Active vrs passive

[Pano]

I wonder how many dome tweeters stay below those THD levels when you feed them the 100-200W necessary to reach those SPL levels.

Most of them, I'm sure. After a brief flash and puff of smoke, of course!

 

[5th element]

If they are within xmax and the average power delivered is low enough so that they don't fry, it'll be reasonably low. Dome tweeters do fairly well with high SPLs as do most hifi drivers, the trouble comes when they are expected to keep it up for extended periods of time, then things melt.

There are some examples here

Zaph|Audio - Design Contest Results

 

[mondogenerator]

Flavio and deward. You guys know the digital domain. Passives arent obsolete '78 tech, and you both know that too. It is merely the origin of all filter topology. How do you filter the input to ADC? Passively. Many passives used in DSP too, prior to digi filters.

 

[AndrewT]

.............Very steep filters, ..................fail to convince me sonically. ........

what do you mean by very steep?
3, 4 & 5pole or 8pole to 18pole?

 

[AndrewT]

Why?
a 110dB compression driver with a 10mW signal is comparable in output level to a 90dB cone driver with 1W. Both will give ~90dB SPL @ 1m

high loudness studio monitors = deaf engineer = poor mix.

Please show me something better than results in High Frequency Compression Driver Evaluation thread:




These are post 1980 drivers. 4%-10% 2nd harmonic is not natural or reasonable for high fidelity, and whatever a "pure amplifier" is, it's not going to fix this.
What is mechanism for "pure" amplifiers elimination of driver distortion?

Regards,

Andrew

I asked and you gave this?

02dsHi+6 108.4 dB, 4% 2ndHD

Does that answer?
I don't even know what that is telling me.

 

[wrager]

Today's my day to go active with my JBL cinema speakers (4622). I bought three Crown DSi 1000's. These have the preset crossovers for my speakers. Can't wait to see what improvements I get vs. passive.

 

[AndrewT]

I can guarantee at least one result:

It will sound very different from using one amplifier with all three drivers attached in parallel across the amps output terminals.

 

[Barleywater]

I asked and you gave this?
Does that answer?
I don't even know what that is telling me.

It is line from results post showing 2nd harmonic of 4% when output is 108dB for a particular compression driver. It is an excellent predictor that IMD products from driver when fed two tone stimulus will be audible as well the 2nd harmonic. Loud yes, high fidelity, not in my opinion.

Regards,

Andrew

 

[AndrewT]

02dsHi+6

is a compression driver description.
and is there a comparable result for a cone driver to show us?

 

[Pano]

what do you mean by very steep?

Mostly I mean near brick wall, the kind that are only practical in DSP. But generally most above 6th order electrical.

 

[Pano]

Loud yes, high fidelity, not in my opinion.

Based on specs, or on listening? We have a whole thread about that, but it really never concludes anything.

 

[dewardh]

Passives arent obsolete '78 tech,

Tell that to Sy . . .

It's not 1978 anymore.

Some of us were already using active in 1978 (Dahlquist DP-LP1 in my case, and not my first) . . . we already knew the advantages "back then". It's certainly true that "in these days of CAD" it is easier to design a "good" passive crossover . . . one that may well be "good enough" for the particular application. It is also easier to design a far better active one. The "technology" has advanced, both in design and implementation. The reasons for and advantages of active remain . . .

 

[SY]

I qualified the "easy" part several times. The question is "can you get the same results?" and I've seen no-one come up with a reason that you can't.

 

[john k...]

Being that I am a user of both and a proponent of neither let me pose a hypothetical. The task is to design a midrange band pass filter either active of passive. One person takes the passive approach, another the active. Both achieve the same, identical bandpass response. So, which is superior and why?

And I am not considering insertion loss as a factor. It's not a serious issue in a home system, which is what I am considering.

 

[Pano]

John, I sure don't have the answer, unless practical matters or costs are considered.

 

[SY]

Yes, you need to specify the criteria by which merit is judged as well as specifics for the implementation.

Like you, I use both, depending on what's the straightest route to a particular target.

 

[Cal Weldon]

So, which is superior and why?

The guy using active. He saved himself a whole bunch of hours for other things, like listening.

Yes, you need to specify the criteria by which merit is judged as well as specifics for the implementation.

See above.

Like you, I use both, depending on what's the straightest route to a particular target.

Active.

 

[dewardh]

The task is to design a midrange band pass filter either active of passive. One person takes the passive approach, another the active. Both achieve the same, identical bandpass response. So, which is superior and why?

It depends, of course, on context.

Are there going to be correponding high-pass and low-pass filters to go with it? What kind of slopes are you looking at? Is it a well behaved driver (at least within the passband)? Will the driver behave better with "pure" voltage source or "pure" current source? Do you need time alignment with other drivers? Are there other potential "phase" issues?

If bandpass is your only goal and there is a lot of out-of-band signal then it will reduce amplifier load (and potentially increase amplifier linearity and reduce amplifier cost) to kill the out of band signal before the amp (this does not, of course, necessarily require an "active" filter . . . you could place a "'passive" line level filter before the amp).

And all the speculation is based on the presumption, not necessarily true as a practical matter in the real world, that you can "achieve the same, identical bandpass response". As you well know it is easy to create filters using something like the UE that cannot be duplicated with any practically buildable passive design . . .

 

[puppet]

I think if you took john k's task literally, with responses of each method EQ'ed close, an A/B would reveal no audible differences. Cost and time would be the prevailing factor.

 

[AndrewT]

...................... (this does not, of course, necessarily require an "active" filter . . . you could place a "'passive" line level filter before the amp). . . .

a passive line level filter before an amplifier feeding a bass unit can either be combined with the passive filtering for the bass driver to give the correct acoustic output or set to one or two octaves higher such that it can be disregarded for it's effect on acoustic output.

Consider a 3kHz crossed passive 2way.
The line level low pass passive can be 3kHz or 6 to 12kHz.
How much signal can a 6dB/octave remove from the signal being handled by the bass/mid amplifier?

When considering a high pass passive for the treble amplifier then some advantage can probably be had, but two octaves below 3kHz means F-3dB @ ~750Hz and F-9dB (~1/3rd of signal level) @ ~370Hz. Not a lot of attenuation of the unwanted signal.