Hi, trying to mod the wien bridge bandpass filter:
- Parametric EQ
I want so the rollof bellow the lower corner frequency to go bellow 0 db gain.
Up till now I managed to change the freq responce after the upper corner frequency (green graphs), bypasing R5 or R6 with C5
- attached
But I would like to obtain the red graph on my simulation.
This is going to be a vented cab bass response correction.
The frequencies bellow the filter boost are critical for xmax
Regards, Emil
- Parametric EQ
I want so the rollof bellow the lower corner frequency to go bellow 0 db gain.
Up till now I managed to change the freq responce after the upper corner frequency (green graphs), bypasing R5 or R6 with C5
- attached
But I would like to obtain the red graph on my simulation.
This is going to be a vented cab bass response correction.
The frequencies bellow the filter boost are critical for xmax
Regards, Emil
Attachments
That is not a Wien bridge any more.
A Wien bridge based EQ is a Bandpass filter, working around the frequency set up by it, in the ESP example traditional R1 C1 R2 C2 , all other elements are NOT frequency setting ones, but flat gain controls, you can not use them to change frequency response.
As is gain will be unity/0 dB at all frequencies when pot is set 50% , and rise above/below 0dB when moved, (just what you asked) at the frequency set by the bridge.
If you want other kind of curves, explore other Equalizer circuits, do not butcher this fine one.
Maybe you want a Baxandall tone control?
Sorry but this does not make sense in English,try to rewrite it, not sure what your needs/intentions are.
A Wien bridge based EQ is a Bandpass filter, working around the frequency set up by it, in the ESP example traditional R1 C1 R2 C2 , all other elements are NOT frequency setting ones, but flat gain controls, you can not use them to change frequency response.
As is gain will be unity/0 dB at all frequencies when pot is set 50% , and rise above/below 0dB when moved, (just what you asked) at the frequency set by the bridge.
If you want other kind of curves, explore other Equalizer circuits, do not butcher this fine one.
Maybe you want a Baxandall tone control?
Here's another ESP circuit that might work.
Project 197
I built this circuit (Figure 3), with the 45 Hz center frequency and a 3 dB peak. It works great for driving full range (2 way or 3 way) speakers! 45 Hz w/3 dB peak is perfect for 6.5" two-ways.
For a subwoofer you could lower the frequency and cascade it with a low pass filter.
Project 197
I built this circuit (Figure 3), with the 45 Hz center frequency and a 3 dB peak. It works great for driving full range (2 way or 3 way) speakers! 45 Hz w/3 dB peak is perfect for 6.5" two-ways.
For a subwoofer you could lower the frequency and cascade it with a low pass filter.
In general, do I need an output buffer for the wien-bridge?
I am going to stack one boost @20hz and one dip @50hz filters in series.
For the low cut, I am going to add a subsonic filter, eventhough I wanted to omit it, or, have a bit more high pass at the bandpass lower frequency (6db/oct more) from the wien bridge @20 hz.
OR, trying Project 197 (thx Fast Eddie D) in simulation, for the 20 hz boost
I am going to stack one boost @20hz and one dip @50hz filters in series.
For the low cut, I am going to add a subsonic filter, eventhough I wanted to omit it, or, have a bit more high pass at the bandpass lower frequency (6db/oct more) from the wien bridge @20 hz.
OR, trying Project 197 (thx Fast Eddie D) in simulation, for the 20 hz boost
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I've been experimenting with active equalization of speakers and active bandwidth limiting. I've had great luck cascading filters, and I have found that strictly controlling the low frequency cutoff reduces distortion and greatly increases maximum SPL in real world situations.
Here's another excellent building block I've used Project 99 - Infrasonic Filter 36 dB/octave high pass filter. I used it with a hard wired shelving booster and the results were tremendous- extended bass response and way higher max SPL; what more could you want?
Here's another excellent building block I've used Project 99 - Infrasonic Filter 36 dB/octave high pass filter. I used it with a hard wired shelving booster and the results were tremendous- extended bass response and way higher max SPL; what more could you want?
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I can get ~95 db (best case) extended and equalized bass response with this speaker/ enclosure.
Subsonic, peak at bellow 20 hz, dip at around 50 hz.
And I go beyond xmax (still within xmech)....
The box will play below 80hz (the crossover not included here).
Actually there are two bass boxes (stereo), so the levels are decent for a living room
No decoupling caps, the next module (vol control) has one at the input.
The bass boost will be adjustable with a resistor matrix and ~2 db step.
A MCU and with a low pass in front will detect peak levels and push the bass boost a step down (xmax issues).
Comments how to do it better? Enclosure volume and driver are not to be changed.
Subsonic, peak at bellow 20 hz, dip at around 50 hz.
And I go beyond xmax (still within xmech)....
The box will play below 80hz (the crossover not included here).
Actually there are two bass boxes (stereo), so the levels are decent for a living room
No decoupling caps, the next module (vol control) has one at the input.
The bass boost will be adjustable with a resistor matrix and ~2 db step.
A MCU and with a low pass in front will detect peak levels and push the bass boost a step down (xmax issues).
Comments how to do it better? Enclosure volume and driver are not to be changed.
Attachments
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Where is the best place to put a trimpot, so I can find adjust the filter gain?
Now I have put 2 trimpots per filter, but due to space considerations, I want to reduce to one.
The first wien bridge is supposed to make a -3db dip @~50hz.
The second one is +6db boost @~20 hz. The original gain pot is substituted with a resistor matrix, so the total resistance of the compound 'pot' is varying.
The inverting input resistors (R3, R4 in the original circuit) are not uniform - I set them in a simulator, to adjust the boost/ dip.
Their ratio kind of controls the gain, so I put a trimpot there as well.
But again, I would like to have one adjustment trimpot per filter, at the best possible place.
Now I have put 2 trimpots per filter, but due to space considerations, I want to reduce to one.
The first wien bridge is supposed to make a -3db dip @~50hz.
The second one is +6db boost @~20 hz. The original gain pot is substituted with a resistor matrix, so the total resistance of the compound 'pot' is varying.
The inverting input resistors (R3, R4 in the original circuit) are not uniform - I set them in a simulator, to adjust the boost/ dip.
Their ratio kind of controls the gain, so I put a trimpot there as well.
But again, I would like to have one adjustment trimpot per filter, at the best possible place.
Attachments
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