The Midrange Enclosure
The midrange enclosure is not very important. Any sealed enclosure will do. However, since we are going to use our midrange to play pretty low frequencies we better give it at least a small, maybe around 5 litres, enclosure. A good thing might be to insert a wall inside the enclosure and divide the inner volume into two parts, one large containing the woofer and the port and a smaller containing the midrange and the tweeter.