Emilio's experimentation with the 24db high pass on the plate amp has merit and is a good one. I'd like to say that I have "been there done that", but have not. I do understand the theory though. There are a couple of angles that makes sense.
First, as mentioned elsewhere, a sealed cabinet will generally roll off around 12db/octave. A ported enclosure will generally roll off at 24db/octave.
Second, there are phase issues. Anywhere there is a resonance hump there is an electrical and acoustic phase shift in the drivers. A sealed 1801 at about 17 liters of cabinet will have a driver resonance of about 45hz. A ported 1801 will have 2 resonance humps. One is at about 20hz. The other is at about 60hz.
Third, most subwoofer plate amps have a low pass at 12db/octave.
The two competing arguments are thus.
1. A sealed monitor is better. Its 12db/octave roll off will match with the 12db/octave low pass installed in 95% of plate amps. There is also little phase issues because where the monitor resonance takes place is also where the monitor rolls off. The bass from the subwoofer will be slighty more prominent.
2. A ported monitor is better. It's 24db roll off allows the effective use of a 24db low pass from a plate amp. The 24db low pass from the plate amp restricts the spl from the sub at higher frequencies. This decreases the ears ability to localize the subwoofer. The monitor will surely have a resonance frequency at 60hz, but this is insignificant. These frequencies are soooooo long that they will be swamped by room modes. This is the approach that Dave Craig takes. He has puttered extensively with this, and prefers the 24db low pass plate amp and a ported monitor.
I must also add that Dave Craig sells what appears to be an excellent plate amp. It is the only one I have seen with a terroidal power supply. If you want an excellent plate amp and don't want to mess with the electrical puttering of installing your own 24db low pass, then Dave's amps will work. Dave's website is here. You will probably have to email him about his plate amps. His 150wpc plate amp will put out an honest 150wpc and the cost was $300 the last time I checked. His site is here:
http://www.artofsound.net/LINE%20UP.htm.
Stuffing in a sealed cabinet:
I generally recommend stuffing the entire sealed cabinet. The air travel in a stuffed cabinet will be slower and the driver will see a larger cabinet. It is possible to overstuff the region around the back of the drivers and cause resistance to air flow. This obviously makes the driver see a smaller cabinet. If the driver has a little room to breathe, it will be fine. Emilio is right on the mark with his stuffing.
Dave
