thoughts and views on PMC OB1's

Ian my references are usually in retort, and they are not definitive, they are only an opinion, I am not ridiculing Mana, or ATC, mereley James' arrogant stance that they ARE the only answers, and if someone disagrees with him, which is their given right, then they are wrong. He then belittles their arguments with arrogant staements like this:

"There will possibly never be a system which is 100% accurate in all respects. But you can get a heck of a lot closer to this than most of you believe."

"And that has to be the objective goal of hi-fi, otherwise it's not hi-fi."

"Your clients are blinkered fools, in my opinion. You have absolutely no idea what constitutes a good sound."

"I'm sorry to have to say this, but until such time that you have heard an LP12 and Naim preamp on a good pile of Mana, you really don't know what you are talking about."

"Basing judgements on 'reputations' is not good enough."

"That's because I've heard precious few off Mana which sound acceptable. And I've heard a lot of hi-fi in the past 22 years."

"What do you mean? Seriously. Do you think that a Ninja LP12 / Naim ARO / ESCo-retipped Linn Troika on phase 9 Mana, and a Naim NAC 52 on phase 9 Mana, and ATC SCM 100A SLs on phase seven Mana aren't accurate? Where have you heard such a system?"


I was ignoring him up until the snide comments re my kit, I challenged his arguments, but have only retorted to his insults.

I'm sure these pieces of equipment give him and many others huge enjoyment, and as a system it wasn't that bad, but I was expecting a lot (maybe too much) I have never ruled Mana out, just don't feel the need at the moment, and naim stuff is ok just not to my taste, but after all the hype I was expecting to be amazed, and I wasn't I was polite about it, but prefered what I had, however when James came to mine, with the intention of disecting my kit, and not to listen to music, then proceeds to ram his opinions down my throat about a problem that doesn't manifest itself to me, then the gloves are off, so to speak, sadly I rather like James' company, but until he drops it then I may reserve the right to retort.

 

AK, GET OVER IT!!!

You have some serious 'issues'.

I'm sorry I didn't like your system, and I was only trying to be helpful.

 

Again James a sweeping generalisation. Whilst the typical 2nd order passive crossover does indeed use the drive units out of phase with each other, this is not always the case. Well designed examples exist with the drive units operating in phase. I'm surprised with your experience you were seemingly unaware of this.

 

Ian,

You are welcome aboard providing no Sun/ra/Brotzman/Mingus, and plenty of booze.

 

You've said this about a million times already. No need to keep saying it. Your position is clear.

WM, I'll bring enough booze to sink the Canadian navy.

-- Ian

 

Ian,

Are you suggesting that the 'slight hiccup' on that sub just of the coast of Erie had anything to do with my re-routing of the main charging circuit?, I strongly refute those allegations, I only touched the Torpedo lunchers

 

long hard and full of dead seamen...................


I'll get me coat.

 

Not true, AFAIK.

 

Really James

Which bit?

 

Don't worry WM, I'm currently in the process of refitting Ian, at great expense I should add, with the new improved "Congo Bongo MRPDS" (Multiple Re-entry Plinque and Destroy System). No need for tactical battlefield Brotzmans anymore

 

Read this:

http://www.enjoythemusic.com/magazine/manufacture/0403/

Thoroughly!

 

It doesnt say a great deal does it? In fact it's pretty meaningless. Who is the author, and what are his credentials?

 

It's written by ATC's technical chappies, I think. There is very similar blurb in the owner's manual.

It says quite a lot, in fact, and is far from 'meaningless'.

Bunch of amateurs, though, if you ask me.

;-)

 

Well it could just as easily be written by their marketing department. It would be better if they could come up with something a bit more meaty with some proper technical arguments/examples/measurements.

Would certainly be more meaningful than this verbage.

 

ATC make both active & passive models, Robbo.

I don't think that you can accuse them of 'marketing' in this instance.

This is the relevant bit:

A major source of difficulty in designing a Passive loudspeaker system lies less in selecting the drive units or enclosure, but in designing and building the passive crossover. This device with its large capacitators and resistors receives the low impedance, full frequency output from the amplifier, and divides it between the two, three or more drive units. It is hardly surprising when taking a look at the size and complexity of these unpowered components that the passive crossover can absorb up to 20% of the amplifier's power output. And that's not the only problem!

The magnitude of the frequency response of both active and passive loudspeakers can be controlled, with good design, to be within 1dB of one another. However, the phase component of the frequency response will always be better in an active system. The active filters produce better filter roll-off characteristics at crossover. Combine this with the inclusion of a variable all-pass filter at each crossover point to correct the phase response of the drive units through the crossover regions and the result is a loudspeaker with much better group delay characteristics. The benefit to the listener will be improved polar response and therefore radiated power response. Such an active loudspeaker will have a large stable sound field with stable imaging and source location. Very difficult and costly to achieve with a passive loudspeaker system.

A passive crossover will only operate correctly into the load impedance of a particular loudspeaker drive unit. However, the impedance of a loudspeaker drive unit will change with the amount of power input. This is because loudspeakers are very inefficient and most of the input power is dissipated as heat in the voice coil. As a result the temperature of the voice coil will rise and because copper has a positive temperature coefficient of resistance the impedance of the loudspeaker drive unit will rise. The result will be frequency response errors as the filters move from their designed response with increased input power. This effect does not occur in active loudspeakers where the filter response is maintained independent of input power to the loudspeaker.

 

Yeah but this is irrelevant if you don't LIKE the sound they produce accurate or not.

 

Of course it is, but you were very nice about my system at first, it was only when I made some suggestions (which were honestly intended to be helpful) about yours, that this sudden dislike for my system became apparant.

Enough, already!

 

Seems to be relevent in terms of achieving high SPLs only which isnt really related to sound quality.

I'n no electronics person, so perhaps an expert could comment. There still has to be filters in the active speaker to filter out the unwanted signal frequencies prior to the amplifier modules. These filters presumably consist of capacitors and inductors. Won't these filters introduce phase anomalies that are then amplified and reproduced by the drivers, giving an end result similar to a passive speaker?

Dont agree. I have heard many passive speakers with very stable imaging and soundstaging, many of them relatively inexpensive. One of the comments that seems to be fed back from listeners of your system is that it doesnt image. It's obviously not the speakers then.

 

OK James. A bit different from the absolutist BS I pulled you up on though isn't it?

In addition, the guys from the ATC marketing department add the caveat that it's

Frankly James, at the prices ATC charge, most speaker designers are able to incorporate an excellent crossover that performs as required. Whilst there is no doubt Active does have theoretical benefits, it is also the truth that there are potential compromises, particularly if the unit is specced by a designer who does not use his ears, and refuses to believe that amplifiers and accesories make any difference.

You stated, quite incorrectly, that passive crossovers require the drive units to operate out of phase. Now you are trying to cover up your apparent lack of knowledge on the subject by cutting and pasting advertorials for your favourite speaker company

Fair play for trying

 

No, it isn't incorrect, go back and read it again more carefully, Merlin.

I think ATC are very reasonable, btw, given the high performance.

It's not an 'advertorial': ATC produce passive designs as well.

I'm sick & tired of arguing with you, Merlin. Your invitation to my place is withdrawn. Frankly, you are a pain in the arse.