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What Is That?

Dave Yantz- Tech Editor

What is that ?(A basic overview)

The Fletcher Munson Curves are a study of human hearing . They did the study by having different people in different age and gender groups listen to two different frequencies at the same time and turn a knob to make the sounds equally loud. The data that they got was compiled into a chart that is called the Fletcher Munson Curves. This study was done and published in 1933.

What did they find ?

What they found was that humans hear different frequency's at different levels(or volume). We hear the frequency of 3,300 Hz the best.(about the frequency of a snapping twig) and the levels drop off fast at 40 Hz (at the low or sub frequencies) and at 10,000 KHz at the high end of our hearing. The Human hearing frequency range is from 20 Hz (Low) to 20,000 KHz (High).

They did not find that husbands have a hard time hearing there wives voice though. That's a differant study. (Smile)

What does this mean to me and my Dj Biz ?

Well you need a few more facts.

Most speaker manufactures do NOT make one kind of speaker enclosure. The Fletcher Munson Curve is one of the reasons they don't.

If I am in a band , and doing live sound....I Know that people hearing my performance will not be able to hear the High's and Low's as well as the Middle Frequencies.(According to the Fletcher Munson Curves) So To help them hear the music evenly I need a speaker system that boosts the Low and High frequencies. There called P.A. Enclosures (or speakers) Speaker manufactures know that live sound needs this boost to have a Flat sounding system. The term "Flat Response" is where we humans hear all frequencies evenly.

If I am a recording engineer, making a master for a CD or other recording. I know that most of the people listening to the recording will be hearing it on a car or home stereo.

To Insure that they can hear all the frequencies evenly on stereo systems that lack the performance of professional systems, I will "Boost" the recording of the Frequencies Below 40 Hz and Above 10,000 Khz to make up (some) of the lack of there home systems performance.

Now...I'm A DJ...

I buy a set of P.A. Enclosures (like the band has) and use CD's or other recordings that have the Low's and High's Boosted for home use.

Guess what happens ! .....the sound is very "Bright" ......the Highs all most (or do) Hurt your ears. You need a EQ to tone them down for close up use. And in my Bi-amp system the Sub Amplifier clip lights come on long before the High Amplifier is working hard. Even though the sub amp is twice the power of the high amplifier.

Now you know why.

Speaker manufactures also make Music Playback speakers. And they work very well for that...because they also know that the Recording engineers Boost the Low and High frequencies. So the speaker manufactures make design changes in the enclosure to make up for that fact. But for crowds over 500 people and/or outdoor shows there normally not enough and we are forced to use a P.A. Line of speaker to get the sound out to all of the venue.

The Answer...?

Well there is no one answer. If you plan on being able to cover 500 person shows and/or outdoor events properly. You will need at least one pair of P.A. enclosures to be able to do the show properly. When you do smaller shows and events you will have to tone down the P.A. Enclosures with the use of a EQ.

P.A. speakers will sound better at large events or outside shows.

But if your shows are never outside and never over 500 people. A Pair or two of Music playback speaker enclosures are your best choice.

Close up the music playback speakers sound better than EQed P.A. speakers.

Most speaker manufactures state there recommend uses for there speaker lines. READ THEM ! As you now know, Price is not the only difference in there Speaker models.

Have a tech topic you would like to see covered in this column ?

Drop me a E-Mail and you may see your topic in the next issue of the DJZONE!

Dave Yantz






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