Bi-amping: Why active crossover?

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XScorpius

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Joined 2013
#1
Greetings.

I have an ongoing project where goal is to Bi-amp Yamaha NS-1000m speakers with triode valve amp (mid/high) and SS-amp (woofer). Original idea was to drive full audio signal to SS-amp (so called "fools" bi-amp) and let the crossover of the speaker do the filtering. But with valveamp, I would add proper capacitor value to line in so imput signal to valve amp is softly filtered at Fs=500 Hz (Fs of woofer in NS-1000m speakers). This way 8watt A-class valve amp would not waste its precious watts into bass section. The speakers crossover will be passive in this setup, only wiring for biamping is added.

But I've been adviced by some people that I really need to go active crossover if I seriosly want to Bi-amp. They did not clarify, why.

Could someone clarify me here? Why I need active crossover?
 
#3
i can't explain why you fail to see why an active x-over is worth while and if the benefits are not obvious to you than just go ahead with what you where planning.
and if active is not appealing to you look up (google) PLLXO (passive line level x-over)

and make sure the current speaker crossover is modified appropriately so you don't link the outputs of your amps through it(i've seen people do this in an attempt to biamp)
 
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#4
I thought it was for the Joules gained by omitting some components, such the plate of a capacitor or the winding of a bobbin.
BTW The capacitor before the midrange ( HP function) is probably followed by an inductor for 2nd order filter. The problem arises when you remove the HP filter part of the bandpass filter that delivers the signal to the midrange unit, because you have to "mimic" the same transfer function -Indeed it's easy ...🙂
 
#6
A lot of people will tell you that Active is the magic bullet. It isn't. It's just easier to achieve good results. There will be much protesting and claims, but bottom line, it's just easier.

As for your valve amp expending watts into the bass, it won't. That's how crossovers work. If the valve amp is connected to the high pass section, then it will see very high impedance in the bass. High impedance means very little (or no) power will be used for the bass. Your idea of a cap before the amp is not a bad one, you just want to be sure it's a large enough value not to modify the crossover points.

Start with your bi-amp passive. Hear how you like it. Then if you are like the rest of us audiophools, you will get an itch to try something new. Go active at that point and play around. But start with what you have, it's the first step. Have fun!
 
#7
krivium said:
Why is clearly explained here:
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1

BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 2
Click to expand...

Links you provided were dynamite and was exactly i wanted. I have now learned so much, thanks for links!

So, indeed..Active X-overing is the thing, and I'll definitely do this.

Ofcourse, now ~10 question arised when I read those articles. But I'll ask these question on later occasion when I have gained more info for my project.

Cheers!

Pano said:
A lot of people will tell you that Active is the magic bullet. It isn't. It's just easier to achieve good results. There will be much protesting and claims, but bottom line, it's just easier.

As for your valve amp expending watts into the bass, it won't. That's how crossovers work. If the valve amp is connected to the high pass section, then it will see very high impedance in the bass. High impedance means very little (or no) power will be used for the bass. Your idea of a cap before the amp is not a bad one, you just want to be sure it's a large enough value not to modify the crossover points.

Start with your bi-amp passive. Hear how you like it. Then if you are like the rest of us audiophools, you will get an itch to try something new. Go active at that point and play around. But start with what you have, it's the first step. Have fun!
Click to expand...

Thanks. This will definitely be my first test! There might be bumps in the way..Because my DIY valve amp has no feedback whatsover (none, nada) and I heard that biamping this with SS-amp w/feedback will probably be a tricky thing.

Can this be corrected with active xover tweaks?
 
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#10
For design work Pano is correct, it's just easier. Wanting more than a active xover would provide have bought into the dsp based solutions from minidsp.

Over the decades have gone from passive, passive biamp, active triamp, and now active dsp.

My latest setup was designed for an all passive xover, but once I saw what the cost of my prefered components were, decided against it. The flexibility a minidsp brings is a lot.
If your not looking for the ultimate but rather still excellent then you should look at their products.

For design purposes a lowly 2x4 is something my tool chest will never be without. Even if the design is for a passive only, it's perfect for defining those costly passive components with little to no changes required.
 
#11
I bi-amped my NS1000M with a 12dB passive crossover built with film caps and toroidal inductors of about 3.6H in value.

You can replace the grid-leak resistor in your amp with the inductor, and change the input cap to suit.

Find some inductors and scale the caps to suit.
 
#13
MiniDSP and active bi amping changed my life. Really - it's awesome to be able to throw together almost any woofer, tweeter and within 30 minutes or less have a XO that sounds decent. I don't have the skill to design passive XO's so this works great for me and allows me to Diy more than full range speakers.

It seems expensive at first but it's not - you have an infinite supply of custom reusable infinitely adjustable XO's.

$80 for miniDSP 2x4
$10 for 2 way advanced plugin
$20 for shipping from Hong Kong.

Get any two sets of amps you like and if you have one already then that's it. Otherwise I recommend a pair of $20 TPA3116D2 boards and you are good to go.
 
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