Bi-amping & "internal speaker crossover" ???

Ellen Degenerate

Novice Member
Sorry to disappoint everyone who clicked this READY 2 RAGE. I've done a bit of research & have found that "passive bi-amping" is effectively pointless. I just like to know how things work, and had a question:

I own a pair of Klipsch RP-260Fs. Removing their terminal connecting bar definitely results in the top binding posts powering the tweeter, and the bottom posts powering the woofers. I saw someone on the internet trying to bi-amp a similar setup, and one of the respondents stated that he'd still be running the signal "through the passive crossover network of the tower - defeating the whole purpose."

If removing the terminal connecting bar allows you to power tweeter & woofers individually, how does this "passive crossover network" ever come into play?

Thanks!
 

Conrad

Moderator
The issue is that you're still sending a full range signal from the amp to the speakers.

If you connect that output to the HF terminals on the speakers then the crossover is discarding everything below the crossover frequency and only sending the HF signal to the tweeter. You know this is happening as your tweeter didn't blow :)

Just because you're only connecting one set of terminals doesn't mean that you're not going through the crossover. You can also confirm this as, when you have the bridiging plates in place, you can connect the speaker cable to either the HF or LF terminals (or one HF and one LF) and both HF and LF will play. This is because the signal from the speaker terminal is being fed to the input of the crossover, split, and routed to the appropriate driver(s).

The benefit of an active crossover is that you're only amplifying the portion of the frequency range that the driver your amp is connected to can use. Each octave (doubling of frequency) takes about the same amount of power to drive to the same level. So 5kHz - 10kHz takes the same power as 10kHz to 20kHz. This is why subs have such large amps for such a small range.

If you can actively bi-amp and send only the frequency range above the crossover to the amp then the amp is only amplifying that range and sending it on to the speaker. Nothing is wasted and the full power of the amp is used across only the range that's being used by the speaker. The same is true for below the crossover. In my speakers the LF/Mid Crossover is about 2.5kHz, so if I actively bi-amp them the LF amp would only be amplifying 40-2.5kHz (about 6 octaves) where the HF amp is doing 2.5kHz to 20kHz (4 octaves).

However, to do this well, you need to bypass or remove the crossover in the speakers.
I tried it using a minidsp to implement a crossover before a pair of power amps which were then connected to the HF and LF terminals respectively. It did not go well. I found that I had to set the minidsp crossover about 3 octaves above and below the crossover to have them not interfere with the in-built crossovers in the speakers. Given that the low end is where you want to reduce the power usage, and given that 3 octaves is 1/2 of the total LF range, it didn't make much sense. It also didn't make much difference in terms of sound quality.
 

Ellen Degenerate

Novice Member
Gotcha... so, the crossover inside the speaker is doing its job at all times, regardless - it's just that there's nothing to send the signal "to" when either HF or LF is "disabled," like in my experiment?
 

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