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Old 5th March 2013, 05:04 PM   #21
jReave is offline jReave  Canada
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AT,
I'm just afraid that your design is not going to be loud enough nor reach low enough for you.

I see you've already purchased the drivers. Have you already built your boxes?
And what are you planning to do to cover the lowest 2 octaves?
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Old 5th March 2013, 05:46 PM   #22
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Originally Posted by Kindhornman View Post
fatmarley,
They are actually fairly well behaved little speakers, the bottom end is a little light. I have some that I used as early prototypes for a speaker cone development that I cut out the cone and replaced it with a cone of my own design and they did sound better but you can't buy them so that is a moot point. I think that they were originally designed to be used in high end TV sets before flat panel designs made that impractical. They are so light they would make a nice portable two way system with the Audax I sighted earlier.
Interesting - Could I ask what material you used and how did it improve the sound?
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Old 5th March 2013, 06:40 PM   #23
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fatmarley,
The cone is a composite material that I developed. Doesn't exist anywhere else and is very different than any other composite cone on the market. The actually gained some bottom end as they did have a bit more mass and lowered the fs value and just were smoother than the original paper cone. I sill have a case of those speakers, some are modified and some still in the original condition. They are in my storage which I hope to get to soon.
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Old 5th March 2013, 07:35 PM   #24
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Originally Posted by Kindhornman View Post
fatmarley,
The cone is a composite material that I developed. Doesn't exist anywhere else and is very different than any other composite cone on the market. The actually gained some bottom end as they did have a bit more mass and lowered the fs value and just were smoother than the original paper cone. I sill have a case of those speakers, some are modified and some still in the original condition. They are in my storage which I hope to get to soon.

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Old 5th March 2013, 09:07 PM   #25
ATAUDIO is offline ATAUDIO  Austria
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Originally Posted by jReave View Post
AT,
I'm just afraid that your design is not going to be loud enough nor reach low enough for you.

I see you've already purchased the drivers. Have you already built your boxes?
And what are you planning to do to cover the lowest 2 octaves?
No, I did not build yet. I will, by the end of June, in my intentions. Still looking for the nice wood. At least for the external parts I would like to use a 9 mm Baltic birch multilayer, or a marine one (the latter is heavier, though). Maybe 12 mm only for the baffle. I will heavily brace everything . A complete skeleton, even with 1" stuff is less than 2 Kg. In the worst case, if power not enough, I can biamp, getting some 3 db more, or even get a 24V battery, going closer to 6dB, but getting probably too close to the drivers limit. Im better with electronics, than with boxes, I feel. Lower octaves, forget them. Too difficult outdoors, without a real , heavy sub.
What about my question on the ports? Large or deep?
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Old 5th March 2013, 09:16 PM   #26
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ATAUDIO.
Small ports have a tendency to chuff or make noticeable noises, like a whistle. You aren't going to have much port velocity with that speaker anyway but I would stay away from very small diameter or thin ports for that reason.
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Old 6th March 2013, 05:24 PM   #27
jReave is offline jReave  Canada
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Originally Posted by ATAUDIO View Post
No, I did not build yet. I will, by the end of June, in my intentions.
Good. The reason I asked was I would suggest adding an extra Aura in parallel to get +6dB with the same amount of power - they are pretty cheap. Actually, I'd like to tell you to scrap that mid and tweeter all together and just add a good cheap tweeter that will cross lower to the Auras (this would maximize your use of box volume) but since you've already purchased them, I won't. But I really, really want to tell you to do that.

So you'll need to double your box volume to add the extra NS6 and since weight and size are important factors to you, I suppose that won't work if you want to stay vented. But you can do it if you go sealed. And going sealed solves the most important problem with your design - the Aura very quickly runs out of excursion at LF's with very little power when it's ported. See the first graph below. That's at 98.5dB with 10W in 14L (you need to account for the volume of bracing, port and driver etc) and Fb=45Hz. With musical content below 35Hz (not at all unlikely), the cone has far exceeded its excursion limits. If we raise the SPL's just a little to 101dB with 18W, xmax is now exceeded between about 65-90Hz where all kinds of musical content lies (2nd graph). Serious problem for trying to fill any semi-large public spaces I think.

But if you go sealed with 2 Auras in somewhere between 15L and 20L, and use 10W for 104dB, cone excursion stays within limits - 3rd graph. Fourth graph is the FR with this alignment. F3 is 74Hz. Not great but not too bad either.

Notice that right now your total box volume plans are 15L + 9L = 24L, whereas by just using 2 Auras and a tweeter sealed, you can do it all in 20L. See now what I was getting at above?

Now if you can high pass the vented version at about 50Hz, then it's a slightly different story but you're still SPL limited with just the 1 driver.
Attached Images
File Type: gif VB Excursion Aura NS6 255-8A 10W.gif (21.1 KB, 87 views)
File Type: gif VB Excursion Aura NS6 255-8A 18W.gif (21.6 KB, 87 views)
File Type: gif CB Excursion Aura NS6x2 255-8A 10W.gif (19.1 KB, 89 views)
File Type: gif CB Response Aura NS6x2 255-8A 10W.gif (22.8 KB, 65 views)
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Old 6th March 2013, 05:37 PM   #28
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jReave,
Your analysis is right on and I second the opinion and have been trying to say the same thing about using a nice dome tweeter rather than a midrange which is not necessary with the Aura and I question if those two other devices are going to sound nearly as good as the Aura speaker would without the mid range crossover and a bullet tweeter that I have always found very objectionable. Double Aura's would be a much nicer implementation and they are fairly inexpensive. I think I only paid about $6.00 per unit when I bought them by the case. The other limitation of the Aura besides the excursion limit is the very small voicecoil and fine wire used. I have burned up a few playing with them but I didn't really care, I just threw those away and put in another. If with two he could accomplish a low frequency output down to 60hz that always gives the semblance of low bass and is a trick used by many commercial bookshelf speaker to sound like they have true bass tone.
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Old 6th March 2013, 07:22 PM   #29
jReave is offline jReave  Canada
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Originally Posted by Kindhornman View Post
If with two he could accomplish a low frequency output down to 60hz that always gives the semblance of low bass and is a trick used by many commercial bookshelf speaker to sound like they have true bass tone.
Thanks for the confirmation. I knew I was repeating what someone had already said but I couldn't remember who.

I was also thinking of suggesting some LF boost down around 60Hz but it was peaking instead around 150Hz in an smaller sealed box. I can get a nice 2-3dB peak centered around 68Hz or so but that's back to a vented design and in an even bigger box of about 30L per driver. Not suitable in this application unfortunately.
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Old 6th March 2013, 09:43 PM   #30
ATAUDIO is offline ATAUDIO  Austria
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Thanks again for the very informative post.
I understand that I have made many mistakes, but I do not see a solution now.
So vented not feasible at all if I am tearing the woofer with only 18 W.
I will not get any other Aura. It looks is a crap woofer for what you are telling me, and at a transport cost of 60 $ I can spend better my money next time.
Lesson learned.
Any good priced neodidium 8" available in EU?

That said, before scrapping the whole project and buy a ready made chinese boombox, I would try to understand if sealed is a possible solution. Why everybody in PA is convinced that vented boxes push more on bass?

Then I do not see why if the sealed box would work with 2 x crap Auras it wont work with the Aura + Celestion 5" Neo . That driver is only a couple of dB spl under the Aura and goes well up to 9K- I can make a removable baffle, so that would be my only risk at this point-I can scrap the bullets if they are really so bad, or cut them badly with a couple of Kohms and 2-5 uF.
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