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Old 25th January 2013, 06:35 PM   #1
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Default Tilt Equalizer Filter

Click the image to open in full size.This filter was introduced in the early 1970s by Quad Ltd in their model 34 preamplifier. A single knob allows you to tilt frequency response around a pivot frequency (Fp), by simultaneously boosting the treble and cutting the bass frequencies or vice-versa. See Heawwize site:
http://headwize.com/?page_id=741
Up to now the filter was tuned by means of PSpice simulations.
In my EDN article:

http://www.edn.com/article/520749-Implement_an_audio_frequency_tilt_equalizer_filter .ph

I derived the transfer function and the formulas to calculate the components value following the desired
Fp (pivot frequency), the Boost/ Attenuation at Low frequencies and High frequencies.
Next time I will give you some examples.
If somebody will a particular Tilt equalizer, I can calculate the components.



Last edited by Francesco Balena; 10th February 2013 at 05:16 PM.
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Old 19th February 2013, 01:51 AM   #2
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Default Tilt Eq

Can you add a second pot to vary the pivot frequency?
Thanks!
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Old 9th March 2013, 10:48 AM   #3
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Quote:
Originally Posted by SmartAlex View Post
Can you add a second pot to vary the pivot frequency?
Thanks!
That's a good idea! Let me "sleep" over that, I will reply soon! FB
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Old 18th March 2013, 05:12 PM   #4
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CHANGING Fp pivot-frequency. Dear SmartAlex,
If we see the parametric equations in my EDN publication there is a good news and a bad one.
Good: the pivot frequency Fp can be changed without changing ML and MH (asymptotic low/hi freq boost-attenuation)
Bad: you must change the couple of capacitors C (fig.1) to change Fp. With other 2 capacitors in parallel to C (with a switch) allows to have Fp = 440 Hz, 1kHz, 3kHz.
If you give me your specifications: ML, MH, Fp1, Fp2, Fp3 etc.. ,I will caculate the componentsfor you. FB
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Old 21st March 2013, 11:12 PM   #5
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In the article, it shows a response that varies between about 100Hz and 10k Hz, but below 100Hz and above 10k Hz the response has flattened out. Can these limits be changed, and how? Is it possible to make the frequency region where the tilt is occurring wider?

This is very interesting! A tilt circuit would be very useful in investigating at what tilt a loudspeaker will sound "the best". This has been recently debated by Sigfried Linkwitz and others...

-Charlie
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Old 22nd March 2013, 09:28 AM   #6
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Very interesting ! Mr Charlie !
Again, let me sleep over that and I will reply.FB
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Old 1st April 2013, 11:14 PM   #7
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[QUOTE=CharlieLaub;3421642]In the article, it shows a response that varies between about 100Hz and 10k Hz, but below 100Hz and above 10k Hz the response has flattened out. Can these limits be changed, and how? Is it possible to make the frequency region where the tilt is occurring wider?

Is FIG. 01 what you ask for? Figure depicts the responses at wiper position x = 0 Ohm and x = 50 kOhm. The blue curves have a wider tilt zone (F-3dB shifts toward 20 Hz and 20 kHz). Unfortunately ( at my knowlege ) the only way to widening the tilt zone is to enhance ML and MH (the max asymptotic boost/attenuation at at low and hi freq. , that happens for the extreme wiper positions of P1, i.e. x=0 Ohm , x= 50k OHM). See FIG. 02. So it is possible but ML and MH are very high:24 dB. The boost/attenuation jumps from 6 dB to 24 dB.
6 dB: the signal is enhanced (atten.) 2 times;
24 dB: the signal is enhanced (atten.) 16 times!
FIG. 01 : the blue curves are artifacts; the black one have:
P1= 50 kOHM, fp= 1kHz, ML=2, MH=2, Rf=50 kOHM, R= (50/3) kOhm, 4.77nF.
FIG. 02 : blue curves: P1= 50 kOHM, fp= 1kHz, ML=16, MH=16, Rf=(10/3) kOhm, R=(10/51) kOhm, C=50 nF.
Comments? Bye Francesco
Attached Images
File Type: jpg FIG 01.jpg (80.2 KB, 59 views)
File Type: jpg FIG 02.jpg (64.3 KB, 72 views)
File Type: jpg TILT-FILTER.JPG (50.3 KB, 96 views)
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Old 1st April 2013, 11:28 PM   #8
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Quote:
Originally Posted by CharlieLaub View Post
A tilt circuit would be very useful in investigating at what tilt a loudspeaker will sound "the best". This has been recently debated by Sigfried Linkwitz and others...
-Charlie
Maybe Linkwitz refers to the lobe tilt. The interaction between tweeter and woofer in the cross-over zone can "tilt" the emission lobe ( up or down ). Can you help me?
bye Francesco
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Old 13th January 2014, 02:43 PM   #9
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Hi Francesco,

Good work here! I would like to read the EDN article but the link is broke?

Ed
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Old 19th January 2014, 02:42 PM   #10
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Quote:
Originally Posted by jamesecox View Post
Hi Francesco,

Good work here! I would like to read the EDN article but the link is broke?

Ed
Right! the old link does,nt work anymore... here is the new:

Implement an audio-frequency tilt-equalizer filter | EDN

Thank you Francesco balena
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