Originally Posted by DanFrancis
Depends on the room, Jeff. The more filters necessary- the more memory you need. I try to stay below 80% capacity to keep the processor "happy".
DSP-3 = just like the DSP-4 but has phoenix connectors instead of XLR
DSP-30 = essentially a DSP-4 that's rack mounted
Most commercial DSPs use phoenix connectors (XLRs take up too much space)- there's no functional difference between the two: 1= shield, 2=hot, 3=negative
Little correction/addition on the above... The DSP-3 & DSP-4 share the similar package which can be mounted to the back of some QSC amplifiers. They do in fact use different A/D & D/A converters and software. The DSP-4 is a higher performance option and adds XLR connectors. Both the DSP-3 & DSP-4 need external power supplies if not used with a QSC amplifier.
The DSP-30 is mostly a rack mounted version of the DSP-3 with on-board power supply and XLR connectors. It also has a simple front button & display which allows recall of 8 different programs. Once you sort out the clunky communication with your PC and storing of the configurations, it is a very stable and reliable unit with no way for anyone to accidentally mess with settings without plugging in a computer. I have very rarely used all of the resources of the DSP-30 with only 2 channels and have never encountered any issues in utilizing the available resources. For subwoofer use, the DSP-4's advantages aren't very significant IMO.
I have 2 starter config files posted here
with more blocks than most will have need for, but it's easy to delete or move blocks as needed.
Another set of DSP products I've been eying are those from Xilica which from what I can tell, do not have any fans and offer a range of different input/output channel counts, but of course for a bit more money.
The very inexpensive Behringer DCX-2496 can be plenty functional, but should also be noted that the DSP-30 is much more flexible. The DCX-2496 is limited to a maximum filter Q of 10 and +/-15dB which can prove limiting in real rooms with strong modal peaks. Also curious is that of it's 3 XLR inputs, only 2 of the 3 can be summed at once, not all 3.