hifi.slovanet.sk

[MaBat]

"Awkward room boundaries"?

There are two prime areas of "awkwardness". First, and by far the most awkward, are standing waves at low frequencies. Without any intervention, no two people in a room hear the same bass, and very likely nobody hears really good bass. With bass contributing about 30% of our total impression of sound quality, this is definitely a problem. I devote Chapter 13 to this topic, and there are some interesting solutions involving multiple subs. This is an area where you could exercise your mathematical skills, or use Sound Field Management, in which case a laptop does it for you - sadly it is proprietary, and only available now in JBL Synthesis products.

The second area of awkwardness is broadband first reflections from the sidewalls, floor and ceiling. The difficulty here is that we need information about the loudspeakers in order to anticipate the effects of the reflections. All reflected sounds originate in the far off-axis radiation from the loudspeaker. If the loudspeaker has something resembling constant, or gradually, smoothly-changing, directivity then the reflected sounds can have sound quality that is similar to the direct sound. This is good - when blind tested, listeners like it. The soundstage definitely benefits, the precedence effect works as it should (i.e. localizations are correct), and timbre is not corrupted. Reflected sound helps to fill the deep, octave wide, 2 kHz dip in the center phantom image spectrum heard by listeners in the sweet spot. This is a fundamental flaw in stereo. See Chapter 9.

However, and it is a big "however", many loudspeakers do not behave well off axis. Historically, it was really bad. So, people found that absorbing the reflections improved things. The pros went through a period of a "live end" and a "dead end " in which the loudspeakers were in the dead end, and all off axis sounds were absorbed. One of the most popular monitor loudspeakers of that era was the UREI 811 and its siblings, all of which had absolutely terrible off axis performance. A lot of bad sound was simply turned into heat in thick absorbers.

Calculus won't help you here, but good loudspeakers can do wonders. I spend several chapters of the book discussing the various influences of first reflections. Think about it, if a Stradivarius violin were played in your room, would you feel compelled to absorb most of its sound output? Instead of timbrally rich and room filling, it would sound thin and tiny. If a really good loudspeaker is playing a good recording of a good voice or musical instrument, why would you absorb most of its output?

The common failing of "room treatment" is that if absorption is attempted, only part of the sound is absorbed. One-inch fiberglass board absorbs sound only above about 1 kHz - all it does is attenuate the tweeter output, degrading what might have been a good loudspeaker. Chapter 21 discusses what to use.

Yes, rooms are awkward . . .

[MaBat]

The Soundstage measurements come from the facility I created around 1981 in my lab at the National Research Council in Ottawa Canada. Those are very good data. In fact I understand that the facility is still used by PSB Loudspeakers, the ones you own, and a few other manufacturers. Soundstage does not buy or publish the full set of NRCC measurements, but there are enough to identify good loudspeakers without ever listening to a note of music. They are the basis for the system that was further developed after I moved to Harman, and that has been incorporated into the ANSI-CEA 2034 recommendation for loudspeaker measurements, so it has gone well beyond a personal opinion at this point.

The John Atkinson measurements in Stereophile are basically correct and useful, but they suffer slightly from not being measured in an anechoic space, and there is no post processing to optimize the visual interpretations. That said, it is not difficult to recognize loudspeakers that have the potential of sounding good, or the reverse. Most interesting is that the conclusions drawn from inspecting the measurements do not always agree with the subjective reviews that have been done in uncontrolled, take-it-home-and-listen-to-it exercises. This is in distinct contrast to my experiences, and those of my colleagues over the decades, where in double-blind subjective evaluations the subjective opinions monotonously confirm the conclusions drawn from a visual inspection of competent and complete technical measurements.

So, your instincts are quite correct. All that is missing are accurate and comprehensive technical measurements on the loudspeakers you may be interested in. The "subjective preference" you allude to is something that has not been strongly revealed in double-blind listening - most people, most of the time, like and dislike the same loudspeakers. In fact it was this (then surprising) observation in my very first (blind) tests almost 50 years ago - described in Section 17.1, p. 339 in my book - that got my research started. If people agree on what is good, the next step is to find the right measurements to describe what they are liking. We have now done that.

The missing component in audio right now is consistency in the timbral quality of recordings. Recording facilities are not standardized, and not necessarily very good. So, the most "perfect" loudspeaker in the world cannot always sound good. In fact, we still need tone controls, especially a bass control, to compensate for easily audible spectral balance variations in recordings. Yet, many audiophiles seem to go through life thinking that recordings are flawless and that all problems are at the playback end. Wrong!

[MaBat]

My goal is to teach people to design good sounding loudspeakers, then selling good sound is not a problem. It is already beginning to happen. I have heard it happening, and have measured evidence of a gradual improvement in loudspeaker sound quality over the years. The world is a better sounding place than is was in decades past. In most cases it costs no more to build a good sounding speaker, it just requires an understanding of what the target is, and some competent engineering.

Today it should not be a challenge to build a truly excellent "high-end" loudspeaker. But several of them are disappointing because the builders don't understand, believe in or care about, the existing science.

I take great pride in having indirectly contributed to some really fine loudspeakers, some of them very affordable, from our own company and from several non Harman companies. The knowledge is there for all to benefit from.

[MaBat]

Floyd Toole. Celé vlákno zde.

[miero]

Diky za dobry prispevok do tejto rubriky. No nazov temy by mohol byt viac k teme, takto je to skor vyzva k bitke :-)

[opa]

Otázka je, zda na česko-slovenské fórum patří citace dlouhých odstavců v angličtině.
Můj názor je, že nikoliv.

[MaBat]

Tak je přeskoč

[Tico]

2 opa: Já to to naopak vítám a řek bych na fóra obecně nepatří jiné věci A možná už to někde zaznělo, ale vrtá mi hlavou, že se k problematice, která už pár měsíců čeří místní vody, nevyjadřuje třeba VB nebo check. Resp. jakési diplomatické vyjádření od VB na AKELu jsme slyšeli...

[kryton]

[MaBat]

Mluvil jsem o morálním úpadku hifi, potažmo high-endu. Technika samotná, pokud ji dělají lidi s upřímným zájmem o věc, se postupem času jistě zlepšuje, hifistům navzdory.

[kryton]

[MaBat]

Ano krytone, stagnace vývoje (zejména) v highendu, jak to napsal kdysi Holt.

Např. to, že dostatečné měřící vybavení si dnes může pořídit každý, včetně nastudování obrovského a dostupného množství know-how, a udělat klidně i doma na koleni špičkový bedny, nesrovnatelně lepší než by to bylo možné před 30 lety, je neoddiskutovatelné. I díky lidem, jako Toole.

"Today it should not be a challenge to build a truly excellent "high-end" loudspeaker. But several of them are disappointing because the builders don't understand, believe in or care about, the existing science.
...
The knowledge is there for all to benefit from."

A vůbec, jaký je smysl v předhazování si tady nějakých citací? Každý, kdo umí anglicky, si to může celé přečíst. Jsou tam daleko zajímavější věci.

[BV]

Tu je "sekta" pred chrámom

[Basstl]

[MaBat]

Pojďme teď udělat nějaký pořádný klasický čtyřpásmo, ať už jim s těma hornama zavřeme hubu. Už mě to taky furt nebaví, navíc Bunta dodnes nechápe, k čemu je dobrá vyrovnaná směrovost.

Kdo si chce postavit výborný klasický bedny za rozumný peníze?

[miero]

fifi by mohol byt dobry stavitel

[MaBat]

Byl to fór, už na to nemám a v dohledné době nebudu mít čas. Jen mě překvapilo, co se tu zase objevilo za obrázek, aniž by to souviselo s tím, co tady bylo odkazované nebo napsané. To už je skoro posedlost, nikoliv ale z mé ("naší") strany.

[miero]

[MaBat]

Tak aspoň něco zajímavého jsme se dozvěděli

[Zorg]

A jak pokračuješ s návrhem zahradní poslechovky? Bude to i kino nebo jenom stereo?

[MaBat]

Pokud, tak asi jen stereo, kino mě doma až tak nebaví a rád si zajdu opravdu do kina. Nejdřív ale přijde na řadu zahrada samotná, která už po tom zoufale volá - snad tam nenechám záda. Letos už určitě ne.

[Zorg]

Jó, můj tenisovej loket z krumpáče by ti moh vyprávět

[bedo]

[PMA]

[mrba]

[MaBat]

[MaBat]

[BV]

No dobre, tak niečo vážne (inak tá veľkosť zvukovodu evokuje spolu s názvom vlákna dojem "vchodu do katedrály").
Skúste niečo takéto s "top" produktom 1518. Na obrázku sú merané "mršby" ružovým šumom (prehrávaným z Foobaru) 1 kanálovou metódou , takže žiadna časová korelácia, je tam priamy aj odrazený zvuk, žiadne okno. Merané u mňa na mieste posluchu (cca 2,5 m od boxov), zvlášť L a R. V pásme do 300Hz malé korekcie cez plugin MathAudioRoom EQ. Peak na 100Hz - zabudol som otvorené jedny dvere...

[MaBat]

Taky bych jeden měl.

[PMA]