Ever think of building a Cornu Spiral horn? Now you can!

[xrk971]

Originally Posted by prezden

Here is another project in the works. I'm a little hesitant to post my effort so far. It looks pretty shabby compared to the ones by chaz and fenris

Prezden,
No worries man, I think they look great. It is not a big deal as it is all internal once the cover is on. The design is pretty forgiving as I have hand drawn my own spirals with drastic mods and both ,my builds manage to sound good. Thanks for sharing.

[chazdrumzalot]

Originally Posted by Cal Weldon

Nice work Chaz.

thanks!

I must say I am worried about you doing the stuffing and closing up the box unless you do as xrk suggests and make sure you can change it if you have to. If you over stuff it, you lose the value of this cabinet. I would do it at the end and make a cup shape for the chamber and use a fork if you want to add some to the throats. Stuffing makes more difference than almost any cabinet, so you have to get it right or you may miss the magic.

I think what I'm going to do is lightly stuff the first 1/3 of the line, approximately, in order to hopefully reduce peaks and dips. It won't be removable but at least I'll have done something. Frankly my more pressing concern is getting a good seal with the back of the box. I'll be using gorilla glue but I've never worked with it before; will I be able to put a bead along the foam board without getting a huge dripping mess? Any advice for this last step? Despite all the precautions I took in getting perfectly straight strips there is a lot of irregularity, which I assume is from the hot glue.

[prezden]

chaz- You might want to try LePage No More Nails. It bonds with around 10-15 sec. of holding and has 15min of working time.

[prezden]

Thanks Cal and xrk971 for your encouragement. The hard part now is waiting for the drivers to arrive from Solen.

[xrk971]

Chaz,
Your channels look like they will seal just fine. I am not sure why you say that the hot melt glue causes uneveness in channel height. I use hot melt glue to even out any height imperfections by laying thin bead on edges of channels before gluing with pva. We have heard G glue makes a mess, Fenris had good luck with caulking adhesive. You can always hot melt a piece of string to the teased out wad of stuffing and leave that hanging into driver chamber as emergency removal/adjustment recourse. When teasing out pillow stuffing, if you do not break it, just gluing string to end should move whole thing out in one piece.
Good luck with capping operation.

[Cal Weldon]

You can add damping near the mouth if needed but you can't take it away easily. Be careful not to overstuff. Mine has no stuffing in the horn itself, but the chamber is heavily damped.

[xrk971]

I am thinking out loud here... since we are looking for a driver with a very strong high frequency end, a low Qts, and high efficiency. What do you think of the Dayton PS108-8 (6.5 in) driver? It is 95 dB efficient and has HF peaks in the 105 dB region, a Qts of 0.23, and it will fit in a 36 in x 5 in deep Cornu which my estimates say will have a lower freq of about 30 Hz. This may be the ultimate Cornu design? We could make it thinner for some compression loading of the driver chamber if desired.

http://www.parts-express.com/pe/show...number=295-344

[chazdrumzalot]

Hey guys, just want to let you know that I've begun sealing my boxes. After cutting away the most egregious bumps, I decided to use some adhesive caulk which I had originally purchased for the job. Specifically I'm using Dap kwik seal. I lave LIGHTLY stuffed the beginning of the line, but don't freak out: I have a backup plan if I think it's overdamped (very unlikely, as my stuffing was pretty much transparent) which involves a vacuum cleaner.

WRT the "ultimate" cornu driver, keep in mind that as Qts drops, the need for a rising HF response diminishes because the bass will not be so exaggerated. (Speaking from the standpoint of someone who hasn't even heard the cornu yet; I'm going off of horn theory.) But of course, low Qts and rising response go hand in hand. That said, the Audio nirvana 6.5" cast frame might be a contender for a large, no-holds-barred cornu design. I'm still daydreaming of a 35" cornu for my tangband w5-1611s though.

[xrk971]

Chaz,
Yeah, that 1611s is a nice driver with moderate Qts so the bass should be pretty punchy. Good luck with the caulking and great idea with the vacuum cleaner for de-stuffing.

[prezden]

I'm wondering how small Cornu spiral could be made with reasonably good results.

Happy New Year All