Using high Q shelving to gain 10 Hz in the bass without severe drawbacks

M

Musician

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This is a trick thats often used in studios to make the soundmix more fuller and more impressive - the use of high Q shelving function to high pass the signal . This can also be implemented in a ported speaker . And as very few streamers on the market, the WiiM can do this.

This can be done with any ported loudspeaker , using the advantage of the back pressure from the tube at the tuning frequency , making the driver cone stand still and the tube makes all the sound . At the tuning frequency the sound spl advantage are about 10 dB compared to a closed box speaker .

If using a highpass high Q shelving filter with a Kef ls50 meta, centered 10-11 Hz below the tuning frequency of the speaker , you get a boost at the tuning frequency at 51 Hz making the loudspeaker sound much more potent in the bass area. The high Q filter gives you an overshoot right before the bass drops below the tuning frequency .

Simulation example with a WiiM pro and Kef ls 50 meta :

Using PEQ in the WiiM :

LS
Frequency = 40 Hz
Q = 3
Gain = - 9 dB

The Kef ls50 meta has a tuning frequency of 51 Hz . You will get a boost at that frequency about 5 dB and you will have a sharp falloff below the tuning frequency . More bass without overloading the xmax of the driver .

Ls50 meta original without shelving :

IMG_4776.jpeg
After high Q shelving it will be :

IMG_4776.jpeg


Read the whole article by Perry Marshall about high Q shelving filter here :


If you have a WiiM streamer and a ported speaker - try it , this will bring better bass in most cases.
 
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Musician said:
This is a trick thats often used in studios to make the soundmix more fuller and more impressive - the use of high Q shelving function to high pass the signal . This can also be implemented in a ported speaker .

This can be done with any ported loudspeaker , using the advantage of the back pressure from the tube at the tuning frequency , making the driver cone stand still and the tube makes all the sound . At the tuning frequency the sound spl advantage are about 10 dB compared to a closed box speaker .

If using a highpass high Q shelving filter with a Kef ls50 meta, centered 10 Hz below the tuning frequency of the speaker , you get a boost at the tuning frequency at 51 Hz making the loudspeaker sound much more potent in the bass area. The high Q filter gives you an overshoot right before the bass drops below the tuning frequency .

Example with a WiiM pro and Kef ls 50 meta :

Using PEQ :

Hipass shelving
Frequency = 41 Hz
Q = 3
Gain = - 9 dB

The Kef ls50 meta has a tuning frequency of 51 Hz . You will get a boost at that frequency about 5 dB and you will have a sharp falloff below the tuning frequency . More bass without overloading the xmax of the driver .

Ls50 meta original without shelving :

View attachment 7052
After high Q shelving it will be :

View attachment 7053


Read the whole article by Perry Marshall about high Q shelving filter here :


If you have a WiiM streamer and a ported speaker - try it , this will bring better bass in most cases.
Click to expand...
Is that the result of what you actually tried with the LS50 Meta? Or is it theoretical?

In my tests with the WiiM PEQ, LS with a high Q value can cause distortion.
 
Wiimer said:
Is that the result of what you actually tried with the LS50 Meta? Or is it theoretical?

In my tests with the WiiM PEQ, LS with a high Q value can cause distortion.
Click to expand...
Good question.
You have to find the right settings for the peq and you must know the real tuning frequency of the loudspeaker.
As with everything, it might result in worse results than without. The resulting frequency response for the meta is a simulation, but it comes from experience of real measurements on a couple of speakers, including my own.

Using this technique you will have an overshoot in the shelving filter because of the Q=3 meaning that the WiiM dsp section might be overloaded to clipping. If one uses the WiiM without volumecontrol, then it should be set to 95%. If used as digital preamp with volume regulation, theres usually no problem as long as you dont max the volume.

Here is an example with minidsp, the same can be done with WiiM.

IMG_0885.jpeg
 
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Some questions about this.

  • Where can I find the tuning frequency of my B&W 704 S2?
  • Is the difference of minus 10 Hz (51-41) a fixed value or dependent on the specific tuning frequency of a loudspeaker?
  • Also, are the values Q=3 and Gain= -9 fixed? Or a starting point for experiments

  • Would „your“ filter look like this at WiiM PEQ?

IMG_0055.jpeg
 
alpha_zulu said:
Some questions about this.

  • Where can I find the tuning frequency of my B&W 704 S2?
  • Is the difference of minus 10 Hz (51-41) a fixed value or dependent on the specific tuning frequency of a loudspeaker?
  • Also, are the values Q=3 and Gain= -9 fixed? Or a starting point for experiments

  • Would „your“ filter look like this at WiiM PEQ?

View attachment 7061
Click to expand...


Sorry for late reply :

1. At soundstage https://www.soundstagenetwork.com/i...&catid=77:loudspeaker-measurements&Itemid=153 , it looks like it is at 39 Hz .

2. No, at 20 Hz the difference are only about 5 Hz . At 80 Hz its about 20 Hz . Use the formula : *1.27.
So, If your tuning frequency of your speakers are 39 Hz , you set the shelving frequency on the WiiM at 31 Hz .
The overshoot for the high Q shelving filter will now be peaked at 39 Hz , your speakers tuning frequency.

3. Only good starting point for experimentation . With your speaker I would try:

Filter=LS Freq=31 Hz Gain= -9 Q= 3.0

(Lowering gain to - 6 will give you less bass. Q=4 will overshoot more )

4. Yes .
However, the WiiM graph do NOT show the overshoot that you have with a Q value bigger than 0.7 . This is a bit confusing.

This is how my setting is for my Markaudio speakers :

IMG_0886.png
The LS 30 Hz , gain -7 dB and Q= 3 is the dsp bass boost.
My loudspeakers tuning is 8 Hz higher than 30 Hz , at 38 Hz.

( measurement at the bass port )

IMG_4685.jpeg
 
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LS
Frequency = 31 Hz
Q = 3
Gain = - 8 dB

That is what I'am trying out at the moment. It leads to a clearly audible change in the bass range. So far I really like the result. But I still have to observe whether it has any undesirable side effects.

Question: Would it be the same effect, when I boost up the curve (around the tuning frequency) with a PK-Filter?
 
alpha_zulu said:
LS
Frequency = 31 Hz
Q = 3
Gain = - 8 dB

That is what I'am trying out at the moment. It leads to a clearly audible change in the bass range. So far I really like the result. But I still have to observe whether it has any undesirable side effects.

Question: Would it be the same effect, when I boost up the curve (around the tuning frequency) with a PK-Filter?
Click to expand...
No, not really. The group delay will be lower with high Q shelving and give you better sound because the overshoot will be also ”the other way” , functioning as a sharp high pass crossover right below the bass ports tuning point - where its needed. This will give lower distortion also in the midbass and midrange.

IMG_0887.jpeg

One drawback with your settings for the shelving ( almost the same as mine ) is that you might also benefit with a simple PEQ filter at 70 Hz , -1 dB and Q= 1. - If you experience to much bass in that area, you can try it.
 
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little extra:

With the help of A4 paper sheets, which you roll up and put into the base tube to make it slightly smaller in diameter, you can lower the tuning frequency a number of Hz, for example from 39 to 35 Hz. A different tuning of the speaker. Then you can get noticeably deeper bass, if you correct with the shelving function at the same time.
And maybe no subwoofer needed.
 
Valdo said:
Hi,
For a complete newbie with the peq.
This is my speaker (https://www.soundstagenetwork.com/measurements/speakers/bw_cm1/) please tell me how to use your calculation for the q shelf.
Thanks!
Click to expand...
Nothing against this nice bass extension trickery, for a newbie to PEQ with no measuring equipment I would rather recommend you get a cheap subwoofer for your WiiM Amp and have it all: Deeper bass, less distortion from your small bookshelf speakers, more dynamic headroom for your amp and (soon to come) automatic room correction.

Applying any form of bass EQ will increase speaker distortion, eat up more amplifier power and most importantly will be shooting in the dark if you have to rely on some 3rd party anechoic measurements of your speaker.

EQ comes for free, that's the only obvious upside.
 
alpha_zulu said:
Same question here.
Click to expand...
By looking at the impedance curve. The blue arrow is the tuning point, give or take +-3 Hz.
Another thing one can do is to use a slow sine sweep from 20-80 Hz , the cone will stand still and the basstube will bring lots of air at the tuning (fb) frequency.

If the box leaks air, the tuning frequency might differ a bit ( compared to the impedance curve ) .
The picture shows a ported speaker, where you always have two impedance peaks.
IMG_0889.jpeg
 
harkpabst said:
Nothing against this nice bass extension trickery, for a newbie to PEQ with no measuring equipment I would rather recommend you get a cheap subwoofer for your WiiM Amp and have it all: Deeper bass, less distortion from your small bookshelf speakers, more dynamic headroom for your amp and (soon to come) automatic room correction.

Applying any form of bass EQ will increase speaker distortion, eat up more amplifier power and most importantly will be shooting in the dark if you have to rely on some 3rd party anechoic measurements of your speaker.

EQ comes for free, that's the only obvious upside.
Click to expand...
Having a step highpass filter right below the tuning frequency of the speaker lowers the distortion in a ported speaker, also at higher frequencies. Please read the article again. And many cheap subwoofers plays bass in a bad way , and you always need two subwoofers for good fidelity and integration. With two stereo subwoofers you will also need a stereo crossover, both HP and LP.

Two good subwoofers ( most likely expensive ) and a separate stereo crossover containing both HP and LP filtering is ofcourse better , but will take up more space.
 
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Musician said:
Having a step highpass filter right below the tuning frequency of the speaker lowers the distortion in a ported speaker, also at higher frequencies. Please read the article again. And many cheap subwoofers plays bass in a bad way , and you always need two subwoofers for good fidelity and integration. With two stereo subwoofers you will also need a stereo crossover, both HP and LP.

Two good subwoofers ( most likely expensive ) and a separate stereo crossover containing both HP and LP filtering is ofcourse better , but will take up more space.
Click to expand...
I wholeheartedly disagree to most of these statements.

The article by Perry Marshall describes an alternative approach to designing ported speakers, it's not a cookbook for "improving" existing designs. While certain aspects surely apply in common, the pros and cons must be evaluated.

I don't share your comments on subwoofer usage at all. From theory and even more from practical experience one single subwoofer (even a very cheap one) can greatly improve real world performance in a typical home, if high pass filtering is applied to the mains. @Valdo already owns a WiiM Amp that is capable of this exercise, so a sub is all that is needed.
 
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I'm not an expert, but this kind of reminds me of ECU remaps in cars. "No downsides! Goes faster, vroom vroom! Even uses less fuel!"

"But since there are car fleet CO2 penalties for manufacturers, at least in EU, and using less fuel means less CO2, why don't car/engine manufacturers do it?"

"It's a conspiracy."
 
In my opinion, this is a judgement call to balance between quantity (more bass) and quality (low distortion). So, it depends on your preference, budget, space, and other factors. If space allows, I would go with subwoofer and proper crossover between subwoofer and main speakers.
 
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