Dr. Toole's - A Rational Approach To Calibrations

[dualazmak]

The most important point IMO is that the non-minimum phase response should not be corrected. @Curvature made a very important point - automated software removes your control of what should/should not be corrected. IMO it's a good crutch for beginners, and it will produce acceptable results for some people. But there is a strong likelihood that it will do something inappropriate and degrade the sound.

(I added bold and underline.)

For myself at least, I agree with your points.

I have always been hesitant to depend on “blackbox type” (to me!) automated software for room mode and other corrections. I would prefer to use tuning procedures (in digital domain, analog domain, and room acoustic treatments) that are "understandable" to me who have rather naive and limited knowledge of audio science...

 

[Justdafactsmaam]

I can't see how that has anything to do with the point i raised, that speakers are not anechoically measured and tuned to a one 1 meter distance...(again unless very small).

Oh right. The exception would be electrostatic speakers. They sound the same from 1 foot away as they do 10 feet away other than the uniform attenuation

If anything, for a highly directional speaker, it is even more important to measure in the acoustic far-field.
because a highly directional speaker inevitably requires a wave guide of some sorts, which means it's a multi-way needing further driver sections.....

Not all of them. See above.

 

[gnarly]

Oh right. The exception would be electrostatic speakers. They sound the same from 1 foot away as they do 10 feet away other than the uniform attenuation

Aah, electrostats ...good point/example.
I've never really figured out what's the right way and distance to measure them. In fact, I've had to measure them up close to get sensible readings.
As they obey line array math in both the vertical and horizontal dimensions, I guess we need some "plane array" math lol.
I see them as highly directional, but from every location on their planar surface, radiating perpendicularly out.
I think the perpendicular HF/VHF phenom occurs, because only a continuous planar diaphragm (or a ribbon), has the tiny c2c spacing necessary for HF/VHF to behave as a true line source.

Line arrays without a ribbon section, that reply on conventional HF/VHF drivers, are also a problem to measure vs distance, ime.
Multiple arrivals independent of coherent summations,

Circling back to my opening point....all I was trying to say is that I think it's a big mistake to believe measurements are routinely made at 1m.
Measurements, for all types of speakers, are much more complicated than they appear on the surface, imho.

 

[DavidMcRoy]

Aah, electrostats ...good point/example.
I've never really figured out what's the right way and distance to measure them. In fact, I've had to measure them up close to get sensible readings.
As they obey line array math in both the vertical and horizontal dimensions, I guess we need some "plane array" math lol.
I see them as highly directional, but from every location on their planar surface, radiating perpendicularly out.
I think the perpendicular HF/VHF phenom occurs, because only a continuous planar diaphragm (or a ribbon), has the tiny c2c spacing necessary for HF/VHF to behave as a true line source.

Line arrays without a ribbon section, that reply on conventional HF/VHF drivers, are also a problem to measure vs distance, ime.
Multiple arrivals independent of coherent summations,

Circling back to my opening point....all I was trying to say is that I think it's a big mistake to believe measurements are routinely made at 1m.
Measurements, for all types of speakers, are much more complicated than they appear on the surface,

Aah, electrostats ...good point/example.
I've never really figured out what's the right way and distance to measure them. In fact, I've had to measure them up close to get sensible readings.
As they obey line array math in both the vertical and horizontal dimensions, I guess we need some "plane array" math lol.
I see them as highly directional, but from every location on their planar surface, radiating perpendicularly out.
I think the perpendicular HF/VHF phenom occurs, because only a continuous planar diaphragm (or a ribbon), has the tiny c2c spacing necessary for HF/VHF to behave as a true line source.

Line arrays without a ribbon section, that reply on conventional HF/VHF drivers, are also a problem to measure vs distance, ime.
Multiple arrivals independent of coherent summations,

Circling back to my opening point....all I was trying to say is that I think it's a big mistake to believe measurements are routinely made at 1m.
Measurements, for all types of speakers, are much more complicated than they appear on the surface, imho.

Even among electrostatics there are variations with regard to radiation geometry. The Acoustat Spectra series are among a number of ESLs with electrically curved, as in their case, or more commonly physically curved diaphragms.

 

[Justdafactsmaam]

I don't want headphone effect, keeping it in order with good clarity and RT60 decay times is fine with me. I initially forgot to mantion ISO 3382-1 (back to front refractions ratio) importance which are also very hard to improve in normal environment (small to medium sized room).

I don’t want a headphone effect either. Thankfully Im not getting it

 

[AudioJester]

I don’t want a headphone effect either. Thankfully Im not getting it

Yeah, but you had to use a very expensive solution to get there......

 

[Justdafactsmaam]

Yeah, but you had to use a very expensive solution to get there......

Yes. I’m aiming at state of the art. I wish that came cheap. I take it where it does

 

[AudioJester]

Yes. I’m aiming at state of the art. I wish that came cheap. I take it where it does

I guess thats one of the problems with DSP, we often try to correct things rather than address the underlying problem.

While a realise it does more, spending another $6-7k to fix a headphone like sweet spot for speakers seems absurd to me.
But then again, if your happy, thats all that counts. However, i would talk others out of going down that path and pick speakers that can be polished by dsp but not be critically dependent on dsp, particularly when spending $10k plus for speakers.

 

[Justdafactsmaam]

I guess thats one of the problems with DSP, we often try to correct things rather than address the underlying problem.

While a realise it does more, spending another $6-7k to fix a headphone like sweet spot for speakers seems absurd to me.

I’m not sure I follow you.

But then again, if you’re happy, thats all that counts. However, i would talk others out of going down that path and pick speakers that can be polished by dsp but not be critically dependent on dsp, particularly when spending $10k plus for speakers.

My speakers are not dependent on the DSP. However they are state of the art when used correctly and synergistic with the specific DSP that is also IMO state of the art. It was a cohesive plan of a speaker/room/DSP system that all push the envelope individually and work ideally together. A different speaker with a wider radiation pattern would have been inferior.

 

[ZolaIII]

I don't use anything special, average bookshelf's with plane silk tweater and usual problem with not great crossover and usually bad ported design. I use them with port's plugged, close to back wall and with two 10" closed box sub's. They stand on each other's and are separated and isolated from each other by thick silicone seaters. Room is relatively small and half treated. Signal processing is done on PC in 64 bit FP base is JRiver added with plugins (MConvolutionEZ and MFreeformPhase along with PTEq-X) all free. Rest of the system also ain't anything special a mid range Yamaha and calibration mic. So it's how I do it respecting physis, placement and doing DSP-ing comprehensive and If I can do it so can you.

 

[gnarly]

"Even among electrostatics there are variations with regard to radiation geometry. The Acoustat Spectra series are among a number of ESLs with electrically curved, as in their case, or more commonly physically curved diaphragms."

@ DavidMcRoy,

Yes, for sure. So many designs have tried to change the flat panel perpendicular radiation pattern, huh?
I still have a pair of Acoustat-X with the 3 angled sections, and the ML CLS.
Damn I love 'stats"....with a love not way far behind my DIY synergy/unity horns..

 

[Justdafactsmaam]

"Even among electrostatics there are variations with regard to radiation geometry. The Acoustat Spectra series are among a number of ESLs with electrically curved, as in their case, or more commonly physically curved diaphragms."

@ DavidMcRoy,

Yes, for sure. So many designs have tried to change the flat panel perpendicular radiation pattern, huh?
I still have a pair of Acoustat-X with the 3 angled sections, and the ML CLS.
Damn I love 'stats"....with a love not way far behind my DIY synergy/unity horns..

You still have the CLSs? I miss mine. Best looking speakers of all time. And enjoyable sound to boot

 

[gnarly]

You still have the CLSs? I miss mine. Best looking speakers of all time. And enjoyable sound to boot

Yes, although in a closet.
With the right material in the right room, they do have a bit of magic, huh?

 

[krabapple]

So, I have my own take-away from Dr. Toole's advice. Buy good speakers. Or if your wife won't let you, do your best with your existing speakers. Apply a broadband low-Q equalization to the upper frequencies if necessary. Pay attention to the off-axis response. And finally, do not correct for a single point in space.

I would only add to this excellent summmary that if you have 'good speakers' but because of distance issues still need to apply high frequency EQ -- if you use one of the most popular speaker correction DSPs (Audyssey) , you actually can't do it because the DSP shuts off the broadband/low Q 'tone controls' of the AVR. This also means that a per-song/album adjustment of the (often wonky) recorded treble or bass is out of the question (a state of affairs Dr. Toole laments), by that means, at least.

 

[ooheadsoo]

I would only add to this excellent summmary that if you have 'good speakers' but because of distance issues still need to apply high frequency EQ -- if you use one of the most popular speaker correction DSPs (Audyssey) , you actually can't do it because the DSP shuts off the broadband/low Q 'tone controls' of the AVR. This also means that a per-song/album adjustment of the (often wonky) recorded treble or bass is out of the question (a state of affairs Dr. Toole laments), by that means, at least.

You can use tone controls if you turn off Audyssey DEQ.

 

[dualazmak]

You can use tone controls ....

Yes, as for safe and flexible tone controls (or I can say "relative gain controls among the multiple SP drivers"), my stance (policy) at least, is that we are encouraged to utilize the "best combination" of "DSP configuration in digital domain" and "analog domain tone controls using HiFi-grade preamplifiers and/or integrated amplifiers".

We need to note (and to respect for) that analog domain tone controls (relative gain controls among the multiple SP drivers) give no effect nor influence at all on the upstream DSP configuration (XO/EQ/Gain/Phase/Polarity/Group-Delay). I myself believe that this is a great merit of flexible tone controls in analog domain. We know well, on the other hand, in case if we would like to do the "tone/gain controls" only within DSP configurations, such DSP gain controls always affect more-or-less on "XO" "EQ" "phase" and "delay" of the DSP settings which will leads you to possible endless DSP tuning spirals every time; within DSP configurations, XO EQ Gain Phase and Delay are always not independent with each other, but they are always interdependent/on-interaction.

Just for your possible reference, my DSP-based multichannel multi-SP-driver multi-amplifier active system (ref. here for the latest setup) has flexible and safe analog level on-the-fly relative gain controls (in addition to upstream on-the-fly DSP gain controls) for L&R subwoofers, woofers, midrange-squawkers, tweeters, and super-tweeters, all independently and remotely. My post here shows you a typical example case for such safe and flexible on-the-fly analog-level tone controls. This my post would be also of your interest.

Spoiler

 

[ElJaimito]

First, thank you for sharing this link: I had not encountered this lecture before. I have always found Toole’s books a useful reference. Unsurprisingly, I find nothing to disagree with!

Let’s note that Doc Toole starts by saying: "What people hear in their homes and cars through their earbuds or whatever..." - we are not discussing the studio environment, which is my only real concern for critical listening. NB: It is interesting how poor the sound is in the hall! Despite the diffusers!

In domestic listening - as he emphasises is the focus! - and with an uncorrected environment certain factors of loudspeakers are emphasised as compared with an acoustically-corrected studio. Moreover, domestic listening is not near-field listening, a placement designed to exclude as much room influence as feasible.

I use room correction in the near-field environment, and also in the far-field - but this is in a highly acoustically-treated listening room, a control room. Even given this restriction, the area, or volume, of the corrected listening space is very restricted before the correction fails.

The other point is that there are two different scenarios involved: reproduction of a performance of music, or reproduction of a studio recording that has no actual original existence outside the control room of the studio.

I built my first hifi at the age of 12, 71 61 (oops not that old yet) years ago. I have heard hundreds of speakers over my audio history - I started out as a hi-fi salesman, then graduated to professional audio. I have never heard two speakers that sound the same, though some brands have family resemblances. The least coloured speakers that were readily available and that I have owned were the Quad electrostatics, both generations, but these are utterly room dependent, and useless as monitors IMHO. And no bass!

I love his graph showing the performance of listeners, which entirely squares up with my experiences in the music industry, where many unexpected people are functionally deaf.

What was once hi-fi - the attempt to get high fidelity reproduction of original live recordings - has little to do with audiophilia, and most popular music does not involve live recordings.

I don’t think there are many serious recording studios nowadays with poor monitoring. His heartfelt plea for neutral monitors is 100% on, in my opinion, and that’s why I have Neumann. Expensive, but priceless.

Note his statement: “active speakers… are the future”, and (paraphrase) the only way forward. All I can say is: Yes.

 

[krabapple]

Moreover, domestic listening is not near-field listening, a placement designed to exclude as much room influence as feasible.

Mine is. And my speakers are designed for it.

I bet I'm far from alone here in the first regard. I mean, at the extreme, how many people on ASR report that they are mainly listening to speakers located on their desk? (Which always bemuses me.)

In my case they're not on a desk, they're on stands, very traditionally, but I'm in the near field of a surround sound setup in a smallish room.

But I agree 1000% that it's always important to understand what situation Dr. Toole is talking about.

 

[ElJaimito]

Mine is. And my speakers are designed for it.

I bet I'm far from alone here in the first regard. I mean, at the extreme, how many people on ASR report that they are mainly listening to speakers located on their desk? Which always bemuses me.

In my case they're not on a desk, they're on stands, very traditionally, but I'm in the near field of a surround sound setup in a smallish room.

But I agree 1000% that it's always important to understand what situation Dr. Toole is talking about.

Sure. And yes. But I wanted to emphasise that this stuff was all focussed around the listening rooms HK use, which mimic traditional home listening scenarios, and the arguments he puts forward here are concerning that type of speaker placement. So these arguments do NOT apply to near-field environments, at least not much. Obvs. he also writes on recording studio design

 

[celroid]

I have read and thought about many of the subjects Dr. Toole presents in his book, but unfortunately this chapter is about how to avoid degrading very good speakers by using automatic room correction. Dr, Toole does cover the subject of personal preference based on individual hearing extensively else where in his book. However, he does compare a microphone to ears and a brain.

Dr. Toole does say "Consequently, the processors perform equalization corrections including non-minimum-phase acoustical interference irregularities, in order to hit the specified target curve." Could be semantics.

I do agree with Dr. Toole that individuals should tune their loudspeakers to their liking. The reason I post this information is to help those, interested, in not degrading their loudspeakers.

Toole also says this:

If system equalization is to be based on these data, careful interpretation is necessary. When it is done by inadequately trained technicians or by an automatic algorithm, there is a real risk that equalization may be applied to non-minimum-phase irregularities that should be left alone. Good loudspeakers can thereby be degraded. This is the explanation why many people find that the best setting for a room equalizer is “off.”

If someone applies EQ for a speaker based on the speaker measurements done by Amir, is there no risk of degrading the speaker by trying to reduce a resonance spike or increase a wide dip? Are the "non-minimum-phase irregularities that should be left alone" also part of and visible in the spinorama, or only something that affects room measurements?
Can we tell from the speaker measurements done by Amir, spinorama + waterfall, etc, whether a spike or dip is a minimum phase irregularity or is not a minimum phase irregularity and therefore cannot be improved by equalization (above the transition frequency)?