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-   -   Active vrs passive (http://www.diyaudio.com/forums/multi-way/221643-active-vrs-passive.html)

Boscoe 16th October 2012 07:09 AM

Active vrs passive
 
2 threads on the same subject started by the same member merged :cop:

High resolution and passive crossover don't go together.

Boscoe 16th October 2012 07:17 AM

Passive crossovers...
 
I see few projects here that feature very expensive drivers and a lot of time designing and making boxes. Then they use passive crossovers which are convenient but are plagued by wrecking the damping factor of the amplifier thus causing distortion especially at low frequencies that causes that sloppy bass everyone is trying to get rid of here. Some confuse this distortion with loud bass. Overall distortion can be measured in the order of 0.1% and up with passives although a nice couple of op amps are in the 0.0001 region with unity gain could that be a thousand times better? Perhaps theoretically but you have to agree that they do have a lot lower distortion!

planet10 16th October 2012 07:28 AM

Why?

Execution is very important. All too many active systems are only good. A very well executed passive system can outperform an only good active system.

Your statement is far to general to be anywhere near true.

dave

Boscoe 16th October 2012 07:33 AM

Why would you pit a good active system against a very good passive system. Agreed active systems still need care but passive crossovers are ultimately flawed so will never reach the performance levels of well implemented actives no matter how good it is. Please tell me Sir, in what way do passive crossovers have an advantage of active?

wolf_teeth 16th October 2012 07:38 AM

Quote:

Originally Posted by Boscoe (Post 3203343)
but passive crossovers are ultimately flawed so will never reach the performance levels of well implemented actives...

This is blatantly false.
Ultimately flawed!? You haven't heard a good pair apparently.

Later,
Wolf

planet10 16th October 2012 08:51 AM

Quote:

Originally Posted by Boscoe (Post 3203343)
Agreed active systems still need care but passive crossovers are ultimately flawed so will never reach the performance levels of well implemented actives no matter how good it is. Please tell me Sir, in what way do passive crossovers have an advantage of active?

Take a well selected system with a simple series XO. It has a degree of self-compensation because of the interaction of all drivers and XO together that no active system can accomplish.

Active systems have some serious advantages, but also downsides. The advantages are not enuff to give them blanket superiority.

Each system has to be considered on its merits.

I admit that most of my systems are active (almost always with no intervening electronics to add their own layer of grunge), but i have built at least one passive system that really opened my eyes to the possibilities.

dave

Dissi 16th October 2012 11:25 AM

Yes, an op amp is thousand times better, but an active crossover is only few percent better than a passive.

tinitus 16th October 2012 11:44 AM

Quote:

Originally Posted by Dissi (Post 3203509)
Yes, an op amp is thousand times better......

why op amp ?

but really, messing with multiple amps, and possibly even different ones, its not just a simple matter like plugging in a few cables

Dissi 16th October 2012 12:31 PM

Example of a woofer at 100 Hz:

Active crossover: 1 % distortion
Passive crossover: 1.03 % distortion

The difference is negligible. An active solution has certainly not 0.001 % distortion.

system7 16th October 2012 02:16 PM

2 Attachment(s)
Quote:

Originally Posted by Boscoe (Post 3203323)
I see few projects here that feature very expensive drivers and a lot of time designing and making boxes. Then they use passive crossovers which are convenient but are plagued by wrecking the damping factor of the amplifier thus causing distortion especially at low frequencies that causes that sloppy bass everyone is trying to get rid of here. Some confuse this distortion with loud bass.
Overall distortion can be measured in the order of 0.1% and up with passives although a nice couple of op amps are in the 0.0001 region with unity gain could that be a thousand times better? Perhaps theoretically but you have to agree that they do have a lot lower distortion!

Yup, a couple of breathless and innaccurate ideas there, sorry. Passive crossovers have NO PROBLEMS with bass response or damping factor. The issues are at the much higher crossover point.

Why? Well look at the circuit. The bass coil really only acts at HIGHER frequencies to slope the response down. At 100Hz it is virtually transparent to the signal and has little effect on bass damping. The cabinet dimensions and room acoustics play a bigger part. You did know that you can get a tight bass with a valve amplifier which has an output impedance of several ohms didn't you?

Op amps look very nice on sine wave, but you face Class B crossover distortion and transient slew rate issues. A simple discrete transistor preamp is the preferred solution in the new Marantz 6004 amplifier, replacing an opamp in the 6003 model. So what do you know? :D

Better drivers with advanced magnets, underhung voice coils and copper pole pieces and vented magnets are all nice features which you will pay for. The skill is to balance the performance to a price point really. Personally, I find reducing midbass cone breakup and avoiding intermodulation distortion from the tweeter resonance most interesting with passive crossovers. You can really hear the difference when it's well done, and for that you need to know the drivers like the back of your hand. :cool:


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