Getting an external crossover: worth doing?


I'm wondering whether to get an external crossover for my stereo setup, something like the Bryston 10B, and would like to get your opinions.

My setup is made of B&W 804s speakers (that go down to 30Hz -6dB, according to B&W)+ REL Storm III subwoofer, McIntosh MC275 tubed amp, a pre and a cd player.

The purpose of adding a crossover would be to relieve the MC275 and 804s from reproducing the lowest frequencies, which consume so much power, and for which neither of these products are best suited to reproduce. I've read post talking about the midrange opening up, etc.

REL recommends sending the whole-range signal to their subs, and likewise running the speakers full-range.

Then, adding an external crossover means adding more circuits to the path, and Sumiko recommends not crossing over the Storm III above 45 Hz, so I'm wondering if this is worth doing. Or in other words, how much power goes in the range up to 45 Hz?

Sorry if this is not coming up super's me not being clear with my own thoughts.

Your thoughts?
Yes it is worth doing - but only if you implement it properly! The ideal way to do it is to remove the internal crossover in your speaker, get another power amp, and go active. There are a number of theoretical advantages to doing so. In fact I am contemplating doing the same with my speaker - just saving up the pennies for another power amp and the crossovers.
Unless the speaker designer envisioned an external crossover being used, you are altering what they designed. So it's a guess as to what will happen. It may work fine or you may end up with a speaker sounding entirely different from what you had before, and from what the designer intended. It may or may not be an improvement.

Now if you multi-amp with an active crossover, that's a different story. That doesn't seem to be the intention from your post however. It seem that you are still planning to use the single amp.
Sorry my post wasn't clear.

The setup I envision: cdp > pre > crossover > MC275 > speakers
.............................................................|_powered sub

The stereo amp would continue to drive the speakers (with their internal crossovers intact), but the amp would receive a signal from the crossover that would go down to...say 45Hz only. At the same time, out of the crossover would come out another signal, 45Hz and down only, that would drive the powered amp.

So it would be bi-amping in a way, as the sub is powered.
However I'm not talking about a crossover to replace what the speakers have in them.
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After reading your follow-up i'm not so convinced if you will get much benefit from doing this. You will free up some amplifier power by removing the bass frequencies from the MC275, but this is countered by inserting more electronics in the signal path. I would agree with Bob_reynolds above, you would be better off getting a more powerful amplifier.

Your are dead on: I meant 10B sub crossover. And the benefits you describe are exactly what I'm after.

Isn't the bottom octave the 20-40 Hz range? I agree REL subs aren't ideally suited for crossing over at 70 or 80Hz, but then I'm not following you how this is bad news if I'm thinking of crossing over at say 45 Hz. I'm not disagreeing with you; just stating I'm not able to follow your reasoning. More watts would relieve the amp, but then not the speakers.

I do appreciate your input.

Thank you.
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