Active Crossovers

[Dentdog]

Wouldn't it be nice to have speakers easily converted for use with active crossovers? I'm in the market for a speaker and have settled on two possibilities. Salk 12s and Revel Salon 2s. Speakers built with separate binding posts for each driver and crossover points and slopes defined would be helpful, no?

 

[AcuDefTechGuy]

You talking about converting them to active speakers? I wouldn't. They sound great as is.

 

[Dentdog]

Hey I'm no engineer and its not a matter of whether or not these speakers are great as I'm sure they are amongst the finest ever produced. It is actually more about allowing separate amps to function more efficiently within a limited frequency range. Allowing the signal to be split before it is amplified reduces the effects on the signal inherent in a heated, highly amplified environment.

I've read much of Rob Elliott's from Elliott Sound Products' theories and he has kindled my interest in this. I also discussed this with Walter Leiderman from Emerald Physics he also questioned why this isn't done more often.

I'm building a system after 25 years away from this hobby. Just trying to do it the best way.

Thanks,and enjoy the music.

 

[fuzz092888]

With todays advancements with amplifiers I seriously doubt the benefits of an active crossover have much, if anything, to do with the amplifiers in a home environment. YMMV.

 

[markw]

With todays advancements with amplifiers I seriously doubt the benefits of an active crossover have much, if anything, to do with the amplifiers in a home environment. YMMV.

Totally agree. This dragon was slayed many years ago.

If anything, it's more to be able to more easily and exactly predict and control the crossover and slope.

 

[AcuDefTechGuy]

You can get a $500 class-D Crown XLS2500 amp that outputs 770 watts x 2Ch into 4 ohms.

Or get a high efficiency speaker w/ a 100+dB/w/m.

But I think that active speakers are overrated.

 

[Dennis Murphy]

You can get a $500 class-D Crown XLS2500 amp that outputs 770 watts x 2Ch into 4 ohms.

Or get a high efficiency speaker w/ a 100+dB/w/m.

But I think that active speakers are overrated.

A big +1 on that. I've been designing passive crossovers for over 10 years now, and every year I expected active technology and amplification to render me even more of a fossil than I already am. And I don't discount the basic theory that scores points for the active approach. Once the cost comes down (way down, to the point where the active circuits are cheaper than the passive), I suspect that active crossovers will come to dominate the market. But as to whether active crossovers actually sound significantly better--I just haven't been able to confirm it when I tried active and passive approaches to the same speaker. In practical real-world conditions, the main advantage of the active approach is the ability to adjust the woofer level to different room environments and tastes. But now you can to that on passive designs with the right equipment, and more precisely than ramping the entire bass level up or down with different amplifier drive levels. Some people would like to use different types of amplifiers on the highs and lows--brawny solid state units for the woofer, and tube units for the highs. But you can do that on the Salk speakers through biamping--the woofer crossover is completely separate form the mid-tweeter crossover when you remove the shorting straps between the two pairs of terminals.

 

[avengineer]

Hey I'm no engineer and its not a matter of whether or not these speakers are great as I'm sure they are amongst the finest ever produced. It is actually more about allowing separate amps to function more efficiently within a limited frequency range. Allowing the signal to be split before it is amplified reduces the effects on the signal inherent in a heated, highly amplified environment.

I believe the main advantage to active crossovers would be in the optimization of a crossover network to a physical speaker design, wherein certain issues as precision time alignment, in particular with systems that use several different horns with offset drivers, becomes complex enough that there's an advantage in doing it active. For example, an all-pass network is a pain in the passive world, pretty easy to do active. But I wouldn't presume to snip out a speaker's passive crossover and think I could do better active. There's a lot of tuning and voicing involved there that I'd be bypassing, basically re-designing the speaker. Interesting project, but probably of little benefit if we assume the manufacturer already did his best.

The issues of an amp being better able to handle signals post-crossover doesn't make any sense, especially with todays electronics.

 

[jinjuku]

With todays advancements with amplifiers I seriously doubt the benefits of an active crossover have much, if anything, to do with the amplifiers in a home environment. YMMV.

Totally agree. This dragon was slayed many years ago.

If anything, it's more to be able to more easily and exactly predict and control the crossover and slope.

Agreed also. If you are investing in $20K of speaker another $2K in 4-6 channels of amplification with DSP isn't doing to be a deal breaker. First thing to keep in mind (and I get a kick out of it) is people discussing damping factor all the while running through a passive x-over.

You get better power handling (thermals), no back EMF, better efficiency (less amp required). Now the instances were actives really shine is when you have a design that is dipping precipitously low impedance wise and/or wide phase angles are going to be present when passively driven.

If you can do it go active by all means. If not passives still do the job. I wouldn't take a commercial speaker and trash the passives just to put actives in.

 

[Ricardojoa]

If someone is going to start from scratch, he will eventually need to get amp, pre, but with Dsp to start with their will be more control? no?

 

[fmw]

Go back and reread what AVengineer said. You need to understand that an active crossover replaces the passive one. That means you need to open the cabinet and remove or disconnect the existing crossover. The main purpose of an active crossover is to isolate the drivers from one another and allow control over the crossover frequency. You simply don't need to do that to a well designed and well made speaker system.

 

[AcuDefTechGuy]

If a speaker sounds fantastic, why change anything? Just enjoy the sound.

I guess some people just fancy active speakers just for the sake of having active speakers?

I have to admit that when I bought my Orion, I did fancy the fact that it was an active quad-amp speaker.

But after the speaker-honeymoon period, I really didn't care.

 

[jinjuku]

If someone is going to start from scratch, he will eventually need to get amp, pre, but with Dsp to start with their will be more control? no?

You need DSP and Amp channel per transducer/transducer array that you are going to drive.

 

[Ricardojoa]

Go back and reread what AVengineer said. You need to understand that an active crossover replaces the passive one. That means you need to open the cabinet and remove or disconnect the existing crossover. The main purpose of an active crossover is to isolate the drivers from one another and allow control over the crossover frequency. You simply don't need to do that to a well designed and well made speaker system.

I understand that, but my post was, if some is going to start from scrtach, it means building one with no passive xover and straigth to a dsp system like deqx, and new amps. This would mean a whole new system basically.

 

[lsiberian]

Why not go all the way and just make your own speakers? Sell your speakers get some parts and have fun.

 

[Ricardojoa]

If a speaker sounds fantastic, why change anything? Just enjoy the sound.

I guess some people just fancy active speakers just for the sake of having active speakers?

I have to admit that when I bought my Orion, I did fancy the fact that it was an active quad-amp speaker.

But after the speaker-honeymoon period, I really didn't care.

I do agree with that, if it dounds good enjoy it, but seems like the OP want to go a litle extreme. Maybe tighter, flatter measurements? Who knows. The only thing o guess would be the additionsl cost of extra amps and a realiable dsp that would be quiet costly.

 

[lsiberian]

I do agree with that, if it dounds good enjoy it, but seems like the OP want to go a litle extreme. Maybe tighter, flatter measurements? Who knows. The only thing o guess would be the additionsl cost of extra amps and a realiable dsp that would be quiet costly.

For a pair of 2-ways it would only cost 200 for the amps, DSP and power supply. For a pair of 3-ways The cost doubles.

 

[Ricardojoa]

what would it, for so cheap?

 

[avengineer]

I understand that, but my post was, if some is going to start from scrtach, it means building one with no passive xover and straigth to a dsp system like deqx, and new amps. This would mean a whole new system basically.

If you were building a xover from scratch and wanted to experiment, and have your results listenable quickly, then doing it with DSP hardware and separate amps would be the answer, but building for manufacturing wouldn't work that way. It's great for experiments, but for mass-production, if you can whip out a crossover with a hand-full of passive parts inside the box, that's cheaper and more controlled than the active way. The DSP device you need to experiment this way would be fairly expensive, though, or would be a stack of cheaper units. And, some of the control software for cheaper DSP devices isn't conducive to optimizing a crossover, more of a sound system EQ tool. Don't forget, if you're starting from scratch with this, you need good analysis tools too.

 

[avengineer]

I do agree with that, if it dounds good enjoy it, but seems like the OP want to go a litle extreme. Maybe tighter, flatter measurements? Who knows. The only thing o guess would be the additionsl cost of extra amps and a realiable dsp that would be quiet costly.

+1 on "Who knows?" No guarantee on thighter flatter measurements.