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Old 12th September 2013, 03:49 PM   #991
xrk971 is offline xrk971  United States
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Fountek FE85 can probably work well with a 20 in Cornu, based on the Sd of 27 cm^2 the depth should by 2.7 in. So anything from 2.5 in to 3 in deep should work. Looks like a neat little driver that I would like to try one day. Good luck.
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Old 12th September 2013, 03:53 PM   #992
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Quote:
Originally Posted by Don Hills View Post
Whatever you were smoking out there, I want some.
hehe. That's years in the past my friend.
I can't blame you for thinking I'm exaggerating about the bass. I wouldn't believe me either.
Quote:
Originally Posted by Coen View Post
Well bigger might be better, but i guess my first pair will end up in my home office (2.5m x 3m) so 70x70 might be on the large side..
You remember these are wall mounted and there's only about a 5" protrusion from the wall?
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Old 15th September 2013, 01:45 PM   #993
Coen is offline Coen  Netherlands
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Well the drivers are here, now if only the foamboard would arrive. Anyhow gr8 reason to get the marantz down from the attic and try them out

Click the image to open in full size.
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Old 15th September 2013, 09:15 PM   #994
Vix is offline Vix  Yugoslavia
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Coen, it would be nice if you could make and post photos of work-in-progress of this one.
Me, I don't need another set of speakers at this time, (no space) but this one may be hard to ignore. I was just staring at a blank wall in my bedroom and thought "why not...."
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Old 15th September 2013, 10:21 PM   #995
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Do it Vix.
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Old 16th September 2013, 02:33 AM   #996
Dave R is offline Dave R  United States
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Quote:
Originally Posted by xrk971 View Post
Dave,
The 3 in Aura's as I recall work really well from what Cal and his BIL did. The TB 1772 is an 8 incher and that will be a HUGE Cornu - we are talking 15 to 17 square feet of baffle! You can make it smaller by designing your own custom channels, but if you simply scale the basic plan (which was designed for a 4.5 in driver) you will get a 50 inch x 50 inch or 17 square foot baffle Cornu! 48 in can probably work and that will fit exactly a front and back panel for a single sheet of plywood. Doesn't have to be thick plywood, probably 1/4 in is sufficient. Let me know if you are serious and I can run a sim with the venerable W8-1772 for you to fine tune the channel depth and throat openings.
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X
Hi xrk971,

If memory serves me, horn loading has been reported to work best for drivers with Qts ~ .30 or so. However, from what I gather here, this configuration is somewhat forgiving for a wide variety of Qts values.

With that in mind, I found another possibility in my stash. It's a 4" with a phase plug. Haven't had time to measure FR yet, but I do have T/S parameters. Could this driver with Qts = 1.02 still yield a reasonable response?

T/S for nominal 4"
------------------
Fs = 89.5 hz
SPL = 83.4 dB
Sd = 52 cm^2
Vas = 2.7 liters
Mms = 4.6 g
DCR = 6.7 ohm
Le = 1.14 mH (@ 1kHz)
BL = 3.62 T-m
Qes = 1.34
Qms = 4.30
Qts = 1.02
Xmax = 3 mm

I don't currently have T/S on the Aura 3" that I have, but the Qts was closer to 2.0, IIRC.
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Old 16th September 2013, 01:19 PM   #997
xrk971 is offline xrk971  United States
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Default Sim of Cornu with mystery 4 inch high Qts driver

Quote:
Originally Posted by Dave R View Post
Hi xrk971,
With that in mind, I found another possibility in my stash. It's a 4" with a phase plug. Haven't had time to measure FR yet, but I do have T/S parameters. Could this driver with Qts = 1.02 still yield a reasonable response?
DaveR,
You are lucky - this driver seems to work quite well in a Cornu. Below is a simulation for a 27 inch x 4.5 inch deep Cornu mounted at 45 in above the floor (centerline of driver). Use moderate stuffing in the driver chamber and the first 40% of the channel leading from the chamber to the channel split point. It has a very flat bass shelf with about 10 to12 dB of gain from the nominal 83 dB efficient driver. The bass extends down to 50 Hz which es excellent, and like all Cornu's suffers from a few peaks in the mids, particularly at 230 Hz. Adjusting the stuffing at the mouth to taste can balance the bass out to be more in line with the 80 dB output in the HF's. You really should use a much more efficient driver in order to get a good balance between the bass and highs.

I would go for it and build this! Good luck!

SPL vs Freq with no stuffing

Click the image to open in full size.

SPL vs Freq with stuffing in chamber and first 40% of channel leading to split

Click the image to open in full size.

Impedance

Click the image to open in full size.

Cone Excursion

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Impulse Response

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Attached Images
File Type: png Cornu-27x4p5-4inch-Freq-1m-no-stuffing.png (19.2 KB, 308 views)
File Type: png Cornu-27x4p5-4inch-Freq-1m.png (26.4 KB, 305 views)
File Type: png Cornu-27x4p5-4inch-Impedance.png (21.5 KB, 304 views)
File Type: png Cornu-27x4p5-4inch-Displ.png (20.9 KB, 304 views)
File Type: png Cornu-27x4p5-4inch-Impulse.png (14.2 KB, 303 views)
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Old 16th September 2013, 01:28 PM   #998
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by Cal Weldon View Post
I tried 6 different 3" drivers and it was a tie between a salvaged JVC and a salvaged LG. No comparison between the 3's and the 4.5. Go with the largest you can.

When it was placed outside recently, the bass made us all giggle like children.

Here is what I think the bass might look like if placed near a wall. 27.5 x 5.5 inch Cornu with FF125WK.
Attached Images
File Type: png Cornu-27p5x5p5-FF125WK-Freq-1m.png (17.3 KB, 799 views)
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Old 16th September 2013, 01:41 PM   #999
Dave R is offline Dave R  United States
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Quote:
Originally Posted by xrk971 View Post
DaveR,
You are lucky - this driver seems to work quite well in a Cornu. Below is a simulation for a 27 inch x 4.5 inch deep Cornu mounted at 45 in above the floor (centerline of driver). Use moderate stuffing in the driver chamber and the first 40% of the channel leading from the chamber to the channel split point. It has a very flat bass shelf with about 10 to12 dB of gain from the nominal 83 dB efficient driver. The bass extends down to 50 Hz which es excellent, and like all Cornu's suffers from a few peaks in the mids, particularly at 230 Hz. Adjusting the stuffing at the mouth to taste can balance the bass out to be more in line with the 80 dB output in the HF's. You really should use a much more efficient driver in order to get a good balance between the bass and highs.

I would go for it and build this! Good luck!

[/IMG]
Wow! Wasn't expecting all of that. Much appreciated. Almost forgot that I had these. They are packaged with Tang Band, and "hand-marked" as W4-1806S (shielded). Got them from Bob at CSS a while back, and have been trying to find a good use for them. This sounds like a great fit.

Now it's back to Santa's workshop -- get those little elves busy! ;^)
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Old 16th September 2013, 03:38 PM   #1000
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Hey Dave, you big lug. So glad you're joining the foam gang.
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