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Old 15th February 2007, 08:02 PM   #11
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Quote:
Originally posted by pjanda1
The BIB is a BLH. (Of course, if your MLTL is expanding, you could call it a ML-BLH too, if my understanding is correct.) With 12ft ceilings, you'd want to consider an inverted BIB. It would work mouth up, but it wouldn't load as well as it otherwise would (though some clever reflecter might work too). Inverting it would help get the drivers to ear height as well.

pj
Well, not really. You may in certain designs get some horn action but no it is not a horn. Transmission lines work by amplifying the 1/4 wave of the FS of the driver in a resonant tube. A horn actually takes the output from the rear of the driver and amplifies the entire spectrum down to whatever the tuning of your horn is. (very simplified terms) The way you stop a horn from amplfying the entire signal is through the use of a coupling chamber which in effect is a mechanical crossover that cuts the sound off above a predetermined frequency. Now, it is possible and quite likely that you will have some TL action in a horn, but in most cases not enough to take note of. Ideally if there is some, you want to have TL action and horn action working together but it is hard to get right and tends to muddy up the bass a bit. Remember, The reason a horn works is the flare constant mixed with length, throat and mouth size. In a TL you will get differing results with a more or less tapered design but what matters is not nessessarily the taper but the length and cross section of the tube as well as the driver placement. As always, if anyone sees error in my statement, I am always happy to take correction. I hopethis helps in your journey.

Tom
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Old 15th February 2007, 08:03 PM   #12
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pj -Yes, I've noticed that all enclosures aren't tuned to the same freqency.

For a regular BIB, you'd be looking at a driver about 39in off the floor, fractionally off-vertical axis for most of us, which is beneficial in flattening the rising response of the drivers. Unless of course higher SPLs for the treble are desired, as some people wish.

Generally the BIB is a little better than an MLTL in controlling driver excursion, but actually not that much, until they're properly positioned in a corner, which pushes it down considerably. Because it's tuned so low, they can often push the point of maximum driver excursion 1 octave above Fc into a slightly less critical zone. Every little helps, though I think people tend to set too much stock by this.

Tom -actually the BIBs are technically a branch of horn. All TQWTs or expanding lines can be considered as such, at a very basic level. They're just a specific type; end-loaded, with linear taper. A horn does not automatically have to have a filter chamber -it was Olson who introduced that in the widest sense in his 1937 patent. Look at all those gramophone horns, or the traditional megaphones. It's the usual grey area really as to where one type starts and another leaves off. I tend to consider all expanding lines from the horn perspective when designing.
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Old 15th February 2007, 08:36 PM   #13
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Quote:
Originally posted by Scottmoose
pj -

Tom -actually the BIBs are technically a branch of horn. All TQWTs or expanding lines can be considered as such, at a very basic level. They're just a specific type; end-loaded, with linear taper. A horn does not automatically have to have a filter chamber -it was Olson who introduced that in the widest sense in his 1937 patent. Look at all those gramophone horns, or the traditional megaphones. It's the usual grey area really as to where one type starts and another leaves off. I tend to consider all expanding lines from the horn perspective when designing.

Scott, I have always been under the impression that for a horn to be a true horn it had to have a flare constant (as in curve)? Hmm. That's good to know! Thanks!

I love posting here. People generally are so good at replying without pretense. And Scott has been in all cases for me the most helpful of anyone. Listen to this guy, he knows what he is talking about! Hehe. Sorry for the ego stroking Scott, just wanted to extend my thanks.

Tom
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Old 15th February 2007, 09:20 PM   #14
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You're welcome -if I can help with anything, I try to (even if my sense of humour occasionally gets the better of me, for which I apologise ). But I don't pretend to be an expert though -I leave that to my betters -in particular, GM, Martin, Dave, & Ron. Those guys are the Masters & I owe them a lot -what little I know I learned from them, along with our much-missed friend Terry Cain, who got me into the BIB thing in the first place a few years back.

In a sense a horn does indeed have to have a flare constant -the BIBs expansion is continued by the room, which forms a part of the speaker-system / cabinet. I'd probably put it around the catenoid region, but that's fudged -depends on where you stand the things!
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Old 16th February 2007, 02:22 AM   #15
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Greets!

Horns don't have to have a flare constant, it just has to expand enough for 1/2 WL action to occur, changing the pipe from a 1/4 WL resonator (only odd order harmonics) to a 1/2 WL resonator (both even and odd orders) with a 1/4 WL fundamental: http://hyperphysics.phy-astr.gsu.edu...opecol.html#c1

Where folks get confused is that they look at a compression loaded horn and conclude that this system is the horn because it's what the pros call them, when actually it's a 4th order bandpass speaker with a tacked on acoustically large expanding vent designed to ideally load it at the inverse of its response, so we start with a severely under-damped, limited BW speaker and through acoustic transformation convert it into a severely over-damped one of much wider gain BW.

GM
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Old 16th February 2007, 07:54 AM   #16
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And as ever, many thanks for that Greg. This is a concept that until now I've been hazy on. Not any more though...
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Old 16th February 2007, 11:09 PM   #17
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I never cease to be amazed. Proof that this is a wonderful place to post and read the replies that follow. Thanks guys! I never knew any of that. Thanks Greg!

Tom
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Old 17th February 2007, 04:04 PM   #18
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Greets!

You're welcome! Just 'horn basics for the masses' published in various DIY books such as where I learned it, Cohen's '56 'HI-FI Loudspeakers and Enclosures'. Lacking this basic understanding, I imagine that compression horn design must seem like a form of black magic even with a simming program since there's so many variables to juggle.

GM
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Old 19th February 2007, 03:59 PM   #19
britbug is offline britbug  United States
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Thanks Guys.
Seems like these have not been built yet.
Anyone seen the sim for DX2. The great zilla site doesn't have these up for this particular combo?
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Old 19th February 2007, 04:12 PM   #20
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As designed by GM:
Attached Images
File Type: gif dx2.gif (6.9 KB, 359 views)
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