Well, I am thinking about something...

This is abstract, so no real advices needed

When having problems with your room for listening, boomy bass, too bright highs, you have few options:

1. room treatment to eliminate most of the causes for these effects
2. seting up equilizer so you can flatten a bit these effects

And there is also a possibility of measuring with microphone measurement systems, which is expensive, I know.

These measurements are what I am interested in. As far as I know, when measuring, you have to compensate the measurement curve with the curve of the microphone which is measuring. but what is the exact procedure?

Playing back full spectrum white noise, setting up microphone where the listener will seat, and then measuring and correcting as needed with equalizer?

If I am correct, does the measurement needs another compensation, and that is of huuman hearing? If the goal is (as) flat frequency response as you can?

is "equal loudness curve" measurement needed, and do they need to be included?

I am thinking about these.

This is the correct solution.


That doesn't work for many reasons, as explained here:

Audyssey Report

One big reason is that room acoustics problems are timed-based as well as frequency-based. Another is that the response changes drastically over distances as small as a few inches. An equalizer can't even get the response flat for both of your ears at the same time.


A decent microphone does not have to be expensive:

Comparison of Ten Measuring Microphones


ETF, Windows, $150
FuzzMeasure, Mac, $150
Room EQ Wizard, Windows and Linux, Freeware
This article explains how I use ETF, but the principles apply to all such programs.


Most of the inexpensive microphones shown in my article above are flat enough to be used as is, with no compensation needed.


No, all that matters is measuring the raw response.

--Ethan

I have no issues with the bass traps you sell, but I must correct several misleading statements in your post about "your competition": Parametric EQ. Bass traps and EQ work best as a "team", IMHO:

Parametric EQ is much more efficient than bass traps in eliminating bass peaks under 80Hz. measured at a sweet spot listening seat common with a two-channel audio system. EQ can't fix the whole room, although an EQ setting for one seat will usually improve the frequency response at nearby seats (distant seats may sound worse).

EQ is not effective for nulls ... but in home audio what listeners usually notice are the "room booms', not the nulls. Bass nulls are much easier to hear if you sit "in the middle" of a large room, such as a sound engineer mixing a recording. Bass peaks are much easier to hear if the listener is close to walls and corners, which is much more likely in a relatively small home audio room.

No subwoofer should be used without parametric EQ.
Almost all sweet spot seats can benefit from one to four bands of bass EQ, and sometimes one EQ setting will benefit several listeners at various seats in the same room.

The alternative to EQ is A LOT of bass traps that few audiophiles will use unless the room is dedicated to audio, and they don't mind looking at a lot of bass traps!

It's true that absorbing reflections is true solution, while EQ is an electronic band-aid -- but EQ is also a very efficient band aid for the powerful first order axial room modes, where bass traps are very inefficient.

The measurements at two ears (I use mics 8" apart) for any given seating position will be very similar for bass tones with one exception -- a side-wall to side-wall room mode can sometimes measure differently at both ears. But so what if a bass peak is a little louder at one ear than at the other?
Don't we hear the average loudness for the bass frequencies, and couldn't we set the EQ for the average SPL of two ears?

It's usually pink noise. For measurement purposes, the frequency band is usually divided Logarithmically. This means you need "equal energy per octave". (And, it's easier on the tweeters than white noise.)

My (older) equalizer has a spectrum analyzer, a pink noise generator, a microphone input, and it came with a microphone. (Similar in concept to this.)

Well... It's a different issue... Perfect speakers in a perfect room will remain "flat" at any volume level. But, you can use the same equipment to measure/calibrate acoustic levels with the digital/electronic levels and then adjust/calibrate the loudness compensation... If you saw this post, some receivers come with a microphone and software (firmware) to equalize the system/room and to calibrate loudness compensation.

The advantage of acoustic treatments over an equalizer is easy to see if you can follow this logic:

(1) The sound field in a room is full of variations. Everyplace in the room is a little different, and if you move about in a room you can often hear the sound quality change.

(2) A equalizer can only address the frequency response at one point in a room.

(3) Acoustic treatments can address the frequency response at many points in the room.

(4) Therefore, acoustic treatments are superior to equalization, unless you only want to have good sound quality at just one point in the room.




Simply not true. Good mics for the purpose start at about $50. Computer software freeware of several kinds can be used to do the analysis on just about any PC.

The first rule of acoustics is "don't put energy into the space if you don't want it there".

Bass NULLS (as well as bass booms) are evidence of strong energy storage. So both indicate that you need to do something to remove energy from the room, NOT add more, for instance. If you're sitting at a bass null in a room (and you don't have some odd speakers that create such a thing) you are sitting at a volume velocity maximum, which is to say that all that energy is there, but it's in the volume phase of propagation, instead of the pressure phase. So don't add more energy, you've got lots already, in fact too much and in the wrong place.

So treat the room.

Now, for high frequencies. Most rooms attenuate high frequencies faster than low frequencies, in fact, even air does that. So the t60 (time required for sound to drop by 60dB at some frequency) is shorter at high frequencies. This means that if you put equal energy into a room at all frequencies, the different t60 will result in a long-term measurement that shows that high frequencies are missing, when in fact they are NOT missing in the direct signal from the speakers.

On top of that, most speakers are much more directional at high frequencies (although designing speakers otherwise above a few 100 Hz is not so hard, most designers don't bother, it costs money), and as a result, the total power output of the speaker is smaller at high frequencies.

The combination of these two effects means that if you use a long-term pink noise equalization in a room, the direct signal at high frequencies will be way, way, way, way, way (while 1 printf("way ")) too high if you just set the long term EQ to flat.

What to do is much more complex. One part of that is addressed in the paper I wrote with Serge Smirnov a few AES conventions ago. It's a bit long to reproduce here.

Let's assume I set up my room for a perfect flat response. Now there's still one factor: my own ears. Would it be wise to alter the EQ to compensate for hearing weaknesses of the listener himself (i.e. boosting high frequencies for older people)? Is there a calibration standard/method for this purpose?

What kind of "perfectly flat response" would you set up? Direct? Averaged? What?

Dunno, I think they serve kinda different purposes too. "Room correction" (MCACC from Pioneer) has been invaluable to me to blend the response of my speakers. I have very different speakers for fronts, center and surrounds. With MCACC off, they sound very different as well, as expected. You can't do that with room treatment.

Not at all. You want to hear from your audio system what you would hear at a live performance. In both cases, the frequency response of your ears is the same.

When it comes to acoustic treatment vs. EQ, I'd say that having it right at one spot is sufficient since I bought this equipment for one person (myself!), but a room's acoustic errors are not merely a question of volume. Reflected sounds do not only amplify, they also come from the wrong direction and at the wrong time. An EQ only fixes volume.




Well, the ear's sensitivity is of course volume-dependent. You could of course tune to precisely the volume which sounds most "live", but for some of us that is simply not an option


- Porcus
(metalhead with earplugs and neighbours)

I never saw EQ as "competition," and in my Audyssey Report linked above I mention that I use a one-band cut-only EQ to cut a few dB around 40 Hz in my HT system.


It depends a lot on the size of the room and where one sits in relation to the rear wall. In my experience nulls are the larger problem, at least in a small room.


Again, it's more a function of where you are in relation to the rear wall behind you. The first graph below was measured in a 16' by 10' by 8' untreated room, and you can clearly see the huge nulls at 82, 120, and 155 Hz.


Agreed. But if audiophiles and their spouses are willing to accept the look of huge tower loudspeakers, with power amps and other gear on pedestals in the middle of the floor, with speaker cables as thick as garden hose on cable elevators, then why not acoustic treatment? I happen to think bass traps look really cool, though I understand that not everyone else feels the same way.


If only. Maybe your measurements are displayed with third-octave averaging? The second graph below shows the response I measured in a different small room (16' by 11.5' by 8') at two locations four inches apart.


Exactly. EQ cannot remove echoes at mid and high frequencies, or reduce the resulting comb filtering.

--Ethan

Source: Acoustics: Good or Bad Vibes?


Source: A common-sense explanation of audiophile beliefs

I believe the charts you have displayed are at least not typical
of home listening rooms, and possibly not correct.

The first chart you display has unusually flat bass frequency response
that suggests the use of pink noise rather than individual sine wave tones.

That chart does not represent what I have measured at typical listening positions
in a variety of typical home audio listening rooms over several decades.

Your chart implies parametric EQ would not be useful under 80Hz. in a typical room.

I believe that implication is misleading for up to nine out of ten typical home listening rooms.

Your second chart is hard to read, but implies large deviations in bass
frequency response SPL with microphone measurements only 4" apart.

I find it hard to believe those measurements are typical of a home audio
listening room, and question the measurement methodology.

Once again you are suggesting a parametric EQ could not be very useful
for bass frequencies because a small change in mic position results in
a large change to bass SPL.

In fact, for front-wall-to-back-wall standing waves,
one EQ setting will work well for everyone sitting across a listening couch.
Their ears will all be the same distances from the front wall.

In fact, for floor-to-ceiling standing waves,
one EQ will work pretty well for three male listeners of similar heights on a couch.
There ears will all be similar distances from the floor
and the "perfect" EQ setting for each person could be different, but all would be similar.

For side-wall-to-side-wall room modes,
three listeners on a couch would need different EQ settings,
although the people on the left side and right side of the couch
may not need EQ at all. The person in the middle of the couch,
assuming the couch is halfway between the side walls,
would have his ears near the trough of that standing wave
so EQ couldn't help him.

I have been measuring bass frequencies using sinewave tones for over
two decades, averaging measurements made 8" apart
(averaged to represent what my two ears hear).

I rarely have 8" apart measurements more than a few dB's different,
with the one exception I previously mentioned (side-wall-to-side-wall
room modes).

The physics of subwoofer bass frequency sound waves
that are 15' long, or longer, strongly suggests a 4" change
in microphone position will make little difference in SPL.

The only way a small change in microphone position
SHOULD show a large change in SPL, would be
when the mic is moving in and out of a deep null.

And that is exactly what I have seen in several decades
of bass SPL measurements made 8" apart.

You sell bass traps and are very positive about them.
I agree.

You don't sell Parametric EQ's and seem unfairly negative
on how useful they are to eliminate bass peaks measured
at one sweet spot seat (most useful for two-channel audio)
and sometimes useful for bass peaks heard at several
seats.

That EQ can only be useful for one point in a room is a myth.

The charts you presented contradict two theories about bass:
- Bass frequency response under 100Hz. tends to be
uneven in most home listening rooms
- Large wavelength tones are not affected much by small changes
in microphone position

In my opinion, the theories above are correct,
but your measurements are at best are not typical of home listening rooms,
and at worst are misleading about typical home listening rooms.

My reality is that bass frequency response is rarely as smooth as
your first chart showed ... and a 4" mic movement rarely changes
the measured SPL of 15' and longer wavelengths as much as your
second chart implies.

I do not sell any audio products
and have no bias for or against
bass traps and parametric equalizers.

I hope arguments are allowed here at Hydrogen,
because I may have just have started one.

I agree with this, but I think we need to understand some reasons why that I odn't think have been mentioned.

One issue is room size. Smaller rooms add an approximate +12 dB octave bass boost starting at a frequency that is inversely proportional to their size. IOW a really small room adds bass at a frequency that cuts in at a fairly high point such as over 120 Hz.

Another issue is the nature of the space that the speaker sits in. The extreme case is a speaker hanging in space which is also called a full space. There are no surfaces to supoort the reproduction of bass, and the actual bass response is about as poor as can be. The next option is a half space, such as sitting in the middle of a large room. Better, but not exactly typical. OTOH, a speaker that is sitting out a few feet into a room will not have as much boundary support as one pushed up against the wall or in the wall. Next we have the quarter space, which is like a speaker along a long wall, but right at the floor. Finally we have the corner location or 1/8 space, which supports bass so well that it often ends up providing too much bass too much for many spekaers.

While most room locations that are actually used come in someplace between quarter or eighth space, real world situations are rarely pure and simple.

Note that both of these situations can be better managed with parametric equalization, but neither can be criticized on many of the grouds that have been mentioned as potential failings for equalization. IOW since they are commonplace, they may be some reasons why there is a widespread perception that equlizers can be very helpful with subwoofers.

Ok in comparison to a live performance you attended you want to hear the exact same thing.

But what about studio recordings? So lets say you can't hear anything above 10khz. But the musican did, and he tuned everything to sound as good as posible with a spectrum up to 16khz. That means you can't experience the whole composition the way the creator did. So why not boosting these upper frequencies until you can hear them too (avoiding clipping and the like of course)?
Such a system will be tuned to a single persons ears and to that person it'll be the way the artists heared and intended it (in theory). For everyone else it's probably just awful.

I would guess this is a bit a matter of reference, and what is subjectively missing from the reference. On one hand, it shouldn't matter if two pairs of ears are "different", as your ears form your sonic reference. If you for sudden were to hear a voice the way I hear it, it is not given that it sounds more natural. People fail to notice their own bad breath, because it is sneaking into their own reference, but everyone else (whose noses are adapted to clean air, or at least different stinks ), will sense the difference?

Then on the other hand, if your hearing is starting to change, you will maybe want to tweak the tone controls. And who hasn't noticed a senior citizen who was shouting louder and louder until finally realizing that a hearing aid was appropriate -- then [s]he suddenly acquires a calm, quiet voice? (Speaking of which: are hearing aids very hi-fi? It would surprise me if they were. I suppose most users don't care, with a plug in only one of the ears ...)

Earl Geddes, whose measurements I trust more than mine, says that his measurements demonstrate that home listening rooms, in general, are not sealed well enough to have a 12dB/octave bass ramp-up from cabin gain like cars do with their windows closed.

The biggest problem with bass traps is few people will use enough of them to make more than a small improvement in the bass frequency response. Using an inexpensive digital parametric EQ dedicated to a subwoofer or two, combined with some bass traps, seems to be a good compromise.

Even E. Winer does this, and he sells bass traps.

But I can't understand why Winer seems to think bass nulls are as much of a problem as bass peaks, at least under 80Hz. -- it's easy to overlook a weak bass note while listening to full-range music but not easy to overlook an excessivley loud bass note. And if a repeating kick drum "note" excites a room mode, you may hear a repeating bass boom that's MUCH easier to notice than a problem from a bass null.

I haven't figured out how to equalize "the room" above the subwoofer range, in a way that makes the sound quality better ... but I've significantly improved my frequency response under 80Hz. from using parametric EQs with my DIY subwoofer(s) going back several decades.)

A null implies that there MUST be a peak somewhere else in the same room. A null is just as much evidence of too much energy storage as a peak.

First, I posted the wrong graph yesterday. I meant to post this one, which shows a very large disparity over distance at frequencies as low as ~60 Hz and even lower:



Every graph you'll ever see me post is real and as measured. The first blue one was made by recording sine waves at 1 Hz intervals. That was five or six years ago before I bought real room measuring software.


Well, please post a few of your own, and tell us the size of the room, and we'll have a good basis for discussion. But understand that what people usually measure - with 1/3 octave averaging - is pointless at low frequencies in a small room. You need much higher resolution to see what's really going on.


Yes, and that's my point.


Most of the graphs I post were measured with the ETF software, though I switched to Room EQ Wizard about a year ago. REW is freeware, so everyone can afford it!


Bingo.


This article shows measurements like that - front to back, left to right, and low to high:

Do Room Modes Even Matter?

Do you measure with sine waves at 1 Hz intervals, or only at the standard 1/3 octave center frequencies?


Debunking that myth is exactly why I did those measurements! The (correct) LF graph I show above in this post was measured in a room 16 by 11.5 by 8 feet high. Full detail of a day's worth of exhaustive measuring to assess EQ versus bass traps is here:

EQ Versus Bass Traps


You got it! But nulls are prevalent, and deep, and occur all over the place in a small room. Here's another attempt to debunk the conventional wisdom:

Non-Modal Peaks and Nulls


Sure, but to be perfectly clear, I sell bass traps because I believe in them, not the other way around.


Yes, I am negative on EQ for LF room acoustic problems. But it's based on 40-odd years of experience, and has nothing to do with what I currently do for a living. Again, I agree that EQ is okay to reduce an obvious booming mode, but it can't help nulls and it can't help ringing. Both of those are at least as damaging as peaks.


Tell you what, do some tests similar to mine in the EQ Versus Bass Traps article. If you're right and can make your case, I promise I'll change my opinion in a heartbeat!


As I always say, Empirical evidence trumps theory every time.


I know Richard, we already covered that. I'm not biased either. If EQ really worked as well as the vendors would like us to believe, I'd sell EQ instead of bass traps (or in addition to bass traps). I know how to design an EQ too.


No way Richard! I know you from other forums, and you're one of the good guys who actually understands this stuff. Disagreeing is not the same as mud slinging and insults! For examples of that you need only visit the General section at Stereophile's forum.

Again, I'm glad to discuss this to the point where either you convince me or I convince you, or a little of both.

--Ethan

RG:
Winer, it's impossible to "win" an argument with you because you contradict yourself in every post!

In an earlier post you said room EQ is no good ... and then you contradicted yourself by saying you use EQ for one bass room mode at home ... so then EQ is good? ... and then in this post (quote above) you say you are negative on EQ for low frequency room acoustic problems ... and then you contradict yourself by saying "EQ is okay to reduce an obvious booming mode" ... so then EQ is good? This is like a debate with an "on one hand ... and then on the other hand" economist!

So I'll sum up my case as follows:
(1) Your're wrong
(2) If a listener hears one or more bass booms under 80Hz., and would prefer to hear the bassline as played by the bass musician, then he start making improvements by eliminating every bass boom in his subwoofers range with a band of parametric EQ. The resulting bassline will sound more like what the musician intended, although there will still be partial nulls under 80Hz. (partial nulls CAN be eliminated with parametric EQ in theory, but are very difficult to EQ in practice because small movements of the listener's head would significantly change the required EQ setting)

While the "correct" solution to uneven bass is to absorb bass reflections using a lot of bass traps, few audiophiles actually use a lot of bass traps in their room.

That's why many subwoofer owners, for as little as $100, have purchased a digital parametric EQ and experimented with it.

In my experience, a subwoofer owner using a digital parametric EQ will be able to get a more accurate bassline, heard at one seat, in roughly nine out of ten rooms.

This improvement is easily documented with measurements of sinewave tones spaced 1 Hz. apart, and also audible with a slow sinewave frequency sweep from 20 to 100Hz.

The fact that so many high-end subwoofers of many brands have been including one or more bands of parametric EQ in recent prioducts suggests there IS some use for EQ with bass frequencies, and I'm not the only person who thinks so.

I've been using and recommending parametric EQ with subwoofers for two decades.

Agree with me now -- it will save so much time!

So listen to the live performance at the same level at home.

Can I get a massive "Dooooh" here? ;-)




They don't have headphones where you are?

Strange....

Yep, Etymotics and Staxes, but they don't deliver realistic sound pressure to my stomach. Or in the case of Sunn O))), to my calves.

On the one hand you're correct, but, oh wait, nevermind.

Seriously, it's not black and white. EQ is a second-rate solution, but that doesn't mean it's never useful. But it is useful only for 1/4 of the applications EQ proponents claim.

Bass traps:

1) Reduce peaks
2) Reduce nulls
3) Reduce ringing
4) All the above improve everywhere in a room, and never made worse in some locations

EQ can only do #1, hence my 1/4 rating above.


See, we agree much more than we disagree. Though I'd set the crossover closer to 60 Hz, or even 50 Hz, depending on the room size.


The obvious solution is education. And more attractive bass traps. You can easily hide bass traps behind false fabric walls, but that costs more. You can hide speakers and wires too, and that costs more. It's not my problem or fault if some people refuse to pursue the most effective approach. The fact remains that bass traps are better than EQ, whether "most" people are willing to accept the appearance or not. The good news is more and more these days people have dedicated rooms, where "spouse acceptance" is not a problem.


By that logic, 96 and 192 KHz sample rates are "better" than 44.1 because companies sell that gear and people buy it. I hope you see the logic flaw there.

Richard, agree with me now, it will save so much time.

(Just kidding.)

--Ethan

Sorry, people, I haven't had much free time last few days, I've read posts, but couldn't really answer.
You all took my question too serious, which is good, i like serious threads

I'm not treating my room, nor I have need to do it - I'm a casual music listener, not really an "audiophile", I care more about what the musician has to say than what the speakers deliver I like to have quality sound, but I don't have to have 10000$ speakers to hear knopfler's guitar "just right", so to say.
But that's beside the point.

I was arguing on one usenet group, because I had this thought that you could correct room imperfections with EQ. I see now that it is rather complex business, and at first I should correct the room's response first. Let's say I do it, but couldn't do it 100%, but let's say I do 60 % of whatever it could be done, because my wife nags There is still 40% of work to do, but I can't place any wooden planks anymore, or whatever gadget needed for that.

And my thinking - I'd buy an parametric EQ, get measuring equipment, and measure the response from the listening armchair - correcting where needed. Now I have done all it could be done, given the situation. Am I right? (I am not trying to get perfect results, more a real-life situation)

If I am right, and I think I am, still the question remains, and I didn't get the concise and explained answer - do I also need to correct for my hearing measurement? If I am to listen to flat frequency response, is it needed or not? And more importantly, WHY?

Thank you - and please don't fight

The single best thing you can do to improve your listening situation is to get 2-inch thick acoustic panels and put them at the side-wall reflection points.

I have what I consider a fabulous system. Two in fact. Neither has $10,000 speakers. But both systems have highly competent and affordable speakers, plus extensive bass trapping and other treatment.

--Ethan

That's probably correct. I live in a 5 year old apartment next to a busy downtown street in central Oslo. Average noise level right outside the apartment is 75dB. Building regulations require that the average indoor noise level is a maximum of 42dB. "Sealed" is a good word for the feeling you get when you close a window or the balcony door. Still, the bass boost in the room (at 50hz) is about 10dB, not 12. I would assume the peak in most older apartments / houses is less.

Anyhow - regardless if the boost is 6, 10 or even 12dB - as was mentioned earlier in the thread, EQ is very useful to reduce this effect.

Ethan, did you read Floyd Tooles book "Sound reproduction, loudspeakers and rooms"? If so, what do you think about his comments on "Apparent source width" and the desirability of side-wall reflections and/or artificial (delayed) side reflections?

-k

It wouldn't make that much difference. It's also moderately probable that the musican was so hearing damaged due to his occupation that he couldn't hear anything above 5 KHz.



Musican's rarely, if ever hear the performance like the listeners do. Most of the time they hear primarily themselves playing, and possibly listen to one or two other performers.



Your example shows little experience with performing music or producing musical recordings. Nothing you talk about happens the way you say.

Knowing Earl's house as I do, that would be true there for many possible locations other than his actual multimedia room. His media room in the basement seals up like a vault.

My prime listening room has so many big holes in it, we can't even tell where it ends and several other rooms begin.

But that's one set of extremes. A bedroom or study turned into a listening room or a home studio could be a counter-example.

That's ture for musicans playing instruments, but what about music generated on synthesizers and computers? Most electronic music was created and heared by the author the same way the listeners does in the end. But even for traditional music there's some guy in the studio listening to it and turning the knobs until it sounds right to him.

If some kind of standard hearing calibration would be used from mastering to playback, then everybody could hear the same thing (in theory). Think of it like calibrating your monitor to make colors look the same on any device.

YOU WROTE:
"Bass traps:
1) Reduce peaks
2) Reduce nulls
3) Reduce ringing
4) All the above improve everywhere in a room,
and never made worse in some locations"

RG replies:
In spite of the fact that you are holding a huge cat
in your picture, and I like cats, I will continue to
argue with you until you give up and admit that
I was right all along.

Bass traps reduce reflections that cause uneven
frequency response when the reflections arrive
at the ears in-phase (peaks) or out of phase (troughs)
with direct sound from the speakers. Bass traps are
less efficient as frequencies that need to be absorbed
decline. That's where the EQ "band-aid" becomes very
useful -- parametric EQ is easier to set and more useful
as frequencies decline -- parametric EQ works best where
bass traps are least efficient.

You have taken the one accomplishment of bass traps
(absorbing reflections) and created four accomplishments.
I have a problem with "reduces ringing" which seems to
duplicate "reduces peaks" and reduces (partial) nulls"

You may not realize that EQ "reduces ringing" too.

If you had a large +6dB bass peak in the 40 to 45Hz. range
at the sweet spot listening seat, those frequencies would be
too loud and fade to inaudibility too slowly.

If you eliminated that +6dB bass peak with parametric EQ,
the frequencies would no longer be too loud and they would
fade to inaudibility faster.

In plain English, that means EQ reduces ringing too.

Floyd Toole has discussed reduced ringing from the use of EQ in one of
his many white papers, so I'm not the only one making the claim.

Because bass traps are inefficient at the lowest frequencies,
and the lowest frequency room modes (first-order axial) tend to cause
the loudest bass booms, most people who use bass traps will not use
enough of them for those lowest frequency room modes, so will benefit
from the supplemental use of an inexpensive digital parametric EQ dedicated to
a subwoofer ... or a more expensive parametric EQ used with full range speakers.

And my cat could beat up your cat if he wanted to,
but he's sleeping now.

If its being done interactively in real time, then there's no difference.



Now you are in essence talking about the tiny minority of music that is performed by what is in essence, a one man band.



That guy could be me. What I do is not in any way comparable to playing or singing music. Furthermore, if I mixed through a 10 KHz brick wall low pass filter, there would not be that much difference in how I would mix as compared to how I would mix if I could hear clear up to 45 KHz. The bottom line is that there is very little in music that happens above 10 KHz that can't be well managed by listening only to what is there below 10 KHz.



Again, this is not how the real world works. Well-made recordings are usually made so that they sound as good as possible on a variety of audio systems from a portable player to a car audio system to a boom box to a high end audio system. The nature of hearing and music is such that this is not mission impossible.

I have not read the book, but I'm aware of his position. I disagree pretty strongly, and so does everyone else who has heard my living room system with and without side wall absorbers. However, in a large room, reflections from the side walls and ceiling (and floor) may be less damaging and thus more tolerable. I haven't experimented with that yet. My living room is 25 feet front to back and 16 feet wide. My home studio is 34 feet front to back and 14 feet wide at the mix position. In both of these rooms absorbing the early reflections sounds much better than not absorbing.

To me the issue is being faithful to the intent of the recording engineers. All of the ambience and reverb needed and wanted is already in the recording. You can clearly hear this "large" sound with earphones. But when played in a small room, early reflections drown out the embedded ambience and make the sound smaller. I want to hear what the mixing and mastering engineers heard! And in the majority of cases they worked in a room with reflections absorbed, or a large room with the side walls angled to deflect the reflections away from their ears without needing absorption.

This comes up so often that last week I made a video to let people hear the difference. I bought a bunch of Masonite panels and stuck them over my existing absorbers, then recorded music at the listening position with and without the panels in place. Sadly, there wasn't as much difference in the recording as I had hoped, so I decided not to add the video to our site. You can hear the difference very clearly in the room! So I'll continue to think of ways to convey that in a video. In the mean time, the video is on my company's site, but hidden because it's not linked. I'd be glad to get opinions from this forum. So here's the link, and please let me know what you think:

First Reflections

--Ethan

Back atcha pal.


Yes, of course. But bass traps can be effective to as low as 30 Hz if you have enough of them. In the video Hearing is Believing on my company's site you'll see a roomful of bass traps have a profound effect on the response and ringing of the lowest peak near 40 Hz. For people that can manage only a "normal" amount of bass trapping, they can still get a meaningful improvement to below 80 Hz.


I already agreed that at very low frequencies EQ is acceptable. I also already stated that I use a one-band cut-only EQ in my own living room HT system.


No, these are separate achievements. EQ can reduce a peak but it does not change the decay rate. Only bass traps can do that.


Yes, and no. Severe ringing muddies the sound of bass instruments because notes the player stopped half a second ago continue to sound in the room. So if you play an ascending scale cleanly on a bass, it will be muddier in the room as notes continue to sound, and overlap, subsequent notes. Yes, the volume aspect of the peak may be improved, but not the muddying overlapping effect. This is an important distinction that is readily audible. Well, it's readily audible if you're a bass player.

It's worth mentioning that a room resonance that extends the decay also slows the attack. EQ can't correct that either.


I have never seen conclusive proof that ringing can be reduced in practice by EQ. I accept that it can happen in theory, but only for a very small location in the room. Move the microphone even an inch or two and the critical balance needed no longer exists. I've tested this twice now! I'm sure I linked to those articles, but here they are again:

Audyssey Report
EQ Versus Bass Traps

If you'd like to run your own tests and prove otherwise, I'll be glad to learn something new. But if you do this test and show ringing being reduced, please move the measuring microphone one foot in different directions and measure again (without changing the EQ). If you can't get rid of the ringing for both ears at the same time, let alone for the next seat over on the couch, then it's not useful in practice.


In some cases the second harmonic is worse because normal construction lets very low frequencies through the walls. At least that's the case in my own living room.


Again, that's their problem and their decision. If someone wants truly excellent sound, and is willing to pay for it, the best solution is lots and lots of bass traps optionally hidden behind attractive faux walls.


Your cat could probably beat up my cat even while sleeping. My precious monster Bear is about 18 years old, overweight, and his only motivation is eating.

--Ethan

I think you need to define "measurement" before there can be consensus on this. In some cases a too-coarse measurement or one that does not factor in time response can lead you astray. Some insist that the ear is the most/only valid measurement system.

Generally speaking, EQ holds the potential to improve things at your reference point with the possible side effect of making things worse other places in the room.

Those practiced in the art of setting up rooms know to make multiple measurements and to be wary of extreme EQ settings. If they can't get reasonable uniformity or if they need to lean too much on EQ, they'll go back and do another iteration of room treatment.

I can't hear an obvious difference in the recording. I'm going to guess that the reason that it is obviously audible in the room is because it is a difference you notice when you move your head. The early reflections in a small room will cause comb filtering. Moving your head will slide the combs around. This is a natural thing that happens in real spaces and so we naturally hear around it; some listeners may actually use it to hear better and may be unsettled when it is not present.

I do appreciate that when listing to a reproduction in an undeadened room you're hearing (at least) two rooms. Most of the mastering and mixing suites I've seen are set up like your room so you're definitely hearing it like the professionals do. However, these professional do realize that what they're doing is critical listening and understand and compensate for the fact that most listeners will not be reproducing the material in such an environment nor listening in this critical way.

I ORIGINALLY WROTE:
"If you eliminated that +6dB bass peak with parametric EQ, the frequencies would no longer be too loud and they would fade to inaudibility faster."
YOU WROTE IN REPLY:
"Yes, and no. Severe ringing muddies the sound of bass instruments because notes the player stopped half a second ago continue to sound in the room. So if you play an ascending scale cleanly on a bass, it will be muddier in the room as notes continue to sound, and overlap, subsequent notes. Yes, the volume aspect of the peak may be improved, but not the muddying overlapping effect."
RG REPLIES TO THE REPLY:
First of all, a bass note may include half the total sound energy, or less, at the fundamental frequency, and half or more at harmonics of that frequency.

The parametric EQ is used mainly to reduce the SPL of the fundamental frequency, while bass traps are needed for acoustics problems affecting the harmonics.

In addition, early reflection sound absorbers may be needed to address acoustics problems affecting the attack of the bass note, which will be in the mid-range frequencies (the "pluck" of a bass guitar string, and the "slap" of a kick drum, for two common examples, are not in the bass frequencies, and could cause some distracting early reflections off the side walls, floor and ceiling.
.
YOU WROTE:
"It's worth mentioning that a room resonance that extends the decay also slows the attack. EQ can't correct that either."
RG REPLIES:
Irrelevant.
Bass note attacks are in the mid-range frequencies and the mid-range frequencies are not relevant for a discussion of problems with standing waves in the sub-80Hz. frequencies.

A typical room mode in a home listening room will attenuate by 30dB in 200 milliseconds (-30dB is my definition of inaudibility -- in reality deep bass may become inaudible faster because low frequencies are hard to hear at reasonable SPLs to begin with).

If a bass note fundamental frequency peak is reduced by 3 to 6dB using a parametric EQ, the decay of that note will fade to inaudibility faster (than 200 milliseconds).

If you want to call the decay "ringing", then the ringing will not reach the same SPL peaks after EQ, AND will fade to inaudibility faster. This will happen whether you agree, or not!
.
YOU WROTE:
"In some cases the second harmonic is worse because normal construction lets very low frequencies through the walls. At least that's the case in my own living room."
RG REPLIES:
True, and those second harmonics are the frequencies where bass traps are more efficient and more useful.

And if my wife was reading this, she'd think bass traps had something to do with fishing.

Yes! The last time I measured my Fender bass when plucked at the usual position over the pickup, the fundamental was about 10 dB softer than the second harmonic. And that's ONLY the second harmonic. As I said earlier, the speaking range of bass instruments is mostly 80 Hz and above.


I don't know how many times I have to repeat that bass traps can target down to 40 Hz and even 30 Hz if they're good traps and you have enough of them.


OMG that is SO wrong! Look at this graph showing the ringing in a bedroom size space 200 Hz and below:



Every one of those peaks that decays slowly also rises just as slowly. Low at the huge one right at the right edge of the graph at 200 Hz, well into the "harmonics" range. Again, peaks that take 300 ms to decay also take 300 ms to rise. An A at 110 Hz on a bass has most of it's energy at 220 Hz. This is hardly midrange. Further, midrange ringing matters a lot too!


I've been talking about fishing all along. You mean to say you haven't?

--Ethan

I WROTE:
"Bass note attacks are in the mid-range frequencies and the mid-range frequencies
are not relevant for a discussion of EQing bass peaks in the sub-80Hz. frequencies."

YOU REPLIED:
"OMG that is SO wrong! Look at this graph showing the ringing
in a bedroom size space 200 Hz and below"

NOW LET ME SAY THIS ABOUT THAT:
The attack of a bass note remains in the mid-range,
whether you believe it or not.
Since I have been discussing the use of parametric EQ
in the subwoofer range (under 80Hz.),
there is no reason to discuss the bass note "attack"
because it's way above a parametric EQ's useful range.

The chart you presented could not have been better ...
... to support my case:

It shows two room modes under 80Hz.
that will usually need parametric EQ to control,
because very few audiophiles use enough bass traps
to absorb reflections at those frequencies
(in 43 years as an audiophile, I've only been in
ONE listening room with enough bass
traps to control the lowest room modes)
... and your chart also shows many room modes
above the EQ's useful range, meaning that
bass traps are still needed, whether or not
EQ is used to fight bass peaks caused
by the first order axial room modes
(at the lowest frequencies where bass traps
are least efficient).

Agree with me now --
it will save so much time.

RG

Guys, yes, most of the attack isn't below the Schroder frequency in most any listening room at home. It's also in the low midrange. BUT

I repeat BUT hangover in the bass region will remove the time alignment of the bass sensation with the midrange components of the attack.

So both matter. Goodness.

Just for fun I replaced the bass track in one of my recent pop tunes with a synth set to play pure sine waves. The tune is in A, so the main bass notes you'll hear are 110 Hz, then the F below (87.3 Hz) when it changes to that chord. Now, this isn't the best bass tone in the world, and without any overtones it's not as clear as I'd use for a final mix. But I think it makes the point that bass punch and clarity can happen well below the midrange:

Lullaby Excerpt (500 KB)

I'll leave this file up for at least a few days in case others here are interested.


We're going around and around again Richard. I already agreed that using EQ is okay at low frequencies. It's not as good as having enough bass traps, but it's an acceptable bandaid.


Again, this is their problem. If someone prefers to spend $5k on cryo'd RCA cables (sorry, interconnects) rather than good acoustics, I am powerless to stop them.


You really need to visit me. I just added new killer bass traps in my living room - a new product my company will announce soon. These traps have more than 8 sabins of absorption at 40 Hz, which based on their front surface area is equal to an Absorption Coefficient of 0.71. Amazingly, the traps are all but invisible when placed in corners, so they have very high WAF too. My point isn't to brag about a new product, but to reiterate once again that bass traps spank EQ every day of the week.


LOL, I don't think we really disagree on all that much.

--Ethan

YOU WROTE:
"Amazingly, the (new) traps are all but invisible when placed in corners, so they have very high WAF too. My point isn't to brag about a new product, but to reiterate once again that bass traps spank EQ every day of the week."

RG:
Leave it to a true entrepreneur to get in a plug for his products at every opportunity ("Now you take my bass traps ... PLEASE!") and imply his alleged new product looks better than the only alternative I know of (a floor to ceiling stack of pink fiberglass insulation rolls in all four corners of the room)?

YOU WROTE:
LOL, I don't think we really disagree on all that much.

RG:
This subject is very important for better reproduction of sound in our relatively small home listening rooms, but would not be interesting without a big disagreement over something, even if the something is not much. And as any REAL audiophile knows, all audio problems can be solved by changing wires, so no one really neeeds needs bass traps and parametric bass EQ?

Further information in this report:
http://www.infinitysystems.com/home/technology/whitepapers/rabos.pdf

I really don't care about the rest of the room, and how it sounds there. All I care is my (virtual) armchair where I sit in front of my system, and the sound I am getting sitting there. I will not move it, therefore measurements should be made in the position of my ears in that chair.
i see some chaps are into serious talk, and all I wanted the procedure

Hi Ethan,

Might I inquire what speakers? Thanks.
Interesting thread btw. I would venture to guess most here listen primarily to loudspeakers, not headphones?
Lot's of aspirin solutions for the pain, without anyone addressing the cancer itself.

cheers,

AJ

My living room system is 5.1 surround with Mackie 624s, plus a killer SVS subwoofer with twin 12s - it's the size of a small refrigerator!

My home studio has a pair of old-school type JBL 4430s. The big ones with the 15-inch woofer and bi-radial horn. They're bi-amp powered by a pair of Crown PowerBase amplifiers with just over 1 KW.

--Ethan

Of course!


No kidding.


They don't show what happens to the ringing two inches away. They never do.

Versus my EQ Versus Bass Traps article which is very thorough.

--Ethan

http://en.wikipedia.org/wiki/Digital_room_correction

For an more controlled experience, and less hassle, you might want to consider a nice set of headphones.

Ok, I can see now why you would have to resort to the myriad of acoustic band aids around the room. Those type of acoustic sources make them a requirement.

cheers,

AJ

Acoustic band aids of some sort are almost always a requirement, if accurate reproduction is the goal.