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Old 4th March 2012, 11:13 PM   #21
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Quote:
Originally Posted by mdocod View Post
I think that what Sreten was trying to tell you, in a more condensed and/or direct form is something like as follows:

The possible advantages of a very elaborate and complicated box design (like the B&W shell), are normally utilized for the very FINE tuning and reduction of a systems distortion characteristics. You seem to be approaching the project with the idea in mind that this "box design" makes up a major part of possible distortion issues. It does not. It's just a spoke in a very complex wheel. Moving that spoke over to your wheel does not keep your wheel round.
Indeed. Even the very simplest of square sided box constructions will have the ability to sound pretty amazing. Going to the extent of building a nautilus style enclosure is one way of getting say the last 5-10% of performance out of a design, providing the drivers are suitable. What this means is that some drivers will benefit more from elabourate cabinet work then others. These tend to be drivers with very thin cones that are more likely to allow reflected sound, within the box, back out through the cone.

The other factor is that you are able to adjust the crossover perfectly to suit the new box characteristics. If you cannot do this, then any of the benefits that the new cabinet will provide will be all for nothing. The frequency response and driver integration are the number one thing to get correct in any loudspeaker design. Botch it and the entire design is screwed, no box will save a bad crossover.

By the looks of things the ditton already uses a dome tweeter and dome midrange. Both of these drivers are already sealed and are completely unsuitable for nautilus loading unless you want to start dismantelling them.

As sreten has already pointed out, all you'd be doing is building a cabinet that looks visually similar to the Nautilus but without reaping any of its design benefits or technical merrits and on top of this destroying the environment in which the dittons crossover was originally designed to work.

From a technical point of view the answer is simple - don't do it.

If you're in it to learn, then there are far easier (and cheaper) things one can do to gain understanding whilst also doing something practical/fun.
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Old 4th March 2012, 11:31 PM   #22
mdocod is offline mdocod  United States
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@5th element

Indeed!
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Old 5th March 2012, 04:43 AM   #23
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thanks a lot for helping me and explaining to me the reasons of it, I really appreciate it, it's another learning to me. I will learn to walk before trying to run.. I was not ready for this project but I swear I'll make them one day(with a few mods)!
for the sealed tweeter and mids, I knew they were like this but the design was more developed for the bass drivers, the rest was more esthetics.
I really like the mini two way idea! less trouble and work, lower cost for just a project as this.. I think I will try it, but do someone knows if there are some (none-sealed) tweeter that would be great for this application and witch drivers should I take for it?
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Old 5th March 2012, 04:55 AM   #24
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Old 5th March 2012, 05:06 AM   #25
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Well , the air moved by the tweeter is so minimal in respect to what the woofer moves . What B&W does for the back wave of the tweeter is mostly philological with the other drivers .There are many tweeters with a little chamber behind the pole. The one that comes to mind is the B&G Neo3 ,which
is a different kind of technology , a planar one , and is available with a back cup ,but removable . But the size needed is no more than a cup of tea
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Old 5th March 2012, 05:43 AM   #26
nezbleu is offline nezbleu  Canada
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I don't understand the negativity here. Yoannblain, if you have the capability to make those funky cabinets (I certainly don't) I say "Go for it!" You have nothing to lose as long as you take care not to damage the Celestions (beauties BTW). I recognize that the project is non-trivial, and may not produce the best results for those drivers. But then I think that cabinet resonance and diffraction doom most "monkey-coffin" speakers no matter the drivers, and for that matter I also think that active crossovers solve a myriad of problems. You will have to learn a lot to do this, but isn't that what this hobby is about?

My only concern here is that you have 2 bass drivers and 2 passive radiators, and you want to use 4 woofers. This begs the obvious question, "What are the other 2 bass drivers and how will they work with the existing drivers?"

Other than that, your only mistake was posting here before you had a full plan or something built. As a result some folks here want to tell you why you are wrong to even want to try. If you are aware of the costs and challenges required to build this project, don't let others tell you not to bother.
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Old 5th March 2012, 05:02 PM   #27
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for the second woofer?..I will simply buy another identical pair from a guy, he's selling them for 90$ but I don't think I'll build them ow, I will start with the little ones, I saw some b&w 7 inch mid/woofer for 100$ new on canuckaudio! now I just need to find my tweeters,
there's something I didn't told about the 60 inch tall diy Nautilus, I will need to buy 20L of polyester resin to make the modeling paste for each speakers!! A 20 L can like this cost almost 200$ and that's not all! I need my fiber glass cloth, the woods, the aerosil powder to put in the resin to make the modeling paste, some cuted fiber to put in it and finnaly, some concrete for the base..+ 400 hours of work.. = proximately 7000$ if I consider I could work being paid instead.. that's a lot no??

so that's why I'll start with the small ones and if it gives great results I'll work hours and hours to conceive the perfect plan for the bigger ones and then I will build them!!
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Old 5th March 2012, 05:49 PM   #28
PChi is offline PChi  United Kingdom
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Just a note a caution. The Celestion 662 Loudspeakers were pretty good in their day. A friend had a pair but as with all speakers the drive units are fragile. Excessive volume will blow them up. He went through a number of tweeters, midrange units and even an Auxiliary Bass Radiator suspension.
It hasn't been possible to rebuild the units or get replacements for many years and all the units will be old.
I wouldn't build any cabinets without replacement drive units being available. Though I have some cabinets with Focal drive units that aren't available anymore but at least they are many years newer than the Celestions if it's the old floor standing 662s.
In my opinion money spent on decent drive units is money well spent. But I don't know what ones to suggest. SEAS possibly.
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Old 5th March 2012, 06:06 PM   #29
sreten is offline sreten  United Kingdom
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Hi,

The current 662 woofers are designed to work in combination with the ABR.

Adding a second woofer will mess up what integration you have with the mid.

You can sympathetically improve the 662's with some tweaks, recapping etc.

It may seem reading the Nautilus white paper that "the final frontier" has been
crossed. Not really. They just have a very expensive USP, unique selling point.
And TBH a relatively dubious one, rear wave control is not such an issue.
Its simply one design aspect taken to very unusual extremes, YMMV.

You'll find it hard to find a B&W bass/mid unit that isn't designed for vented
box loading and and likely won't suit a long tapered sealed line very well.
(The line in your sketch is quite short and heavily tapered, bass loading
would be effectively sealed in the low bass with that arrangement.)

Good design is about making the right decisions for a given cost / effort,
and a good speaker design is all about performance for the price / effort.

rgds, sreten.
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Old 5th March 2012, 08:32 PM   #30
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how can you say that my 662 woofer can't go in twin configuration if celestion did it with the ditton 88 ?? the 662 woofer is the same in the 66, 44, 66(version2) and the 88..
I suppose they're not only made for active + passive configuration.. no?
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