What is "slope"???

"Ezmeralda, Jeffrey -- thanks for the the clarification on the slope values. My memory doesn't seem to work quite as well as it once did ;-) Next time I'll confirm before I post."

You're welcome. Happens to us all. I had a poor memory when I was young, and I think as I got older, it got worse...but I can't remember. Now at 60, I have too many 'senior moments'.

So you're talking about the high-pass filter to the Thiels?

If so, my 1st response is 'why bother'? Using any of these filters introduces phase errors into the bass and midrange frequencies. Also, it sounds as if you're using one subwoof, so filtering the bass from the Thiels makes the low- and midbass mono instead of stereo.

My 2nd response is the less 'slope' (and phase errors) the better. If you feel you MUST use a hi-pass filter, use as gentle a one as you can select.

But try running them fullrange and filling just the bottom octave with the subwoof.

"Expanding just a bit on Marakanetz's response, the slope is the decrease in signal strength per octave. So a first order cross-over has a slope of -3db and it goes up from there -- second is -6, third is -12, fourth is -24. The decrease begins at a certain frequency and keeps on going from there depending on the specifics of the cross-over."

Well...not quite. First, 'slope' references the steepness of the plotted falloff of signal strength v. frequency. When someone says 'the slope of the filter', they mean the steepness of the filter when visualized (= plotted on paper). But that term is rather casual and inexact.

A filter point is defined as that frequency which is 3 decibels (dB--the 'B' is capitalized in the abbreviation because it was someone's name) above or below the zero or reference level. A 1st-order filter has a 'slope' or steepness of SIX dB per octave. That means that with a perfectly behaving low-pass filter, the signal strength one octave (= double the frequency) further up the frequency scale is now 9dB below reference level. The signal one octave higher yet (= another doubling of frequency) is another 6dB down, or a total of 15dB, and so on. For example,with a 1st-order low-pass filter of, say, 100Hz, the signal strength will be down 3dB at 100Hz, 9dB at 200Hz, 15dB at 400Hz, 21dB at 800Hz, etc. A 2nd-order filter has a slope of 12dB per octave; a 3rd-order, 18dB per octave, and so on.

In a 2nd-order filter at 100Hz, 100Hz is still down 3dB, but 200Hz is down 15dB, 400Hz is down 27dB, etc. With a 3rd-order, 200Hz is down 21dB, 400Hz is down 39dB, etc.

Higher-order (means 'higher than 1st-order') filters get rid of 'unwanted' signal to a greater degree than 1st-order filters; they're often used to increase power-handling capacity of a driver and hence a system. For instance, if one had a woofer that sounded really poor in the lower midrange because it was slow to respond to faster signals, one could use a 3rd- or 4th-order filter to keep more of the midrange out of that woofer. However, higher-order filters have increasing amounts of phase error, so there's a price to pay.

M, is this a high- or low-pass filter? Do you have large, full-range speakers or ones with relatively limited bass output? Do the main speakers have plenty of power-handling capability full range or can you overdrive them at YOUR normal, high listening levels?