Evidence-based Speaker Designs

[QMuse]

spend some time learning how to actually measure and modify a room to meet a set of design requirements. it will make much more of my commentary relatable and understandable vs someone who has not done so.

Have you posted any measurements here?

 

[localhost127]

No, he says to buy a speaker with proper off-axis response that correlates well with direct sound.

no, he states if the loudspeaker has poor off-axis response, the reflection will color/tonal change the perception of the direct signal - and in that case it is best to absorb the reflection and to do so with broadband absorption that doesn't modify the spectral content of the reflection (ie, fully attenuates it).

and if you have a loudspeaker with good off-axis response, then it is "a matter of taste" whether the user prefers more accurate, pin-point imaging (attenuated first order high-gain early reflections) - or a more broadened width imaging as with natural sidewall reflections allowed.

If you chase and try to remove all those reflections for a bad speaker, you will build a padded cell that will be dead as a year old fish. It will sound horrible for any 2-channel listening and depending on how far you have gone, for multi-channel as well. You have completely bastardized Dr. Toole's research with that statement.

this is not my experience - is it yours? adding some broadband panel absorbers at first reflection points (or anywhere else that induces a high-gain, delayed reflection deemed destructive by the user) in no way "creates a padded cell" dead as "old fish". what kind of exaggerated vocabulary is this? the reason i don't think you actually have any experience modifying rooms is becuase you continually make statements like this (totally exaggerated) that have no basis in reality.

secondly, you do not need "absorption" to attenuate an indirect specular reflection. large, flat/planar reflective panels are used all the time to redirect the reflection away from the listening position such that it can be managed and reintroduced at a later time - preserving energy within the room.

and for multi-channel, we use Binary Amplitude Diffusers (2D BADs) to atteunate the high-gain specular reflections and convert them into many spatially dispersed reflections of lower gain (below detection threshold such that they are not cued on for localization, imaging, etc). this is because there are so many active sources (and thus reflection points) in multi-channel setup that it would require over-excessive use of broadband absorption and create too damped room. so in this scenario, BADs are used to damp but maintain energy within the room to alleviate this.

2ch stereo also utilize later arriving diffuse (reflection RICH, dense) sound-field - so the room is certainly not considered a "padded cell". again, you ignore these basic foundations of room treatment.

i personally do not know anyone who has done this process and created a a "padded cell" - yet you continually mention it as if it is so common pitfall! go to any audio forum or online community and you can find people with loudspeakers that exhibit poor off-axis response whose perception was improved via the use of attenuated first-order reflections - while not creating a "padded cell that will be dead as your old fish".

 

[tuga]

no, he states if the loudspeaker has poor off-axis response, the reflection will color/tonal change the perception of the direct signal - and in that case it is best to absorb the reflection and to do so with broadband absorption that doesn't modify the spectral content of the reflection (ie, fully attenuates it).

and if you have a loudspeaker with good off-axis response, then it is "a matter of taste" whether the user prefers more accurate, pin-point imaging (attenuated first order high-gain early reflections) - or a more broadened width imaging as with natural sidewall reflections allowed.

It's not enough to read the book. There are rules on how to interpret what is written.

 

[localhost127]

500 Hz? What was explained was a general issue with ETC because it is spectrum-blind. It says that the spikes in such measurement are not representative of the true energy of the reflections. There is no magic 500 Hz in there. Anything that absorbs some of the spectrum of the reflection will produce such false measures.

no one is analyzing their rooms in band-limited 500hz speech signals. full stop. you haven't qualified at all how the time-domain information (used to determine flight path distance) is "extremely unreliable measurement". now you're telling me to use mirors and a tape-measurer to mark reflections instead of actual, measured data.

a mirror is not a measurement tool. it's a visual-aid used to illustrate to someone the reflective nature of indirect specular energy.

You do? In literally years of arguing with you on this topic on AVS, you did not once produce a measurement you had performed. Later on I discovered you lived in an apartment and did not even have an audio system.

i don't even like music, to be honest - so why on earth would i spend money on own a stereo??? who does that??

And why do you need ETC to know which reflections to absorb? If you are designing a new listening space, how would you do that without measurements? You need ETC to know there is a side wall reflection? Ceiling? Floor? Rear and front walls?

why are you now implying every home listening environment is "a designed, new listening space"? it's comments like these that really solidify the fact that you don't actually have any experience modifying a reproduction environment to achieve a pre-determined set of design requirements.

are the bulk of the members here predominately designing new listening spaces here? or are they modifying existing spaces? what was the context of the conversation?

Answer is that you don't. Professional acousticians design state of the art listening spaces all on paper without a single measurement to "find reflections: using ETC or otherwise. We use psychoacoustics research into perceptual effects of reflections and use that a priori to decide what to do with reflections. ETC with its faulty amplitude problems need not apply.

i get it - you are now deflecting and distracting the use of insinuating that "500hz speech band-limited signals" are somehow used to treat and modify an existing listening space to instead implying all designs are somehow "new".

fact is, professional acousticians design new rooms from scratch all the time - and are able to take advantage of software modeling in what's called the "design phase". they are able to incorporate many of the room's "treatments" and acoustical tools into the structure itself. unfortunately, many of the members of this forum and elsewhere in the world do not have that luxury. many are working with pre-existing rooms that can only be modified from the walls-in, and extensive "software modeling" and "redesign of the room from scratch" is not possible. there is no "design phase" and "construction phase" for modification of existing rooms.

what's your point? acousticians design brand-new rooms from scratch (incorporating a design phase) and also modify existing rooms based on a myriad of measurement tools. why would a professional acoustician need to "hunt down reflections with the ETC" when they designed the room from scratch? why would you even impose this question? it makes no sense at all - it's all hand-wavy distractions/deflections.

 

[QMuse]

Ok, all clear now.

 

[Senior NEET Engineer]

This forum is so hell bent against acoustic treatment lol. Even the writer of the bible has a lot of acoustic treatment in his room, including absorbing the first sidewall reflection.

 

[tuga]

This forum is so hell bent against acoustic treatment lol. Even the writer of the bible has a lot of acoustic treatment in his room, including absorbing the first sidewall reflection.

Maybe he needs to publish a "Sound Reproduction - For Dummies Edition".

 

[spacevector]

This forum is so hell bent against acoustic treatment lol. Even the writer of the bible has a lot of acoustic treatment in his room, including absorbing the first sidewall reflection.

This room? https://www.thescreeningroomav.com/...te-Real-World-Home-Theater-and-Listening-Room

 

[Senior NEET Engineer]

Maybe he needs to publish a "Sound Reproduction - For Dummies Edition".

I don't think that will work. The followers have already seen what they wanted to see and are taking the religion in a different direction.

 

[BillH]

I don't think that will work. The followers have already seen what they wanted to see and are taking the religion in a different direction.

Am I a follower? Let's not forget that there are many less vocal members here that are just a little less vocal. This is a site for the exchange of ideas and I hope all ideas are debated on their merits. I especially am interested in the relation between directivity (i hate the term) and imaging. To sound absorb or not?
Regarding "directivity", in other fields of physics we would be calling this the beam width or divergence or propagation angle. And don't get me started on dispersion - a frequency dependent term.

 

[Mnyb]

Latest exchanges in the tread is a bit off topic , but a more modern speaker will be more friendly to eq and room treatment as what’s spills out off the speakers not directly on axis actually resembes the input signal making the whole process more predictable and less room dependent.

I think I’ve learned something :

Some speaker designers have learned to tame the old cone and dome problem in a better way .

The old ways where “3 way speakers “ with smaller or dome midrange ( 3 way still valid , but also improves with more modern approaches) .

Or let’s makes the xover frequency higher so that it’s not in the “sensitive midrange where humans hear so well” combined with so called ”controlled breakup” of the midbass driver ?

What we actually hear is that jarring discontinuity between drivers radiation patterns if I understand the topic .
And the better solution is to control directivity via for example waveguides and then you suddenly can have your xover between treble and midbass/midrange in that “sensitive midrange” which is desirable for various reasons.

There are more things than controlled directivity ofcourse, but it’s where I learn new things and that some design with a systematic pow , you can’t just shove good drivers in box and call it a speaker it won’t perform acoustically

 

[andreasmaaan]

What we actually hear is that jarring discontinuity between drivers radiation patterns if I understand the topic .

That, and lobing.

you can’t just shove good drivers in box and call it a speaker it won’t perform acoustically

Exactly. In fact, if you'll indulge me in an unscientific generalisation for a moment here: A well-designed speaker made up of crappy drivers will tend to sound much better than a poorly-designed speaker made up of SOTA drivers.

 

[Ilkless]

That, and lobing.

Exactly. In fact, if you'll indulge me in an unscientific generalisation for a moment here: A well-designed speaker made up of crappy drivers will tend to sound much better than a poorly-designed speaker made up of SOTA drivers.

An extreme example I know. The SEAS distributor here (not sure if he still holds the distribution rights) swears by running the magnesium SEAS Excel at 6dB/octave . For the superior "time-domain" performance of course. That is a driver series known for a very aggressive breakup (albeit with great pistonic performance at lower frequencies)

 

[tuga]

This is a site for the exchange of ideas and I hope all ideas are debated on their merits.

There seem to be a lot of dogmas which result from misinterpreting Toole or ignoring is uncertainties, though.

I especially am interested in the relation between directivity (i hate the term) and imaging.

The relation between directivity and imaging is inversely proportional, unless you have a very very wide room or treat/deflect early reflections.

 

[Frank Dernie]

Maybe you are right. Here are a couple of CSD plots:

Surely it is more likely to be the bass driver breakup than mid at that frequency?

 

[tuga]

Surely it is more likely to be the bass driver breakup than mid at that frequency?

Those are measurements of the SM75 midrange driver.

Here's the CSD plot of a SCM100SE:

https://www.hifinews.com/content/atc-scm100se-loudspeaker-lab-report

 

[Frank Dernie]

Those are measurements of the SM75 midrange driver.

Here's the CSD plot of a SCM100SE:

https://www.hifinews.com/content/atc-scm100se-loudspeaker-lab-report

Sorry, my pitiable brain read 350Hz up thread and I see on the graph it is 3.5kHz.
There used to be a paper on the net iirc by K&H before they became part of Sennheiser that illustrated how good their mid dome was using a comparison with a "well known mid range dome" (well known to be the ATC) showing an almost undamped breakup on it. This could be it.

 

[Ilkless]

Sorry, my pitiable brain read 350Hz up thread and I see on the graph it is 3.5kHz.
There used to be a paper on the net iirc by K&H before they became part of Sennheiser that illustrated how good their mid dome was using a comparison with a "well known mid range dome" (well known to be the ATC) showing an almost undamped breakup on it. This could be it.

The K+H dome manages 10dB more max SPL than the ATC one in a smaller footprint too.

 

[Bjorn]

i agree. i inquired numerous times at AVS and he was kind enough to respond and is very forth-giving that it is simply a matter of taste. and that certain people (professionals, studio engineers) would perhaps prefer a more objective (accurate) response for reproduction (for both working and pleasurable listening) than others that would subjectively prefer their own tastes (vs use of polls are surveys) - all very valid conclusions.

and as you reference, there is seemingly almost always a complete lack of discussion on the later-arriving sound-field in such circumstances. many will "remove" lateral energy via attenuation of first-order sidewall reflections, but completely ignore the re-introduction of that later energy via the use of 1-dimensional phase grating diffusers to provide a very dense, lateral reflection-rich diffuse tail to provide a sense of spaciousness and envelopment (coming from the rear wall/rear side wall directions) - whose decay also emulates the linear slope found naturally in large acoustical space reverberant sound-fields. you get the best of both words: a large ISD where-by only the direct signal is allowed to be "heard" (increasing the acoustical perceived size vs what the room's natural boundaries allow), increasing accuracy of direct signal in terms of localization, imaging, and speech intelligibility - and then providing a sense of the room (and in fact a sense of a much "larger" room) via the sparse reflections being converted into dense, reflection-rich, diffuse reflections and their lateral direction for spaciousness and envelopment.

so the comparison and testing should never (in my opinion) simply be: "allow sidewall reflections vs absorbed sidewall reflections", it should be something akin to "allow sidewall reflections vs attenuated sidewall reflections with later-arriving dense, reflection-rich lateral diffuse sound-field". it's a completely different response and perception. you are removing some lateral energy, but re-introducing it to the listening position at a later-time (in a managed fashion).

Absolutely. It's a more or less non existent topic and blind spot in Toole's researchers. However, it's been researched by others. But most are ignorant of past and other studies and cherry pick what suits them.

And as you have seen, there are unfortunately no room for serious acoustic and psychoacoustic discussions here. Peronal attacks and insinuations are more the norm. The irony is that the ignorant claim to be scientific with very little understanding of even the basics of small room acoustics, regularly confuses it with large room acoustics, and feel threatened by what they preceive as attacking "the truth". It's quite amusing but also very sad. Fortunately Floyd Toole is wiser and more humble and I respect him though I disagree with him in several areas (preference for multichannel, side wall contribution etc.).

 

[Frank Dernie]

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The K+H dome manages 10dB more max SPL than the ATC one in a smaller footprint too.

I have considered the KH420 from time to time but have so much kit I like already I have managed to avoid spending the money so far.
The layout of my room means I sit just a bit too far away from them according to their recommendations too.
Not sure where I can get a demo pair from either.