I just ordered the same kit, but grabbed the XLS 2502. I'll be running the coils coupled. I wonder if the 2 Ohm impedence taxes the driver. In another thread I was told that when coupled the overall impedence is closer to 6 Ohms.
My hope is to run duals off of one 2502, with a total of four subs and two amps. Now I'm wondering if it might be a decent idea to exchange out the Crown for Behringers. What I like about the Crowns, however, is the higher SNR and the quieter operation.
Another thing to mention is that I'm not concerned as much about output as I am about coverage throughout the room. I have an SVS PC-2000 and HSU VTF-3 MK4. Shady mentioned some differences between the Ultimax and my current subs. It was interesting to me that outside of 20hz-35hz that the Ultimax outperforms- even on the lower side.
@TLS Guy I'd love some of your insight. The musicality of the UM18-22 appeals, hence the shift, and I know it's more suited to that than what I'm working with right now. Gear, btw, will be 4400H running to 2x4hd to the Crown (haven't put the kit together yet, so just my Denon handling everything right now).
To much attention is paid to solely how low will it go. The other side of the coin is how loud will it go at that frequency. At 25 Hz those drivers become limited in power output to 100 db 1 meter. If you have 2 of them then 103 db and 3 db for each one you have. Domestically for most that is pretty good. If you are a real "bass head" though probably not enough. Also people tend to set their subs far too loud in my opinion. That sort of sonic imbalance seems far too prevalent.
The other issue is that those drivers below 25 do not increase their power output with increased drive due to mechanical limitations.
If it were not for size factor no one would ever stuff a woofer in a sealed box. Basically it is a terrible idea and extremely crude.
At low frequencies a loudspeaker cone is horribly inefficient. I know generating sound is all about moving air, but a speaker cone does not move a lot of air. It takes pressure to move air.
That is where the concept of using an acoustic transformer comes in. The analogy is identical to an electric circuit. Voltage cause current to flow, the higher the voltage the high the current and the greater the power. Pressure is equivalent to voltage. Air movement equivalent to current. So we need pressure variation to move air.
That is what ported enclosures, pipes and horns do. The provide high pressure to the back of the cone. Much higher in fact than the restoring force of a sealed box. On top of that the rear radiation from the cone is totally adsorbed in the box and therefore wasted..
So good enclosures harness the power from the rear of the cone where there is very high pressure. This pressure then generates highly significant air displacement from the port, pipe or horn mouth. Of these the horn is by far the most efficient and the pipe close behind. A pipe closed at one end is the easiest to understand.
In a pipe where there is maximal pressure there in no air movement. Where there is no pressure there is maximal air movement. So at the closed end there can not be air movement only pressure change. The pressure is high, and therefore ideal for limiting cone movement and controlling it. At the open end these high pressures generated at the closed end result in large air movements from the open end.
In the ported enclosure the pressures are high and we have to make sure that the port has sufficient cross sectional area to not generate turbulence and noise. (chuffing).
A horn in front of the horn throat generates enormous pressure for high output at the horn mouth.
To cut to the bottom line, you never select a sealed solution for a sub if you have room for a bigger box. If it were not for the size issue we would not be talking about closed boxes ever.
So yes, my advice to you is to not go for a sealed solution if you have the space for something better.
The notion that sealed designs are inherently more musical is arrant nonsense.
