History and Types of Loudspeakers

[j_j]

The same has been said by other notable crossover/driver designers (and not just Gedlee) I have followed in discussions, both designs have their strengths and weaknesses but key as mentioned in a very different thread "if done correctly".

It's been my experience that the right way to do an active crossover is not to mimic the passive crossover. Damping, etc, have little or nothing to do with the issue, rather the ability to keep the driver impedance out of the filter function is important.

For instance it is possible to have a near-power-conserving active crossover, using a combination of IIR and FIR filters that sums to exactly unity. (It is possible to have such with a passive crossover, but it can not be as close to power conserving, and then you see interesting impedance reflected into the amp, which may or may not be a good thing depending on the amp.

An active system costs more, most likely, because of power amplifiers.

 

[Groucho]

Hmm, well from my experience following those designing crossovers they feel if done properly both are trivial in context of equal sound quality/audibility.

Presumably, though, the designer of either type of crossover has to say that, in order to stay in business or to keep their own internal motivation alive.

From my own reading around the subject, and experiments I've done myself converting passive speakers to active, the claims for the superiority of passive crossovers seem tenuous to say the least. I would suggest they only really exist in the domestic setting for non-technical or historical reasons - active took over in professional applications long ago (something which, I suspect, 'taints' the use of active systems in domestic hi fi). Surely we can't get around the fact that even if passive and active can be given the same basic frequency response, and if we accept that perfect absolute phase correction is not necessary, one system has a single amplifier required to work over the full audio range, putting out much more power into a more variable load, with lumps of blancmange between it and the drivers. The amps in the active system have a much easier time and drive the drivers directly. How can the designer of the passive system make any claims regarding sound quality if he has no control over what amplifier is being used - unless he assumes that "all amplifiers sound the same" and that they are unaffected by load?

 

[Orb]

Look,
try both types of the PMC MB2S (active and passive) dbt ABX - its one of the few where it can be comparing like for like.
These are professional hi quality "monitor" speakers designed to work with Bryston electronics in active form, and therefore easy to use with top model (emphasis being their reference power amp) Bryston power amp in passive mode.
I am sure you will agree PMC should know how to do active monitors (that was their background originally), and they sell a fair amount of that model as passive to the professional world as well.

The context is if done correctly, and as most here use quality reference engineered amps this also applies - not talking about average amps or underspec ones with a demanding passive design.
I do feel Earl Geddes and other crossover designers wrong saying both have pros/cons and in real terms if done correctly differences in terms of being audible is trivial (this is from those that have done both) is very relevant.
However from what I have followed nearly every crossover engineer has mentioned it is much easier to work to an active design albeit being much more expensive to do at high quality "reference" product scope (putting aside passive costs have further external considerations).
This is turning into theory vs real world again like the other thread.....

Cheers
Orb

 

[Groucho]

The context is if done correctly... This is turning into theory vs real world again like the other thread.....

But they are not equivalent in theory or practice, are they? Maybe there can be some equivalence at certain 'levels of ambition' and to what degree we are prepared to dismiss certain supposedly-desirable attributes of active systems as myths. If we simply want to emulate a passive crossover with an active system, maybe we can claim they are equivalent. But even then, the active designer may find it hard to degrade the output exactly to the same level as the passive system - how does he perfectly emulate the lack of damping? We can, of course claim that the need for damping is a myth or exaggerated and dismiss it as unimportant, or state that in a system designed correctly the driver is perfectly matched to the crossover's somewhat spongy series impedance. But once we enter the realms of absolute phase correction, or identifying a need for steeper crossovers, only an active (maybe DSP) system can do it. But again, we can dismiss those requirements as myths also.

Martin Colloms says this about the Meridian 7200:

Right away certain speci?c characteristics were evident. It’s unquestionably ‘active’, with the grip, near e?ortless dynamic range, convincing integrity and authority that is typical of the breed.

He identifies a common difference between all actives vs. passives. This is my experience also. If it's a real difference (and not just imagined) which type of speaker is the more 'correct'?

 

[Orb]

Groucho,
so you want to ignore actual crossover designers or those with exceptional knowledge/experience such as Earl Geddes, and also not bother trying to test the experience yourself with the PMC MB2S in a dbt comparison - a professional background speaker manufacturer who specifically design and develop both active and passive models using Bryston electronics.
Martin Colloms has said exactly the same for the best passive speakers, anyway you were against anecdotal subjective reviewer comments in the other thread but if you insist on using them now bear in mind Colloms has said the same about the best passive speakers so we cannot be that selective.

Edit:
BTW I have heard apples vs apples in the past; PMC MB2S as active/passive at one of PMC's best dealers in Europe but the key was using the reference Bryston power amp with the passive speaker.
Cheers
Orb

 

[j_j]

Um, "Earl Geddes" not "Gedlee". Gedlee is a portmanteau of his and his partner's names.
As a note, extremely steep filters are probably not the best idea in the world, if one does it even slightly wrong, it is trivial to introduce pre-echo or serious time-alignment problems that will create some pretty astonishing vertical pattern issues.

Extremely steep filters are also not necessary, you shouldn't ever be running a driver that close to its limits, you're not getting linear response at that point anyhow.

I don't doubt one can make an active and passive version that are indistinquishable. I would say that might suggest that the active crossover might have been better designed to me, unless both the box design and the drivers are the best I've ever measured, and I've measured more than a few lately. Most of them were donated to college students, too.

 

[microstrip]

Martin Colloms says this about the Meridian 7200:
Right away certain speci?c characteristics were evident. It’s unquestionably ‘active’, with the grip, near e?ortless dynamic range, convincing integrity and authority that is typical of the breed.

He identifies a common difference between all actives vs. passives. This is my experience also. If it's a real difference (and not just imagined) which type of speaker is the more 'correct'?

These are the characteristics that can be expected from the technical aspects of active speakers. But it makes a lot more to create a good speaker for domestic audiophile use.

I find funny that active proponents always quote this sentence from the MC review when debating active and forget about the MC conclusions

"This exceptional loudspeaker presented two faces to us. Inexplicably, when driven via the 802.2i CD transport/control centre, the 7200 sounded elegant, controlled, powerful, very well mannered, wide in bandwidth and with exceptional detail and focus. It also sounded comparatively undynamic, downbeat and uninvolving musically."

However driven by the SPDIF input it sounded very good. IMHO this sentence just shows that high-end audio is really a complex problem.

 

[Orb]

LOL yes Geddes
Thanks JJ
Orb

 

[Orb]

Um, "Earl Geddes" not "Gedlee". Gedlee is a portmanteau of his and his partner's names.
As a note, extremely steep filters are probably not the best idea in the world, if one does it even slightly wrong, it is trivial to introduce pre-echo or serious time-alignment problems that will create some pretty astonishing vertical pattern issues.

Extremely steep filters are also not necessary, you shouldn't ever be running a driver that close to its limits, you're not getting linear response at that point anyhow.

I don't doubt one can make an active and passive version that are indistinquishable. I would say that might suggest that the active crossover might have been better designed to me, unless both the box design and the drivers are the best I've ever measured, and I've measured more than a few lately. Most of them were donated to college students, too.

OK JJ,
which speaker manufacturers are implementing active correctly and which ones are not?
I am sorry but such a vague-generic statement is really bad, and if it is an issue was anything done to correct this with the major pro manufacturers such as PMC, ATC, Proac,etc?
It is fair to say then that majority passive crossovers might had been better designed and maybe a consideration that sets some of the best passive speakers apart from the rest.

Thanks
Orb

 

[Orb]

To put it into context and comparing like for like that must take into consideration top electronics for the passive model.
PMC MB2S-A £39k
http://www.funky-junk.com/pmc-mb2s-a-active-main-monitors-pair/

PMC MB2S £11k
http://www.funky-junk.com/pmc-mb2s-passive-monitors-pair/

Thanks
Orb

 

[Groucho]

Groucho,
so you want to ignore actual crossover designers or those with exceptional knowledge/experience such as Earl Geddes, and also not bother trying to test the experience yourself with the PMC MB2S in a dbt comparison - a professional background speaker manufacturer who specifically design and develop both active and passive models using Bryston electronics.

Unfortunately I don't have a PMC dealer in my locale... and it's raining, anyway! I'm not ignoring anyone, but just weighing what they say against others who take the opposite view, plus the self-evident (YMMV) technical 'correctness' of active crossovers. And the "level of ambition" question, where we may be able to make audibly identical passive and active speakers if we are trying to make something that sounds like the average audiophile's idea of what a speaker should sound like, but maybe such as Meridian take it to another level that only DSP active can achieve - my own speakers are the poor man's version

 

[Orb]

Agreed that is definitely one important differentiation for active; specifically DSP active xover/speakers such as Meridian and Grimm Audio that provide greater scope compared to the more traditional active such as from Linn,PMC,Proac,ATC,etc.
But key is do they provide real world better and audible SQ in all areas such as integration/dynamics/FR/phase/reduced distortion to the best passives using the best electronics.
Theory will say yes, but in reality it is not so clear cut going by actual designers and listening to the traditional active designs where it is possible to do a like-for-like comparison (but then some will debate whether implementation is ideal although that can be argued for both active and passive).

Edit:
Missed saying it is unfortunate there is no way to really compare real world speaker implementation of DSP to identical passive, where the manufacturer has designed both to "reference standards".
Cheers
Orb

 

[Phelonious Ponk]

What's interesting is how the very first kind of loudspeaker invented (the electrodynamic speaker) is still, for most, the best available. Planars are for the most part electrodynamic with a different motor than a cone speaker. I'd have to say that in the useful (i.e. not budget or sonar) audio space, 99.9% of the rest are electrostatics.

I didn't mention piezo speakers for a reason. I don't do sonar, and I haven't met many audio piezo's that performed the way I'd prefer. Plasma, flame, and other speakers that make ozone aren't really interesting for reasons unrelated to how they sound.

There certainly seems to be some space for improvement in basic mechanisms, but I don't know what it is, either.

I don't think I've met one. They were very popular as a cheap substitute for compression horns in inexpensive PA for awhile, particularly in floor monitors, where the long throw of the horn is unnecessary. But they always sounded a bit like bacon frying. Don't like them.

And in spite of having heard a few good implementations of metal domes, I still find that most of the speakers I like have either really good compression drivers (PA) or soft dome tweenters (studio monitors and hifi)

Tim

 

[microstrip]

I remember that the Motorola piezo tweeters were very easy to source and inexpensive when I was still in my DIY speaker phase. Although I can not remember the brand and model, I read once a review of a speaker in Stereophile that used them, and AFAIR the famous Dahlquist DQ10 used them as super tweeters.

 

[Phelonious Ponk]

I remember that the Motorola piezo tweeters were very easy to source and inexpensive when I was still in my DIY speaker phase. Although I can not remember the brand and model, I read once a review of a speaker in Stereophile that used them, and AFAIR the famous Dahlquist DQ10 used them as super tweeters.

Supertweeter sounds like a perfect use for piezos; outside my range of hearing.

Tim

 

[j_j]

OK JJ,
which speaker manufacturers are implementing active correctly and which ones are not?

Hard to tell, frankly.

I have yet to see a paper on a proper FIR design for matching crossover points, etc, even though the math is dead cold in modem design, for a harder problem (mathematically speaking).

Once again, I have to say that I find that audio is often behind the state of the art, again, often because there is serious confusion between least-mean-squares measurement and perceptually appropriate measurement.

 

[j_j]

I don't think I've met one. They were very popular as a cheap substitute for compression horns in inexpensive PA for awhile, particularly in floor monitors, where the long throw of the horn is unnecessary. But they always sounded a bit like bacon frying. Don't like them.

Well, I'm willing to concede that somebody out there might have made one that sounds good, hence my more gentle phrasing, but no, I haven't met one I liked. I did use them in a deliberately cheap design ?40? years ago, but it was for college students who had no money. (i.e. me, and it was marginally better than no high frequencies)

 

[j_j]

And in spite of having heard a few good implementations of metal domes, I still find that most of the speakers I like have either really good compression drivers (PA) or soft dome tweenters (studio monitors and hifi)

Tim

Have you ever tried Beston ribbons?

 

[tkollen]

I remember when I bought my pair of Dahlquist DQ-10 in the seventies I was at first very impressed with the spaciousness of the sound but after some time the high end became overbearing. I think I could attribute this to the Peerless tweeter and the Motorola super tweeter. I was just about to sell the speakers when I tried replacing these two drivers with the newly released Sequerra HF-1 ribbon tweeter. This replacement especially but also including other later mods ( Dynaudio midrange dome, revised filter design etc.) transformed the DQ-10 to the best speaker of all times, at least to my ears. The system has now a huge and expansive sound field (both width and depth), is very dynamic, instruments and voices are projected at the proper height and with pinpoint accuracy. Voices sound natural and transparancy rivals most electrostatic systems.

In the last 35 years I've owned most of the speakers on the "The 12 Most Significant Loudspeakers of All Time" list on this site. The only pair I've kept are the DQ-10's.

 

[Phelonious Ponk]

Have you ever tried Beston ribbons?

I don't think I've ever heard them. I've heard several implementations of the Heil Air Motion Transformer. Similar at all?

Tim