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
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
small horns..
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..
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..
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.
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.
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similar to Frugal Horns..
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
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
Re: similar to Frugal Horns..
It is possible. I have drawings pointing towards Frugel-Horn 2.0, but some details will require an as yet undeveloped version of Martin's sheets. The 1st step in that direction is getting a set of Frugel-Horn 1.0 into his hands (and that is underway).
dave
Nanook said:
It is possible. I have drawings pointing towards Frugel-Horn 2.0, but some details will require an as yet undeveloped version of Martin's sheets. The 1st step in that direction is getting a set of Frugel-Horn 1.0 into his hands (and that is underway).
dave
Re: similar to Frugal Horns..
Easy, just reduce or eliminate the void areas. Just tell me the chamber size, length and expansion profile that you know will work, along with the hornlength+distance to baffle (to cover phase issues at the uppoer horn cutoff), and I have the folding scheme with a shallow bend and 2 folds. I was just waiting for the Frugal dimensions to be set in stone before building both and have something for direct comparison. I don't feel comfortable going out on my own trying such tiny horn dimensions.
Nanook,Nanook said:
Easy, just reduce or eliminate the void areas. Just tell me the chamber size, length and expansion profile that you know will work, along with the hornlength+distance to baffle (to cover phase issues at the uppoer horn cutoff), and I have the folding scheme with a shallow bend and 2 folds. I was just waiting for the Frugal dimensions to be set in stone before building both and have something for direct comparison. I don't feel comfortable going out on my own trying such tiny horn dimensions.
AndrewT said:
In a back loaded horn, you don't want mid frequencies to come out of the mouth... you want to lift the drooping response in the bottom to make it flat (red in the FE126e FR plot attached) or lift it a bit to compensate for baffle-step (yellow -- which with BS would be where the red one is). Note that there will be a dip in FR due to baffle-step between where it starts and where the horn action can start creating lift, hence the need for a wide baffle so that baffle-step doesn't start until where the horn can start compensating for it (hence the supra-baffle on the RonHorns & the Frugel-Horn, or the wide baffle in John's tombstone proposal.
Rear mouth gives the advantage of using a wall/floor or a corner to multiply the mouth size. Otherwise you are faced with a Klien-horn size box (KH designed to do 30 Hz in free-space IIRC).
By using the corner (and the deflector to further increase mouth size) the Frugel-Horn, for example, has a mouth large enuff to hit ~50 Hz. Against a wall/floor this would be ~70 Hz
In a box such as the Fostex recommended horn for the 108es with a front terminus up off the floor, we don't really have a horn at all, but a transmission line.
An approximation of the cut-off of a horn is that the circumference of the mouth equals the wavelength of the cut-off frequency divided by the multiplier (1 for free space, 2 for floor loading, 4 for wall/floor, and 8 for a corner) -- approximation because the further the mouth is from a circle, the less true it is.
In the FE108eS fostex "horn" circumference = ~35" with a multiplier of 1 -> ~400 Hz. Since we are trying to have the terminus output fall above 200-300 Hz you can see there is really no horn action at all.
In the Frugel-Horn (Level 3) the mouth circumference is ~120" with a multiplier of 8 -> 15 Hz. The reallities of the rapid flare at the end and the high aspect ratio means that this potential is not met. We'll see how low they really go when we can get a mic on them.
It is pretty easy to see that any rear-load horn with a front mouth is either going to have to have a very large mouth or depend on TL action for the lowest frequencies.
Another advantage of the rear mouth is that it gets the driver (think satelittes) out a bit into the room where they will image better, yet leave the mouth (woofers) near the room boundaries for maximum reinforcement.
dave
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