Gedlee on distortion

[djg]

Good to know.

[MI Pro]

Hello Everyone,

I have posted a Group Buy (GB) announcement for audio analyzer software that does the following:

- Traditional, old fashioned, and non-relevant (IMO) THD and IMD, but far more importantly, the vastly more modern and relevant non-coherent distortion (NCD) as well as the Dr. Earl Geddes "GedLee Metric (Gm distortion).

- If you own an RTX6001 audio analyzer this software has a custom API that controls the RTX's internal attenuators and gains to allow for true autoranging and autoscaling (which is a HUGE deal).

- Even if you don't own an RTX6001 and instead use a soundcard type of approach, the new distortion and other features of this software will prove to be very useful to many IMO.

You can read more about this GB audio analyzer software at: https://bit.ly/2LdMtB9

[Deward Hastings]

Re: Gedlee on distortion

I usually associate THD and IMD with amplifiers and other electronics and multi-tone with
speakers. But certainly if all you have is IMD then it is what should be used with speakers.

It used to be that two-tone IM tests were done at 60 and 6k Hz (later 60 and 7K), and it was the 60 Hz. signal that was pushing the amplifier or speaker into non-linearity. Those tests tracked pretty uniformly with simple harmonic distortion measurement of the 60 Hz. tone. Of course with multi-way speakers that IM test is essentially null . . . and swept two-tone test devices were not readily available.

Someday I'll try this around the upper resonance
of a metal dome tweeter.

It is always interesting (not just with domes) to do distortion testing with a separate tone sitting on/exciting a cone or dome breakup/resonance. It can dramatically increase measured distortion over the (theoretically) not-broken-up (useful) part of the driver's range to have the cone flexing out of control at some resonance . . .

[Pete Basel]

Re: Gedlee on distortion

An old timer told me of a situation where some of the early stereo demultipexers for FM
would produce "birdie" tones if you applied something like 18 and 18.1 KHz. The birdies
being at the 1 KHz difference frequency. Someday I'll try this around the upper resonance
of a metal dome tweeter.

About my other post, I was also trying to point out that the distortion issue seems to make
more sense in the time domain as compared to the frequency domain at least for simple
examples. Speakers are complex with the non-linearity being different vs. frequency and
this complicates things.

[fpitas]

Re: Gedlee on distortion

I agree, they both usually work for electronics or other devices that are not band limited.
Speakers are always band limited, so they are just confirming what I wrote. I've said for
years that the multi-tone tests are best:

http://www.libinst.com/close3rd.htm

I usually associate THD and IMD with amplifiers and other electronics and multi-tone with
speakers. But certainly if all you have is IMD then it is what should be used.

Yes, now that I re-read what you wrote, I agree.

[Pete Basel]

Re: Gedlee on distortion

Normally, for a semiconductor device etc. I'd agree; but the Klippel paper above in post #144 suggests that THD is not so easily connected with IMD performance for a speaker driver, for example:

Contrary to the THD response in Fig. 9, the nonlinear force factor Bl(x) and the inductance L(x) THD generate significant intermodulation distortion at higher frequencies as illustrated in Fig. 10.
Thus, harmonic distortion measurements using a single test tone are not sufficient for assessing loudspeakers comprehensively and predicting the large signal performance for complex stimuli like music.

I agree, they both usually work for electronics or other devices that are not band limited.
Speakers are always band limited, so they are just confirming what I wrote. I've said for
years that the multi-tone tests are best:

http://www.libinst.com/close3rd.htm

I usually associate THD and IMD with amplifiers and other electronics and multi-tone with
speakers. But certainly if all you have is IMD then it is what should be used with speakers.

[fpitas]

Re: Gedlee on distortion

The thing is, and perhaps you are aware of this, if you consider the fundamental cause
of distortion it is the Vin(t)/Vout(t) for amps, or Vin(t)/Uout(t) for speakers being other
than a straight line (linear), or being non-linear. A harmonic distortion test _or_ an IMD
test reveals the frequency domain distortion resulting from such a non-linearity, either
one will do it if the system has wide bandwidth. You can even "back out" the shape of
the non-linearity of the transfer function if you have the time domain signal (LAUD does
this). The advantage of IMD is the case where you have a bandlimited system (all real
systems are but some have 10X or more beyond the intended use bandwidth) that hides
the higher harmonics of a fundamental test tone as it gets closer to the top of the band.
IMD testing produces sum and difference products that fall within the passband and thus
are a better test for such systems. The cone in a speaker makes it a band limited system.
I've pointed this out before ...

Normally, for a semiconductor device etc. I'd agree; but the Klippel paper above in post #144 suggests that THD is not so easily connected with IMD performance for a speaker driver, for example:

Contrary to the THD response in Fig. 9, the nonlinear force factor Bl(x) and the inductance L(x) THD generate significant intermodulation distortion at higher frequencies as illustrated in Fig. 10.
Thus, harmonic distortion measurements using a single test tone are not sufficient for assessing loudspeakers comprehensively and predicting the large signal performance for complex stimuli like music.

[Pete Basel]

Re: Gedlee on distortion

At the risk of inciting flames, it seems we can all agree that intermodulation performance is a much better predictor of audible differences than THD alone.

The thing is, and perhaps you are aware of this, if you consider the fundamental cause
of distortion it is the Vin(t)/Vout(t) for amps, or Vin(t)/Uout(t) for speakers being other
than a straight line (linear), or being non-linear. A harmonic distortion test _or_ an IMD
test reveals the frequency domain distortion resulting from such a non-linearity, either
one will do it if the system has wide bandwidth. You can even "back out" the shape of
the non-linearity of the transfer function if you have the time domain signal (LAUD does
this). The advantage of IMD is the case where you have a bandlimited system (all real
systems are but some have 10X or more beyond the intended use bandwidth) that hides
the higher harmonics of a fundamental test tone as it gets closer to the top of the band.
IMD testing produces sum and difference products that fall within the passband and thus
are a better test for such systems. The cone in a speaker makes it a band limited system.
I've pointed this out before ...

[craigk]

Re: Gedlee on distortion

For a start there is a difference of several orders of magnitude. You have to work at it (or have VERY bad cable) to see cable effect at all (and I obviously disagree with Risch about the importance, and even the meaning, of those measurements).

got it. thanx.

[mattsk8]

Re: Gedlee on distortion

I think the intimates have a little more life. In my little 13X13 room and sitting in the sweet spot approach the mids and highs of a good electrostatic. The Vifa's measured and sounded very good though. It's there in the link I provided. I'm probably going to put them up for sale in the PE classified in a bit.

I actually have a build with the XT25 now. Saying the Mundorf gives yours "a little more life" is all I needed to hear and that's exactly the way I remembered them sounding . Which again, that's tough to do when they were competing against that XT25!

AMT
type drivers were patented by Dr. Oskar Heil in the early 70's . ESS I believe was the first company to use it in a commercial product, the ESS
AMT that PE sells is pretty much the same design from the 70's, of which I still use. Oskar Heil was a very busy guy with multiple patents on
all types of technology.

Thanks. I'll ask where the guy who said Mundorf invented them to me heard it.

[Squidspeak]

Re: Gedlee on distortion

lol! "These don't sound quite the way I remember them sounding" :p



I know there are plenty of options, but I'm pretty picky and the only AMTs I've heard that had everything and still sounded natural were the Mundorfs; I was told they invented the AMT (not sure if that's true?). From what I remember, they had amazing clarity without sounding too thin, and they still had great body everywhere while maintaining that glow I look for in a tweeter. From what I've heard in a lot of tweeters, you either get great body but sacrifice the glow and distinction, or you get great distinction but they tend to be a tad thin; those seem to give everything and sacrifice nothing. But, my opinion is from a brief listen, so I'd love to spend more time listening. What are your impressions on how they sound?

As far as cost goes; it isn't as much about whether the cost is an issue, it's more about whether it's the best choice when I'm going for the ultimate speaker if that makes sense. If or when I do it, I don't want regrets, so which one and where it's implemented is definitely key ;).

AMT
type drivers were patented by Dr. Oskar Heil in the early 70's . ESS I believe was the first company to use it in a commercial product, the ESS
AMT that PE sells is pretty much the same design from the 70's, of which I still use. Oskar Heil was a very busy guy with multiple patents on
all types of technology.

[carlspeak]

Re: Gedlee on distortion

*Warning* Thread deralement



Looking at your links I just saw that you replaced the XT25 with those Mundorfs, and IMO beating that XT25 in terms of SQ is a pretty tall order. I love the XT25, the only area I would complain (and this is a stretch) is that it has a kind of "fuzz" in the upper frequencies, other than that it's nearly perfect. In your opinion, how do those Mundorfs compare to the XT?

I think the intimates have a little more life. In my little 13X13 room and sitting in the sweet spot approach the mids and highs of a good electrostatic. The Vifa's measured and sounded very good though. It's there in the link I provided. I'm probably going to put them up for sale in the PE classified in a bit.

[mattsk8]

Re: Gedlee on distortion

*Warning* Thread deralement

Hey, don't worry about regrets. Just go for it. Look at my signature line. 3 iterations of the Intimates before I was satisfied.

Looking at your links I just saw that you replaced the XT25 with those Mundorfs, and IMO beating that XT25 in terms of SQ is a pretty tall order. I love the XT25, the only area I would complain (and this is a stretch) is that it has a kind of "fuzz" in the upper frequencies, other than that it's nearly perfect. In your opinion, how do those Mundorfs compare to the XT?

[SpeakerScott]

Re: Gedlee on distortion

Geddes is a smart guy with a lot of knowledge in this field, and a lot of good information on acoustics. He is also quite prone to playing semantics games and spinning information to precisely fit his "highly acclaimed Gedlee loudspeakers". When he is wrong, don't expect an admission, which is just silly. (I was in a discussion with him on another forum on modeling diffraction and he was just wrong about the importance of modeling the first baffle peak in a simulation, which his model leaves out. The rest of us moved on.)

Regarding his comments on distortion; I don't know if he is just being very precise and narrow in his statement (but he doesn't really infer this), if he's just mistaken in his views, or if he is purposely spinning information to suit his needs at the expense of a larger truth. Whatever it may be, he knows exactly how he wants his comments to be interpreted.

As for me, after taking lots of distortion measurements on a range of different drivers, and then playing and listening to these drivers under different conditions, I am sufficiently satisfied that higher distortion components produce easily audible effects and I can hear very quickly what it is and what it sounds like. Consequently, very low distortion drivers actually do sound better in a number of ways to me, but it does depend on drive level and where that audibility enters the picture for that particular driver and crossover combination. Still, for some drivers, this threshold is quite low. I am satisfied enough based on my own testing that it wouldn't really matter to me if someone else stated something otherwise.

Jeff B.

My interactions with him have been very similar. We had quite the discussion over my DIY Synergy horns. His take was that it can't possibly sound good. I still don't know if he's heard a quality Synergy horn (real or DIY) or has any interest in having his ideas/models challenged. I hope I'm wrong, as a researcher you *always* want to find the flaws in your theories.

Scott

[carlspeak]

Re: Gedlee on distortion

lol! "These don't sound quite the way I remember them sounding" :p



I know there are plenty of options, but I'm pretty picky and the only AMTs I've heard that had everything and still sounded natural were the Mundorfs; I was told they invented the AMT (not sure if that's true?). From what I remember, they had amazing clarity without sounding too thin, and they still had great body everywhere while maintaining that glow I look for in a tweeter. From what I've heard in a lot of tweeters, you either get great body but sacrifice the glow and distinction, or you get great distinction but they tend to be a tad thin; those seem to give everything and sacrifice nothing. But, my opinion is from a brief listen, so I'd love to spend more time listening. What are your impressions on how they sound?

As far as cost goes; it isn't as much about whether the cost is an issue, it's more about whether it's the best choice when I'm going for the ultimate speaker if that makes sense. If or when I do it, I don't want regrets, so which one and where it's implemented is definitely key ;).

Hey, don't worry about regrets. Just go for it. Look at my signature line. 3 iterations of the Intimates before I was satisfied.