Active Crossover, Digital Crossovers, and Software Digital Crossovers


and Frequency Response Control:

The active crossover is superior in nearly every way to passive crossovers with the exception of one huge and glaring problem…

simple passive crossover network

…implementing them at the retail level.

What do I mean? The issue is changing over existing speaker systems, amplifiers, home theater processors, receivers, etc. so that active circuits can be used…

And its not likely to happen anytime soon, so this is either a very high end product, or a DIY approach to home audio.

Passive crossover technology is what most consumers are accustomed to. In short ~

Passive crossovers are safe and comfortable!

Active crossovers are different because you need an amplifier for each type of speaker driver. A DAC for each channel (6 channels for a 3 way stereo speakers set).

This causes most consumers to think that they cannot afford to step up to the plate and go all active. They would be wrong. Active crossovers and digital crossovers are so much better that you can use a lower powered lesser quality amp to achieve better results than you could with an all passive system.

So yes; they look more complex as a system, because they are. But when you really consider how they work and why they can be far superior, going all active just makes high fidelity sense.

Making changes to the frequency response of your drivers is easy with a digital crossover. It’s even easier with a digital software crossover.

Time and Phase Coherence:

Time and phase coherence can be achieved by using a 1st order crossover and knowing what you are doing. Building speakers that use 1st order crossover will place high demands on your speaker drivers so you must know what you are doing here. I would not attempt it.

Time and phase coherence can easily be achieved with the use of a digital crossover or digital software crossover by simply placing delays on the driver units. Measurement may be necessary to fine tune your delays but this is pretty easy to do.

This just one of the major advantages of the digital crossover and it is not a small task. Achieving time and phase coherence with the use of passive crossovers is very difficult and almost none of the speaker builders bother to achieve it. (it is that hard) But again; by going to digital, this is very easy.

Speaker Driver Spacing:

In order for your drivers to work well with one another they will need to be placed close to minimize “driver localization”. This is the ability to hear the signal that each specific driver type is playing.

If you can hear your tweeter coming from its exact location on the speaker, something is not right.

Speakers should be able to fool you into believing that sounds are coming from all over the room. The better the speaker were built and designed usually the better they are at pulling this disappearing act off.

Being able to hear exactly where your speaker drivers are located is not a good thing and is not an excellent speaker design characteristic. Images should be placed in the places where the recording engineers placed them. This is called the sound-stage.

Acoustic Lobeing:

Lobeing occurs when speaker drivers are not placed close enough together and, there is not enough distance between the speaker and the listener. There are ways to calculate exactly how far a particular driver should be placed apart and what frequencies are going to be canceled out.

Lobeing causes cancellation due to the acoustic output causing a negative phase at specific frequencies.

It basically messes up the frequency response of an otherwise well-made speaker. If your drivers cannot be placed any further; try sitting farther from the speakers.

The more distance you can place between your ear and the speakers, the better chance the sound will have to sum (flatten out) properly -prior to reaching your ears.

This trick can be used on line source speakers and point source speakers with multiple drivers. Increasing distance will decrease lobeing.

Summary – Active crossover:

These are the most obvious things you will need to address when designing and building a speaker system.

If you find a reasonable way to deal with all of these design parameters you are likely to build a very good speaker system.

I have found that the performance of a speaker built in this way can compete with retail speakers at close to 10 times the price. You can even find good computer speaker systems such as our surround sound speakers (Mini Cube Speakers).

Your experience may be a bit different; maybe better, maybe worse. But that is the beauty of DIY; you can always try harder next time.

Good luck with your build!
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