[James Tanner]

Hi All,

As suggested by MAD - here is something I wrote on the subject a few years ago.  We can use it as a start point.

The Importance of Staying Active

Recently there has been a lot of interest in "Active Loudspeakers." Active loudspeakers are those in which the drivers (woofer, midrange, tweeter) are directly connected to the output of an amplifier. This is referred to as active bi-amping, tri-amping etc. There are no "passive" components (large size resistors, capacitors, coils etc.) in the signal path between the amplifier and the loudspeaker driver(s).

There is some confusion in the market place at this time because of "passive bi-amping." Passive bi-amping assign a separate amplifier to each individual driver but it still uses the "built in passive crossover" to control which frequencies are assigned to which driver and the per octave roll-off characteristics.

In a true active system this assigning of frequencies and roll-off is handled at the small signal level stage, using an "electronic crossover" which is positioned between the preamplifier or other input source and the individual amplifier(s). There are two main types of active systems currently in the marketplace. One is the small or medium sized loudspeaker that also houses the drivers, crossover and separate amplifiers in a single enclosure. Two, the larger active systems that house the drivers in an enclosure but provide the ampliification/crossover with external electronics usually placed adjacent to the loudspeakers. The other option available is the so called "powered speaker" where a single amplifier is attached directly to the rear of the loudspeaker but the internal passive crossover is still used. This is not truly an active system (due to the use of the loudspeakers built-in passive crossover) but the advantage of having the power amplifier/speaker combination in a single portable unit is very convenient and cost effective.

An active system is certainly more costly to implement properly. The extra cost of separate amplifiers superior crossover parts and quality drivers certainly adds expense. If implemented correctly though the advantages of active systems are well worth it

Some aduantages of Active Systems are:
1) More efficient use of power.
2) Superior direct coupling of drivers to the amps provides increased control of drive units and damps unwanted resonance's in drivers.
3) By splitting the frequency bands before amplification crossover filters become easier to design and predict.
4) Control of level. phase {delay) and driver anomalies (response/resonance/phasej is simplified.
5) Higher SPL's can be achieved in larger systems (typically you get a 4dB improvement in level with the same power).
6) Convenient, smaller, one package solution to customer with the smaller active systems.

The foregoing is not in any way meant to diminish the value of passive systems. A good well designed passive system will outperform a poorly designed active system any day of the week. Passive systems are much more cost effective from a value/performance level standpoint than active systems. Passive speakers allow you to choose or upgrade to a specific amplifier now or at a later date (the larger active systems employing outboard electronics also offer this option). Passive systems do not require a power outlet near your speaker or the ugly power cord that attaches it. And finally, passive systems are usually a little more forgiving of the quality of the signal input than active systems and therefore, easier to listen to longterm.

 

[Tyson]

Good topic.  I'm running fully active on my speakers and it's actually less expensive because I am able to use medium powered amps on the mids and tweeters and a higher powered amp on just the bass woofers.  If I were running a passive speaker system, I'd have to use a real "monster" amp to get the same level of bass, dynamics, control, and ease that 3 more modest amps give me in a fully active setup.

[b5pt9]

Anyone have any thoughts as to how the following might compare:

1. Passive PMC IB1 / 14BSST
2. Active PMC 1B1 / 2 x 10B STD crossovers / 4BSST bass / 9BSST mid & high

Does the 10B STD have suitable crossover frequency and slope selections?

[James Tanner]

Anyone have any thoughts as to how the following might compare:

1. Passive PMC IB1 / 14BSST
2. Active PMC 1B1 / 2 x 10B STD crossovers / 4BSST bass / 9BSST mid & high

Does the 10B STD have suitable crossover frequency and slope selections?

The crossovers made for Active PMC's are custom units so the crossover slopes, gain, overload protection and frequency are proprietary to PMC.

james

[b5pt9]

Anyone have any thoughts as to how the following might compare:

1. Passive PMC IB1 / 14BSST
2. Active PMC 1B1 / 2 x 10B STD crossovers / 4BSST bass / 9BSST mid & high

Does the 10B STD have suitable crossover frequency and slope selections?

The crossovers made for Active PMC's are custom units so the crossover slopes, gain, overload protection and frequency are proprietary to PMC.

james

I've aquired all components listed above for option 2.  Is there any point in trying this or would the effort be futile?  I would remove the passive crossover and run the driver leads direct to the 3 sets of binding posts on the speakers.

[werd]

Active speakers tend to be more boxy in shape( i am sure there exceptions) while most passive speakers come in all shapes. Including those that take advantage of advancements in cancellation of internal standing soundwaves. However if i ever won the lottery, i would most certainly do some type of active Bryston/ pmc system. Having brystons coupled within inches of their drivers seems heavenly.

[Mad Mr H]

Anyone have any thoughts as to how the following might compare:

1. Passive PMC IB1 / 14BSST
2. Active PMC 1B1 / 2 x 10B STD crossovers / 4BSST bass / 9BSST mid & high

Does the 10B STD have suitable crossover frequency and slope selections?

Hi,

Looking at your kit list you already have the 14B SST...

So If you were going active I would go

14B SST bass
4B SST Mid/Hf

The cross over point for the IB2i are 380Hz and 3.8Khz . 24dB/oct L-W type

That is the info on the PMC brochure.

If you wanted 3 way then I would sell the 9B and get another 4B (or 14 or 28!)

[b5pt9]

Hey MadMrH thanks for the info.

My plan was actually to sell the 14B if I can end up with better results by going active and using 4BSST on the bass drivers and 4 channels of the 9BSST on the mids and highs.  Then I could buy a BP26

On paper the total wattage to the speaker is identical with both options: 600W from the 14B or 300W + 150W + 150W with the active setup.

The 10B STD limits me to either 300Hz or 450Hz for lowpass and 3k or 4.5K for highpass.  Slope options are 6, 12 or 18 dB/oct.  Per your info the ideal settings would be 380Hz, 3.8kHz and 24db/oct.

So the question is would the benefit of active amplification offset the drawback of deviating slightly from the factory IB1 passive crossover frequencies and slope?

[Daniel Datchev]

Hi b5pt9,
all 3 way speakers made by PMC are using the same crossover frequency 380Hz and 3.8kHz and 24dB/octave.
If I were you I would remove the passive crossover and drive the drivers directly from the amplifiers.The question which remains is about the tweeters. In active PMC speakers they are larger, but if you drive them carefully I think there will be no harm to blow them up.
Daniel

[rahman]

I think this thread, and previous ones like it, highlights an issue which, to my knowledge has largely remained unclear. That is, what options are available to PMC owners to upgrade their existing passive speakers and Bryston amps to an active system (i.e properly avail of any proprietary PMC know-how, active equipment (cross-overs, amp tweaks etc), and support).

Whilst I recognise the potential commercial implications of such an upgrade path on the sales of the active range, I'm guessing that active sales are likely to be to pro-users predominantly and I'd suggest that these sales would likely remain unaffected by allowing consumers an upgrade path in this regard. i.e studios wanting active speakers are likely to continue to acquire said systems upfront with all the tech support/service that comes along with it. Unlike consumers who, for lack of financial resources or auditioning options etc, are more likely to upgrade gradually. And it's probably better facilitating a proper ugrade route than leaving consumers with little option but to try it on their own and risk damaging equipment (and potentially themselves) in the process.

Any comments/info welcome.

Cheers
Adrian
ps: the literature that came with my PMCs indicate that an upgrade path exists, but doesn't explain what it is.
pps: I personally am not looking to upgrade in the near future, but would like to know if such an option exists so I can weigh that up with other available upgrades/purchases going forward.

[James Tanner]

Hi Rahman,

I assume Ian from PMC will step in to answer this one for you.

james

[rahman]

Thanks James.  Looking forward to Ian's input.  Hope I haven't set a cat amongst the pigeons.

[Daniel Datchev]

Hi
about active speakers in case of PMC it is actually active system comprise of dedicated speaker for active system plus Bryston crossovers and amplifiers. I don`t know what PMC think about converting a passive speaker into active, but as Mr.Tanner has mention the speaker must be build for this purpose. Maybe we have to look at this issue as having a part of the required equipment I mean Bryston amplifiers and add the missing PMC part. I don`t think it worth converting one passive speaker into active with some exceptions. The price paid by anyone will become very high and close to the price of PMC active system. The only way which I could see is to use audio gear you have to be reduce from the price of the PMC system.
Daniel

[mvwhiting_83]

Hey guys, sorry for the delay.... Long weekend ...

So for going passive to active, it isn't possible . We had an end user one time try to remove his internal passive crossover and use an external active crossover (not a 10B), and ended up blowing his drivers .... Our active systems are a slightly different animal in terms of the build process and components used.

To achieve the most out of your passive three ways I highly recommend triamping.  All of the benefits that James mentioned before can be touched on although not thoroughly exploited like that of an active system.

[Daniel Datchev]

Hi.
I agree. What is my understanding being an engeneer not audio of course, tells me that is not so simple to convert a passive speaker into active.There are the sound pressure, phase, delay which have to be calculated and coherent sound to be produce by the drivers. Think about if it is an easy job we could have hundreds or thousands of active speakers, which not the reality. If somebody like to go active the only way is by buying an active speaker now way converting passive speaker into active. Maybe I am not right but the way of learning by mistakes is very costly.
Daniel

[Tyson]

Active crossovers are not any more difficult to design than passive ones.  If you know what you are doing. 

But, you have to distinguish between building an active system as a manufacturer, versus doing it as a consumer.  If it's the former, it's still easy to maintain control of the slopes, crossover points, baffle step compensation, box tuning, driver selection, crossover selection, even amp selection.  One advantage to going fully active for manufacturers is that you can really take a full-system approach to matching drivers, amps, and crossovers.  With a passive system, you have much, much less control.  Plus, you can use less powerful (and less expensive) amps when you have each one only doing a small portion of the system.  The other advantage is you can use steep L-R phase coherent crossovers.  Combine this with the ability to time-delay the outputs to each driver so they are time as well as phase coherent, with very little overlap or playing outside of their bandpass, and the advantages for active systems become overwhelming.

However, as a consumer, if you are trying to "rip out" a passive crossover of an existing speaker system and replace it with an active crossover, you had better be doing it with the support of the speaker manufacturer - there are too many variables that you must know in order to get the speaker working properly again.  Without direct and specific info from the manufacturer, you are going to be hopelessly lost, trust me.

[Mad Mr H]

Hey MadMrH thanks for the info.

My plan was actually to sell the 14B if I can end up with better results by going active and using 4BSST on the bass drivers and 4 channels of the 9BSST on the mids and highs.

On paper the total wattage to the speaker is identical with both options: 600W from the 14B or 300W + 150W + 150W with the active setup.

I have to say that for IB1's I would run them on a 14B SST that you already have.

IF you run them hard then I would consider an additional amp to drive the mid/hf section. In Passive Bi Amp format.


The upgrade path from the IB1 is, IB2 MB2 BB5.......



Ian (PMC) is correct that you are better to stick with the PMC built cross overs and passive bi or tri amp.

For a few of us then ripping the internal cross over out and running active is in my opinion an option, and one I have done many times on many different systems.........You have to have an understanding of what you are doing, So in general I would suggest people stick to what PMC have designed, For me its more about "because I can" and "why not", I have NEVER blown a driver , thats only done by excessive power to the driver, BUT in an active system that mistake is fairly easy to do !!!!


In a full PMC active system, there are a number of changes throughout the signal path which offer an advantage over the similar passive system. For domestic use passive is worth sticking with. If you are driving asystem hard in commercial application then active is the way to go..............