[BC] Optimod 9000-vs-9100

[Robert Orban]

At 09:30 PM 10/8/2009, Broadcast List USER wrote:
>Frankly, the original 9000 (which my AM used) was abusive on AM radio
>too.  It just had too much HF boost.  (Sorry, Bob, but that is just my
>opinion.)  I don't blame this on Orban, but rather on the AM radio
>manufacturers, especially those who made car radios.  They rolled off
>the high end so much, that the high end boost was the counter-attack.
>It was a bad time in audio.
>
>Then again, the 9000 did cut through the radio in my Ford Fiesta.

If you extend the concept to consumer AM radios in general, that was the point.

>  It  was typical of the era (1984).  The stock radio just rolled off the
>high end in the extreme.
>
>That brick for the air monitor actually had too much high frequency
>attenuation.  I ended up using an external EQ, and it sounded good.

Our passive rolloff filter for the air monitor's response was 
carefully synthesized to emulate the average AM radio response that 
we measured in the early '80s based on about 20 radios. It turns out 
that it was almost identical to the results of the 2006 NRSC AM radio 
frequency response measurements -- very little had changed in 20 
years. Once again, the point was to help broadcasters get a sound 
that would complement the typical radios their listeners were using. 
The rolloff filter was intended to be useful to set up a reference 
environment for adjusting the processing. Its main limitation was 
that real radios tended to roll off more abruptly than the filter 
above 5 kHz -- the filter's rolloff was 18 dB/octave.

The rolloff filter had an adjustment that allowed you to limit the 
amount of rolloff to your taste by inserting a shelf at higher 
frequencies. When you dialed in more highs like this, the filter no 
longer emulated a typical radio. However, the adjustment retained the 
most important aspect of the typical radio's "sound" -- the fact that 
the rolloff was typically down 3 dB at 2 kHz.

If the goal was to make something that sounded "pretty" in the 
control room for the talent, then a graphic equalizer would work as 
well as anything else. But it is unlikely to be useful as a reference 
environment for adjusting the processing.

Bob Orban