(Informal) Chat with Dr. Earl Geddes of GedLee Audio

Last week I asked Earl - in a thread here - if he would be willing to come on my YouTube channel and talk about a few different topics ranging from nonlinear distortion to how reviewers can do better. He obliged. It was a great opportunity to talk to someone who I truly admire and respect. You’ll have to excuse me for occasionally “fan-girling”. ;) :D


* I'll try to add bookmarks to this when I get the time

Personally, the discussion was very beneficial for me as it gave me some ideas on areas I can improve my reviews. If you watch you’ll see we talk about compression and I mention that I perform what I would consider a “dynamic” test. He suggested doing long term compression and convinced me to add that back in to my arsenal. So I’ll be incorporating that in future reviews but in a different manner than I had done before.

I also was simply unaware that - due to masking - our ability to hear distortions of a loudspeaker are lessened as we increase output. This makes me think that it might be more beneficial to test HD components at lower SPL.... or potentially just not worry about it altogether. (I already provide 86dB and 96dB @ 1m HD components for loudspeaker/transducer tests)

I have to thank Earl again for joining me and helping me (us) understand the various aspects of nonlinear distortion and I appreciated his insight in to the other topics we touched on.
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2009-10-13 2:43 am
Thank you about this video and thank to Earl for his time.

In the first part where harmonic structure of thd was discussed you talked about tubes and it made me thought about this paper ( a bit dated) from Russell O. Hamm from Sear Sound Studio (Tubes versus transistors: is there an audible difference?) where he came to more or less the same conclusion and why tubes still have their place and are still sought after in recording and playback environnement:

[PDF] Tubes Versus Transistors-Is There an Audible Difference | Semantic Scholar

I've found some other interesting coincident points about loudspeaker test with an article from J. D'Appolito which was published in Audio Express in 2008:

Testing Loudspeakers: Which Measurements Matter, Part 1 | audioXpress

Testing Loudspeakers: Which Measurements Matter, Part 2 | audioXpress

The test D'Appolito perform for compression ( part 2) may be of interest to include to your routine too imho:it doesn't reveal thermal compression ( power compression) issues as discussed in the video but non linear behavior related to driver compliance and /or magnetic field distribution issues.
Thanks Erin and Dr.Geddes for a very informative and interesting interview.
Erin, you have improved on the speed of spoken word. I have no complaints
in that sense.

Glad you found it entertaining.

Yes, it is much easier for me to slow down when I'm not worried about trying to cram an hour's worth of information in to a 30 minute video because I know people have a low attention span and won't watch a long video.
Thanks for that.

What I took away from that is that my hearing is probably not normal.
I always heard something I found highly objectionable but others did not seem to be bothered by it, at least not to the degree I am.
Since I came across the Klippel test I know that this something is mostly THD and anything above say 1.5-2% is really driving me nuts so much so that frequently I rather turn the music off than continue listening. Also it gets rapidly worse with increasing volume.
That said masking like the Cocktail Party Effect do not happen for me at all which is why I practically never go to noisy pubs because in environments like that I really struggle to follow conversations while others do not seem to have any problems.
Hi All,

I just found this video interview and thought it contains a lot of helpful information on:
1) the origin of the GedLee metric, and
2) amplifier and speaker distortions, and
3) thermal compression, and more.

So I did a transcript of the first 33 minutes (up to and including) loudspeaker compression. I checked with Erin and he's happy for me to belatedly post it.

The transcript is attached.

Thanks Erin for putting together this very useful interview with Dr Earl Geddes. And thanks to Dr Earl Geddes for being so honest about the need for better ways to measure our loudspeakers.

A compact audio (mp3) of the first 33 minutes is available here.


  • Erins-interview-Earl-Geddes-transcript-ver1.txt
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