Integrating subs for 2 channel

[Learning]

I'm building a system using a citation 5.1 (4x100 or 2x300), a tube preamp (either SF Line 1 or AI Mod 3a, still deciding), and Magnepan MMGs. My room is smallish, so the larger Magnepans are out, but I want to try the speaker for a while.

Only problem is that the MMGs only go down to 50Hz, so I will need to add a sub(s). The analog preamps only have 2 channels with no bass mgmt.

How do I integrate woofers into this setup? Can I use a single sub? If so, How? Otherwise if I need two subs (how about two used 10" NHTs?) how do I go about delivering the right freqs to the four speakers?

I know I'll have to fool around with placement and setup, but what do I need to start?

Help!

[ThomasW]

Here's the theoritical "idea" setup for seamless subs.

1)A single Sub should be placed centered, left to right and front to back with the "mains". Now this won't give the max output (corner loading does that) but it is the most "forgiving" placement for higher XO frequencies ie 100Hz. Center placement prevents "smearing" of the stereo image, if higher XO frequencies are used.

If you use two subs, you can simply place your MMG's on top of them. And position them for best imaging from the MMG's.

2)You'll need to be careful chosing a crossover frequency. The "mains" should be capable of good output to one full octave below the XO point. And like wise the sub should be capable of good output to one full octave above the XO point.

For example the MMG's go to roughly 50Hz. They should then be crossover at 100Hz. A sub to match these should have good output to 200Hz.

This "criteria" prevents a "suckout" from occuring at the XO frequency.

You'll need either a sub with a built in crossover or an external active XO for use with the pre-amp. Here's a link to one source of very good active external XO's. Sorry they aren't cheap.

http://www.marchandelec.com/xm9.htm

Here's a link to a very inexpensive DIY kit.

http://members.aol.com/johnpomann/speakers/crossover.htm

10" drivers in general don't have a low enough Fs or move enough air to be real subs. Remember 2-10"s are smaller than 1-12", when you calculate the "swept volume" of air displaced. You would be better off with something like a Shiva, or the Shiva clone from Parts Express. Or one of the other "new generation" of high excursion 12"s. These will easily go to 200Hz, so they are fine for a 100Hz XO point




theAudioWorx
Klone-Audio

[JonMarsh]

Thomas is the man, and his advice is very sound. (no pun intended). Remember, both the maggies, and subs with drivers like the Shiva, are a bit on the inefficient side, so plan to have a few watts available to drive them.

Someday, if you wanted to try something more radical, and maintain dipole bass well into the low end, you could consider a dipole woofer using Shiva's or the new Adire 15" driver, with a Marchand Basis to do the LF EQ chores. What earthly benefit would that have? Only that it would maintain the figure eight radiation pattern of a dipole speaker like the maggies, which minimizes room interaction. It's something I'm playing with, and it's the principle upon which ThomasW's Whisper clones are based (the dipole speaker thing). Thomas doesn't run his Whisper clones low, though, and crosses over from them to a sub- but they'll do 40 - 50 OK without EQ.
Anyway, enjoy your MMG's- they're sweet speakers, and it sounds like you'll have a real nice system when you're done.

Regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....