Is a FLAT response the IDEAL?

Sounds in nature are not a flat response, quite often, there are natural attenuators, accelerators and amplifiers, including horns (caves), wind and water, let alone reflections, absorption and diffraction.

Similarly the holy grail (one of them) of recreating outdoor, concert or live music, and so on, abound with these shifts in the environment or context where the experience happens and the recording takes place. Are we depending on the mic positioning, and mic performance, along with mixing equipment, format and so on, to enable recreation of the environment when moving to playback. How does a flat response curve help?

Of course, we have DSP. For Club, Hall, Rock, Indoor, Outdoor and may other shifts to music recordings. And mastering adds reverb as another way to create a 3D version of context/venue. These are averaging processes that apply universal shifts to shape a standard curve across the music stream continuously.

So why is it that we pursue flat response curves? Or DSP generated fixed curves? How does flat recreate that live ’being there’ experience.

When designing equipment including components, such as DACs, and speakers, most seek to judge against a flat frequency response.

Mind you, how on earth can we allow other than flat. Turntables as most here know, use the RIAA curve to fix the problems of hearing that itself is not flat. But even that is aimed to deliver a flat hearing response.

I don’t understand. If we are trying to model or capture the original event, how does flattening everything help? And, what are the alternatives? How do we achieve close to the venue or location, given so many unique variables, that our approximations just don’t seem close to the original. It’s no wonder... Have we selected flat because it is the best average we’ve got?

Do immersive audio methods of sound reproduction do it better? Some prefer pure stereo, some like DSP, some multi-channel and multi-speaker methods including ambiophonics.

Where does the ’flat curve’ fit into the equation here, vs say cross-over design or powered speakers or upgrades as a priority? Should we care about it?

Well that’s enough to launch this inquiry...


Peter Comeau, the entertaining English golden ear speaker designer for IAG (Wharfedale, Mission, etc) has done some good interviews on this subject. He suggests that his approach to being the final filter for his companies was liberated when he finally realized the flat performance was not his goal. He rejected over 170 trial and error crossover designs for the modern Mission 770 speakers before settling one. It’s good to be Peter I assume :)

OP has a fundamental misconception of what is meant by a flat response.  Early posters above tried to point out and correct this but to little avail and now everyone's gone off at tangents.  I'll try again.

A musical event is recorded.  The frequencies in the event are not flat - i.e. all the same sound intensity, or volume.  The objective in recording the event and replaying it on replay systems is to reproduce the event as it happened, i.e. with the loud bits loud and the soft bits soft.  The systems that are employed to do this should have a flat response, i.e. every frequency is recorded and replayed at the sound intensity/volume it had in the event.  That requires a recording and replay system that is 'flat', i.e. it treats every frequency input the same and does not make it louder or less loud that it was in the event.

Summing up.  The system is flat if it records and replays all frequencies as they occurred in the event, not louder or softer.  A flat system does not make the sound intensity of all elements of the event the same (as OP seems to apprehend, incorrectly).

Let me see, where did my flat response misunderstanding start... I'm a logical thinker, other than when I'm not, and can be both at times.

Flat response to me does not speak at all to it's meaning in use here in the audio world. 'Flat response' suggests an outcome that is flat. Clearly not the intention. I get that.

Let me repeat my problem. Flat response suggests an outcome that is flat. Just plain simple English. Maybe neutral not flat, or unchanged and not flat either. Neutral or unchanged far better convey the intention not to add anything or take anything away be it frequency, amplitude, place, timing and so on. Flat? No. Flat means flat. Flat what? At each and every moment in time, being measured, by a mic or ears or whatever, there is no additional (or loss of) information, change or disturbance, perturbation or otherwise in (tempted to say the force...) but will say the music/audio signal(s) being heard or recorded. Flat? No. Doesn't make any sense yet. To me.

Just accept it mate. Ok, throw away logic. Not yet.

Flat is a state not a transformation. In mathematics which I studied (among other things) a flat transformation (as a term or as a function) doesn't exist as far as I know. Other than its equivalent here - a zero transformation. Yet, here, the term flat transformation means no transformation (like in the maths sense), no changes are made to the original audio signals. You see I am trying to talk my way into understanding this term.

But the mind wants to think, flat means to flatten. And that drift, that urge is driving my misunderstanding. Response is an action (a verb), a flat response in this case is a zero action. This is an oxymoron. Ahhhh. And I think it's the juxtaposition of these two terms that is triggering my mind to think flatten - otherwise it doesn't make sense, logic. Zero response (I like zero transformation even better), easier to comprehend in this case, than flat response. Flat is a shape descriptive, flat surface, flat tyre, flat land, what do you imagine a flat response looks like? Visually? Duh?

Flat response means no response. Since when does flat mean none? Flat means flat. Flat response, is an oxymoron. You mean zero response, and here we go again, unchanged.  

Now I understand why I don't like the inadequacy of this phrase. Its an oxymoron. Unless someone can show me otherwise. Its an acculturation rather than a matter of logic, that has combined poor word choices into a phrase.

If a person gives a flat response, what would she/he be saying or doing? Nothing? This phrase doesn't make any sense. Just as it doesn't with mic's, equipment or anything else for that matter. No response, zero response, no transformation, no change (more simply), these are all easily understood alternatives, that don't risk sliding into oxymorons. 

Are you giving me a flat response here? You speak in oxymorons? ;-)


No,no,no.  You guys got it all wrong.  Regardless of any non-linearity of your hearing or from the environment, you want you playback hardware to have a flat frequency response.

I'll chime in here as well.  

I'm sure others have touched on this.

First off, Flat Response refers to how the piece of equipment (amp, pre-amp, etc.) is designed to reproduce signals.

in other words, if the amp is designed to amplify signals from 20 hz to 20 Khz for example, then you definitely want that amp to have a absolutely flat response between 20 hz and 20 khz.  a 20 hz signal should have a particular gain/response level from that amp.  a 1 khz signal should have the exact gain/response level from that amp.  A 20 khz signal should have the same gain/response level from that amp.

That is a flat response.  The amp, pre-amp, etc. isn't adding of subtracting (missing) any information to the signal.  it is not adding a signature of it's own.

However, many designers design to add additional bass or high frequency response to their equipment.  This most definitely not a flat response.

I want my equipment to reproduce the signal exactly as it came in, flat from 20 hz (or lower) to 20 khz (or higher).  Anything else is cheating and is adding a certain "sound" which is not accurate in the slightest.

Now, if the amp is designed in conjunction with a particular speaker for example, then there may be a need for some wave shaping circuitry to correct for the speaker's issues.  many speakers require this wave shaping correction.  However, it is typically in the crossover and not in the amp.  my point is certain equipment is designed together to correct for issues from other equipment from the same manufacturer.  This why as a system they sound great, but when used separately with other equipment, not so much.

thanks, enjoy