Importance of impulse response

[FeddyLost]

This confused me because I happen to use Eclipse single driver speakers, which I like a lot and I indeed think they sound really transparent like they claim, and their whole philosophy is basically designing for good impulse response

Transparence IMO is not a thing that can be easily felt. From my experience if some speaker sounds "transparent", it's not correct, with some exaggerations of presence/mid-highs or lack of lows.
But really good fullrange speaker can sound correct until it's overdriven. For example, Fostex NF1 speakers with parabolic hyperboloid woofer like FW168HP-X sounded very nice.

Has any company tried to make an active single driver speaker, that utilizes EQ to somewhat fix its issues etc?

For example

PROFESSIONAL STUDIO MONITORS SUPER CUBES 5

dmaxaudio.com

But these speakers are usually limited with SPL, LF extension and of course they are beaming. So, it's a nearfield monitoring by definition.

 

[gnarly]

OT : I have been shooting my own IRs, with my studio monitors. I do not really agree that one needs an omnidirectional speaker. There are almost no musical instruments with an omni response, most are directional, some highly directional. Eg. a trumpet is very directional. If one puts a (with omni speaker) sampled hall on a trumpet spot, the acoustic will sound weird. A trumpet never triggers the real space in this way !

Hi, there's a little confusion it seems...
Pretty sure kemmler3D was talking about the impulse response of a room, not that of a speaker.
The reason an onmi is needed to excite the room, is to get the room's response alone, without path dependent speaker reflections as part of the room response.
A speaker's varying polar radiations excite the room unevenly, and will give a different room IR for each different speaker location, and/or install angle.

A balloon pop, or a gun loaded with blanks, gives an omnidirectional stimulus to the room....in an even polar fashion. Those two example of sharp transients are basically a Dirac pulse, providing a fairly full-range stimulus.

When speakers are used to excite a room to measure the room's IR, they are typically a dodecahedron or such...



My DIY version...

 

[Yannick Willox]

Hi, there's a little confusion it seems...
Pretty sure kemmler3D was talking about the impulse response of a room, not that of a speaker.
The reason an onmi is needed to excite the room, is to get the room's response alone, without path dependent speaker reflections as part of the room response.
A speaker's varying polar radiations excite the room unevenly, and will give a different room IR for each different speaker location, and/or install angle.

A balloon pop, or a gun loaded with blanks, gives an omnidirectional stimulus to the room....in an even polar fashion. Those two example of sharp transients are basically a Dirac pulse, providing a fairly full-range stimulus.

When speakers are used to excite a room to measure the room's IR, they are typically a dodecahedron or such...
View attachment 243705


My DIY version...
View attachment 243708

Off topic I know, but that was exactly my point. A musical instrument does not excite a hall in an even way, hence it makes almost 0 sense do use a hall IR shot with a dodecahedron.

Hall IRs for music production are not about measuring the hall, it is about the musical result. Even a Steinway D does not excite a concert hall in an omnidirectional way, certainly not above 5KHz.

 

[kemmler3D]

Off topic I know, but that was exactly my point. A musical instrument does not excite a hall in an even way, hence it makes almost 0 sense do use a hall IR shot with a dodecahedron.

Hall IRs for music production are not about measuring the hall, it is about the musical result. Even a Steinway D does not excite a concert hall in an omnidirectional way, certainly not above 5KHz.

@gnarly I think Yannick is probably right. The orthodox way of recording a room's IR is to use an omni source, but when you consider using the IR as an effect in production, you'd be effectively simulating "what if this instrument (e.g. Trumpet) had the same radiation pattern as the omni source" which is not necessarily true-to-life. Most real instruments are fairly directional... maybe for percussion you'd want an omni IR, but for voice or trumpet, a studio monitor probably makes more sense...

 

[gnarly]

@gnarly I think Yannick is probably right. The orthodox way of recording a room's IR is to use an omni source, but when you consider using the IR as an effect in production, you'd be effectively simulating "what if this instrument (e.g. Trumpet) had the same radiation pattern as the omni source" which is not necessarily true-to-life. Most real instruments are fairly directional... maybe for percussion you'd want an omni IR, but for voice or trumpet, a studio monitor probably makes more sense...

Aaah, I see. We're all saying the same thing it seems, but with different points of reference...
Thanks

 

[ernestcarl]

The two major factors that mess up an impulse and step response are the phase rotations from crossovers; and different times-of-flight from drivers to the ears simply based on geometric distances.

A single full-range driver has neither. Too bad they can't ever play very loud, or really have good frequency extensions.

And there's the room...

Even with a full-range driver, the IR as it finally arrives (and is measured) at the MLP may not be entirely so intact or pristine.

@KSTR mentioned the Fostex 6301 which I happen to have here with me. Measured at maybe around 2.7m (more or less) mounted above my front desk LED monitor pointing towards the rear couch MLP of my room:



It's okay, but the GD in the bass is not looking so hot anymore. I doubt DRC by itself can perform miracles in that messy area.

However, I've been able to improve the situation with the addition of a subwoofer which mainly extends the response and relieves the small single driver of much of the LF workload.

Using a few filters in rePhase in this particular instance: three paragraphic phase EQs in the HF, a first order all-pass HPF at 100Hz and a linear phase 2nd order 180Hz HPF:

*rest of the IIR PEQs is performed in JRiver's DSP studio

While the crossover with the sub may not be "linear phase", the result nevertheless is pretty decent.

 

[gnarly]

And there's the room...

Even with a full-range driver, the IR as it finally arrives (and is measured) at the MLP may not be entirely so intact or pristine.

Hi ernestcarl,

Yep, for sure a room mucks with impulse. But i stay fascinated by "how much, really"?

For grins yesterday, I FIR tuned a single 3" TC9 using it full-range from 100Hz up.
Wanted to see if an IIR high-pass would show any pre-ring at all, in combination with the mag and phase flattening used to get to a near perfect impulse.
(which as you can see it doesn't)

Ok, when i look at that ETC, i think all the direct sound has hit my ears within 1ms. And that's a fine impulse for sure.
So then come reflections...floor bounce maybe first, what 3-4ms later? How much does that really muck with what i first heard?


We all read/know about Haas effect, that says sounds arriving close in time get fused together, and are perceived as a single event.
Afaict, that fusing however, is with regard to psycho-acoustical fusing localization into a single source....
How about fusion in terms of tonality and timing?... as distinct from localization....

I dunno, much I need to study/learn here, in terms of hearing science..

I do know when i take a speaker outdoors, its clarity improves.
But i don't know if the clarity improvement comes from cleaning up the impulse response, or from simply not having later (non Haas) room reflection arrivals.
I also know the greater the direct to reflected sound ratio in a room, from building differnt H&V synergy horn patterns, the closer it sounds to outdoors.
So I'm inclined to believe rooms muck up sound more so with relatively later reflections, than within the short time frame of an impulse response.

Hope that made sense...

 

[kimmosto]

Room does not void good timing because timing affects to transients which don't have much reflections. Energy peaks of reflected transients are also higher and shorter if source has good timing. So speaker with good timing is better than speaker with bad timing also in room. Other claims just indicate lack of common sense and experience with minimum phase speakers.

 

[ernestcarl]

Hi ernestcarl,

Yep, for sure a room mucks with impulse. But i stay fascinated by "how much, really"?

For grins yesterday, I FIR tuned a single 3" TC9 using it full-range from 100Hz up.
Wanted to see if an IIR high-pass would show any pre-ring at all, in combination with the mag and phase flattening used to get to a near perfect impulse.
(which as you can see it doesn't)

View attachment 243987View attachment 243988

Ok, when i look at that ETC, i think all the direct sound has hit my ears within 1ms. And that's a fine impulse for sure.
So then come reflections...floor bounce maybe first, what 3-4ms later? How much does that really muck with what i first heard?


We all read/know about Haas effect, that says sounds arriving close in time get fused together, and are perceived as a single event.
Afaict, that fusing however, is with regard to psycho-acoustical fusing localization into a single source....
How about fusion in terms of tonality and timing?... as distinct from localization....

I dunno, much I need to study/learn here, in terms of hearing science..

I do know when i take a speaker outdoors, its clarity improves.
But i don't know if the clarity improvement comes from cleaning up the impulse response, or from simply not having later (non Haas) room reflection arrivals.
I also know the greater the direct to reflected sound ratio in a room, from building differnt H&V synergy horn patterns, the closer it sounds to outdoors.
So I'm inclined to believe rooms muck up sound more so with relatively later reflections, than within the short time frame of an impulse response.

Hope that made sense...

I can’t say I know the exact time window wherein things need to be contained in order to be psychoacoustically acceptable. Keeping other sounds as low as possible and the envelope/ETC as evenly declining seems to be desirable.

Clarity values is increased by controlling reflection-decay, but some amount of reflections do improve perceived sound quality so I wouldn’t necessarily want to eliminate it all. Though, I don’t understand why you think controlling room reflections is not part of cleaning up the IR unless we were exclusively only talking about the speaker’s native anechoic response without regard to the room at all.

Room does not void good timing because timing affects to transients which don't have much reflections. Energy peaks of reflected transients are also higher and shorter if source has good timing. So speaker with good timing is better than speaker with bad timing also in room. Other claims just indicate lack of common sense and experience with minimum phase speakers.

Of course, it does not void the inherent good timing performance of the speaker. Can’t really argue with that… but, common sense really is not all that “common” to the inexperienced. I’m curious, what other specific claims about min phase appear wrong or a mistake to you?

 

[kimmosto]

I’m curious, what other specific claims about min phase appear wrong or a mistake to you?

Sorry my head is quite empty so I can't recall claims not already mentioned.
OT I just hope people don't give up their independence to decide what is important to them. Significance or preference result from some study is just statistics if perceptibility or audibility or both exist (proved). It may be valid for some...many of us, but at least I don't need anyone including the best known audio scientists to specify preference and significance of different features in reproduction. Science may not be ready either In addition, anyone can use as much snake oil as like, and that does not necessarily make his audio system and listening conditions any worse. It could be just one funny part of the hobby while listening one of the best systems in the world.

 

[fineMen]

... in order to be psychoacoustically acceptable ...

For whom? What You do: state a problem with an entertaining machinery, that's what the stereo, 5.1, 7.1, 7.2 ... actually is. It is not even some virtual reality, It is most of the time, if not always meant to entertain a single person at home, which is you in this case. With the term 'psychoacoustically' you call science in. You ask Science to investigate the human body, in this case the ears, the nerves, the brain in order to render Your experience perfect. Then You might get into some peace of mind. Yep, the enjoyment you want to get from the stereo has to be an automatic body sensation, not the result of an effort taken by the intellect. You want a perfect 'signal' so that the 'information' doesn't have to be decoded actively.

Did I rephrase your comment correctly? My counter argument:

Hifi people feel entitled to utterly ignore the production process of the also otherwise arbitrary software they want to run the machinery with. What people are after is the excitement and affirmation by the experience of perfection that is just set in place for them personally. Music, what is that for? Again, production process, never mind! The contemporary production process kills every attempt to have 'impulse' because of how the many microphones are used alone (pun not).

I appreciate that science neglects the hifi industry. All reasonable papers we waved around here (without any clue, of course) focused on understanding the human hearing under the aspect of hearing aids. Hifi was not in focus. Do we need a hearing aid? Why is it, that the situation with a hearing aid is considered applicable for the reproduction of a recording? Differing signal capture for hearing aid versus hifi, what sort of a 'signal', how to decode it into 'information'? What's the 'information' contained in a recording? Is there something missing? Is it because of the production process to begin with, or is it just and only the speaker? If it was the speaker--how could the producers, the sound engineer evaluate the recording, when they use non-ideal monitor-speakers themselves? The recording would be non-ideal from the very start.

 

[ernestcarl]

Did I rephrase your comment correctly?

Can't say "yes" unequivocally to the way you've re-worded things.

"Acceptable" can mean a number of things, but in the context and goal of high fidelity sound reproduction, I suppose it is only fair and desirable that the speaker system's anechoic and and in-room transfer function retains some relative close semblance to the original source signal. Given how imperfect and variable the performance of speakers (and rooms) are to this day, some arbitrary minimum standard of quality may need to be encouraged. For example, Genelec provides a GRADE report performance analysis to some of their studio monitors.

While there is no reason why a person cannot enjoy the same "information" mangled or distorted to an x level of degree, that's really not the singular point of this hobby to me -- else why bother with measurements at all here at ASR. It may seem ironic, but it's not lost on me that I can still enjoy "flawed" sound playback experiences at any time, anywhere.

 

[thanossapiens]

And there's the room...

Even with a full-range driver, the IR as it finally arrives (and is measured) at the MLP may not be entirely so intact or pristine.

@KSTR mentioned the Fostex 6301 which I happen to have here with me. Measured at maybe around 2.7m (more or less) mounted above my front desk LED monitor pointing towards the rear couch MLP of my room:

View attachment 243880 View attachment 243881

Is the group delay in the second pic from the reflections?

 

[ernestcarl]

Is the group delay in the second pic from the reflections?

Mainly rear wall (<100Hz), floor and ceiling (+100Hz), desk table (400-500Hz) reflections.

 

[fineMen]

"Acceptable" can mean a number of things, but in the context and goal of high fidelity sound reproduction, I suppose it is only fair and desirable that the speaker system's anechoic and and in-room transfer function retains some relative close semblance to the original source signal. ... arbitrary minimum standard of quality ...

... cannot enjoy the same "information" mangled or distorted to an x level of degree, that's really not the singular point of this hobby to me ...

And reiterated You don't even mention the production process, having multiple microphones for recording a real drum kit or a grand piano. Toole's work revealed and resolved another problem, that was present for decades. Tonal balance, home curve, directivity of home stereo speakers. But instead, the 'impulse' was, ignoring that pink elephant in the room discussed eagerly. Prudent ignorance is a constant in the business, as well as to overemphasize minute details, whilst misusing 'scientific' terms in speculative hyperbole.

What was the stereo advertising without consumers believing that there was "a resemblance to the original source signal"? It's like believing that a Picasso would resemble the physical image of a person. Irony: could some historians in art evaluate the quality of a Picasso when the portrayed person has passed away? I mean, once the historian would not know anymore what is portrayed? Same situation with recordings, one never knows. Speculate! You miss the 'pulse'.

 

[gnarly]

@fineMen, you raise some interesting points about the actual production, and how recording cannot help but change impulse responses.
Which is easy to picture and agree with...

But i don't think that dilutes the value of a speaker's impulse at all, because I don't think we are really trying to recreate the actual production's impulse response(s).
For me, attempting to do such is pure audio non-sense.
I figure the best we can hope for is to get to something close to what the mastering engineer listened to and liked.
And he/she did that listening to speakers.
So, in essence we are asking our speakers to reproduce mastering speakers that are reproducing actual production ...(other than maybe for bootleg or direct recordings that never have been mastered).

Ok, so for me...I could give a rat's ass for the idea of "faithful reproduction".
I simply care about how good a track sounds to me.
And I've found that pursuing a clean impulse response, greatly improves the odds of any given track sounding good.
That simple really......


The closer to textbook the impulse/step/ETC response is, the flatter the frequency magnitude is, and the flatter the phase is. That's just a given no one can dispute.
With such a speaker, i think it's the best odds you can get, of hearing what the mastering engineer heard through their speakers/studio.
If nothing else, I know my system isn't adding further noise to the circle of confusion.

 

[617]

@fineMen, you raise some interesting points about the actual production, and how recording cannot help but change impulse responses.
Which is easy to picture and agree with...

But i don't think that dilutes the value of a speaker's impulse at all, because I don't think we are really trying to recreate the actual production's impulse response(s).
For me, attempting to do such is pure audio non-sense.
I figure the best we can hope for is to get to something close to what the mastering engineer listened to and liked.
And he/she did that listening to speakers.
So, in essence we are asking our speakers to reproduce mastering speakers that are reproducing actual production ...(other than maybe for bootleg or direct recordings that never have been mastered).

Ok, so for me...I could give a rat's ass for the idea of "faithful reproduction".
I simply care about how good a track sounds to me.
And I've found that pursuing a clean impulse response, greatly improves the odds of any given track sounding good.
That simple really......


The closer to textbook the impulse/step/ETC response is, the flatter the frequency magnitude is, and the flatter the phase is. That's just a given no one can dispute.
With such a speaker, i think it's the best odds you can get, of hearing what the mastering engineer heard through their speakers/studio.
If nothing else, I know my system isn't adding further noise to the circle of confusion.

The original recording engineer was probably listening to the recording on speakers which mangled the IR as much as any other speaker. Same with the mastering engineer, the artist's monitors, everybody.

There are 'pure' recordings out there - stuff mic'd with, you know, two earthworks or B&K microphones with no compression, huge bandwidth and no EQ. You 'produce' such a record by moving the instruments closer and further from the mics. I believe Pearl Jam even made a binaural album that way.

Unfortunately there are big problems with these 'principled' approaches to recording production. One, I've never heard one with music that I liked. Two, who is to say which mic orientation is correct for speakers? Space the mics out or coincident? Angle them or straight ahead or use omnis? As I'm sure you're aware, the stereo illusion uses multiple cues such as delay and relative loudness of sources, but it's hard to find a mic position which has both cues in the right proportion for the speakers you listen on.

Our recordings are entirely synthetic. They are not photographs, they are memories of impressionist paintings. I would argue that it is precisely this quality which makes music so transporting.

Toole's 'circle of confusion' described problems establishing consistent in room tonality, and I think adressing these problems is a good goal for the recording industry because it is achievable.

 

[fineMen]

And I've found that pursuing a clean impulse response, greatly improves the odds of any given track sounding good.
That simple really......

Imho that is an acceptable statement.

Our recordings are entirely synthetic. They are not photographs, they are memories of impressionist paintings.

Imho that is an agreeable statement.



Both speak of what can be spoken of. But to talk about all that other stuff before, using occupied scientific terms incorrectly got me annoyed. Sorry for that little defect of mine. I'm trying to be less impulsive (implosive?) next time.

Best regards!

 

[ernestcarl]

And reiterated You don't even mention the production process, having multiple microphones for recording a real drum kit or a grand piano. Toole's work revealed and resolved another problem, that was present for decades. Tonal balance, home curve, directivity of home stereo speakers. But instead, the 'impulse' was, ignoring that pink elephant in the room discussed eagerly. Prudent ignorance is a constant in the business, as well as to overemphasize minute details, whilst misusing 'scientific' terms in speculative hyperbole.

What was the stereo advertising without consumers believing that there was "a resemblance to the original source signal"? It's like believing that a Picasso would resemble the physical image of a person. Irony: could some historians in art evaluate the quality of a Picasso when the portrayed person has passed away? I mean, once the historian would not know anymore what is portrayed? Same situation with recordings, one never knows. Speculate! You miss the 'pulse'.

You assume I am supposed to be unaware of these things — because I have not mentioned it.

And now the accusation of “misusing scientific terms in hyperbole”… eh, ok.

So what exactly are we supposed to do alternatively then in your paradigm?

I’m hoping you’ve got an interesting answer for us.

 

[gnarly]

The original recording engineer was probably listening to the recording on speakers which mangled the IR as much as any other speaker. Same with the mastering engineer, the artist's monitors, everybody.

There are 'pure' recordings out there - stuff mic'd with, you know, two earthworks or B&K microphones with no compression, huge bandwidth and no EQ. You 'produce' such a record by moving the instruments closer and further from the mics. I believe Pearl Jam even made a binaural album that way.

Unfortunately there are big problems with these 'principled' approaches to recording production. One, I've never heard one with music that I liked. Two, who is to say which mic orientation is correct for speakers? Space the mics out or coincident? Angle them or straight ahead or use omnis? As I'm sure you're aware, the stereo illusion uses multiple cues such as delay and relative loudness of sources, but it's hard to find a mic position which has both cues in the right proportion for the speakers you listen on.

Our recordings are entirely synthetic. They are not photographs, they are memories of impressionist paintings. I would argue that it is precisely this quality which makes music so transporting.

Toole's 'circle of confusion' described problems establishing consistent in room tonality, and I think adressing these problems is a good goal for the recording industry because it is achievable.

Many good points, easy to nod yes to......

I'd love to see the recording industry work towards at least specifying some degrees/type of standards.

my previous 'circle of confusion' comment was meant to say, I don't want to add yet another layer of confusion into what my ears finally hear...
(i have Toole's book, and refer to it often)