Yes, I just wish there was some way to put my finger on it. What I'd like to see, for the benefit of those building a high reflection environment, is a system of classification.. a distribution plot of earlier reflections by time, quantity, level and angle.
This can be compared to theoretical maximums for rooms (or partial rooms) for the greatest usage and at the same time, diversity.
The next step could be to use selective absorption and subjective listening groups to chart preferences.
Then, create software to make such plots from directivity data, room placement data and possible use of absorption.
This can be compared to theoretical maximums for rooms (or partial rooms) for the greatest usage and at the same time, diversity.
The next step could be to use selective absorption and subjective listening groups to chart preferences.
Then, create software to make such plots from directivity data, room placement data and possible use of absorption.
@OP
Getting bass right is important since it affects the perception of high frequencies too (a pretty weird phenomenon of providing sort of a baseline for human hearing). Also if you look up the equal loudness curves, you can see that it takes a lot of sound pressure level for bass to become audible, but once it does the curves are crowding i.e. the hearing is more sensitive to small changes in SPL at low frequencies.
The main factor is the room! and the bass unit(s) placement!! One can argue for dipole bass exciting the room differently but one can get a good result with cheaper sealed or ported bass units if they can afford different placement and if they can put in time to optimize the response. Using an active XOver helps delay the units if they get closer to the listener.
in re: to the dipole bass here is one resource:
Prototyping a Dipole Bass System
and I can look up the white paper on multiple subs from Harman site (the approach which E.Geddes also advocates).
So do not sweat the big $$s for a dipole system which doubles up on the expensive long stroke Seas units; just think where you think you could put the sub(s) and if your room has similar dimensions and where you sit in terms of wavelengths for the standing waves mainly front-to-back and side-to-side. there are room acoustic calculators online to give you an idea of the wavelengths which may present the most challenge in your room.
Getting bass right is important since it affects the perception of high frequencies too (a pretty weird phenomenon of providing sort of a baseline for human hearing). Also if you look up the equal loudness curves, you can see that it takes a lot of sound pressure level for bass to become audible, but once it does the curves are crowding i.e. the hearing is more sensitive to small changes in SPL at low frequencies.
The main factor is the room! and the bass unit(s) placement!! One can argue for dipole bass exciting the room differently but one can get a good result with cheaper sealed or ported bass units if they can afford different placement and if they can put in time to optimize the response. Using an active XOver helps delay the units if they get closer to the listener.
in re: to the dipole bass here is one resource:
Prototyping a Dipole Bass System
and I can look up the white paper on multiple subs from Harman site (the approach which E.Geddes also advocates).
So do not sweat the big $$s for a dipole system which doubles up on the expensive long stroke Seas units; just think where you think you could put the sub(s) and if your room has similar dimensions and where you sit in terms of wavelengths for the standing waves mainly front-to-back and side-to-side. there are room acoustic calculators online to give you an idea of the wavelengths which may present the most challenge in your room.
Last edited:
There are two separate and independent sources for creating ambience in what you hear in your listening room at home.
The first is the sound captured by microphones positioned at various locations in the venue where the performance is recorded. These sounds are then further used and manipulated in the mixing studio. They then are part of the recording that you play back. These are fixed ambience effects. You can’t change them.
The second ambience effect is related to your speakers and room. This effect you have significant control over. Open baffle speakers, in particular, create different sound fields than boxes in the same room.
OBs reflect sound off of the wall behind them which is delayed from the sound that you hear directly from the front of the speakers. As long as that delay is at least 6 ms the sound has an ambience that is similar to being in a venue much larger than your room. You can call it spaciousness, openness, ambience, whatever you like. But it is very different from what you hear with box speakers.
Some people believe that the delay really needs to closer to 10 ms for the best effect. Opinions vary. That’s why the minimum recommended distance from the front wall for OB speakers is usually 3 feet, and longer is considered to be even better.
Last edited:
Other than minor "source bloom" or widening of stereo images, spl from reflections (greater than 5ms) in "listening" room are not loud enough to generate an "ambiance" effect. (..though you can do this with an extra set of near-field speakers as SL did as a first effort on the Pluto, typically with a delay feature.)
Instead what you are hearing is a *wider dispersion pattern horizontally (both forward and reward of the speaker), along with what is often a very different diffraction profile. You also get to hear intensity differences generated by the reflections. Counter-intuitively, the more uniform the reflection is with regard to intensity (as in similar "loud" intensity from all near reflection surfaces) the less most listener's "hear" the room. (Toole has a section devoted to this in his book.)
*note: that wider dispersion generates an increased "mono-phonic" effect that tends to increase apparent depth (..the right ear hears more of the left loudspeaker and vice-versa.)
Finally irrespective of dispersion and any room effects, any open-baffle driver has effectively 3 different characteristics that are often all audible to some extent:
1. Qm is that of the driver itself with a Qts that's typically lower than in any box design.
2. Added resonances from the box effecting operation of the driver. (..though depending on mounting you might have different resonances, and often worse at low freq.s.)
3. The driver's character/operation becomes that of a "velocity" source as opposed to "pressure" source.
Instead what you are hearing is a *wider dispersion pattern horizontally (both forward and reward of the speaker), along with what is often a very different diffraction profile. You also get to hear intensity differences generated by the reflections. Counter-intuitively, the more uniform the reflection is with regard to intensity (as in similar "loud" intensity from all near reflection surfaces) the less most listener's "hear" the room. (Toole has a section devoted to this in his book.)
*note: that wider dispersion generates an increased "mono-phonic" effect that tends to increase apparent depth (..the right ear hears more of the left loudspeaker and vice-versa.)
Finally irrespective of dispersion and any room effects, any open-baffle driver has effectively 3 different characteristics that are often all audible to some extent:
1. Qm is that of the driver itself with a Qts that's typically lower than in any box design.
2. Added resonances from the box effecting operation of the driver. (..though depending on mounting you might have different resonances, and often worse at low freq.s.)
3. The driver's character/operation becomes that of a "velocity" source as opposed to "pressure" source.
Last edited:
Does it vary from system to system? I'd disagree when it comes to a low reflection system. The significant reflections are late, say 30ms or so, and they are encouraged. Hearing the back of the listening space is comforting imo.
If the reflections are well diffused it can be very effective, it's a one size fits all solution though. You can get a similar effect with omnidirectional speakers, it's more about polar response than whether or not they are box speakers, there are box dipole speakers.
Well, it can certainly vary from room to room. Largely depending on sound absorption materials (for a given bandwidth), but also room size (..with around 34 feet getting to that 30ms reflection.)
It can also depend on the pressure loss with distance of the loudspeaker/(system) itself: as in point-source vs. line-source.
As for late reflections being significant - that depends almost entirely on the spl of those reflections when compared against direct sound from the loudspeakers, most of which (at least at higher freq.s) will have very little significance because they are so much lower in spl than the loudspeaker's direct sound (particularly with respect to later/longer time arrival reflections).
(..I'm not really sure what "encouraged" means here.)
Last edited:
Encouraged meaning wanted, and not brought down by an excess of room absorption.
When done well, these later reflections are not particularly loud but they are audible as a separate event. It transcends just the SPL of it.
When done well, these later reflections are not particularly loud but they are audible as a separate event. It transcends just the SPL of it.
Your analysis is all well and good, but it seems to imply that there really is not much difference in listening to open baffle speakers versus box speakers. My experience is just the opposite. What I’ve heard is a major difference, particularly with orchestral music.
I would even go so far to describe it as more than a major difference. I would call it a night and day difference.
So at some point the analysis, at least for me, has to give way to what you really hear.
-within the source, yes.
-within a concert hall setting specifically designed for loud late arrival reflections relative to direct sound, yes.
-in a small (listening) *room context, no. 😉 (..with two exceptions: there are people that have either naturally or through design/repetition "messed-up" their hearing to reduce their ability to auto-negate the effects of (live) reflections in a small room; most anyone upon 1st walking into an unfamiliar acoustic environment will not immediately do that "auto-negate" feature.)
Look at any good research on the subject.
This of course is not to say that you aren't hearing a number of other effects that are actually contributing to the effect you are hearing. 😉
*though even here you could be listening in a retched room acoustic like a typical hard-surface bathroom.
Last edited:
"My" analysis isn't mine. There is a fair bit of research on this topic.
Nor am I implying that there isn't much difference to open baffle speakers versus box speakers (..I did of course specifically mention dispersion and diffraction). I tend to prefer an open baffle design within certain bandwidths (most particularly 70-300 Hz, though I also like it in the upper treble). I also like all three of those secondary effects I mentioned when done well - and two of which (the first 2) can ALSO be (mostly) accomplished with really good design that is not (strictly-speaking) open-baffle. In fact I rather hate the effects of the box on mechanical compliance - which surprise, surprise:
REDUCES LOW LEVEL (ambient) DETAIL OF THE SOURCE AND DEPTH-OF-FIELD. 😉
(..though some drivers display less loss than others.)
Last edited:
I'd think I'd know the sound of my own room, but I could be mistaken 😉 As I've come to find, the elements should not trounce each other, but sound as separate events whether they be intruments in an image, recorded or real ambience.
That's just it:
Once you know the sound of your room, you negate it. 😉
(..again though, with exceptions.)
Once you know the sound of your room, you negate it. 😉
(..again though, with exceptions.)
Try walking into an unfamiliar (truly unfamiliar) room and listening.
Then after several minutes, go out of that room for a bit and then go back in again.
BTW, it's NOT a theory.
Then after several minutes, go out of that room for a bit and then go back in again.
BTW, it's NOT a theory.
Toole gives a practical example in 7.6.1 Adaptation and Perceptual Streaming
He references
Bregman, A. S. (1999). Auditory Scene Analysis, the Perceptual
Organization of Sound, MIT Press, Cambridge, MA.
Benade, A. H. (1984). “Wind Instruments in the Concert Hall” Text of
an Oral Presentation at Parc de la Villette, Paris; part of a series of
lectures entitled “Acoustique, Musique, Espaces”, 15 May 1984
(personal communication).
He references
Bregman, A. S. (1999). Auditory Scene Analysis, the Perceptual
Organization of Sound, MIT Press, Cambridge, MA.
Benade, A. H. (1984). “Wind Instruments in the Concert Hall” Text of
an Oral Presentation at Parc de la Villette, Paris; part of a series of
lectures entitled “Acoustique, Musique, Espaces”, 15 May 1984
(personal communication).
Just the parts that are negative. For example, Allison boundary problems. Geddes also explained his philosophy on addressing the room reflections he thinks are negative.
http://www.gedlee.com/Papers/Philosophy.pdf