Active crossovers, worth the effort?

[yepimonfire]

Considering a relatively inexpensive minidsp is capable of performing all of the functions necessary to implement an active crossover, and REW makes measurements easy, outside of eliminating insertion losses, does an active crossover provide a significant benefit compared to a well designed passive one?

I've considered experimenting with it using my inexpensive R-15ms, I figure I could toy with using a slightly lower xover point (still within the operating range of the horn) but a steeper slope, such as an LR4, which is impractical to do passively. In addition, any sort or phase or time alignment problems can easily be compensated for in the minidsp. While the R-15m is hardly worth the trouble, it's inexpensive enough that blowing a tweeter during the process wouldn't be a big deal to me, and it'd give me some experience with it.

Anybody have experience with active crossovers, and do they actually provide a significant enough benefit to be worth the time involved in getting right and extra amplifier costs?

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[fuzz092888]

If the purpose is to tinker and learn then could be worth it outside of paying for modeling software.

If the purpose is to make a pair of speakers that are just going to sit and be enjoyed then you'll hit diminishing returns more than likely.

For the latter purpose, a well thought out and designed speaker/passive crossover is easily just as good IMHO.

 

[Speedskater]

For new commercial loudspeakers or new DIY loudspeakers, then active DSP based crossovers are the way to go.
But for retro-fitting older speakers, there are some challenges.

 

[jazzman53]

Absolutely. EVERYTHING improves: Bass tightens up considerably, phasing errors disappear, improved coherency and clarity, higher efficiency... you would never go back to passives.

 

[yepimonfire]

Absolutely. EVERYTHING improves: Bass tightens up considerably, phasing errors disappear, improved coherency and clarity, higher efficiency... you would never go back to passives.

Phasing errors, as between drivers or something else? What if the speaker is already time aligned via the passive crossover?

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[TLS Guy]

Considering a relatively inexpensive minidsp is capable of performing all of the functions necessary to implement an active crossover, and REW makes measurements easy, outside of eliminating insertion losses, does an active crossover provide a significant benefit compared to a well designed passive one?

I've considered experimenting with it using my inexpensive R-15ms, I figure I could toy with using a slightly lower xover point (still within the operating range of the horn) but a steeper slope, such as an LR4, which is impractical to do passively. In addition, any sort or phase or time alignment problems can easily be compensated for in the minidsp. While the R-15m is hardly worth the trouble, it's inexpensive enough that blowing a tweeter during the process wouldn't be a big deal to me, and it'd give me some experience with it.

Anybody have experience with active crossovers, and do they actually provide a significant enough benefit to be worth the time involved in getting right and extra amplifier costs?

Sent from my LM-X210(G) using Tapatalk

The real advatages of active crossovers are when you require a low crossover point. Passive crossovers below 400 Hz are just bad news. They are inefficient, seriously degrade performance and stress amplifiers, and if you are not careful operate in resonance. A speaker with a low passive crossover is no longer state of the art. Even at crossover points below 2000 Hz an active design is preferable if the passive design is complex.

Active crossovers also allow for a wider selection of drivers in the design.

If on the other hand a two way can be designed to work well with a simple low component count passive crossover the I don't think there is an advantatge sonically to an active design.

The more complex the speaker the more pressing the argumant for an active design.

For high powered designs in large spaces, passive designs are no longer accceptable.

 

[KEW]

The real advatages of active crossovers are when you require a low crossover point. Passive crossovers below 400 Hz are just bad news.

Can you explain why this is ?
What is it about lower frequencies that compromises passive crossovers?

 

[TLS Guy]

Can you explain why this is ?
What is it about lower frequencies that compromises passive crossovers?

The problem is that the values of the components become huge. As low crossover points are in three way speakers, then the electonic order is also higher, to protect the fragile mid and keep a large woofer well out of break up range.

Even at 400 to 500 Hz compnent values are high. This means that to make a good passive unit very expensive inducors have to be used, and they usally are not. The compnents alone for my my passive speakers downstairs cost over $400. Only high end speakers like B & W can afford that sort of cost. Even so in their current flagship they raised the lower crossover to 500 Hz. The problems of passive crossovers at low crossover point are wasting half or more of the amp power, core stauration, hysteresis distortion, and even with high cost inductors, excessive DC resistance altering Q, and tuning freqeuncy.

Finally, you end up with horrible amp loads, and make the speaker sound different with different amps. It is these desiigns that have the worst impedance curves and phase angles. And finally if the impedance dips below the DC resistance of the woofer or woofers, then the crossover is in resonance, and you have a lousy speaker. This occurs in quite a few very high priced speakers, I suspect, and you can surmise it from the impedance/phase curves.

Making the speaker a decent drive for tha amp usually involves adding extra high cost components to improve the situation in terms of amp load.

These days an active design is the better and cheaper solution by far.

 

[highfigh]

Also, problems in the low frequencies may be across a range of 10-20Hz, but that might mean it affects a quarter to half of an octave and that can really screw up the response. Also, a steeper crossover slope adds even more phase shift and insertion loss- subwoofers don't need to intrude on the range above it and it's difficult to prevent it with a passive crossover. The cost is prohibitive, too- TLS spent more than $400 for his crossovers and mine weren't that much, but they still cost more than the four woofers and two tweeters I used. I could have bought a 2x4 MiniDSP and been halfway to another for the price of the passive components.

Another benefit of active vs passive- if you prefer a particular driver for bass and will be using a larger one for the sub(s), woofers made for sealed boxes exhibit a more gentle slope, which can be a problem and the active crossover can make these blend better than they would otherwise.

 

[Verdinut]

I have been actively bi-amping my front speakers for several years and I get excellent performance.
I am using very affordable DBX 223XS crossovers, which do what they are intended to.
Originally, I had to proceed with active crossovers when I replaced the Altec compression drivers with 5¼" mid-bass speakers and ribbon tweeters. The Altec 416-8As were 12dB more efficient than the mid-bass transducers.
More recently, I sold the Altec woofers and replaced them with Dayton RSS390HF-8 subs. I fixed the crossover at 190 Hz between midrange speakers and sub. As I was not interested in wasting amplifier power with expensive and highly resiststive series inductors and resulting reduced damping action from amplifiers, I decided to keep bi-amping with the new subs acting as woofers in each of my three front cabinets.

Another advantage of actively bi-amping is that I get an additional headroom of 7.8dB with the 3 front speakers because of the combined amplifying gains.

Here is an excellent article about bi-amping and comparison between active and passive crossovers:

http://sound.whsites.net/bi-amp.htm

 

[Johnny2Bad]

If your goal or intention is to bi- or tri-amp your loudspeakers, an active crossover (either analog or digital) is desirable if not a necessity. If you want to run with a single amplifier, the passive crossover that was developed for that particular loudspeaker is probably your best bet, unless you intend to do some extensive DIY speaker experiments (speaker building, kits, etc).

So it's not really so much a question about the crossover topology, rather it's one regarding how you intend to amplify your speakers. Determine that and the choice of crossover is the next step. Passive crossovers work quite well when properly designed, as do active ones. But improperly designed, neither will be ideal.

 

[everettT]

Considering a relatively inexpensive minidsp is capable of performing all of the functions necessary to implement an active crossover, and REW makes measurements easy, outside of eliminating insertion losses, does an active crossover provide a significant benefit compared to a well designed passive one?

I've considered experimenting with it using my inexpensive R-15ms, I figure I could toy with using a slightly lower xover point (still within the operating range of the horn) but a steeper slope, such as an LR4, which is impractical to do passively. In addition, any sort or phase or time alignment problems can easily be compensated for in the minidsp. While the R-15m is hardly worth the trouble, it's inexpensive enough that blowing a tweeter during the process wouldn't be a big deal to me, and it'd give me some experience with it.

Anybody have experience with active crossovers, and do they actually provide a significant enough benefit to be worth the time involved in getting right and extra amplifier costs?

Sent from my LM-X210(G) using Tapatalk

Either active or passive, you still need to learn to correct measurements first. Active will be easier to play with, but you still need the correct gear. Taking TS measurements will require additional software (not rew) and you will have to be able to mass load the woofer.
I'm not anywhere close to being able to design a speaker with effectiveness and I have all the gear. I've sent design thoughts to designers and gotten them ripped apart. I've read Dickerson and still am far from being ready. The math isn't simple FWIW...
Subs are one thing but ....

 

[TheWarrior]

Can you explain why this is ?
What is it about lower frequencies that compromises passive crossovers?

Assuming the use of off the shelf components, TLS was pretty comprehensive .

The Salon2's are a 4 way with purpose built drivers and are more than capable, but as TLS is pointing out, thats not an issue especially when you are likely to throw dedicated amps at them considering the entry fee.

 

[Verdinut]

Can you explain why this is ?
What is it about lower frequencies that compromises passive crossovers?

The main reason is that a passive crossover for filter frequencies below 400 Hz requires a big inductance in series with the woofer: the lower the frequency and a higher inductance is required.

High inductance requires longer wiring with resulting added resistance in series with the woofer. This results in more power needed from the amplifier and reduced damping control on the woofer with resulting decreased transients. Also, big inductors using AWG10 gauge wire are heavy and also expensive.

With the money saved on purchasing two big inductors, you would have enough to cover a good portion of the cost of a pro audio stereo analog electronic crossover.

See: http://sound.whsites.net/bi-amp.htm

Cheers,

 

[yepimonfire]

Either active or passive, you still need to learn to correct measurements first. Active will be easier to play with, but you still need the correct gear. Taking TS measurements will require additional software (not rew) and you will have to be able to mass load the woofer.
I'm not anywhere close to being able to design a speaker with effectiveness and I have all the gear. I've sent design thoughts to designers and gotten them ripped apart. I've read Dickerson and still am far from being ready. The math isn't simple FWIW...
Subs are one thing but ....

Perhaps I'm missing something, but couldn't one simply retrofit a speaker that uses a relatively simple (hi/low pass with tweeter attenuation) passive xover with an active xover and use response measurements to correctly align or eq it all?

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[highfigh]

Perhaps I'm missing something, but couldn't one simply retrofit a speaker that uses a relatively simple (hi/low pass with tweeter attenuation) passive xover with an active xover and use response measurements to correctly align or eq it all?

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The phase shift from a passive component is in the 90 degree range and the typical way of addressing LP crossover is with an active filter, so the effects don't intrude on the HP. Most subwoofers with a built-in/on amplifier have a simple 0-180° switch and that's all. Some have a variable phase control and that works much better.

It's better to use an oscilloscope and impulse signal to view the time alignment but even that must be done over a relatively wide frequency range because it's not the same for all- it's necessary to make a decision about where it sounds best, even if it's not perfect.

Also, parametric equalizers can often address the problems better than graphic because the center frequency is fixed on graphic equalizers and they don't address anything other than fixed frequency and amplitude, not variable frequency, Q, width (range of frequencies) and amplitude.

 

[TLS Guy]

Perhaps I'm missing something, but couldn't one simply retrofit a speaker that uses a relatively simple (hi/low pass with tweeter attenuation) passive xover with an active xover and use response measurements to correctly align or eq it all?

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You can, but you can and we all do Eq passive crossovers.

The big difference between the active and passive crossover I should ave mentioned, is that passive components can only cut, but active ones can boost as well. Take BSC. BSC is actually due to a lack of bass. An active crossover can boost it. A passive crossover can only cut the HF. The latter means a significant loss of speaker sensitivity compared to the active solution.

Unless you are using a fully digital filter which is rare, the time shift/phase issues of active and passive solutions are the same. It will be 90 degrees for every order of crossover.

 

[everettT]

Perhaps I'm missing something, but couldn't one simply retrofit a speaker that uses a relatively simple (hi/low pass with tweeter attenuation) passive xover with an active xover and use response measurements to correctly align or eq it all?

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Sure you may be able to achieve the goal, however:
Your going to need a 4 channel amp
A crossover/eq-dsp
An a AVR with preouts

After that investment you could have upgraded your speakers or sub. Redoing an inexpensive speaker to active makes little sense. If you had the gear already I’d say play with it for fun.

 

[Verdinut]

Perhaps I'm missing something, but couldn't one simply retrofit a speaker that uses a relatively simple (hi/low pass with tweeter attenuation) passive xover with an active xover and use response measurements to correctly align or eq it all?

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Sure, it can be done. If the two drivers already have their voice coils in the same vertical plane, it becomes rather easy with the proper equipment to adjust the frequency response.
If they're not time aligned, some electronic crossovers have a delay adjustment to arrive at an adequate time alignment.
Have you seen my post #10 which contains additional info?

 

[lsiberian]

I'm a huge active crossover fan because of the many reasons listed above, but there are a lot more cables to deal with so keep that in mind.