Active vrs passive - Page 7 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th October 2012, 11:43 AM   #61
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by Charles Darwin View Post
The 3dB are commensurate with manufacturers literature who give a power rating of 100W (woofer) and 25W (tweeter) with the passive xover in place while the woofer itself is clearly marked 50W.
sounds like a 'standard' plug and play speaker
and if its got a 'standard' crossover that could cost like 20EUR, and you have replaced it with amps and active crossover that cost more than both speakers, and not to forget the Eq, I guess you would expect some positive effect
  Reply With Quote
Old 17th October 2012, 11:46 AM   #62
diyAudio Member
 
Join Date: Nov 2009
Location: Birmingham, UK
Tannoy Little Red Monitors.
  Reply With Quote
Old 17th October 2012, 12:38 PM   #63
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by chris661 View Post
With a damping factor (at the driver terminals) that varies according to frequency, insertion loss, and all the additional nasties inductors bring along, how could a passive ever be better than an active?

I can see that they can be good enough in many cases, but better than active?

I'm still unconvinced.
Well, damping factor plays little roll in controlling the driver at any frequency other than its resonance. The flat band part of any driver's response is referred to as the mass controlled region for a reason. The effect of damping drops off at 6dB/octave to both sides of the impedance resonance peak. The effect of the suspension compliance is constant below the resonance peak and drops off at 12dB/octave above the peak. I would agree that insertion loss does rob a small amount of power but in a home environment this really isn't of significant concern unless you are trying to drive the system with an under rated power amp. As for additional nasties from inductors that pretty much a stretch. Properly chosen inductor will be extremely linear in their operating range.

I pointed out that actives can make design simpler, particularly digital. But there are other factors with actives. For example the quality and design of the active crossover itself. Active devices introduce distortion. The circuits in most active crossovers are more complex and convoluted than you will find in most preamplifiers and power amps. Digital is another source of error. Certainly in theory an digitally sampled signal can be reconstructed exactly. But in reality digital algorithms use finite math with introduces round off error which limits accuracy. There is an uncertainty kind of relationship between the analog world and the digital one. With analog it is possible to reproduce a signal exactly, but you can never know its exact value. With digital you can set the limit of accuracy so you know the exact digital value within some error. For example, with 2 digits to the right of the decimal point you can have 1.00 or 0.99 but there is no way to express an amplitude of 0.993 or 0.994 or distinguish between them. And when these numbers are multiplied together the errors can grow. A good example here is the banking industry. Money is digital. Taxes, like sales taxes are in % which can lead to fractional values below 1 cent. Everything has to be rounded off to the nearest cent. Adding, subtracting, multiplying, dividing these numerical values can introduce round off errors which have to be accounted for. In digital processing it is not necessary to track these errors. It is only necessary to make sure they remain below a certian value.

I'm not dissing active crossovers. I use active crossover between the woofer and mid/tweeter panels of all my speaker designs, and where practical I offer fully active options, both analog and digital.

What I object to in these threads is these blanket statements that A is better than B. The OP has started at least 3 threads on this topic:

1 this one,

2) What do you think of 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!

3) Passive crossovers... Some hate them and will never use anything other than active, they say due to high distortion brought on by amplifier damping. What do you think? Do you like the sound of active over passive?


These all seem to address the damping issue, which as I have discussed, is pretty much a red herring. In fact, the argument is easily turned upside down. After all, ignoring the VC inductance for simplicity, the relationship between the voltage across the VC and current is V = (If - Ib)/Re where If is the forward current and Ib is the back current (from the back emf). This is expressed at V = I/Zd where V is the applied voltage (by the amp) and Zd is the driver's impedance. Obviously, at resonance Zd is a maximum which is a result of Ib being a maximum. Since it is I that generates the force with influences the driver's motion, and since for any value of V the current flowing through the VC will be a minimum at resonance compared to frequencies to either side of resonance, it seems that the amplifier would actually have the least control over the driver at resonance due to the maximum in Ib. That is, since the musical signal supplied by the amp is a voltage as a function of time, V(t), when V(t) has frequencies near or at resonance the current across the VC will be at a minimum and therefore the amp will have the least influence over the driver's motion. The fact is that most of the arguments on damping address what happens when V(t) goes to zero and the driver must return to its rest state. The point here is that whether an active or passive system, musical instruments are basically highly resonant devices that ring on for many cycles. And in any typical musical recording V(t) does not abruptly drop to zero, but decays over time with some inherent wave form. For example, you could think of a highly damped woofer as crashing a car into a concrete wall. A woofer with lower damping would be like crashing a car into a concrete wall with 10 ft of foam padding on it. The car's velocity is V(t). Music usually ends as if you were putting your foot on the brakes to modulate V(t) so that you stop before you hit the wall. In such a case, it makes little difference what the properties of the wall are. Q of a woofer system, with in reason, has more effect on the amplitude and phase around resonance than it does on how the driver stops compared to an applied musical signal.

And the bottom line is that if there are concerns with, for example, the damping of the woofer in a multi-way speaker with passive crossover, measure it! It's not too hard to do.


Anyway, sorry to take up so much space, but blanket statements by proponents of active or passive crossovers regarding the merits of one over the other just don't fly. Like anything else in life, it's a matter of execution. To get good results you have to do it right.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 17th October 2012, 01:20 PM   #64
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Quote:
Originally Posted by john k... View Post
The OP has started at least 3 threads on this topic:
Hi,

All starting with the premise active must be better than passive. In an ideal
world it is, but not in a practical world depending on the circumstances,
the real world is cost versus performance benefits, and the downsides
of the extra complication versus the alleged benefits of the arrangement.

Amplifier damping is a complete red herring, nothing is "ruined". Simplistic
active arrangements using preset active functions are nearly always
worse overall than properly designed bespoke passive arrangements.

Its simply not the way to do active properly and is a very poor option.

If you can't design the proper electrical transfer functions to give
the correct acoustic transfer functions, active is near useless.
If you can, then active has some intriguing advantages.

BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1
and Hybrid Design and Hybrid Design

Point to some of them that can be used effectively.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 17th October 2012, 01:54 PM   #65
puppet is offline puppet  United States
diyAudio Member
 
Join Date: Dec 2011
Location: The Dells, WI
Errors in the digital processing John? ... do you mean around the xo frequency? I understand digital to lose some xo accuracy but the is mostly in the higher frequencies. IE, above where most would even consider placing a xo point to begin with, so, it of no consequence typically. Besides, any error in LP reproduction @ a xo frequency is reproduced on the HP side exactly. Summing is therefore not effected.

I'd imagine that passive components would/can introduce greater/varied error(s) @ any given xo frequency do to the component value ranges.

The audibility of some of the posted reasoning, in this thread, for favoring one side or the other is questionable to me anyway. Pick your poison. Implementing either takes a bit of skill and as stated before .. properly implemented, xo's should be transparent.
  Reply With Quote
Old 17th October 2012, 02:11 PM   #66
Helmuth is offline Helmuth  Netherlands
diyAudio Member
 
Helmuth's Avatar
 
Join Date: Oct 2008
Location: Winterswijk
Quote:
Originally Posted by wolf_teeth View Post
This is blatantly false.
Ultimately flawed!? You haven't heard a good pair apparently.

Later,
Wolf
x2. Active is often worse .
__________________
( (( KUGELWELLE )) )
recent projects :OB-mk1 /fatboy / monitor-xl / Horn-AM / dappolito / td124-mk1-rb301 / Hybrid-pse / Vfet
  Reply With Quote
Old 17th October 2012, 02:47 PM   #67
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by puppet View Post
Errors in the digital processing John? ... do you mean around the xo frequency? I understand digital to lose some xo accuracy but the is mostly in the higher frequencies. IE, above where most would even consider placing a xo point to begin with, so, it of no consequence typically. Besides, any error in LP reproduction @ a xo frequency is reproduced on the HP side exactly. Summing is therefore not effected.

I'd imagine that passive components would/can introduce greater/varied error(s) @ any given xo frequency do to the component value ranges.

The audibility of some of the posted reasoning, in this thread, for favoring one side or the other is questionable to me anyway. Pick your poison. Implementing either takes a bit of skill and as stated before .. properly implemented, xo's should be transparent.
When ever you work with numbers of finite length (limited number of significant figures) there are errors. Consider the value of Pi for example. It is defined at the ratio of circumference to diameter, C/D. To a hole bunch of decimals its value is:

3.141592653589793238462643383279502884197169399375 10

and that is not exact. But any time you multiply the diameter of a circle by Pi to find the circumference there will be an error if you use that value. If you use fewer decimal points the error will be bigger. We can place bounds on the error and limit the size based on how accurately we specify PI and we can assure that any errors do not grow by insuring that any processing algorithm is stable.

You have the same thing with digital imaging. The more pixels the closer the picture looks like the real thing. It becomes a question of how much resolution is needed before the error can not be observed under some set of conditions.

I am not saying that errors in digital audio processing are audible, just that they are there. Some people will claim 24 bit audio is superior to 16 bit. Other say they can not hear a difference. Passive, active, analog digital 16 bit, 24 bit, 44k sampling, 96k sampling. Pick a topic and someone will argue for and against.

It's audio. It's more divisive than politics. And 99% of it is BS.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 17th October 2012, 02:58 PM   #68
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Quote:
Originally Posted by Jay View Post
The question is: can your complex multi-stage amp outperform the best simple full class-A amp?
This is completely irrelevant in my view, we are discussing which is best in terms of the xover. The amplifiers are assumed to be identical or perfect in that they are effectively removed from the equation. Nevertheless amplifiers tend to have a much easier job driving just a single crossoverless driver in an active system then they would in a full passive one. This almost always improves the amplifiers performance and should therefore sound better.


Quote:
Originally Posted by planet10 View Post
For example an active XO (as opposed to a PLLXO which have different issues & advantages) will introduce higher order harmonic distortion products (which the ear/brain readily detects at very low levels) that a passive XO will not have.

As with everything it is all about execution.
Again from my point of view this isn't strictly comparing active vs passive, you're tarring active with a brush in the sense that it isn't implemented quite as well as it should be and now we compare this to the passive xover that has been implemented correctly. This isn't a fair comparison and certainly isn't really comparing the best of one with the best of another, which is what this thread should be about, not tolling the downfalls of improperly designed active filters.



Quote:
Originally Posted by cbdb View Post
Not if the active is digital, you can have linear phase, plus time delays to acousticaly align the drivers. You can change the xover freq, the filter slopes, the delays, the phase, the amplitude, etc very easily. You can use class A for the tweets and mids and D for the woofs and get (pretty much) class A sound with a punch for a lot cheaper than passive.
Clearly did not read the rest of my post. Obviously you can get phase linear digital filters, I said as much myself, but if we're comparing active to passive filters then it doesn't make sense to include what active can do that passive cannot. Granted this seems somewhat at odds with my above statement, where we should be comparing the best of active vs the best of passive, but in that instance passive will lose flat out because it is more limited.

Evening the playing field, by only comparing an active implementation to its passive counterpart should help to show any inherent flaws in either type. If you include all the extra stuff that one can do that the other cannot, then you've got a situation where people will say, yeah active is better if you need all the extra stuff that it can do, but if you don't, passive will sound better - this is clearly wrong, as it is implying actives are inherently worse and that you should only use them if absolutely necessary.

Quote:
Originally Posted by cotdt View Post
I've used analog active crossovers and liked them. However it is easier to work with passive to make changes.
Then you've not used an active xover that has been designed to allow for full flexibility of the filters that it has been built around. You can do this with variable resistors that cost pence and will give you more design freedom then having lot of boxes filled with passive crossover parts.

Quote:
Originally Posted by cotdt View Post
But the analog sections of digital crossovers sound like crap.
Then even in your own words this isn't the fault of the crossover type but in the implementation.

Quote:
Originally Posted by puppet View Post
Errors in the digital processing John? ... do you mean around the xo frequency? I understand digital to lose some xo accuracy but the is mostly in the higher frequencies. IE, above where most would even consider placing a xo point to begin with, so, it of no consequence typically.
Some digital filters lose accuracy at lower frequencies, IIR biquad based filters for example, and the higher the sampling frequency the worse this becomes. There are different filter types you can use to get around this however.

Quote:
Originally Posted by puppet View Post
The audibility of some of the posted reasoning, in this thread, for favoring one side or the other is questionable to me anyway. Pick your poison. Implementing either takes a bit of skill and as stated before .. properly implemented, xo's should be transparent.
Exactly there are a lot of subjective opinions being thrown around against active xovers. There are a lot of objective reasons too, but none of them should be used for or against either school if they are done correctly. We should not be comparing poorly or improperly implemented versions of either, but only the best.
__________________
What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz!
  Reply With Quote
Old 17th October 2012, 03:14 PM   #69
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
Quote:
Originally Posted by Charles Darwin View Post
Then please explain the much tighter and more detailed bass I got when I replaced the passive xover on my speakers with an active one. Same room, same placement, same box, same amp.
Admittedly the active xover has 24dB L-R slopes as opposed to the 12dB original but most of the audible difference is well below the unchanged 1.2k xover point.
I think you've answered your own question there.

You're comparing a second order butterworth closed box response with a 4th order (overdamped?) reflex type response. I think I could hear the difference. It's not a valid comparison.

It's interesting to see what the simple 1.2mH bass coil does with that Visaton W200S 8" driver I looked at earlier. It slopes the driver response for a standmounter to be approximately flat in the 500-5000Hz region with a 6dB rolloff. The very deepest bass response is largely unaffected. It's worth mentioning that some drivers like the polycone Vifa P13Wh are approximately flat in the right cabinet and room placement without a bass coil at all. A question of loudspeaker voice coil inductance.
Attached Images
File Type: jpg Bass_Coil_Electrical.JPG (65.7 KB, 253 views)
File Type: jpg No_Bass_Coil_Electrical.JPG (68.1 KB, 250 views)
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.
  Reply With Quote
Old 17th October 2012, 03:20 PM   #70
diyAudio Member
 
Join Date: Oct 2010
Location: Colorado Springs, CO
Quote:
Originally Posted by 5th element View Post
In my opinion getting a design right is just as hard, or easy, whether you go active or passive, that is if 'right' for you is a perfectly implemented crossover for a certain set of drivers where everything has been put together with a lot of measurements and a large chunk of CAD work.
I dont know if its just as hard. Making changes is far ieasier with the turn of a knob and pressing a few buttons. Making changes in high order crosses from sub to sats is pretty expensive and cumbersome if you dont have quite the selection of parts on your shelf. While I completely agree that a well implemented John K design will beat any crossover that I can design, a high order sub crossover is just rediculous in signal loss and cost over active.

In the end, time alignment, notch filters, and high order crossovers are just so much easier to tweak with buttons and knobs. Nothing I have made with passive comes anywhere near my active systems. I guess for me, my lack of skill gets rescued by active which for me is easier to impliment. My hats off to you guys who can build great passives but I'm not there myself.

I know the thread is about one path or the other but the builder has to part of the real world result in that for the average guy with minimal equipment for testing which is better for him, is different from which is better for a prodigy builder.

Last edited by SpinMonster; 17th October 2012 at 03:25 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Active or Passive bjackson Multi-Way 30 4th April 2005 10:49 PM
Passive into active MethMan Multi-Way 8 12th January 2005 04:58 PM
Active of passive audiobomber Multi-Way 9 31st July 2004 02:31 AM
dB loss by using passive crossovers? Active vs Passive and 1st vs 4th order Hybrid fourdoor Multi-Way 3 11th July 2004 09:16 PM


New To Site? Need Help?

All times are GMT. The time now is 11:45 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2