Integrating Dayton RSS390HF-4 IB with Open Baffle Mains

[sharpi31]

I recently invested in a Behringer DCX2496 to allow me to integrate my 160L sealed RSS390HF-4 sub with my Martin King 2-way open baffles. I'd be grateful for any advice on crossover slopes etc.

The OBs are exactly as detailed in Martin's white paper: http://www.quarter-wave.com/OBs/OB_Design.pdf except I used the FF85K rather than the specified FE103E. The passive crossover is 2nd order at 200Hz for the Alpha 15a, and 500Hz 2nd order for the FF85K. My plan is to stick to these values when I go active with the DCX2496.

Assuming I keep the 2nd order crossover for the mains, would I be best to use a 2nd order crossover for crossing over to the sub?

According to Martin's paper the Alpha 15a will roll off at approx 18dB per octave below 50Hz or so.

I'm tempted to roll the OBs off early to avoid over excursion. Instincts tell me to aim for around 100Hz 2nd order crossover to the sub - does this sound right?

The sub will be placed directly inbetween the two OBs equidistant from the hot seat. The DCX2496 will soon be weighed down with six Jensen transformers when I convert it for passive transformer output on all channels.

Is there anything else I need to consider to successfully combine OB mains with an IB sub? Any suggestions or advice would be gratefully received.

[matevana]

The passive crossover is 2nd order at 200Hz for the Alpha 15a, and 500Hz 2nd order for the FF85K. My plan is to stick to these values when I go active with the DCX2496.

Here's something you may want to try once you gain the extra utility from the DCX. It has worked very well for me, and really speaks to the power curve issues of the three drivers. This is assuming your OB is by-amped; if not, try using an inexpensive Dayton T-amp (Dta-100a) on the Fountek driver... I think you will be very impressed.

Try crosing the Alphas at 500Hz, 24dB/oct, the Founteks at 500Hz, 12dB/oct and the sub @ 100Hz, 24 db/oct. If you room characteristics are similar to mine, you will notice greatly improved "thwack" in the lower mids. You may need to put a slight notch (-3dB somewhere between 400Hz-630Hz) with the DCX's parametric compensation if you find it a bit boomy, but this should only be needed if the room is fairly reflective. I think you will notice a big improvement in the handoff between drivers. I find that I favor the sub for movies, but generally leave it off for music.