Manley JUMBO SHRIMP - Manual (Page 14)

More Helpful Hints...
You may have bought a great system but there is a good chance that you are only getting a fraction of
its potential. Very frequently we have experienced top quality electronics sounding unimpressive simply
because acoustics were ignored. Even amongst studio engineers, few can really tell the difference between
good speakers in a bad room and bad speakers in a good room - but they all know good speakers in a good
room and very likely so do you. Acoustic techniques are better explained in books on recording studio con-
struction. You can buy good ready-made acoustical materials and/or build them yourself for a fraction of
the cost. Dollar for dollar, you can expect far greater improvement with acoustic treatment than expensive
interconnects.
Most people think acoustics is about sound-proofing but there is a lot of info available for improving the
reproduction of music. Sound-proofing is usually expensive. Luckily just improving the acoustics in a
room can be pretty painless. You may be able to change or move what is on the floors and walls (without
getting expensive or ugly). The improvements may be dramatic.
Number One on the bad list is parallel surfaces. That pretty much includes most rooms. Parallel surfaces
can support a very short echo that is known as a standing wave. It boosts some frequencies and cuts others.
This effect is often called comb filtering because of the multitude of peaks and dips. One cure is breaking
up the big surfaces with a variety of smaller ones. The good news is that book shelves, curtains, wall hang-
ings or macrame, plants, furniture and lamps all help. Not only does this balance live surfaces with dead
ones but “checker-boarded” areas also act as a sort of diffuser. You can probably build low cost effective
and attractive diffusers or have them made if you want something better (and more efficient).
Number Two is very unbalanced room treatment. Both too “live” and too “dead” is generally bad. One
might think that wall to wall carpets & curtains is going to be fine but watch out. All that stuff only eats
highs and a little mids, but doesn’t do anything to the lows. The lows end up very live in contrast to very
dead highs. One way to balance this is get some thick absorbsion into the corners. Thick absorbsion in
the corners is most effective to lows. The idea is to balance high and low absorbsion. Even normal speech
sounds weird in near empty rooms with plain painted gypsum walls and hardwood floors. The simpler the
decor the more intense the acoustic problems. The only hints we can offer is that the wall behind the speak-
ers and behind you are often the most important. You can build some simple absorbers. Simply cut two
4’X8’ pieces of 2” rigid fiberglass or open cell foam rubber into 16”X8’ strips and wrap some white cloth
around them. Easy, clean looking and cheap. Experiment, lean them against the wall at various places.
Even very experienced acoustic designers experiment, listen then decide rather than attempting to predict
every result. A variation is to use “perf-board” as a backing if you intend to stretch the fabric reasonably
tight. It may also help with hanging the strips to the walls. Perfboard with a one or two inch space behind
it is an alternative front surface to increase diffusion or can do double duty as a simple helmholtz absorber
(for the low mids) and can be effective on the ceiling. You can hang a few up there either flush or dropped
a few feet if you have the height to absorb lower frequencies. The wall behind the listening position is
usually responsible for too much or too little lows compared with the rest of the room. Read up on slat and
membrane absorbers for problems there - the panels described above won’t help much for that.
Number Three is lack of left/right symmetry. In order to get the left and right similar sounding and
getting a rock-solid center you should have identical left and right walls and distances. The ideal is a
perfectly symmetrical room but this may not be practical. Again, try to achieve this with positioning.
Some of the “test” CDs have a variety of low frequency tones or sweeps. Use them to find rattles and
buzzes in the room. Lamps and fixtures, some cabinets and components can do this. A little tape or glue
can often fix these types of things. If you are getting serious about this kind of thing you can get a variety
of test gear from measurement mics to real time analysers or computer software. These are useful tools but
do not depend on the readings unless you are very experienced using them. Best to use your ears and use
the test gear to verify what you hear and to document the changes. Remember that test gear neither makes
records nor listens to music. Frequency measurement often ignores “time” and exagerates some factors and
glosses over others. Steady tones are virtually useless in real rooms. The more comprehensive tests give
complex data that needs to be correctly interpreted to be useful. Use ‘em but don’t jump to confusions.
Always use ears too. Ears are fabulous instruments.
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