Gedlee on distortion

[Face]

Re: Gedlee on distortion

https://www.psychologytoday.com/blog/look-it-way/200906/how-start-cult

[andy19191]

Re: Gedlee on distortion

Any thoughts? Should we ignore distortion graphs etc?

Distortion defines the operating range of drivers and speakers. How loud, how low and loud, how high and loud. Fundamental stuff for sizing drivers to handle musical peaks cleanly. This aspect of distortion seems to get too little attention when the performance of speakers is considered. I suspect it may be a factor in some grossly undersized speakers being considered high fidelity by some.

The commonly shown distortion spectra at various power levels gives an indication of the linearity of the speakers in a similar way as other home audio components like amplifiers, CD players, etc... The levels are usually higher and therefore probably a bit more important to know about. One can also read to some extent engineering information from them about what is probably going on in terms of cone motion, motor construction and such. Useful stuff.

The complaint that the THD, IMD or whatever plots are not a direct measure of how intrusive the distortion is to the ear is correct but that they therefore should not be considered or shown is just daft. No doubt some people will interpret the plots as a direct measure of how nice or nasty the speakers sound but this is a problem with the people and not the plots.

[dlr]

Re: Gedlee on distortion

In this thread here: http://www.diyaudio.com/forums/multi-way/249310-nearfield-farfield-curve-splicing.html

It's a discussion with Dave Thomas, Andrew Jones, Geddes, and several names you will recognize from here. We are discussing my paper on using the "Blender" spreadsheet that Charlie and I made. The discussion a few pages in moves to diffraction where Geddes states that he only uses a spherical model in simulations. I make the point that his slope will be off if it doesn't include the first peak compared to the spherical diffraction. This is probably around page 9 or so. I haven't dug into it for a while.

Thanks Jeff. I read through it, but quickly, so I may have misread some of it. It appears to me that he's not dismissing the peak, though he does say he only uses a spherical model. My reading of his responses is that he's primarily interested in the low end well below the peak which may be accurate enough for his particular applications. He uses a big woofer and waveguide compression tweeter crossed very low. The waveguide probably largely eliminates the diffraction peaking from the baffle while the low range used for the woofers are probably used where the baffle diffraction is almost done moving into 4-pi. Given the wavelength and small baffle size relative to that, he's probably on fairly solid ground. If not, at those frequencies, the room and positioning create far wider variations in response at the listening position.

His key comment is this:

I still believe that those peaks are out of band. Could you plot both on the same plot using something more comparable like a sphere of the same volume as the enclosure with a driver size more like a real driver. I am willing to bet that below 500 Hz the two will not differ by more than one dB. In my work I fit between 200-300 Hz, sometimes as high as 400 Hz, never 500 Hz.

Then there are jcandy's supplied graphs that tend to support Geddes' position:

Here is a comparison with a cube of the same volume as the sphere. Specifically, a cube of side L=48cm. This is a good check of the very-low-frequency behaviour of any diffraction algorithm. Anyhow, we approach a 1dB error at about 250Hz. So, your claim about the 1dB deviation at 500Hz would certainly hold for a cube of side L=48/2=24cm.

I won't comment on his position about room gain. That's more semantics than substance, I think, and he can be dogmatic. But then, so can I. ;)

I've never heard his systems, so I can't comment on the sound.

dlr

[skatz]

Re: Gedlee on distortion

I remember Earl Geddes from a forum I used to be on, maybe the Bass List? Anyway he repeatedly got his feathers ruffled by posters being critical of something he claimed. He eventually quit the forum in anger. It seems there are thin skinned narcissists, and thick skinned. He was in the former camp.

[blur]

Re: Gedlee on distortion

I remember Earl Geddes from a forum I used to be on, maybe the Bass List? Anyway he repeatedly got his feathers ruffled by posters being critical of something he claimed. He eventually quit the forum in anger. It seems there are thin skinned narcissists, and thick skinned. He was in the former camp.

I think we should keep the personal comments to a minimum, especially when they aren't that high of opinions.

Jeff B: You've been a little cranky lately, is everything OK at home?

[Jeff B.]

Re: Gedlee on distortion

I think we should keep the personal comments to a minimum, especially when they aren't that high of opinions.

Jeff B: You've been a little cranky lately, is everything OK at home?

I don't see where I have been cranky at all. I haven't felt cranky, and I haven't responded angrily in a long time, so I'm not sure what this is in reference to. I think my comments above were fair, having read a lot of posts by Dr. Geddes. He is very smart and knowledgeable, and at times he is a bit difficult and cryptic too. Unless you are referring to some other post, still I don't see where I have been cranky sounding.

[hongrn]

Re: Gedlee on distortion

Jeff B: You've been a little cranky lately, is everything OK at home?

Quoting you: "I think we should keep the personal comments to a minimum".

[Jeff B.]

Re: Gedlee on distortion

Quoting you: "I think we should keep the personal comments to a minimum".

Yes, there was some curious irony in his post. I guess it depends on who's making the personal comments. ;)

[blur]

Re: Gedlee on distortion

Yes, there was some curious irony in his post. I guess it depends on who's making the personal comments. ;)

I do have a high opinion of Jeff B and I was honestly concerned.

[Jeff B.]

Re: Gedlee on distortion

I do have a high opinion of Jeff B and I was honestly concerned.

Well, I do need a kidney, and soon, but I don't think anyone would say it's making me cranky. In written posts it's easy to infer things that may not be there.

[philthien]

Re: Gedlee on distortion

Well, I do need a kidney, and soon, but I don't think anyone would say it's making me cranky. In written posts it's easy to infer things that may not be there.

Let's type-match Blur.

[blur]

Re: Gedlee on distortion

Let's type-match Blur.

Sorry my organs are ear-marked for good people.

[Jeff B.]

Re: Gedlee on distortion

Sorry my organs are ear-marked for good people.

Well, I'm not asking for a kidney, but I'll assume you didn't mean that as cold as it seemed to come across.

[craigk]

Re: Gedlee on distortion

Sorry my organs are ear-marked for good people.

Wow, really ? Joking or not what a thing to type. I know what to say, I am just not aloud to on this forum. I will say your a poor excuse for a human being and leave it at that.

[Pete Basel]

Re: Gedlee on distortion

Sorry my organs are ear-marked for good people.

I'll take that to say when you are dead because otherwise it is a pretty offensive comment.