Mixing/Mastering for “Flat” Loudspeakers: What is really “flat” anyway?

Bob Katz Leave a Comment

Dear Bob,

I write because I noticed you apply a slightly tilted room curve to your mixing room. But why not make a flat response as reference and then mix your recordings from that? To a “straw man” like my that would seem more logical because a tilted curve will introduce a spectrum bias which I as a consumer would need to implement in my system as well. Whereas if a mix made from a flat response means that if my speakers (whether equalized or not) are pretty much flat I will get the approximately same sound impression as in your studio. Of course, a complete replica is not likely unless I also aim for the same RT level as in your studio.

Anyway, it was just something that got me curious and finally I just had to ask for the reason for a tilted curve in a mixing studio, which for the uneducated man (like myself) seems odd.
I certinaly mean no disrespect, since your knowledge in this field is manifold greater than mine. So it with the utmost respect that I ask :-).

Best regards,

Mikkel G. Hangaard

Dear Mikkel:

Thanks for your letter.

What you have brought up is the classic “chicken and the egg” situation. It is true that our recordings have to complement our reproducers. if we equalize our reproduction system to flat (however that is measured), it would cause us to produce mixes and recordings which would be duller sounding than our current mixes! But historically, that has not been the case. We have a large recorded legacy of recordings that sound perfectly good on playback systems that measure some high frequency rolloff. All the major accepted reproduction systems since the beginning of time measure rolled off at the high end to some degree. So basically you are asking us to try to produce new recordings that would not be compatible
with the older reproduction systems.

It’s academic: If today, suddenly, all playback systems were made flat, then all or most recordings which already have been made would sound too bright. It’s a long, historical precedent and consistency is more important than absolute conformance with “flat”.

Lastly, there is a whole question of how “flat” is to be determined. Loudspeakers which have a wide, flat dispersion characteristic sound very different than loudspeakers which are flat on axis but rolled off off axis. How do you determine what is flat in that case? Then getting into questions of reflections from the side walls in the room and how they are treated. Lastly, the question of the measurement method and the measurement window, should it be anechoic or should it include some reflections in the room?  There are so many different ways of determining the window that unless you know exactly how a measurement was taken, you cannot effectively judge a published loudspeaker measurement.

All these variables produce varied amounts of “measured” rolloff. In other words, even the definition of how to define “flat” is put into question. So even if we were starting from scratch with new recordings and new reproducers, there would still be a fundamental disagreement as to how to measure and determine what “flat” really means and we would still get nowhere!

So in the end, the egg came first, and the chicken followed, and we just have to keep on keeping on!
Hope this helps,


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