Here iis Kimmo's explanation:
Post in thread 'Some help with lobing' https://audiosciencereview.com/forum/index.php?threads/some-help-with-lobing.22661/post-755427
For simple testing you could use freeware Edge. Then migrate to test baffle made of cardboard. To make smooth edges use painters tape.
If you crossover between the woofer and mid at 250-350Hz, it is feasible in many cases to have the center-to-center spacing within a 1/4 wavelength.
Crossing over between the tweeter and mid at something like 2.5khz, then the 1/4 wavelength is NOT feasible. The old rule of thumb was to stay within 1 wavelength, and the closer the better. Kimmo showed that a CtC spacing of around 1.2x the wavelength allowed better integration of the sound waves and a better outcome than the old rule of thumb. ("Better outcome" was probably directivity/power/vertical lobing...see the link krivium posted in #261.)
Gotcha. Can't say I noticed many issues with the big speakers with current placement, though I could definitely hear the vertical lobe sitting on the floor. The speakers in general were sensitive to vertical movements.
So when you folks say the lobe shoots up with the mid up top, I interpret that as with standard two ways the lobe is shooting down? Troels seems to like to put his mid above the tweeter in many designs but I also don't really consider him to be the top authority in a lot of things. Frankly evey speaker I've had images better when the head is at tweeter height.
I have edge, I can interpret the results some what but not sure which placement is most beneficial. IEC sized baffles seem to be the best lol but yeah.
As far as spacing, I have some drivers that can get withing the 1/4 wavelength guideline I might play with and see how it sounds.
So when you folks say the lobe shoots up with the mid up top, I interpret that as with standard two ways the lobe is shooting down? Troels seems to like to put his mid above the tweeter in many designs but I also don't really consider him to be the top authority in a lot of things. Frankly evey speaker I've had images better when the head is at tweeter height.
I have edge, I can interpret the results some what but not sure which placement is most beneficial. IEC sized baffles seem to be the best lol but yeah.
As far as spacing, I have some drivers that can get withing the 1/4 wavelength guideline I might play with and see how it sounds.
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Perhaps you could use paper, pencil and scissors in trying to duplicate a profile. It may be enough to decipher the intent.
Perhaps, but is this relevant? Clearly the presence of the lobes is the symptom, but the effect of floorbound waves doesn't manifest until it comes back to you, maybe after it joins the reverberant field once it goes past you the first time.
Well I guess it depends on how you listen, I've just been finding myself on the floor in the living room, just kinda feels better. Not really an issue when sitting in a chair.
That's different of course 😉 The point was that the lower off-axis radiation is still relevant from the listening position but in a different way, and sometimes for a different reason.
1. Full spectrum reflection from the ceiling
2. Mid and treble ceiling reflection with the crossover region missing due to a null
3. Ceiling absorber to reduce the reflection, especially all of the middle/higher frequencies.
I would suggest 2 is the worst and 3 is the best.
It was written...
I may be misinterpreting something, I don't know.. but I don't feel that aiming a null to the ceiling reflection point is ideal. Consider these three scenarios...
1. Full spectrum reflection from the ceiling
2. Mid and treble ceiling reflection with the crossover region missing due to a null
3. Ceiling absorber to reduce the reflection, especially all of the middle/higher frequencies.
I would suggest 2 is the worst and 3 is the best.
I can't decide if @ wafflesomd's speakers are haunted or his house 😉
(the never ending problem)
(the never ending problem)
Well let's say we talk about monitoring ( implying studio work on audio as it is how i interpret Wafflesomd work presented here): one of the first thing acousticians does when working on control room acoustic is defining first reflection point ( to create a RFZ) and especially on ceiling. The strategy is rarely to absorb ( only) if they have choice but rather use diffusion or redirecting ER outside the sweetspot ( if dimensions allow), then what is still untreated if often used as wideband absorber through absorbsion and or a mix of bass trapping.
It's the reason you see 'clouds' in small control room rather than absorbers ( to redirect ER) or 'strange shape' of overall room.
So i would reorder your ranking this way: 1 is a no-no in this case, 2 and 3 is ok if they work together: xover in the range 1khz/3khz + diffusors working in this range ( it's the range ceilling diffusors depth and distance to listening point allow for efficiency of diffusors).
Sure it hurts power response and is not an ideal but it's way more troublesome than to have comb filtering in this freq range when mixing.
An other answer if you can't treat ceiling or want to minimise some other sbir issue (floor/ceiling bounce) is mtm or variants.
I can go along with that. In a domestic setting I would also suggest a cloud, although the amounts (power and so forth) would be slightly different.
https://www.soundonsound.com/techniques/sos-guide-control-room-design
Imagine you are creating the control room of a studio, and have the luxury of employing professionals to design and build the space to have great acoustics. Depending on who you went to, you might get offered one of a number of different design philosophies, such as Live End Dead End (LEDE), non-environment or Reflection-Free Zone (RFZ). But which is best? This guide compares different design philosophies, explaining how each affects the sound in the room and what the engineer hears as they work at the desk.
. . .
Non-environment Rooms
One approach to controlling early reflections is to suppress them via absorption. A ‘non-environment’ approach goes even further and removes the reverberation as well as the early reflections, to create a quite dead acoustic. This design philosophy has been successfully applied to many control rooms.
. . .
Live End Dead End
One way of reducing the amount of absorption and mitigating the high power levels needed for a non-environment is to retain the reverberant tail in the control room, and suppress only the first-order reflections that cause the most coloration. This will lengthen the time between the direct sound and the first significant room reflection, so that the room sounds bigger. Many studio designs try to achieve this goal, the simplest one being the Live End Dead End (LEDE) design proposed by Davies and Davies in 1980
. . .
Reflection-Free Zone & Controlled Image Design
The two methods described so far use brute force to suppress early reflections. Although this has some advantages, especially in the case of the non-environment room, they are impractical for many rooms due to the amount of treatment that is required. A better approach is to only put treatment where it is needed, and this is the principle behind design philosophies such as Reflection-Free Zone and Controlled Image Design rooms. . . . By defining a reflection-free zone around the listening position, and by drawing lines from the image loudspeakers, one can see which portions of the wall need to be made absorbent. The absorber in these locations only needs to treat the mid- to high frequencies that have the strongest effect on creating stereo images and coloration
. . .
Ambechoic Designs
Instead of absorbing every reflection, as in the non-environment room, another approach is to diffuse every reflection by putting broadband diffusers on every surface, except the floor. In such a room, the impulse response looks like that shown in Figure 11, with a dense set of reflections all at a reduced level. Over a large part of the room the reflections are at least 20dB below the direct sound. . . . In terms of practicality, all these approaches use large numbers of diffusers and so are difficult to achieve in a home studio. Diffusers need to be at least a quarter of a wavelength deep to be fully effective, which means that you would need about 200mm-deep diffusers, about the depth of a bookcase, all around the room to achieve diffusion down to 500Hz.
In fact i don't have to imagine the situation as it was part of my job in a previous life. And i've heard every kind of rooms philosophy you linked ( maybe the exception being a 'real' LEDE as the one i've heard was redesigned/repurposed at that time) and surely not ambechoic as to my knowledge there is not many rooms built like that (Massenburg's room in Nashville's Blackbird studio C is the most iconic example ).
So yes there is difference between these approach but it's not really different than the situation you face with monitors: you could encounters in studios horns systems, mid and tweeter dome, coax,.... all gives a different rendering too, but except for rare exception it won't stop you to work and have a nice result if you can spend a bit of time in the room with reference recordings ( or work on nearfield but... no spend some time listening the mains/room with reference recording!).
I know what I like but understand others can have different preferences too. Of all the philosophy i prefered the one which were the less oppressive long term eg: a Non Environnement room is very oppressive to me, luckily T. Jouanjean ( Northward acoustics) implemented evolution to the design and now offer Front to Back which is a non environment but with human into the place took into account... 🙂.
So RfZ / Cid or FtB ( but with coax loudspeakers in place of Atc) for me please... but... you can't implement this at home easily: it require 'big rooms' and most important a very decoupled one ( sound isolation) which means box into a box and which is to me the most important specification of pro control rooms.
Having no perturbation from the outside world is game changer: you can 'read' deeper into the message...
Anyway, for home i live in countryside despite not having real soundproofing and i'm lucky to have a sloped ceiling/roof from 2,1m to 3,8m and it give 80% of the room treatments needed imho. Redirecting ER above sweet spot is golden... ask Dave ( Planet10), he built his home around the principle! 😉
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I don't think I'll have funds to do anything anytime soon thanks to car problems and sick kittys. I was going to get some data on the big speakers to share, anything that would help other than the typical measurement process? Timing reference? I was just going to mic in between tweeter and mid at 1m. Maybe closer since I have to do it in the garage.
Bleh, I got data but it always looks like butthole, I just can't get things far enough from the ground. No access to ground plane measurements space.
The 'ideal' example of LEDE was to have a measurement result called "RT60". That was a "Reverb Time" of - 60 dB @ 1 second.
The word 'reverb' was probably not the best because it conjures-up the idea of a sound-effect.
What it meant was that ALL frequencies decayed at rate of - 60 dB in 1 second. IE. a tone burst of any frequency = the same decay.
This was not achieved without substantial design and trapping. I was involved in one such build. Very impressive sound.
PS. The "Live End" is the 'in wall' main monitor speakers. The RT60 measurement also comes from the main monitor speakers.
Yeah I'm listening to them right now, just let me know what you need
Would you mind sharing some impulse response files? Generally with the mid and tweeter >1m from boundaries you can reach gates just around 4ms. That is enough to get the mid to high crossover right. The woofer to mid of course is another story. Part of the reason designing a more-than-2-way is problematic Is that you must be able to make measurements with time windows around 10ms, which requires both more than 2,5m-3m distance from boundaries and, because of the size of drivers and the baffle step involved, bigger measurement distances up to 2m. Most of us have no option but going outdoors for that (or rent some sport venue with high ceilings).
I figure it'd be easier to look at the mdats instead of me exporting something wrong.
https://drive.google.com/file/d/1yPf2Ovf8eLXdrFrCye0mBhBFyplHUP7T/view?usp=sharing
https://drive.google.com/file/d/1yPf2Ovf8eLXdrFrCye0mBhBFyplHUP7T/view?usp=sharing
Your unsmoothed response of the mid looks like this. I guess your time window settings are off (I noticed a 13ms setting, that is roughly 4,5m direct-indirect pathway difference 🤔). I'm not home in REW at all, maybe others here can and will apply correct time window settings.