Cabinet design

Cabinet design	Note: By clicking the images you will get a bigger image.
	Interested in having a look inside... In my speakers I have only used wood from birch. Birch is very hard, dense and heavy (0.69 kg/l which is the same as for oak). I had first planned to use oak, but I couldn´t find any sawmill which could deliver oak. I then decided to use birch instead who have almost the same characteristics as oak, but is much harder to work with. By comparing birch with MDF-boards (MDF = medium density fiber boards, 0.75 kg/l) which many use in speaker cabinets, you will find that birch have less «sound» then MDF-boards. If you knock on a MDF-board (don´t break any bones), you can hear a loud bright sound which can lead to a closed or a «box» similar sound if you are unlucky. In building speaker cabinets, there are two main schools (correct me if I am wrong). Either you can build a speaker cabinet as rigid as you can (risking to get a high resonance frequency in your cabinet), or you can build a speaker cabinet not so rigid and fill it up with some kind of resonance killing material (to prevent low resonance frequency in the cabinet). I chose to build them as rigid as possible, mainly because the cabinet is of bass reflex enclosure type.
	If you look closer at the different boards which the cabinet is made of (left picture), you see that all boards are made of smaller boards put together. A construction like this will prevent the wood in the cabinet from become misshapen (as told before birch is not easy to work with). When putting together a board of smaller boards, the board will become harder in places where a board is connected to another board (because of the glue). This I hope will prevent up to a certain degree vibrations in the cabinet (vibrations or waves have problems in passing through a medium with different densities). Left and right side of the front are round to avoid diffractions.
	The draft shows how the cabinet looks inside (cross section). The sidewalls have a large area (47x30 cm) so I have made them more rigid by building a stiffener between the sidewalls (dot-and-dash lines on the draft). Where the top-, bottom- and sidewalls are connected to the front and rear of the cabinet, the boards are much thicker. This because it is at these places forces on the cabinet is largest. A construction like this will also prevent standing waves in the cabinet (fewer and smaller parallel areas inside the cabinet).
	This draft shows more specific the measurements of each board (cross section) of the cabinet. The minimum thickness of top-, bottom-, rear- and sideboards is 24 mm (which I hope is enough for a cabinet enclosure of 17 liters). The maximum thickness in the corners is 42 mm. The front is 30 mm thick.
	More specific the front board (baffle) looks like this. Dot-and-dash lines show where the side, top and bottom is connected to the front. The inner circles indicate the hole for drivers, and the outer circles indicate the maximum diameter of the drivers. The front board is completely split into two parts. This to prevent vibrations from the woofer to influence in a bad way on the tweeter and visa versa. In the split I have put some rubber-like stuff (looks like the rubber in your mouse-pad I guess) to get the front baffle «air-tight».
	The rear plate. The circle and rectangle indicate the hole for the bass reflex port and the hole for speaker terminals. The bass reflex port is 10 cm deep, and is tuned to a frequency around 45 Hz. `TABLE: Some cabinet data` Weight (only cabinet) 8 kg Weight (total) 11 kg Volume 17.4 l Density (birch) 0.69 kg/l

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