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Old 8th February 2013, 06:50 PM   #581
xrk971 is online now xrk971  United States
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The wire mesh grill threw me off there. Would you say the cornu presentation is like the speakers are bigger than they are (room filling) and the sweet spot is wider?
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Old 8th February 2013, 06:52 PM   #582
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Jim - could you be getting some cancellation / interference from the proximity of the inner facing mouths - maybe try them at least a couple of meters apart?
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Old 8th February 2013, 10:57 PM   #583
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X,
I think the imaging is less specific than with the Mets, but the sweet spot may be a bit larger-- if that makes any sense.

Chris,
I will try them in another position tomorrow: out from the wall and further apart.

Cheers, Jim
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Old 9th February 2013, 01:38 AM   #584
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Default gluing together the spiral sandwich

Quote:
Originally Posted by Cal Weldon View Post
Am I seeing that correctly, that the driver is mounted off center so there will be 6 different length horns? If so you certainly have all the bases covered with tuning frequency.

The foam joint tape - is that your spiral template? hehe, what, are you only building two of these?

As far as the glue drying, I would first install a 3/8" wide strip of paper to the cardboard edge with PVA glue, let it dry and then you will have a wider surface to put your glue on for the baffle piece.
Thank you Cal, you save my life! Had a crazy busy week and was not even back here on the thread. All 4 spirals are done and I will use your suggestion with the paper strip this weekend - excellent!
Originally I designed the drivers off center to get them closer together, because they are also separated wide by the fireplace. Off center they will be now about 2.5m or 8plus feet apart. Yes all 6 horns have different length and that will be an extra bonus I hope.
Yes I cut up some of my templates for joint tape. Made about a dozen of them in different sizes on the copy machine to help me design the real thing.

They have to be real good for me to build more than two. Was not all easy sailing to coax the spiral strips on their places.
Think I try single spiral ones next with 5 inch or 4 inch driver.
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Old 9th February 2013, 02:18 AM   #585
xrk971 is online now xrk971  United States
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Glowglass,
Can't wait to see your creation! Cal had a great suggestion there for the cardboard. You are right, that was super ambitious of you to try such an advanced design on your first cornu. But now, a simple 28 incher will seem like child's play
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Old 9th February 2013, 10:03 AM   #586
solhaga is offline solhaga  Sweden
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Great work Cal and X and all others!
A truly expiring thread together with the generic foam core thread.

I´ve built my first Cornu, 56x56 cm, with two 2" drivers.
Purely for proving the concept, but I was not so happy with the large excursions the little drivers were force to.

So now I´m thinking of what to do next.
First is to have a larger driver for the Cornu, maybe something that is laying around and then complement it with my 2" driver(s).
So to be able to fit the larger and deeper driver I thought of extending the compression chamber in z-direction towards the listener by 2".
Actually it will be a second front to the Cornu. In the space between the two fronts will be regular 2" thick foam with an cut out chamber for the driver.

So what about the 2":ers? Well, they will be mounted in the second front with their own outcarved boxes in the 2" foam.

A quick sketch:
Click the image to open in full size.
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Old 9th February 2013, 11:54 AM   #587
xrk971 is online now xrk971  United States
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Solhaga,
Sorry to hear about large excursions on the 2 inch driver, but 55 cm is probably too big of a horn to provide enough resistance (and loading) of driver diaphragm. What driver were you using? Neat idea about extending depth out to front to accommodate larger driver. You could just make a small box that goes over the central driver chamber rather than whole thing. What is larger driver you plan on using? If it doesn't fit make sure it is not too big, and you will have a case of too much resistance or loading. The drawing you show has a rectangular opening and object adobe round hole. Are you planning on pitting a ribbon tweeter there? Anyhow, great progress. Can you post pictures of your Cornu please?
Regards,
X
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Old 9th February 2013, 04:04 PM   #588
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Feb 9,2013

OK, so I moved the speakers off the wall over the mantel and down onto the floor and six feet apart (which I am sure is a big help). They now are on the long wall rather than the short wall of the room. WOW! what a difference. They sound so much more open and airy. Sound stage depth increased as well. Even my wife immediately commented on the improvement. The dip in the 100-125 Hz range improved slightly, but isn’t fixed. And there is now a bump at 200 Hz. The bump at 80 Hz went down (shift in room mode?), level at 63 Hz went down, and spl at 50 Hz went ip. Note that on the floor one of the horn mouths is blocked. Then I moved them up off the floor, which isn’t much of an improvement, except at 200 Hz.

Again I used the 1/3 octave warble tones on Stereophile test CD #1 to see what was happening. Here are the measurements, made with a Radio Shack meter.
Hz: dB on wall: dB on floor: up off floor:
1,000 68 68 69
200 72 77 73
160 74 73 71
125 64 66 57
100 64 65 61
80 75 71 68
63 73 69 64
50 61 64 61

So far, I still prefer the Mets, which I guess isn’t surprising, since I have built 4 pairs of them.

Cheers, Jim
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File Type: jpg cornu 108-2.jpg (46.3 KB, 354 views)
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Old 9th February 2013, 05:01 PM   #589
solhaga is offline solhaga  Sweden
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Thanks for you response X.

Yeah, I think I will go for a smaller Cornu for my 2":ers, and then perhaps just one. A larger Cornu will have to wait for a while.
They are the EAD E60s by the way, I got a surplus when I did my FAs.

Any suggestions for Cornu size?

My work so far with the Cornus turned out really shabby , perhaps there will be pics for the next one.

Last edited by solhaga; 9th February 2013 at 05:03 PM.
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Old 9th February 2013, 05:46 PM   #590
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by solhaga View Post
Thanks for you response X.

Yeah, I think I will go for a smaller Cornu for my 2":ers, and then perhaps just one. A larger Cornu will have to wait for a while.
They are the EAD E60s by the way, I got a surplus when I did my FAs.

Any suggestions for Cornu size?

My work so far with the Cornus turned out really shabby , perhaps there will be pics for the next one.
The E60 is a nice driver, I think Cal may have tried it. It should better than a 2 in driver I used from a Logitech computer speaker. I would go with a 14 to 16 inch cornu x 3 in to 3.25 in deep.

Good lick!
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