Bob Cordell Workshop at HE 2007

[Bob Cordell]

I have posted a Show Report for the HE2007 audiophile Listening and Measurement workshops we presented on my website at www.cordellaudio.com. Each workshop is described in detail and some pictures are provided as well.

The six workshops were as follows:

Amplifier Listening Comparison
Loudspeaker Listening Comparison
The Peak Power Demands of Well-recorded Music
Amplifier Measurement Clinic
Speaker Measurement Clinic
Active Loudspeakers - an Example


Once again I want to thank Stereophile Magazine and Ray Kimber for their generosity in sponsoring these workshops.

Cheers!
Bob

[tktran303]

Hi Bob,

Can you tell us more about the speakers you had on show?

Any plans to release details for DIY builders to have a go?

Tasty looking WWWWMT and 8 (or 10"?) 3-way, as shown in the 1st picture on your HE07 show report.

http://www.cordellaudio.com/he2007/HE2007-1.jpg

[Bob Cordell]

Originally posted by tktran303
Hi Bob,

Can you tell us more about the speakers you had on show?

Any plans to release details for DIY builders to have a go?

Tasty looking WWWWMT and 8 (or 10"?) 3-way, as shown in the 1st picture on your HE07 show report.

http://www.cordellaudio.com/he2007/HE2007-1.jpg

The WWWWMT is a 3.5-way active loudspeaker dubbed the Athena. It is described in some detail on my website at www.cordellaudio.com. There is not enough detail there to make it a DIY project, as it was an extremely challenging design. Each cabinet has four 125 watt MOSFET power amplifiers inside it. One for the tweeter, one for the mid, and one for each of the two pairs of woofers. The active crossover and EQSS equalizer are also inside the cabinet. The unit can be fed either a line-level signal or a speaker-level signal. In the latter case, the unit provides an internal 8-ohm dummy load at the speaker terminals.

The three-way was done by Peter Smith. Details of his speakers are at www.helarc.com. I don't know if the details of that speaker are up on his site yet.

Cheers,
Bob

[tktran303]

Thanks for your reply Bob,

Pjay had alluded to the 3-way that he had been working on. I didn't know they were finished.

Were these the 2 speakers used in the Loudspeaker Listening Comparison workshop?

Compared to the other reports on the HE07 workshops, this one was very brief, and I didn't quite get the take-home-messages.

Different loudspeakers sound different?
What is right and what is wrong is often hard to define?
Different tracks can highlight differences better that others?

regards,
Thanh.

[Bob Cordell]

Originally posted by tktran303
Thanks for your reply Bob,

Pjay had alluded to the 3-way that he had been working on. I didn't know they were finished.

Were these the 2 speakers used in the Loudspeaker Listening Comparison workshop?

Compared to the other reports on the HE07 workshops, this one was very brief, and I didn't quite get the take-home-messages.

Different loudspeakers sound different?
What is right and what is wrong is often hard to define?
Different tracks can highlight differences better that others?

regards,
Thanh.

Yes, these were the two sets of loudspeakers used in the loudspeaker listening comparisons, at least at the beginning of the show on Friday. Saturday morning we were making some changes and setup adjustments and I somehow managed to blow Peter's tweeter in one of his three-ways. So thereafter, we used his two-ways that had been previously used at RMAF.

I'm sorry that the reports were brief. Are you sure that you drilled down to the full reports on my website at www.cordellaudio.com under the HE2007 tab? Not just the abstracts. The show report was pretty much limited to the workshops, as we didn't get much chance to see a lot of the rest of the show.

Anyway, the takeaway on the loudspeaker comparison was that loudspeakers not only sound different, but they can influence how you perceive the sound of the other one. We also noticed that the ear-brain seems to adjust, and that sometimes after a switch from one speaker to another, the new speaker sounds better after some time has passed. There seems to be an awful lot of psychology going on there.

It was also very true that different music and tracks can make one or the other speaker more appealing, so the choice of speaker may depend a lot on the kind of music you are listening to. At the same time, we found it is very hard to make generalizations.

We also observed that level matching is very important in listening comparisons, but noted that level matching is not that easy to define when the two speakers being compared are inevitably voiced a bit differently.

Cheers,
Bob

[lineup]

Originally posted by Bob Cordell
I remember your comment about the resistor. I also believe this to be the case.
I actually added about 0.2 to 0.3 ohm in the output of the Super Gain Clone when I built it with this very same thing in mind.
This, together with the soft clip circuit, I reasoned, would make it sound more like a tube amp.

Originally posted by Bob Cordell
There is not enough detail there to make it a DIY project, as it was an extremely challenging design.

Each cabinet has four 125 watt MOSFET power amplifiers inside it.
One for the tweeter, one for the mid, and one for each of the two pairs of woofers.
The active crossover and EQSS equalizer are also inside the cabinet.
-----------
The three-way was done by Peter Smith. Details of his speakers are at www.helarc.com

Originally posted by al2002

Bob had a working version of his super gainclone (3886 chip amp)
and it measured under 0.01% THD at 50 W out at 20 kHz.
Not bad for a 3 buck chip.

hi Bob.

I actually got a hold of a fairly detailed description of the Gainclone system
you & your friends used in Bob Cordell Workshop at HE 2007 - Room 1627.
... don't ask me how ... there is not much detail in your homepage
... but in these internet times we live in, there are many ways ...


I have not the suberb speakers 3.5-way active loudspeaker Athena by Peter Smith as you used.
But the LM3886 curcuit setup, including 0R22 output resistors, is a pretty accurate copy of your Gainclone version.

I can say even with my own more normal 'good audio speakers' & in my livingroom,
this amplifier performs beyond most I've heard

And I can only agree with al2002:

Not bad for a 3 buck chip.

Lineup - regars


-----------------------------------
Appendix. References.
LM3886 - High-Performance 68W Audio Power Amplifier
http://www.national.com/ds/LM/LM3886.pdf

[Bob Cordell]

Originally posted by lineup





hi Bob.

I actually got a hold of a fairly detailed description of the Gainclone system
you & your friends used in Bob Cordell Workshop at HE 2007 - Room 1627.
... don't ask me how ... there is not much detail in your homepage
... but in these internet times we live in, there are many ways ...


I have not the suberb speakers 3.5-way active loudspeaker Athena by Peter Smith as you used.
But the LM3886 curcuit setup, including 0R22 output resistors, is a pretty accurate copy of your Gainclone version.

I can say even with my own more normal 'good audio speakers' & in my livingroom,
this amplifier performs beyond most I've heard

And I can only agree with al2002:


Lineup - regars


-----------------------------------
Appendix. References.
LM3886 - High-Performance 68W Audio Power Amplifier
http://www.national.com/ds/LM/LM3886.pdf

Hi lineup,

Thanks for your kind words.

Indeed I have been remiss in putting up more info on the Super Gain Clone on my web site. For that I apologize and know that I need to put up more stuff on the site.

I believe that a friend of mine will be making a kit version of the SGC available this year.

The Athena active loudspeaker systems were actually done by me. Each has four fully discrete 125-watt MOSFET power amplifiers built into the cabinet. Peter did the passive three-way speakers we employed at HE2007.

Cheers,
Bob