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Old 13th September 2006, 03:55 PM   #1
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Question Mass loaded horn?

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
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Old 13th September 2006, 04:55 PM   #2
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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
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Old 13th September 2006, 10:23 PM   #3
ronc is offline ronc  United States
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IMHO a BLH is partially a MLTL with acoustic gain. For that matter even a FLH.
ron
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Old 14th September 2006, 03:49 AM   #4
GM is online now GM  United States
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Default Re: Mass loaded horn?

Quote:
Originally posted by cheesehead
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
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Old 14th September 2006, 07:13 AM   #5
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Thanks for putting us right guys. Greg, good to see you -noticed you'd been away from the boards for a few days.

Regards
Scott
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Old 14th September 2006, 07:25 PM   #6
chrisb is online now chrisb  Canada
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Quote:
Originally posted by ronc
IMHO a BLH is partially a MLTL with acoustic gain. For that matter even a FLH.
ron

Ron - you've been talking to Ed Schilling again?
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Old 14th September 2006, 07:57 PM   #7
GM is online now GM  United States
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Greets!

You're welcome! Yeah, 'life' keeps getting between me and my hobbies.

GM
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Old 15th September 2006, 07:03 AM   #8
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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
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Old 15th September 2006, 07:05 AM   #9
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Oh yes. GM's designed an ML version of the BIB for the Visaton B200, and there's one lurking around for Isophon drivers I believe.
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Old 17th September 2006, 05:28 PM   #10
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Quote:
Originally posted by footstony
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
Scottmoose

Have your ever considered modelling a BIB with two labhorn drivers (isobarik) for some REAL DEEP BASS?
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