Equalizer curve advice

[visage]

when making ringtones, I want apply some EQ adjustments to get better sound. I need help to draw an EQ curve which would take into consideration both the general advices for ringtones equalization (attenuate low frequencies 30-300Hz to -24dB, increase frequncies from 300 to 900Hz, cut the response above 5 kHz) and specific speaker frequency response curve(see image). Can someone draw this curve sample?

[kozikowski]

You need to do this because you need to listen to it and make sure you got it right.

It's not that hard. In Audacity 1.3, you can make the curve and then save it for later.

http://kozco.com/tech/audacity/100Hz_Rumble.jpg

This is a low-cut "rumble" filter I designed based on a commercial hardware product. Each of those little dots is a control point and it's a rubber band. You can click on them and push them around as you wish.

-- 3dB is barely noticeable.
-- 6dB is half level.
-- About 18dB is half loudness to your ear (note: 2 and 3 are different)
-- About 60dB is the quiet limit of human hearing.

Koz

[kozikowski]

Db works both directions. Your example is dB up from very quiet instead of dB down from maximum volume. Your scan appears to be from a live microphone which has no natural upper limit to the point of microphone destruction. Audacity always works from "0" which is the loudest a digital sound can get without distortion and damage and then works down from that. Two different ways of looking at the same thing.

The Audacity timeline works in percent which is easier to see. You can change the timeline to dB with the tools on the left.

Your example also might be Sound Pressure Level in a room instead of electrical size, but those two change in step. Increase the electrical size 10dB and the sound pressure level should increase 10dB, given a good sound system.

Koz

[visage]

this graph is typical frequency response curve of mobile phone speaker,from manufacturer's specs. Testing sheme:
http://img19.imageshack.us/img19/4918/testinglz.jpg

SPEAKER MODE
- SOUND PRESSURE LEVEL
88±3dB SPL @0.8,1.0,1.2,1.5KHz in average (0dB SPL=20μPa)
Measuring condition: 0.1W (Sine wave) 10cm measured with baffler shown in Fig.1.
- IMPEDANCE: 8±15%Ω (@2KHz 1V) without baffler.
- RATED POWER: 0.8W. MAX POWER: 1.2W
- RESONANCE FREQUENCY (F0): 850±20%Hz @ 1V. (Without Baffler)
- DISTORTION: Less than 10% at 1KHz, 0.5W
- BUZZ RATTLE: Must be normal at sine wave 2.5V

I tried myself varios settings, what I want is some generic EQ curve that will work in most cases, for most ringtones.

[steve]

Try a high-pass filter set at "900Hz / 6dB per octave"
Normalize to -1dB (minus 1) after applying the Eq.

Setting the frequency at a higher value will make the sound more "thin and tinny".
Setting the frequency at a lower value will increase the "warmth" of the sound, but if you set it too low the speaker will be over-driven and will distort.

I assume that you will be encoding the file in a compressed audio format (MP3?) at a low bit rate - if so, that will automatically cut off high frequencies.

[kozikowski]

Since this is the first I've heard of someone doing this, I assume most people don't worry about it.

You may need to whack off the low frequencies (move the curve I designed up to around 1KHz or so), but past that, the sample curve you posted is more or less flat. I know it doesn't look flat, but remembering you can't hear 3dB variations, that curve is a lot less violent than you think.

Also please note that that curve is "typical" of cellphone receivers. I bet my crappy cellphone would make that one look like a pleasant walk in the park.

Koz

[visage]

Try a high-pass filter set at "900Hz / 6dB per octave"
Normalize to -1dB (minus 1) after applying the Eq.

Setting the frequency at a higher value will make the sound more "thin and tinny".
Setting the frequency at a lower value will increase the "warmth" of the sound, but if you set it too low the speaker will be over-driven and will distort.

I assume that you will be encoding the file in a compressed audio format (MP3?) at a low bit rate - if so, that will automatically cut off high frequencies.

I use 256 or 320kbps MP3 as source, and encode ringtones to 128kbps.
Usually I do these steps after trim:
1. High Pass Filter or Equaluze
2. Compress with default settings
3. Normalize -3dB
Some ringtones sound good, some distorted. So want to find some good Eq settings that will make sound more natural.
To set the high-pass filter before Eq?

[steve]

Your method sounds about right, so now it's just a matter of tweaking them for best results. There are not really any "optimum" settings beyond what you are doing - from there on it depends on the individual sound clip.

[visage]

You need to do this because you need to listen to it and make sure you got it right.

It's not that hard. In Audacity 1.3, you can make the curve and then save it for later.

http://kozco.com/tech/audacity/100Hz_Rumble.jpg

This is a low-cut "rumble" filter I designed based on a commercial hardware product. Each of those little dots is a control point and it's a rubber band. You can click on them and push them around as you wish.

-- 3dB is barely noticeable.
-- 6dB is half level.
-- About 18dB is half loudness to your ear (note: 2 and 3 are different)
-- About 60dB is the quiet limit of human hearing.

Koz

I added this 100Hz_Rumble filter, the curve look slightly different on my computer(I use windows) and it's not horizontal at the beginning of x-axis. Should we attenuate low frequency by -40dB, or -24dB would be sufficient? What's cut-off frequency would be better to set: 300Hz, or 100Hz? Does it make sense to extend frequency response by 6dB from 300 to 900Hz?

[kozikowski]

This is taking way too much work. What's the complaint? That the ring tone isn't loud enough and when you make it louder, it distorts? That's a common complaint for many music applications and juggling frequencies isn't the answer, past the obvious getting rid of the bass notes which no cell phone can handle.

You probably need dynamic compression. Try running the show through Chris's Compressor...

Chris's Compressor
http://pdf23ds.net/software/dynamic-compressor/

... and then adjust the new compressed show down so it doesn't distort. Is that more like the volume you had in mind? If it's still not quite right, you can run through Chris again, although I've never done that for theatrical listening. That should produce a good dense musical clip.

Koz