|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
47.188.98.98
In Reply to: RE: Excellent point posted by Duke on October 27, 2016 at 11:13:05
Golly, to read what you guys write, a person would think that Earl Geddes and Floyd Toole were the only two guys who ever researched this stuff. :)
I've been reading research papers on psychoacoustics since the mid 1970s, and working with audio systems since before that, before I quit college as a music major in 1975 (I veered off into audio and acoustics instead of music). Anyway, this whole "2 ms, 6 ms, 10 ms, 20 ms" stuff is making me gag.
YES!, there IS a threshold between where a reflection 1) Changes the character of a sound, 2) Changes the apparent location of a sound, 3) Interferes with the 'definition' of the sound; and, it varies with the type of sound, and these effects vary with both sound level and frequency.
Duke, I'm not raggin' on you, but in the "audiophile" world, many people are SO clueless about acoustics and psychoacoustics. To me, your comments are well-taken and useful. The thing is, the audience for your comments needs more depth in order to understand the topic, and you're over-simplifying it. Generally speaking, I'd say you're on the right track. (See my post from a couple years ago. LOL)
One of the bottom lines is that "audiophiles" should get at least a basic understanding of acoustics and psychoacoustics.
:)
Follow Ups:
From my reading on acoustics I thought Bell Labs identified the importance of at least a minimal separation between direct sound and reflected sounds for reason of clarity -- minimizing sonic smearing. Unfortunately I don't have a specific reference for that.
"The piano ain't got no wrong notes." Thelonious Monk
Auditory thresholds are usually somewhat fuzzy in the time domain, and reflection detection thresholds do indeed vary with level and frequency and direction, and the subjective effect of said reflections likewise varies. But if the question is a practical one like "how far do my Maggies need to be out from the wall for the magic to happen?", then that answer is going to translate into a path-length-induced time delay that is the same at all frequencies. What I'm doing isn't exactly the same as the Maggie situation, but it's pretty close. So that's why I'm not talking about the effects of different delays at different frequencies.
Just for the record, in addition to Toole and Geddes and Greisinger, my sources include "Spatial Hearing" by Jens Blauert and an assortment of AES articles by various authors. But Toole and Geddes are the ones who the most into practical applications relevant to loudspeaker systems in home listening rooms.
Now if the question is "what matters most - getting the reflections to arrive from the ideal direction, or getting a bit more time delay?", the answer cannot be found in the published literature. It has to be determined experimentally. James Romeyn's findings on this topic surprised me, as based on my understanding of Toole I'd have told him not to waste his time trying the upfiring geometry, but in practice it outperformed other geometries that resulted in a more ideal reflection direction but less time delay.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Psychoacoustics is a fascinating field. Heck, just for starters, it's kind of amazing that we can fool ourselves into thinking there's a band/orchestra spread across the living room wall - with only two sources!
Anyway, I'm in complete agreement that the up-firing driver is the way to go as a means of improving the ambient sound field. The one caution is that it not be too directional. Even though we're not very good at detecting the vertical location of a source, if the up-firing driver is too directional, it could actually be a contributor to a less-than-desirable ambient field.
One other thing... If you could build in a passive FR contour control, with maybe 4 - 6 setting choices, and a level control, that would be the tits.
:)
I agree that we would not want too strong and distinct ("specular") a reflection from the upfiring array, but in practice we're usually getting reflections off of both nearby walls as well as the ceiling, and so it hasn't been an issue with the radiation patterns I've been using. And the ear's reduced localization ability in the vertical plane probably helps too. I would guess that there is a tradeoff between narrow pattern to minimize any early-arrival energy vs wider pattern to give us a more diffuse "main" reflection, but in practice the physical size required to get very tight directional control down usefully far into the midrange is probably prohibitively large.All of my speakers (LCS and rear-firing arrays included) have an external resistor-in-a-cup that functions as a "tilt" control for the high frequency driver. I say "tilt" because changing the resistor value has more effect at 10 kHz than at 2 kHz, which I think is more useful than a "shelving" type control. I normally provide resistors for three different settings, but obviously someone who finds that an "in between" setting would be optimal can tailor the resistor value to that.
My more recent rear-firing or LCS arrays incorporate a level control with about 6 dB of range, and I could incorporate such into any future builds.
In most cases my LCS and rear-firing arrays have separate inputs, which means you can reverse their polarity. This can be useful for smoothing out the in-room response in the upper bass region. Actually having two bass/midbass sources per speaker that are a different distance from all three room boundaries helps in that respect all by itself, regardless of which polarity you use.
I have designed (and shown) a set of add-on LCS modules that could be added in parallel to many existing speaker systems without dropping the impedance too much, but I have not gone into production with it yet. Further testing is needed before I can say with confidence what range of circumstances it would be beneficial in.
Speaking of psychoacoustics, there is one other trick I do which I have not gone public with, something I learned from Earl Geddes and which is confirmed by a close reading of other sources. Psychoacoustics is indeed the neatest thing, it's like there are these little counter-intuitive backdoor entrances to the halls of sonic bliss.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Edits: 10/30/16 10/30/16
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: