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Old 28th November 2012, 02:40 AM   #91
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dimensions are roughly (coz the laptop isnt with me right now) ~400x350 ish. and the speaker box could be up to 125mm tall if need be. any bigger it wont fit in the bag i carry it in. i already have the drivers, so id rather not let them waste... i have 4 of the 4inch ones, and 5 of the 3inch ones. (might be the other way round on item count, ill check it later)
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Old 28th November 2012, 03:10 AM   #92
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OK, I have done some practice run with 30" pieces at 4.5". It's not too hard to do. Your suggestion of putting the relief cuts on the inside of the curve was excellent. I managed to get some pretty tight corners even though I was near the end of the strip. One thing I can add at this point is to use even more cuts than suggested. On the tight corners spaced at 1/4" is not too many. Also, because the way an Olfa blade extends, the tiny little nib as you begin to extend the blade is all you need, and of course it prevents cutting to deep You sure don't have to be careful to do the lines perfectly parallel, I found you can just go to town and have 20 or 30 of those little slits in a flash. After that I used the rounded edge of my countertop to help shape it before gluing. All in all, very successful at this point. Hope I can get the repro people to do an enlargement of Sabastien's drawing for me tomorrow. That will make it super easy.

I would like to say thank to you directly but we don't know your name yet.
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Old 28th November 2012, 08:32 AM   #93
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Ok so turns out my laptop is 380x260 and the speakers i wanna use are 90mm. Turns out the bigger ones were Jvc. Numbers on the back are 6400FTTC01A and F30C-D323. 50w8r.

I have just had a play and mounted them into a roughly 1L cardboard box and they sound surprisinly good . if i decide to scale down my Pa sub bins (theyre an SS15)will that kinda work? Is it the horn path length what i need to adhere to or is there more to it than that?
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Old 28th November 2012, 09:43 AM   #94
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Quote:
Originally Posted by klampykixx View Post
Ok so turns out my laptop is 380x260 and the speakers i wanna use are 90mm. Turns out the bigger ones were Jvc. Numbers on the back are 6400FTTC01A and F30C-D323. 50w8r.
Quote:
Originally Posted by klampykixx View Post

I have just had a play and mounted them into a roughly 1L cardboard box and they sound surprisinly good . if i decide to scale down my Pa sub bins (theyre an SS15)will that kinda work? Is it the horn path length what i need to adhere to or is there more to it than that?
It would be helpful if you can get the Thiele/Small parameters for your drivers (Fs, Qts, and Xmax in particular). The dimensional constraints you give are really quite small for a TML or horn of any type. If you give 100 mm min width for the drivers, that leaves about 4 channels along the 260 mm direction for a total length of about 1.04 m. If you have a driver with a high Qts, you can mass load the tml (restrict the terminus) to push the low frequency down. Based on this, your requirements seem to indicate that the very popular and successful TABAQ TL design is the way to go. See my posts on that thread ( TABAQ TL for Tang Band ) and you will see ways to fold the path 3 dimensionally if needed, but I think a simple 4 channel fold should work. You can get down to about 55 Hz with the TABAQ. The problem is how do you fit more than one driver for stereo? One other thought if you like deep bass is to use a simple box enclosure with passive radiators to allow low frequencies to come out and mount both left and right drivers in common volume. This is how the Jawbone Jambox works.
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Old 28th November 2012, 09:56 AM   #95
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Originally Posted by Cal Weldon View Post
OK, I have done some practice run with 30" pieces at 4.5". It's not too hard to do. Your suggestion of putting the relief cuts on the inside of the curve was excellent. I managed to get some pretty tight corners even though I was near the end of the strip. One thing I can add at this point is to use even more cuts than suggested. On the tight corners spaced at 1/4" is not too many. Also, because the way an Olfa blade extends, the tiny little nib as you begin to extend the blade is all you need, and of course it prevents cutting to deep You sure don't have to be careful to do the lines perfectly parallel, I found you can just go to town and have 20 or 30 of those little slits in a flash. After that I used the rounded edge of my countertop to help shape it before gluing. All in all, very successful at this point. Hope I can get the repro people to do an enlargement of Sabastien's drawing for me tomorrow. That will make it super easy.

I would like to say thank to you directly but we don't know your name yet.
Cal,
You are well on your way, and I estimate only a day or two away from hearing the sound come out of your Cornu spiral. Well done with the cutting the channels en masse - that was a real time killer and drudgery for me. You are right about not having to be careful with the scoring the channels for bending. I was careful and used a ruler on the first few that are exposed so that they look neat but cheated and hand cut the rest that were internal as fast as I could to save time!
I look forward to your next update!
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Old 28th November 2012, 11:25 AM   #96
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Quote:
Originally Posted by klampykixx View Post
Ok so turns out my laptop is 380x260 and the speakers i wanna use are 90mm. Turns out the bigger ones were Jvc. Numbers on the back are 6400FTTC01A and F30C-D323. 50w8r.

I have just had a play and mounted them into a roughly 1L cardboard box and they sound surprisinly good . if i decide to scale down my Pa sub bins (theyre an SS15)will that kinda work? Is it the horn path length what i need to adhere to or is there more to it than that?
The dimensions you have actually are almost an exact fit (10 in x 15 in x 5 in) for the back loaded horn design on post 17. You still have the problem of what to do for the second channel? This design actually has very good loud bass, almost too much. Due to all the internal ribbing and channels, the enclosure feels very solid and can probably be toted around in a backpack. The Cornus on the other hand are much lighter and more fragile feeling.
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Old 28th November 2012, 12:53 PM   #97
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I have never tried to measure the power input to speakers before, I think if you have an O-scope you measure the rms voltage across the terminals. For 8 ohm speakers the voltage should be 2.83 V to be equal to 1 watt input correct? If you don't have an O-scope, can the AC voltage setting on a DMM be used? I think usually you want to drive the amp with 1 kHz which is where most specs are quoted. I want to do this on the Cornu horns to see how efficient they are because they sound awfully loud at a fairly modest amp setting even with a fairly inefficient driver like the Vifa TC9FD (84.5 dB at 2.83 V, 1 m, 1 kHz). I have to get a 1 kHz tone generator - maybe a program to do this from the computer? Is there a thread you guys can point me to get a newbie in measurements started? I will need a calibrated mic at some point but for now, I will use the old eardrums to say "This is pretty loud because I can't have a conversation with someone next to me".
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Old 28th November 2012, 02:53 PM   #98
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Cal,
You are well on your way
Thanks to you I am. I haven't picked up the plywood for the facers yet but I did try and experiment with using scrap piece and yellow glue. I had doubts about the bonding last night but not this morning. I just have one question that is bugging me. This is shown as 70 cm square. All the pictures I look at appear to be bigger as in 1 meter or even larger. Is this just a perspective thing?
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Old 28th November 2012, 03:48 PM   #99
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I think that is just fact that photos do not have something to compare. You can use the diameter of the 4 inch driver that they use as a reference. For my build, it is 20 inches square or 0.5 meter square (which is really 0.25 square meter). For a 0.7m square think baffle area is 0.5 square meter and I believe some sound energy radiates from the front baffle as I can feel it vibrate, perhaps this is acting as a passive radiator and could be reason why the speakers are quite loud at relatively low power levels. In effect the speaker cone may be much bigger than the "active" driver and approaches a 20 to 23 inch dia square woofer driver? The foamcore front panel may have more an effect of this than using plywood which is dense and heavy compared to the foamcore. An earlier poster mentioned that NXT drivers use foamcore flat panels for the "cones". I think we are not used to seeing such wide baffles in general. The foamcore bonds pretty well using white or even better, yellow aliphatic woodworking glue. Get your plywood and burn the mnidnight oil! Who needs sleep anyway?

Last edited by xrk971; 28th November 2012 at 04:00 PM.
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Old 28th November 2012, 05:58 PM   #100
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Quote:
Originally Posted by xrk971 View Post
I have never tried to measure the power input to speakers before, I think if you have an O-scope you measure the rms voltage across the terminals. For 8 ohm speakers the voltage should be 2.83 V to be equal to 1 watt input correct? If you don't have an O-scope, can the AC voltage setting on a DMM be used? I think usually you want to drive the amp with 1 kHz which is where most specs are quoted. I want to do this on the Cornu horns to see how efficient they are because they sound awfully loud at a fairly modest amp setting even with a fairly inefficient driver like the Vifa TC9FD (84.5 dB at 2.83 V, 1 m, 1 kHz). I have to get a 1 kHz tone generator - maybe a program to do this from the computer? Is there a thread you guys can point me to get a newbie in measurements started? I will need a calibrated mic at some point but for now, I will use the old eardrums to say "This is pretty loud because I can't have a conversation with someone next to me".
I stumbled across the "speaker voltage test' challenge ( A Test. How much Voltage (power) do your speakers need? ) that we often see in members' signatures. I think this is what I was looking for and plan to take this test. It will be interesting to see how efficient the Cornu spirals are.
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