Will active crossovers make cheap drivers sound well?

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Joined 2007
Doesn't the copper to handle high current cost a lot more than a few op-amps??

Winding your own must be cheaper than purchasing of cours but how much wire do you need to buy to get it at the best price??

Price of copper is thru the roof at the moment and here it's sold by the kilogram, some high current inductors at high values mass aound 5 kilos each
 
My current 3-way active OB project has cost ~$350 USD for 2 circa 1960 6v6 Magnavox console pulls (modified) and a 200 wpc QSC PA amp to drive ~3 ohm stacked W-dipole bass modules (mini-refrigerators). The crossover, 4 "active filter four" boards from a DIYaudio group buy, along with capacitors, resistors, OPamps and surplus regulated psu, comes in at ~$170 USD.

...not "cheap", but infinitely more flexible than anything passive.

Another advantage can be seen when one models a 300Hz passive notch filter and sees the reactance that it presents the poor amplifier asked to drive it
 
If you already have tons of spare amplifiers (like I do, I keep building them for some reason :)), and you're building a 3-way, then active is cheaper. But for 2-ways, passive is a lot neater and more elegant, you can take them anywhere, without all the crossover modules and amps.

Active can make cheap woofers sound better by using the Linkwitz Transform. It really does wonders.
 
cotdt said:
If you already have tons of spare amplifiers (like I do, I keep building them for some reason :)), and you're building a 3-way, then active is cheaper. But for 2-ways, passive is a lot neater and more elegant, you can take them anywhere, without all the crossover modules and amps.


The Linkwitz Plutos might be fifteen pounds each for everything with the only portability issue being that you need both a sound signal and power at their location. It's not a big deal.

With silicon being inexpensive, companies are even building cheap plastic portable stereos with active cross-overs.
 
gedlee said:



You're not comparing apples to apples. Wind your own inductors and caps and its still cheaper with passive.

I remember articles (crystal radio's) about rolling your own caps, but really doesn't make sense to do this. Not sure you can save that much winding your own copper either, store bought just looks so much better anyway.
 
infinia said:


I remember articles (crystal radio's) about rolling your own caps, but really doesn't make sense to do this. Not sure you can save that much winding your own copper either, store bought just looks so much better anyway.

you've obviously never rolled your own caps before. by rolling your own, you can make caps that are not commercially available like using liquid teflon, or make parallel plate capacitors.

also, mega savings rolling your own caps.
 
I guess it depends on the price you pay for wire, buy in bulk save more. But in retail smaller spools, it's a draw/per pound. You all gettin any good deals on Cu up in Canada we don't know about?

yikes, who elso makes their own caps? I guess I'm falling behind on technology.:D I rather spend time cuttin MDF and painting.
 
gedlee said:



You're not comparing apples to apples. Wind your own inductors and caps and its still cheaper with passive.

It really depends. If crossover frequency is 1500Hz, than probably passive filter is cheaper. If you cross at 150Hz than i doubt it. And I don't know how to wind my own cap.

And I was not talking only about crossover. Also you need less amplifier power to handle the same peak SPL.
And this is simple to understand: let say you need at the same time 20V for LF driver and 20V for HF. It is 40V.
If you have 2 amplifiers, you need 20V for each one. But an amplifier with 40V has 4x more power than 20V one.
Transformers, high capacity C, heat sink are more expensive than filter.
 
Active XO and DC Offsets

I didn't see much chat about the effects of amplifier DC offset in an active XO speaker system. I'm wrestling with my hardware to get my offsets down below 5mV so as not to adversly affect the low excursion dome tweeters and midranges. I hate the idea of a big cap to block DC. Folks say 25mV is fine, that may be so for a long throw woofer..but if you wish to stay in the drivers magnetic gap sweet spot, 2mv or less DC offset is what I would want.
 
I guess your options are big cap, tweaking to low offset or using a DC servo amp.

I use a pair of 12 uf polyprop caps. That puts the cap induced rolloff well below the XO frequency and doesn't have a noticable impact on the sound. The protect my dome tweeters from improper turn on sequencing. Last night they didn't protect a JP3 ribbon from a computer glitch when testing though. :(
 
DC offset alternative

I like the DC servo solution. For those unfamiliar with it:

The DC servo is a very low pass filter (from 0.1 to 10 Hz depending on your configuration and preferences) that is driven by the amplifier output. Its filtered signal is feed into the input to cancel out the DC offset.

This avoids the caps in the signal path and is inherently self adjusting over the life of the amp.
 
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