disclaimer: I know nothing about recording apart from pushing the record button and watching that the VU meters don't get into the red too much.
back to the topic:
Whether it has been while listening to my own system or to any other, I've noticed one thing about the (commercially) recorded sound of trumpets in the context of a 'big jazz band' performance. The recordings tend to lack the dynamic range, tonality and texture of the original performance as experienced live at the event.
Whether it be a seat at a Buddy Rich concert, or a local college 'stage band', recordings I've heard never impart the actual power of attack that is felt at the live event.
Picture the Maxel tape commercial with the guy sitting in the chair. Like in a wind tunnel. The tie. The hair. The clothing. The martini. The lampshade. They are all being blown away by a hurricane gust of acoustic energy. The live event isn't quite that dramatic, but you feel as if it might be. Such is the power of the brass wind instruments when unleashed at full levels.
I've always been disappointed that no recordings of any such events can relate the pure excitement of them.
I chose to post this query to the microphone forum because I've a hunch, intuition perhaps, that the limitation may occur at the microphone. Is there a microphone that has enough, uh, room... to input the entire loudness range of massed trumpets without distorting?
-Steve
Hi Steve,
Well, here was I thinking that everbody had fallen asleep! Sorry for the delay!
Generally speaking, your intuition regarding the microphone is almost completely correct.
Regarding the question of capturing trumpets or brass in general, the most interesting thing is that these instruments put out a staggering SPL, and they can do it constantly over time!
I would guess that most people around Jonathan's place know of the concept of compression loaded drivers in horns, in the case of the trumpet this is more or less what we are taking about - very high efficiency & very high air pressure.
I would guess that the air in the trumpet at high volume is driven into non-linearity, which might account for the harmonic structure to a certain extent.
Not only that, but the trumpet puts much of its energy into a rather directional beam (often directed at the audience), which loses less energy per metre than does a direct-radiating violin for example.
Single trumpets have been measured to put out something like 115dB RMS (average) and most likely can exceed that quite significantly in peak terms.
Symphonic orchestras have been measured with peaks of nearly 140dB SPL and this is a serious problem for microphones AND speakers.
Regarding microphones, the majority of popular condenser microphones will be working around 10-30% distortion with these peaks, let alone the speakers.
Since 99% of orchestral recordings were made with these mics, this is the kind of distortion figure typical to the recordings you hear (ie. 10% or worse on peaks) - not including the distortion of the mic-amps involved or even tape machines/etc.
Some ribbon & dynamic mics do better, as well as the very high SPL measurement microphones, but none of these are practical for recording orchestral music so are not used.
Looking at the specifications for microphones this distortion performance might seem unlikely. However, almost all microphone measurements published do not include measurements of mechanical distortion (!).
The 'THD' figures published in 99% of cases are only measured in the electronics following the capsule, which figures are far lower than the distortion in capsule itself.
I have measured some of the popular orchestral mics with 10% mechanical distortion at 130dB (ie. orchestra peaks) and my own acoustic-loaded mics are designed & measured for <0.1% mechanical distortion at the same SPL.
In practice, the massive distortion of the average mic is heard as compression (unless the acoustic capacity of the mic is exceeded and the diaphragm actually reaches its excursion limit, which is very dramatic distortion).
In some cases, well designed horn-loaded speakers can have lower distortion than the mics in question, and given differences in listening SPL VS performance SPL, it is quite likely to occur.
This is one of the reasons it can be dangerous to judge a speaker system by the recordings available.
If you'd like to go into more detail about the distortion mechanism or measurement methods we can certainly discuss it a bit deeper.
I have orchestral A/B files on my server which compare a standard mic (10% distortion) with my own mics (<0.1%), if anybody is interested :
http://www.simpsonmicrophonesarchives.com/AB/Andy
