HELIUS DESIGNS: In conversation with Howard Popeck – part three

Geoffrey – what is your response to the statement ‘How many channels do you think it takes to make a music listener happy; One. Mono's fine. I've never heard anybody bitch about Louis Armstrong, saying, "I would enjoy it if it were only stereo"

Now this question is interesting from several perspectives and I’m going to come at this sideways, so bare with me for a minute. In the first instance, the greatest portion of what you hear ( in the context of both live music and recorded music ) is reflected off walls, ceilings and floors, so unless you listen to your hi-fi in an anechoic chamber, the dispersion characteristics of your system contribute significantly to your enjoyment of the music.

But here’s the contradiction – dispersed sound is a mixture of phase shift, time delay and echo ( try swapping the leads of one speaker ) Referring back to question 1 of this interview, ‘can a sound be wrong but good’, yes – with the right music, an artificially diffuse sound can be ‘wrong’ but give the impression of an enormous sound-stage.

For this reason, and returning to answer the question - I don’t mind the use of rear speakers in conjunction with Ambisonic electronics. ( quasi 4 channel - IMF, circa 1980’s ) However, when it comes to Quadraphonics, I just don’t see that it contributes anything other than sending a strong message to one’s wife/girlfriend that invites divorce. For me ..... it’s a gimmick and one that demands the listener sits in a swivel chair, in the middle of a room with no furniture between you and the four speakers spread 90 degrees apart - 4 channels is not for me.

Okay, thanks. So how do you apply this to your design engineering?

When designing speakers, I often use a mono source. My reasoning being that I evaluate a system by its ability to reproduce the human voice – moreover, I prefer using bass voices as they highlight design flaws more readily than sopranos.

Why mono?

Well .... simply because a voice is point source ( well, almost ) so you don’t really need two channels.

Why the bass voice?

Because it extends to 60Hz ( I do, and I’m not ‘that’ deep. My singing range is 60Hz to 3KHz. ) I do not believe it’s possible to reproduce a coherent male voice if the speaker’s crossover frequency is anywhere around here.

Traditionally, the frequencies used for bass/mid transition are between 300Hz and 700Hz. If you consider that 400Hz ( pure tone A ) is used by musicians as a tuning reference frequency, I do not see why anyone would want degrade the signal by adding phase shift and roll-off problems. Do you really want your music to suffer from major distortions smack-bang in the middle of the range where most music comes from?

Certainly not. So, can you expand on this please?

Yes, of course. Playing a deep male voice in mono really tells you a lot about the flaws in a design; and before anyone asks, my preferred crossover frequencies for a 3-way system are 60Hz and 4KHz ( yes, 60Hz – not a typo) . A purpose-designed midrange enclosure remains phase coherent and untainted by the demands of a box otherwise designed to optimise bass output.

I think that does it – 4 music channels? Definitely not; though perhaps if two are for added ambience, OK. Being an audio rebel, I don’t always advocate the purist position, if it sounds good – hell, I’m OK with it. Isn’t that what it’s all about? ...getting into the music? ( regardless of whose product you buy )

Mono is great for testing – and the only option if you want to listen to music recorded in the days when some truly gifted artists abounded, alas - long before stereo

Otherwise – I’m happy with good ‘ol groovy stereo.

Thank you Geoffrey


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