Active biamping question

[Jmodified]

Recently, actively, vertically bi-amped from a Marantz AV8003 balanced outs to a Rane MX-22 2 channel active crossover to 2, 250 wpc Class D Audio

kit amps. I have an outboard passive crossover that i built for my KLF-20'S utilizing crites autoformers. I disconnected the crossever to the woofer section and have the woofers wired directly to my amps. The closest crossover freq. on the active is 875hz, the factory on the klf's is 800. I am still using the mid and high crossover section of the outboard speaker crossover. My question is should i calculate and change the capacitor value going to the midrange autoformer to 875hz instead of the 800hz? Will this make an audible difference? I assume that i am doubling the 875 hz playing from the woofers and the midrange, the difference between 875 and 800 with the extra 75 hz bieng played by both. The rane is a 24 slope.

Thanks in advance for any suggestions!

[Jmodified]

One thing I forgot to mention is that I ran the Audessy setup on my Marantz and looked at the auto eq curve and it is fairly flat except it set the 500hz to 1k

down 3db which i think may be an indication that the 800- 875hz region bieng duplicated by the mid and woofers may be a problem. Maybe I am bieng a bit critical here, it sounds awesome, very dynamic and soundstage is excellent.

Thanks again!

[Don Richard]

The crossover frequencies on that unit are not exact and may vary +/- 10% from what the knob setting says, perhaps more on a unit of earlier manufacture. You might not be far off at all or could be off quite a bit. There are tolerances on the passive crossover as well. If you like the way it sounds, don't worry about it.

[Jmodified]

Thanks, I rebuilt the Rane with new regs, +15 and -15 are dexa discreet. Schottky diodes, Nichicon kgs for electrolytics and Nichicon bp's for all of the rest.

I am considering a pair of RF-7II's and ditching the crossover for a real active bi-amp setup.

Always items on the upgrade list!

Thanks for the reply!

[MikeFord]

Something to consider when converting from a passive to an active crossover is that the reactive components of the passive crossover interact with the impedance of the driver in often complex fashions beyond the crossover function.

[Jmodified]

Thanks for the reply. So you prefer the active route? This is my first attempt at active bi-amping

and I have to say that the biggest difference i notice is in the bass control, it is rock solid, almost subwoofer like. The sound seems fuller and very dynamic.

Since the Klf's are 3 ways and i only have them bi-amped, I left the mid and high crossover section intact and removed the inductor from the woofer section.

Sounds great imho.

[MikeFord]

Bass I think clearly benefits from a direct connection to the amp, how to do the mids and highs is more a case by case descision. What some like to do with midrange up is to make a zoebel network to even out the impedance, but do the crossover function electronically or digitally.

[WMcD]

We all want things to be perfect for our babies. In this case, I think you are best off sticking with something which works.

The theory of crossover points involves consideration of the phase of the acoustic outputs where there is some overlap and this is very difficult to measure and predict. So it is difficult to measure what you have, and what you'll have if you change things even with the best of equipment.

It is also interesting to look at the band of freqs that we are considering here, about 10% of the frequency.

Please see my post http://forums.klipsch.com/forums/p/21216/171695.aspx

It has a very nice diagram by Harry Olson (I can't find anything quite as clear on the Internet and it is a gem of information) showing the freqs of the notes on the musical scale and the piano. BTW the gif has a good deal of resolution which you can copy and download -- or enlarge on your browser.

Essentially, if we are talking about a 10% change in freq, that is less than one whole note on the scale in any octave.

We're looking at going from G to A (one note) at appoximately the 800 Hz area.

WMcD

[Jmodified]

Thanks for the reply, very informative chart. It sounds excellent and have way more clean power than I know what to do with!

I really like the active bi-amping. Made more of a difference than I expected. Dont think i will ever go any other route. Wish i would have held on to my cf-3's, would have been perfect for my current setup.

[MikeFord]

The theory of crossover points involves consideration of the phase of the acoustic outputs where there is some overlap and this is very difficult to measure and predict. So it is difficult to measure what you have, and what you'll have if you change things even with the best of equipment.

It is also interesting to look at the band of freqs that we are considering here, about 10% of the frequency.

What can be difficult are sounds we know well that transition the crossover point, like a female vocal and a rising note. You really don't want "anything" to happen at the crossover point, but your ear does seem to get used to a bit of funny business. Listening to a 2 way speaker or a full range, and then going back to a 3 or 4 way speaker and you may notice the crossover points.