Center speaker advice: Is timbre matching real?

[kawauso]

I like your post because it’s so typical. Seriousness gets completely drowned in audiological dogmas. You don’t even address the response you asked from me. You say a speaker is ruled by non-linear thresholds, breakup modes, and material limits. Well, good for you—mine isn’t. I payed for it. Btw: Did you give some numbers for any comparison?


Who mentioned non-linearities? We were talking about resonances, which, in real-world usage, are of course always linear. But as I said, typical—I kind of like that.

Please try playing your R11 at a level that reaches about 115 dB at the listening position.
The behaviour you observe will answer the question immediately.
You will probably need around 500 W, so drive them with something like a Hypex-based amplifier.
Avoid boosting the low frequencies (even though your theory says it should be fine, just to be safe).
Also, please use music for this test rather than test tones, just in case.

 

[dlaloum]

What @Heinrich display is a classic case of "linear thinking", as if the whole world acts like linear systems.

What does a high Q resonance do? It magnifies the amplitude by many many times at the natural frequency. Can a real system do that? Probably not as it will likely go nonlinear well before it can reach the resonance amplitude as predicted by linear analyses. The differences of small signal vs large (i.e. real) signal.

Another one is diaphragm breakup. It is a case of structural buckling, and it doesn't happen until a certain critical limit is exceeded, just like a slender column buckles when the compressive load exceeds the critical buckling load. Is that a "resonance"? Depends on how you define it. Buckling is studied using modal analyses, just like room modes. Are room mode resonances?

The reason resonances are difficult is because - when discussing speakers - they are typically NOT simple resonances where the phase/amplitude/Q adjustments are well understood, but include complex behaviours that although theoretically modellable, are not practically so...

Diaphragm breakup is an example - other simpler cabinet resonances, are further subject to variable damping, reflection, and refraction, making simple resonance models relatively innefective in managing them.

Having said that, I guess at some point, our processing power, and modeling capabilities may increase to the point where we can model and understand some of these complex behaviours (eg Diaphragm breakup) along with the manner in which they propagate in the room, and therefore actively cancel or remedy them.... and that process will then end up being lumped in with others and generically called EQ...

Dirac ART currently provides an example of how a complex room system can potentially be managed/improved through such methods, and without a doubt such methods will multiply, and become more common over time.
(ART does not pretend to be a truly active system, with microphones in the room and active feedback response correcting in real time - in theory, that would ultimately be the ideal.... and might be what is required to correct the more complex distortions...)

P.S. I apologise for my colloquial and imprecise use of the term "resonance" - similarly I would point to the almost universal tendency to call Dirac ART "RoomEQ" - it isn't EQ at all (strictly speaking)... although it does come layered on top of Dirac Live, which is a sophisticated "true EQ" tool.
Sometimes we use the precise scientific/engineering term, and sometimes we use a colloquial term.... and just to be confusing the word is the same and has two differing meanings... effectively we have a homograph, and we can get lost in the difference between the two meanings.

 

[Heinrich]

The reason resonances are difficult is because - when discussing speakers - they are typically NOT simple resonances where the phase/amplitude/Q adjustments are well understood, ...

Diaphragm breakup is an example - other simpler cabinet resonances, ...

No, this conceptual confusion stemming from mere lack of knowledge is not acceptable. And now there’s also a bit of argumentative showboating being added. With audio-talk that’s practically inevitable.

Originally, the discussion was about Dr. Toole’s statement that resonances are the first thing to avoid. The word resonance was reinterpreted here, and that’s what I argued against in post #111. I have a formal education that unfortunately won’t let me leave things alone.

Diaphragm breakup is generally well understood, while cabinet resonances tend to be exaggerated — and in most cases they aren’t resonances in the sense of independent oscillations, but simply sound transmission. But where are you supposed to begin when terminology gets aggressively redefined by glossy magazines and is promoted by hearsay? I can only hope that I’m wrong about this.

 

[drodgers]

The overloaded definition here is just adding confusion: Let's avoid the word 'resonance' from now on.

My attempt to synthesise:

At certain frequencies, most transducer (speaker) designs will exhibit very high gain due to feedback loops from self-reinforcing reflections (either mechanical or electronic). The resulting high amplitude oscillation can drive the system into non-linear response regimes for a range of reasons: diaphragm breakup; cabinet warping; thermal effects etc.

EQ can be used to compensate by suppressing those frequencies in the input signal and avoiding the non-linear response regime. If the EQ isn't perfect (eg. not enough filters), or the input level is high enough to enter those non-linear regimes even with the EQ'ed input signal, then the result will still be significant distortion.

Hence, highly electrically and mechanically robust speaker designs which raise the ceiling of the linear response regime, combined with careful reflection control, damping, and crossover design to minimise feedback loops will maximise the linear operating range. Such designs are typically expensive (lots of rigid materials, tight tolerances, curves which are hard to manufacture, generated by experienced engineers using computer modelling and iterative testing etc.). Less robust speakers can generally be EQ'ed into a smooth response, but will need to be volume-limited to avoid distortion, which can limit dynamic range.

@Heinrich and @kawauso, do you both agree with that?

 

[kawauso]

The overloaded definition here is just adding confusion: Let's avoid the word 'resonance' from now on.

My attempt to synthesise:

At certain frequencies, most transducer (speaker) designs will exhibit very high gain due to feedback loops from self-reinforcing reflections (either mechanical or electronic). The resulting high amplitude oscillation can drive the system into non-linear response regimes for a range of reasons: diaphragm breakup; cabinet warping; thermal effects etc.

EQ can be used to compensate by suppressing those frequencies in the input signal and avoiding the non-linear response regime. If the EQ isn't perfect (eg. not enough filters), or the input level is high enough to enter those non-linear regimes even with the EQ'ed input signal, then the result will still be significant distortion.

Hence, highly electrically and mechanically robust speaker designs which raise the ceiling of the linear response regime, combined with careful reflection control, damping, and crossover design to minimise feedback loops will maximise the linear operating range. Such designs are typically expensive (lots of rigid materials, tight tolerances, curves which are hard to manufacture, generated by experienced engineers using computer modelling and iterative testing etc.). Less robust speakers can generally be EQ'ed into a smooth response, but will need to be volume-limited to avoid distortion, which can limit dynamic range.

@Heinrich and @kawauso, do you both agree with that?

Broadly speaking, I agree with your summary.
Within the linear operating range, EQ can control amplitude (and phase) quite effectively.
One thing it cannot control, however, is directivity: the radiation pattern is set by driver size, geometry, and breakup behaviour, so no amount of EQ will turn poor off-axis behaviour into good directivity.

That’s why I see EQ as a powerful finishing tool for a well-designed loudspeaker, not a replacement for good mechanical design and controlled directivity.

 

[drodgers]

Yep, totally agree on directivity.

 

[kawauso]

The reason resonances are difficult is because - when discussing speakers - they are typically NOT simple resonances where the phase/amplitude/Q adjustments are well understood, but include complex behaviours that although theoretically modellable, are not practically so...

Diaphragm breakup is an example - other simpler cabinet resonances, are further subject to variable damping, reflection, and refraction, making simple resonance models relatively innefective in managing them.

Having said that, I guess at some point, our processing power, and modeling capabilities may increase to the point where we can model and understand some of these complex behaviours (eg Diaphragm breakup) along with the manner in which they propagate in the room, and therefore actively cancel or remedy them.... and that process will then end up being lumped in with others and generically called EQ...

Dirac ART currently provides an example of how a complex room system can potentially be managed/improved through such methods, and without a doubt such methods will multiply, and become more common over time.
(ART does not pretend to be a truly active system, with microphones in the room and active feedback response correcting in real time - in theory, that would ultimately be the ideal.... and might be what is required to correct the more complex distortions...)

P.S. I apologise for my colloquial and imprecise use of the term "resonance" - similarly I would point to the almost universal tendency to call Dirac ART "RoomEQ" - it isn't EQ at all (strictly speaking)... although it does come layered on top of Dirac Live, which is a sophisticated "true EQ" tool.
Sometimes we use the precise scientific/engineering term, and sometimes we use a colloquial term.... and just to be confusing the word is the same and has two differing meanings... effectively we have a homograph, and we can get lost in the difference between the two meanings.

ART is a form of EQ, and it cannot change the physical limits of the speakers or the room.
But compared to traditional EQ or SIMO-type correction, MIMO processing really does feel like a different category.

What ART does is treat all speakers, all subwoofers, and the room as one integrated acoustic system.
Each channel influences the behaviour of the others, and the result is a complete reconstruction of the waveform at the listening position.

If you solo the signal sent to each speaker or subwoofer, the frequency and phase responses look chaotic, almost like a puzzle with no obvious pattern.
None of them resemble a “normal” loudspeaker response.

But when everything plays together, that chaotic puzzle suddenly locks into place.
Across the listening area and throughout the room, the combined result behaves in a way that genuinely feels magical.

 

[Heinrich]

...
Those distortions, are by their nature, not really subject to EQ - if you reduce the response at a resonance peak, you will also reduce the desired signal... mostly we have to live with the resonances.

Those resonances / flaws therefore become the "signature" of a speaker... and we have to live with them or live with compromises made to reduce their impact... no 2 compromises are alike, and different people find different compromises they are willing to live with.

This comment was of concern, when I tried to clarify the terminology. (Not picking on him, for sure.) It shows where it goes when terms are misused - becoming unable to resolve the issue by dismissing the most appropriate tool.

EQ can be used to compensate by suppressing those frequencies in the input signal and avoiding the non-linear response regime.

While peaks in frequency response as such are that primary problem, according to Dr. Toole.

@Heinrich and @kawauso, do you both agree with that?

I'm o/k with even not discussing the wording further. Just for the fun of it:

Aperiodic Resonances - Theory and Applications

This book presents various types of aperiodic resonances in the form of a complete theoretical framework for the first time

link.springer.com

Aperiodic Resonances - a full book, academic ...

Finally the debate has shifted gears to "directivity" anyway, the new hot topic?

 

[dlaloum]

Broadly speaking, I agree with your summary.
Within the linear operating range, EQ can control amplitude (and phase) quite effectively.
One thing it cannot control, however, is directivity: the radiation pattern is set by driver size, geometry, and breakup behaviour, so no amount of EQ will turn poor off-axis behaviour into good directivity.

That’s why I see EQ as a powerful finishing tool for a well-designed loudspeaker, not a replacement for good mechanical design and controlled directivity.

I would argue that it is not "controlled" directivity so much as maintaining the same spectral F/R throughout - Omni's can do an excellent job, maintaining the same f/r from all sides of a speaker - There is an implied assumption that "controlled" directivity (often a synonym for "limited" directivity) is part of the "ideal"

Personally I have always had a preference for speakers with a broad directivity, electrostatic dipoles/bipoles, or the Gallo Nucleus speakers with the CDT tweeter, and a semi-omni radiation pattern.

Differing speaker directivity, does change how a speaker needs to be positioned in a room - you need to be more conscious of the reflections coming from all different angles - but the potential for a naturally massive soundstage is huge ... and if you manage those reflections properly, then you can maintain imaging while gaining the soundstage.... lovely!

And no EQ will help you adjust this!

However, MIMO techniques can allow for beamforming - used in Radio / WiFi fields, and in theory, such techniques could be applied to audio...
Something like ART, with these type of techniques used, could potentially take an omni design and through DSP, shape the actual audio beam - either resolving or amelioration directivity issues...

 

[dlaloum]

This comment was of concern, when I tried to clarify the terminology. (Not picking on him, for sure.) It shows where it goes when terms are misused - becoming unable to resolve the issue by dismissing the most appropriate tool.


While peaks in frequency response as such are that primary problem, according to Dr. Toole.


I'm o/k with even not discussing the wording further. Just for the fun of it:

Aperiodic Resonances - Theory and Applications

This book presents various types of aperiodic resonances in the form of a complete theoretical framework for the first time

link.springer.com

Aperiodic Resonances - a full book, academic ...

Finally the debate has shifted gears to "directivity" anyway, the new hot topic?

I am somewhat aware of resonances, having modelled cantilever behaviour in phono cartridges along with how loading can adjust by correcting resonances (along with the relationship between phase and frequency response in "natural" systems aka minimum phase)

Many natural systems have minimum phase resonances - which can be controlled simply with EQ, without messing up phase/timing

but some complex "distortions" (avoiding the term resonance) are not minimum phase, and therefore the frequency/phase relationship can get scrambled - with no simple way of bringing them back into alignment.

 

[Oddball]

@dlaloum and @kawauso - would not even argue in this thread. Absolutely pointless. Achieving perfection will be out of our reach and not sure if any of the recordings would actually warrant that.

What you guys have is probably so much better that the responders to this thread so if I was you - I would reinforce the science part of it and provide proof that what we do matters greatly.

 

[kawauso]

I would argue that it is not "controlled" directivity so much as maintaining the same spectral F/R throughout - Omni's can do an excellent job, maintaining the same f/r from all sides of a speaker - There is an implied assumption that "controlled" directivity (often a synonym for "limited" directivity) is part of the "ideal"

Personally I have always had a preference for speakers with a broad directivity, electrostatic dipoles/bipoles, or the Gallo Nucleus speakers with the CDT tweeter, and a semi-omni radiation pattern.

Differing speaker directivity, does change how a speaker needs to be positioned in a room - you need to be more conscious of the reflections coming from all different angles - but the potential for a naturally massive soundstage is huge ... and if you manage those reflections properly, then you can maintain imaging while gaining the soundstage.... lovely!

And no EQ will help you adjust this!

However, MIMO techniques can allow for beamforming - used in Radio / WiFi fields, and in theory, such techniques could be applied to audio...
Something like ART, with these type of techniques used, could potentially take an omni design and through DSP, shape the actual audio beam - either resolving or amelioration directivity issues...

I prefer speakers with a narrower and more consistent directivity pattern, roughly within ±30 to 50 degrees, rather than designs with very wide radiation like omnis. I also own high-Preference-Score speakers such as the Revel F228Be and the Ascend Sierra-LX, but for my taste their dispersion is a bit too broad. I enjoy listening on-axis with speakers like JBL or KEF that have tighter and more coherent directivity and provide strong point-focus imaging.

That said, the low frequencies in my system are not actively directivity-controlled, so they behave in a largely omnidirectional manner in practice. dlaloum’s idea of shaping a speaker’s directivity through DSP is fascinating, but even if it is theoretically possible, it would likely require a very large number of drivers and raise major compatibility issues.

Still, I feel that something similar could be achievable up to around 300 Hz with ART. Trinnov’s claims about beamforming-like effects sound more like marketing than something that actually works in practice. If true directivity control ever becomes possible, I would first want it to create a physically convincing phantom center so that a center speaker becomes unnecessary. That seems extremely difficult, though.

 

[kawauso]

@dlaloum and @kawauso - would not even argue in this thread. Absolutely pointless. Achieving perfection will be out of our reach and not sure if any of the recordings would actually warrant that.

What you guys have is probably so much better that the responders to this thread so if I was you - I would reinforce the science part of it and provide proof that what we do matters greatly.

Oddball, thank you. I can’t really see him on my side of the screen.
But talking with dlaloum is fun for me.
We’ve wandered pretty far off the original topic though.
Anyway, I left a small comment about the center speaker just in case. lol

 

[Oddball]

Both you and @dlaloum are what I enjoy on the forum. So please keep the good stuff coming. When someone quotes me a 50 page book, I do not follow through.

I would describe myself as thorough but a bit shallow with a twist of knowing what makes it or breaks it within the time I can spend of the forums. There is life after all.

 

[7Tiger]

I prefer speakers with a narrower and more consistent directivity pattern, roughly within ±30 to 50 degrees, rather than designs with very wide radiation like omnis. I also own high-Preference-Score speakers such as the Revel F228Be and the Ascend Sierra-LX, but for my taste their dispersion is a bit too broad. I enjoy listening on-axis with speakers like JBL or KEF that have tighter and more coherent directivity and provide strong point-focus imaging.

...

If true directivity control ever becomes possible, I would first want it to create a physically convincing phantom center so that a center speaker becomes unnecessary. That seems extremely difficult, though.

A good phantom center is almost (if not totally) impossible with your preferred kind of speakers, only those with wider dispersion are capable of creating that effect