May. 12, 2016

Conn Electronic Pipes

Conn electronic pipes were first developed by engineers of the Conn Organ Corporation in the late 1950's; many thousands of these units were manufactured and shipped all across North America and the English speaking world through the 1960's and 1970's to enhance the sound of the Conn organ and other analog electronic organs of the time.
These units were a very hot seller back in the day and difficult for Conn dealers to keep in stock; they consisted of a rectangular walnut wooden chest supporting a vertical array of cylindrical anodized metal pipe tubes of differing lengths and diameters, below which one or two pair of 6 X 9 inch oval speakers were mounted inside the chest end-to-end which projected sound waves upward against the pipes which cushioned the sound.
In the case of the Conn organ, these speaker pipes worked only on the main channel voices (diapason, strings, reeds) and not on the flutes (tibias) or Pedal voices.
In many Conn organs there was a set of screw terminals located at the bottom left of the back of the console just below the box with the two Leslie sockets; these terminals were for connecting the Conn pipes (in parallel) using an audio cable with spade connectors; usually there was also a small, 3-way toggle switch on the console to select internal speakers, pipes, or both; with both switches in the "on" position they were putting a 4 Ohm load on the console's internal amp.
Conn electronic pipes came in 3 models; the smaller treble unit was model 145, was 3 feet high, and had 48 pipes mounted in 2 parallel rows; it came in 3 types, the only difference being the configuration of the pipes on the walnut wooden base; type 1 had a symmetrical shape with the longest pipes in the front row being on both ends and the longest pipes in the rear row being centered; types 2 and 3 had only a single row of pipes with the longest ones being on the far right of the wooden base, and on the left, respectively.
The 145 pipes, being a treble unit, enhanced the higher harmonics or upper partial tones of fundamental frequencies from about 200 Hz (corresponding to 8-foot tenor G) upward.
The model 144 treble unit was about half as long as the 145, a bit shorter in height, had only one pair of 6 X 9 speakers, and was available only in types 2 and 3.
The model 146, also available only in types 2 and 3, was made up of 12 longer pipes having cosmetic notches; these were mounted in a single row on the same wooden base as the 145 but were almost twice as tall and capable of handling the lower 8-foot octaves of the manuals; the Pedal stops were wired to speak through their own 15-inch stationary speaker.

The precise dimensions of these units were as follows:
No. 144 -- types 2, 3: 21.5" W, 8.25" D, 29-7/8 H, Wt. 17.5 lbs.
No. 145 -- types 1, 2, 3: 42.5" W, 8.25" D, 34"H, Wt. 18 lbs.
No. 146 -- types 2, 3: 42.5" W, 8.25" D, 63.5" W, Wt. 40 lbs.
Finishes: choice of gold or silver anodized pipes.

As stated, the sound producing portion of the Conn pipes were the 6 X 9 inch oval speakers located in the wooden base (photo); models 145 and 146 with their 4 speakers had an impedance of 8 Ohms (2 pair of 8 Ohm speakers, each pair wired in series/parallel); the smaller model 144 had only two 8-Ohm speakers in parallel with a 4 Ohm load; about 40 watts of amplification power was needed to operate each unit.
The only way for the tone from these speakers to be heard was through the pipes, each of which was permanently tuned to resonate at a different frequency of the musical scale.
Conn engineers had a demonstration of this where a small microphone could be dropped inside any given pipe; this microphone was connected to a regular guitar amp; they used a set of 145 pipes labeled as to their tuned pitch; while holding down middle "C" on the organ, the microphone would be lowered into ANY "C" pipe, and a "C" was heard coming from the guitar amp; then, while still holding middle "C", the microphone would be lowered into a "G" pipe, and one would hear a "G" [3rd harmonic, or 2nd upper partial tone] coming from the amp, and likewise with an "E" pipe, an "E" [5th harmonic, or 4th upper partial tone] would be heard coming from the amp; the sound emitted was non-directional; engineers also noted a very slight bit of reverb after the key was released as the sound within the pipes quickly dissipated.
When the speakers were energized by a tone from the organ the column of air in each pipe acted as a cushion on the tone and had to be put in motion before the sound could escape resulting in the volume building up gradually before the tone blossomed out the top of the pipe in all directions; the metal walls of the pipes which were tuned to the frequencies being played would begin to resonate, then the pipes tuned to the frequencies being played would also resonate; the result of all this resonating and pneumatic action within the walls of the pipes was a wall of sound lacking the beam effect produced by ordinary cone speakers alone; and, as stated, when the keys were released the column of air within the pipes would not come to rest immediately, allowing the tone to linger for a split of a second before dying away completely.
These pipes were untunable but could be connected to play through ANY make or type of electronic organ; they could be positioned to stand vertically or placed on a shelf horizontally, like real trumpet "en chamade" pipes, with the weight of the chests making them stable enough for the pipes not to require supporting bracing.
Those who owned Conn organs with model 146 pipes connected reported that when the cosmetic notches on the pipes were covered up with tape the bass response was increased; we know what a hole in a pipe does -- it raises the resonant frequency, which is what the cosmetic notches on the 146 units did; when these notches are covered up the pipes reproduce the bass tones more as expected.
These units have no input jacks; the way they were hooked up was that a two-conductor speaker cable connected with the console or external speaker cabinet was attached to the pair of screw terminals at the bottom of the pipe chest by means of spade connectors; each chest received just a single channel of audio.
Back in the day Conn made a pipe connection interface box that was intended to help compensate for the lower efficiency of these speaker pipes and to provide easy switching between the console speakers and the pipes; it was a nice thing to have, but was not really necessary.
Hooking up these units in parallel to a Conn or any other electronic organ today presents a consideration of critical importance called impedance -- the resistance offered by the circuit to the transmission of an electrical current.
Every amplifier connected to a speaker system requires a minimum impedance load (in Ohms); in Conn organs the simplest way to attach these pipes was to hook them up in parallel with the main pulse speakers inside the console for the diapasons/strings/reeds; the internal speakers for this circuit usually involved a single 12-inch and one or more 6 X 9 inch ovals; it's important to understand that connecting a set of Conn pipes in parallel like this with the console's internal speaker system effectively reduces the impedance load to the console's internal amp.
NOTE: When you put 2 resistances (impedances) in series, they total; but when you parallel 2 resistances they split the load, effectively lowering the resultant Ohms; while the formula for calculating this is a bit complicated, when you parallel 2 resistances of the same amount, the effect is, you get half; two 8-Ohm speakers wired in parallel, for example, results in a 4 Ohm resistance; if however one of those 8-Ohm speakers is made of two 4-Ohm speakers in series, you also get 4 Ohms resistance.
Since according to Ohm's Law the voltage in the circuit is the product of the current (in amps) and the impedance (in Ohms), and since the wall socket voltage remains constant, whenever speakers are paralleled and the impedance load is halved the current in the circuit doubles; this can make the amp run hotter and even fry the amp unless it receives the minimum load in Ohms for which it was built.
Conn solid state amplifiers were not quite as particular about impedance as tube amps were, but, like all amplifiers, they were built for a minimum load (usually 4 Ohms) however the speaker system happened to be configured.
When Conn pipes are in good condition one hears a nice sparkle in the sound, but since these units are now 40 to 50 years old, and since dust, insects, and other stuff can fall down through the pipes and accumulate on the speaker cones over time, one may not get the desired sound without opening the units and renovating them, cleaning them up at least, and even replacing the speakers if they're spoiled.
The usual choice for those owners who have done extensive renovating of these units has been 6 X 9 oval replacement car speakers from Parts Express; these replacements are 4 Ohm speakers however, and since Conn used 8 Ohm Cletron speakers by Cleveland in these pipe units one needs to adjust wiring accordingly, making sure the new hook-ups still put a decent load on the amp.
It's important for owners and technicians to understand and appreciate that these units were built to operate on the principle of sympathetic resonance and are not to be compared to the tones produced by direct beam loudspeakers.
These units have always been in limited supply, and today they are still hard to find; besides the quite obvious and noticeable difference these pipes make in the tone they also contribute positive visual aesthetics; their size often allows them to sit on top of the console with the rack up, and they do look awesome there; pricing of them these days seems to be all over the place due to their scarcity, and a lot depends upon their condition, as it seems they're easily damaged during shipment and not very amenable to shipping given their shape.