[TenTec] COMMUNICATIONS SPEAKERS Article

[Jim Brown]

On 2/27/2013 10:10 AM, Richards wrote:
>
>   There is no need to get crude or angry over this.

Who's crude or angry?  The late Paul Klipsch, a very bright guy and 
Fellow of the Audio Engineering Society, was known for standing up near 
the back of the hall at certain technical presentations where he felt it 
appropriate, and opening his outer shirt to reveal a Tee shirt 
emblazoned with the word :BULLSHIT in large letters. He was much 
appreciated for his comments.

>
>
>
> What is needed for good speech quality is nothing more or
>> less than a loudspeaker with flat response AND uniform coverage in the
>> speech range.
>
>
>     Funny... that is just what the author was
>     saying.    And he suggested a center channel
>     speaker as exactly that sort of thing.

So is ANY GOOD loudspeaker.
>
>     Otherwise, you have been outvoted by an entire
>     industry - which sells center channel speakers
>     expressly on the premise they enhance speech
>     and dialog intelligibility.  And outvoted by legions
>     of movie fans who buy them for that very reason.

Not at all. When film sound is mixed, ALL dialogue is placed in the 
center, while music and effects are mixed to left, right, surrounds, and 
the sub-woofer. Cinema sound has been done this way for much of the last 
half of the 20th century, and the various forms of distribution and 
encoding for home playback are based on this.

The function of a center channel loudspeaker is to provide a hard center 
channel image, AND to maximize speech intelligibility. The center 
channel maximizes intelligibility NOT because of the type of loudspeaker 
used, but because it is a SINGLE loudspeaker. Indeed, all three front 
channel loudspeakers should have flat response with good dispersion 
(that is, uniform coverage over the listening area)...

>
>
>
>     Exactly what WE are saying !   Apparently you
>     agree with us, after all.   You have just described
>     what we mean by a  "speaker tailored for speech."

I've done far more than that. I've observed that the requirements of 
good speech intelligibility are the same as for good music reproduction.

>
>
>
>> Now, it so happens that Optimus is the "house brand" that Rat Shack used
>> in the 70s and 80s. They didn't make anything themselves,
>
>
>         Nobody does.... it all comes from some
>         outfit in China.   Besides that is hardly
>         relevant or probative of any point under
>         discussion here.

While that is probably true for most vendors TODAY, it has not always 
been thus.
> You have missed the point entirely.
>
>         We are only saying that a small, flat sounding
>         speaker that does not have a lot of bass or treble
>         is one that is "tailored for speech"  --

A good loudspeaker reproduces what is fed to it.  This may come as a 
shock to you, but the frequency response numbers typically quoted in 
catalogs for ham and consumer products are meaningless because they 
include no anplitude tolerances on the response, nor do they provide any 
description of angular coverage, nor distortion, nor efficiency.

Modern loudspeakers designed for home use rarely have much useful output 
below 100 Hz, but most have response to 10 kHz or more. 100 Hz is more 
than enough for speech, and good response to 10 kHz benefits speech 
intelligibility if the content is there.  When a loudspeaker is used 
with a ham rig, the response is limited by (and for the most part, 
DICTATED by) the response of the transmitter, including the mic, the 
transmit filter, the receive filter, and the output stage. Unless 
something is broken in that system, there's rarely much content outside 
the range of 100 Hz to 3 kHz.
.
>         FACT -- not all speakers are well "suited for
>         speech"  intelligibility -- which is why you
>         specified "small" as a design criterion.

I added "small" to the description only because it needs to fit in a ham 
shack without burning a lot of space.
>
>         FACT -- there are loads of flat response speakers
>         that are not well suited for speech applications.
>         Older, JBL studio monitor speakers with 15 inch
>         woofers just do not sound as clear as, for example,
>         the  5 inch Avantone MixCube speaker - or similar
>         size center channel speakers.

That's because some of those older JBL studio monitors have design 
problems!
>
>         By specifying "decent small, accurate loudspeaker
>         that sounds the same over a fairly wide angle"
>         YOU HAVE IDENTIFIED EXACTLY WHAT IS
>         RIGHT ABOUT THE CENTER CHANNEL SPEAKER
>         AND WHAT MAKES IT WELL SUITED FOR VOICE
>         APPLICATIONS.

No, I've described a perfectly ordinary ideal loudspeaker.  What you're 
missing is that the same characteristics that make a loudspeaker good 
for music also make it good for speech.

>
>         FACT -- not everybody agrees what sounds
>         good.   Not all speakers with a flat
>         response will suffice or please everyone.

More technical parameters are needed (and used) to describe loudspeakers 
than you (and most of the high futility community) are aware of. A study 
of the work of the late Richard Heyser is highly instructive.

How "flat" response is measured matters a lot.  Is it measured ONLY 
on-axis, or is it measured at multiple points over a wide angle, or is 
it integrated over a full 360 degree sphere? What is the TIME response?  
If there are multiple drivers, what is the alignment between them?  What 
is the crossover, and what are its characteristics?  These are some 
common problems with loudspeakers, including some JBL studio monitors. 
Perhaps the ones you didn't like (and that I probably don't like 
either).  BTW -- I'm a member of two AES Standards Committee Working 
Groups on Loudspeakers. These working groups include most of engineers 
who design professional loudspeakers, and many other leading engineers 
who APPLY those loudspeakers.

FWIW -- I suspect you would consider me a presumptuous fool if I argued 
with an attorney about the law.

73, Jim K9YC