Observation on micing electric guitar cabinets.

[jm2]

A short time ago, I posted a question about the necessity of recording electric guitar at high SPL (something I had read many times). The responses were in agreement, and several reasons were given as to why a miced guitar amp records better at loud volumes, including the stress of maxed out speakers and tubes.

The explanations were comprehensible, however, another question recently popped into view. How much of the equation is governed by the microphone? Theoretically (and remember, it is just conjecture for the sake of discussion), the microphone under greater stress might be accounting for the benefit of recording at high SPL's, rather than the gear itself.

Further, how could one separate cause and effect when trying to determine where the benefit is really coming from?

[Greener]

"Further, how could one separate cause and effect when trying to determine where the benefit is really coming from?"

By testing and changing variables in small increments.

The high SPL low SPL discussion is an odd one. Alot of good effects come from overdriving amps and speakers.
However you do not need to move air to get a good sound. A very light very small cone driven balls to the wall by a tiny tube amp that's glowing and humming sounds like a tiny little box in the room but shove a mic up in the grill and suddenly it (can) translate into something massive through the monitors. However a massive amp that has ear splitting mids and back melting bass just puts tons of energy into creating mud in the room... You record the mud and on playback the phase cancelation causes holes in the sound and (can) make for a thin translation...

How you arrive at a good tone takes time, no matter who you are. So you have to spend alot of time playing with different amps and different mic choices and positions.

[jm2]

Thanks for the reply. There are three reasons I feel compelled to try to find a way to get good guitar sound from recording at low to moderate levels, although I fully trust what you are saying about micing a small amp, or overdriving, etc.

The first is just sheer caprice. The second is that I want to try to capture the particular sound in the room that I enjoy playing and listening to, which is more modest in level. I am not a great player with the kind of skill or discipline found in studio musicians. It will be easier for me to capture the best musicality I can muster if it is captured without greatly altering what I am hearing (which would not be the case with rigging up a seriously loaded small speaker). Even headphones seem to reduce my ability to play clean and articulate musical ideas the way I want, as it is a disconnect with the instrument.

The third reason is that my early attempts at getting respectable sound from modest volume have been well, respectable, which tells me the louder equals better formula may have a small loophole. I am trying to understand if the loophole exists, and how to best exploit it.

What prompted this particular question about mics, is after loading the mic very close to the speaker, the sound I recorded with modest loudness was quite nice. Granted, my listening skills in the context of recording may be way off, and maybe the sound would not be considered great by an actual engineer, but for the time being, I will have to trust my ear.

So, moving the mic really close to the speaker is going to increase the displacement of the microphone’s diaphram, and again, I am just wondering aloud as to how much of a factor this particular component is. My guess is that it is an important component, and one that I have not seen mentioned when discussing the benefits of high SPL’s when recording.

[Davedog]

Take into cosideration the makeup or construction of a microphone if you will.

The 'diaphram' is in all actuality a very small speaker. In essence only but a very real aspect.

A primer on mic construction will clue you into this aspect and give you a more complete answer to your question.

The short of it is, in most cases where using a mic capable of high spl's, the only thing that really gets distorted is probably the mics preamp circuit.

The diaphram is usually tensioned so high that actual distortion from a 'distorted' movement of this caused by a high spl is unlikely.

[GeckoMusic]

A short time ago, I posted a question about the necessity of recording electric guitar at high SPL (something I had read many times). The responses were in agreement...

Where was that thread? The general consensus on the board here seems to be that lower SPL is better. And that driving a small amp hard as Greener mentioned is generally better than trying to drive a large amp at high SPL.

Playing with headphones is a different experience than playing live. If you continue to practice playing with headphones on your skills when wearing them will improve.

I've never heard the "louder equals better" formula. In my experience louder equals muddy with a combed out high end. Of cource one mans loud may be anothers average level. What dB level are we talking and how big is your room?

If you use a dynamic microphone rated for high SPL, then the distortion of the diaphragm should be minimal. Dynamic microphones do not have active circuitry so they generally do not overload as easily as a condenser. Although you may get some interesting results from putting an LDC touching the grill. To find out what effect the LDC has simply record the same passage with both and LDC and SM57 at the same time and listen to the results.

[jm2]

Well, perhaps there is confusion in term or definition. Even a small amp driven hard will be "loud", at the very close proximity of where a mic would be. I think it is possible for two different speakers to produce identical loudness at the cone surface and yet different loudness out in the field (although I will test this idea shortly). So I must confess that it is me who has made the loudness equals better generalization based on the fact that a little amp will be quite loud very close up.

The room is 13 x 16.5, and fairly dry. I am recording a 2 X 12 cabinet at about 80dB at 3 feet. I am not sure how others would percieve that as far as loudness goes.

[GeckoMusic]

Well, perhaps there is confusion in term or definition. Even a small amp driven hard will be "loud", at the very close proximity of where a mic would be. I think it is possible for two different speakers to produce identical loudness at the cone surface and yet different loudness out in the field (although I will test this idea shortly). So I must confess that it is me who has made the loudness equals better generalization based on the fact that a little amp will be quite loud very close up.

The room is 13 x 16.5, and fairly dry. I am recording a 2 X 12 cabinet at about 80dB at 3 feet. I am not sure how others would perceive that as far as loudness goes.

"Loud" is a pretty straight forward term in itself. Use of the term can be confusing. It roughly defines the sound pressure level. When I hear the term "loud" I think about holding a sound pressure meter in a normal listening position and seeing numbers 90 or above.

I see where you get the "louder = better" now. It might be clearer to say "higher signal = better" Loud is normally what you hear, signal is what the microphone picks up.

You cannot have "two different speakers produce identical loudness at the cone surface and yet different loudness out in the field." Sound level is proportional to one over the distance squared. This assumes you are comparing one speaker to one speaker. If you compare a 1x8 to a 8x8 cabinet you will see that the 8x8 is louder "in the field" than the 1x8 with the same displacement measured at one cone.

The room size, volume and cabinet should be fine if the room is well damped and you keep a dynamic microphone close. You may get a better tone by disconnecting one speaker and keeping the volume in the same place. You may need a load in place of the removed speaker. (Don't try it unless you know what you are doing.)

[jm2]

Thanks for the reply and useful tips. In theory, I agree when you say You cannot have "two different speakers produce identical loudness at the cone surface and yet different loudness out in the field." however, in practise, something is still telling me that a 3" speaker producing 85dB at the closest possible micing distance and a 15" speaker producing 85dB at the same mic distance will produce different loudness readings well out in the field, due to the additional area of energy radiating surface presented by the larger speaker. The 1x8 vs. 8x8 analogy is a good one, and I think the same principle applies, but the conceptual obstacle is merely in thinking of a 15" speaker as a multiple of many 3" speakers.

I am going to test this idea soon, perhaps this evening.

[GeckoMusic]

My discounting of your theory may come from a lack of understanding of what you are trying to prove. Can you clarify your hypothesis?

For starters, what do you mean by "loudness at the cone surface" Do you mean the amount of air displaced by the cone? Or the SPL measured with a meter as close as possible to the cone? Is that the center or the edge? As measured at a distance equal to that of the diameter of the largest cone in order to capture most all of the air moved by the speaker?

[jm2]

Hmmm.. It will take me a bit of thought to clarify what I think my hypotheses are (post to follow), but by loudness, I am thinking of the measurement given by a SPL meter as close to the loudest region of a given speaker.

But briefly, I am merely thinking that two different speakers could produce identical SPL at the closest and loudest possible point of measurement and yet produce different loudness (or SPL measurement) at greater distances. I have somewhat lost track of how that fit in with my initial question, but again I will think about it for a time.