Matti Otala - An Amplifier Milestone. Dead or Alive

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#527
john curl said:
Not in the least, any competent engineer could make a comparable design. We just don't bother to complicate our designs to that extent. You might notice that Halcro's best designs save no money, offer no more output, and really don't sound any better than comparable designs. Since, you are from Australia, perhaps the local press has given you a more one sided input.
For example, when 'Stereophile' had to evaluate a very expensive speaker, that had a VERY LOW overall drive impedance, they turned to the Parasound JC-1 to do the job, NOT Halcro.
This is objective reality, not marketing-sales, Aussie style or anywhere else.
To not understand Halcro's true position, you also impugn Nelson Pass, who is now 'top doggie' on the hydrant, according to 'Stereophile'.
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John you are missing the point here. It's not about who makes the Halcro or where it comes from, or how it is marketed etc. The point is that it is a high feedback design which just happens to have an exemplary performance. Sure they could have gone a bit further and designed it to drive the very small percentage of 1 ohm speakers which represent a difficult to drive load but that would not have had anything to do with the application of negative feedback itself.

And speaking of 1 ohm loads how does your amps perform driving such a load ?? Can you run some tests and post the results here ?

I take it that when you say that Halcro are no better than other comparable amps then does that include your designs as well and vice-versa 😉

regards
trev
 
#529
disclaimer: I'm in a corny mood!

john curl said:
[snip]
For example, when 'Stereophile' had to evaluate a very expensive speaker, that had a VERY LOW overall drive impedance, they turned to the Parasound JC-1 to do the job, NOT Halcro.
This is objective reality, not marketing-sales, Aussie style or anywhere else.
[snip]
Click to expand...

Making a speaker with such low impedance dips (<0.3Ohms, if my memory serves well) is just as insane as making amps that comply with such a kind of a botch job.

So, nothing wrong with a current limit of 15Amps.

BTW, such speakers do NOT comply with European recommendations, regulations or directives (or whatever).
 
#530
nothing wrong with a current limit of 15Amps
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I wouldn't show your friend's favorite flag.
Please assume phase shift in the speaker 45 deg, so peak active current would be 10A. 10A*10A*4Ohm/2=200 W, halcro claims 400, yes, this is correct for the purely resistive load.

comply with European recommendations
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What? What recommendations? Please mention standard #

Final Sound Solutions B.V. Eisenhowerweg 8d 5466 AC Veghel The Netherlands manufacture panels with 0.3 Ohm dip,
 
#531
I thought the limit was 15Amps, regardless of the phase. Correct me if I'm wrong.

edit: European standard: minimal impedance (read: dips) should not less than 50% of the nominal impedance.
Can't give you a ref as my main PC is down. (HD crashed).

edit2: "Final Sound Solutions B.V., 0.3Ohms? Another botch Job?
Who's next with even 0.1Ohm perhaps? Should we make amps that can deliver 500Amps? No way! that's utter BS!
 
#532
Edmond, I am not talking about the WATT 1's that I personally own. I am talking about another company's speaker, considered one of the best in the world, today. It is only about 3 ohms. The JC-1 is rated at 800 Watts THX rated, into 4 ohms. Less than 4 ohms tends to overheat the amp, if it driven continuously. However, momentarily or just occasional peaks are OK.
 
#533
impedance dips

Okay John, your amp is doing a great job. But my point is that we should not run an amp into the ground that can't deliver its full power to an idiosyncratic speaker (famous or not), simply because it wasn't designed/intended to do such a job.
Maybe such speakers sound beautiful. Nevertheless, I regard extreme impedance dips as a design flaw.
Why should we adapt our amps to the incompetence of speaker manufacturers. We are doing our job and they should do their job. That means (among a dozen other criteria) a flat as possible impedance characteristic.
 
#535
dimitri said:
What? What recommendations? Please mention standard #
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IEC/EN 60268-5 says that minimum impedance shall not be lower than the rated impedance -20% (allowing for lower values outside the rated freq range, but this must be stated then).

So that panel with a 0.3ohms dip inside the rated freq. range should only be avertised as 0.375 ohms rated impedance if the manufacturer takes things seriously.

Where that 50% figure comes from makes me wonder anyway.

- Klaus
 
#536
john curl said:
Trevor, I am not being critical of Halcro. It is you who is not giving me equal billing on the same stage, that is all. The real critic was Martin Colloms in 'Hi Fi News'. PLEASE read his review and his credentials before passing judgement, yet again.
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Yeah, lets all pay attention to what Mr Colloms says.

The NFB in the amp goes round and round
Round and round
Round and round
The NFB in the amp goes round and round
All day long
 
#537
impedance dips

KSTR said:
IEC/EN 60268-5 says that minimum impedance shall not be lower than the rated impedance -20% (allowing for lower values outside the rated freq range, but this must be stated then).

So that panel with a 0.3ohms dip inside the rated freq. range should only be avertised as 0.375 ohms rated impedance if the manufacturer takes things seriously.

Where that 50% figure comes from makes me wonder anyway.

- Klaus
Click to expand...

So this standard is even more stringent. Apparently I confused that figure with my own 'standard' for amplifiers, which should also handle (for a limited period) half the impedance as the one they are designed for.
Anyhow, thanks for the correct figure.
 
#539
dimitri said:
Edmond,
I don't consider electrostatic panels as idiosyncratic speakers, sorry, after forty years of trials and comparisons. And yes, such speakers sound beautiful!

Typical impedance curve:
http://www.integracoustics.com/MUG/MUG/reviews/stereophile_sl3.htm
Click to expand...

Hi Dimitri,

Okay, many dips, but not as low as 0.3 Ohm, rather 1.5 Ohms (five times higher!).
BTW, Quad ESL 2805: 4..15 Ohms, ESL2905: 4..20 Ohms.

These latter figures suggest that there are no fundamental reasons, even in case of electrostatic transducers, why some speakers exhibit extreme impedance dips, sometimes as low as 0.3 Ohm. Therefore I insist that it's the responsibility of the speaker manufacturer to avoid such dips instead of putting an unnecessary burden on the amplifier (and blaming Halcro for lack of output power).

Cheers,
Edmond.
 
#540
Edmond, it is NOT helpful to insist that the speaker manufacturers conform to your idealized standard. They just don't do it. Dave Wilson made a mistake 25 years ago, when he designed the WATT 1, BUT every amplifier that I have made for Parasound can drive it, for the most part. Even the lowly Electrocompaniet drove it OK for years, in my OWN system.
The speakers that I referred to that virtually had to be driven by the JC-1 power amp are the YG Acoustics Anat Reference 2, reviewed in the Mar.09 issue of 'Stereophile'. Above 3KHz the load Z is about 2 ohms, 3 ohms between 150 and 700 Hz. Lousy load for sure.
 
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