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Old 16th March 2013, 10:22 PM   #121
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Default Group delay Problems

Phase Distortion Vs frequency interferes with the requirement that all the signals of different frequencies are required to arrive at the end of the pipe together in time.

Consider these items:

(1) Low frequency speakers are the most corrupted element in the loop. You can research this in the Free Wikipedia Dictionary.

(2) I am not Pushing Audio Cables, but history speaks well on this item.

"Interconnect cables and speaker cable phase corruption"__ according Mr. Bruce Bresson, CEO of MIT / Musical Interface Technology inc, owner of all the important Patents on cables in the world__ states in his first patent: "From 20,000 Hz all the way down to the lowest audio frequency of interest aka, 20 Hz, the magnetic field attending the audio current in the cable conductor Sinks toward the interior of the conductor" which by definition is:increasing inductance inversely proportional to frequency or increasing Group Delay with decreasing frequency.

MIT's first solution was to use a "hollow thin wall flexible pipe" which was executed by wrapping thin wire side by side around a Teflon rope some ten feet long, which he licensed to "Monster Cables inc.

This approach worked quite well down to some 300 Hz, His next patents extended the low frequency group delay with various networks.

Legend has it That "Transparent Audio Inc" added a chunk of Ferrite Magnetic Inductance Properties at the end of the Monster Cable with considerable success.

(3) Vacuum tubes are superior to solid state because there is no impediment to the Emission in the Vacuum, especially tubes with heavy filaments like a Type RCA 26 tube & the type 845 or the Western Electric 300-A & 300-B which have filaments of 11 layers of lamination construction good for 10,000 hours.

(4) Every component in the audio chain damages Group Delay including hook-up tiny conductors in amplifiers. I have a 1989 Sony TV with a tiny 2 inch square Chip 10 watt amplifier in which the chip components are inter-connected with 1/8 inch gold ribbons__ this amplifier offers superb audio sound and measures quite well for phase linearity and phase distortion__ impeccable Group Delay despite the solid state active devices

Last edited by Robert the cat; 16th March 2013 at 10:45 PM.
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Old 21st June 2013, 02:53 AM   #122
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Location: Wappingers Falls, NY
Originally Posted by Aucosticraft View Post
Guys ,Just found a link pls read this, Do read it from first page. I am putting link for 4 th page which is conclusion page.

Thanks for posting the link to this article. Interesting simulation based optimization based on the extrapolation of certain listening tests from 500Hz and scaling with wavelength period. I have played with similar optimizations and wondered how much bass I should give away and how much group delay at 20 Hz is audible in a system with and F3 10 or 20 Hz above that anyway. Good point about the implied THD tradeoff with cone excursion.
However - it would be nice if the following statements (pg 4) were linked to more specifics on the listening tests done: "
In researching this dissertation, I was unable to ascertain a finite limit for acceptable group delay in speaker
design. It appears to be relatively indiscernible, especially when listening to musical content (as opposed to
test tones), and some studies indicate its effects to be partially masked by the reverberant field of the room." Any more info on this?

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Old 6th October 2014, 04:54 PM   #123
jim1961 is offline jim1961  United States
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If low frequencies are dominated by the room response, and the delays associated with it, then when we are talking about GD or EGD, we are in great measure talking about the room at least as much as the speaker, right?

So if we are trying to determine what the good, the bad, and the ugly are in terms of measurement data, we are talking about those measurements taken at the listening position, right?

10 06 14 gd r 2.jpg

Here is what I am measuring. My question is how big an issue the 35-40hz region is in regards to GD and/or EGD. This measurement is taken at the listening position, the right channel driven and measured only with 1/24th oct smoothing.
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