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Multi-Way Conventional loudspeakers with crossovers

pattern control below 400Hz
pattern control below 400Hz
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Old 20th January 2019, 08:10 PM   #51
ScottG is offline ScottG  United States
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Yeah, Princeton's 425 Hz is enough for head-shading effects, but really doesn't meet the <400 Hz requested here. MBK does state that his data is good to somewhere between 150-200 Hz though, and that there is the grass/ground reflection around 300 Hz that results in that 300 Hz dip/bump in some of the graphs.

I actually think that MBK got the interaction with baffle better than anyone. Not only is it an evolutionary process that he presents with and without baffle, he specifically makes a comment with full polars that a larger baffle INCREASES rear output as seen here with no baffle, 12" wide baffle, and 16" wide baffle. Basically ANY substantive baffle increases rear output to a fairly low freq. (when considering the small width of the baffles tested), the larger the baffle, the more rear-output to a lower freq.:

Adventures in cardioid


This lets me know that IF I were doing a <400 Hz resistance design (or perhaps most any cardioid design), that I'd want to minimize the baffle's size to almost nothing to reduce the output to the rear.


BTW, I personally am not a fan of most resistance designs (moreso as freq.s increase into the lower midrange and up). It's not the directivity, rather it's what it does to low-level excursion and it's why I'd go for a DSP "double-driver" design (if having that as an option). Note the various subjective descriptions/results of all of Kimmo's designs - he loved that large bass cardioid, but when he got into the midrange: not so much. (..for me resistive mid.s tend to kill sound-stage depth).
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Last edited by ScottG; 20th January 2019 at 08:23 PM.
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Old 21st January 2019, 04:21 AM   #52
hollowboy is offline hollowboy  Australia
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Quote:
Originally Posted by Cask05 View Post
I've had success using "A/B" using the trace arithmetic functions.
Thanks, will try it out. I was considering exporting the SPL plot as text and normalising / plotting it myself in a spreadsheet.

This is mainly for nerdy gratification. Looking at the bigger picture, I'm not sure how much time I should put into plotting, tweaking and getting a 'perfect' pattern. It seems as if moving the box from outside to inside gives a pattern so different from the outdoors measurement, that a crude measure might be just as good as a sophisticated one.

My current rough plots look like I have OK rear reduction <300Hz and good side reduction 300-500Hz (relative to the sealed box). If my patience runs out, that will have to be good enough.

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Originally Posted by Juhazi View Post
hollowboy is interested in lower midrange, below 400Hz!
Yea. That's my target, but not set in stone. If 350 or 500Hz works better in practice, that's how I'll roll - hooray for DSP & easy Xover changes.

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Originally Posted by Juhazi View Post
The difference of dipole and cardioid is in what happens after 30¤ off-axis. The dipole attenuates rapidly up to null at 90¤ but cardioid keeps on radiating only slightly attenuated. A supercadioid has minimum around 120-150¤, real cardioid at 180¤.
Looking at prior work / plots, it looked like 0, 90 and 150 degree measurements were quickest way to spot whether I was getting dipole(ish) or cardioid(ish) pattern. Quick = good for getting through a couple of tweak-and-test cycles in an afternoon.

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Originally Posted by ScottG View Post
BTW, I personally am not a fan of most resistance designs (moreso as freq.s increase into the lower midrange and up). It's not the directivity, rather it's what it does to low-level excursion and it's why I'd go for a DSP "double-driver" design (if having that as an option).
The prototype seemed OK for excursion with one OB 18" playing 50-400Hz. In the final (hopefully) version, I intend to use sealed boxes for LF (2x the cabinet pictured in post 28), so I can set the sub/midbass crossover to whatever seems best.

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Originally Posted by ScottG View Post
Note the various subjective descriptions/results of all of Kimmo's designs - he loved that large bass cardioid, but when he got into the midrange: not so much
Are you referring to this subjective description from the KS-2125 page?

"There's not too much resolution at midrange. Mild directivity step from midrange to tweeters keeps harshness away, but sometimes midrange sounds pronounced. Height of speaker increases this feature because room height is only 248 cm and roof is reflecting (painted pine panel)."

My goals are probably different enough that this is N/A. I'm aiming to use my perforated box 100-400Hz (ish), whereas the KS-2125 used them 20-220 and 220-1800Hz.

Also, I'm not fancy enough to worry about "sound-stage depth" or any of that stuff. For most of the music I like, that's not a thing I even think about.
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Old 21st January 2019, 06:20 AM   #53
Juhazi is online now Juhazi  Finland
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I haven't heard Kimmo's speakers, but like I said in my previous post, a large waveguide (and for the most a horn) gives such a focused sound that transition is noticed (too?) easily. Ear/brain is very sensitive around 1-4kHz. In a Finnish hifi forum K has said that he didn't like the sound of cardioid+horn and that room is the king anyway. He values high clarity and sharp imaage, definition very much. But still, in one version there is a backside horn added obviously for "ambience")

In this respect we listeners are very different. Many hate and some love dipoles and panels. I get easily tired when listening to conventional or highly directive speakers, they sound unnatural and obtrusive to me.
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Old 21st January 2019, 07:30 PM   #54
ScottG is offline ScottG  United States
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Originally Posted by hollowboy View Post

..Are you referring to this subjective description from the KS-2125 page?
All of them in the aggregate with respect to midrange, though he loved that bass bass design (KS-2125) in particular. Also look at the evolution of his designs (ie. look at the date vs. the design).

Note that the KS-2125 has a crossover around 250 Hz.


Read his description for the KS-585 (..with resistance bass and mid.s):

KS-585
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Old 12th February 2019, 12:34 AM   #55
hollowboy is offline hollowboy  Australia
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Making slow progress:

-I have complexity addiction
-I'm trying to build this from existing materials / clear my shed / use up scraps. Marie Kondo would approve
-I fail at the "measure twice cut once" thing

The thick trans-laminated cabinet edges were largely made from of plywood offcuts. The multi layered section is only a few cm deep: I want just enough material to allow for some rounding of the edges. Any more would be extra weight.

I also tweaked the plan, making the horn closer to square (90 x 80 degrees). The mouth is now 500mm high, with 300mm of baffle above it (the section covered by tools in the picture), so it should have ~symmetric pattern control.

The face sections are a laminate [ bamboo || ply || plastic grid ] to try for a high amount of strength and damping for a relatively low weight. I'm using a double layer of bamboo in key spots, to allow me to grind + sand more of a curve into the mouth-baffle transition.

Just visible on the right of the pic is one of the holes for the leaky bass.

TL;DR: I'm trying to smoosh a lot of my recent design ideas and experiments into one project, and make it pretty.
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Old 12th February 2019, 12:46 AM   #56
pcgab is offline pcgab  United States
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pattern control below 400Hz
Very interested to see how it comes out. I think I 'understand' the leaky bass section, need to read up a bit more on that.

Keep up the good work!
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Old 16th February 2019, 07:15 AM   #57
hollowboy is offline hollowboy  Australia
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I think I 'understand' the leaky bass section, need to read up a bit more on that.
I don't fully understand it either. I can visualise how a figure 8 pattern can form but not the more complex shapes.

Here are progress shots, showing I how I'm setting the bamboo/plywood panels slightly into the shell, then grinding the shell back to get the edges flush.

This grinding step means it doesn't matter that I jigsawed together a bunch of wonky scraps and offcuts for the trans-laminated part - it makes me a bit sad when I see (otherwise amazing) projects that do CNC translam from whole sheets, generating enormous amounts of offcuts and waste.

The blobby bits in the photo are where I'm filling in chips and gaps with a slurry of glue + wood dust. The bamboo 'heals' remarkably smoothly. I guess it is because the fibres of the normal panel are so smooth / tightly packed that the fixed up section doesn't stand out. In real wood, filler sections look oddly blurry, like they've been photoshopped IRL.
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File Type: jpg grind after.jpg (628.2 KB, 207 views)
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Last edited by hollowboy; 16th February 2019 at 07:22 AM. Reason: added extra 'blobby' section; grammar
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Old 17th February 2019, 02:57 AM   #58
pcgab is offline pcgab  United States
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pattern control below 400Hz
Quote:
Originally Posted by hollowboy View Post
I don't fully understand it either. I can visualise how a figure 8 pattern can form but not the more complex shapes.
Exactly, the figure eight _mostly_ makes sense to me. By mostly I mean, nearly, of course.


Quote:
Originally Posted by hollowboy View Post
Here are progress shots, showing I how I'm setting the bamboo/plywood panels slightly into the shell, then grinding the shell back to get the edges flush.

This grinding step means it doesn't matter that I jigsawed together a bunch of wonky scraps and offcuts for the trans-laminated part - it makes me a bit sad when I see (otherwise amazing) projects that do CNC translam from whole sheets, generating enormous amounts of offcuts and waste.

The blobby bits in the photo are where I'm filling in chips and gaps with a slurry of glue + wood dust. The bamboo 'heals' remarkably smoothly. I guess it is because the fibres of the normal panel are so smooth / tightly packed that the fixed up section doesn't stand out. In real wood, filler sections look oddly blurry, like they've been photoshopped IRL.
They can be very wasteful unfortunately. I really like your approach to building, it's awesome to see you utilize every bit you can.

The wood dust, glue trick is an awesome one. I use that for all sorts or repairs, gap filling, etc.
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Old 17th February 2019, 08:19 AM   #59
kimmosto is offline kimmosto  Finland
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I can see some discussion about KS-585, KS-2125 and KS-1804.
Room acoustics in our living room was very bad at mid...highs a decade ago when those speakers were designed and built. No acoustic panels on the walls ceiling. 700 ms humps at mid...treble in EDT spectrum due to flutter echo between windows in front and back, and reflective ceiling did not help a bit. Resolution was low and sound dead and sometimes harsh. That time I was in war with bad room acoustics, and especially KS-1804 was close to final statement how this war is possible to win with quite small speaker, though changes are still very low. Bad room acoustics could beat you anyway depending on personal preferences, so acoustic treatment targeting low and flat EDT is more final solution giving freedom to select speaker design and drivers by overall quality and preferred sound nuances - not just strong directivity.

Leaking cardioid bass is very flexible application, but also very ineffective sucking all power and excursion available. Bass unit with 2x18" (KS-2125 and KS-1804 mk I+II) has been tested for example in 6m2 bathroom with brick walls, 15m2 concrete "bunker" and large living rooms total area >40m2. Room EQ and level adjustment for bass range is not required though the lowest axial mode could be boosted in small sturdy rooms and some narrow or small dips exist anywhere. Speaker location is not so critical than with omni or dipole to get balanced sound, but locations are worth to optimize anyway because these are not headphones either.

I haven't done much diy designs since acoustics of our living room was improved. Mostly commercial speakers without special directivity tricks. Therefore the latest history of my design does not reveal any progress or trend. I can and will design anything if someone else purchases components and builds cabinets
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Old 13th March 2019, 04:30 AM   #60
hollowboy is offline hollowboy  Australia
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Originally Posted by kimmosto View Post
I can see some discussion about KS-585, KS-2125 and KS-1804.
Thank you for your comments. I didn't realise (until now) that you had responded.

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Originally Posted by kimmosto View Post
Room acoustics [...] acoustic treatment targeting low and flat EDT is more final solution giving freedom to select speaker design and drivers by overall quality and preferred sound nuances - not just strong directivity.
That seems valid. I'd like a dedicated room. I currently rent a house with my GF, so there are lots of limits to what I can do with the room.

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Originally Posted by kimmosto View Post
Leaking cardioid bass is very flexible application, but also very ineffective sucking all power and excursion available. Bass unit with 2x18"
I'm using my 18" as midbass drivers. I'm not trying to EQ the leaky box for flat response to 30Hz.

When testing, the 18" has no visible excursion.

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I haven't done much diy designs since acoustics of our living room was improved.
Very interesting. Thank you for the info.
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