Tannoy Reveal 5A Owner's Manual - page 5
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First the theory. For unblemished stereo imaging and frequency response you would want to listen in a completely reflection free environment, like an anechoic
chamber, where all you would hear is the image and the direct sound produced by the speakers, no nasty reflections anywhere. For most people this is
impractical. Next best thing, if you can establish a listening position free of reflections arriving within 2 milliseconds after the direct sound (that’s the time it
takes sound to travel about 24" or 600mm or less which represents all frequencies from 500 Hz and up), and minimise reflections arriving within 10 milliseconds
of the direct sound, you can maintain a remarkably stable stereo image, and uniform response throughout the mix area. The "direct sound" is just that, it is
the shortest straight-line path that sound can take from the speaker to your ear, no bounces, no reflections. The 2 millisecond reflection window really affects
the character of the sound at the mix position, drastically altering the response of the speaker in the critical audio bands of 500Hz and above. The 10 millisecond
reflection window does some more subtle things to the speaker’s response, because the ear/brain reads reflections arriving within 10 milliseconds of the direct
sound as being part of the speaker’s response, these reflections can pull the stereo image around in different directions at different frequencies. Enough theory,
now to the lab.
Here’s where we have fun with science. Take the microphone stand and place it at the mix position. Attach one end of the string to the top of the mic stand,
and stretch the string out to the front of one of the monitors. This is the direct sound path from the speaker to your mix position. To locate all the surfaces that
will contribute reflections within that magic 2 millisecond window, add 600mm(24") to the string you have stretched out. Take a small piece of gaffer tape
and attach the string to the baffle (NOT the drivers!). Now, every surface you can touch with any part of that string can contribute a reflection to your mix
position.
This same concern about reflecting surfaces applies to all nearby widgets such as computer monitors, outboard gear, coffee cups, rolls of tape, the producer’s
wooden leg and all the other usual paraphernalia found in a studio environment. Cleaning up this short sound path between the speaker and your listening
position is like using a cotton bud on your ear.
You can repeat the process with an extra 3000mm (10 feet) of string to see which surfaces will influence the timbre and imaging of your mix. This exercise is
not just about finding places to stick fuzzy or foamy absorbers to, the last thing you want to do is make your room completely dead. What this process will
show you is which surfaces you should try to angle to redirect reflections away from your mix position. If there are surfaces that you cannot move or shift, you
can apply a small amount of absorbent material to specific surfaces, rather than covering the entire room in absorbers.
You may want to consider a speaker placement other than the console meter bridge, perhaps on an elevated mounting arm attached to the wall, or on a
mid-field monitor stand, just behind the console. These positions can help clean up that 2-millisecond window. Keep your ears open for other problem reflections,
like between the sloped connector panel on the back of the console and the baffle of the speaker, which will find its way back to the mix position a bit too
late to be useful. The string trick works just fine for locating these reflecting surfaces.
It’s important that you listen to the effect of speaker placement on the sound character of your speakers, and understand what those changes are going to do
to your mix. To make the point here’s are some more things to consider: -
4.4: SPEAKER MOUNTING
You’ve probably got your monitors delicately balanced on your console meter bridge, or sitting on a counter top beside your hard disc editor. Find some
music with some real solid low end that you know well. Try listening to this music with the speaker sitting directly on the mounting surface and then with
it sitting on a thin piece of rubber pad. Hear a difference? Which one sounds more like the recording should? Does one get tubby, or muddy? Depending
on the type of mounting surface, you may find it beneficial to use a thin layer of flexible material (i.e. Bluetack) beneath the enclosure. This not only absorbs
some vibration, but will help prevent the monitor from vibrating off of its mounting surface.
4.5: BASS PORTS
The Reveal 5A monitor’s’bass port is located on the back panel. You should keep the back panels at least 150mm (6") away from the nearest wall surface
to avoid an overblown bass sound. If you cannot avoid being close to the wall or if you’re using a separate subwoofer, you may want to consider plugging
the port tubes on your near-fields with a closed cell foam-rubber plug, friction fit for a full seal. Because the ports aren’t needed if the monitor speakers
are being used with a high pass filter, you won’t be losing any bass performance and you can improve the mid-bass response by plugging the ports.
4.5: EQUALISATION
Our feeling is that you shouldn’t equalise monitors at all; variations in the monitor response should be fixed through placement (after all, that’s what
this manual’s about). But we realise that equalisation is sometimes a necessary evil. If you have a choice of equalisers for monitor applications, less is
more. The fewer the number of filters, the better the equaliser will sound. A stereo five band parametric is better than a stereo 15 band that is better
than a stereo 1/3 octave. You may not realise that in all but one or two brands of 1/3-octave equalisers, all 30 filters are in series. There is a minimum
transit time through each filter of some 25 microseconds, plus just a bit of decay time for each filter. Even with the equaliser set flat, it does not behave
like a straight piece of wire in the time domain. If you don’t need to equalise your monitors, then don’t hook an equaliser up to them at all.
An important thing to keep in mind if you are equalising these compact monitors is that they are not intended to substitute for really large loudspeaker
systems you might use for tracking synth lines, or drum samples. Don’t try to equalise them to sound the same as the 15" monitors you were listening to
in the in the music store. The equalisation of your near-fields should be undertaken with great subtlety. With only the best intentions of correcting some
of the placement related characteristics we’ve talked about here, a subtle bit of reduction in the mid bass where the console or table top will give you a
rise, perhaps a bit of tailoring to taste here or there. As a general rule for this application, you should never need more than 6dB of control range, and
you should never see two adjacent filters with more than 6dB of difference between them. Over equalisation can reduce system headroom, and introduce
phase distortion resulting in greater problems than cures. Always check out the result of equalisation by listening to well recorded vocals or speech.
6.0: PERFORMANCE DATA
ON AXIS ANECHOIC FREQUENCY RESPONSE @ 1m
The STRING analyser
5.0: REVEAL 5A DIMENSIONS
184.0mm
271.5mm
313.0mm
298.0mm
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