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-   -   curved enclosures/standing waves (http://www.diyaudio.com/forums/multi-way/18349-curved-enclosures-standing-waves.html)

RobWells 29th July 2003 04:29 PM

curved enclosures/standing waves
 
Hi Guy's

As theres been a few of the "layered" type of curved enclosures mentioned recently, I thought I'd bring up the parrallel top and bottom of the enclosure.

I've decided to make my mid/tweet enclosure the same as my bass units ( http://www.diyaudio.com/forums/showt...&pagenumber=10 )

However, though the curved sides are meant to reduce the standing waves, the parrallel top and bottom will still be a problem.

I'm thinking of using lengths of 1"x1" timber, cut with a 45 degree at the top, which start of 1" long near the front of the box, and end up 4" long at the rear. Also I'd rotate the tops so there is no straight bevel across the width.

Did any of that make sense?:o I wish I had a scanner here.

I don't know if anyone has tried this, but I 'feel' (?) it could be effective.

Cheers

Rob

RobWells 29th July 2003 05:09 PM

2 Attachment(s)
Like this, getting higher to back of box..:

:)

GM 29th July 2003 05:52 PM

If it's a sealed design, then this is a good plan anytime you move much beyond a golden ratio cab, but for vented, it's normally best to leave them parallel to get more pipe action. Tapering the end of a long vented design creates the equivalent of a massive amount of stuffing as the air 'spring' increases through loading, IOW think of it as the increasing pressure of a horn's throat. Also, this effect shifts the optimum driver location down the pipe depending on the amount of taper.

GM

RobWells 29th July 2003 06:11 PM

Hi GM,

Yep it's sealed. The approx (rough sketch on paper) dimensions are 25cm wide, 35cm high, and enough depth to make the teardrops' internal vol =11L (+ the vol of the bits of wood!)

I forgot to say that this treatment would be to the top and bottom of the cab.

Cheers

Rob

THOR509 30th July 2003 01:49 PM

a sugestion
 
I have been expiermenting with low difraction/low resonate, low standing wave enclosures since 1977! Ive tried spheres, (bad)tapered ends, curved, prisms, eggs, tubes, tubes with spherical ends, lead tubes:) and a few more i cant renember. The pic of the litter and by far the best, is the egg, with the driver mounted in the large end . After laboriously making them of F glassed styrofoam, laid up F glass,cast plaster, laminated wood, i finally got smart:) Iwas in the garden dept of home despot and spied some urn shaped flower pots that are shaped like the back 3/4s of an egg! they are made of hi fired Chinese porcelain and when lined with soft exlanded vinyl lino or felt bonded in with liquid nails are completely inert! I bond on a 3 layer front baffel curved inside and out to complete the large end of the egg, stuff them with wool , mount the speaker and its done ! they sound gorgeous! The pots are called "Kona" and are quite pretty.. they are avail in 3, 5, 8, 12, and 16 L volumes . the curved fromt adds volume as well . try them, and i dont think you will ever go back to vibrateing wood :)

RobWells 30th July 2003 07:33 PM

Wow!,

They sound interesting. Any pics?

We don't have home depot in the UK, but I'm sure theres similar stuff available.

Cheers

Rob

Vikash 30th July 2003 08:47 PM

Yeah I'd love to see some pics too.

All my research on diffr/sw leads me to the egg as well, not forgetting the aesthetic pluses, but I just can't see how I can form my design.

I 'm always on the look-out for egg-shaped objects that can be used as an enclosure. I saw a brilliant giant egg shaped porelain vase in camden recently, but it was rediculously priced.

Another problem when using the end of the egg as a baffle (I'd have it not other way) means you can't easily point a tweeter in the same direction. And of course you want it close to the other driver so a seperate enclosure is not ideal. Perhaps I don't need to contain the rear of the tweeter in the egg. Hmmm. Ok enough waffling...

Andy G 31st July 2003 01:52 PM

Vicash...
 
... there is no reason that an egg shape cannot be made using the "turned tramslam" method.

section 2 on this page

http://users.tpg.com.au/users/gradds...udspeakers.htm

you will see that both speaker there are not really that far off egg shaped

THOR509 1st August 2003 02:28 AM

pics and etc:)
 
unfortunately i sufered a crash (AGAIN! DAM WINDOWS!) and lost the pics bui will try and borrow a dig camera in the next few days and post them here if i can find out how:) Otherwise i will e mail to those interested. Turned layered cabs are not in the equasion with ceramic pots when it comes to ease of construction . Did it when i had my lathe and its not worth the labor intensive process . Bond a baffel on a pot radious it (i use a disk sander and a rasp on the outside ), line the pot and ur done :) The speakers i will photograph have a single layer baffel radioused on the edge , but not the equal of a 3 layer with big R inside and out (but great sounding ) I wont build any more with a single layer. These have Jordan JX 92S FR drivers over subs ,all sealed enclosures and are fab ! Three layer are just that touch smoother and better, ill add 2 more layers to these. To mount a tweet just counter bore a flat as close to the MR as desired , screw it on and make a "cocoon"for it of felt . u still get the major bennefits of the egg every where else. I did this on several sets before i got hooked on FR drivers! Next set will be the Fostex FE 167E in a sealed 12L pot , again over my sealed DIY HSU 1202 bi amped subs.


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