Big rig audiophiles do play wide bandwidth high SPL material, while avoiding the more revealing small scale acoustical forms that don’t work so hot with muscle amps and enormo-loudspeakers that excite too many lower mid and LF room modes.
If I pop in that Art Pepper disc and there is any flub or doubling in the LF, I re-cut the system arrangements until it’s gone. If “Who Made Who” does not result in utter annihilation LF, that means I overdid it with the Art Pepper, and more adjustment is needed.
Those fast kick drum hits in the remastered Foreigner Greatest Hits (especially “At War With The World”) instantly reveal excess at 63, 80, and 100 Hz, and the Black Eyed Peas stuff can reveal deficits or excess at the same spots.
To summarize, think Pepper and Ellington for fidelity, AC/DC for genre specific horsepower, Foreigner to minimize standing waves, and the Peas to make sure the LF works for what is happening now.
My students did a tweak on our big (lotsa subs, lotsa horsepower) rig recently with (ugh) “Billie Jean”. It sounded OK until I got out the aforementioned LF reference discs. Foreigner sounded like total mud, you couldn’t hear both heads of the kick on “Who Made Who,” the jazz stuff had weird notes popping out (like at 100 Hz) – the Peas sounded like a disco band on a ’70s system – you get the idea.
They re-did the thing (using Audiocore running on XTA DP226s and 224s) with the real reference discs and it passed all the tests with no problems, beyond the lovely contribution of our HVAC ducts, which seems to have a problem with eight double-18 Martin subs and a zillion watts of Lab.gruppen power.
There is one disc that qualifies (for me) as an infallible full bandwidth reference. Remember – I hate being forced into non-voiced tweaks, but it happens. Sometimes there is no time for the full LF tweak sequence. Also, more sensitive clients would be upset by some of those tracks. You need one multi-purpose disc for all those occasions.
The next time I hear it will be one time too many, yet Janis Ian’s “Breaking Silence” remains the champ. Recorded with minimal (the audiophiles say none, but I don’t buy that) processing, it is a female folksinger/pop singer with a small group. For some reason it was mastered at a low volume – you need to turn it up more than most discs.
Go to the last cut, crank it (careful though – it starts with a whisper, and then ramps up significantly) and prepare for the mother of kick/snare/bass grooves. Her voice is totally neutral – any 1K6 is you, not her. You can finalize the whole system with that cut, though the whole disc is a wealth of useable information. It will translate to all genres – not as well as a voice tweak with the reference LF disc sequence, but close enough to get you through the night.
It is not as familiar as “Aja,” or as danceable as “Billie Jean,” and it doesn’t come with a screen and a measuring mic, but “Breaking Silence” reveals the performance of a live system faster than any tool outside the human voice presented through an open mic.
If you’re looking for something more than positive reinforcement (ha-ha) of your reinforcement system – something that reveals rather than mindlessly confirms, you might want to check it out.
And it will help keep you employed.
Jack Alexander designed and supervises the live sound reinforcement program in the Department of Audio Arts & Acoustics at Columbia College in Chicago.