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 Post subject: Some 4001 frequency spectrum analysis
 Post Posted: Wed May 15, 2019 9:30 am 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
Hi guys,
some time ago, in order to try an distill the essence of the 4001 into a test tube, i isolated the basses on a couple of tracks and ran them through a spectrum analyser.

I thought I would share them with you in the attached gifs. The tracks were Smoke on the Water and Highway Star from DP's Machine Head, and Chris Squire's Roundabout.

For Roundabout, you can see the very sharp notch at 750 Hz and a sharp peak at 1200 Hz.

F


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File comment: Roger Glover 4001 on Smoke on the Water, spectrum analysis. Machine Head album. Spectrum analysis.
sotw extended spectrum analysis.gif [95.79 KiB]
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File comment: Roger Glover 4001 on Highway Star, spectrum analysis. Machine Head album. Spectrum analysis
highway star 2.gif [106.19 KiB]
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File comment: Chris Squire 4001 on Roundabout. Isolated Bass. Spectrum Analysis
roundabout.gif [94.89 KiB]
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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Thu May 16, 2019 4:08 am 
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Joined: Sun Oct 08, 2006 6:07 am
Posts: 3829
What I see in common from the charts is a consistent dip somewhere in the 500 to 750 Hz range, although not as pronounced in the other two charts as in the Squire. I would be interested to see a chart from something played by Macca, to see if it has a similar dip, knowing that with flats, there may not be the extension of highs otherwise.


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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Thu May 16, 2019 1:29 pm 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
Below is the Frequency analysis of a few notes from Golden Slumbers off Abbey Road, where he is distinctively using both pickups. The notch appears at 945 Hz and the Peak at 1337 Hz. The notch moves around slightly, and sometimes less pronounced. However, the peak is quite stable.

Compare this to Bathroom Window, in the second extract. If i had to put money on it, he is just using the neck pickup, with the tone wide open.

F.


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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Thu May 16, 2019 2:02 pm 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
Actually, I stand corrected, in some places in In through the Bathroom window, the treble pickup is quite evident. Notch at 850 Hz, Peak at 1204 Hz. I wonder was he switching in and out the treble pickup.


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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Fri May 17, 2019 3:49 am 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
Just looking at Golden Slumbers. The forum doesn't allow mp3's so i've uploaded to dropbox.

https://www.dropbox.com/s/lseigdq7mliin ... s.mp3?dl=0

You have to assume that the peak at 1337 Hz is the advent of the treble pickup. As per the first frequency analysis.

What happens when you roll off the bass from 1337 Hz downwards (i think 16+db per decade), and isolate the treble pickup?? The result, as you can see in the frequency analysis below, is as follows.

https://www.dropbox.com/s/5axd0edaznjlf ... e.mp3?dl=0

Play it back in a loop, sit back, close your eyes and savour the timbre


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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Fri May 17, 2019 4:51 am 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
Isolated bass for Golden Slumbers is

https://www.dropbox.com/s/ywlkrddfvno5z ... s.mp3?dl=0

Frequency spectrum is below. Here, the treble is rolled off from 1000 Hz onwards.

Hopefully, the treble and bass samples are mutually exclusive of each other.

F.


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 Post subject: Re: Some 4001 frequency spectrum analysis
 Post Posted: Sat May 18, 2019 3:08 am 
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Joined: Wed Aug 23, 2006 8:26 pm
Posts: 27
Location: Green and misty Isle
To recap. The single note from Golden Slumbers is

https://www.dropbox.com/s/lseigdq7mliin ... s.mp3?dl=0

The isolated treble pickup is

https://www.dropbox.com/s/5axd0edaznjlf ... e.mp3?dl=0

The isolated bass pickup is

https://www.dropbox.com/s/ywlkrddfvno5z ... s.mp3?dl=0

When we zoom in further to the bass pickup sound, in the attached gif, we can identify the relevant harmonics and a few other artefacts.

The fundamental note that McCartney is playing is G2 (98 Hz), giving rise to harmonics G3, G4 and G5. However, we also see so called "fractional" harmonics .. thirds B4 and B5 and fifths D4, D5, D6. Enriching the tone further are E5,E6, F5,F6 and A5.

I don't know too much about fractional harmonics. Without these interesting sounds, a sound based on pure harmonics would sound like a triangle of ramp wave ......


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