I am curious, do you find these horns throw the lows further out and, if so, what's normally the best placement to make sure I've got maximum bass in the dance area? Thanks again for all your help on this.
"Throw" when it comes to speaker cabinets is a BIG MYTH.
Folded horn subs act as low pass filters. The cabinet will not produce much beyond 200Hz.
Direct radiator subs produce harmonics of the fundamental frequencies and produce content well beyond "sub frequencies"...content to 800Hz is not uncommon.
In rooms with low(er) ceilings (or close(r) walls), which is anything shorter than one wavelength (28ft @40Hz), the reflections from the ceiling/wall are strong enough to cause cancellations with the sounds coming directly from the cabinet. These cancellations lead to the myth about "throw" or "wave formation" with subs. All subs are susceptible, but because folded horns do not produce higher frequency harmonics, the effect is more pronounced.
The sound from the subs and tops must have room to integrate at the listening position. Generally, if the subs and tops are in the same plane (e.g. up against the same wall), the closest "good" listening position will be half distance that the tops are separated. The tops should be separated by at least 22.6ft (two wavelengths @100Hz). So, if the tops are split by 22.6ft, and the subs are centered between the tops on the wall...the "good" listening space will be about 11ft from the wall. The farther apart the tops are, the farther the stand off distance. If you have a wiiiiiiiide listening area, multiple tops at 22-ish ft intervals along the long wall are best.
Best placement for subs will (almost) always be corner or wall loaded. That additional boundary reinforcement is (almost) always better for sound in the room than any other choice. In NO event should subs be placed with the radiating plane between 2.5 and 8ft from a wall or corner boundary.
Finally, while I am happy to answer general questions here...for specific questions about Bill's cabinets, the best answers will come from Bill's forum. I highly recommend signing up over there to get the best information about those cabinets.
- - - Updated - - -
If you are planning on going to four why not choose 8ohms to start then when you add the other pair just run it in parallel via a jumper from the back. Have your Builder put a Parallel output on the back for said jumper so that you do not have to run double cables, one to each box. If you are buying a new amp then also buy an amp suitable for running the pair per side. For example, if the Speaker is 300W @ 8 ohms when you add the second to each side you will have 600w at 4 ohms. Give yourself the necessary headroom so you don't run into early clipping. A 400w-500w per side into 8 ohms will more than get you covered.
Generally this is really good advice.
However, in the specific instance of Bill's folded horns, this is not a required strategy. Horn loaded subs do not distort before they blow (the folded horn path acts as a low pass filter and removes the distortion sounds). Hard limiters are REQUIRED when running folded horn subs. As a result, the amp does not need to be over-spec'd by the typical 2x RMS rule of thumb. There are good reasons to have amps with higher ratings, for instance they tend to have better heat sinks and will run cooler. Headroom is necessary in the signal path, and should be accounted for when setting the gain structure of the whole signal path.
I prefer to have 8ohm cabinets. If I need to run a "full system" (tops and subs) with a single amp, I can still have two cabinets per channel without stressing the amp.
