How would you do this crossover bass + subwoofer thing
 

Due to space constraints I need monitors for recording in two rooms in my house. I have "real" studio monitors with a subwoofer in one room. The other room has no subwoofer yet. I would really like to combine that with a basic bass rig. Something like a 1x 15 that I can use both as a subwoofer for the full-range outfit and that I can take to jamming (I don't gig right now and don't expect to anytime soon).

Is that realistic? I have spare EQ capacity to get the frequency response in line and I don't need high volume at the same time as flat response.

If so, the gritty detail question goes like this. For the studio monitor subwoofers the (stereo) frequency crossover is inside the (mono) sub. I would need a separate crossover with the ability to merge the lows into mono. I want to avoid having separate rack space for crossover and amp. I wonder whether there's a 200W or so P.A. amp that has such a crossover built in? The ones I have seen (Crown) do not do the right stereo + merge crossover trick.

So I am looking for either a 1/2 width 19" unit crossover, or an active subwoofer. Or I could use a 1x15 bass amp. In general I prefer non-combos/not active but only if I can squeeze things in the rack.

Any thoughts?

Well full range speakers are not sub-woofers. Most full range speakers will not go to the sub-lows of a sub-woofer. They will get close but still be at least an octave from sub-woofer territory.

If you go the other way, a sub-woofer isn't going to get the high end extension that a full range speaker will give you.

It seems like you are making a lot of compromises by doing something like this.

I should have clarified that the frequencies > 100 Hz are covered by shelf monitors and that for bass alone I know I'd be happy with e.g. a EV 15L (not sure about the 15B but anyway). This is only about subwoofing.

So you will have additional speakers for the jamming rig as well?

The 15L only goes down to 60Hz. That isn't much of a subwoofer.

Use quality studio monitors, satellite and sub, then with your DAW use cabinet emulation for a bass rig.

If you can't afford 2 subs, one for each room, you could carry it from room to room. A sub can match many satellites. There's not of matching you need to do for sub other than DB.

I am still not entirely sure what you are asking for but let me try to break down what is going on.

You have 1 room that has studio monitors and a subwoofer, a second room with monitors but no subwoofer that you want a subwoofer for, and you want a bass rig to take to other locations so you can jam with friends. The rig does not need gig volume. Are these your goals, or am I misreading you?

If I am correct in what you are trying to do here are the problems.

If you use a bass amp as your sub for the second room it likely will not put out true sub frequencies. The Fearful designs are some of the lowest tuned bass amps around and they only go to about 40Hz. If you check out commercially available studio subs even the least expensive will go to the low 30s because they are using a dedicated subwoofer speaker not a full range speaker (like the EV 15L) or a super 15 (like the 3015LF in the Fearful).

So perhaps you just want more bass in the second room. Well you need a design that is as flat as possible or you will be getting an inaccurate sonic picture and your studios monitors will lose what studio monitors are supposed to do, be accurate.

If you use a dedicated subwoofer as a bass amp you will need a mid driver because most subwoofers only go to a couple hundred Hz.

The absolute best scenario I can think of if you HAD to do this would be to get a multi-way custom built bass cabinet like a fearful and have two separate inputs installed one normal and one that bypasses the crossover and mid and or tweeter. Then you could buy a power amp with a built in crossover and have some sort of amp sim to get a good tone. This obviously is not a good scenario.

If I were you I would buy one of the cheapest studio grade subs (about $400) which will give you better low end extension than almost any bass cab (though not nearly as much volume but that is not needed in a studio monitor), and a combo or amp cab.

I know this is not the answer you want but if you try and do double duty you will be limiting the lowend extension and accuracy of your monitoring system, and have some cobbled together, not very easily portable bass rig.

I think this misunderstanding here is about the need for accurate monitoring. Upstairs has fine enough monitoring with a 10" JBL subwoofer. I can live without < 40 Hz downstairs. Right now it has a set of Rokit 6 only, so anything will be an improvement. I mostly mix with headphones anyway.

My question was more aimed at the equipment section. 1/2 width crossover with mono sub functionality, or a 19" power amp with such crossover built in.

I know I will be fine with just a 15L playing bass with people because that's what I had long ago.