Active v Passive speakers - discuss

[RobHolt]

Good and bad in both approaches so lets discuss them.

For starters, what do we consider as active?

Is it the lack of apparent passive crossover or does it require line level response shaping to properly qualify as active?

 

[flatpopely]

Active: Frequency division done within line level crossovers and output of same fed to required number of power amps to feed drive units directly.

Passive: Entire frequency range supplied by power amp to crossover network that divides signal into correct frequency response for each drive unit.

In both cases the frequency response of the drivers/speaker are taken into consideration by the active or passive network.

 

[Labarum]

This Wiki is not particularly well written

http://en.wikipedia.org/wiki/Active_speaker

But

A`"Powered Speaker" has an internal amp or amps.

In an "Active Speaker" each driver is directly connected to it's own amp and any crossover function is effected at line level - ie before the power amps. The amplifiers and line-level crossover may be built into the speaker cabinet or housed in a separate case or cases.

Arguably a speaker that uses a single full range driver may claim to be active as there is no passive crossover between the amp and the driver.

 

[flatpopely]

I really tried to be succinct and precise with my explanation.
You are correct with direct driven drivers, I own such a device.

 

[RobHolt]

This Wiki is not particularly well written

http://en.wikipedia.org/wiki/Active_speaker

But

A`"Powered Speaker" has an internal amp or amps.

In an "Active Speaker" each driver is directly connected to it's own amp and any crossover function is effected at line level - ie before the power amps. The amplifiers and line-level crossover may be built into the speaker cabinet or housed in a separate case or cases.

Arguably a speaker that uses a single full range driver may claim to be active as there is no passive crossover between the amp and the driver.

On the latter point, that is still a passive crossover and indeed even active systems have some passive element - they don't eliminate the passive crossover entirely as is often thought.

Consider a simple 1st order electrical crossover (lets use the correct term - filter) obtained by connecting an inductor in series with a bass driver. The inductance causes rising impedance with frequency (the definition) and therefore current flow reduces and drive level falls - roll-off occurs.
Eliminate the inductor and we still have a 1st order electrical filter because the bass driver motor itself is inductive. It makes no difference in terms of the filter characteristic how the inductance is distributed - half in the coil and half in the motor for example or the entire lumped value. The knee of the filter is determined by the lumped value.
So, when we connect our power amplifier directly to the bass driver we still have a first order filter.

We can go on to look at the acoustic properties of the driver and see that mechanical considerations will also cause roll-off, and this acts in combination with the electrical filter to produce in effect a higher order filter action.

So we can say that an active speaker will always be part passive

 

[flatpopely]

Rob

In the context of established thinking can we agree that the electrical properties of a drive unit do not constitute the crossover. They are part of the calculation of the passive or active crossover but not actually part of it. If not then there is no such thing as an active, moving coil, loudspeaker and the whole debate is then moot.

 

[RobHolt]

I disagree Andrew.
The properties of the driver are very much part of the crossover.

It depends how precise you want to be but strictly speaking there is no such thing as an active moving coil loudspeaker - there is always a passive filter in operation.

I think that much established thinking would recognise this.
Right is right and wrong is wrong.

The argument really is about were the filters are distributed (all of them), the complexity of the filters and the benefits of moving (most of) them into the small signal area or leaving them in the speaker high level crossover.
That's why I said it might be a complicated discussion

 

[flatpopely]

Well then we need to agree to disagree. I think you need to look at what loudspeaker manufacturers themselves regard as active and passive though.

 

[Richard Dunn]

Well then we need to agree to disagree. I think you need to look at what loudspeaker manufacturers themselves regard as active and passive though.

What it is called is entirely down to the marketing men and what bullshit they think they can get away with and foist on you.

As I said in the old thread, this manufacturer says that to make it simple an active speaker means active electronics is built in it, and that means the amplifier and that can also mean the crossover and multi amps.

 

[RobHolt]

Well then we need to agree to disagree. I think you need to look at what loudspeaker manufacturers themselves regard as active and passive though.

I know what they regard as active and passive and for simplistic argument it holds well enough. it is however wrong if we are discussing filters, and the final speaker response reflects all parts of the chain.

it just depends how deep you want to look and how precise you wish to be.

 

[flatpopely]

You should rename the thread Rob. Can a moving coil loudspeaker ever be active?

 

[Richard Dunn]

Big and effective active speakers are limited by building the amp in. In my opinion the genre for home audio is only really suitable to av systems and cheap computer based systems like the AVi much hyped thingy ADM9?. Interestingly the Class D fad that Jerry is rehyping at the moment on forums is very suitable for this as small transformers means less field interaction between amp power supply and voice coils.

Now big active speakers designed as studio monitors have a fan base for home audio as well, but I have never seen the point.

 

[flatpopely]

What it is called is entirely down to the marketing men and what bullshit they think they can get away with and foist on you.

As I said in the old thread, this manufacturer says that to make it simple an active speaker means active electronics is built in it, and that means the amplifier and that can also mean the crossover and multi amps.

Not in the context of the OP I'm afraid. But well posted in the context of your anti dealer sales model.

 

[RobHolt]

You should rename the thread Rob. Can a moving coil loudspeaker ever be active?

It cannot ever be if you base the definition around the use of filters because you always have a passive filter involved.

If we redefine the definition and use the one you used earlier in the thread then people can discuss around that. There are many nuances within the topic.

There is no one definition on this, especially when we start looking at why one approach sounds better or worse than the other and that is surely what matters. It all comes back to filters - how many and where are they positioned in the chain. What are those filters doing and where can they do it best.

There is also passive line level against active (as in a powered circuit) line level.

Lets talk about the lot.

 

[Richard Dunn]

It cannot ever be if you base the definition around the use of filters because you always have a passive filter involved.

If we redefine the definition and use the one you used earlier in the thread then people can discuss around that. There are many nuances within the topic.

There is no one definition on this, especially when we start looking at why one approach sounds better or worse than the other and that is surely what matters. It all comes back to filters - how many and where are they positioned in the chain. What are those filters doing and where can they do it best.

Simples remove as many of them as possible

Everything mechanical is a filter, your room is a filter, your ears are a filter, your brain is a filter, why the FFF do you want to create more. Design the mechanical things to do it for you and only use filters to protect things that can't cope with the FFR.

 

[RobHolt]

Simples remove as many of them as possible

Everything mechanical is a filter, your room is a filter, your ears are a filter, your brain is a filter, why the FFF do you want to create more. Design the mechanical things to do it for you and only use filters to protect things that can't cope with the FFR.

Oh yes, filters everywhere.
Every plug in every socket, every inch of cable, every pcb track - every single interface along the line right from the singer's mouth through to the listeners brain.

That is why I'm quite relaxed about using a few more in the system if it gives me a better listening experience. Thousands of filters and a few more isn't destructive IMO.
Can be constructive.

Relying on mechanical properties is fine but those alone seldom do the job well enough.

 

[sq225917]

So towards an agreed definition then.

Active speaker: one where all the filter components than are not physically part of the drive units themselves act upon the line level signal and sit before the amplification, one amp being used per drive unit.

I think this is a broad church that takes in everything except self powered speakers with a passive crossover after the amp or passive loudspeakers.

Maybe we can agree that ES14's are curiously semi active when used biamped....lol oh no he's gone....

 

[Richard Dunn]

OK back on subject, can anyone see anything wrong with my definition. I have always applied it even back in the 70's and I think most people applied it this way back then.

Active doesn't only mean active crossover it means any application of gain stages even if they are unity gain. So for me an active speaker is any speaker that has to be plugged into a battery or the mains because it has gain stages. Now that starts with the amp / amps as they are the thing that is connected to the speaker drivers. You can then go back in the system further and further until you create a box with everything in like a portable CD radio

Now if we want to discuss the merits of active v passive crossovers then that is the subject not active loudspeakers. AND as Rob very rightly says there is no such thing as an entirely active crossover, everything is a series of compromises, that if you are sensible you arrive at with your ears as there are so many variables to take into account using fixed measurement and design criteria, but that is the start point.

 

[RobHolt]

I like it Simon.

 

[Richard Dunn]

I like it Simon.

So if you want me to bend to your definition then how do you differentiate between something like the ADM9 and a full (so called) six pack (what a marketing cliche) Isobarik system.

I once (in the early 90's) built amps into a pair of Cube 1's, but there was no active crossover, they were passive bi-amp as there was no crossover apart from a cap on the tweeter, are these part of the discussion?