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   Do you long for the old days--do you fondly remember the JBL "wallbanger" 

sound? Knocking that hideous art-deco kitchen clock off the wall with

Mercury's Antal Dorati recording of the 1812 and evoking ooh's and ahh's from

dumbstruck friends who couldn't believe their ears on hearing your massive 60

watts per channel and the sound of Bob Prescott's "Cartoons in Stereo?"

   In 1961, those of us who could capriciously defy our wives or parents and 

spend $355.80 plus the outrageous $10-$12 cost of high-grade plywood lumber to

build our own 14 cubic-foot cabinets, lived in bliss with the reverently held

belief that a pair of D130's and 075 bullets was as good as a speaker system

ever needed to be, that recorded music could never challenge such a system,

and that some day if we ever got a huge tax return we might think about adding

a pair of 175DLH's to make the ultimate system. We were the audio elite–the

cognoscente who held court for those who thought we were geniuses because we

could plug together a Mac 60 and a preamp and actually set the correct disc

equalization for any one of the many individual record company disc cutting

EQ's used back then–to the chagrin of non-engineer music lovers.

   If you're like me, a child of the fifties, chances are your memory of 

those early high-efficiency systems nags at you and makes you wonder what in

the world all the fuss about "digital-ready" speaker systems is all about.

Yes, JBL was digital-ready 35 years before digital was ready!

   Of course, you can still get an E130 and a 2402 (the current model 

numbers of the old components) and fool yourself into thinking that's hi-fi,

but if you're still the audio tweek you were in 1961, the results of this out

of date thinking will prove uninspiring–the sound you remember won't be good

enough any more. The sound you get won't live up to the memories of it in

view of what you've probably heard over the last 25 years.

    Well wallbanger fans, since 1961, some progress has been made in 

understanding the listening experience, the reasons sound systems never sound

like live performances, and how to improve that enigmatic situation. We know

how all the hardware works now, and we know a lot more about why there are so

many ways to make bad speaker systems. As Danish philosopher Kierkegaard

would probably have said, "audio is like philosophy; at every step it sloughs

off an old skin into which creep its useless hangers-on." If you want to stay

on the leading edge of your favorite technology, you have to have an ecclectic

view of past design improvements. Never mind the fact that today's "recording

engineers" have green hair and can't read music and that most of what goes

into the grooves of pop records emanates from a programmable box. To be fair,

there are plenty of well recorded compact discs available to listen to, and

every reason to expect that good program material will be made by those who

care about music and audio quality more than mass marketing.

   Although JBL's sales of raw components to the home-grown market has been 

continually expanding since the fifties, JBL as a company, has done so well in

professional audio (permanently installed sound systems, touring sound

systems, movie theater sound and musical instrument speakers and components)

over the past decade, and the hi-fi marketeers have innundated the public with

so many ready-made speaker choices, that the proportion of JBL's total sales

of raw components to the hi-fi market has been overshadowed to the point where

supporting that market segment is now unprofitable. JBL loves its loyal fans,

but the time it takes to answer the thousands of questions from them offsets

the resulting sales. As a result of this and the fact that almost all the

consumer calls received by JBL Professional are now inquiries into building

ultimate systems (despite our efforts to send you to Harman America and sell

you the spectacular 250 Ti top of the line consumer loudspeaker system), I

have decided to answer all your questions in writing in hopes you won't call

and nag me.

   This then is what I personally think I would do if I had a lot of money 

to spend on my own home system and could not countenance the occasional doctor

with his super-expensive integrated MacIntosh system, challenging for bragging



   A sizeable number of dissatisfied audiophiles, bass freaks and a lot of 

JBL hi-fi old-timers have called and written insisting on my recommendations

for "larger" home stereo playback systems that might deliver all the gut-

thumping reality of curling up in fetal position inside a rock-n-roll kick

drum. Although the merits of self-inflicted hearing destruction escape me, I

offer what I consider a useful alternative (for those so inclined) to hiring a

live band and a tour sound company when the urge for auditory self-abuse


   The "dream system" described here won't peel the paint from your walls or 

suffice as a P.A. system for rooms larger than a typical vertical assembly

building, but it should satisfy the auditory cravings of even highly altered

punkers, disco-droids and the most masochistic metal-rock fans, while still

providing adequate subtlety for delicate baroque chamber music, your annual

Hogwood Brandenburg, and those ubiquitously popular insect sound-effects


                  The system consists of the following:

[4] 2245H 18-inch subwoofer drivers.

                   [2] 2220H 15-inch midbass drivers.  
                   [2] 2123H 10-inch midrange drivers.
                   [2] 2445J 4-inch compression drivers.
                   [2] 2382 Flat-Front Bi-Radial horns.
                   [2] 2405 Diffraction tweeters.
                   [1] 6290 power amplifier.
                   [4] 6260 power amplifiers.
                   [2] 6230 power amplifiers.
                   [2] 525 active crossovers.
                   [2] 3105 passive crossovers.

The total system cost for these components only, is around $12,000 so

dust off the old mortgage papers and gas up the Rolls for the trip to the bank

for a second on your house.

   The amplifier complement listed will, on demand, deliver 1200 watts to 

the four 18-inch woofers, 1200 watts to the two 15-inch midbass drivers,

1200 watts to the two 10-inch midrange drivers and 600 watts to the two

compression drivers and tweeter units. The total on-demand power is a clean

4200 watts. This may also place demands on you–from your neighbors and local


   Now before you gasp and expectorate "yech!, horns?" be aware that 

everything you've heard is history and most of it was wrong. The model 2382

is a two-inch throat, 120-degree waveguide type device with a rapid flare rate

and virtually non-existent "horn sound" which is due to horn throat non-

linearities associated with smaller one-inch throats and exponential flare

rates and it won't be used in this system to reproduce low enough frequencies

to be obnoxious anyway. Remember the JBL catalog copy of the Sixties: "Steep

wavefronts of explosive loudness are taken in stride by the powerful magnet

and 4" diaphragm." Keep an open mind if you expect to be rewarded with high

sound pressure levels. It's one of Nature's immutable laws that you must make

at least some concessions to get certain benefits (like extremely high sound

levels). Sorry, but you can't change the laws of physics with money. Your

buddy's 7-foot tall Acoustats are going to sound like a $4 transistor radio

next to your system, so stop biting your nails and write the check.


   You will need to build or otherwise acquire (don't call us, we can't 

help) cabinetry that will provide an internal volume of 20 cubic feet for each

pair of 18-inch bass drivers, a separate enclosure of 1.5 cubic feet for each

15-inch midbass driver, a sub-enclosure or separate enclosure of 0.3 cubic

foot for the 10-inch midrange drivers and mounting surfaces for the horns and

tweeters. The whole affair (one left or right member of the pair) will

probably be between 48 and 60 inches tall, about 5 feet wide, about 3 feet

deep and will weigh a lot.

   Build the low-bass enclosures out of something stiff like 6-inch poured 

concrete cast around woofer mounting rings made from 14-ply Finland birch

plywood, or just use the plywood and two-by-four bracing glued and screwed

down on-edge anywhere where you can detect any panel resonance when pounding

on the panel with your 2-pound framing hammer. The goal here is to make the

finished cabinets as rigid as concrete or at least as rigid as possible. Keep

in mind that the system will sound better if you build the whole thing into

flush-mounting soffits in the wall, so you'd better have a long lease or own

the house you intend to modify.

   The exact interior box dimensions for the subwoofer enclosures are 41 x 

33.5 x 29 inches. The 29 x 40 side is used for mounting the woofers. The

ducted vent consists of two boards, 9.25 x 29 inches installed in the center

between the two woofers. This slotted vent tunnel serves both to tune the

enclosure and brace the side panels. The open area of the vent and tunnel is

4.5 x 29 inches (the width of the box), with a total depth of 10 inches. The

13 inch diameter tube thus replaced, wouldn't fit on the baffle anyway, and

slots work the same as tubes–there is no difference at all in performance.

   Line the box interior on all sides with a single layer of 1-inch thick, 

half-pound density fiberglass for internal reflection damping. There is no

benefit, and in fact, there could be deterioration in performance if lots of

fiberglass is used. Fiberglass adds virtual volume to an enclosure. Wear a

mask and gloves when you staple the stuff around the bracing (unless you have

put the bracing on the outside of the box) or onto the panel interiors and

then take a cold shower when you finish. Maybe you won't itch and cough for a


   A word of warning for animal lovers: if you have a cat, you should use a 

screen of chicken wire on the inside end of the ducts in the woofer enclosures

to prevent curious felines from losing any of their nine lives when the cannon

from the 1812 overture awakens them from their cozy nap inside the box.

   For the midbass driver, you have to create a very solid, resonance-free 

enclosure to set on top of the bass enclosure. Once flushed into the wall, it

won't matter if the boxes don't match width and depth dimensions. The exact

interior dimensions of the midbass enclosure are 18.9 x 15.4 x 13.4 and you

will need a vent consisting of a 2-inch x 5-inch slot, cut in the 3/4-inch

material of the baffle, somewhere near the edge of the midbass driver. As

with the woofer enclosure, apply a layer of fiberglass to the interior walls

of the box.

   The midrange driver is housed in a separate sealed enclosure whose inside 

dimensions are 10.7 x 8.7 x 7.6 inches. This enclosure too, should be lined

with the same fiberglass padding, with an extra layer against the back of the

box. It is best to build the enclosure onto a large flat baffle to accomodate

mounting the driver since it is 6 tenths of an inch larger than the inside

width dimension of its ideal enclosure and some relief routing will be needed

to furnish a good mounting and ensure a good air seal.

   The horns can be mounted on 3/4-inch baffles made of the same lumber, and 

don't require sides or boxes, just the front baffle and some way to support it

is enough. If you're a golden-eared audio wizard, you may wish to "align" the

timing of the acoustical signal arrivals at your listening position; to do

this, all you need to do is move the tweeter back over the flat-front horn to

a point where the backs of the two magnet assemblies are lined up vertically,

and move that whole assembly forward to within 3 inches of the position of the

magnet assembly of the midrange driver. If you do this and baffles or horn

walls end up shadowing the mounting surface of the midrange driver, simply

line all facing surfaces (those that have a view of the midrange driver) with

Sonex or similar sound diffusing, irregular-surfaced foam. Do the same on top

of the 2382 horn so the tweeter won't be spraying sound down onto a reflecting



   Once you've finished the cabinets and mounted all the drivers and horns 

and done all you can to assuage your family that you don't need outpatient

psychiatric help, you can hook everything up. Start by making speaker cables

out of the heaviest wire you can find–battery jumper cable is not too large!

The only advantage the "esoteric" cables have over ordinary speaker cables is

that they are usually a heavier gauge, beyond that there is no measureable (or

it would have been published) difference. Cut your cables 50% longer than you

think you'll need for the minimum run, but be careful to locate the power amps

close to the speakers so there is no extra cable length. Carefully label all

your cables (VLF, LF, MF, HF) for left and right and mark polarity if

necessary so you won't get confused, and to be helpful, you should be able to

feel any markers in the dark or around in back of the amp rack if you're

working in confined spaces. The amp rack (crossovers and power amplifiers)

should be wired according to logical engineering practice, crossing signal and

speaker wiring at right angles and isolating any chassis grounds as necessary

to prevent ground loops and hum. It should be possible to assemble and wire

your amp rack so there is no audible hum, just some hiss (associated with

high-sensitivity loudspeakers) from the amplifiers when their gain controls

are wide open.

   The 525 crossovers should be set to divide the subwoofers (VLF) and 

midbass (LF) drivers at 100 Hz. The 6290 power amplifier, in turn, is

connected to the two pairs of 18-inch drivers wired in parallel to each

channel, and the two 6260's are switched to bridged mono mode and each drive

one of the midbass drivers. The MF outputs of the 525's feed one each 6260,

set to bridged mono mode, which are connected in turn, to the midrange

drivers. The dividing frequency for the LF-MF drivers should be set to 500

Hz. The HF outputs of the 525's feed the remaining pair of (bridged) 6230

power amplifiers which in turn each feed one of the 3105 passive crossovers.

The dividing frequency for the MF-HF section should be set to 1200 Hz.

   The 2445J compression drivers are connected to the low-frequency outputs 

of each 3105, and the 2404 tweeters are each connected to the high-frequency

outputs of the 3105 crossovers.

   Hook up the 15-inch midbass drivers in reverse polarity from the 18-inch 

drivers. Hook up the midrange drivers in reverse polarity to the midbass

drivers (the same polarity as 18-inch drivers). The horns and tweeters,

through the 3105's, should be connected according to the red-black

instructions on the 3105 crossover instruction sheet and wired so the input to

the 3105 (red terminal) is reversed polarity from the midrange driver, unless

you have physically aligned the horn and tweeter forward over the midrange

driver, in which case you will flip the polarity of the 3105's input. (NOTE:

this one item may require some fudging and adjustment including polarity

experimentation, to achieve the best group delay characteristics.)


   After you're finished putting everything together and flushing it all 

professionally into your living room wall, you will need to get a 1/3-octave

spectrum analyzer or an audio engineer who has one, and set everything up

properly by adjusting gain controls and the like. If you live in a

metropolitan area, you might even find someone with a TEF machine who is

curious enough to measure and tweek a system the likes of which he has almost

certainly never seen. I recommend that you don't try to play any music

through the system until some measurement and adjustment can be done, so that

you will have no chance to suffer buyer's remorse when, because the system is

not properly adjusted, it doesn't sound right. If you've spent this much

money, you owe it to yourself to finish the job properly.

   The best procedure for setting correct gain between all the amplifiers is 

by the use of sharply defined, octave-wide bands of pink noise. If octave

band filters are not available, use the rule of thumb that the subwoofers are

the least sensitive portion of the system, so they have to be used as the

level reference for the other components, in other words turn them up all the

way, then turn up midbass, midrange, and horns, in that order, until the

levels sound like they match. The frequency response measurement capabilities

of the TEF measurement system are probably the best way to ensure proper

system setup and the machine's time-energy and phase measurement capability

make it easy to properly physically align the components along the listener's

Z axis, forward or back.


   My philosophy on speaker system design is in accord with JBL's.  Simply 

stated, the acoustic power output of the speaker system in a diffuse,

reverberant field, should be as flat as possible. Individual driver elements

should be smaller than the wavelengths they are asked to propagate. I also

feel that none of the system elements be should stressed during operation at

typical listening levels. For the latter and I believe most important reason,

I have chosen midbass and midrange drivers that are the most efficient

available in order to start out with the advantage of operating nominally

below 1 percent of rated power capability. You should find, when listening to

this system, that there is an effortless, bigger-than-life sonic quality that

makes for a very detailed and revealing reproduction of the input signal.

This is due in large part to the high sensitivity of the system components.

   Although there is every reason to want a single small driver to reproduce 

the entire audio frequency spectrum, we know from direct experience that small

drivers can't handle enough power to produce sufficient acoustic output. The

cone of a 4-inch speaker would have to be able to move back and forth 4 feet

to move as much air as the subwoofers in this system are capable of moving.

In addition, the wider the frequency range one driver has to cover, the more

it is subject to doppler distortions; non-harmonic and non-musical irritating

sounds caused by the modulation of higher frequency sounds by large diaphragm

movements associated with simultaneous low-frequency reproduction. The answer

for doppler distortion and power handling capacity is to divide the audio

frequency spectrum into bands, each of which represent a small portion of the

total required power and each of which require only successively smaller

drivers to propagate the successively smaller wavelengths those frequency

bands require.

   The essence of the system's performance is its ability to track 

transients, which, in well recorded musical software, will have peak levels 20

to 30 decibels higher than the average power used to play at reasonable

listening levels.

   Lower efficiency speakers suffer heating of their voice coils and 

subsequent output compression, from high-power inputs. My thinking is that

for a loudspeaker to faithfully reproduce incoming signals, it must at each

moment in time, act as though the signals are the first stimulus received;

that is, it is impossible for a loudspeaker to be accurate if the signals just

reproduced alter the loudspeaker's electrical or mechanical characteristics,

by for example heating the voice coils or stretching the active materials that

make up the loudspeaker's moving parts. In the case of electrostatic

speakers, losses occur as the result of finite power and motion capability.

Electrostatic speakers also suffer from extremely low efficiency. The solution

is to keep input power levels nominally low so heating is minimized, and to do

this it's necessary to use high-efficiency drivers as system elements. The

disadvantage of high efficiency drivers is that they cover narrower frequency

bands as their efficiency increases. Conversely, wide-bandwidth drivers (the

JBL LE8 is an example) always exhibit low efficiency–a direct manifestation

of physical laws.

   You may wonder why it's necessary to provide a bridged 600-watt amplifier 

for a driver that will be operated nominally at a watt. A 20 decibel musical

transient peak requires 100 times the power required by the average signal and

a 30 decibel peak requires 1000 times the power required by the average

signal. The 600-watt power output capability of the amplifier driving the

midbass units represents just a bit less than 28 decibels above 1 watt of

power reserve for the tracking of transients. If you are an electrostatic or

bi-polar speaker fan, you will loathe the sound of this system until you get

used to it, after that you will loathe the electrostatic and bi-polar types.

An analogy of the perceived effect is that this type of system (high-

efficiency type) is like removing an electronic compressor from an otherwise

good speaker system.

   There is bound to be "time-smearing" or "image smearing" from any sound 

source that is not a simple point in space, but by aligning the system

elements in a straight vertical line (except the subwoofer drivers),

horizontal time and image smearing is eliminated. Humans don't perceive

vertical time and image smearing unless they jump up and down in front of the

speaker system–a practice I don't recommend for critical listening (divides

your attention). Since JBL's individual component loudspeakers are matched

very closely as a matter of manufacturing practice, the stereo imaging of the

system should be spectacular.


   A serious word of warning:  the system described here is easily capable 

of producing sound pressure levels far in excess of that which will cause

irreversible hearing loss–don't take this lightly. You might suffer not only

permanent hearing loss, but also constant ringing in the ears that can cause

insomnia and lead to nervous disorders or emotional problems. JBL and this

writer make no claims and take no responsibility for the design, operation or

consequences of using the system described here.

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