Flat Response

[DDF]

Re: Flat Response

"Flat anechoic response" is a common slogan that has very little actual practical meaning for establishing a design standard. Flat response in an anechoic chamber at what distance - 1 meter, 3 meters, 10 meters? Since the energy available for inevitable propagation loss is directly proportional to wavelength, the frequency response balance is altered significantly with distance .

See table 4 in:

http://www.rane.com/pdf/ranenotes/Enviromental%20Effects%20on%20the%20Speed%20of%20Sound.pdf

At 10' listening distance, sound absorption impact on frequency response < 0.1 dB.

I measured the difference in the diffraction signature for a quite small design at 2' vs 10' and the difference was less than 0.3 dB. It would be much bigger for a large baffle. I agree that the distance at which "flat response" is specified is very important due to changes in diffraction signature over distance. These response changes occur over a wide bandwidth so even a change around 1 dB would be quite audible.

[mzisserson]

Re: Flat Responce

Auracle,

I cannot believe I am saying this, but thanks for the response. I know what I am looking at but it did help me re-think how to interpret it, so thanks.

Listen to DLR too. He is beyond "guru" status.

[dlr]

Re: Flat Responce

Listen to DLR too. He is beyond "guru" status.

Thanks, only no more so than many others and less in some areas such as DDF and john k for example. I still learn from them.

dlr

[auracle]

Re: Flat Responce

Auracle,

I cannot believe I am saying this, but thanks for the response. I know what I am looking at but it did help me re-think how to interpret it, so thanks.

Listen to DLR too. He is beyond "guru" status.

I'm well aware of who DLR is. I've corrected Siegfried Linkwitz on another forum for an "apparent oversight" too - doesn't necessarily make me a genius. Everyone makes mistakes and oversights - that's an essential ingredient to the human condition. You corrected me the other day on another thread for a grammatical oversight - thanks, btw.

I've always felt it worthwhile to consider that the humility Einstein brought to his understanding of the universe is what drove his accomplishments - and that should give us all pause for thought.

[dantheman]

Re: Flat Responce

I'll share my thoughts on the old flat anechoic response. There are basically 3 schools of thought:
1) "reproduce the recording and just pray the recording is good" which requires a pretty darn flat on axis response and a smooth off axis response. These people only need graphs to pick their speakers generally, and lots of them. I fall into this crowd. The failings I see in this group is their neglect of the room. The mastering studio is typically a relatively dead environment--very dead when you look at the measurements of the control room compared to a typical untreated room in a house. The mixes are usually checked in various places as well--often a car(an acoustic disaster) and an iPod with cheap headphones(). That sort of depends on the studio/artist's target demographic. However, movies and multichannel music are mixed with a home environment in mind. The thing to remember here is that these studios often have a live end/dead end construction. The "live end" typically employs 2 or 3D quadratic diffusion. I have 2 sets of the same speakers, one in a more similar to the studio environment and one completely wet. In the wet room, the speakers do indeed sound bright and a touch harsh. No 2 ways about it. Even Harman's listening room is treated: http://seanolive.blogspot.com/2009/0...reference.html So far, this camp of thinking has made me happiest with my audio by a long shot. All the long day it's anything I want to play.

2) "I want to hear what I hear at the concert of my favorite music." I think every audiophile ultimately falls into this category for their entire lives. This is where I started my home audio journey and returned to it after going to camp #3 for many years. I hadn't even thought about there being a camp #1. So response and power is contoured to approximately resemble what the listener hears in his/her typical seating. A dedicated practitioner in this camp will forever be in a state of failure b/c there no way to really accomplish their goal except by swimming in dee Nile. What's recorded isn't the same or even all that similar to what they hear at the concert in multiple ways and every recording is different. That said, they might be able to get "close enough" for personal satisfaction as long as they limit what they listen to. It's too bad they need a second system for movies, television, or multichannel if they care about audio on those formats at all. This thought camp dedication resulted in me narrowing what I listened to more radically than any of the others both times. After going back to it for a few weeks the second time, I knew my thinking was off base and had to move on. I know Deward and Auricle take offense to this(maybe some others as well), but it is not intentionally offensive. They take offense to everything I (or most people) say. Hopefully they'll be adult enough to not take stabs at more ad hominem BS again after reading this. Just explaining my perspective. No reason for hostility adults. No one is attacking you.

3) "Take a few of your favorite recordings to Big Box Depot or the HiFi boutique, listen multiple times, pick the speaker you like in that unfamiliar and sometimes hostile and pressured environment with those few recordings and buy them." When I was this type, I was disappointed with every purchase after a few days of listening. Actually as soon as I got them home, but it took a few days for it to really sink in that there weren't what I thought I was buying. I tweaked various set ups for years and was never satisfied. I suspect it's similar for most. http://seanolive.blogspot.com/2009/0...o-product.html

Oh, I should throw in a fourth: 4) "Dude, buy a Bose they're the best it says so right here in the literature!" This is the uninformed majority that is probably just as happy with their purchase or maybe even more so than anyone else.:o I feel good just saying the name "Bose". "Bose!":D

Dan

[johnnyrichards]

Re: Flat Responce

Oh, I should throw in a fourth: 4) "Dude, buy a Bose they're the best it says so right here in the literature!" This is the uninformed majority that is probably just as happy with their purchase or maybe even more so than anyone else.:o I feel good just saying the name "Bose". "Bose!":D

Dan

Actually, you can insert any name of any speaker in there because that is what most people do. Some of us may play with toe-in, or move them out or in to the walls, whatever... Realistically though, until the advent of DSP like Audyssey - how many people who owned speakers ever did anything to compensate for the room? Hang some drapes? Throw a rug on the floor?

Most people who buy speakers (and many who build them) throw them in the room and hook up an amp. I do that lol, and I am ok with it. I just want it to make the music I like (and movies) sound how I want them to sound.

I've read enough to understand that duplicating a live performance of acoustic instruments is a waste of time, so why try?

[Guest]

Re: Flat Responce

There are basically 3 schools of thought:

How about the 5th group, which is:
Design the acoustic source with as linear on axis as possible and as linear off axis as possible, then place it in a reverberant room.
If you find the need to apply amplitude adjustment at the listening positions/area to correct tonal balance, based on that particular room, do so then.
I fall into that group ;).

cheers,

AJ

[Thomas Brown]

Re: Flat Responce

Most people who buy speakers (and many who build them) throw them in the room and hook up an amp. I do that lol, and I am ok with it. I just want it to make the music I like (and movies) sound how I want them to sound.

I've read enough to understand that duplicating a live performance of acoustic instruments is a waste of time, so why try?

Johnny, Thank you for the simple fact of enjoying what we have built or bought.
Bad recordings, good recordings, old crappy (in a good way) movies, to the best movie soundtracks out there. I enjoy 'em.

the one fact is, everyone 'hears' everything different, it is up to the individual to decide to enjoy it or not, or spend the rest of there life trying to find there personal 'audio nirvana'!

OP, or anyone else, if a 'guinea pig test subject' is every needed for what I hear, I'm in! I don't want to see graphs/tests before I listen, just set up the system and I will give my honest 'lead ear' opinion.

We now continue with our regularly scheduled programing of - hurling big scientific words and links at each other, enjoy. :D

[Dennis H]

Re: Flat Response

Because you said so?
Deward's subjective opinion is an unerring reflection of physical reality?
Or do you have scientifically verifiable/repeatble data to support this claim?
Can we see it now?

Audio Engineering Society Convention Paper 6190
Presented at the 117th Convention
2004 Oct 28-31 San Francisco, USA

A Multiple Regression Model for Predicting Loudspeaker Preference Using Objective Measurements: Part II - Development of the Model
Sean E. Olive, AES Fellow

ABSTRACT
A new model is presented that accurately predicts listener preference ratings of loudspeakers based on anechoic measurements. The model was tested using 70 different loudspeakers evaluated in 19 different listening tests. Its performance was compared to 2 models based on in-room measurements with 1/3-octave and 1/20-octave resolution, and 2 models based on sound power measurements, including the Consumers Union (CU) model, tested in Part One. The correlations between predicted and measured preference ratings were: 1.0 (our model), 0.91 (inroom, 1/20th-octave), 0.87 (sound power model), 0.75 (in-room, 1/3-octave), and −0.22 (CU model). Models based on sound power are less accurate because they ignore the qualities of the perceptually important direct and early reflected sounds. The premise of the CU model is that the sound power response of the loudspeaker should be flat, which we show is negatively correlated with preference rating. It is also based on 1/3-octave measurements that are shown to produce less accurate predictions of sound quality.

[Deward Hastings]

Re: Flat Responce

I have 2 sets of the same speakers, one in a more similar to the studio environment and one completely wet. In the wet room, the speakers do indeed sound bright and a touch harsh. No 2 ways about it.

Well golly . . . just what I said (and you took exception to). I don’t, and don’t want to, live in an anechoic chamber. Of course every recording is different, and most are “corrected” so they sound at least acceptable in the typical “live” listening environment (on typical “consumer” speakers, in the opinion of the producer) . . . movies in particular are consistently equalized in anticipation of it. But movies are not expected to sound “real” . . .

"I want to hear what I hear at the concert of my favorite music."

If you have not been able to accomplish that then

my thinking was off base

would explain it. But you give up too soon, and your “fall back” of “flat everything” and simply suffering with inaccurate sound most of the time doesn’t satisfy a lot of us (including SL). What we are finding is that “flat on axis” generally doesn’t sound right (in a live room) unless off axis has a pronounced roll off. When we go to “constant directivity” (mostly to improve imaging and other psycho-acoustic effects on recordings where that’s even possible) the overall sound field becomes “bright and a touch harsh”. Some roll off, both on axis and off, mostly resolves that and leaves the improved spatial imaging and sense of realism. It doesn’t, as nothing can, resolve the problem of variation in recordings, and in mic placement, and it is less likely to work on synthetic “studio” recordings than it does for live symphony recordings. In a sense, then, it does depend on what music you chose to listen to. Some recordings won’t sound “balanced” until you listen with headphones (guess how they were mixed) . . . others won’t sound right until you listen on your boom box or in your car.

My own experience over the years and with a variety of loudspeakers (in the same listening room) is that “flat everything” is generally the worst and least satisfactory “compromise”. Hopefully you'll be adult enough to not take stabs at more ad hominem BS again after reading this. Just explaining my perspective. No reason for hostility adults. No one is attacking you.

Ps.

I know Deward and Auricle take offense to this(maybe some others as well), but it is not intentionally offensive. They take offense to everything I (or most people) say.

Just one more example where what you (think you) know is wrong. And intentionally offensive . . .

[dantheman]

Re: Flat Response

AJ, That's covered in group #1. Except with an EQ that could and pretty much necessarily needs to be there if the problems are modal. The only thing I've ever wanted to EQ in my room is a 140Hz bump and maybe the 40Hz dip just for sanity.


The modal region is such a pain. The old squeezing a balloon analogy comes to mind. To some degree, depending on how perfect you want to be, an EQ will come into play. I've been trying to avoid it.

The other reason I see for EQ is that some recordings just stink but you like the music.

Dan

[Zilch]

Re: Flat Responce

That said, why did you use 2 examples of an 8" 2-way speaker? I have been following, but unsure why. Thanks!

It's Geddes's data, and his choice for illustrating whatever he intends. Two-way #2 looks more like a 3-way to me, but his comment says not and that the system has an issue at 600 Hz. That's one heck of a wide-dispersion CD tweeter, too; ribbon, maybe? It'd be interesting to know the details, and since he is quite specific as to the particular models of the other "samples," he might be convinced to spill their IDs.

This thread is acknowledging the disparate design objectives (and capabilities) illustrated in Geddes's directivity maps, but no one has yet put quite the spin on it that I would. I do have data substantiating my case; it's largely a matter of presenting that in a manner minimally offensive to both principals and enthusiasts I have yet to work through.... :p

[dantheman]

Re: Flat Response

Deward, that wasn't what I took exception to. You were blaming it on the speaker not mimicking the live event like YOU want unless you've changed that since the last thread. I said it is diffraction and room problems. You even went so far as to say you didn't want to sit in the good seats b/c you think they might be too bright. That's not why I sit in the cheap seats, but there just no accounting for some people's taste. No well reasoned speaker engineering would try to mimic the sound of the cheap seats--ever. It's flawed logic from the get go. That's where we diverge--not what we hear, but what we attribute it too. IOW, we(you, me, AJ, and probably many others) believe in the same outcome (bright/harsh etc) of what I attribute too a lot of diffraction (in this case) and a wet room but different causation. You seem to believe that the speaker needs to have very narrow beam width in the top octave and much wider beneath it(correct me if I'm wrong here, but that's what I've gathered) and that will prevent harshness and provide you with a mimicked concert toward the rear of the hall. I say fix the real problems and enjoy the good seats at home. Do you really only listen to one type of music--live concert hall recorded classical that never went to a mixing/mastering studio? I don't even know where you find them. That was my problem with going that route--I listen to many things and even watch movies. My thinking certainly was wrong when I tried to duplicate that which is not on the recording. Thanks for repeating it, but I wish you would see why that will only work for a very few people and not something you should conscientiously recommend to others or openly promote as a good option. You already know that if you make your logic work once, you've automatically blown it for every other recording made without some serious fiddling(pardon the pun). I have a lot of recordings and want to enjoy them as close as I can to what was intended to be heard. I know YMV. I just hope others don't try and go down that path or if they do they realize it will require reworking for every recording they own and it's a crapshoot since they don't know what the original sounded like.

Dan

BTW, wise words Zilch. It seems everything I say causes offense no matter how hard I try. You are much better with words than I am so if anyone can do it, it is you. Just remember that excessive verbosity indubitably dissipates covetable semantic lucidity.

[Guest]

Re: Flat Response

Audio Engineering Society Convention Paper 6190
Presented at the 117th Convention
2004 Oct 28-31 San Francisco, USA

A Multiple Regression Model for Predicting Loudspeaker Preference Using Objective Measurements: Part II - Development of the Model
Sean E. Olive, AES Fellow

ABSTRACT
A new model is presented that accurately predicts listener preference ratings of loudspeakers based on anechoic measurements. The model was tested using 70 different loudspeakers evaluated in 19 different listening tests. Its performance was compared to 2 models based on in-room measurements with 1/3-octave and 1/20-octave resolution, and 2 models based on sound power measurements, including the Consumers Union (CU) model, tested in Part One. The correlations between predicted and measured preference ratings were: 1.0 (our model), 0.91 (inroom, 1/20th-octave), 0.87 (sound power model), 0.75 (in-room, 1/3-octave), and −0.22 (CU model). Models based on sound power are less accurate because they ignore the qualities of the perceptually important direct and early reflected sounds. The premise of the CU model is that the sound power response of the loudspeaker should be flat, which we show is negatively correlated with preference rating. It is also based on 1/3-octave measurements that are shown to produce less accurate predictions of sound quality.

Hi Dennis,

Ok, you got me....what are you implying with that link under my quote?

Sean/Harman subscribes to my school (or is that vice versa?:D).
Check any of their products

http://www.jblpro.com/catalog/suppor...pe=3&docid=858.



Let's just be perfectly clear and rewind the tape here. This is what the OP said:

I would like your opinions on actual vs. perceived flat frequency response. Some say a flat response sounds to forward or even harsh when auditioned in typical listening rooms,
yet it seems a flat response is an important design goal for many designers.

Clearly, we(?) are talking about a "flat on axis" acoustic source...not "flat" at the listener position, measured in a reverberant room, response...yes?

cheers,

AJ

[Zilch]

Re: Flat Response

Now that's an interesting set of comparison measurements. The Behringer Monitor seems to be ever so slightly smoother overall than the Geddes Nathan.

And wider dispersion, midway between Nathan and Orion.

The relative difference in perception would be really interesting as a followup.

Indeed; I'm just not set up to do that here, and like Geddes, I conveniently don't do "How's it sound." ;)

The Orion dipole response certainly reduces the low end influence with the room analyzed in isolation, but that does not by itself define the goal of each designer, especially since the low end response in isolation is overlooks the fact that it is a system, not just a low end producer.

The dipole response is clearly not delivered with the specificity illustrated in theoretical characterization of it.

You may want to completely ignore Geddes graphs that Zilch posted because the data, at least for the Orion, is completely flawed. The front and rear graphs for the Orions should look identical below 200Hz, but they are far from it. When I questioned Geddes about this he didn't have an answer why this was so.

It's a brave beginning; the burden falls upon others to present data to either confirm or confute it. If prior experience is any indication, none such will be forthcoming.

I've read enough to understand that duplicating a live performance of acoustic instruments is a waste of time, so why try?

Perhaps so, and consistent with my own view. The prospect of its ultimate accomplishment is intriguing, but it'll likely require a fundamentally different paradigm.

The one fact is, everyone 'hears' everything different, it is up to the individual to decide to enjoy it or not, or spend the rest of there life trying to find there personal 'audio nirvana'!

In one of the YouTube presentations of his lectures, Linkwitz tells us otherwise -- we hear the same, but LISTEN differently, is all. Whether this insight is profound or merely clever is for each of us to decide for ourselves.

No reason for hostility adults. No one is attacking you.

Are we getting close to a group hug yet? :D

The only thing I've ever wanted to EQ in my room is a 140Hz bump and maybe the 40Hz dip just for sanity

Assuming that's in-room response, despite their flat anechoic (or quasi-) axial response and constant directivity, the downward tilt of higher frequencies due to room absorption, interference, and diffusion is quite apparent.

Clearly, we(?) are talking about a "flat on axis" acoustic source...not "flat" at the listener position, measured in a reverberant room, response...yes?

A significant distinction. I believe everyone understanding the difference acknowledges that flat in-room response is "overly bright." The only ways I know to get there are flat power response or boosted axial high frequencies, which was (and still is, commonly) used to compensate for the falling off-axis response of conventional domes.