I'm not a serious audiophile, but appreciate good sound. I picked a pair of Dali Suite 2.8 (danish speaker manufacturer), because I found them to deliver a good deep, but not dominant bass and a very detailed treble. While comparing them to other speakers, I found brands like B&W sound "dull and lifeless" to me.

People talk about a "flat" frequency response, but how do this compare to the real world? Speakers are of course different and delivers different sound, and you pick a sound you like, but I guess that most speakers would have a different frequency response, and therefore ideally need to be EQ'ed to present a "flat sound" - But then I think that most speakers - cheap as expensive - would be able to reproduce the exact same sound once EQ has been applied?

Which advantages would a flat frequency response have i comparison? Would I generally just be able to reproduce the sound as it sounded during mastering?

I can't claim to know most of the factors involved but I have an idea about some and those say the answer is no. EQing the signal before sending it to the speakers isn't going to change many of the factors and in fact isn’t a good way to proceed in general. Fixing the room is a much better solution.

Speaker drivers need to move air to make sound. Some drivers flex more that others, so they produce more distortion. Drivers move back and forth along their axis of travel in relation to the signal applied to them. Some respond less linearly than others and thus produce more distortion. Some have more limited travel than others, thus less ability to respond well to louder peaks so they can only reproduce reasonably clean audio at a lower volume. The radiation pattern of sound waves varies for different drivers. Some will beam higher frequencies in a relatively narrow cone, some will provide wider, more even dispersion. The driver design and its relationship to its cabinet will produce more or less diffraction at the driver's outer edge, leading to more or less distortion. These are probably only a minor subset of real world considerations.

Regardless of what the advertising world and the HiFi magazines tend to say, most "hifi' speakers are designed to sound pleasant. In part this means they do not reproduce all frequencies evenly. Professional monitor speakers are designed to reproduce whatever is actually in the signal, whether it sounds good or bad. This later seems not to be so appealing to most music listeners, which is why the speakers sold to them are designed differently.

Is this the most valid explanation of why speakers sound different? In which way would a consumer-speaker be EQ'ed then?

I'm not into tuning my room for a better music experience. To my ears, I don't think it will make the great difference, and really I live in a very limited space

I think it would be fun to measure the frequency response of my current setup. Does anyone have experience with this, and which applications are useful for it? When I look for a microphone, which preferences should I look for?

Distortion of various varieties is much higher is speakers than in any other part of an audio system. This accounts for a good bit of the differences in the way music coming out of them sounds. Reducing that distortion significantly is an expensive proposition.

I haven't memorized the details, but I do recall that some midrange bands are de-emphasized in home speakers because that is where a lot of critical and revealing (maybe ugly) data comes through.

Measuring room characteristics (or speaker characteristics) requires a calibrated measurement microphone(s) in order to give any values or meaning to the data. There is software that can analyze rooms pretty well from dimensions and other data you enter at the keyboard. I think some of it may be freeware (probably not the best, but at least some kind of results are possible). Making measurements on the speakers themselves requires a special space that won't interfere with the measurements (in addition to the calibrated microphone).

There is a professional in this field that haunts this forum
http://www.audiomastersforum.net/
He is sometimes willing to answer questions and knows about various room analyzing software.

This is, as you probably guessed, a very complicated subject. The complexity comes, mainly, from the interaction of the speakers with the room. It would be much easier to design speakers to have a flat response in an anechoic chamber than in a real room.

I have designed an built several speakers (including a little input to a commerically available kit), and recently have been applying room correction by convolution with speakers that were designed to make that process work well.

Unless you are a speaker designer you'll want the in-room response; but quickly you'll realise that there is no such thing: the response at your left and right ears will be different above a few hundred Hz - which do you want to be "correct"?

It is worth thinking for a moment about how sound travels and reflects around the room. At low frequencies, up to say 300 Hz, room modes strongly dominate the response, and the main control over this is the position of speakers and listener, although adding lots of big furnishings etc. can damp them somewhat. From 300 Hz up the speakers playing stereo tend to produce interference patterns in the room. There are typically very strong spatial nulls, and strong ripples in the frequency domain. Floor, ceiling and wall reflections make this more complicated, but the basic pattern comes from having two speakers. Reflections are more and more easily damped at higher frequency. Moving up to a few kHz, the wavelengths and resulting patterns become smaller than a head, and the frequency response is then dominated by the speakers' response. Here the problem becomes one of measurement, as the brain is very good at sorting out the direct sound from the reflection, and combining left and right ear information. A single microphone does not do that!

Talking of which, a Behringer ECM8000 measurement mic is a good start, it needs phantom power though, so a proper mic preamp (I use the input on my Echo Gina 3G soundcard, for example). Measuring the frequency response can be done using e.g. Foobar 2000 to play white noise or tones, and recording with something like Audacity (which has a basic FFT analyser to show the response). Apart from satisfying curiosity, and possibly horrifying you, this is not all that useful, as there is no separation of direct and reflected sound.

A more useful measurement is to find the impulse response of the system. This is best measured by playing a chirp (sweeps over the audio range in a minute or so) recording the result and processing it. But here we are getting into a very big topic - look up "Digital room correction" (wikipedia has it, could not quickly find it on the wiki here).

So to get back to your original question: do speaker designers aim for different results? Yes, most aim for a flat on-axis response measured with a mic 50 cm away or so (to be able to say something like: response from LL Hz to HH Hz +/- ZZ dB). So why don't all speakers with a flat on axis response sound the same? The off-axis response and total radiated power as a function of frequency are not determined by the on-axis response. Take extreme examples of a very small satellite speaker - this will have a uniform radiation pattern at low frequency, but moving up to higher frequency the sound will drop off except straight ahead; or an electrostatic or other diplole, where there is nothing radiated left and right, and the same to front and back. Those will give very different in-room responses.

I think I've said enough to hint at the main issues: from my perspective integrating speakers and rooms is *the* challenge for hi-fi: in my experience it utterly dominates all the common concerns people have about other components in the system.

Distortion has already been discussed: it is also a factor in speaker sound.

Ken

Agree.

I once positioned & equalized a room with great difficulty... only to have the owner of the house rearrange the furnitures 'extensively' to make the room better-looking with the speaker placements...

I hate feng shui.

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