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Last month we looked at the development of bass guitar
speaker systems from the fifties to the eighties. This
month we continue from the nineties to the present. Of
course there are a few holdovers from earlier decades,
especially the Ampeg SVT that still remain popular today.
GALLLIEN KREUGER 800RB
You may have noticed last month my omission of a popular
piece of bass equipment in my discussion of the eighties.
This would be the Gallien-Krueger 800RB. Since our discussion
is centered around speakers more than amps I left this
out because while the amp head was a leap forward, the
GK cabs were not revolutionary. But amplifier development
is closely tied to the speakers and I want to mention the
800RB now because of its popularity and its influence on
subsequent designs. A main attribute of the 800RB is that
this solid state head distorted musically unlike other
solid state amps of the time that became unmusical sounding
when pushed.It was well built electronically using high
quality components, although the chassis did not hold up
well under touring, unless mounted in a rack case. The
800RB contained several features that were cutting edge
for the time. There was an on board electronic 2 way crossover
with adjustable frequency and separate level controls for
the two outputs. The crossover outputs fed two internal
amplifiers, one for lows at 300 watts and another for highs
at 100 watts. One other notable feature was the Boost control,
enabling a variable and foot switchable volume boost for
solos.
THE NINETIES
The first major trend of the nineties was a move away
from large PA like bass guitar systems to smaller more
portable systems. The eighties were over and the thousands
of bands playing local venues with huge backline,PA and
lighting came to an end. It was no longer economically
sustainable to carry large amounts of equipment, so now
players wanted equipment they could fit in an SUV or car.
The major players in the nineties for bass amps seemed
to be Hartke, GK and SWR. Hartke manufactured affordable
equipment that was decent for its price point, GK released
newer designs moving forward from their 800RB and SWR released
decently designed amps that sounded good. The paper used
in the SWR speaker cones was thinner than the paper in
a lot of other bass cabinets contributing to the characteristic
tone of the SWR bass systems. Almost all brands of amps
now incorporated the features pioneered by the GK 800RB
and most added compression and better thermal management
(fans and related heat sinking). Technology was progressing
in the nineties and amplifiers were becoming more powerful
and stable. The introduction of more and more equipment
built in China gave you more watts etc. and kept the price
down.
The most accepted change in bass speaker cabinets in this
period is the 4x10 cabinet. This is sort of half an SVT
cabinet. But remember, the low end response of a cabinet
using ten inch speakers comes from the line array effect.
The wavefronts of the individual speakers are coupled together
so they act as a single speaker with a larger surface area.
But four tens is not eight tens, so the lows are not there
as much as with an 8 X 10 cabinet. But the smaller individual
ten inch speakers due to their smaller cones have a snappier
more defined mid and high ranges as opposed to the larger
cone mass of a fifteen that develops more inertia as the
amplifier tries to pull it back and forth blurring the
mids and highs. Therefore the four ten cabinet was well
suited for the popular slapping and popping bass style.
The other cabinet that became popular is a sealed back
and ported single fifteen inch cabinet by itself or part
of a bass combo amp. What a lot of players don't understand
is unless the single fifteen cabinet has an incredible
speaker and computer tuned ports, you don't have a prayer
of keeping up with even a moderately loud drummer. As I
have stated in the past, increasing power is not directly
related to increasing volume.Two hundred watts is not twice
as loud as a hundred watts. It will take a thousand watts
to be twice as loud. So it follows when using a single
fifteen that the power to it starts to increase dramatically
as you start to push it. Also the cone surface area of
a single fifteen inch speaker will only give so much low
end causing the speaker to move further in its excursion
and straining it. Adding just one more fifteen will help
by dividing the power from the amp between two voice coils
instead of one and doubling the cone surface area creating
more low end with less amplifier power.
One other modern feature has been the introduction of
a high frequency horn integrated into the bass guitar speaker
cabinet. This can be a plus to those players whose style
includes popping and slapping, In fact a 4 x 10 cabinet
with a horn is well suited to this type of player as the
desired tone is often seems like it was added as an afterthought.
The inclusion of a small piezo horn as in the GK MB212
series does very little to add highs to the sound.It is
also very easy to blow. The addition of a dynamic horn
driver (better than piezo) requires an additional crossover
assembly. A Piezo horn has a high impedance to low frequencies
so it has no problem handling a full frequency signal.
Lows will have no effect on a piezo horn, but a dynamic
horn requires a crossover to keep the lows out of the horn
so it doesn't blow. The crossover itself converts power
from the amp to heat so there is an insertion loss stealing
wattage away from your volume. Many crossovers include
a light bulb used as a limiter and sometimes also a fuse
for the horn. Fusing a horn is almost a futile effort.
Due to the dynamics of the signal if the fuse is small
enough to protect the horn it is also small enough to nuisance
blow from signal peaks during your gig. Make the fuse larger
and it offers almost no protection. Balancing the horn
volume with the speakers is also problematic. If a high
quality horn is used, it is also usually efficient and
too loud to balance with the speaker. The solution to this
is to add an L-pad level control to the horn circuit so
you can dial it back in volume to match the speaker. The
L-Pad is another component that is usually underrated and
will toast itself shutting off the horn. It's one thing
to have a piezo blow out, but when you are using a horn
with a crossover the amplifier's entire top end is given
over to the horn through the crossover. If the horn goes
out the whole top end goes away. At least if a piezo horn
blows,since it doesn't use a crossover, the remaining speaker
receives the full frequency response from the amplifier
leaving at least some top end present.
RECENT DEVELOPMENTS- THE 2000'S
The latest trend seen in bass guitar systems in the last
few years is the Neo speaker. This type of speaker contains
a magnet made from the rare earth material neodymium. A
neodymium magnet has more magnetism with much less weight
than a conventional speaker. These speakers are usually
designed into bass guitar systems utilizing switching power
supplies and class D amplifiers which also weigh next to
nothing when compared to equivalent conventional amplifiers.
This gives the ability to create a 300 or more watt amplifier
and a speaker cabinet with eight tens that can be carried
amp in one hand and speaker in the other. Try that with
a real Ampeg SVT!. But that may be its most important attribute.
Does a circuit containing what amounts too a computer power
supply and a very different type of amp circuit sound as
good as conventional gear? I don't think so. First of all,
if you look at the waveform on an oscilloscope, there are
many high frequency artifacts in the signal. They are very
high frequency but they are there. Secondly these type
of circuits perform well within their designed specifications
but have a tendency to fail when pushed. The Neo speaker
also does not work as well when pushed. A heavy conventional
speaker magnet has much more mass than a neo speaker. This
acts as a heatsink to help conduct heat away from the voice
coil. The neo speaker is lacking in this respect so it
has a higher likelihood of failure. One other problem is
that the Neodymium magnets come mostly from China and the
price has been increasing dramatically, so Neodymium is
fast becoming Unobtanium.
Next month will be the final installment in the Speakers
series and will feature PA speakers
Steve
Weiss is the owner and main technician of Steve Weiss
Electronics Inc. He is experienced in the repair
of analog and digital musical equipment. This includes
everything from Vintage Tube Amps and Pro Audio equipment
to Digital Keyboards There is also a guitar repair
shop staffed by some of the areas top guitar repair
techs. He is authorized for warranty work on most
major brands. Steve Weiss Electronics is located
inside of Sam Ash Music at 5460 West Sample Road
Margate, FL 33073 954-975-3390 Ext 272. Steve has
also spent 25 years on the road as a performing guitarist
and is the designer of Primal Guitar amps that can
be seen at Primal
Audio.com Steve can also be reached at stevew@metromusicmayhem.com |
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