Attenuating the entire Frequency response curve to the level of the lowest frequency.

[abdo123]

I’ve been playing around with some old speakers of mine and I have realized that (without EQ) the frequency response will never resemble anything flat in anyway.

I had the idea of just reducing the loudness of the entire frequency response curve to the level of the lowest frequency on the curve.

I ignored the room modes and found that the high frequencies were the lowest (Around -5dB, I sit off axis). And then i just constructed the filters in REW to equalize everything to that level (after ignoring the warning).

Why no one does this? I haven’t heard of it before so far. Sure i have to raise the volume a bit to compensate but it sounds really good.

 

[Chromatischism]

It's effectively the same as boosting the dips to flat.

 

[abdo123]

It's effectively the same as boosting the dips to flat.

It is much easier to tell people to do what i did than to cement their chimneys and barricade their windows.

Why this is rarely recommended?

 

[Chromatischism]

How were measurements taken that informed you on what to do?

Without knowing the speaker's directivity vs frequency, it's very hard to predict how to EQ in the treble region. The only way is to just do it by ear in-room in the spot where you will listen.

 

[abdo123]

How were measurements taken that informed you on what to do?

Without knowing the speaker's directivity vs frequency, it's very hard to predict how to EQ in the treble region. The only way is to just do it by ear in-room in the spot where you will listen.

REW and UMIK-1, basically text book stuff.

 

[Matias]

It is much easier to tell people to do what i did than to cement their chimneys and barricade their windows.

Why this is rarely recommended?

Good question.
If you leave the target curve in the middle and elevate and reduce dips and peaks, later you have to add a negative preamp amount to compensate for the peaks not clipping. This should impact SNR the same as just attenuating all frequencies. Specially with 64 bit precision, should be the same I guess.
Let's leave to the experts to answer.

 

[Wayne A. Pflughaupt]

This post should explain things pretty well. The bottom line is that merely boosting the lows will get you the same thing, as far as headroom goes (assuming that’s your reasoning for trying something like this).

https://www.avsforum.com/threads/did-i-eq-correctly.1387919/#post-21516881

But, there is more. The situation is that equalizers use phase shift to accomplish what they do. Why is that relevant? Because peaks and troughs in frequency response are the result of phase shift. It takes phase shift to fix phase shift, according to professionals in the pro-audio field.

With regular equalizing to address the room or minor speaker deficiencies, moving the Target to an appropriate location between the peaks and troughs means you are using the equalizer’s phase shift to counteract the phase shift that caused said peaks and troughs. To quote from the article in the previous link, “Associated with each change in amplitude is a corresponding change in phase response. In fact, it can be argued that phase shift is the stuff that causes amplitude changes. Amplitude, phase and time are all inextricably mixed in the physics of sound. One does not exist without the others.”

While it's true that trying to compensate for a speaker's lack of extension isn't a phase issue, dragging down the entire curve like you’re considering – that makes it a phase shift issue. That’s using the equalizer as a de-facto level control. And in doing so the equalizer is introducing phase shift that’s not addressing any phase shift. Headroom issues aside, I don’t expect the end result will sound nearly as good as if equalizing had been done properly. I like what a poster at AV NIRVANA said recently: “I’ve had the feeling that my overzealous EQ attempts fixed the graphs but killed the sound.”

Regards,
Wayne A. Pflughaupt

 

[abdo123]

This post should explain things pretty well. The bottom line is that merely boosting the lows will get you the same thing, as far as headroom goes (assuming that’s your reasoning for trying something like this).

https://www.avsforum.com/threads/did-i-eq-correctly.1387919/#post-21516881

But, there is more. The situation is that equalizers use phase shift to accomplish what they do. Why is that relevant? Because peaks and troughs in frequency response are the result of phase shift. It takes phase shift to fix phase shift, according to professionals in the pro-audio field.

With regular equalizing to address the room or minor speaker deficiencies, moving the Target to an appropriate location between the peaks and troughs means you are using the equalizer’s phase shift to counteract the phase shift that caused said peaks and troughs. To quote from the article in the previous link, “Associated with each change in amplitude is a corresponding change in phase response. In fact, it can be argued that phase shift is the stuff that causes amplitude changes. Amplitude, phase and time are all inextricably mixed in the physics of sound. One does not exist without the others.”

While it's true that trying to compensate for a speaker's lack of extension isn't a phase issue, dragging down the entire curve like you’re considering – that makes it a phase shift issue. That’s using the equalizer as a de-facto level control. And in doing so the equalizer is introducing phase shift that’s not addressing any phase shift. Headroom issues aside, I don’t expect the end result will sound nearly as good as if equalizing had been done properly. I like what a poster at AV NIRVANA said recently: “I’ve had the feeling that my overzealous EQ attempts fixed the graphs but killed the sound.”

Regards,
Wayne A. Pflughaupt

Thank you for your response! It will take me some time to digest.

The speakers are from the 70s, in a time when even the manufacturers measurements were probably way off reality. So this whole experience has been honestly nerve wrecking.

99.99% of people don’t live in an exceptionally wide under ground bunker, so I really gave up on the idea of perfection some time ago.

Doing what i did brought me the closest to proper sound image, as female vocals are properly infront of instrumentals now.

 

[andreasmaaan]

This post should explain things pretty well. The bottom line is that merely boosting the lows will get you the same thing, as far as headroom goes (assuming that’s your reasoning for trying something like this).

https://www.avsforum.com/threads/did-i-eq-correctly.1387919/#post-21516881

But, there is more. The situation is that equalizers use phase shift to accomplish what they do. Why is that relevant? Because peaks and troughs in frequency response are the result of phase shift. It takes phase shift to fix phase shift, according to professionals in the pro-audio field.

With regular equalizing to address the room or minor speaker deficiencies, moving the Target to an appropriate location between the peaks and troughs means you are using the equalizer’s phase shift to counteract the phase shift that caused said peaks and troughs. To quote from the article in the previous link, “Associated with each change in amplitude is a corresponding change in phase response. In fact, it can be argued that phase shift is the stuff that causes amplitude changes. Amplitude, phase and time are all inextricably mixed in the physics of sound. One does not exist without the others.”

While it's true that trying to compensate for a speaker's lack of extension isn't a phase issue, dragging down the entire curve like you’re considering – that makes it a phase shift issue. That’s using the equalizer as a de-facto level control. And in doing so the equalizer is introducing phase shift that’s not addressing any phase shift. Headroom issues aside, I don’t expect the end result will sound nearly as good as if equalizing had been done properly. I like what a poster at AV NIRVANA said recently: “I’ve had the feeling that my overzealous EQ attempts fixed the graphs but killed the sound.”

Regards,
Wayne A. Pflughaupt

Sorry if I’ve misunderstood your post, but... If minimum-phase EQ is used, the phase response of the output will be the same if the amplitude response is the same, regardless whether that amplitude response was achieved by boosting dips or lowering peaks.

The reason the phase responses of the two outputs you used as examples in the AVS forum post were different is simply that the amplitude responses were different.

If I understood the OP here correctly, on the other hand, they’re talking about using different (minimum-phase) filters to achieve an identical amplitude response. In such circumstances, the phase response will also be identical.

 

[escape2]

It is much easier to tell people to do what i did than to cement their chimneys and barricade their windows.

Why this is rarely recommended?

It is widely recommended. It's basically only using negative dB EQ filters and never using positive dB filters to avoid overdriving.

MathAudio Room EQ does this.

 

[Chromatischism]

It is widely recommended. It's basically only using negative dB EQ filters and never using positive dB filters to avoid overdriving.

But he raised the level afterwards, so the result is the same.

It's like going in reverse before going forward, or going forward before going in reverse

 

[abdo123]

But he raised the level afterwards, so the result is the same.

It's like going in reverse before going forward, or going forward before going in reverse

I raised the volume in the Analog domain using my Pre-Amp.

 

[ernestcarl]

That Rane article Wayne linked to was interesting.

“Serious correcting requires sharp constant-Q performance, among many other things.

Only by adding many precise, narrow phase shift and amplitude corrections do you truly start equalizing a system's blurred phase response.”

This may be off-topic now — so you can ignore this — but what would be a good example of a ‘blurred’ phase response?

Has anyone measured speakers prior application of ‘serious’ correction that had this kind of attribute?

 

[Wayne A. Pflughaupt]

I expect that “blurred phase response” is what you have before correction. Like maybe the comb filtering you see in the upper frequencies of a graph before smoothing (admittedly, that’s probably an extreme example...).

Modern auto-room correction would probably come closest to being able to address room issues with “many precise, narrow phase shift and amplitude corrections.” It’s just not feasible with manual EQ. I’d love to see an unsmoothed “before” and “after” graph from Dirac et al. to see how comb filtering looks afterwards.

Regards,
Wayne A. Pflughaupt

 

[ernestcarl]

I expect that “blurred phase response” is what you have before correction. Like maybe the comb filtering you see in the upper frequencies of a graph before smoothing (admittedly, that’s probably an extreme example...).

Modern auto-room correction would probably come closest to being able to address room issues with “many precise, narrow phase shift and amplitude corrections.” It’s just not feasible with manual EQ. I’d love to see an unsmoothed “before” and “after” graph from Dirac et al. to see how comb filtering looks afterwards.

Regards,
Wayne A. Pflughaupt

Ah, so at a distance with reflections and everything? I was thinking they were describing something more inherent in the system design (i.e. phase is blurred even before the room is added into the equation — necessitating the serious correction.)