[Elecraft] OT (Yamaha Cm 500)

[Jim Brown]

On 11/16/2010 10:19 PM, Joe Subich, W4TV wrote:
>   >  I ended up with:
>   >
>   >  50 Hz   -16 dB
>   >  100 Hz  -16 dB
>   >  200 Hz  -16 dB
>   >  400 Hz  -10 dB
>   >  800 Hz  -16 dB
>   >  1.6 kHz   0 dB
>   >  2.4 kHz  +3 dB
>   >  3.2 kHz  +6 dB
>
> I think that is doing too much cutting at the low end and not
> enough boost at the high end.  Adding 6 dB at each band from
> 200 Hz to 3.2 KHz would make me more comfortable.  Like, Jim
> I prefer to leave 50/100 at -16 regardless as they contribute
> nothing to communication.

Joe,

Yes, I agree that Alan is doing way too much cut on the low end.

I meant to respond earlier to your recommendation of high boost.  I've 
helped a LOT of K3 users adjust their TX audio using a CM500, and I've 
NEVER heard a CM500 that needed ANY boost EQ.  I've also gotten a lot of 
very positive reports on my CM500s (I own two) and I've never used any 
boost.

So I started thinking about why you might like boost -- after all, 
you're a pretty sharp engineer. I can only come up with three scenarios 
where you might prefer that. The first scenario is IF bandwidth on the 
listening station.  I always listen to the other station with my IF 
bandwidth at about 2.7 - 3 kHz, because I don't want what MY RX is doing 
to color my judgment of what the other guy is transmitting. So I get him 
sounding good that way, and THEN I narrow up my IF to 1.8 kHz and listen 
again.

IF you listen at 1.8 kHz bandwidth with the high end of the IF cutting 
around 2.4 kHz or below, you certainly ARE going to want a bit of boost 
on the high end, because the RX IF is rolling it off.. But if you center 
that IF a bit higher, you won't want that HF boost.

The second scenario is that since CM500s are pretty inexpensive 
products, there may be a fairly wide tolerance on the response of the 
capsules.  I've seen some anecdotal observations that suggest this might 
be true.  I DO believe, however, that the CM500s I own, and those I've 
helped set up on the air, do NOT need HF boost.

The third scenario is hearing loss.  We old farts have put a lot of 
mileage on our ears, I know that I've got some hearing loss, and so do 
many of my friends my age, especially those of us who work with audio or 
radio professionally, or even as active hams.  The nature of MOST 
hearing loss is that we lose the high end first, so we want more high 
end boost.  I find that I need to do that with many news magazine and 
interview programs that have poorly produced audio. I find it 
professionally disgusting that the technicians who produce these 
programs have the balls to call themselves engineers when they obviously 
don't know what an equalizer is for or when to use it. But don't get me 
started. :)

The reason I'm going through this is that I hear so much badly distorted 
audio and splatter during contests, and the LAST thing that we need is 
HF boost to produce more of it when the mic is already providing that 
boost, and the CM500s I've heard DO have that HF boost built in.

Also a response to Alan's suggestion of tuning for flat spectrum on the 
display.  IF, and ONLY IF, the spectrum display is providing a VERY FAST 
and very reliable peak and hold response, that is a potentally useful 
way to START. The problem is that most displays are averaging, and the 
average power of human speech is greatest in the lower octaves, so an 
averaging display should NOT look flat. But it is NEVER wise to depend 
only on any form of spectral response display to set EQ. The final test 
instrument must always be our ears and the grey matter between them.

73, Jim Brown K9YC