Cross over frequency ???

Kg: If you cross your monitors over at 80 Hz @ 24 dB's, that means that the signal is down -24 dB's at 40 Hz, -12 dB's at 60 Hz, -6 dB's at 70 Hz and "flat" at 80 Hz. At the same time, your sub is running at full output at 70 - 80 Hz, so the monitors are adding to what the subs are already contributing there. Even though the monitors are "sloping down", the amount of output that they can contribute may be too much for the room when combined with the subs. On top of that and as you can hear by ear, the amount of output that the speakers are required to make with that crossover frequency selected is still putting a strain on them.

If possible, you might want to select "small" speakers for the monitors and then tinker with the crossover point for the subwoofer. This should roll the monitors off a little quicker and clean them up while letting you fine tune the contribution of the subwoofers to a greater extent. I don't know if your Pre / Pro will allow you to take this route, but it might be worth checking out.

As a side note, placing the subs in the corner will give you the most reinforcement at low frequencies. While i've no doubt that you can shake the room like this, bass transients, pitch and definition typically suffer in such an installation. I would encourage you to do some further reading on the subject and do some personal experimentation with your installation. If you are using this system primarily for HT, it may be fine the way that it is with the subs in the corner. If you are using the subs to listen to a lot of music, i'm near certain that you can do better. Whether or not where the subs need to be place is convenient is an entirely different matter : ) Sean
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All of the above is good advise and sound theory. Give it a try. However, my experience has led me to a somewhat different approach.

First, turn off the main speakers and, with the crossover set to 90 Hz or thereabouts, listen to some music. "What music" you say. Yes it's true that most of the time nothing will be coming out of the subwoofer. (Dirty little fact).

Secondly, search through your recordings and find one that does have signal below 90 Hz. How does it sound? Do you really want that in your mains?

Thirdly, think about the high frequency capability of your subwoofer. Is it really all washed up at 100Hz?

Obviously what I am driving at is the suggestion that the 50Hz subwoofer crossover frequency often suggested is too low, at least for my particular system. My subwoofers are my own design, and include 15 inch JBL drivers which are good to 800 Hz, so 90 Hz is a walk in the park. (The somewhat deficient range below 30 Hz is filled in with 12 inch specialized subwoofer drivers). Although most commercially available subwoofers don't claim to go higher than 200Hz or so, limiting them to 50 Hz is unnecessary.

IMHO no aspect of audio exhibits greater disparity between theory and practical tweeking based on listening than does the subwoofer. I am not alone in noting that precisely measured (with a warble tone) flat response to 20 Hz often sounds deficient when music is played.

Finally, with regard to overlap/gap of crossover frequency: I have obtained Marchand electronics modules which have an interesting feature. It is a control that provides a bandpass boost or cut at the crossover frequency. This is supposed to take care of the problems around crossover noted by sean. I have not got the things wired up yet, but I am anxious to see how this feature works.

El: The Marchand "blending control" or "damping" adjustment as Phil calls it works fabulously. I'm sure that you'll be happy with this once you get it running. Sean
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OK.What I did was run the mains and rest of the system ie. center and surrounds xover at 80hz.With the sub off I listened to a few well known sound tracks.Trying to ignore the unbalance sound it did not have that chesty sound I disliked before.It was tight and free from the peaks in the bass.It would appear that is my starting point.It also had tons of head room and only began to show signs of distress above 100db,well above my usual listening.Setting the xover higher also yeilded the same results.Gave me more headroom and my 6.5 inch drivers were very happy.I will go rent a pro xover this weekend and ease the subs into the system until I feel they are making a contrabution not an over statement.I never tryed to solve this problem from up high first and then the subs.This makes so much sense.Keep in mind I am stuck with the 24db high pass coming out of the processer.Thanx I'll keep you guys posted.

Kgveteran: Glad you are making progress. It's always good to hear that someone is willing to experiment and learn on their own AND the results that they obtain from doing such are to their liking. This can only encourage that person and others that may be sharing those experiences through forums like these. It is stuff like this that makes me happiest when it comes to various threads in these forums. Well, that and people sending me boxes of money : )

As a side note, any professional crossover that you get is likely to use either XLR's or 1/4" ( mono headphone ) jacks. As such, you'll probably have to stop by the "Shack" and grab some 1/4" male mono headphone jacks to female RCA jack adapters. You might also be able to find these at a store that sells musical instruments ala Guitar Center, Sam Ash, etc.... It's quite possible that wherever you go to rent the crossover may have adapters that they'll lend you.

By the way, find out what the slope is on the crossover that you end up renting is. Some have variable slopes along with hinge frequencies. You'll probably find that a higher frequency crossover requires a sharper slope and that a lower frequency with a shallower slope can work too. Strictly a matter of trial and error here to see what works best with your gear, room and ears. Sean
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