[uncola]

So I have these these drivers:
2 chinese bg neo3 pdr tweeters 4 ohm 93db
2 lii audio fast8 fullrange 8" 8 ohm 94db
2 speakeraddict 8 ohm 10.5" woofers 82db

I was going to do 3 way open baffle speakers for a small room with 3 stereo amps and a 3 way dsp box.. but I realized the woofers sensitivity is too low to match the other drivers.
Should I parallel the woofers to get to 85 db, then use the DSP to reduce the tweeter and fullrange down to 85db?   and get 2 more woofers for the 2nd speaker?  or should I just not use these woofers and get two Eminance Beta15 woofers at 98db?
edit: I see everyone lowers gain to match the lowest sensitivity driver in their speakers.. what are the issues with increasing gain for the low sensitivity woofer to make it match the mid and tweeter?

[mcgsxr]

When I mated active woofers with OB mains they did not match in terms of sensitivity.  I raised the gain of the woofer amp to match.

As long as the noise floor in the woofer amp is low enough it won’t matter. 

Using a DSP you may be able to change the gain at the rca outputs to the woofer amp.  Useful if so.

[brj]

Paralleling the low end is a good start, as getting as close as you can between driver sensitivities will help.

My (non OB) active system has an 8 dB sensitivity difference between the tweeter and woofer.  I need to pad down my 103 db/1w/1m tweeter by 8 dB to match my 95 dB/1w/1m woofer.  While I implement my driver EQ digitally via convolved IR filter, I implement the crossover right before the amps in the analog domain via Pass XVR-1.  Using my measurement rig, I was able to dial in the 8 dB delta exactly using the attenuators on the front of the Pass.  Once I figured out the ratio, I then played with dialing them both up until the woofer attenuator maxed out, and then both down until the tweeter attenuator bottomed out.  I have enough total gain in my system that I ended up setting them with the tweeter attenuator bottomed out, as this was the (slightly) lower noise configuration, and I have plenty of volume range on my autoformer pre-amp.

You could perform a similar experiment with the DSP (at low to moderate volumes), and then pad down the other drivers with a suitable resistor to minimize the gain differences needed in the digital domain.  You want to make sure that at high volume, you don't run into digital clipping on the woofer if you increase its gain digitally.  In general, I'm very hesitant to increase gain digitally.