them to the inside of the bowl in a N, E, S, W type fashion. Try to come up with a simple wiring solution in case you need to get back into the back of the speakers or plan to move. A simple barrier strip works nice when installing LED's.(SEE PIC)
Next, place the bowl behind the speakers magnet and center as well as possible. Apply silicone sealant around the outer edges of both bowls. This can be tricky doing it from the back, so make sure the marquee is opened to get those hard to reach places.
Lastly, you need to cover those drill holes that you made in the bowls for the speaker wires. Seal it with silicone no one will ever see it.
SELF TESTS
Hear are a couple seal checks you can try out.
Come to the front speakers when everything dries and push on the speaker cone gently from the front. It should comes out very s l o w l y after you let go. If you hear wisping, comes out fast, or you hear air noise then you have an incorrect seal.
Take this one step further and smoke it. Calm down it's just my terminology. Take a cigarette, incense or anything that smokes then put it close to the speaker while pushing it in. Does smoke enter the speaker when you push it in? It shouldn't. Also do this test behind when a friend pushes on the cone.
With this setup in hand you are looking at tighter midbass and amazing sounding speakers guaranteed.
On a side note please be careful in your net sealed air volume because different drivers have different perimeters and you can actually build a box that sounds even worse then running them free-air.
