We just called one another and chatted about it.
A couple of good points Kevin made to me is that the sensitivity is rated on the conservative side. So it is possible that a mini monitor might wind up in the 84db range (not too bad).
Another good recommendation was to go with a 2" flared port. Regardless of what the numbers say that it needs (because of the huge X-Max), it will likely not ever be pushed to those levels, or those extreme X-max's. So the monster port may not really be needed.
I am looking at the numbers again right now.
Looking at the projected curves, it really looks good to me in about .4 cubic feet. This is a little bigger than optimal (by the numbers) of .351 cubic feet, but not as far as Kevin had in mind (,5 cubic feet).
Still, a 2" flared port needs to be 12.25" long (ouch).
.5 cubic feet of air space and tuned to 40Hz keeps it flat to about 45Hz then it really drops hard. It is not much of a gentle rolling curve.
Would you guys be apposed to building a box with a slotted port that folds once inside the box?
Couple points.... efficiency is defined as input power electrical / output power acoustical. Usually people are looking at sensitivity, which is the sound pressure between 125Hz-4K assuming a constant voltage source and 1M measurement distance. You typically see this as 2.83V/ 1M because 2.83V is one watt into 8 ohms. The SPL/watt/meter number is simply a consequence of the T/S parameters and that number doesn't exactly match with 2.83V numbers which are typically reported by manufactures because it is comes out slightly higher than the 1W/1M number, especially if your VC is a slightly lower DCR allowing for the 2.83V number to be elevated by the fact that it doesn't account for the transducer impedance. Consumers confuse the matter and a higher number is always better.... right? It is if you are in the marketing department.
At the end of the day the efficiency is a by-product of our choice of box and bandwidth. You don't don't pick efficiency... it picks you. If you decide to target 0.5 cubic foot and a certain bandwidth, the efficiency pops out the other side of that choice. If you want to target a larger box, same bandwidth... you can pick up a smooch more. If you want less bandwidth and same size box, you can pick up more yet. So... the choice of efficiency is pre-determined once you choose a target size and choice of how deep the unit will play. How much is enough? Well... it depends. If you are using a SET amp with 45s you need a LOT. If you have a 100W solid-state amp it hardly matters. My old driver, the EX-6.5 had pretty much the same efficiency. It was within spitting distance. Most of the SS, Usher or Seas models have comparable ratings because all of us are targeting roughly the same box/bandwidth goals. One might be 1-2dB different with the tradeoff of larger box & less bandwidth but most of them are not drastically different.
Kevin Haskins
Exodus Audio
