I don't think that we disagree, your points are different than my points, and I don;t disagree with them. It simply makes clear how examples like this can be complex to discuss and analyze. I hear "corner loading" concepts used all the time and I find the whole thing wrought with complexity, false assumptions and errors. I see very high potential for problems where others see only benefits. Personally, I don't do it and I don't recommend it and having listened to those who do I find the arguments superficial.
An externally hosted image should be here but it was not working when we last tested it.
Mind if I call these the Bumma?
The OS WGs are a big improvement over my collared JBL PT guides a la econowave. What specifically is improved from a performance standpoint is mostly in the top octave and boogie factor. Maybe it's just proud poppa. I haven't measured. That's a JBL 2226h on the bottom.
The sound of throat discontinuity is to my ears largely defined by a splashiness. Call it HOM or "lack of clarity" if you like, but it's like the cymbals are recorded in a tiled shower. Shaping the throats on my Waveguides as above took a lot of careful finish sanding (it's perfectly smooth and even to the touch, any apparent bumpiness is the way the multiple material layers photograph), and I used clay like the doc does for the last tiny bit of gap fill (there's a gap left by the bugscreen retaining ring after the bugscreen is removed)
An externally hosted image should be here but it was not working when we last tested it.
I'd like to put some directional speakers into room corners, or at least against a wall near corners. I figure that with, say, 70 degree coverage that can't be too bad a thing. I understand that this may not be optimum but can it be made to work well enough?
Badman, thanks for the photos. Did you make smoothness your priority, or following the OS contour? and how did this work for you?
Badman, thanks for the photos. Did you make smoothness your priority, or following the OS contour? and how did this work for you?
There is no answer to a question like that, because it depends on so many personal factors. For example, what is "good enough" seems to be a lot lower if you build it yourself than if you buy it. It's called "Beranek's Law". And the WAF sets a very low standard on "good enough". There are lots more ... So basically if you build it yourself so as to also please your wife, its likeley to sound like XXXX, but it will be "good enough" if it's small with nice wood and a shiny finish.
Continuing my earlier question, I was thinking that the higher frequencies would avoid early reflections from the walls as their pattern would "fit" the corners. The lower midrange and upper bass might be augmented by the corner in a relatively benign way, and could be EQ'd down, and the bass would be OK seeing as a corner placement is useful and two opposite corners can be better than one.
Yes, this is basically correct. But its not really a question as much as just a statement of fact.
But moving the same directivity out of the corner will always work better since it makes the "relatively benign" prolems even more "benign". Al this gets into degrees of "less than optimal" - always a problem to resolve. But what is unchanging is that one needs to have a constant and narrow directivity - thats the first "major" requirement. Compromise on this and most of the other compromises pale by comparison. Once you have "true" Narrow CD, then you can begin to talk about compromises of placement, etc.
Don't have Narrow CD? Well, the rest is kind of irrelavent. Thats why I obsess over directivity, because its control is a necessary requirement which should not be compromised.
But moving the same directivity out of the corner will always work better since it makes the "relatively benign" prolems even more "benign". Al this gets into degrees of "less than optimal" - always a problem to resolve. But what is unchanging is that one needs to have a constant and narrow directivity - thats the first "major" requirement. Compromise on this and most of the other compromises pale by comparison. Once you have "true" Narrow CD, then you can begin to talk about compromises of placement, etc.
Don't have Narrow CD? Well, the rest is kind of irrelavent. Thats why I obsess over directivity, because its control is a necessary requirement which should not be compromised.
I found a measureable difference - a couple of dB at the upper end. Basically, I found that removing the screen almost offset the loss that results from using the foam. Since it is unnecessary with the foam in place I always remove it. But without foam you would have to think very carefully about removing it because "bugs" can, and probably would, get down into the throat and gap.
I have removed some open-cell foam from a fan filter in an old PA amp from the 80's (yamaha), and it was rotted, sticky and fragile. Could this happen to the foram you use (or similar foam we can get from aquarium shops)? That would be a concern, especially if there is not bug screen to protect the throat...
Sounds about right- I didn't do a lot of controlled testing but the good doc's approximate equivalence sounds about right.
Now I have to figure out some impedance plot jaggies.... I think Lpads might be a lot more resonant than we think (I have one in place as a variable parallel damping resistor)
Not sure that's the case (I've seen some previous discussion of L-pad related variations), but I'll be running impedance sweeps tonight anyway (probably) so I'll try it at a couple positions for you. Response variation is going to largely depend upon the rest of the crossover and the location of the L-pad and I (wrongheadedly) haven't set up a good method for posting measures.
I don't care about using the term "waveguide". That's a phrase I rarely use in audio. I tend to describe horn features, i.e. constant directivity, conical, oblate spheroid, etc.
But I do think that putting an omnidirectional sound source at the apex of a trihedral corner generates a wavefront that is defined by the walls and has constant directivity. To me, this is an axiom, not subject to opinion or debate.
For that matter, omnidirectional radiation can have constant directivity, and so can radiation into half-space. An example is a subwoofer on the ground, which has fairly constant directivity at low frequencies. Constraining the pattern further to eighth-space is no different. It can be constant directivity, and in fact, it must be. If the source directivity isn't narrower than the boundaries that confine it, then the boundaries set the pattern.
Indoors, room modes modify the pattern, I think we would all agree. Only if the trihedral corner is completely open would there be no room modes. In a real-world situation where the room is closed, room modes take over below a certain point, and make pockets of hot and dead zones throughout the room. But above the Schroeder frequency, the walls still constrain the pattern and provide constant directivity.
I learned about this empirically, and later sought to learn why it worked so well. Essentially, I felt that if a Klipschorn were made to provide constant directivity, it would provide better room coverage. It did, and it did some other really interesting things too, seeming to give better imaging and soundstage in addition to improved coverage. I first thought it was solely because of the more uniform reverberent field but later began to think it was also due to the self-balancing nature of having two speakers toed-in 45°, with forward axis crossed in front of the listener. I first noticed this in 1980, when I started building cornerhorns having constant directivity.
The basic design approach is to let the room's corner set woofer directivity from the Schroeder frequency (~200Hz) up to maybe 400Hz or so. A midhorn is made as large as practical and it blends with the woofer in that 200-400Hz octave. A tweeter is crossed over at a point where it can be done and maintain constant directivity, typically between 1kHz and 1.5kHz or so. All horns have a 90° pattern, and blend well together. Below the Schroeder frequency, multisubs can be employed to provide a uniform sound field at low frequencies.
I agree. Of course, the source would need to be baffled seamlessly into the corner, and secondly, the corner would need to be ideal.
On this second point, my walls tend to have selective absorption and I don't trust them to do this job.
LOL !
StudioRoom Forum - Computer Simulation of Room Acoustics - Wayne Parham, March 21, 2006 at 14:39:33
Hello Wayne, how did your bet turn out ?
Are you two still struggling to find the winner after roughly four yeas of work on the subject ?
Michael
StudioRoom Forum - Computer Simulation of Room Acoustics - Wayne Parham, March 21, 2006 at 14:39:33
Hello Wayne, how did your bet turn out ?
Are you two still struggling to find the winner after roughly four yeas of work on the subject ?
Michael
We never agreed on the conditions of the bet, specifically, what software would be used to test with.
At any rate, that's a different subject because it is a discussion of what multisub configuration to use, which is intended to improve response below the Schroeder frequency. The range where the cornerhorn is able to use the walls to set directivity is above the Schroeder frequency. The two approaches can be used together, in whatever way suits your fancy, but that's a different subject.
Well, yes, room acoustics influence everything and wall damping is a big part of the deal. But I think that's another point too, related but separate. The absorption of the walls influences room modes and ultimately bass response because they set the damping. Absorbent walls acts something like panel dampers, whereas rigid walls tends to make room modes stronger and more defined.