OK, I've got a question... probably a crazy one. Started with this thread on the metronome:
The metronome which has a quadratic cross-section
and the Spawn of Frugel-Horn...
Spawn!
Can you build a mass-loaded back-loaded horn? MLBLH?
I take Martin's work as a start. Before he started, a transmission line was a 1/4 wave straight pipe. Very big. Some worked, some didn't... then Martin did his voodoo and showed that you could "mass-load" a TL, and came up with a set of equations to model behavior. The result - a MLTL is usually much smaller than a comparable "classic" TL.
What effect would one get from doing the same with a horn? Capping it and adding a port? Make it smaller?
BTW, my hats off to Martin and all the horn people out there. I've got a Ph.D. in physical chemistry, so I don't consider myself mathematically illiterate (course my continuum mechanics was long forgotten!) And I've spent a couple of hours with Martin's theory, hoping I could figure this out myself... no luck
Thanks much for the thought.
cheesehead
The metronome which has a quadratic cross-section
and the Spawn of Frugel-Horn...
Spawn!
Can you build a mass-loaded back-loaded horn? MLBLH?
I take Martin's work as a start. Before he started, a transmission line was a 1/4 wave straight pipe. Very big. Some worked, some didn't... then Martin did his voodoo and showed that you could "mass-load" a TL, and came up with a set of equations to model behavior. The result - a MLTL is usually much smaller than a comparable "classic" TL.
What effect would one get from doing the same with a horn? Capping it and adding a port? Make it smaller?
BTW, my hats off to Martin and all the horn people out there. I've got a Ph.D. in physical chemistry, so I don't consider myself mathematically illiterate (course my continuum mechanics was long forgotten!) And I've spent a couple of hours with Martin's theory, hoping I could figure this out myself... no luck
Thanks much for the thought.
cheesehead
We all owe Martin a massive debt of thanks for all that he has done, and continues to do. He's provided accurate software capable of simulating many enclosure types, and helped lay many myths to rest.
FWIW, the term TL has caused far too much confusion. Bailey / Bradbury have much to answer for.
First was the QWR -Voigt and the big US concerns were playing with these in the 1930s if not earlier. They are basically resonant enclousres. The TL created by the aforementiond B/B is pretty much the opposite: it's heavily stuffed so it becomes effectively non-resonant. For some reason though, probably because they used similar line lengths, the TL term stuck and has driven people mad ever since.
Re the idea of an ML horn, it's an interesting question. It'd be possible to check what would happen in BLH Sections. But I don't think it'd work well. Or -it probably could be made to have a decent response, but at the sacrifice of a lot of the original advantages of the horn enclosure. Quick answer is 'sort of', but if you choke the area of a horn's terminus down, it would no longer really be a horn any more. The area between what is a horn and what is an expanding TL is a hazy one (even more so when ML is applied) especially because most domestic horn designs are really more bandpass designs with long expanding vents, but there are a few basic principles at work, and one is said expansion and the mouth size. If you mass load it, you'll loose most of the efficiency you gain from horn loading, and the coupling of the driver to a very large quantity of air.
Any other views horn experts?
Scott
FWIW, the term TL has caused far too much confusion. Bailey / Bradbury have much to answer for.
First was the QWR -Voigt and the big US concerns were playing with these in the 1930s if not earlier. They are basically resonant enclousres. The TL created by the aforementiond B/B is pretty much the opposite: it's heavily stuffed so it becomes effectively non-resonant. For some reason though, probably because they used similar line lengths, the TL term stuck and has driven people mad ever since.
Re the idea of an ML horn, it's an interesting question. It'd be possible to check what would happen in BLH Sections. But I don't think it'd work well. Or -it probably could be made to have a decent response, but at the sacrifice of a lot of the original advantages of the horn enclosure. Quick answer is 'sort of', but if you choke the area of a horn's terminus down, it would no longer really be a horn any more. The area between what is a horn and what is an expanding TL is a hazy one (even more so when ML is applied) especially because most domestic horn designs are really more bandpass designs with long expanding vents, but there are a few basic principles at work, and one is said expansion and the mouth size. If you mass load it, you'll loose most of the efficiency you gain from horn loading, and the coupling of the driver to a very large quantity of air.
Any other views horn experts?
Scott
cheesehead said:Can you build a mass-loaded back-loaded horn? MLBLH?
Greets!
Back in the late '40s, Altec Lansing began marketing the A800 Voice of the Theater (VOT or VOTT) cinema speaker system, a front horn loaded, simple mass loaded backhorn, though TTBOMK it was always referred to in print as a FLH/BR combination cab. Without baffle 'wings' and a different HF horn assembly, it became pretty much the standard in large studio monitoring, small cinema, band, and PA sound systems for decades in various A7 VOTT configurations and is still a favorite in H.E. HIFI apps, so yeah, you can.
BTW, any positive expanding pipe is technically a horn, so MJK's ML-TQWT, Voigt and Weems pipes, etc., are technically ML-BLHs. A TQWT is a reverse tapered horn, which by definition mass loads the terminus just as a FL or BL horn mass loads its throat, so ML-TQWT is just stating the obvious IMO, though I suppose one can argue that when adding a vent tube to the terminus it changes enough acoustically to warrant the prefix.
GM
Hi cheesehead,
I have been thinking about this also.
I think Tom Danley has already done it with his tapped horn.
check out this one:
http://www.danleysoundlabs.com/DANLEY_dts20.htm
he calls it a horn but there is no way that mouth is big enough for "Solid output down to 15Hz"
could you model a bigger is better enclosure as a mass loaded conical horn?
more questions than answers I'm sorry, but a very interesting thread anyway.
Regards Philip
I have been thinking about this also.
I think Tom Danley has already done it with his tapped horn.
check out this one:
http://www.danleysoundlabs.com/DANLEY_dts20.htm
he calls it a horn but there is no way that mouth is big enough for "Solid output down to 15Hz"
could you model a bigger is better enclosure as a mass loaded conical horn?
more questions than answers I'm sorry, but a very interesting thread anyway.
Regards Philip
Thanks everyone...
just a note to say that I'm reading with interest. Life interferes, tho; my university chem students are at a particularly confusing part & require lots of encouragement.
Gotta pay up and get those new MJK worksheets (I've got the earlier, "no-pay" ones right now) and start doing some simming myself.
cheesehead
just a note to say that I'm reading with interest. Life interferes, tho; my university chem students are at a particularly confusing part & require lots of encouragement.
Gotta pay up and get those new MJK worksheets (I've got the earlier, "no-pay" ones right now) and start doing some simming myself.
cheesehead
25Hz at -3dB in room
Not a crazy idea. It works. I got 25Hz at -3dB in room out of a FE108EZ. 20Hz at -7dB (still in room). On warble tone, 20Hz is clearly felt, and no the driver isn't going in overexcursion.
I'm sure everyone will yell that it's impossible to get that kind of bass from a 3in cone and I don't believe it myself.
For that very reason I booked (and paid for) the anechoïc chamber at the NRC so I'll have independant and trustworthy data to back the claim.
So mass loaded horns, IMHO are an area definitely worth considering. It's also impossibly hard to calculate the outcome, sort of a black hole...
Not a crazy idea. It works. I got 25Hz at -3dB in room out of a FE108EZ. 20Hz at -7dB (still in room). On warble tone, 20Hz is clearly felt, and no the driver isn't going in overexcursion.
I'm sure everyone will yell that it's impossible to get that kind of bass from a 3in cone and I don't believe it myself.
For that very reason I booked (and paid for) the anechoïc chamber at the NRC so I'll have independant and trustworthy data to back the claim.
So mass loaded horns, IMHO are an area definitely worth considering. It's also impossibly hard to calculate the outcome, sort of a black hole...
At low frequencies, where the axial length direction dominates, it should be relatively easy to calculate and correlate the response with actual measurements from an anechoic chamber. In room response might be a little tricky but I believe it is not that difficult to simulate and design using an appropriately configured computer code. I have done this for one commercial BLH speaker system where third party measurements were available and the correlation was excellent after the first modeling attempt. I have also recently done this on three designs from German Hi Fi hobby magazines where the enclosure plans, measured driver T/S parameters, and SPL and impedance measurements were published and again the correlation was very good. No black hole or voodoo required.
Official!! 20Hz from FE108EZ!!
Yipee!!
Unbelievable 20Hz in-room measurements were confirmed today at the NRC anechoïc chamber facility.
OdB reference point is 90dB (average sensitivity, 20 to 20K).
20Hz, anechoïc -6dB, port reading
25Hz, anechoïc, -2dB, port reading
30Hz, anechoïc, 0dB, port reading
In room with back wall loading (vent on the rear) should give 20Hz at 0dB depending on placement.
Further R&D needed to optimize cabinet rigidity/damping. No compression measurements done yet, but output very clean in smaller rooms, so compression figures should not be too bad.
Yipee!!
Yipee!!
Unbelievable 20Hz in-room measurements were confirmed today at the NRC anechoïc chamber facility.
OdB reference point is 90dB (average sensitivity, 20 to 20K).
20Hz, anechoïc -6dB, port reading
25Hz, anechoïc, -2dB, port reading
30Hz, anechoïc, 0dB, port reading
In room with back wall loading (vent on the rear) should give 20Hz at 0dB depending on placement.
Further R&D needed to optimize cabinet rigidity/damping. No compression measurements done yet, but output very clean in smaller rooms, so compression figures should not be too bad.
Yipee!!
Re: Official!! 20Hz from FE108EZ!!
Unbelievable!? With a FE108EZ? Thatth's Inconthievable!
OK, now you've asked for it. You tease - What's the design? Tell us or we'll come to Montreal and apply special techniques
to get you to cough it up!
Seriously, wow. I must express skepticism if only to reassure myself that what I know about speaker design is still correct.
cheesehead
robertG said:
Unbelievable!? With a FE108EZ? Thatth's Inconthievable! OK, now you've asked for it. You tease - What's the design? Tell us or we'll come to Montreal and apply special techniques
to get you to cough it up! Seriously, wow. I must express skepticism if only to reassure myself that what I know about speaker design is still correct.
cheesehead
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