Frequency for dummies

ntg

Do they make a book Frequency for dummies or a web site for understanding most of this stuff?
Every time I start reading the threads here and think I am starting to under stand things you guys throw in some graph and I am done

Where do the graphs come from and how many different measuring devices does one have:eek:

Thanks from stupidville

PolkThug

snapbug

steveinaz

Frequency response is a measure of a components ability to reproduce a certain frequency range, with all frequencies as equal as possible in level (amplitude). Human hearing is believed to be in the range of 20 Hertz (Hz=cycles per second) to 20,000 Hertz. 20Hz being very low frequency (bass--think: rolling thunder) and 20kHz being very high frequency (treble--think: the hissing of steam). Realistically speaking, your "average" 40 year old male probably has a range of 20Hz-14kHz.

Measuring involves using a "control" which would be a reference level, say 90 decibles, and then seeing how close all of the frequencies can be reproduced at that reference level. This tells you how linear the response is, in other words--if all the frequencies are being reproduced at the same level (ideally), and if not, what is the deviation in dB (decible) of each charted frequency.

Ideally you want your equipment to reproduce this frequency range with as little deviation in level between frequencies as possible (+/-3dB in level), though it's easier said than done, and generally, the more "accurate" the equipment, the more expensive it is. It is especially difficult (and EXPENSIVE) to build a speaker that covers the full range of frequencies, because of speakers electro-mechanical nature and interaction with the listening room. Most speakers can attain the necessary high frequencies, but getting super-low bass is far more of a challenge.

Summing up, generally you like to see a specification like: 20-20kHz, +/- 3dB, but again, very few speakers can dig down to 20Hz, sans sub woofers.

Remember: Specifications only tell half the story. They speak more to performance capability than they do to the actual sound of the component. There are many components that measure well, but sound like ****; and likewise there are components that don't have fabulous specifications that sound very good. Let your ears be the final judge.

Skynut

Nice Steve, I get confused on these things also.

sunil3478

Good explanation
thanks

madmax

The best way to get a really good feeling for frequency is to get a graphic equalizer and play with it. After awhile you will be able to say things like "I hear a hiss around 13 Khz".
madmax

PolkThug

...and before you know it, you've got a mic, pre-amp, laptop and true rta level 4 and are analyzing the resonating frequency of every object in the room.

JKnPA

Graphs are plots of two different parameters. One parameter is on the 'vertical' scale, the other is on the 'horizontal' scale. Looking at a graph can tell you a lot of information , much easier than trying to express the results in words!
This link shows a graph of speaker impedance vs. frequency.
Notice how the speaker impedance( vertical scale) changes as the frequency source( horizontal scale) changes. Notice the 'nominal impedance' is taken from the flat portion of the chart...........:rolleyes:
http://en.wikipedia.org/wiki/Electrical_characteristics_of_a_dynamic_loudspeaker
Cheers....
Jk

Holydoc

Steve,

Kudos on the explaination. Great job!

steveinaz

Gracias.

michael_w

If you have an spl meter and a laptop (or close enough desktop) give a program called Room EQ Wizard a shot. It's free and can be pretty fun and useful to play around with.

Ern Dog

Here is the link for room eq wizard.

http://www.hometheatershack.com/roomeq/

Deadof_knight

frequencies are all good but the resonances are a pain to deal with in a big room. Sometime they sound better in a room than out as Steve is trying to expain. The speaker you listen too must all be compared in the same way. or you have no true idea in how they sound. They sounded good at the stereo shop yet they sound less than desirable in your living room. The sonics of the environment have changed greatly.

steveinaz

Deadof_knight wrote:

frequencies are all good but the resonances are a pain to dea l with in a big room

Absolutely, the room is a component of the speaker no doubt. You want to hear speakers at their best, take them outside, with no walls to reflect or room resonances **** things up. I tried my speakers out on the patio once, they sounded wonderful---wish I could replicate that in the house.