Thanks for the knife tip. I do have one sheetrock knife you can extend the blade out increments so that should prevent cutting all the way through.
Yes i figured for 4 bucks a sheet i can experiment with the design and if it turns out good then I can build a set of the full scale ones. I'll have to buy 2 full 4' by 8' sheets for that project.
I saw the cornu version with gentleman the used monacor sp-50x drivers. WOW is all I can say.
I used a set of those just in a set of micro towers for my budget basement system and I'm very impressed with them. I can imagine they sound quite will in the cornu horn
Yes i figured for 4 bucks a sheet i can experiment with the design and if it turns out good then I can build a set of the full scale ones. I'll have to buy 2 full 4' by 8' sheets for that project.
I saw the cornu version with gentleman the used monacor sp-50x drivers. WOW is all I can say.
I used a set of those just in a set of micro towers for my budget basement system and I'm very impressed with them. I can imagine they sound quite will in the cornu horn
Your epiphany is not for every man it seems. I tried it with a number of tools.
Table saw - really fast but jagged edges
Hand saw - slower but still fast, slightly less jagged edges
Tin snips - slow, crushed the edge
Chef's knife - a little faster but hard to control
Serrated bread type knife - what was I thinking? The noise it made was as bad as nails on a chalkboard
Straight blade (drywall) - good but couldn't do the scoring
Hook blade (roofing) - another dumb idea
Olfa knife (box cutter) - the only practical means I tried
I thought I had the cat by the tail by bundling and cutting it on the table saw. Took less than 2 minutes to cut all the pieces for the 80 cm horn but the blade was chunking out the foam because it got hot enough to melt the polystyrene and pieces ended up stuck to the carbide tips. It was a ***** to clean until I took a piece of wood and ran it through. Cleaned it up right nice.
Table saw - really fast but jagged edges
Hand saw - slower but still fast, slightly less jagged edges
Tin snips - slow, crushed the edge
Chef's knife - a little faster but hard to control
Serrated bread type knife - what was I thinking? The noise it made was as bad as nails on a chalkboard
Straight blade (drywall) - good but couldn't do the scoring
Hook blade (roofing) - another dumb idea
Olfa knife (box cutter) - the only practical means I tried
I thought I had the cat by the tail by bundling and cutting it on the table saw. Took less than 2 minutes to cut all the pieces for the 80 cm horn but the blade was chunking out the foam because it got hot enough to melt the polystyrene and pieces ended up stuck to the carbide tips. It was a ***** to clean until I took a piece of wood and ran it through. Cleaned it up right nice.
This is my favorite blade that I use for all builds in foam core. You can sharpen it on ceramic stone to extend life by quite a bit.
#11 Classic Fine Point Knife Blades | X-ACTO
I use the basic #1 precision knife.
The Original #1 Precision Knife | X-ACTO
Gives very clean edges and straight or curved cuts.
You can see the quality of the cuts this knife makes here:
#11 Classic Fine Point Knife Blades | X-ACTO
I use the basic #1 precision knife.
The Original #1 Precision Knife | X-ACTO
Gives very clean edges and straight or curved cuts.
You can see the quality of the cuts this knife makes here:
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I just realized something and it makes me sad. I have finished with these for the time being so they have to go away. There's no room here, no place to put these and I already have the systems I need, so these will be going to my other place, down into the speaker room. Ordinarily this doesn't bother me but this seems different. Our friend XRK has brought a new approach to this hobby of ours and, as I've said before, I enjoyed the whole process behind these, from start to finish, including sharing it with you guys. I have to admit, there's a hollow spot in my heart right now.
The only good thing is the speakers are going to where there are lots of others just like them. They will be with friends. It's like taking your dog to a kennel. Still there's a little twitch somewhere inside that I can't seem to get rid of. Damn you X, what the hell did you do to me?
The only good thing is the speakers are going to where there are lots of others just like them. They will be with friends. It's like taking your dog to a kennel. Still there's a little twitch somewhere inside that I can't seem to get rid of. Damn you X, what the hell did you do to me?
Homes for Wayward Cornus
So what to do with my initial experiments? I ordered a Lepai 2020A Class T amp thru Amazon for $19 and will provide the speakers and amp to a couple of VISTA/AmeriCorps volunteers who work for me for very little money and are stuck with a stupid boombox for music. I think this setup is going to blow their young minds!
Last weekend I finished my Tang Band Buyout 20" Cornus using the true four horn spirals. I've been enjoying them all week, but on Friday I'm getting the Aurosound NS3's that someone (Cal?) recommended. I'm planning on a set that will meet the WAF to stay in the living room.Such an empty feeling.
So what to do with my initial experiments? I ordered a Lepai 2020A Class T amp thru Amazon for $19 and will provide the speakers and amp to a couple of VISTA/AmeriCorps volunteers who work for me for very little money and are stuck with a stupid boombox for music. I think this setup is going to blow their young minds!
Jsouder,
That's a great thing to give the Americorps volunteers. It will blow their minds, I can't imagine what my music listening would be now if I had experienced this in my 20's. When you say you built a true four horn spiral, which plan are you referring to? When I say "true Cornu" I am referring to the true Cornu function which has rather narrow channels near the throat. I was not sure if anyone actually tried to make that.
That's a great thing to give the Americorps volunteers. It will blow their minds, I can't imagine what my music listening would be now if I had experienced this in my 20's. When you say you built a true four horn spiral, which plan are you referring to? When I say "true Cornu" I am referring to the true Cornu function which has rather narrow channels near the throat. I was not sure if anyone actually tried to make that.
6 Sided True Cornu Function BLH Plan in pdf
Jsouder,
Here is the plan in pdf. Note that this is a yet untested, not-yet modeled plan so use at your own risk. It is 28 in in dia and 4.5 in to 5 in deep, I would go with a 3 to 3.5 in class driver - not enough room or throat for a bigger driver. Probably best to use thin cardboard stock on inner sections where spacing is narrow.
Jsouder,
Here is the plan in pdf. Note that this is a yet untested, not-yet modeled plan so use at your own risk. It is 28 in in dia and 4.5 in to 5 in deep, I would go with a 3 to 3.5 in class driver - not enough room or throat for a bigger driver. Probably best to use thin cardboard stock on inner sections where spacing is narrow.
Attachments
So the 28” (5” channel) Cornucopya produced less than amazing results with the geriatric Altec 405A drivers.
Mr. X asked if anyone has a pair of FE108eSigma drivers. I do. Used them in my first Metronome build, and I like those Mets very much. But they were the first build of my later years, and while the cabinets are fine acoustically, they are cosmetically challenged. So I pulled the 108s, made adaptor rings, and put them into the Cornu horns. See photo below.
The result is way better than the poor old 405As. Bass is acceptable, highs are a bit too hot, presentation is interesting. I tamed the highs (mostly) with the treble control on the Sansui 4000 receiver. (Note that I use BSC on the Mets.) But there is something wrong between the bass and the mids.
I used the 1/3 octave warble tones on Stereophile test CD #1 to see what was happening. Here are the measurements at a distance of 8’ from the speakers, made with a Radio Shack meter.
Hz: dB:
1,000 68
200 72
160 74
125 64
100 64
80 75
63 73
50 61
I’m not surprised by the bump at 80 Hz, as it is (I believe) a room mode. The drop in the 100-125 region puzzles me. I also hoped for lower bass extension. I may try them in another position or room to see if they can do better.
Cheers, Jim
Mr. X asked if anyone has a pair of FE108eSigma drivers. I do. Used them in my first Metronome build, and I like those Mets very much. But they were the first build of my later years, and while the cabinets are fine acoustically, they are cosmetically challenged. So I pulled the 108s, made adaptor rings, and put them into the Cornu horns. See photo below.
The result is way better than the poor old 405As. Bass is acceptable, highs are a bit too hot, presentation is interesting. I tamed the highs (mostly) with the treble control on the Sansui 4000 receiver. (Note that I use BSC on the Mets.) But there is something wrong between the bass and the mids.
I used the 1/3 octave warble tones on Stereophile test CD #1 to see what was happening. Here are the measurements at a distance of 8’ from the speakers, made with a Radio Shack meter.
Hz: dB:
1,000 68
200 72
160 74
125 64
100 64
80 75
63 73
50 61
I’m not surprised by the bump at 80 Hz, as it is (I believe) a room mode. The drop in the 100-125 region puzzles me. I also hoped for lower bass extension. I may try them in another position or room to see if they can do better.
Cheers, Jim
Attachments
Jim,
Thanks for making those measurements and sharing with us. That's a neat way of getting a frequency response. I think the dip at 100-125 Hz may just be cancellation from horn plus front driver, try moving forward or back a few feet and see if it goes away. Glad the FE Sigmas are working out better than your Altecs though. Since you built a 28 in x 5 in Cornu, and you are running it with the FE Sigma you have the closest approximation of what the commercial Cornu sounds like. I am not sure if having a middle divider will change the sound a lot? If you are interested in doing more measurements, try getting the Panasonic WM61A capsule for $2 ea from Digikey. They are flat from 20 to 20 kHz and Holmimpulse even has a calibration curve for them. Are your photos showing the FE108Sigmas?
Regards,
X
Thanks for making those measurements and sharing with us. That's a neat way of getting a frequency response. I think the dip at 100-125 Hz may just be cancellation from horn plus front driver, try moving forward or back a few feet and see if it goes away. Glad the FE Sigmas are working out better than your Altecs though. Since you built a 28 in x 5 in Cornu, and you are running it with the FE Sigma you have the closest approximation of what the commercial Cornu sounds like. I am not sure if having a middle divider will change the sound a lot? If you are interested in doing more measurements, try getting the Panasonic WM61A capsule for $2 ea from Digikey. They are flat from 20 to 20 kHz and Holmimpulse even has a calibration curve for them. Are your photos showing the FE108Sigmas?
Regards,
X
Hi X,
Yes, the Cornus in the photo are with the FE108eS installed. Close-up attached shows the adaptor ring.
I will try playing with placement to see if the 100-125 Hz dip will go away. The ‘hot’ high end is just the character of the 108, which apparently gets fixed with the BSC in the Mets: 1 mH inductor in parallel with a 4.5 ohm resistor. In the Met, the 108 is bright and detailed, but I don’t find it fatiguing. Of course, YMMV. The Met also goes lower, with useful in-room response down to about 40 Hz--not bass monsters, but in jazz recordings the double bass sounds pretty good to me.
The sonic presentation of the Cornu is rather different from the Met, but I don’t know how to explain it.
Cheers, Jim
Yes, the Cornus in the photo are with the FE108eS installed. Close-up attached shows the adaptor ring.
I will try playing with placement to see if the 100-125 Hz dip will go away. The ‘hot’ high end is just the character of the 108, which apparently gets fixed with the BSC in the Mets: 1 mH inductor in parallel with a 4.5 ohm resistor. In the Met, the 108 is bright and detailed, but I don’t find it fatiguing. Of course, YMMV. The Met also goes lower, with useful in-room response down to about 40 Hz--not bass monsters, but in jazz recordings the double bass sounds pretty good to me.
The sonic presentation of the Cornu is rather different from the Met, but I don’t know how to explain it.
Cheers, Jim
