We know that Frequency Response isn't the end all be all... so what else is there?

[JRunior]

Hello all,
I'll be posting this on a few other Audio/DIY forums because I almost always come across the same argument that Frequency Response isn't the only factor when it comes to Speakers/Headphones but I don't have a good knowledge on what else matters.
For example, let's place three speakers in a Anechoic chamber (Removing room acoustics for sake of discussion) as well as assume that the three speakers chosen will all have a FR of 40hz to 20KHz +/-1.5 db. With these assumptions if I the listener heard all three speakers (Maybe one being the top of the line Genelec Studio monitor, another being lower end KRK speakers monitors and the last being the Orion (a well received DIY speakers) I think most would agree that each would sound different. Where I get confused is that 1.5db is very difficult for humans to distinguish between yet (and I may have this all wrong) the three systems would sound quite different even though the listner is hearing the same frequencies from each speaker... So from my perspective 8hz should sound the same no matter the source. This is where I'm looking for some education. I know there are numerous graphs posted alongside FR graphs and these are what I assume cause a sound difference even though the FR is for the most part identical.
I tried googling and reading through forums to find the answer yet I'm not finding out nearly as much as I'd hope. How does a speaker produce a flat FR yet contain distortion or other anomalies while maintaining a flat FR?
If any of you know some good material to read and can link it for further explanation that's just as good as a lengthy post.
Thanks for your time. I just want to be able to created a great listening environment and am interested in how to accomplish this without using FR as my only guideline.

Joel.

[SY]

Even in an anechoic chamber, polar pattern is critical. "Frequency response" is a simple thing for boxes of gain, but much less well-defined for transducers.

[wintermute]

if you want some reading material on this topic (and have the patience) you could check out this thread Measurements: When, What, How, Why

I thnk you will find it covers your question and also shows a pretty good cross section of beliefs/opinions.

As Sy mentions polar pattern is a key (though I'm unsure why it is critical even in an anechoic chamber, unless because there is no such thing as a perfect one?), think of it not so much as what the direct sound arriving at your ears sounds like (anechoic freq response) but how all the other reflected sounds arriving at your ears mix together when they arrive at your ears. Depending on the polar pattern of each speaker the reflections will be different, and since our brain interprets these reflected sounds to work out spacial information they will have an effect on the ultimate sound we perceive.

Tony.

[dantheman]

The more I've measured and listened to loudspeakers the more I'd say polar response has got to be the most important thing. The better controlled/more constant and less rippled the PR the better. If the tonal quality isn't right, there's just no real sense moving on. The next things I'd put on that list is efficiency(I'm a green kind of guy ha ha) and that is really b/c I want the maximum amount of output possible before distortion/compression becomes audible. Once you get there, you probably won't care about anything else. If you still do... more power to you.

Check these out: ****DanTheMan's blog****: Review of Polar graphs

care to guess which of these sound most correct?

Dan

[ra7]

I have a belief that maintaining the time information and reproducing it
correctly is more important than frequency response (and polar response).

Our brain can adapt quickly to variations in frequency response, but it has
a hard time reconciling distortion in time. I still haven't thought about this
clearly, but in my mind, this has got to be it.

Why else would full range drivers have a certain appeal that multi-way
speakers find hard to replicate, even though the full range drivers have
typically terrible on and off axis response?

Example: if two notes are reproduced at slightly different frequencies than
the orginal, but correctly spaced one after the other in time, they would
sound the same. But if they are spaced even slightly differently, they
would not sound the same at all.

[wakibaki]

Harmonic distortion, particularly second harmonic distortion at low frequencies and high volumes is a feature of many speakers. 10% THD is not uncommon, mostly second and some third.

Of course even 10% may be barely audible, it's popular to decry THD as a measure of quality, but it is measurable and it'd still be nice to eliminate it...

w

[charlesp210]

Loudspeakers project sound differently in every direction. They also continue to project sound after electrical stimulation has ceased.

The room also has directional and delay characteristics that interact with the loudspeakers.

Some loudspeakers are intended to be omnidirectional, even those speakers that do not intend omnidirectionality can be so in the bass frequencies. Some speakers emulate mostly a point source (such as dynamic systems with dome tweeter), others emulate line or planar sources.

I currently like adding omnidirectional ribbon supertweeter (crosses in at 16Khz) to my line-source-like Acoustat 1+1 electrostatics. What matters is the overall effect, and not whether one "model" (such as "the line source model") is realized perfectly.

[ra7]

Originally Posted by wakibaki

Harmonic distortion, particularly second harmonic distortion at low frequencies and high volumes is a feature of many speakers. 10% THD is not uncommon, mostly second and some third.

Of course even 10% may be barely audible, it's popular to decry THD as a measure of quality, but it is measurable and it'd still be nice to eliminate it...

w

Another reason to believe that the brain can tolerate large amounts of harmonics
not present in the original material, but even slight amounts of distortion in time makes
it sound unnatural. You immediately know that the sound is 'not real' or reproduced.

I believe we are chasing the wrong target when going after vanishingly low levels of
THD - we are not happy even after achieving it.

[dantheman]

and FRers never win any sort of listening contest.

Dan

[ra7]

True, but they're more musical than most loudspeakers out there.

I'm talking strictly about enjoyment, about connecting with music.
Most single driver designs achieve this quite easily, given all their
shortcomings. Now, if the criteria were soundstage depth, response
variations, and such other terms we use to describe how great our
systems are - and I like these things too - then obviously the full
range drivers will fall short.

All I'm saying is, the goodness behind full range drivers needs to be
explored more, rather than going on about polar response and such
other things. To me, they sound right despite all their shortcomings.

And what they got going for themselves is time coherence more
than anything else.