Slightly OT: Guitar Tone Mythbusting (video)

[jan-sandahl]

This guy (Jim Lill) made a great, fun and revealing series of pretty scientific electric guitars and amp/cab testing videos (six, I think). We are led via marketing and perception bias et c to a high degree to believe in differences where there are hardly any real ones.

The situation is comparable in my view to the plugin world of amp and cab sims. I bought a few crap, VERY limited amps (in comparison) before I found a home in the open ended world of Melda TurboAmp/MCab & Guitar Architect - Edit mode preferably.

Anyway, I found the series enjoyable and enlightening, and see a link between it and the work of Vojtech/Melda, so I felt like sharing it here.

[steve2KVR]

+1

[BennyG]

Really interesting, thanks for posting!

[Hexspa]

One flaw with his methodology for amp cabinet size is that he moved the mic in his room. This is particularly problematic at low frequencies where modal behavior dominates. The speaker has to be in the same location too so he'd need to have built a custom adjustable stand. I appreciate his work but it's not air tight science; not that you said so. EDIT: you said "scientific" but, his methods have flaws.

[jan-sandahl]

"Pretty scientific". No, itś not perfect...

[sparella]

This guy (Jim Lill) made a great, fun and revealing series of pretty scientific electric guitars and amp/cab testing videos (six, I think). We are led via marketing and perception bias et c to a high degree to believe in differences where there are hardly any real ones.

The situation is comparable in my view to the plugin world of amp and cab sims. I bought a few crap, VERY limited amps (in comparison) before I found a home in the open ended world of Melda TurboAmp/MCab & Guitar Architect - Edit mode preferably.

Anyway, I found the series enjoyable and enlightening, and see a link between it and the work of Vojtech/Melda, so I felt like sharing it here.

I was subbed to Jim Lill's channel and immediately noticed the parallel when his amp video came out. It was a nice confirmation of the legitimacy of the methodology I had been using to design in MTurboAmp.

[sparella]

One flaw with his methodology for amp cabinet size is that he moved the mic in his room. This is particularly problematic at low frequencies where modal behavior dominates. The speaker has to be in the same location too so he'd need to have built a custom adjustable stand. I appreciate his work but it's not air tight science; not that you said so. EDIT: you said "scientific" but, his methods have flaws.

Do you find modes to be a significant issue when close micing cabs? I'm curious because I record everything direct these days and use MCabinet + IRs, so it doesn't ever come up.

[Hexspa]

One flaw with his methodology for amp cabinet size is that he moved the mic in his room. This is particularly problematic at low frequencies where modal behavior dominates. The speaker has to be in the same location too so he'd need to have built a custom adjustable stand. I appreciate his work but it's not air tight science; not that you said so. EDIT: you said "scientific" but, his methods have flaws.

Do you find modes to be a significant issue when close micing cabs? I'm curious because I record everything direct these days and use MCabinet + IRs, so it doesn't ever come up.

My expertise is not as a recording engineer. What knowledge I have comes from setting up my monitoring and listening environment. That said, the principles should apply to both. The fundamentals are that you will get a strong cancellation at 1/4 wavelength which relates to how far a source is from a boundary known as speaker-boundary interference response (SBIR). The closer a mic is to the source, the lower the ratio of ambient sound but I don't think that applies to bass because of the modal dominance. In other words, if the mic and speaker are close but in a pressure null of a given frequency then, as far as I know, you will have less of that frequency in your recording.

Now, how much of this applies to guitar (low E standard tuning is about 82.5Hz) depends on where the cabinet is located. Actually, the cutoff of a guitar is similar to that of a bass-managed satellite loudspeaker (~80Hz) and Genelec recommends a very near placement (pushing the interference higher into the spectrum) or further than 1.1m (pushing the cancellation below 80Hz and thus filtered out). You can probably treat guitar cabinets the same way. Where there are boundaries (within some absurd distance), cancellation will always occur but, with near-boundary placement (within 60cm) and sufficient absorption (above 143Hz is not too hard to absorb) or far placement (below source cutoff), you can minimize its impact. Bear in mind that a guitar cabinet might resonate below 80Hz and you may or may not want to preserve that bandwidth. However, with a little sleuthing, you could play around with where the cancellation is and, say, help the kick drum sit better by recording the guitars in a null where the kick drum fundamental is.

I will note that small rectangular rooms have three axial modes so you can balance your positioning so you don't end up with a three-way null (which will probably be audible). The easy fix is to ensure you're not equidistant to two or more boundaries. Peaks are less problematic because you can EQ them down whereas nulls don't give you anything to boost. Finally, having your source near a boundary will introduce what's known as 'room gain' which also increases the bass. Every nearby boundary adds to the bass. On the floor in the middle of the desert is known as half space. On the floor near a wall is quarter space and near two walls is eighth space (all as though you're dividing up a sphere in free space (you can think of it as outer space or really high in the sky)).

So yeah, it probably matters but it's arguably not as important as the performance you're trying to capture. Having said all that, if your IR was captured in a room and I'm not talking out my ear then the IR will have this embedded into it unless it's totally synthetic like MCabinet. Even then maybe it matters since there's a 'room' function in that plugin (I haven't used it much) so it depends to what extent that room is modelled.