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Old 7th July 2013, 09:46 AM   #1
Kev06 is offline Kev06  England
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Default flat vs equal loudness vs room gain

Can I just check that I understand some of the key points relating to what frequency response I should be aiming for in a speaker build?

Music will be recorded and produced on systems which have a fairly flat frequency response (within reason). Therefore to reproduce it like the original I will also want a flat response at the listening position. The equal loudness curves (in an absolute sense) are not something that I should be looking to reproduce for normal listening, because I would not have heard the original music at equal loudness either - it will be subject to my imperfect human hearing response whether live or recorded.

However, the equal loudness levels change with volume. So if my intended playback levels deviate from the original music's volume, then I may need to adjust the relative loudness of low and high frequencies to bring them back into step with the rest of the frequency range 'in my perception' at the playback volume. This adjustment would be indicated by the 'difference' between the equal loudness curves at original and playback volumes.

Room gain comes into play at low frequencies, so a flat response (even if already compensated for loudness) from the speakers may not be desirable. To be flat at my listening position the speakers should roll off gently to oppose room gain - in a typical room say 'very' roughly around 2db/octave below 100-200hz.

Have I understood the basics of these things?

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Old 7th July 2013, 02:14 PM   #2
Pano is offline Pano  United States
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I'd say yes, with some caveats depending on taste. I don't like a flat response at the listening position, I prefer the old B&K downward curve. Flat up to about 400Hz, then gently sloping down to -6dB at 20KHz.

You do need to take room gain into account, usually it's your friend and helps the bass where the speaker is sagging.

Equal loudness is what tone controls or the "Loudness" button are for. Trouble is, there is no reference level for music mastering. You don't know how loud it was in the mastering suite when the engineer found the tonal balance he liked. Tho generally that going to be in the low 80s SPL. Below that you might like some equal loudness correction.

That's my 2 cents. I'm sure you'll get plenty of other opinions.
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Old 7th July 2013, 02:49 PM   #3
DUG is offline DUG  Canada
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Pano: I agree that opinion is the correct word.

One can never debate: "It sounds good to me."

I find some songs need more bass, some less.

I am not going to re-equalize my entire library.

If I walk to another room the sound changes.

Sometimes you have to put up with some of your music content not sounding perfect.

Design for flat and adjust for your taste.

My $0.02

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Old 7th July 2013, 04:48 PM   #4
Kev06 is offline Kev06  England
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Thanks chaps. Yeah, I guess there would always be an element of preference with these things, but as long as I have the basics then it at least gives me a sensible starting point.

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Old 7th July 2013, 04:49 PM   #5
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Several studio active monitors have built-in equalization with a calibrated microphone whereby one merely locates said microphone at the desired listening location & equalizes by the feedback of the microphone, setting the response "flat" right away.
Now, the quality of the sound will be up to the sound engineer at that moment. Any tweaking or un-acceptable modifications of frequency bands to your DISLIKE will not be your fault.
Now, if we really want to extend the technology....why shouldn't there be a wearable microphone where we walk around the room & the system actively & immediately re-equalizes for our location????
Building a loudspeaker system, I believe, should aim for a flat response with modifications for any one listening room.

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Old 7th July 2013, 06:39 PM   #6
jReave is offline jReave  Canada
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I'll just add another 2 cents.

Think of it this way. Each individual instrument (whether acoustic or electrical) is already designed or EQ'd so that its FR sounds correct to our perceptual systems. (For eg, what do you think all those differently shaped and sized boxes on acoustic stringed instruments are for? Besides adding volume and richness, they're boosting the bass). Likewise, all the instruments and voices get mixed together (ie. their real SPL levels get adjusted) so that again they sound correct to our human measuring system. Thus correct reproduction is thru a system that makes no further changes to what is already considered by our hearing to be correctly equally loud across the FR - in other words, you want a flat set of speakers.

However, consider what happens when the mixing is also done in a room. The mixing engineer adjusts the bass so that it again sounds right to his or her ears, room gain included. (Headphones obviously is the wrench in this process.) So in other words, room gain and room acoustics in general are also already included in the recording process. They also occur at both ends of the chain when you are listening in a room.

Still, your room is unlikely to be an exact match to the studio's, nor do you know if the LF roll-off of the studio monitors was -12dB or -24dB or (as has been mentioned) at what volume it was mixed at so the key I think is that you still might want to make EQ and room treatment adjustments to suit your own preferences.
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Old 7th July 2013, 09:21 PM   #7
Kev06 is offline Kev06  England
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Interesting stuff - thanks!

Some of this seems beyond the scope of any single system response. With these 'out of my hands' deviations, the best approach would presumably be to design speakers (etc) that assume the original recording is faithful in an open field, and deliver that as close as possible 'in my room, at my listening position, at my volume'.

Then if its been recorded or mixed in a small room, or had the sound engineer's/producer's own eq stamped on it, I'll manually use a graphic or parametric equaliser to adjust things to my own taste. I can't really see how I could reproduce an original (if indeed one ever existed in the real/acoustic/audible world) which is biased in some way without information I won't have, so my preference will have to rule.

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Old 7th July 2013, 09:40 PM   #8
markusA is offline markusA  Sweden
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I read something pretty smart once, fix acoustical problems with acoustic solutions.
You can't EQ radiation pattern/directivity but you can EQ FR and phase to a certain degree.
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Old 7th July 2013, 10:54 PM   #9
ra7 is offline ra7  United States
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I'd second Pano's suggestion of the B&K curve at the listening position. But to get that, assuming normal furnishings, it mostly requires a flat, anechoic response. At least that's what I've found. When you get it flat anechoic, it naturally results in the B&K response at the listening position. Flat above 500 or 600 Hz is easy to get. Below that, you will have to juggle the room response with the speaker response, and understand how to measure what you are hearing.

Let me add by saying that flat anechoic is not as important as a smooth response. Ups and downs in the response is something the ear really does not like.

You will get a 100 different opinions here. The most important thing is to learn to relate what you are hearing to measurements. If you can get good measurements, the result will more than likely be to your liking.

Last edited by ra7; 7th July 2013 at 10:58 PM.
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Old 7th July 2013, 11:26 PM   #10
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There are some "hi fi" manufacturers that insist that "you shalt not have tone controls" on your pre-amp. It makes them more "pure" in their view. How does this position stand vs. listening volume & room tonal response?
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