Design Overview

Hegeman's Letter

In 1978 Stewart Hegeman wrote a response to a review by Harry Pearson of Absolute Sound magazine. Hegeman wrote: “You tend to lean, like the rest of the industry, towards a sophisticated public address system when it comes to speakers.”

I think that went over Pearsonʼs head as well as pretty much all the rest of the reviewers. It is with that statement in mind that I thought that it high time to present an overview of speaker types to point out the different approaches to audio reproduction. It should be noted from the outset that it is not a matter of musical taste.It is rather a matter of “capturing” an event, and then launching it in the home via loudspeakers. Any studio recording using multiple microphones, mixers and manipulated by the engineer can be described as “creating” an event. It never sounds real. It canʼt. It always sounds like youʼre listening to a fake source. Hegeman was obsessed with the concept of capturing a live event and accurately reproducing the experience in the living room.

In theory the perfect sound reproducer (loudspeaker) would be a pulsating sphere. Think of a pair of basket balls somehow magically suspended in midair in your listening room. A tough engineering feat. Beam us up Scotty. Down here on planet earth we are faced with a list of roadblocks not the least of which is gravity. We want everything to appear to be emanating from a point and having equal dispersion. Under no circumstances do we want to hear any unwanted resonances. In other words we do not want to hear the cabinet or drive units rattling around which distracts our attention. We only want to hear the envelope of sound being launched from the basketballs. The best we can do is create the illusion that we are firing from a hemisphere, trading off the sound going straight down to the floor.Using one full range driver is too much of a compromise. In order to wring out low frequencies weʼd have to sacrifice some of the top end. Conversely the low end can be rolled off to extend the highs. Then we need another drive unit to fill in the bottom. Any full range drive unit capable of full spectrum response wonʼt play loud enough and/ or will have unacceptably high distortion. Think of headphones. The best practical compromise is a two way system using long throw wide bandwidth drive units. We can fudge the perfect point source requirement by snuggling the drive units as close as possible while still maintaining a hemispherical launch pattern into a solid angle. This was the jist of Hegemanʼs comment to Pearson. It would seem that not much has changed in the time since 1978. In the audio world marketing always trumps science.

Time is of the Essence

The great race of frequency response is a red herring. Letʼs suppose youʼre walking down the street and hear the sound of a piano coming from a second floor window. The window may only be cracked open a foot or so but you know that itʼs a real instrument. In fact, youʼd bet a thousand dollars that itʼs a real piano up there. A microphone parked beside the piano will pick up a response pattern which will be fairly smooth and extended in frequency. Another mic parked down on the sidewalk will exhibit a completely different waveform. The response will certainly collapse in a heap above 2 K hZ or so since the waveform will have to bend around the window frame and reach the street. Traffic noise will also certainly play havoc with the signal to noise ratio. And yet you will still bet that itʼs a real piano in the room up there despite the much distorted frequency response and extraneous noise. This goes against the rules of high fidelity. Perhaps weʼd better take another look at the things that matter. Cast your mind back to when you were a lad and you were always on the lookout for saber toothed tigers. When walking through the woods it was a matter of life or death to be able to locate the whereabouts of the beast. The snap of a twig and a few growls help to locate the position and distance lest you become lunch. Our ear/brain function has been evolving for thousands of years to enable us to survive. The reality aspect just like the 2nd floor piano was caused by time, not frequency. Those audiophiles who hunger for the reality of a music event seem to always bet on the wrong horse. As a result they constantly miss the boat. If your goal is to reproduce a music event that has any hope of sounding “lifelike” in your living room there are a few ground rules which must be adhered to. Ignore these rules at your peril.
(1) Assuming a two channel playback system the performance must be recorded with two and only two microphones. Any additional micʼs and itʼs all over. Period.
(2) Using a point source omnidirectional speaker is the only method of reproducing a lifelike sound in the living room. Period.
(3) Using a conventional bipole, dipole or monopole signal launch pattern will always result in a public address type of sound reproduction. Of course if you are trying to reproduce those rock concert experiences of your youth with a forest of microphones and banks of speakers in a hockey arena all bets are off. If you spend enough money and down several pints of ale you may be able to replicate those incredible sound pressure levels but it will never sound lifelike. Period.


The word “imaging” when applied to a speakers ability to recreate a scene or “soundstage” can be a bit misleading. In the early days of stereo there were numerous recordings of “ping pong” stereo displaying hard left right scenes. The consumers were dazzled by this and were keen to go from their mono rigs to stereo.It became somewhat costly and time consuming to place 2 microphones in a concert hall in exactly the right position to capture the event. The shareholders were not amused. The cure for this was the mixing board. Now a forest of microphones could be installed quickly and the chap twiddling the knobs could give you the sound he thought would be pleasing. A bit of drums here and a touch more guitar there. The net effect was to achieve a pleasant sound for the owners of mediocre sound systems since 99% of systems were fairly mediocre. The result has been some of the most dreadful and unnatural recordings ever. Thatʼs why mono recordings (one microphone) sound more acceptable than multi mic mixdowns. Audiophiles who never attend live unamplified events have no clue what a system can create in terms of lifelike reproduction. The shenanigans going on with the mixing, gain adjusting and polishing to create a perfect sound result in a wholly artificial presentation. With a conventional monopole speaker the best you can do is create the illusion of instruments being louder or softer while at all times being within the confines of the cabinet boundaries. The sense of listening to an electro mechanical device never goes away. Itʼs like gazing at two picture frames with something going on within the frames. Sometimes youʼll get lucky and have a thin curtain of sound strung between the speakers which constantly shifts around depending on the efforts at the mixing board and where you sit. When sitting hard left the cello in a string quartet will almost vanish when using monopoles. The first violin tends to take on an “in your face” perspective. There is endless repositioning of the speakers with toeing in, toeing out, and tilting forward, backward and carefully measuring distances. It never sounds natural. It canʼt. When sitting hard left in front of correctly implemented point source omni directional speakers there is a natural perspective. The first violin sounds a wee bit closer than if you are seated dead centre and the cello moves from nine feet away to twelve feet away just as it does in real life. There is no incessant nattering about the imaging ability of the point source omni, it simply gives a natural perspective which allows the listener to delve into the music as intended by Beethoven, Bach and Mozart. This is no fun for the equipment junkie. He always prefers his hi-fi to attending a live performance.