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I saw a site about a year or to ago with a good project by a Swedish guy called Matheus/ Mathias (sp??), to accomodate that horns really only behave like ideal horns when the WL inside the horn is several times shorter than the horn length, and allow this e.g. where floorpsace is limited, with a 90 degree folded midbass J shaped horn, using a 15" JBL driver.It sounded like a very good way to get sufficient length for good performance down to about 70 Hz, "using height rather than length".
The site has a good "how I did it section"Does anyone know the link?
Thanks
Follow Ups:
http://hem.passagen.se/sajberrapid/But the site is gone.....
Greets!Jumping into the Wayback Machine, click on the asterisked links:
GM
.
dunno if following corresponds to that horn but maybe (?)- can't tell much with 4th order lowpass @200 - can't locate drawing - maybe Mathias will catch this topic and give some good input - to save some depth / not muck up things would be nice
That looks like the system . .Some leads thanks freddy
beautiful work
(you don't ahve the original link?)(The midhorn above, would be a BMS 4592, in either one of Martin Seddon's 204 Hz flares, or a version of Steve Schell's straight sided conical horns)
. . Now I need to work out if any of my drivers will work say 40-300 Hz in a U or a J.
the link might be dead -? when's "The Great Karlson Revival" coming? :^) - I've got one with horn on top which almost works!
;^)
. . roll my own, so thank you for the WHG links
(though like to see what others have done before)Two questions:
If a triangular horn like Steve’s flares from a throat near the ceiling, parallels down the room corners, down facing where the wall meets the corners, and
“about 40 inches of the floor, the throat makes a smooth 90 degree bend out into the room, terminating with an 18" high by 69" wide mouth that hugs the side walls and floor”. . what placement factor should realistically be assumed . . a full 8? 6 or 7?
The other question – throat compression/ mass rolloff tradeoff:
One driver option, the JBL 2202 has a nice high mass rolloff of 588 Hz, but with optimal throat size requires a throat compression of about 380%. :(
For domestic use up to say 110 dB ~ well short of maximum capability, I guess that is still way too high. Is a safe maximum about 200%? Though probably better to avoid sub-optimising throat size by that much, so . .The other driver option (a Lambda) models with optimal throat size only 94% of Sd. It has a mass rolloff of only 200 Hz, adequate for a straight horn if crossed to the mid at say 300 Hz.
Steve’s intention with the single large 90 degree bend, several feet from the driver, was the bend to be relatively harmless.Anyone like to comment on which driver’s throat compression/ mass rolloff is likely a better compromise? Hopefully at least one is realistic
Regards
Greets!Ah, didn't recognize you as 'Richard Grant'. This all got beat to death many moons ago IIRC, so why no horn yet?
Anyway, if the mouth is against the floor and both walls, then the horn is the corner out as far as the top of it extends plus end correction, so call it a lossy 8 since the mouth will unload somewhat before the room gain curve kicks in unless it's in a fairly small, 'tight' room.
I don't recall what drivers were discussed, but the original and current Altec 515.8G's mid 30s Fs/~213 Hz mass corner is a 'no-brainer' for a 300 Hz Fh, with 30-300 Hz requiring a modest ~2:1 CR and M = ~0.7 (though using 1.0 (expo) will in theory sound better), so it will have at least another octave if not lost in the bend. Regardless, there's no need to use a driver with a mass corner higher than required and CRs > 2 can be problematic depending on the driver's design and unless only relatively low power is used, ~3 is considered the practical limit with a typical prosound driver AFAIK.
GM
GM
A while back I was looking at a midbass horn, but reluctantly decided thn that with family etc & very limited build time, I would instead KISS, with a HE driver in just a midbass box.(That was also partly as I had a got a taste of the sonoc joys of 845 SE's. I later came to appreciate that it's one of the harder, more dangerous, most expensive amps. It's been said that an 845 with a 45 driver, is an 45 on steroids).
If "adding 9 dB of steroids" (the extra power of an 845 over a 45 amp) done properly costs an extra $1- 3 k, danger, etc I started to look for a ways to drop the $$ 845 'steroids'.Back on topic:
A horn would do me, volume wise, with a relatively simple 45 amp (for which I have the parts, and a just received copy of Morgan Jones tube amp building book). So the horn idea has resurfaced, but with a J horn allowing an extra octave at the low end, and maybe losing less than an octave at the high end.> a lossy 8
That's what I was thinking, to be conservative I'd allow a 7.While Altec 515's might well be ideal, i'm hoping unless they're clearly out of the ballpark, to use one one of the 4 different pairs of HE low Q drivers I've accumulated.
> mid 30s Fs/ 213 Hz mass corner is a 'no-brainer' for a 300 Hz Fh
One of my driver pairs is the PHL 5320: a prosound driver with damped paper fibre cones, flux ring; Fs of 45 (a tad higher), but mass corner of 290 Hz ~ similar BW, slightly higher range . . Good so far.
CR is about 2.5, fine I would think if not driven hard.Your comments have helped firm that up as the best of my candiadates, and unless I've missed something, a fairly reasonable one . .
Cheers
Greets!Based on published specs, I get a much higher CR/lower 'M' for an optimized 30-300 Hz BW, so IMO a larger throat is in order, or ~30-205 Hz gain BW and let the driver's excess rising response/horn's directivity to fill in the rest. That, or since we're talking seriously low power, take it out to where the driver wants it at ~410 Hz/~M = 0.7, where again 1.0 is an option, though it will need to be much longer with another bend to take full advantage of its potential extra LF gain BW.
GM
Hi GM> I get a much higher CR
That has me puzzled. Throat area I have as
2* Pi* Fs * Qes* Vas * 10/ Speed of Sound
ie about 6.29 *45 * 0.31 * 128* 10/ 343 = 327 cm²
Sd is 855, so CR is 2.61. Highish, but with only 2 watts . .You suggested "~30- 205 Hz gain BW", rather than up to 300 Hz. Apart from driver mass rolloff, how is the top end of BW estimated?
> and let the driver's excess rising response/horn's directivity to fill in the rest.
hadn't factored that going the "other way", thanks.> since we're talking seriously low power, take it out to where the driver wants it at ~410 Hz
(The piston range is up to 326 Hz) - that would allow better overlap with the midhorn, but how is the 410 Hz estimated?> it will need to be much longer with another bend to take full advantage of its potential extra LF gain BW.
I'll only have one bend to maximise the top end of BW, so will fill in the deep bass with a sub & SSCheers
Greets!I use Leach's math, which calcs a smaller throat to achieve greater acoustic power when loaded with the appropriate horn Vs Keele's greater acoustic efficiency. BTW, according to the PHL specs its Sd = 892, not 855. When this is factored in the gap between the two is still significant, but not the 'night n' day' I implied.
You have to 'do the math' to calc the HF gain BW based on the horn's roll-off, driver's response, and the directivity gain, so well beyond my basic math skills. I just know that when using Leach's math that a good rule-of-thumb is to set the horn's HF corner a half octave below the driver's mass corner for a decent trade-off between the three and if you want the horn to do all the work to the mass corner, then set its HF corner a half octave above it, ergo at 290 Hz, this equates to ~205/410 Hz. At the desired 300 Hz then, this requires a ~212 Hz mass corner, which the Altec driver's ~213.7 Hz matches 'close enough'.
GM
Hi GMI used the Tractrix Calculator from www.volvotreter.de/dl-section.htm, (using the formula used by Edgar).
Thanks for the pick-up on the PHL Sd.I need to find out how to calc the HF gain from the horn's roll-off and the directivity gain ~ would you suggest Leach/ Dinsdale/ Edgar/ Voight ??
Cheers
Happy New Year!FWIW I don't recommend using Tractrix down this low unless the flare frequency is at least 0.7x the desired Fc, but then you wind up with a ~hyperbolic once you cut off the oversize mouth, so might as well use Leach and attach an expo flare to it if you want a shorter, lower distortion horn.
I assume that there's some combined formulas to predict all this, but even if I've seen them I just skipped over it since it's literally 'Greek' to me, so you'll probably have to start a new thread for this info. MJK's MathCad worksheet attempts to predict the on-axis response, but it assumes a round horn and apparently only ~accurate with a conic expansion.
BTW, it's Voigt.
GM
Hi GMThanks your suggestions.
I'll look carefully at them and Steve's corner horn material over the next week or two.Happy New Year
Cheers
I probably should have made it explicit, that to allow the folded horn to go high, I'm referring to a single 90 degree turn.
Steve,
Matheus may have been inspired by your design from 2001, which I just came across tonight. http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=16329&highlight=90+degree+horn&r=&session=
What are your reflections now about that design?While initially I had had in mind a straight going down to say just 75 Hz, your post mentioned a flare of 35 Hz . . as they say in England "in for a penny, in for a pound"
35 Hz with a horn-length of 1/4 WL requires a horn-length of 8 feet/ 2.5 m - some extra may be needed if the corner loading is not perfect, but doable in most normal lounge rooms :)
I'd been thinking lately that for me building bass horns were too time consuming, esp. if I just got down to 75 Hz, but as this adds about another octave, that then covers most of the musical bass spectrum. And personally I like the idea of tall corner speakers.
Could you email plans (and any photos) to rick57 at optusnet.com.au please.Anyone else tried this?
Thanks
Hi Richard,It is funny that you should mention the 35Hz. corner horns. I recently reassembled them and put them back into service after years of stubbing my toes on parts of them around the house.
I will gather up some documentation on them and send it to you.
Hi SteveThanks for the material. I replied offline, but for those following the thread, compact of footprint, to my eyes stylish, and a very handy banwidth. A great compromise.
"Honey, look at this pair of organic sculptures that we can put in those under-used corners!" . .
Cheers
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