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Multi-Way Conventional loudspeakers with crossovers

pattern control below 400Hz
pattern control below 400Hz
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Old 14th January 2019, 05:25 AM   #21
frangus is offline frangus  Australia
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I’m surprised by the patent; I thought Amphion did this earlier, with the circular pattern of perforations flanking the midwoofer?
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Old 14th January 2019, 06:43 AM   #22
ScottG is offline ScottG  United States
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Quote:
Originally Posted by frangus View Post
I’m surprised by the patent; I thought Amphion did this earlier..
..well, there's a patent, and then there is a defend-able patent.

My guess is that Geithain had this "down" before Amphion (..and likely someone before them from which it was derived).
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Last edited by ScottG; 14th January 2019 at 06:48 AM.
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Old 14th January 2019, 06:49 AM   #23
hollowboy is offline hollowboy  Australia
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Another good thread (one I saw a while back, but couldn't find again):
Leaky supercardioid mids
I'm seeing that that same midbass hump (like a badly tuned BR) where I've hacked a simple hole, and not added resistive material.
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Old 14th January 2019, 07:03 AM   #24
ScottG is offline ScottG  United States
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..here is a design and manufacturer that represent prior "art":

..it's a resistance-cardioid midrange:

Gradient Revolution loudspeaker | Stereophile.com
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Old 14th January 2019, 07:17 AM   #25
Juhazi is online now Juhazi  Finland
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I followed Keyser's thread with great interest then. The proto had 12" driver in a large perforated box combined with a 12" wide horn. I was pretty close to making woofer boxes like that or even better like kimmosto's KS-2125 But then I turned my head to Gradient 1.3 again. I like the lively sound of dipoles over studio-like precision and I don't have difficult reflections or modes in my room.

Cardioid has almost as poor efficiency as dipole in low register, that's why it must have large cone area and tolerate high power. D&D 8C has just a 8" cardioid mid and it suffers because it has to blow down to 100Hz, however loudspeaker's distortion is not easily an audible problem. Mitcho's measurement at audiosciencerewiev
Click the image to open in full size.

If one decides to diy a cardiod, be careful to find good model to copy, and still prepare to do lots of tuning and measuring to fit it with rest of the speaker.
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Old 14th January 2019, 10:10 AM   #26
cowanaudio is offline cowanaudio  Australia
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pattern control below 400Hz
Quote:
Originally Posted by hollowboy View Post

If the passive cardioid thing doesn't work for me (that is: if it requires a frustrating number of trials), my fallback position is to just package a nicer version of my prototype parts into simple towers - similar layout to this Lambda Unity Tower picture (from Cowan Audio website).

To me, this looks better than an Everest style box.
Thanks

You could make larger waveguides to get better low frequency pattern control. A bit of creativity and they can look really good.

A for Ara (@a.for.ara) • Instagram photos and videos

The grey ones are 1.5M across! They control their pattern much lower than my Unity horns.
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Old 15th January 2019, 02:16 AM   #27
hollowboy is offline hollowboy  Australia
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Quote:
Originally Posted by Juhazi View Post
I followed Keyser's thread with great interest then. The proto had 12" driver in a large perforated box combined with a 12" wide horn.
That's loosely what I'm interested in: a visually simple tower with woofer size roughly equal to horn size. A multi driver horn will allow a much lower crossover, though, so the midbass won't have to go up as high.

Quote:
Originally Posted by Juhazi View Post
Cardioid has almost as poor efficiency as dipole in low register, that's why it must have large cone area and tolerate high power.
Using this calculator
Piston Excursion calculator
I guesstimate a 18" (highpassed at 100Hz) with 3-6mm Xmax will hit its limits at roughly the same SPL as the components in my prototype horn.
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Originally Posted by Juhazi View Post
If one decides to diy a cardiod, be careful to find good model to copy, and still prepare to do lots of tuning and measuring to fit it with rest of the speaker.
I'm looking at something like the LF section of the KS-2125, but bandpasssed higher e.g. aiming for 100-400Hz rather than 20-220Hz.

Because I'll only need a couple of octaves, and am flexible about crossover points, I'm hoping it will be a relatively quick tuning process.

For my prototype, I'm trying light foam on the side wall perforations (some pretty chamfered holes are pictured, the other side has random shapes) and very dense stuff on the holes in the back wall (as yet untested). I'm guessing the lightly foamed holes will do almost all of the work / pattern shaping.

To keep the final version visually tidy, I think I will do something similar - I could do final tweaking by (internally) making some slots much more resistive than others. That seems like less work and mess than modifying the plywood shell.
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File Type: jpg perforated.jpg (217.0 KB, 160 views)
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Last edited by hollowboy; 15th January 2019 at 02:17 AM. Reason: picture didn't attach
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Old 15th January 2019, 03:40 AM   #28
hollowboy is offline hollowboy  Australia
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Originally Posted by cowanaudio View Post
Thanks
I showed my GF a gallery of possible build styles, and that was one that got the seal of approval. Large (to ~80cm wide) is OK, as long as the exterior is visually clean and not too industrial.

Quote:
Originally Posted by cowanaudio View Post
You could make larger waveguides to get better low frequency pattern control [...] They control their pattern much lower than my Unity horns.
I like some of those pictures, but my size & weight limits (I'll need to be able to pick them up) mean my horn sections will have roughly the same amount of pattern control as your Unity horns.

My prototype (60x36cm mouth) should be good for 400Hz / 750Hz. That's about as big as I'd like to go, cos going much wider than the woofer(s) seems like it gives diminishing returns, and because I'd like to allow enough extra width for roundovers.

These earlier projects (link and pic) show the sort of mouth transition + overall aesthetic I'm after. I'd like to skin the horn in bamboo, hence I'm trying to keep the horn angles simple & repeatable.

seeking rear mounted driver for front horn

Click the image to open in full size.
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Old 15th January 2019, 10:37 AM   #29
Brett is offline Brett
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Quote:
Originally Posted by hollowboy View Post
I showed my GF a gallery of possible build styles, and that was one that got the seal of approval. Large (to ~80cm wide) is OK, as long as the exterior is visually clean and not too industrial.
I'll be re-doing my Unitys later in the year as I was sick of the unfinished nailed together mdf boxes.
No real pics for design on this PC, but 45cm flat baffle with 15cm (ea side) 15* angled wings. Rear the same and just deep enough for the Unity. Drivers above and below are AE TD15S. Built in 3 boxes/side so I can actually lift them.
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Old 18th January 2019, 05:53 AM   #30
hollowboy is offline hollowboy  Australia
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Originally Posted by Brett View Post
Built in 3 boxes/side so I can actually lift them.
This is a concern
I did some outdoor testing, and hauling my boxes in & out of the house was not easy.

---

I'm using one sealed box (the pretty one pictured in post 28) as the baseline, and a less pretty but otherwise near-identical twin as the test mule. I'm happy to chop holes in the ugly box, because I want to reduce the weight before I re-skin it with a heavy layer of bamboo. That's exactly what I did to the pictured box.

As far as I know, the earlier "Resistance enclosure" threads didn't have (or didn't show) an identical sealed box to act as a baseline. Having this baseline is amusing / frustrating. The process often goes:

1) I record an off-axis plot for the "Resistance enclosure"
2) I congratulate myself, cos it looks like a pretty good weakening of rearward radiation
3) I then realise it is only slightly better than the sealed box

Other than that, I've mostly noted noted the same things as the earlier threads.

OLD INFO, REHASHED:

(1) Running 2x15" vs 1x15" made surprisingly little difference (outdoors). Only a narrow LF band gets the sensitivity gain. I've probably seen this info before, but it seems much more real now that I've measured it myself.

(2) The simple sealed box (48cm wide) has more directivity than I really understood. It is the same as the previous point - I've seen this info before (e.g. plots of the Geddes Loudspeakers NS15), but the effect seems more real now that I've measured it myself.

POSSIBLY NEW INFO:

(3) It looks to me like any hole in the back wall dominates the pattern you get ...so I think I see why Kimmo Saunisto and then keyser went with a solid back & perforated sides. I'm measuring a figure 8 (dipole-like) pattern, with big dips 90 degrees off axis, not the cardioid-like pattern that they report.

This figure 8 pattern persists even when the holes in my back wall are much more heavily damped than those in the side walls.

(4) Despite asymmetry in the side wall holes, I get essentially symmetrical response. I chopped one side wall further, to have about 2x the surface area open than the other ...and I still get symmetrical response. Not sure if this is always true, or if it is only true because of (3).

AND, THE PRACTICAL STUFF:

(5) Outdoors, the "standard" plots for the listening position (0 vs 30 degree off axis) look better for the "Resistance enclosure" than for the sealed box.

(6) Indoors, positioned near a corner, my "Resistance enclosure" is flatter on-axis than the sealed box.

These last two points are promising, and make me think it is worth persevering. The outsdoor off-axis measurements may seem underwhelming (not much better than the baseline box), but all that actually matters is whether there is a +ve effect at the listening position.
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