I currently use a Mirage BPS-150i.
I have the line out from the receiver go into it and then send the signal out after the crossover to the amp powering the mains.
For me, this method seems to make the sub blend best with the mains.

I just scored a BPS-400 and want to use this for the very low end.
My plan is to stack the two and route the signal the same way as before but through 2 subs....like this:

receiver line out > BPS-400 (big sub)
BPS-400 line out (after crossover) > BPS-150 (smaller sub)
BPS-150i line out (after crossover) > amp > mains.

But, this seems like a long signal path with a lot of electronics in between.

So, I am now thinking of keeping things the way they are but sending the LFE on the receiver to the BPS-400.

Any opinions on either of these 2 methods?

I would also like to know what people think about stacking them vs spreading them.

I was basically thinking that by stacking and making sure that they didn't share the same frequencies, that I would be fairly safe of cancellation and they would act like one sub.

Thanks in advance!

Give it a try and let us know how it turns out. If you really serious about stacking them then run and RTA on your room and make sure everything is tuned properly.

If you already have the subs then, it's not like your talking and arm and leg investment. Just some cables. Experiment and play with the positioning.

You prob have the cables laying around. I mean really, what's the investment. Play with them.

Unless the subs sound almost identical, your best bet with any pair of non-identical subs is to co-locate them -- that way you don't have to contend with one sound from one place and another sound from another.

Another advantage of co-location is that it gives you an additional 3 dB gain over widely separating them -- and with small subs that comes in handy!

I'm gathering you don't have a sub/mains crossover in your receiver/preamp -- if you do you should use it instead of the crossover on the plate amp of one of the subs.

If for some reason you have to use a plate amp crossover to high-pass the signal to your mains, you just use one of your plate amp crossovers. The signal to your mains should then come in to one sub's inputs, and out from that sub's outputs to your mains amp(s). Make SURE your subs HAVE high pass filters on the RCA (low level) outs -- most sub RCA outs are not high passed at all, merely daisy chained to the RCA ins. SVS is an exception to this, their RCA outs have a fixed 80Hz high pass. There are three possibilities:
1. The RCA outs are daisy chained to the RCA ins
2. The RCA outs have a fixed high pass frequency (you need to find out what frequency)
3. (Rarely if ever) The RCA outs have a variable high pass filter set with the knob on yor sub

You want to select ONE crossover frequency (start with 80Hz unless you know otherwise for your system) and have both subs roll on at that frequency as your mains roll off at that same frequency. Usually you do this by using a Y connector to send the same input signal to both subs -- unless you find out your subs' RCA outs are straight through (no filter), in which case you can use them to daisy chain the subs -- but then you'll need to find another way to high pass your mains. ACI and other vendors sell inexpensive in-line fixed high pass filters you could use in this case.

If you could post back and let us know what equipment you have and if the RCA outs on your subs are high pass filtered or not it would help. :)

why couldn't you use a splitter after the first sub like this:

............................../----> amps -> main
receiver out -> sub 1 |
..............................\----> sub 2

EDIT: the more that i think about it, why not just split the signal off the receiver?

when you can't get them to couple together properly

use the good one as your main sub and use the lesser one on your surround channels :)

The smaller sub (BPS-150i) is very musical and blends well with my mains.
Because of that, I want to use this one for most the bass that will be found in music and use the larger sub (BPS-400) mainly for the LF for movies.
Both these subs are made by Mirage and are from the same series, so I think they should work together pretty well. My plan is to set the crossovers so that neither of them share the same frequency range.

Perhaps something like this:
Big one: for below 35
Small one: 35-80
Mains: 80 and up

My receiver is a Yamaha (I really need a new receiver!) and it has 2 sub outs in mono but it has a built it high pass at 90 that is not adjustable.
The line level out of the BPS-150i is set at 80.

The BPS-150i also has speaker level ins and outs that passes through the crossover circuit.

According to the manual:
"The High Level inputs allow you to connect your subwoofer to the speaker outputs of any A/V receiver or power amplifier. The signal from the high level output terminals passes through a built in high pass filter. When these terminals are connected to your main/satellite speakers the result is increased dynamic range and power handling, which improves overall system performance."

Is this true? I thought it was a better idea to make longer runs with the low level RCA than with speaker cable?

BTW, I don't use the amp circuit in the receiver for my mains. I have a threshold 400a handling those.

I don't have much info on the BPS-400 yet because I have not picked it up, but from the info on Mirage's website, it looks like it only has a RCA LFE in.