DIY speaker builders: Why not go active? (long) (1 Viewer)

[Saurav]

OK, looks like we're all in agreement here, more or less

 

[ThomasW]

Certainly we're in agreement that custom designed active XO's do a very good job.

Generic active XO's have their place too. But it's not as a drop-in replacement for any passive unit on the market.

And passives when done correctly, using quality components, can and do sound extremely good. Anyone having the opportunity to audition a pair of Avalon Acoustics Sentinels will attest to that. Note that the 'black box' at the bottom of the speaker contains the XO for the speaker. The built-in subwoofer has an active XO, the rest of the design has a passive XO.

Alex

I ran across this link today you might find it interesting
http://pcazeles.perso.cegetel.net/acxo.htm

 

[Wayne A. Pflughaupt]

Wow, when I left town for the weekend this thread appeared to be all but dead in the water. Certainly a surprise to come home and see all this activity! Michael Price, nice to see you weigh in with fresh input about your on-going experiment.

The comments have all been outstanding and educational, save Thomas' snide and uncalled-for invective (post #3). It should have been obvious to anyone reading my opening post that I'm no subject-matter expert in this; anyone who got the impression that I was pretending to be wasn't paying attention.

I wouldn't be foolish enough to claim that there are no first-class passive designs out there. However, I think it's safe to say that those designs are only "first class" with the speaker system/drivers they've been designed for. You can't take them anywhere else and expect the same results, right?

That's why I'm intrigued with Michael P's experiments with an active design, as well as Ethan's and Michael K's experiences. Michael P was reporting improvements early on, long before he had the design optimized. Michael K reports that despite some drawbacks, his active set-up is "far superior" to his passive. And Ethan reports improvements with a basic off-the-shelf crossover. Sure, the latter two may not be an "optimal" approach, but for someone who isn't interested in spending his life endlessly tweaking and/or doesn't have the necessary training or experience in component-level electronics to embark on a custom active design, the overall discussion here tells me the odds of realizing some audible improvements should I try to hot-rod my old Genesis speakers are pretty good, even with an off-the shelf crossover.

If it doesn't work - hey, it's easy enough put it all back together the way it was. At the very least, it would be an educational experiment.

All of that aside, it appears I failed to get the point across in my original post, but it was directed more to DIY speaker builders who prefer passive crossovers to active. I'd still be interested in seeing some of them weigh in and tell us why they prefer to go that route.

Any takers?

Regards,
Wayne A. Pflughaupt

 

[Michael R Price]

My problem with passive crossovers, especially for the purposes of speaker development, is cost. Now that I have my active crossover board up and running I can change the circuit (with cheap small signal components) easily to tweak the filters. I can also perform electrical response measurements on those filters, and acoustic measurements on the speakers connected to them, and listen to some music in a matter of minutes. That would be somewhat tougher with the passive crossovers.

By the way I think I'm about done tweaking the current 2nd/4th order iteration of the Kit281 active crossover. It might be a couple weeks before I try the steeper filters because this sounds pretty good now and I'm about to go on vacation with my parents. The problem I had was that the breakup on the woofers was a larger problem than the Adire response graphs would indicate (the narrow band peak is 10db or more). I ended up sacrificing output in the 1.4KHz range (worsening off axis) to bring the breakup down and get better "integration" at the crossover frequency. Now it sounds less fatiguing and has a deeper soundstage but there's a slight audible deficiency somewhere in the midrange (doesn't bother me). Hopefully the steeper filters and lower crossover point will correct that.

One of my friends was over yesterday, he'd heard my Kit281s before, but this time he said it was the cleanest sound he'd ever heard. We drove back to his house to get his electric guitar and amp, and then he played along with some loud rock music.

 

[Pete Mazz]

Nice work Mike! I opted for a Marchand XM-9 xover because I am electronically challenged . I use it on my B&G RD50/Dayton 7" aluminum line arrays with a xover at 500Hz. I have also had to insert 2 passive notch filters to tame a couple resonances but would love to do it actively as well. I could probably mount them in the Marchand enclosure but as I said......I don't know the first thing about designing one.

Pete

 

[Michael R Price]

Pete, the active notch filters are a little less intuitive but still pretty simple. You use a series resistor followed by LCR to ground, with the L and R replaced by this circuit:


By the way here is the woofer response of my current active Kit281s, 1/24 octave smoothed. I am now using a 2nd order Q=0.60 filter at 1170 Hz!


Edit: If anyone's still looking please disregard my above graph. I accidentally changed the wrong resistors in my crossover and the frequency used in that measurement was actually more like 750 Hz. That explains the thin midrange. It's hard to tell there is anything missing now, with the 1170 Hz filter.