Is bi amping worth it ?

@billpete  Active crossovers and equalizers are totally different animals.  Let's first understand the difference between active and passive crossovers.  A passive crossover is an electronic circuit that has no power supply.  It is just a circuit that sits between the output of your amplifier and the loudspeaker drivers.  

An active crossover has a power supply like your preamp and power amp, and sits between your preamp and multiple power amps.

An equalizer is a device with a power supply, that typically is located on an extermal processor loop on your preamp, or a tape recorder loop on your preamp. 

The do very different things.  An equalizer alters the system response.  Typically the operate on ten bands across the audio spectrum.  

A crossover, either passive or active, is designed to separate out the signals being sent to the loudspeaker drivers.  High frequencies for the tweeter and low frequencies for the bass driver.  If you have a 3-way system, then the crossover has the added function of allowing only an intended band of signals for the mid-range driver.

Most loudspeakers use a passive crossover.  The user has a preamp & power amp, or an intergrated amp or receiver, and run one speaker line to the speaker.

In a system with an active crossover, the preamp sends a line level signal to the active crossover, which then outputs line level signals that have only those frequencies suitable for the given driver.  If you had a 3-way system, then on each side, the active crossover would have 3 line level output signals for 3 separate amplifiers, each of which powers a single driver.

The more expensive amplifiers are very good at managing the very complex impedances typical of loudspeakers with passive crossovers.  

Less expensive amplifiers can do a very good job if they are only powering a single driver and do not have to cope with the complex loads that a passive crossover have.

I run a set of Linkwitz Orion loudspeakers, which have an active crossover.  I use a B&K AV1260 power amp which has 12 channels at 60 watts/channel.  Each side of my speaker has two tweeters run in parallel, a mid-bass driver and two 10" bass drivers.  There is one amp channel for the tweeters, the mid-bass driver and each of the 10" bass drivers.  B&K made MOSFET amps that were well thought of in their day, but was never seen in the same class as Mark Levinson, Bryston, McIntosh, etc.  Being that my amp channels don't have to deal with a passive crossover, they do a very good job.  I *LOVE* my system.

@russbutton Nice explanation, thank you. So, why is a Krell amp better suited to run a 3 or 4 way system with passive crossover? I believe that my Parasound amps do a very fine job of powering the AR9's. They are 4 way with 2x12 wooferrs each on the low side, the top is made up of a low midrange driver (8 inch, I think), upper midrange driver and a tweeter. There are 3 toggle switches in each cabinet, allowing control of bass, midrange and treble. You can set at zero, minus 3db or minus 6db to adjust mostly for room acoustics, I would imagine. I currently have them all at zero.

I am not in any way questioning your answers, just trying to understand why. BTW, good job explaining to someone with very limited knowledge of the components. I do understand the basics but most of the EE stuff is well over my head. Thanks again.

@billpete I believe that John Curl is the chief designer for Parasound, so their amps are going to be very good.  I don't know that Krell is better than Parasound.  I just know that they are more expensive.  I like to say that today's $10,000 wonder is tomorrow's $5500 white elephant.  

Chances are if you were to sub in a Krell amp into your system, that it would sound a bit different.  Depending upon your opinion, it might be better or not.  It's my expectation that the difference between your Parasound and a Krell would not be huge.  But if you were to compare either of them to an amp from someone like Adcom or Cambridge Audio, that you would hear greater differences.   I think that Parasound is closer to Krell than it is to Adcom.

But were you to remove your passive crossover altogether and replace it with an active crossover, a pile of Adcom amps and level match them properly, you'd be surprised at how good it would sound.  

In practice with home systems, it is mostly in DIY builds that you see people using active crossovers and a pile of lower cost amps.  You really can't sell a commercial loudspeaker and then tell the customer they have to buy an active crossover, a pile of low cost amps and be sure to level match them when they get home.

Pro audio systems have been doing active crossovers for decades.

@ditusa --

+1

@russbutton --

+1

@russbutton wrote:

The do very different things.  An equalizer alters the system response.  Typically the operate on ten bands across the audio spectrum.  

A crossover, either passive or active, is designed to separate out the signals being sent to the loudspeaker drivers.  High frequencies for the tweeter and low frequencies for the bass driver.  If you have a 3-way system, then the crossover has the added function of allowing only an intended band of signals for the mid-range driver.

But as you know an active, electronic crossover/DSP also has an equalizer function in the amplitude domain integral to its design "raison d’être." Apart from dividing the signal sent from the preamp and passing it on to the power amps with chosen filter slopes, types, cut-off frequencies, delay etc., each driver band also has its overall gain setting and a number of PEQ’s (i.e.: Parametric EQ):

In my own Xilica DSP there are 8 such PEQ’s for each driver band (3 of them per channel for a 3-way system), and that means the opportunity to choose up to 8 specific frequencies (in single Hz increments) within each of these bands that can be positively or negatively gained in 0.25dB steps from a chosen Q-factor (i.e.: the sloping width around each of these frequencies). That means 3x8 PEQ’s + the overall gain structure for the 3 individual driver bands.  

In fact there’s also an "equalizer" function in the time domain in the shape of delay settings; IIR filters that applies a specific delay to the whole of each frequency band, and linear phase FIR filters that have some 65,000 delay points over the frequency spectrum (obviously not done manually).

Which is to say: functionally an active crossover is also an equalizer, whereas an equalizer is only that. What’s more and not least: with an active crossover the equalization is done at the heart of the crossover itself, and not as an additional hardware component. What an active crossover lacks in the number of equalizer bands it can make up for getting the overall gain structure of each driver band right from the outset, which is the easier part. The rest with PEQ’s is fine tuning, but also the hairier aspect that can really lift the overall performance.