where do you cross over your ht setup

I'd like to add that in addition to the importance of room acoustics/speaker placement discussed above, it is also extremely important to avoid "double filtering" the audio signals to your active sub. The results can be very unpredictable if you feed a sub's filtered line-level input from a processor's filtered LFE output. (Nearly ALL receivers/processor's LFE outputs are filtered). This can either cause the dreaded bass "suckout" or "boom" even if the sub is positioned properly in the room. This is especially problematic when you set the active sub's crossover frequency close to the frequency setting in the processor. The interaction of the two filters, which may have very different characteristics (different slope, etc.), in the signal path can wreak havoc with the sound.

Many higher-quality subs offer an unfiltered line-level input for exactly this reason. It's usually labeled something like "LFE-in" or similar. Or there may be a "bypass" toggle switch you can set to bypass the sub's built-in crossover.

If your sub lacks the unfiltered input and you are going to use your processor to set the crossover point for LFE, you should turn the sub's crossover as high as it will go.

My $.02 ;)

Distortion- I'm glad to hear you heard a difference trying it this way. It never hurts to experiment!

It's just good advice I wanted to pass along that I came across on Polk Audio's website. Although I do not use Polk speakers or a Polk Sub, the information provided there applies to any speaker setup. In fact, Polk asserts that connecting your active sub via line-level cables can often sound worse than a speaker-level connection unless you do it right. This may sound counterintuitive, but his reasoning is that the speaker-level connection will avoid the filtered LFE output of most pre/pros and that any cable effects introduced are much less of a degradation to the audio signal than the double filtering of multiple crossovers in the signal path. Getting a good "blend" between your sub and mains is only made more difficult if the crossover point for LFE output is fixed at something like 80 or 100hz, as in many mid-level A/V receivers.

You can find the info at www.polkaudio.com, click on "Home Audio" then "Setting up a home theater system" under the FAQ's & Advice section. You can find a fairly detailed explanation of why it's bad to "stack" filters there as well. Check it out.. it's a good read even for seasoned audiophiles.

Exertfluffer- I agree with your points above and I have very much enjoyed your posts. I just mentioned the speaker-level connection scenario in my post to illustrate a point that Polk makes that there are often several options available for working around "double filtering" and connecting an active sub to a system and the LFE-OUT is not ALWAYS the best choice in certain situations. Certain connection options (like speaker-level) that are seldom considered by many people can often work very well depending on your particular type of speakers, etc. I agree that it's not necessarily the BEST choice for HT in the assumed 5.1 system, but as we both have both stated above (either literally or inferred), it can pay BIG dividends if you take the time to experiment and learn exactly what you are dealing with within your own system.

I fully agree with your recommendations as they pertain specifically to 5.1 discreet HT. However, the Polk recommendations I paraphrased above were taken somewhat out of context and were a bit generalized. The Polk website covers many scenarios including using a sub just for 2-channel music, sub-sat systems vs. full range mains+sub, etc. but I did not want to repeat the whole article word-for-word in my post.

But I do think it's important for people to be aware of the problems that cascading filters can cause(that hard-to-nail-down "hump" or "hole" in the mid-bass, for example) and that often people aren't even aware that this MAY be the culprit (or a contibuting factor) in their HT setups.. And it was not being mentioned prior to my post.

Cheers! JZ

Here we go again!.. I've been pondering much of what has been said above on this subject and decided to do some more checking on the matter. Here's an excerpt of an email I sent my friend regarding this dilemma and his reply. Said friend works very closely with the engineer who helped create the spec for THX Ultra2 (among other projects) in the Bay Area. Names have been changed to protect the innocent. To wit:

Dear Mr. X,
I have a quick tech question for you regarding THX
equipped processors/receivers. There's been a lively
thread on Audiogon.com in the "Home Theater"
discussion forum regarding where to properly set the
crossover for bass management for movies and home
theater. There's lots of debate regarding why it's
better to set your crossover to 80hz and set your
speakers to "small" (even if you run "large" front
speakers) to maximize dynamic range. Others say it's
better to set the crossover lower depending on where
the main speakers rolloff.

Correct me if I'm wrong, but isn't it true that
regardless what type of speakers you tell your Dolby
Digital processor you have (large or small) and where
you set the crossover point for bass during initial
setup, doesn't THX override those settings and default
back to an 80hz crossover, set all speakers to
"small", and route (or "sum") all LFE to the active
sub when THX processing is engaged? It seems to me
that's the only way THX could reasonably ensure proper bass
management and to coax the maximum dynamic range from
a 100 or 120-watt THX-equipped receiver which most likely will be used in a
variety of potential systems with different
brands/specs of speakers, room size, etc.
I'd love to hear your thoughts on this!

Mr. X's reply:

"Regarding your question, funny thing, (name omitted) called last week
with
the same question. You are correct, the crossover point is 80hz, no
matter
what size speaker is being used. As for your explanation, you nailed
it on
the head." (End)

I hope this helps to clear the air at least a little bit especially for those running receivers and/or processors equipped with THX processing. If max dynamic range is your goal for movies and HT, THX knows a thing or two about helping you get there!

Cheers!
JZ