Recording - May 2014 - 8

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This article really resonated with readers
Hi Bruce: I just finished reading your 2-parter about Helmholtz
resonators (December 2013 and March 2014). Thanks for the
most helpful article I've read in years.
I have two questions about the article, though. First, you mention performing a room analysis. What should I use to figure out
what frequency needs to be tuned? And my other question is,
does it matter where the port is located? Thanks!
RL Alexander
New Jersey

Bruce Black replies:
Hi RL! The easiest and least expensive way to find your room
resonances requires an SPL (Sound Pressure Level) meter, and
the ability to play a sine wave through a speaker and manually
sweep its frequency. You can get an SPL meter at Radio Shack
or online (try Amazon.com). If your DAW doesn't have an oscillator/tone generator, you can find one online.
You're going to be tracking the relative SPL as you sweep through
a low-frequency sine wave. However, the low-frequency response of
the cheaper SPL meters can get dicey due to the cheaper and smaller capacitors used in them. Get the best you can afford.
Send a sine wave to one of your speakers and sweep it
between roughly 30 Hz and 200 Hz while watching the level
on your SPL meter, which should be set up with its mic at your
primary listening position. Zero in on the peaks by sweeping
back and forth across them, and write down the frequency and
SPL at the highest readings. Move to the left and right a few feet
and repeat this process at each position. Move back from your
listening position and repeat the entire process. You can also
move all around your room and repeat the process if you like.
Be sure to use only one speaker. Using two speakers introduces uncertainties and unnecessary complexities. If you really
want to get into it, take a bunch of readings with one speaker,
and then repeat the process with the other speaker. This provides more data points, which gives you better accuracy.
At this point you should have a series of numbers for each
position. Some of the numbers will repeat in multiple positions,
closely if not exactly the same. These are the numbers you
should use for the tuning of the resonator.
Also, if you have any particularly large peaks exclusively at
your listening position, you should consider making a resonator
at that frequency, as the listening position is where your creative
decision-making takes place.
Since you may have space limitations, use the levels you
wrote down to prioritize which frequencies you will build resonators for. Since the Q (bandwidth) of the resonators is rather
broad, even with no absorbent inside, you can chose the port
size on the drawing in the article that is closest to your frequency of interest. This also means that there's no need to build a separate resonator for two close frequencies.
I like to place the port on the resonator in a panel position that
allows the resonator to be placed as close as possible to a tricorner where three room surfaces meet. This positions the port

to influence resonances on all three room dimensions. A
bicorner (two room surfaces) will work too, but it only influences
resonances from two dimensions. So a port as near as possible
to the corner of the resonator allows it to be placed as close as
possible to a tri- or bi-corner. I hope this helps out!-BB

Getting schooled
Dear Eric Alexandrakis: I enjoyed your December 2013 article, "Remixing Depeche Mode's 'Should Be Higher'". I also am
a Depeche Mode fan, especially "Strangelove". In the late
1980s I was a small-time engineer/producer in a studio
equipped with an SSL 6000 board, Lexicon 224XL, Otari 24track reel recorder, Studer Revox 1" Stereo Master recorder, and
JBL monitors with 18" woofers, silk dome tweeters, and loaded
horns with QSC amplifiers. I've never heard anything like it. So
beautiful.
Please help me with your advice-I have been away from the
industry for a long time and am just trying to get back into it
again with all the new technology, and I am pondering my education options. What DAW certifications and schooling do I
need? Respectfully,
Ken Bogle
via email

Eric Alexandrakis replies:
Hey Ken, sounds like you had a really nice setup!
Education options? I suppose it really depends on what you're
trying to do. I find that if you already have a background in
sound engineering, the new tech can be learned via manuals,
experimentation and taking a night class or two. Unless you're
looking to get some sort of Bachelor's, school can teach you the
tools of the trade... but in the end, for this trade (especially if you
already have a degree), networking and unique output is what's
going to grab people's attention.
If you're not set up to attend a school, I'd enroll in a program
online to go at your own pace earning your degree, while learning new tech/skills, and interning at studios/recording your own
material to pull attention towards your craft. Mix local artists for
free if necessary, get into the game in your town so that you
have something to show.
DAW certification isn't as important as knowing your DAW
inside and out. Avid Pro Tools is the standard, but I love Logic
because I'm Apple-obsessed since 1982, and it fits my workflow
and is fun for me. It's also more affordable than Pro Tools, if of
course you already have the Mac to run it.
All of my engineering skills I learned on my own, without
courses or degrees in that field. Just manuals and experimentation can get you what you need, but some kind of degree makes
one more acceptable in order to get into a more professional setting. All in all, focus on recording/mixing a great band/artist,
work hard, and hopefully everything will fall into place. Best of
luck.-EA

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