Please help this newbie out!

[vjcritic]

I have been a longtime lurker over here and I have finally decided to embark on my first DIY loudspeaker project. I have set my sights on the recommended Bass Reflex for FOSTEX 127E. It is a 10Litre box with 50mmX80mm port. I selected this design because of its simplicity and size. After some playing around with WinISD and some thinking I have come up with these questions. Any help is greatly appreciated. I did search the forums extensively before posting. I couldn't get some definite answers.

1. Should I use lining on the inside of the box. If so what should I use? Should I use filling?

2. If I use the dimensions for the box as specified in the FE 127E spec should I account for the volume of the driver magnet. After initial calculations I get the volume to be around .3Litres. Should I change the dimensions of the box because of this?

3. Do I need bracing for this box (10L ). If I do use bracing, how should I brace and should I change the dimensions to account for the bracing volume?

Here is a link for the enclosure design. The one on the bottom right corner.
http://www.fostexinternational.com/d...7e_enclrev.pdf

Thanks!

[chrisb]

For a relatively simple, rectangular box, please consider the "GR" version of this series ( fifth set of drawings from the top) :

http://www.planet10-hifi.com/fonken.html

[Scottmoose]

Yes indeed. Chris speaks words of wisdom: the GR fonken box he links to will blow the Fostex BR cabinet out of the water in terms of quality, and will keep the driver under much better control. There are quite a few other designs lurking around for the 127, of varying difficulty (though none are very hard), which will give better performance than either of the Fostex cabinets. Have a look at these alternatives too, also on Dave's site: http://www.planet10-hifi.com/boxes-fostex.html

Oddly enough, I've just completed the designs for 3 new boxes for the 127, which are about as simple as it gets. Drawings should appear soon, when Dave has time to fire up his CAD software, in between stints of paying work!

If you're set on the Fostex box though, then you won't need to line all of it. I'd do the rear panel, from the top to just below the driver, the top, and one side-wall. That should be quite sufficient. Carpet underlay is a good, cheap material to use. I wouldn't bother to make any adjustments to the dimensions of this cabinet -it's a bit of a compromise, so the differences will be minor. Bracing a small cabinet isn't strictly necessary, but usually worth doing. In this case, if you use a good plywood, a couple of hardwood dowel-rods across the width should do, and another one bracing the rear of the magnet to the inside of the rear panel, which will cut down on box-noise dramatically.

Hope that helps
Scott

[chrisb]

Originally posted by Scottmoose


Oddly enough, I've just completed the designs for 3 new boxes for the 127, which are about as simple as it gets. Drawings should appear soon, when Dave has time to fire up his CAD software, in between stints of paying work!

Scott

Great; just when I thought I'd have time to finish his kitchen before next month end, you throw this at us. Oops, that was 'spossed to be a surprise - but then again, maybe that means the floor will get repaired in time to install.

Maybe you could take up knitting for a few weeks?

cheers


BTW, without blowing my own horn too much, may I say that I've probably built and extensively listened to more of the multitude of enclosure designs posted on Dave's site than a lot of folks.

In my temporarily not so humble opinion, of all these FE127E designs, including several varieties of bi-poles, the Fonken exhibits the most finesse and overall disappearing act. Nothing's perfect, but these are a pretty decent compromise - within their excursion limits, it's quite amazing the bass "authority" of which this driver is capable.

[Scottmoose]

Did I say 3? Sorry, I meant 4. I forget to mention the versions for the 167 & 207 as well. Oops...

OK, I promise. No more new box designs for a while... although that's probably just giving me time to dream up something really far-out...

[chrisb]

Originally posted by Scottmoose
Did I say 3? Sorry, I meant 4. I forget to mention the versions for the 167 & 207 as well. Oops...

OK, I promise. No more new box designs for a while... although that's probably just giving me time to dream up something really far-out...

Just hold back 'til August, OK

[vjcritic]

Thanks for your replies guys.

Originally posted by Scottmoose
Oddly enough, I've just completed the designs for 3 new boxes for the 127, which are about as simple as it gets. Drawings should appear soon, when Dave has time to fire up his CAD software, in between stints of paying work!

I can wait I haven't finalized on any design. All I have to lose is a pair of port pipes I bought from Amazon

Originally posted by Scottmoose
and another one bracing the rear of the magnet to the inside of the rear panel, which will cut down on box-noise dramatically.

So this will be a piece of wood connecting the back of the driver and rear inside wall of the speaker? Am I getting the picture? How can I attach the wood to the back of the driver?

Thanks Again.

[chrisb]

Originally posted by vjcritic
Thanks for your replies guys.



I can wait I haven't finalized on any design. All I have to lose is a pair of port pipes I bought from Amazon



So this will be a piece of wood connecting the back of the driver and rear inside wall of the speaker? Am I getting the picture? How can I attach the wood to the back of the driver?

Thanks Again.

You don't want to "attach" it permanently to the driver magnet. Cut correctly it will be a pressure fit: I use a small dab of double edge tape or ductseal / blue-tak. Ideally this brace will be at least a U-shaped piece, rigidly connecting at least 3 cabinet panels and the magnet. See the part on Dave's drawings described as "holey brace"


http://homepage.mac.com/tlinespeaker...nkenGR-map.pdf