[Ethan Winer]

Guys,

Wow, great thread indeed. If I were to address everything here it would be all I do today. Here's what I do have time for:

Rob said: "If you don't want a flat room responese, then exactly where would you like your peaks and dips? And how pronouced would you like them to be?"

Bingo.

Related, I am convinced that when a recording engineer tries different mike placements on a grand piano, what's really being sought is the most pleasing arrangement of the comb filter peaks and dips that are always generated by reflections off the open lid. If you play around with an equalizer on a full music track you'll quickly learn that some frequencies sound good when boosted, and others sound good when cut. For example, cutting somewhere between 300 to 500 Hz reduces "boxiness" on many instruments. So if a piano sounds boxy or tubby, the engineer can slide the nulls around via mike placement so they align with the tubby or boxy tone. I bet many engineers don't even know they're doing this - they probably think the final mike location they selected is the most flat and neutral!

John said: "I'm not convinced that 'any' mechanical method exists to allow us to measure and adjust (thus over-riding our ears) to a 'true' flat."

Yes, this too, because there's no one right place you can put a measuring microphone. Perhaps the best way to measure room response is with two microphones, ear spacing apart, and sum the two channels before analyzing. But that won't account for moving your head a little as you bob along with the music.

Nathan asked: "Do you correlate 'measurably flat' with a subjective 'damn that sounds good' feeling?"

I have never used room EQ but I can tell you that the experience of most pro recording engineers is EQ'ing a control room system (versus a large venue which is very different) generally makes the sound worse. Yes, it measures perfectly flat, but it sounds bad - often too bright - anyway. I suspect the real problem is the way the room was measured, and not the result of having a flat response per se. That is, the measuring itself was probably wrong, likely due to using 1/3 octave averaging which lumps together frequencies that are currently correct with others that are not.

Fishin said: "simply having a flat response alone is definitely not it. I would guess having a low distortion..."

There are only a few things that matter in audio, and they have all been well known and understood fully for 50 years or more. What matters are frequency response, distortion, noise, and time/pitch stability. There are many types of frequency response errors, even more types of distortion, and many kinds of noise - and all have different levels of audibility.

Russ said, "I've concluded that the most realistic goal for the audiophile is to accurately reproduce what the MASTERING engineer heard."

Exactly, and this is the real reason acoustic treatment is so important. If the original studio room had some coloration or other, what you want is to duplicate that coloration. Whatever the recording contains, as determined by the recording and mastering engineers, is what should then come out your speakers and be heard by your ears. And if you want your room to sound like a million dollar control room, then you need a similar amount of acoustic treatment.

--Ethan

[8thnerve]

It seems that this thread is addressing more than just a flat frequency response and its value.  What we can and can't control, and does it matter seems more encompassing to me.  I think everyone agrees that it is practically impossible to achieve a truly flat response (assuming of course we can decide what that actually means), reduce all reflections and phase delays, and of course, try and figure out what the recording engineer was thinking when recording in the first place, or what his equipment or environment was like.  Not to mention the tenuous at best understanding we have regarding what our brain can and can't decode/discard/determine.  What this says to me is that we still have a long way to go in determining what will enable us to get closer to the live event, the event being the music making, not the exact displacement of the air molecules at the time of recording.

Here are some of the results of our testing to determine the most important factors to enable you to be transported to the music making.

Frequency response:  A flat frequency response alone can be very sterile.  That being said, with other factors corrected, acheiving a flatter frequency response is almost always beneficial to the overall experience.  Alone, it is not engaging; with other factors addressed, it shows it's benefits.

Phase and Reflection:  We have found this impossible to improve upon with the confined boundaries of any room, using any method of reduction of overall sonic output.  Reducing a set of frequencies at one area will cause a loss that we feel outweighs the benefit.  The only way we have found to improve phase relationships is with incredibly precise speaker placement, a wide, balanced frequency dispersion, and the reduction of distortion.

Distortion:  This is one of our primary focuses.  We have found nothing that makes a more dramatic improvement than the reduction of room distortion.  Room distortion causes severe phase cancellation and smearing, produces echo and ringing, and contributes heavily to what we consider the "sound" of your room.  Reducing the room distortion allows a flat frequency respose to be more obvious in its benefit, and a wide and accurate dispersion to seem to exist outside the boundaries of your room.

We honestly feel that without room distortion reduction, any change in frequency response, reflection reduction or any other room treatment method is overshadowed by the huge amounts of distortion in that space.  Imagine if electronics designers ignored distortion altogether and focused only on a flat frequency response and maintaining phase relationships!  Would they really be able to achieve either a flat frequency response or true phase relationships??  Not without addressing the distortion first.

This is where our research has lead us.  The benefit of each different method of room treatment is much more apparent in a space with less distortion.  In a room with distortion, results are inconsistent.  Like, "my measurements look good, but my room sounds bad" and vice versa.  Every time I see that I remain unsurprised, as it is the distortion causing that phenomenon.  In a well treated room (our definition of that of course ), obtaining better measurements almost ALWAYS results in an improvement in sound.

[_scotty_]

8thnerve,is your "room distortion"term the same as comb filter effects causing audible coloration at geometric frequencies.

Phase and Reflection: We have found this impossible to improve upon with the confined boundaries of any room, using any method of reduction of overall sonic output. Reducing a set of frequencies at one area will cause a loss that we feel outweighs the benefit
.

Is this an argument against active room equalization via analogue or digital equalizers?

[John Casler]

Wow, these are some great responses and I think from the questions and responses we can increase our options, awareness, and direction of experimentation

It is also great that we can freely discuss this as members and vendors without ruffled feathers.  A tribute to the gentlemen in our group.

If I might add another twist, which could also influence how we set up our systems and rooms, and that is the "music program" element.

This could even be a topic for a new thread, but I'll throw it out here.

In some of the discussions in this forum, we have discovered that there are various methods to using "acoustic treatments" that are "prefered" by some members and vendors.

Some of us like to "reduce" room interaction in some areas and "use it" in others.

But in the end, unless we are techies, we go with what "sounds right" or best.

And that takes us to recordings    

It is a sad fact   that even though the pursuit of our hobby could be considered the search to actually "recreate" the "absolute" (nothing added nothing taken away) reality of the performance, a good portion of the recordings we listen too cannot, and are not, engineered to allow us to do this.

Just as computer generated effects have taken over the video segment, "engineered" sonics are out of control in the audio portion.

So what does this mean in setting up your system?  Well for sure we can set up a room/system that sounds absolutley incredible, but is not, cannot, and will not sound like the real event.

Is that so bad?  I don't think so.

But for me the goal still is to strive for the "realism" that can occasionally be found in some of the Orchestral, Jazz, and Live recordings, when and if they are "left alone" enough to allow us to actually "hear into" the venue and recording itself.

I mean look at the rag "Absolute Sound".  Even though they clain to be chasing the "real deal", year after year they highly rank and praise a speaker that "recreates" its sound by using the very room your in to totally develop its sound (Magnepans)

To me, as much as I like the "dipolar" sonic signature (Sometimes it is unreal) using the room takes any reference to "absolute" out of the equation.

I have also heard some make reference to the fact that they think "flat" might even sound bad.  I think "truly" flat will not sound bad at all, and by flat, I mean that each frequency is produced and perceived in the same relationship as it was recorded, or performed (we have to remember that even the recording process is not guaranteed to be flat)

I have also seen comments that relate to the "sound" of an anechoic chamber and how bad it sounds.  I might disagree.  I think many times we attempt to place our map (the way we listen) on all environments and expect to be able to assess the result.

That won't work.  If you are listening in an "anechoic chamber" you have to listen nearfield!!!! and I mean near!!!  If you have speakers that will "blend" in the nearfeild and listen at 3-5 feet in an anechoic chamber you will have a religious experience.

For that matter, you can listen anechoically at home....Just put on your headphones   Aside from the fact that you don't get the "localization" cues, to build a soundstage in front of you, you do get to hear the signal with very little else added.  It is a "personal anechoic chamber".  

So since I don't like headphones, and I can't listen really nearfield in an anechoic chamber, I go for a reasonably nearfield position in a "quasi, psuedo, LEDE and reduce the negative effects of the room dramatically and hear (what I find to be) incredible reality in recordings that can display it.

But in any event, the main thrust of this post is to say, that while we all have goals for our rooms and systems, we are certainly limited by the software quality, and our personal prefernces (and sometimes our decorators) as to just how to pursue and satisfy our quest.

[Ethan Winer]

Hi Nathan,

> Room distortion causes severe phase cancellation and smearing, produces echo and ringing, and contributes heavily to what we consider the "sound" of your room. <

I agree with all you said, but I have a problem with your use of the term "distortion" in this context. From my perspective distortion implies a non-linearity, as in THD and IM distortion. Room effects - discounting a buzzing bookshelf - are always linear in that any deviation occurs in the same proportion at all volume levels. I know that others use the term distortion when referring to normal room effects, so I'm not singling you out! But in pure "engineer speak" I think distortion is best reserved for true non-linearity, no?

--Ethan

[Russtafarian]

I have also heard some make reference to the fact that they think "flat" might even sound bad. I think "truly" flat will not sound bad at all, and by flat, I mean that each frequency is produced and perceived in the same relationship as it was recorded, or performed

I like your description but I would call that "accurate", not "flat".  I define flat as a straight frequency response line across a spectrum analyzer that is measuring the on axis response of a speaker system from the listening position using pink noise and a calibrated microphone.  Clarifying definitions can help to straighten some of our semantic banter.

I have also seen comments that relate to the "sound" of an anechoic chamber and how bad it sounds.

Anechoic chambers are creepy to be in because the noise floor is so low and reflections so dead that nothing colors the source sound.  This isn't necessarily bad but it's unnatually freaky sounding (or more properly not sounding).  Nobody listens in that kind of enviornment.  It's used for laboratory purposes and possibly for prisoner torture.  A great place to measure the true output characteristics of a speaker but not a nice place to listen to that speaker making music.

John, since you and I seem to be on opposite sides of this discussion, I'd like to hear your room and your ideas as to why it sounds good.  And if your willing, come down and hear my room and I'll explain to you why I think my room sounds good.

[John Casler]

John, since you and I seem to be on opposite sides of this discussion, I'd like to hear your room and your ideas as to why it sounds good. And if your willing, come down and hear my room and I'll explain to you why I think my room sounds good.

You know I'm always up for that!

But I don't know if we're on "opposite sides" or not.  My reason for starting this thread was to actually "challenge" the flat measurement reality.

Flat lining on an instrument readout really might not be "flat" at all.  Accurate should be "flat" in that all frequecies are produced in a relationship with each other.

If a speaker/room/system has a "peak or valley" (remember I'm not talking about as displayed by current devices, but more what currently may not be measurable)  no matter how small or large, then that "accurate" relationship is changed to inaccurate.

So as you say it is semantics and discussing the existance of what I think is currently not accurately measurable.

But in any event, let me know when your coming this way and e-mail me your address and I'll see when I'm occasionally down there.

I'd love to hear the Gallo's again.  

[8thnerve]

Hi Nathan,

I agree with all you said, but I have a problem with your use of the term "distortion" in this context. From my perspective distortion implies a non-linearity, as in THD and IM distortion. Room effects - discounting a buzzing bookshelf - are always linear in that any deviation occurs in the same proportion at all volume lev ...

Distortion is defined in the electronic context as:

a. An undesired change in the waveform of a signal.
b. A consequence of such a change, especially a lack of fidelity in reception or reproduction.

Source: Dictionary.com

I don't entirely agree with the concept that room effects are always linear either.  I think the distortions caused by angles, especially acute ones, are decidedly non-linear.  And I don't mean to nitpick, but I use the term distortion as it it the most accurate for the type of signal degredation that I believe is occuring at these locations.  Essentially, I use that word after careful consideration, and believe it to be as or more harmful than distortion in electronic equipment, simply because I believe the levels of room distortion in most untreated rooms are 10% to much, much more.

So I guess what I am saying is, I understand why you think that distortion is the wrong term to use, but it is for precisely that reason that I use it...    - to irritate you! -- Just kidding... about the 'irritating you' part that is.

[Ethan Winer]

Nathan,

> to irritate you! <







Fair enough.



It's hard not to play with all the great smilies here!

Thanks.

--Ethan

[8thnerve]

Nathan,

It's hard not to play with all the great smilies here!

Thanks.

--Ethan

True!  I even got to use the cool devil one... I had been looking forward to that.  

[gonefishin]

I like your description but I would call that "accurate", not "flat". I define flat as a straight frequency response line across a spectrum analyzer that is measuring the on axis response of a speaker system from the listening position using pink noise and a calibrated microphone. Clarifying definitions can help to straighten some of our semantic banter.
 

  Hmmm...I view flat as a description how the response of a speaker is measured (which may be in room response).  I don't equate flat with necessarily being accurate.  To be accurate you must have low distortion and minimal phase problems.  You can be as flat as you want...but if the other two are high (or off) it ain't gonna sound accurate.


   Why can't as much attention as we give a flat response, be put toward low distortion measurements in speakers.  To me...this can be where a real difference in quality can be had.  In fact...this is where I think some of the regular ol' "audiophile" speakers fall short...which in part turns me off from them.  I know one speaker cannot be all things to all people...I just think distortion and phase relationships are equally important as having a flat response, if not more important...as long as things don't get out of hand  

   I can't wait until I start working on my room...I feel sorry for you guys already   so many questions!        


   thanks again for the discussion...

[_scotty_]

I have to second gonefishins question about loudspeaker distortion measurements. We routinely see THD and IM measurements on electronic
equipment in our systems,why aren't the same distortion measurements
done on loudspeakers. They wouldn't tell you everything about how they sound but you could at least have a place to start the winnowing out process from. A speaker with very bad IM could at least be left to last
place in an audition lineup.

[SWG255]

Scotty,

This isn't as easy as it sounds, unless some industry standards for measuring the distortion are developed. At what SPL and at what distance from the speaker should the measurements be taken? Should THD, IM or both be measured? What bandwidth should be considered?

Keep in mind that like other transducers, speaker distortion products are usually measured in the one to ten percent range. I suspect both room interactions and frequency abberations in the loudspeakers will effect the distortion measurements.

All of that notwithstanding, companies like JBL, Electro-Voice and Acoustic Research used to publish distortion figures as part of the spec sheets, particularly for their professional monitor and PA speakers. Distortion specs are still published by many manufacturers, and used to be a staple of reviews in mainstream hi-fi publications. (They still might be, I haven't read one in years) But we're back to the age old problem of not having an industry-wide measurement standard, so one can't compare distortion specs from manufacturer to manufacturer with a high degree of reliability.

Still, I consider a loudspeakers distortion characteristics, especially as plotted against SPL at a few frequencies across the spectrum to be a strong indicator of how the speaker will sound. A speaker with very low distortion at relatively high SPLs should sound better to my ears than a speaker with "flatter' frequency response but higher distortion measurements at the same SPL.

OK, perhaps this is taking this thread somewhere where it should spawn a new one, but all these points, especially considered with room treatments, passive and active, leads to better understanding of what is needed to achieve better, more accurate and euphonic sound.

I have to second gonefishins question about loudspeaker distortion measurements. We routinely see THD and IM measurements on electronic
equipment in our systems,why aren't the same distortion measurements
done on loudspeakers. They wouldn't tell you everything about how they sound but you could at least have a place to start the winnowing out process from. A speaker with very bad IM could at least be left to last
place in an audition lineup.

[_scotty_]

SWG225, From what you are saying 1% to 10% THD or IM on loudspeakers would look pathetically bad compared to .005% THD or IM
measured on typical solidstate electronics. This would explain why the subject isn't discussed in public. It looks like there is still room for improvement in this area despite the latest claims of sonic perfection from any number of manufacturers.

[Ethan Winer]

Scotty,

> From what you are saying 1% to 10% THD or IM on loudspeakers would look pathetically bad compared to .005% THD or IM measured on typical solidstate electronics. <

You nailed it. People obsess over minutiae in electronics, but overlook the horrible distortion in their speakers. This is not unrelated to fretting over a loudspeaker's frequency response when the room is making the response ten times worse than the speaker itself.

--Ethan

[8thnerve]

You nailed it. People obsess over minutiae in electronics, but overlook the horrible distortion in their speakers. This is not unrelated to fretting over a loudspeaker's frequency response when the room is making the response ten times worse than the speaker itself.

Word.

[Horsehead]

One designer paying particular attention to frequency response, phase relationships, and distortion is Bob Smith at SP Technology.  My Continuums were shipped with a personal THD graph of my individual speakers from 20hz to 10khz @98db @1 meter.  THD from 100hz to 10000hz are all under 1%.  Individual frequency graphs are also included and the speakers are pretty much ruler flat (+/- 1db) from 150hz to 20000hz.  

Does this translate into good sound?  You bet! The Continuums are by far the most dynamic and "cleanest" loudspeakers I have had in my listening room while at the same time remaining totally musical.