You are going to invent your very own
loudspeaker system. "Your very own" means that you may try to realize a soundreproduction
which gives the "being there" illusion, with a wide, high and deep stereo image,
with extended bass and high frequency reproduction, a system which will give speed
and magnitude as if you were in the concert hall. That is the extravert way.
Or you just may want to build a very small two-way system which does not have
the impact of large panels and big units, but lets you imagine a perfect world
of harmony and inner detail. That is the more introvert approach.
many possibilities in between. There are many ways that lead to happiness.
You can look for a neat and precise reproduction or you can achieve the live experience.
I myself want to have the experience of the live performance sound in my
listening room. A grand piano should just stand there in full bloom. A violin
should have that same live character as when my brother is playing a Tartini sonata
or a Kreisler piece. A drum should show its vibrating skin. Already for that instrument
you need a large surface to reproduce the lows and the lower mids. And the brass
section should have the snoaring, high, top frequencies which are so characteristic
of that warm and yet scintillating and chiseled sound. Yes, writing about it is
easier than making it happen.
The first thing to do is to learn what the
sound of acoustic instruments is like in reality. Even if you are not too fond
of classical music you should go to a concert hall from time to time to listen
to a symphony orchestra or a piano recital. You should go to a jazz club. You
should pay attention when a fanfare plays in the swuare of your hometown or just
passes by in your street with that firm sound of the drum and the dynamics of
While constructing you will learn that sound is not only
frequency and decibels. You will learn that it is also amplitude and that the
low frequencies produced by your bass speaker should have the necessary amplitude
to give the mid and high frequencies a good basis to produce the harmonics in
the respective registers they are responsible for.
Amplitude can only be
achieved by dynamic loudspeakers and not by electrostatic loudspeaker panel and
isostatic speakers.(br)If sufficient amplitude is lacking in the bass or an irregular
amplitude curve (like in ported speakers and transmissionlines with a dip around
60 to 75 Hz.), than the mid and high registers will be restrained and will repeat
the harmonics of the irregular patern in the bass. But once you have heard a big
system like a Klipschorn which -because of the high efficiency- can make the step
from a tender pianissimo to a realistic, but well controlled fortissimo in a few
milliseconds, untill you have heard a Cabasse Atlantic which reproduces a Bösendorfer
Imperial Grand as grand as real life, untill you have heard the impact of a drum
accompanied by cymbals in a symphony orchestra, or have heard the live performance
of a violin in your listening room, you may aim for big speakers. Only then of
course when you have enough space and your wife or partner does not object.
2. Transient and harmony
Although harmony, phase, wide range, transient
response and amplitude are all related and depend on each other, one can say that
harmony is the first important aim to be realized. You can find an extremely harmonious
configuration without being completely correct in all registers. I have heard
fantastic active speaker configurations (some of my own) which made the hairs
on your arms stand up and could move you to tears just because of the impact the
harmonious sound had, yet the system was behind in many other aspects.
depends on the correct phase of the entire system.
Transient response depends
on phase. If the fundamental frequency of an instrument (say 40 Hz.) is not being
followed by its harmonics (80, 160, 320, 640 Hz. etc.) with their natural sound
levels, the plucking of a base player in a quality jazz recording does not sound
Transient response also depends on the bandwidth of the system. That
is why in the golden days of analog quality phono stages boasted on a bandwidth
of 400.000 Hz. instead of the limited 40 or 50 kHz. The drawback of most of those
devices was that they picked up signals form radio stations (you could hear Radio
Moscow via your cartridge) and transmitters for pagers.
Bandwidth also depends
on the source and on the amplification. Analog sources provide a far better transient
than digital formats.
3. Best loading
You are going to reinvent
the loudspeaker as it were - if you have not already done that earlier by building
a passive speaker system.
Be aware of the fact that an active system is different
from a passive system. Since there are no passive filter sections (no coils and
capacitors), it is necessary to determine a different and appropriate volume for
each and every unit. The interesting thing is that you can determine the loading
of each individual unit, not only by calculating with formulas and measuring through
programs, but also by listening to the performance in practice. In this way you
can create the sound you want. The basis is of course the sort and quality of
units which you have chosen.
For the lower mids I have built cabinets of which
the volume is adjustable. The surface of the cabinets are squares, but the back
is a plyable wood panel. You can adjust the panel in order to find the best back
loading of the unit.
4. No hurry
Make sure that you have loudspeaker
systems to listen to, even if these are simple but effective 2-way speakers like
those of Mission Electronics or Bowers and Wilkins. This means that you will be
able to enjoy music while you are going the long way of building an active system.
So you need not be in a hurry to finish your active system (if it ever will be).
While listening to the smaller speakers, you will be confronted with correct sound
and this will make you realize if you took a wrong direction somewhere on the
While devising and optimizing the active system
you should use (two or three, depending on the configuration of the system) identical
power amplifiers. It is not advised to use different makes and types of power
amps unless you can measure that the phase characteristics are indentical over
the entire frequency band.
Preferably simple, but correct loudspeaker cables
should be used in the beginning for your system. Or cables that do not have anomalies
and/or manipulated and/or do not ask for very heavy power amplifiers. Use Supra
Cable for instance, the simplest Monsters or a sophisticated, well balanced type
like Cardas. Be sure to know the qualities of the cables you are using. Simple
cables have the advantage that they are not expensive. You will need at least
2.5 m for every channel. Use the same type for all channels. Uniformity is the
key word in building a good system. At the end you always can connect the speaker
sections using very expensive cables and adjust the system slightly if necessary.
The choice of loudspeaker cable depends also on the sort of amplification you
choose: tubes, transistor, high power, low power, all in relation to the efficiency
of the loudspeaker units.
Be sure to have a good source:
CD-player and/or turntable. You should know the behaviour of the source, its qualities
and its limitations. Do not compensate for shortcomings of your CD-player and
phono section (cartridge, arm, phonostage), but make sure these sources are performing
correctly. If you are in doubt of the correct performance of your high end turntable
and 4 kilo bucks cartridge, use a good but simple specimen that has justified
its existence over the years as a good analog source. Momentary I play with a
vintage Shure M91 moving magnet cartridge and am amazed and enjoy a very good
overall performance with a very good midband.
Remember that room temperature
will specifically alter the performance of a phono cartridge and of tweeters filled
with ferro fluid which is more supple in summer and at high room temperatures,
than with an everage 21 degrees Celcius when viscosity is lower.
As for the
CD-player, just leave it always switched on. I have switched mine on several years
ago and it was only switched off a few times when dusting or changing its place.
Of course quality interconnects between source, preamp, electronic crossover and
power amplifiers should be used. The affordable Cardas type (from www.diycable.com)
are an excellent option. Whatever your choice is, make sure that the interconnects
from the crossover to the power amps is of one and the same brand and type.
7. Listening room
While constructing and optimizing you will notice
that you will compensate for acoustic anomalies (imperfections) of the listening
room. Standing waves will easily be generated. Your starting point should be a
given position of the speakers which can be adjusted slightly if necessary when
you are progressing. Read the article about Loudspeaker
Placement to get more ideas and information that you can apply to your listening
room. Place the speakers some five to six foot apart, to begin with. And determine
a good distance from the side walls and the back wall. Distances depend not only
on the room, but also on the width of the baffle and the size of the units and
the position of the units.
8. Surround sound
If you want to extend
your system to surround sound you can do that later taking your active system
as starting point. Since the additional surround speakers are restricted in their
frequency bands, they only will influendce the reproduction of the midband. In
that case the best placement of the rear and center speakers have to be found
without altering the active system (if it is optimized). This means that you still
can listen to old, fantastic high resolution analog sound when you wish to. You
would not give that up just for some heavy door-slamming and car crushing in an
action movie. Would you?
Stands or racks used for the
power amps should be identical. Do not forget that when a rack gets heavier by
placing more heavy power amplifiers in it, the sound reproduced by the units can
It is a good thing to couple the bass enclosure to the floor
with spikes, right from the beginning.
If your listening room has a concrete
floor it is a good thing to make holes of 10x10mm in the carpet so the spikes
are completely free standing and not touching the carpet..
Electronically as well as acoustically there are variables which need to be controled
and adjusted. First there are the levels. These are very critical. You will learn
how to adjust the levels of the various sections in relation to each other. A
slight turning of the volume of one channel can alter the sound significantly.
Especially when using 6 dB slopes, the turning of 1 mm of a volume knob can be
You also will find that you need a stepped configuration of the units
and that the vertical distance between the units is as important. You have to
determine the correct distances. They relate also to the levels and the slopes.
The choices of slopes are determined further by the width of the baffle and
The choice of 6 dB or 12 dB slopes determines the ease of the
reproduction. Slopes of 6 dB per octave would be the best option. In that case
you need to choose units that are very linear and have a natural roll off.
You will find that combinations of 6 and 12 dB will still give the best phase
characteristic. A 12 dB low pass for the woofer and for the tweeter a 12 dB highpass,
while the mid band has slopes of 6 dB at each end is a very good configuration.
Personally I do not like 24 dB/octave slopes because they tend to make the transition
from one register to another rather difficult and they will easily restrict amplitude.
As said earlier, levels are crucial. The slightest increase or decrease will effect
harmony, transient response (slam) and distortion. Good luck!