Thank you for this. Do you have any recommendation for finding the center frequency of the EQ when not listed on the amp, in the manual, or anywhere on the web?
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Drop1s EQ tutorial
- Thread starter Drop1
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Won’t a LPF be used to tame back high end, since frequencies above the set point be eliminated (not passed)?
Hpf is a great tool on any sound system.
Yes actually. 2 ways. Both involve work.
First is to plug straight into a computer or analyzer , boost the knobs one at a time and look at the response.
The second is to take your cab outside away from any walls. Boost heavily and play down your neck until you find the loudest note. Your center frequncy will be close to that notes frequency.
You can try the second inside but the room acoustics may lie to you.
I think you make some good points, but let's not forget that EQ strategies tend to be situational. I think what @Drop1 wrote is pretty informative, but it's not universally applicable. So there is more to learn and probably things that none of us understand fully.
I agree that if your sound is boomy all the time, chances are it's your rig. But boomy sound is often a consequence of poor acoustics. If the room has a long decay time, the frequency range we perceive as boomy tends to build up and form a diffuse field. EQ can help a little with this by reducing the amount of energy you put into exciting the diffuse field, but IMHO when you do this you are really dealing with masking and frequency slotting. In essence you reduce the boomy frequencies which tend to mask other frequencies. By doing this you let the rest of the bandwidth of the bass's sound reveal itself. So in essence your compromising the low end of your direct sound because it is overstimulating the room. Too some degree I think this approach could be used to some degree in most performance spaces, but the tone controls of most amps are not flexible enough to accurately target problem frequencies.
As far as how careful/subtle you need to be with EQ inputs. Some consideration should be given to whether you rig is a personal monitor or driving the entire house. If it's a personal monitor and run at a low level that does not impact the main mix, then you can EQ pretty aggressively and it won't have any negative impact.
If your amp is driving the house, then IMHO it's not so much the degree of EQ you use, but the average of the results. In general when my amp is pushing the room, it's EQ'ed for the room and not for my personal taste on stage, and I rarely enjoy the resultant sound or volume.
Nodes and antinodes are locational and should generally be ignored if you are EQ'ing a bass amp to fill an entire room. I don't believe you can actually correct for antinodes with EQ anyway. There may be a few nodes that are so obnoxious that they should be addressed, but not without considering how much degradation occurs to the rest of the room. Often when you do address nodes, you strike a reasonable compromise.
I think if you look at these ideas you see that there is a distinction between EQ'ing your direct tone and EQ'ing to compensate for acoustic problems. I use sort of a Ying and Yang approach on this. I start with the goal of EQ'ing for tone, and then make concessions that are mandated by poor acoustics. I personally think your tone and the effects of the diffuse field and other acoustics related problems are different things, but in the context of a mix they must be considered together. The sound combines in our ears, so conceptually you could argue that there is no meaningful difference, but I think it is useful to think of the different things that are going on and how you are trying to deal with resultant problems. I guess it really comes down to whether you take a Micro or Macro view of the subject.
As a pro audio tech, I found that once the mic channels and system EQ was dialed in I could often go to several venues and only need to make minor changes, providing the venues had decent acoustic with no severe acoustic flaws. Usually indoors I found it necessary to use quite a bit of broadband cut in the 200-400hz range or the mix sounded like a boomy mess.
The most significant change from gig to gig involved dealing with feedback suppression. You pretty much have to ring out and notch a system every-time you set it up. Note that this involves using EQ to dial back nodes that force the system into feedback. In this case tuning out the nodes is appropriate and greatly improves sound throughout the house.
Whenever we setup in a hall with really bad acoustics, I usually had to do some pretty major additional carving on both the system EQ and also channel EQ. The amount and type of corrections could vary significantly from room to room...often you wind up chasing your tail as EQ is not really the proper tool to address this sort of problem
Another exception is the system EQ for outdoor gigs is drastically different because there is no diffuse field. Under this circumstance you EQ'ing primarily your direct sound with the channel strips. Outdoors it's generally necessary to eliminate the 200-400 dip that is typically needed indoors or the mix will sound scooped and hollow.
I think many audio techs will argue that the best approach is to dial in the system nominally flat, make some minor changes to the system EQ for taste, ring the system for feedback, and then use the channel EQs for everything else.
This was a good read. While I don't agree with everything written, I do a lot of the same things you described when tracking and mixing. Much appreciated, I really enjoyed reading this.
Thanks for posting this. Looks to be quite useful.
I’ll admit I was a little annoyed with how this was presented in the other thread. My bad.
I’ll admit I was a little annoyed with how this was presented in the other thread. My bad.
I think you are out by about an octave...
Otherwise not a bad tutorial
Fair point - it may be more useful to use the first overtone instead of the fundamental- perhaps a quick correction in your tutorial so as not to confuse people?
Otherwise not a bad tutorial
Fair point - it may be more useful to use the first overtone instead of the fundamental- perhaps a quick correction in your tutorial so as not to confuse people?
I actually do something similar. When I first got an amp with a sweepable semi-parametric control I also learned how to dial in a room. I now have an amp with three sweepable semi-parametric controls. It was actually easier to dial in a room with the one sweepable control. Here's how I did it:
This particular control allowed you to pick out any frequency center between 40Hz and 10KHz. First thing I would do is turn the boost/cut control up to 3 o'clock. This particular boost/cut control was a +/- 15db. So turn it to 3 o'clock would boost the heck out of any frequency you chose. I would have a buddy (often the drummer who I helped carry in and out his gear) slowly turn the frequency knob while I played a run that covered all 4 strings.
When he hit a frequency that was being boosted by the room, it would really jump out at you. I'd have him make a note of that frequency and then continue on. Usually there was only one frequency that jumped out and I would just cut that frequency a little bit to get everything back to "neutral". Sometimes you'd hear a frequency drop out when you were doing this and that told you that you needed to boost that frequency slightly.
With my amp, 2-clicks on any EQ control makes a noticeable difference in sound. Usually 2-clicks boost or cut would do it. Occasionally I'd have to move it 3-clicks.
And BOOM! The room was dialed in!
Now I have to do that with 3 knobs and can cover from 30Hz up to 12KHz. But the process is the same and I don't have to turn the boost/cut on each of those as slowly because each one handles an octave range of frequencies instead of all of them.
Personally, using my Eden amp, at this point I will add a little boost at ~250Hz on either my first or second semi-parametric control (controls overlap slightly) while keeping everything else flat except for the EQ adjustment I made for the room. With my Jazz, that produces the sound I like and I can consistently get that sound as long as I dial in the room where I'm playing.
By the way the difference on a semi-parametric vs. a parametric control is that the semi one has a gentler boost slope up to the frequency center - sort of a "^" shape. It's actually a bit steeper than that caret, but you get the idea. On the other hand, a true parametric is almost a needle shape up to that frequency.
This particular control allowed you to pick out any frequency center between 40Hz and 10KHz. First thing I would do is turn the boost/cut control up to 3 o'clock. This particular boost/cut control was a +/- 15db. So turn it to 3 o'clock would boost the heck out of any frequency you chose. I would have a buddy (often the drummer who I helped carry in and out his gear) slowly turn the frequency knob while I played a run that covered all 4 strings.
When he hit a frequency that was being boosted by the room, it would really jump out at you. I'd have him make a note of that frequency and then continue on. Usually there was only one frequency that jumped out and I would just cut that frequency a little bit to get everything back to "neutral". Sometimes you'd hear a frequency drop out when you were doing this and that told you that you needed to boost that frequency slightly.
With my amp, 2-clicks on any EQ control makes a noticeable difference in sound. Usually 2-clicks boost or cut would do it. Occasionally I'd have to move it 3-clicks.
And BOOM! The room was dialed in!
Now I have to do that with 3 knobs and can cover from 30Hz up to 12KHz. But the process is the same and I don't have to turn the boost/cut on each of those as slowly because each one handles an octave range of frequencies instead of all of them.
Personally, using my Eden amp, at this point I will add a little boost at ~250Hz on either my first or second semi-parametric control (controls overlap slightly) while keeping everything else flat except for the EQ adjustment I made for the room. With my Jazz, that produces the sound I like and I can consistently get that sound as long as I dial in the room where I'm playing.
By the way the difference on a semi-parametric vs. a parametric control is that the semi one has a gentler boost slope up to the frequency center - sort of a "^" shape. It's actually a bit steeper than that caret, but you get the idea. On the other hand, a true parametric is almost a needle shape up to that frequency.
Thank you again. Could I use a Frequency Analyzer app on a phone to more or less do the same thing as plugging into a computer?
You can try, I've found phone apps arent exactly reliable. They give you a general idea but it may work for what you are doing.
The Mesa Subway WD-800 does have three semi-parametric bands, in addition to variable HPF, bass, "passive mid" (like a voicing knob), and treble controls. Yeah, that's more capability than most bass amps have.
I've used this software as a low cost frequency analyzer to find actual center frequencies of EQ knob positions in a couple of Genz Benz amps I own: TrueRTA Audio Spectrum Analyzer Software -- it has a sweep signal generator that you can use to do a frequency response plot which shows the actual frequency at a given knob position.
Pull up the Mesa Subway thread on here. IIRC, there are some posts making comparisons to the Genz.
Way to go, @Drop1. I like yer tenacity about all this. Some people would've tucked tail, or said to hell with it, what with all ridiculous negativity being flung around. Nice post, I'm gonna try it.
A big thanks from me also. Where were you years ago before IEM? I have nothing on stage any more. Just me and my bass. Kindy lonely sometimes without my big rig.
