Rockman EQ

[rbc]

I was looking at the Rockman EQ frequencies. They are 62, 125, 250, 500, 700, 1k, 1.4k, 2k, 2.8k, 4k, 8k, and 16k on the model that I looked at. I don't have any idea if they changed over the life of the product. It looks kind of like the frequencies are basically set at an octave (62, 125, 250, 500, 1k, 2k, 4k, 8k, and 16k), with some key frequencies added in between (700, 1.4k, and 2.8k). In comparison, the Pro Bass graphic EQ seems to cover the octaves without anything added in.

Does anyone know or want to speculate why 700, 1.4k, and 2.8k Hz were added to the Rockman EQ? Just curious. They are also an octave apart, just from a different starting frequency.

[GuitarBuilder]

I'm betting that's a question only Tom or Bob can answer. If I had to guess, it was likely the result of trial and error.

[mikegiovannucci]

WOW! I started to think about your question and when I looked at the numbers it was interesting.

The first thing that came to my mind was granularity across the mid band spectrum. More control over your mid range sound. Genius!

Your standard EQ has the flowing spacing between them.
63, 125, 250, 500, 1k, 2k, 4k and 8k

Rockman EQ spacing.
63, 125, 250, 200, 300, 400, 600, 800, 1.2k, 4k, 8k

Mike

[rbc]

62/63, 125, 250, 500, 1k, 2k, 4k, 8k, and 16k Hz frequencies line up to a B note. 700, 1.4k, and 2.8k Hz are aligned with an F note. That's assuming A4 is 440 Hz. Maybe they were chasing specific harmonics of certain notes.

[mikegiovannucci]

I guess what we need to know is if the Rockman EQ was designed with constant Q. If it is constant Q, then you are right, that it would target more of that note frequency. If it's not, then my guess it would be to control the overlapping humps on each side of it. For example 1k and 2k would overlap the more you get them up to + or -12db. The 1.4k would help tame the 1k and 2k a bit. Just my 2 cents anyway.

I also noticed that there are a few dual 15 band SR&D eqs built from Rane ME15s. I am guessing this is a one of a kind eq. Seems like Tom really likes the Rane eqs. I see a lot of ME15s being used in his racks.

Rane has a bunch of white papers on eq design that I was reading today. They have some really great docs.

Figure 5 in this doc shows a great example of what the humps look like on each side of a singal freq. Really cool.

https://www.rane.com/note101.html

Here is a picture from Bob's site showing that SR&D EQ at the top part of the rack in yellow. Betcha Sunburst doesn't have one of these.



Mike

[mikegiovannucci]

This is from Dave A's documents. He touches on a little about the 1.4k

62...Flat
125...between +6 and +9
250...between -6 and -9
500...-12
700...between +6 and +9
1KHz...between +6 and +9
1.4KHz...between -6 and -9
2KHz…between +6 and +9
________________________________

2.8KHz...-12 totally cut
4KHz...-12 totally cut
8KHz...-12 totally cut
16KHz...-12 totally cut

Output slider...between +5 and +10

Notice that the last four sliders are all the way down. This simplifies the EQ by eliminating frequencies that don't make it through the Sustainor's filtering.

The 125Hz slider is one of the most important sliders. This frequency is what will give you a nice UMPH, much like cranking the bass knob on an old Marshall JCM800 head.

The 1KHz is a touchy, but necessary frequency that brings out the upper mids. It's a necessary evil, because if it's too high, this frequency is very shrill sounding.

The 1.4KHz slider is also a necessary evil. Totally cut, it leaves something lacking, but boost it too high and it could kill a mouse!