Dr. Earl Geddes' amp on this speaker load?

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James Romeyn

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Dr. Earl Geddes' amp on this speaker load?
« on: 20 Nov 2010, 06:10 pm »
Amp is Dr. Earl Geddes' last known reference, 2003-2004 Pioneer VSX-D12 receiver, pure analog chip power amp, 105Wrms but rated only to 8 Ohms, switching mode P.S.  On the right load it's as good as SS gets.

Proposed speaker is Esoteric MG10, whose impedance graph is located here: http://esoteric.teac.com/resources/pdf/EsotericMG-10Measurements.pdf

How well-suited or ill-suited is this amp/speaker combination? 

TIA!

Jimbo   

cujobob

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Re: Dr. Earl Geddes' amp on this speaker load?
« Reply #1 on: 20 Nov 2010, 06:30 pm »
That's not the right receiver FWIW (pretty sure, at least), but could be the same chipamp setup.

James Romeyn

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Re: Dr. Earl Geddes' amp on this speaker load?
« Reply #2 on: 21 Nov 2010, 02:53 am »
Search DIYaudio where Earl posted the model himself, estimate two years ago. No idea of changes since then. 

I'm sure enough I'd take a $100 cash bet.  I exchanged emails with Earl about it.  It's correct.  You don't think I'd spend $200 on a Pioneer receiver otherwise do you?  :lol:   (Read my old thread where I traded $11k worth of separates for it...never looked back for a second.)

The 912 will likely sound like poop on the wrong load.  On a load that hovers around 8 Ohms and does not go much below that, moderate sensitivity, it equals or approximates the best cost no object SS.  In the DIY thread mentioned above Earl explains the Pioneer's excellence, way over my head except that the chip has parts tolerance specifications that would be impossible to achieve or cost many thousands of dollars in a discreet circuit.  That and super low XO notch distortion. 

Earl also described his proprietary amp test procedures, which the techs at DIY loved and requested he publish in-depth.  I'm quite sure Earl posted that the Pioneer passed his tests with flying colors.   

My main speaker is HPX'd @ 150 Hz.  Speaker is flat 8 Ohm impedance above the bass range, about 87 dB.  Superb performance up to moderately high levels then the amp gives up.  Same speaker plays tons louder with Atma-Sphere S-30 OTL, a marriage made in heaven and the best amp/speaker interface I've heard.

I think Earl's speaker is 96 dB.  If so, the 100W 912 on Earl's speaker is like 800W on my 87 dB speaker!  Yikes!         

Speedskater

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Re: Dr. Earl Geddes' amp on this speaker load?
« Reply #3 on: 21 Nov 2010, 03:21 am »
The "Audio Critic" magazine Spring 1997 reviewed the Pioneer SX-203  receiver:

http://theaudiocritic.com/back_issues/The_Audio_Critic_24_r.pdf

They reported that it could handle complex 1 Ohm loads!

James Romeyn

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Re: Dr. Earl Geddes' amp on this speaker load?
« Reply #4 on: 21 Nov 2010, 03:29 am »
Hi Speed!

That's a completely different animal, not even close.  The 912 is strictly 8 Ohm rated only. 

Speedskater

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Re: Dr. Earl Geddes' amp on this speaker load?
« Reply #5 on: 21 Nov 2010, 02:27 pm »
A different and older animal, for sure.  Heck it's got a discrete output stage. But it does show Pioneer's technical thinking and this article probably started the interest in using Pioneer receivers in better hi-fi systems.