Why Do We Need Equalization and Room Correction?

[octagon]

Originally Posted by Big Daddy

This is a preliminary and unedited post.

Did anybody else read that and in their head hear Doc Brown apologizing for the crudity of his model?

[srrndhound]

Originally Posted by Big Daddy

The curve is referred to as the house curve. The curve should have a steeper slope in small home theater rooms and a flatter slope in bigger movie theaters and auditoriums. The reason is because in a movie theater we are too far from the speakers and as a result higher frequencies are attenuated more. Therefore, we need to boost the higher frequencies to compensate for this. At home, we sit too close to the speakers. As a results, they sound brighter. That is why we should cut higher frequencies more.

If the larger distance in theater is causing a rolloff in the higher frequencies, then why wouldn't the calibration microphone, which in the same location, experience that rolloff too?

Actually the issue, for steady state measurements, is the reverb being longer in theaters. This fools the microphone into seeing more level than the human will perceive because while the microphone cannot distinguish reverb from direct sounds, we do, and judge the response based on the direct sound.

[LordoftheRings]

Originally Posted by srrndhound

If the larger distance in theater is causing a rolloff in the higher frequencies, then why wouldn't the calibration microphone, which in the same location, experience that rolloff too?

Actually the issue, for steady state measurements, is the reverb being longer in theaters. This fools the microphone into seeing more level than the human will perceive because while the microphone cannot distinguish reverb from direct sounds, we do, and judge the response based on the direct sound.

Very true and an excellent point Roger!

________________________________

And if I may add; all the EQ in the world won't fix poor room acoustics to begin with.
Acoustic Room Treatments should always be the very first step!

[Big Daddy]

I added significant amount of information on Frequency Masking and its effect on Speech Intelligibility to post #2.

[Fors*]

Originally Posted by Big Daddy

I added significant amount of information on Frequency Masking and its effect on Speech Intelligibility to post #2.

Wow, you sure did.....interesting read too BD!

[Big Daddy]

Originally Posted by Fors*

Wow, you sure did.....interesting read too BD!

That is probably another reason why we should not run the center channel speaker full-range, particularly for movie applications. The idea of putting a subwoofer inside a center speaker never made much sense to me.

[LordoftheRings]

Originally Posted by Big Daddy

That is probably another reason why we should not run the center channel speaker full-range, particularly for movie applications. The idea of putting a subwoofer inside a center speaker never made much sense to me.

I'm with ya on that BD. The bass info from the special effects that is in the Center channel is much better reproduced by a dedicated and properly positioned Subwoofer. Same for the low bass from Music.
And the dialog, or voice from a Tenor singer is nil below about 150 Hz.
So you can cross your Center channel at 100 Hz and that would be just fine (or 90, or 80 Hz).

A center channel that can cleanly reproduce the audio frequencies to somewhere between 40 and 60 Hz is amply sufficiant. So you can cross it at 80 Hz with perfect blending.

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* What you guys think of that?:

@ http://forum.blu-ray.com/4210801-post36.html

[Big Daddy]

Originally Posted by LordoftheRings

I'm with ya on that BD. The bass info from the special effects that is in the Center channel is much better reproduced by a dedicated and properly positioned Subwoofer. Same for the low bass from Music.
And the dialog, or voice from a Tenor singer is nil below about 150 Hz.
So you can cross your Center channel at 100 Hz and that would be just fine (or 90, or 80 Hz).

A center channel that can cleanly reproduce the audio frequencies to somewhere between 40 and 60 Hz is amply sufficiant. So you can cross it at 80 Hz with perfect blending.

____________________________________
********************************

* What you guys think of that?:

@ http://forum.blu-ray.com/4210801-post36.html

Did you get a chance to look at post #2 on Masking?

[LordoftheRings]

Originally Posted by Big Daddy

Did you get a chance to look at post #2 on Masking?

I just did now! But man do I am impressed with those posts of yours Big Daddy! They help so much at understanding so many audio factors in audio reproduction.

* Is Blu-ray.com will have a poll soon on voting for the most helpful member of the year 2010?

And you know what too? With your sticky threads there shouldn't be any more audio forums at all with people having questions!
...But then, how many of them (including myself) take the time to read them all?

[Big Daddy]

Originally Posted by LordoftheRings

I just did now! But man do I am impressed with those posts of yours Big Daddy! They help so much at understanding so many audio factors in audio reproduction.

* Is Blu-ray.com will have a poll soon on voting for the most helpful member of the year 2010?

And you know what too? With your sticky threads there shouldn't be any more audio forums at all with people having questions!
...But then, how many of them (including myself) take the time to read them all?

You can start the poll. Just rig the poll so that I win. I promise I will share the rewards with you.

[LordoftheRings]

The rewards are this: Thank you sir! ...For everything, including your generosity and good sense of humor.

[K-Fed2]

BD that was by far the most interesting read i have come across in a long time. I had always wondered why high freq sounds loose impact off of center. I'm a visual learner so to see a graph did it for me.

Your information on here makes complicated things make sense to guys like me.

in regards to the lowest freq. of a bass guitair, I had read before (google search) that the lowest string on a bass guitar is 41hz. your sticky lists it at 30hz. I will take your info as the correct lowest freq.

Regards,

K-fed2

[Big Daddy]

Originally Posted by K-Fed2

BD that was by far the most interesting read i have come across in a long time. I had always wondered why high freq sounds loose impact off of center. I'm a visual learner so to see a graph did it for me.

Your information on here makes complicated things make sense to guys like me.

Thank you. I spent a lot of time preparing and writing this thread.

in regards to the lowest freq. of a bass guitair, I had read before (google search) that the lowest string on a bass guitar is 41hz. your sticky lists it at 30hz. I will take your info as the correct lowest freq.

Regards,

K-fed2

I am told that B0 (B string on 5 string bass) is 30.87Hz and E1 (E string on 4-string bass) is 41.2Hz. I am not a musician and do not know much about musical instruments. I simply went by the following sources:

http://en.wikipedia.org/wiki/Bass_guitar_tuning
http://wiki.answers.com/Q/What_is_th..._a_bass_guitar
http://www.paranormalghost.com/evp_frequency_ranges.htm
http://www.diyaudio.com/forums/music...ncy-range.html

[LordoftheRings]

Yeah, that was the distinction between a 4-string and a 5-string bass guitar.

[JBALL]

Great thread here! Has anyone tried Audyssey X32 with the mic kit? I tried Audyssey MultEQ on my Axiom speakers but wasn't overly happy with the results. I will try it again with my new speaker upgrades that are coming but I'm thinking about selling my AVR and getting a dedicated prepro with X32 built in.

[rarredoa]

What signal am I supposed to be using so that I can find the peaks/valleys for my speaker frequency response? Pink, white noise? I will be using a 2-channel 1/3 octave equalizer feeding external amps.

[Big Daddy]

Originally Posted by rarredoa

What signal am I supposed to be using so that I can find the peaks/valleys for my speaker frequency response? Pink, white noise? I will be using a 2-channel 1/3 octave equalizer feeding external amps.

Use pink noise. Pink noise is essentially white noise, but painted with a can of pink paint.

I copied the following from another thread. If you don't fully understand it, don't worry. All that stuff is written by some crazy guy who has nothing better to do than confuse us. I wish he would just go away and stop making these incomprehensible sticky threads.

Understanding & Using Test Tones To Calibrate Your System

White Noise
White noise has the same distribution of power for all frequencies, so there is the same amount of power between 0 and 500Hz, 500Hz and 1,000Hz or 20,000Hz and 20,500Hz. This means that the band level increases by 3dB with every Octave. In other words, if you double the frequency, the sound pressure level will increase by 3 dB. For example, assume that we move from the first octave (20Hz to 40Hz) to the next octave (40Hz to 80Hz). The white noise has the same level of power for the 20Hz to 40Hz, 40Hz to60Hz and 60Hz to 80Hz. This means that the second octave has twice as much power as the first octave. The formula for dB level is defined as 10 . log(Power2/Power1) and since Power2= 2 Power1, the formula is simplified to 10. log (2) or 3 dB.

White noise is normally the random noise that we hear as hiss created by all electronic circuits. White noise is also created in nature as wind blowing through leaves or on the beach. White noise has equal energy for each frequency width (cycle). As the frequency (cycles) doubles for each octave, so does the noise energy (+3dB/octave), resulting in white noise sounding as treble sound or hiss.

Pink Noise
Pink noise has the same distribution of power for each octave, so the power between 0.5Hz and 1Hz is the same as between 5,000Hz and 10,000Hz. It has a linear scale so that for each octave band, it will produce the same amplitude. Pink noise is filtered white noise so each octave has equal energy, therefore a flat energy response and is similar to music and useful for acoustic measurements for sound system calibration. Remember that sound system calibration by Pink noise is a simplified approximation only and is not an accurate method.

White Noise Versus Pink Noise Plot
The energy distribution of pink noise is flat, octave-wise. On a logarithmic frequency plot, pink noise is represented by a flat horizontal line. Pink noise sounds evenly spread across all frequencies and best approximates the spectral distribution of music and the human auditory system, which processes frequencies logarithmically.

The energy distribution of white noise is flat which means that it contains all frequencies in equal proportion. Because the human auditory system processes audio in a logarithmic frequency scale, white noise sounds much brighter than pink noise.

[Ethan Winer]

Originally Posted by rarredoa

What signal am I supposed to be using so that I can find the peaks/valleys for my speaker frequency response?

I use the freeware Room EQ Wizard software. It avoids a lot of the drudgery needed to measure manually using noise or test tones. Once it's set up, you push a button and five seconds later you have several different graph types to choose from. More here:

Room Measuring Primer

--Ethan

[rarredoa]

Originally Posted by Big Daddy

Use pink noise. Pink noise is essentially white noise, but painted with a can of pink paint.

I copied the following from another thread. If you don't fully understand it, don't worry. All that stuff is written by some crazy guy who has nothing better to do than confuse us. I wish he would just go away and stop making these incomprehensible sticky threads.

Understanding & Using Test Tones To Calibrate Your System

Ooh, the visual's worth a thousand words! Most of the images are blocked out by the office's firewall.

I just got my Equalizer today, I started to play pink noise and tried to match my system's response to the house-curve. The software I'm using doesn't seem to be cutting it. I am using my Ipad (newest) built-in mic. I tried using the Behringer ultra-linear microphone, but my Ipad would not recognize it. Another flaw, I believe, is that the software (Signalscope Pro) uses 1/3 octave for the RTA. By the looks of things, there's 1/6 octave and even higher RTA's. Looks like I'm gonna have to invest in one of these RTA suites.

Question... how high do I have to play Pink Noise to accurately manipulate the response using the EQ sliders?

As of now, my equalizer's adjusted with the higher frequencies being boosted and the mid-bass 80-180hz range being attenuated. This is of course by ear and by judging using my favorite tunes.

More to follow