Question about equlizing with a BFD (1 Viewer)

[Pete Mazz]

That’s a pretty big assumption. You can pretty well rest assured that a recording of a live event has been processed and equalized by the time gets to the store shelves.

And then you want to add more EQ on your end? There's no telling where you'll wind up.

If music sounds natural straight out of the instrument, I don't see why a recording of it would sound better with an unnatural amount of EQ added to it.

We'll have to agree to disagree on this one Wayne.

Pete

 

[RichardHOS]

There's still that lingering question of why, if a mix sounded good to the mastering engineer who is presumably using a very flat EQ'd monitoring system, why wouldn't it also sound good to us at home when using a flat EQ'd playback system?

I think the options still remain either (1) difference in room acoustics or (2) concious decision by mastering houses for whatever reason to reduce the level of bass in most albums.

I'm just wondering which of those two it is, and some details of the explanation.

 

[Wayne A. Pflughaupt]

Peter,

As I noted, generally it is only the sub being equalized – not the mains. Most audio buffs do not feel that equalizing a sub degrades anything. Of course, anyone who prefers ragged, inaccurate in-room response at low frequencies is certainly free to have it.

Richard,

The answer is more or less #1. I say “more or less” because it’s not so much acoustics (which has to do with reflections, reverberation, dampening, dispersion of soundwaves, etc.) as it is the size of the listening room. As to why the size of the room affects bass the way it does – you’ll have to find that out from someone with a degree in this stuff.

Regards,
Wayne A. Pflughaupt

 

[Pete Mazz]

Richard,
I wonder if your perception of lack of bass has to do with the fact that a lot of CDs are compressed quite a bit to sound "louder". This certainly affects dynamic range, which may affect bass transients on the recording.

Here's what I'm talking about:



A recent release that's been compressed.

Vs.



An older recording done properly.


Have you noticed that recent CDs, for the most part, sound louder overall than an older recording? The record industry has decided to abandon reason and good engineering practices in favor of being able to say "Mine sounds louder than yours!"

So they use compressors and limiters to boost the overall levels and then clip the tops off of the transients (can you say square waves?).

Drives me crazy!!!

Pete

 

[RichardHOS]

I still have a problem with that Wayne. Most home theaters are as large as, if not larger than most mixing rooms and mastering studios. According to your size/amount of perceived bass relationship, in a smaller mastering environment the engineer would tend to EQ the recording for more bass to get a flat perceived response.

Play that back in our somewhat larger theater rooms where we need less bass to sound flat, and suddenly the recording is bass heavy. That's going the opposite direction from a house curve.

The devil is in the details. It isn't enough to just say "probably the room." I'm curious as to just what the complete explanation is. Is it reverberation related? Resonance related? SPL related? I understand that you may not be able to answer this... I was just hoping someone could.

Perhaps studio's just monitor the recording in the final stages at very high volume levels, while we play it back at significantly lower levels, and the F-M curves are all that's needed to understand why we need a house curve to make up the difference.

 

[Wayne A. Pflughaupt]

According to your size/amount of perceived bass relationship, in a smaller mastering environment the engineer would tend to EQ the recording for more bass to get a flat perceived response.

Play that back in our somewhat larger theater rooms where we need less bass to sound flat, and suddenly the recording is bass heavy. That's going the opposite direction from a house curve.

Nope. You have it backwards, Richard. The smaller room will naturally boost the bass (remember the “free” bass you get from cabin gain), so the inclination for an engineer will be to reduce the bass level.

Also, I think we need to differentiate mastering for music vs. theater. I’ve been primarily talking “music,” because the goal there is (hopefully!) balanced response, and you seem to be more concerned with mastering for theater. For movies, they intentionally exaggerate bass for the purpose of impact.

Also – I don’t know about movie mastering, but often the engineer for a music project will test his work on different types of systems, from boom boxes to car stereos to home systems, to help insure the CD will sound as good as possible to the end user. An engineer who does this effectively takes his local room response out of the picture.

Regards,
Wayne A. Pflughaupt

 

[RichardHOS]

Also, I think we need to differentiate mastering for music vs. theater. I’ve been primarily talking “music,” because the goal there is (hopefully!) balanced response, and you seem to be more concerned with mastering for theater. For movies, they intentionally exaggerate bass for the purpose of impact.

I've been primarily talking about music as well. I use the term theater simply because I no longer see the need to have a dedicated two channel listening environment.

 

[Jacques C]

If I may butt in here with a question I have seen the answer to but cannot find:

What does a "house curve" look like?

My new media room is just about ready and I would like to try it out and see how a house curve sounds (I do have a BFD).

Thanks!

 

[TimForman]

This might help.

 

[Wayne A. Pflughaupt]

Jaques,

A house curve is a gradual rise (or slope) in response at the lowest frequencies...

Using flat response as a reference point (i.e., where all frequencies reference at 0dB):

The response with a house curve would measure + 7dB at 30Hz and slope gradually downward from there and read –4dB at 10,000Hz. NOTE: This is only an example – larger rooms need/have a gentler slope than smaller rooms.

The links I provided in my first post will give more information.

Regards,
Wayne A. Pflughaupt

 

[Wayne A. Pflughaupt]

Richard,

No contradiction there. Notice the quote started with “however” – which means the information above it was relevant, especially the part about cabin gain. That’s what was being overlooked when you said:

It would also suggest that the larger the room you have, the closer your system could be to measuring flat and still sound flat.

Trust me, measured-flat response is no Holy Grail. Based on my admittedly limited experience, your room will have to be the size of a large, cavernous warehouse or a medium-sized concert venue (that seats a few thousand) before you will be able to achieve measured flat response. But then you will have a host of other problems to deal with – multiple reflections, long delay and reverberation times, etc. Not to mention extension (for all practical purposes) limited to about 40Hz.

Regards,
Wayne A. Pflughaupt

 

[Jacques C]

I missed the links earlier.

Tim and Wayne, thanks for the pointers.

Take care.

 

[Stephen Dodds]

I'm not an engineer, but I spend a fair amount of time in recording studios. Most of the ones I've been judge bass levels by ear. They check the mix using full range monitors, and then again using small (crappy) monitors to check if the mix is radio friendly.

Then compress the hell out of it.

They also tend to monitor in the nearfield.

Regarding the white noise/pink noise, it depends what you are calibrating with. If you use an MLS analyser (ETF)you would use white noise, if you use an RTA (TrueRTA) you would use pink noise.

I have both and get essentially the same results.


Steve

 

[RichardHOS]

I suppose I'll just have to live with the less-than-satisfying explanations given thus far.

Wayne, while the cabin gain might want to make the engineer master the recording with too little bass, that is competing with the reverb/size effect, which would tend to make him do the opposite. I don't see how you could draw the conclusion that the cabin gain necessarily gives him all the extra bass he would perceptually want in a particular room.

I wish there were references to rigorous work done along these lines. I haven't heard anything in this thread that goes very far in explaining why if my system measures flat, and a studio's monitoring system measures flat, and the room sizes aren't drastically different, why I wouldn't perceive the same amount of bass that the person making the final EQ adjustments did.

Perhaps we just like more bass than studio engineers, and that's all the explanation required.

 

[Wayne A. Pflughaupt]

I don't see how you could draw the conclusion that the cabin gain necessarily gives him all the extra bass he would perceptually want in a particular room.

It’s from personal experience, Richard.

Perhaps a couple of real-life examples will help.

A number of years ago, back when I was only vaguely aware of any of this, I had a pair of speakers with outstanding and extended bass response. After I had them a couple of years we moved from one location to a second. Both had approximately the sized same living room area, and I noticed no appreciable change in the way the speakers sounded.

But then we moved to a bigger place with a larger living area. The first thing I noticed when I fired up the stereo (I did say this was a number of years ago, didn’t I? ) was, “Holy cow, where’s the bass?" Suddenly my pride and joy speakers with their outstanding bass sounded very thin and “anemic,” sonically speaking.

A couple of years later (still living in the same place) I found myself in need of some new speakers, and I caught an ad in the local paper for some speakers I remembered had gotten a good review in Stereo Review some years earlier. I went out to the owner’s place to hear them; he lived in a rather small townhouse with a living room much smaller than mine. On auditioning the speakers, my reaction was that they sounded rather bass heavy. But I remembered what had happened with my other speakers, and figured, “Y’know, I’ll bet these will sound just about right at my place.” Sure enough, when I got them home and hooked them up, the exaggerated bass was gone. They were perfect.

Now, if I had been living in the little townhouse the former owner did, I would have been inclined to use the tone controls to roll off some of the bass. Just like the engineer in the example you gave above.

I could cite other real-life examples, but it would only be redundant. Suffice it to say, I’ve seen it time and time again: Smaller spaces reinforce a speaker’s bass response. I don’t know why that is, and I haven’t made attempts here to explain why - only that it does. Just like I don’t know how or why gravity works, but I’m confident in the fact that it does.

Perhaps, Richard, if you started a new thread in this section, “How does cabin gain work?” it would attract the attention of someone smarter than I who could give you the answers you’re looking for.

Regards,
Wayne A. Pflughaupt

 

[Pete Mazz]

I haven't heard anything in this thread that goes very far in explaining why if my system measures flat, and a studio's monitoring system measures flat, and the room sizes aren't drastically different, why I wouldn't perceive the same amount of bass that the person making the final EQ adjustments did.

Absorption. Most living spaces have nice overstuffed furniture, nice thick carpets and the like. Although studios have foamed walls for early reflections, these don't absorb much low bass.

Cabin gain is created by reflections. Axial modes, the strongest, are created from 2 parallel surfaces. Tangential from 4 and oblique, the weakest, by all 6. Standing waves are based on the 1/2 wavelength distances in a room. The smaller the room, the higher in freq the standing waves start. That's why a car's cabin gain begins so high. That's why a rooms dimension should never be a cube. All the standing waves would be at the same freq.

Grab a copy of The Master Handbook of Acoustics.

Pete

 

[Greg Yeatts]

A perfect example of cabin gain is the sub and room combo that I am attempting to equalize (and started this thread). My enclosure is tuned to about 19.7 hertz. I get flat bass response in my room to 14 hertz. On a model, my bass should be down 5 or 6 db at this point. So, I have some room gain here.

 

[Richard Greene]

Cabin Gain is an approximately 12dB/octave bass ramp up starting below the lowest frequency room mode
whose center frequency in Hz. for a rectangular room
would be approximately:
565/room length (largest room dimension) in feet.

Cabin Gain will be less than 12db/octave if there are open windows and doorways. A sealed enclosure 0.707 Qtc subwoofer with its 12dB/octave bass roll-off can combine with a small room's natural 12dB/octave Cabin Gain to create a very low frequency f3.

In large rooms that have very little Cabin Gain at 20Hz., a sealed enclosure subwoofer will tend to sound weak at 20Hz. compared with a ported subwoofer.

In small rooms a ported subwoofer combined with Cabin Gain will tend to overpressurize the room at 20Hz.

 

[Robert AG]

There is one simple reason that at least in film mixes the bass is "tamer" than what is the norm in home environments: Taste.

I can assure you that if the film mixers cranked the bass to levels heard in the majority of home theaters, the mix would sound muddy, bloated and exaggerated in the low end. There are no real restrictions on the levels of bass in a film soundtrack other that what is in good taste. The dialogue would be difficult to hear, and the spectral balance would just sound "wrong".

Film mixing engineers learn to have a relatively neutral ear when mixing, and they are not free (again by good judgement or taste) to exaggerate any one freuqncy band just because they may have a personal preference. If I mixed music with my preference for heavy bass, the resulting mixes would simply sound muddy and probably receive negative comments on this muddiness.

One instance where I have been able to record to my personal preference for bass resulted in the recording reviewed by Edward JM in this thread:

http://www.hometheaterforum.com/htfo...=&pagenumber=9

This was a straight to two track digital recording with no multi-track mixing, and in the mastering phase, no adjustments were made to the low frequency balance - just straight through. Is this recording commercially viable? No frigg'in way!!! It would shread consumer's subwoofers, which is why you never hear recrodings with this much low frequency extension. Is it fun? You bet!! But if I turned in a recording like this for commercial release, I'd get slapped up the side of the head and invited to exit the building.