LS3/5a mini monitor clones

[mondogenerator]

i have to agree that the 5/19 kit looks nice.

Joachim, or anyone else are more than welcome to comment or copy my visaton TQWT design. Many helped and contributed, and the xo is almost a copy of the vib130tl project on their site. As an aside, the visaton TL despite the 'old' methods of design is also worthy of note, and should be fantastic! Its not bookshelf though

[system7]

I thnik you're posting from your mobile phone again, mondo...

If you want some opinions from people on your Visaton AL130 "TQWT" aluminium woofer design, you need to post the link to avoid turning it into a huge homework question, which is: TQWT Visaton AL130 & G20SC Finished!





I've been looking into this BBC Birch Ply and Beech Fillets/battens idea. The BBC said that anything other than Beech was worse here. Seems Birch Ply (1300 rating Janka Scale) is a lot harder than softwood pine or fir ply (400 Janka Scale) that builders often use. Beech is an absorbent hardwood (Rated 1300 on Janka Scale) that is as hard as Oak, but has a very fine grain with good absorbtion and is the timber of choice for tough hardwood flooring. Ply has many forms suitable for boats, aircraft and furniture. Evidently a lot of its strength comes from the outer layers which are often a hardwood, and for some reason, odd number of laminates are preferred.

[ivanlukic]

Recommended reading:

Trevor Butler, A little legend - The BBC LS3/5a, HiFi News and Record Review, January 1989, pages 27-31.

Unfortunately I do not have scanner to post it.

[Colin]

I'm not sure if anyone has linked to this yet - the unofficial LS3/5a support site with a lot of information:

The Unofficial LS3/5A Support Site


If you go to the Library and Links page on that site, the Trevor Butler Little Legend article is also there.

[Colin]

More on the original design and specification in this PDF

http://www.g4dcv.co.uk/ls35a/pics/BB...me_service.pdf

[mondogenerator]

haha a free 'plug'! Yes mobile, either way i havent worked out how to post links! On topic tho, there is a wealth of info on the 'tribute' site. For what its worth, i have always used pine battens and thought them 'good enough', although almost anything is perhaps an improvement on pine.

[Colin]

Have a look at the original BBC Harwood research paper for the result of using pine battens.

[mondogenerator]

thanks Col i may read them again since i dont recall the results of pine battens. How exactly they would impact a 'not BBC not thin wall' construction i dont know. Whilst my box is ply and not uber thick, half of the volume is solid MDF. The only battening is to support the baffle.

[mondogenerator]

Speaking of the visaton drivers I have.....I hadnt considered trying to make a small monitor like the LS3/5A using the AL130.....

Im surprised to say that in Boxsim, (using the published values) it gives an F3 of ~90 Hz, so very similar to the 'real' LS3/5A, but in a volume of 5 litres, moderately stuffed.

This is what Boxsim, spits out:

http://static.diyaudio.com/forums/ga...okshelf-FR.jpg

and the crossover for a golden ratio dimensioned box, of 5 litre net volume.

http://static.diyaudio.com/forums/ga...okshelf-XO.jpg

Not too bad...
I think its fair to say the 'average' SPL is about 80 dB/W/m, so probably on par with the original.....

I may have to try it out!

[system7]

I was scratching my head over whether it is possible to use that Falcon Acoustics LS3-5A Kit with modern drivers. Apart form the Monacor SPH-135/AD and SPH-135TC Mid/Woofers, I haven't found ANYTHING that will fit.

You have a 121mm hole and 4 screws on a roughly 135mm diameter PDC. Tweeter rebate is 108mm. Problem is the beech battens only give you about 133mm width with mounting on the back of the baffle which scuppers your chances with the SB Acoustics polycone below. FWIW, the design uses 9-layer 12mm birch ply and 16mm beech battens, although the front panel is 9mm 7-layer birch ply. It does look possible to fit a different 12mm front baffle with a rebate. Especially with a small unit like the Visaton AL130 or W100S where the Vas works out OK even if it's not a polycone.

Timber is not something I knew a lot about. But Yellow Birch ply is vastly (X4) harder than floppy pine ply. Pinkish Beech battens are vastly (X4) more rigid than floppy pine battens too. Other choices for hardwood front baffle laminating and battens can be maple, used in guitar stems and violins, and surprisingly, Lime aka Linden aka basswood, which is used in the stems of bass guitars and is an ungrainy hardwood. Happens I tested some Lime for strength in 1987 in Holland Park, London, when "Lime Walk" all blew down one very windy night...



Lime is that stuff with the big green sticky leaves that dumps goo on your car if you foolishly park under it. Beech trees are interesting because they fuse branches with adjacent trees to produce a stronger structure. These are hardwood trees of the mature forest. Pine and Spruce and Fir adopt a more flexible strategy in exposed places as firstcomers. They BEND with the wind...

I would presume birch is quite bendy too, since it is a firstcomer in woodland too. Bottom line, is these BBC cabinets are a lot more rigid than I thought initially, and the hardness of the panels and battens seems to be quite well matched. I really don't know much about the equally important damping properties.