hi Dan,
there are a few different answers to your question depending on the context of the question.
--after reading other posts and questions of yours it appears that you are asking about subwoofer integration for a 2-channel analog system and not Home Theatre from a processor. is that correct?
assuming that my interpretation of your situation is correct; then the answer to your question would depend on the output choices of your preamp and the adjustments available on your subwoofer.
there are a very few analog preamps which allow for multiple outputs that split the frequencies (and the only one i know about is $25k). so if you want to filter the bass output of your main speakers it will need to be done in another way.
one way is to use an external crossover as you mention. personally i don't like that as it comes with a sonic cost.
another way is to use a subwoofer which has a high pass filter and then simply lower the filter on the sub until you have optimal bass integration. this is the most common way to integrate a sub into a 2-channel analog system. your preamp either has two analog outputs or you use a 'Y' connector. personally; i've not heard a system done this way which intergates 'good enough' for my tastes but many people are very happy with this approach.
another version of that approach is to actually connect your subwoofer directly to the speaker terminal on your main amplifier with a high current Neurick connector. there are a few subs which have a high level input and can be connected this way. this does have the advantage of taking the signal from the main amplifier and so the bass character seems to better integrate.
personally; in a way i have a similar setup as my last description. my speakers, the Evolution Acoustics MM3's, have powered integrated subwoofers which take their signal from the main speaker terminal. they use a ICE based digital amp to power the subs and it sounds perfectly integrated and goes to 10hz flat in my room.
if your subwoofer does not have a way to adjust the crossover frequency then don't attempt to try to intergrate it with a full range speaker.
finally; if you are not using a subwoofer and just want to reduce the strain on your speakers by limiting the low frequencies, don't worry about it. the roll off of your speakers will do that anyway. they will output some signal at frequencies way below what you hear that will have benefits.
if you describe the exact gear you have it will be easier to give specific advice.
there are a few different answers to your question depending on the context of the question.
--after reading other posts and questions of yours it appears that you are asking about subwoofer integration for a 2-channel analog system and not Home Theatre from a processor. is that correct?
assuming that my interpretation of your situation is correct; then the answer to your question would depend on the output choices of your preamp and the adjustments available on your subwoofer.
there are a very few analog preamps which allow for multiple outputs that split the frequencies (and the only one i know about is $25k). so if you want to filter the bass output of your main speakers it will need to be done in another way.
one way is to use an external crossover as you mention. personally i don't like that as it comes with a sonic cost.
another way is to use a subwoofer which has a high pass filter and then simply lower the filter on the sub until you have optimal bass integration. this is the most common way to integrate a sub into a 2-channel analog system. your preamp either has two analog outputs or you use a 'Y' connector. personally; i've not heard a system done this way which intergates 'good enough' for my tastes but many people are very happy with this approach.
another version of that approach is to actually connect your subwoofer directly to the speaker terminal on your main amplifier with a high current Neurick connector. there are a few subs which have a high level input and can be connected this way. this does have the advantage of taking the signal from the main amplifier and so the bass character seems to better integrate.
personally; in a way i have a similar setup as my last description. my speakers, the Evolution Acoustics MM3's, have powered integrated subwoofers which take their signal from the main speaker terminal. they use a ICE based digital amp to power the subs and it sounds perfectly integrated and goes to 10hz flat in my room.
if your subwoofer does not have a way to adjust the crossover frequency then don't attempt to try to intergrate it with a full range speaker.
finally; if you are not using a subwoofer and just want to reduce the strain on your speakers by limiting the low frequencies, don't worry about it. the roll off of your speakers will do that anyway. they will output some signal at frequencies way below what you hear that will have benefits.
if you describe the exact gear you have it will be easier to give specific advice.