Small horn in 1955

[Jaime]

The grandfathers of the Fostex small horns in 1955.
And an nice amplifier with triodes also (6SL7, 6SN7, 6BX7, 6X5)

“......The construction principles that are explained here are those that are used in expensive cabinets of loudspeakers of great size. Although this same design applied to enclosures of small loudspeakers improvement extraordinarily these systems, the certain thing is that until now it seems to be ignored completely.....”

http://www.mimecanicapopular.com/vernota.php?n=615

Mecanica Popular is the Spanish version of Popular Mechanics

[johninCR]

Jaime,

As far as the speaker is concerned, it looks more like the grandfather of Bose hype, because it doesn't look like much of a rear horn. The added bass output of the unit may be resonance of those huge voids.

[Nanook]

well I translated the isometric drawing to a 2d side view in Autocad. The horn length is approximately 58", So=4.25", Sx =21.85" (or so, I took a little poetic licence). The ratio is 5.1388

Fill the cavities with sand (providing you have a way to ensure they don't topple over). I end up with a 1/4 wave frequency of 58.6Hz for a 58" horn length.

The material is 3/8", so use Baltic birch, finish the interior exactly as the exterior (ie, paint if exterior is to be painted, etc., )

I wonder if there is an English print of these out there:-). I guess somewhat similar to the Frugal Horn, other than Dave has em firing rearward..

[Scottmoose]

I'd call that an expanding TL rather than a BLH. MathCad predicted response attached, using above dims and the FE83E, which is probably going to be roughly similar to the original driver specs. (And the magnet might just about fit).

I've seen worse, though it'll need damping out, and as it's a straightforward expansion as far as I can see, no filter chamber, with the mouth effectively on-axis to the listener, I suspect you'll run into problems with mids coming out of the vent. Note the classic expanding TL nulls at the odd harmonics.

It might go a touch lower due to the reflectinal boundary condition of the floor nominally doubling the mouth size, but I wouldn't bet on it -Fs of most any driver that'll fit this thing will be well over 100Hz, and you won't want to try pushing them too hard. Nothing to stop you from scaling it up though.

[Dumbass]

I dig old articles like that. Check out the styling record changer and amp de tubos.

[planet10]

Originally posted by Dumbass
I dig old articles like that.

Me too. I had a stack of late 40s (and some early40s & early 50s) Radio Craft & Radio magazines. I sold them all on eBay but not before scanning all the articles i found interesting. A treasure trove of info.

dave

[Scottmoose]

Likewise. Some creative stuff that's been forgotten, and can be re-used, with a modern twist. The BIB for example. Be interesting to look at multiple tuned pipes described in Voigt's patent at some point too.

[chrisb]

Originally posted by Nanook
... I guess somewhat similar to the Frugal Horn, other than Dave has em firing rearward..

Having built several pairs of the latter, I'd respectfully suggest : No, I don't think so. I can also attest that Dave's inspiration was of more recent vintage.

[Dumbass]

Originally posted by planet10
Me too. I had a stack of late 40s (and some early40s & early 50s) Radio Craft & Radio magazines. I sold them all on eBay but not before scanning all the articles i found interesting. A treasure trove of info.

The engineering library here at UCLA has Audios going back to the magazine's inception (late 1940s?). When I'm bored I sometimes just flip through them in the stacks, as much for the ads as the articles. Great stuff.

[Nanook]

only in basic overall dimensions, and compact design.

Having redrawn the above horn in Autocad and playing with the internal dimensions only,it's easy to see just how inspired Dave was/is with Frugal Horn Project--kudos to dave (and u 2 chris for building em), Ed form the Horn shop, etc.

Dave's line length of 82 1/2" in the super compact Frugal Horn is , what I believe, one of the most efficient packaging of a line of this length in such a small overall envelope possible (If it is possible to make the length larger within the confines of this envelope, I don't see how).

The best I could do with the "1955" was a line length of 83 2/3" without a compression chamber, Sx/So= 5.14. Maybe my terminology is incorrect regarding the 1955 as a horn