Dallas II

[pete2112]

Finally got round to sorting out some dallasII images. I have put the 2 extra panels in black for the FE208E

http://i78.photobucket.com/albums/j1...MydallasII.jpg
http://i78.photobucket.com/albums/j1...s/dallasII.jpg

Peter

[Andrew]

Hi Pete,

Back again, what's the black bit on your drawing, behind the speaker? Are those the extra panels?

Looking at the dimensions, its all in inches I assume?

Do you have a bigger version of the image, or in a vector format, that you'd be willing to e-mail/share?

many thanks,

-- Andrew

[Scottmoose]

Look like wedges to brace the rear of the magnet to the back of the CC. Ron designed the Dallas, unlike almost every BLH you'll come across, using some compression-horn techniques (as well as everything else, although they pre-date the Austin principle), so they'll come in handy if they are, especially at high SPLs.

Lovely work. Enjoy!

[Andrew]

Dumb question time.

Assuming I was to build the Dallas, than I'm guessing I use a router/table saw to create channel(s) on both the sides pieces so that the lateral sections slot into them, which are then glued up?

Sort of a bit like this?

http://en.wikipedia.org/wiki/Dado_%28joinery%29

thanks,

-- Andrew

[simon2a3]

Hi Andrew,

I haven't built the Dallas II so have no direct experience, but I would say, yes, in an ideal world you could rebate the sides which would make the construction very strong and should help to seal the line. Although cutting the rebates wouldn't be easy it would make locating the other pieces a lot easier during gluing up.

May be easier overall to butt join though. You'd need to get all the pieces between the sides a regular width so that there aren't any gaps, though PVA type woodworking glue is pretty good at bridging small gaps. It's strong too.

Others may have more relevant experience here though.

Scott, I know we had this conversation over a year ago, but I've a hankering to build some more speakers (cos I haven't got enough on right now ). Which cabs would you recommend for my 208eSigmas? I've still got the design you gave me for the larger version of the ones you brought to Owston, and I'm quite impressed by Steve's Metronomes now he has the baseplate (how a 4" driver makes bass like that I don't know!) Any idea how the Dallas compares? Anything else worth considering? Guess they'd have to be "better" than the Fostex factory cabs or there's no point.

Cheers,
Simon.

[Scottmoose]

Oook. (as the Librarian would say).

Nasty one. The DallasII is certainly more refined & the better cabinet, but your factory boxes are no slouches at all, so I'm not sure it'd be worth going for them given that you already have something very good. So if you want to build something, I'd be inclined to take a completely different approach to what you already have & go for something with a different style of presention.

A Metronome should be interesting & give a very different sound to what you've got at the moment. Remember that it won't be as efficient as the horn though -it'll need 4ohms of series resistance as the Sigma's a low Q unit & needs correcting to work properly in a resonant cabinet. I'd be inclined to try a BIB pipe-horn as it doesn't need the resistance, and they do sound rather good. If the full-sized box we talked about before is a little over-large, then you could tune it a bit higher by going for the original 70in height & compensate for the loss of Vb by increasing the WxD dimensions. You'd loose a few Hz of extension, but it'd still be solid to 30Hz, which isn't too shabby. Internal dimensions 9.25in wide x 13.25in deep + thickness of the internal baffle. 70 in tall, start the internal baffle 3/4in down from the top of the front baffle, driver 29.25in down from the point.

[Andrew]

Seriously, do you guys just butt joint your cabs?

-- Andrew

[simon2a3]

Mine are butt jointed, but the form of construction of the Fostex cabs probably helps as there's a fair bit of wood in there to provide a gluing surface. Wood working glue is pretty strong, but I actually used a tub of builders pva from Wickes. Put plenty on (I use a small decorators paint brush) and work quickly when gluing up. Work the pieces back and forth a couple of times if you can to build up stiction; you need to watch you're not spreading glue around too much as it's not easy to get it all the excess off. A few screws to hold if you can (my cabs have two side skins) and some cramps (or pots of paint) and leave well alone overnight. Works for me anyway.

Thanks Scott. I think I might get some 3/4" chipboard and knock some cabs up, should be pretty cheap. If I like them I might "veneer" them with 1/4" birch ply. Cheaper than 3/4" birch ply, and possible better?

Then explain to the missus why I need more than one pair of large speakers...

[Scottmoose]

You could point out to her it's better to have speakers than you going boozing & chasing other women.

Particleboard venered with ply would certainly be better than MDF. The best BIBs use a combination of birch ply and particleboard panels, so as a combination it makes sense -you get the rigidity of the ply while the lossier chipboard helps kill some of the mids we don't want coming up through the horn without resorting to a load of damping (which is often just a bandaid for sloppy design). Keeps it pretty stiff though, so with a minimum 1:12 slope = no slap echo.

[pete2112]

Hi here are the answers to your questions.

what's the black bit on your drawing, behind the speaker?

The black bit behind the speaker is 3/4 ply, i added this after the speakers were built due to starting with fe206 and upgrading to fe208 sigma.

Looking at the dimensions, its all in inches I assume?

Yes the dimensions are in inches

Peter