Here it is for those that are interested
https://www.diyaudio.com/community/threads/t25a-simple-waveguide-profile.423131/
Hello All,
I have been reading along following this conversation about directivity.
Much, perhaps most of the thought process comes from the Harman research about listener preference in a standard listening room.
Using the Revel F328Be speaker as a sample, the drivers stairstep smaller in diameter and the woodwork is carved to effect a smooth continuous slightly increasing directivity Index. Get to the tweeter, then a waveguide is required to maintain the smooth continuous DI. Even then, the top
~octave begins to beam.
The directivity is held close to + / - 70 degrees for most of the BW of the speaker.
Is that + / - 70 degrees by design or is it the nature of cones and domes? You know, the best we can do?
Thanks DT
I have been reading along following this conversation about directivity.
Much, perhaps most of the thought process comes from the Harman research about listener preference in a standard listening room.
Using the Revel F328Be speaker as a sample, the drivers stairstep smaller in diameter and the woodwork is carved to effect a smooth continuous slightly increasing directivity Index. Get to the tweeter, then a waveguide is required to maintain the smooth continuous DI. Even then, the top
~octave begins to beam.
The directivity is held close to + / - 70 degrees for most of the BW of the speaker.
Is that + / - 70 degrees by design or is it the nature of cones and domes? You know, the best we can do?
Thanks DT
The F328Be doesn't have the front panel detailing that the Salon 2 has, as a result there is more effective flat baffle area. The DI is quite flat between 700 Hz and 7K, rising and falling at either end relatively quickly to give it an overall rising DI. The wider flat baffle area gives it the more constant directivity through the major frequency range. They may have chosen the dimensions to target that directivity but the outcome is a consequence of what happens with those size drivers in that configuration.
The best is dependant on a lot of factors but a speaker like that sounds good in many average size rooms at average listening distances across a wide range of genres. Average of course changes depending on which continent you are on, that has an effect on whether the speaker is too big, too small or just right.
The in room response is smoothly falling without any real peaks or dips, they get this from downsloping the on axis and listening window just a bit to offset the fairly constant directivity.
The best is dependant on a lot of factors but a speaker like that sounds good in many average size rooms at average listening distances across a wide range of genres. Average of course changes depending on which continent you are on, that has an effect on whether the speaker is too big, too small or just right.
The in room response is smoothly falling without any real peaks or dips, they get this from downsloping the on axis and listening window just a bit to offset the fairly constant directivity.
Can the “best we can do” directivity be determined from graphs/charts?
Versus
Versus
I’m not certain it can be…
Versus
Versus
I’m not certain it can be…
One of the better tools that we have. Otherwise we are just waving our arms all around.
Hello All,
I am not necessarily thinking that widest is best. Perhaps it is a matter of taste. Sitting at my bench near field I kind of like + / - 45 degrees. Think compression driver with a waveguide.
Is + / - 45 degrees doable with cones and domes? To me it seems like + / - 70 degrees is where the cones and domes technology tends to gravitates.
Thanks DT
With modern off-axis data as spectrogram I look also beyond -3dB line (eg. -12dB) Deep waveguides and horns cast more sharp lined beam than open drivers.
Like this, cpmpare to shallow coaxial TAD in my previous post
or this small horn monitor
Like this, cpmpare to shallow coaxial TAD in my previous post
or this small horn monitor
Sometimes I wonder whether this is akin to what we are doing when we put different drivers in different cabinets:
Exactly how wide is "ideal"?
And for which frequency bands?
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And for what applications?
Hello,
Considering that this spinorama stuff started in a standard Harman listening room of a given size and with given room treatments. I can understand that the preference for Directivity Index would gravitate towards what we are used to seeing today.
Consider differing listening spaces. In my last home where we had larger groups (teenage young people) in the large 2nd story room, music and home theater, over the 3 car garage below I had 90 X 50 degree coverage CD waveguides to reach the back of the space.
I am finding that speaker coverage angle often should be adjusted to the listening space.
Thanks DT
^ This!
e.g. a wide radiating speaker with mid dome in rounded baffle will sound great in a mid size living room when they can stand free with space to left and right. Half meter to the left a glass front, and half meter to the right a bookshelf, and it would sound not more so well. 7" mid + tweeter in larger waveguide might give the better result then.
e.g. a wide radiating speaker with mid dome in rounded baffle will sound great in a mid size living room when they can stand free with space to left and right. Half meter to the left a glass front, and half meter to the right a bookshelf, and it would sound not more so well. 7" mid + tweeter in larger waveguide might give the better result then.
In other news... I am starting the process of laminating the midrange-tweeter baffle. The outer layers will be solid cherry, with a Baltic birch plywood core.
https://audioroundtable.com/misc/Loudspeakers_and_Rooms.pdf
This is classic Toole, many aspects considered outside of Harman room. Generalizations can be made but still some like apples, some oranges...
This is classic Toole, many aspects considered outside of Harman room. Generalizations can be made but still some like apples, some oranges...
Yes, classic Toole / Harman.
Harman knows well that is important to match the angle of coverage to the venue. The people in the back row want to hear some direct sound, not just room reflections.
It is interesting to me that vast majority of home HI-FI speakers that we see data for, you know the cones and domes that we are talking about here have coverage in the + / - 60 to 70 degree range. I tend to think that the home listening spaces that most of us sit in are not too far removed from the Harman International Standard Room.
This little bit is clipped from section 1.2 of the Toole PDF, I think.
As the directivity of the sound source increases—in the direction of the listener or microphone—the critical distance also increases. In thinking about what may happen in the small rooms of interest to us, assuming no other differences, the critical distance * will be larger because these rooms have proportionally more sound-absorptive material and the sound sources have significant directivity, and are aimed at the listener. As a result, we may find that we are not listening in the reverberant sound field.
(this is the best I found in the PDF that speaks about directivity and room size. This clip was taken from from the Large Room section of the PDF.)
* The distance from the source at which the direct sound equals the level of the reverberation is the critical distance (also known as reverberation distance, reverberation radius).
Thanks DT
Just for grins I just moved a new pair of new JBL AC2212/00 100 X 100 degree coverage speakers into my not large bedroom size media space for a test drive.
Thanks DT
Unfortunately this is a 20 year old paper. The 3rd edition of Sound Reproduction is also almost 8 years old.
Does anyone have anything more recent?
Does anyone have anything more recent?
Yes, Toole's new forthcoming edition.
https://www.audiosciencereview.com/...s-rainmaker-speaker-review.40906/post-2173873
https://www.audiosciencereview.com/...s-rainmaker-speaker-review.40906/post-2173873
Hello,
There is not too much under the sun that is new.
My favorite acoustics text is a MIT Text from 1954.
Take a look at this one.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2677334/pdf/JASMAN-000124-000450_1.pdf
If I were to state a preference for direct sound to reflected I would start at 60% direct to 40% reflected.
Thanks DT
Another one.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4744263/pdf/13414_2015_Article_1015.pdf
Sure reads like Direct to Reflected ratio has a serious effect on distance perception, you know perception of "sound stage".
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I think a lot was already known(researched) for a long time. Just got lost in the cloud of rumors, opinions, influencers, etc and above all the captivating effect of numbers (keep thinking of 42 ;-))
I have the laminated sections complete. There are three lamination layers in the midrange-tweeter baffle. The baffle is 350 mm H x 286 mm W.
The outermost layer is solid wood, with the grain oriented vertically. I glued two boards together to get the needed width.
The middle layer is composed of a Baltic birch plywood core that is 280 mm H x 146 mm W, bonded to a solid wood edging that is 70 mm wide. The solid wood has the grain oriented horizontally.
The innermost layer is composed of a BB plywood core that is 300 mm H x 186 mm W, bonded to a solid wood edging that is 50 mm wide. The solid wood of this layer is oriented vertically.
In order for this process to work, the solid wood must be planed to the same thickness as the plywood, which in this case was 17.9 mm. I used Titebond wood glue to bond the solid wood to the plywood cores, but I will use epoxy to bond the three layers together. The total thickness will be 54 mm.
If the weather is nice tomorrow, I will router the holes in each layer, including the recess in the outer layer. Then I will epoxy them together.
It feels good to make some progress.
j.
The outermost layer is solid wood, with the grain oriented vertically. I glued two boards together to get the needed width.
The middle layer is composed of a Baltic birch plywood core that is 280 mm H x 146 mm W, bonded to a solid wood edging that is 70 mm wide. The solid wood has the grain oriented horizontally.
The innermost layer is composed of a BB plywood core that is 300 mm H x 186 mm W, bonded to a solid wood edging that is 50 mm wide. The solid wood of this layer is oriented vertically.
In order for this process to work, the solid wood must be planed to the same thickness as the plywood, which in this case was 17.9 mm. I used Titebond wood glue to bond the solid wood to the plywood cores, but I will use epoxy to bond the three layers together. The total thickness will be 54 mm.
If the weather is nice tomorrow, I will router the holes in each layer, including the recess in the outer layer. Then I will epoxy them together.
It feels good to make some progress.
j.
My wife was quizzing me on what the full up cost for this latest project is likely to be, including the eventual woofer/subwoofer cabinet upgrade to twin SB34NRXL's per side.... She has decided that she might be in the mood for a new guitar.
https://www.gibson.com/en-US/p/Electric-Guitar/Les-Paul-Supreme/Fireburst
I guess I have no grounds to object...
https://www.gibson.com/en-US/p/Electric-Guitar/Les-Paul-Supreme/Fireburst
I guess I have no grounds to object...
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Very nice, if you need to increase your budget a little, I once owned a Fender Custom Shop Strat Ltd 59 with Birds Eye Maple fingerboard, it had an amazing metallic flake finish using a nitocelluslose laquer. It felt really good, but it was too much guitar for a drummer. Nice while I had it though 🙂
Closest link I could find
https://www.fullersguitar.com/fender-custom-shop-ltd-ed-65-strat-nos-aged-burgun.html
