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Old 24th February 2013, 02:33 PM   #1371
guangui is offline guangui  Puerto Rico
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Originally Posted by KLBIrd View Post
The attached would be a real challenge to build in foam or any other material. It is from an article in Radio Craft Magazine in 1938. They call it an infinite baffle but it looks like a labyrinth and the sound path is over 30 feet long. The two 12" drivers are filed coil types.
Anybody game for this one?
Heard and seen the concept before, but how about taking it further, a single 5-1/4" woofer, and try to keep it compact by using the infinite baffle. Where could it lead? Could be the enclosure for my OB Hybrid bookshelf. I have been looking at the 5-1/4" Silver Flute for this. But, PE has a 6" Aura at Buyout cheap price, that I had discarded, as it needed a larger than what I want vented enclosure. Wonder if using the 6" in an infinite baffle enclosure will be compact enough for what I want.

As you can see, I would be game, but at a smaller scale.
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Old 24th February 2013, 02:41 PM   #1372
xrk971 is offline xrk971  United States
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What do you mean by OB hybrid bookshelf? I have been thinking of making a very low cost acoustical bandpass subwoofer with the NS6 buyout. It is a really efficient driver and in a 4th order bandpass reflex cabinet can provide a flat 40 hz to 100 hz at 87 db to 89 db efficiency with no xover needed. The design can be easily made in foam core: 24 liter back chamber with 7 liter front chamber with 2x2 inch x 8 inch long vent on front chamber. I sim'd it in WinISD. If you just need a sub, not sure if a horn or TL is needed unless you want really loud and low freq HT stuff. In which case a foam core tapped horn would be the thing to build. Lots of ideas for those in the subwoofer forum.
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Old 24th February 2013, 03:03 PM   #1373
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Quote:
Originally Posted by KLBIrd View Post
1938. They call it an infinite baffle
Is that because those drivers can't produce a wavelength that long so it qualifies as an OB?

Just askin'.
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Old 24th February 2013, 03:11 PM   #1374
xrk971 is offline xrk971  United States
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Originally Posted by Cal Weldon View Post
Is that because those drivers can't produce a wavelength that long so it qualifies as an OB?

Just askin'.
30 ft path is quarter wavelength of 9 Hz not too many drivers can hit that low of a frequency. It would sound like a big fat cicada buzzing away. 9 Hz is not even sound unless you like the rhythm of a jack hammer or machine gun.... thunk, thunk, think, thunk, thunk, thunk,....
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Old 24th February 2013, 03:18 PM   #1375
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After talking with Giau, I am getting itchy again. I am thinking this might be in order.
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Old 24th February 2013, 03:25 PM   #1376
xrk971 is offline xrk971  United States
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Cal,
That's a nice design. Unique, and I bet it will sound good too. What size driver were you thinking and how deep are the channels? I am currently side tracked onto making amps so i won't be making speakers for a while.
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Old 24th February 2013, 03:35 PM   #1377
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I use the CSS driver as the Fostex is back in the 27". This will be 30" at the points. I am thinking the channels that start at 1" width should be around 4" deep. What do you think?
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Old 24th February 2013, 05:26 PM   #1378
guangui is offline guangui  Puerto Rico
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Originally Posted by xrk971 View Post
What do you mean by OB hybrid bookshelf? I have been thinking of making a very low cost acoustical bandpass subwoofer with the NS6 buyout. It is a really efficient driver and in a 4th order bandpass reflex cabinet can provide a flat 40 hz to 100 hz at 87 db to 89 db efficiency with no xover needed. The design can be easily made in foam core: 24 liter back chamber with 7 liter front chamber with 2x2 inch x 8 inch long vent on front chamber. I sim'd it in WinISD. If you just need a sub, not sure if a horn or TL is needed unless you want really loud and low freq HT stuff. In which case a foam core tapped horn would be the thing to build. Lots of ideas for those in the subwoofer forum.
I call it "hybrid" for the lack of a better word. It is an Open Baffle on top of an enclosed woofer. Very common, but don't know the exact term for such an speaker. So, I call it a Hybrid OB.

The problem with the NS6 is that for the design I want, I would like to keep the woofer ported enclosure outside dims. to +/- 8" Wide x 9" High x 10" Deep. Then on top, place the baffle with a 3" Full Range driver (the good thing of having the enclosure is that, if needed, you can fold the baffle to increase baffle width, and still be within the desired W x D dims.), and add a tweeter, only if needed. The OB baffle will add about 5" to 6" to the final Height.

But, if by doing a horn or IB I can keep the desired enclosure dims, and get the lowest Hz I can get from the NS6, that would be awesome.
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Old 24th February 2013, 06:06 PM   #1379
xrk971 is offline xrk971  United States
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Guangui,
For the small cabinet you describe you may be better off buying a couple of computer monitor 2.1 speakers and use the sub cabinet and driver. The cabinet I have in mind for the 40 Hz to 100 Hz with the NS6 is about 27 in tall x 8 in wide x 12 in deep - kind of big but the performance you get is good. A very long folded transmission line might be able to fit in the dimensions you have to reach 40 Hz. You need about a 2.2 m pathlength to get to 40 Hz so the channel will probably spiral around like a Cornu but not be a horn - a tapered TL spiral that gets smaller at the port.
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Old 24th February 2013, 07:51 PM   #1380
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Another run around trying to find the foam but I finally found it. We are lucky that we seem to have a 1/2 dozen Dollarama's within a 30 minute drive.

Fronts and backs are double layered foam, offset to make 30" square, now gluing with the help of some 416's.

I will go to the repro place tomorrow to enlarge my drawing.
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