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Old 1st December 2012, 12:49 PM   #401
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buzz,

I think your 2nd try .doc will be more pleasing, in room. I see the response drooping (circa 150Hz to 30 Hz, ...over 2 octaves) ~5 dB. Depending on your room characteristics, it will have enough gain which will offset this droop.

Said again: The combination of speaker droop and room gain will offset...you may still realize some net boost in bass response.

Consider the frequency response plot as a representation of the acoustic energy available from the speaker system. By changing the physical dimensions of the box, you are "steering" the energy into a range where it most resembles the original signal.

By including room gain (which is not included in Martin's worksheet) you arrive at a "real" system integration.
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Old 1st December 2012, 01:30 PM   #402
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So, I am basing my designs above on this concept. I model a box based on a 10/1 ratio of Sl/S0. This give me my line length for what would be an open ended tapered TL tuned to about 55Hz for a 37" box. What happens if I take the same concept and apply it to an MLTL? In stead of havinga tapered box, I have a rectnagular box and the port acts as if it were a taper. If I make the port Sd 1/10th the box Sd, I essentially have a tapered TL, but with some advantages. The port allows me more tuning flexiblity than I get with the TL, allowing lower tuning. I dont know what the acoustic ipedance says about the sound, but it i have f ound thta it is basically the same for both boxes if designed using the same parameters. One thing I like about the tapered TL is the lower 2nd resonance peak it offers. This is where the idea of the aperiodic loading comes in. If i could implement it in such a way s to tame the impedance pekas, it should make for a more favorable load for an amp.

THis is all theory and mat be bad theory on top of that
MAin concern is what the acoustical impedance says about the sound. IT makes sense tht it would be similar to a BR, but I have yet to model that.
Attached Files
File Type: doc ALtec 10 to 1 Tapered open TL 55Hz.doc (124.0 KB, 15 views)
File Type: doc ALtec 10 to 1 MLTL 55Hz.doc (139.0 KB, 11 views)
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Old 1st December 2012, 01:30 PM   #403
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Posted this before reading your response. THis is rough draft. I want to play with the tuning a bit.
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Old 1st December 2012, 11:50 PM   #404
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Smaller at around 12^ft, as I was considering interior space vs final outer size. Port is figured based on slot on front of 1.25" baffle. Shown without stuffing as I have been working this way to get an idea of what is really going on before stuffing. Dont even know what it is tuned too, but i think about 32Hz. -3dB around 40Hz and -5db at 30Hz. I think it is an improvement in response. I think i could go lower with bigger box, but not sure i need to. I will measure larger boxes to see what i can do, but it seems that a taller box is needed for good clean results. Perhaps ZM or GM or anyone has an opinion. Either way, I am proud, as I think i have figured it out a little....wel maybe not, but it does look pretty
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File Type: doc Altec MLTL 1.3.doc (155.5 KB, 28 views)
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Old 2nd December 2012, 01:38 PM   #405
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You have as an option including a large chamfer on the front top of your cabinet.

The Orphean MKII has this.

It allows lowering the horn/CD combination to be closer to the woofer. This reduction in the C-C distance between them may improve the integration of the 2 drivers.

Things to watch:

response ripple induced by changing the shape of the cabinet
selection of the x-over point with regard to the C-C distance.

I would rather not build (waste) a test box...I think I will need to in order to test the drivers in situ... Then refine for the "keeper" cabinets.
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Old 2nd December 2012, 01:54 PM   #406
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Since I am using Iwata horns, they will be as close as physically possible. It would seem there is no real advantage to what he has done other than allowing for the physical alignment of the front of the horn and the face of the cabinet. The horn was clearly not located for time alignment and he must be accomplishing this with the xover. I have a minidsp to do the intial xover and then will move to discrete B4 clone for final revision.

You are right about the box. With boxes this size, test cabs get expensive.
I am working on a google sketchup of the cabinet. I also tested the other driver in the cab above and i can get it pretty dead on with little modification.
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Old 2nd December 2012, 11:41 PM   #407
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What is the major advantage of the reduced impedance peaks as seen in ZM's calculations included below?
My ignorant assumption is that it provides a more even load to the amp that should improve performance, but does this play out in real life as audible improvement?
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File Type: jpg Impedance graph.jpg (61.5 KB, 108 views)
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Old 2nd December 2012, 11:51 PM   #408
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well - I was looking at lowest ripple in first few graphs - acoustically ;

that what you're asking is just repercussion of that
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Old 3rd December 2012, 12:11 AM   #409
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Is this reduced acoustic phase ripple the advantage of true Tqwt vs ML-TQWT, like mine? I can reduce mine with more stuffin, but not to the degree that you have achieved. OTOH, the impulse response from mine is very good, which i would think is an indicator of a quick cone response. Just trying to figure out what all these graphs mean. No where does MJK speak to these things.
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Old 3rd December 2012, 12:20 AM   #410
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all I can say is that , properly made long (folded) pyramidal MLTL (or derivation of it ) is much less boxy sounding than BR counterparts

difference is , if you put it that way - that BR is always haroomph-ing through pipe (opening ) while TL (derivatives ) are much less using those openings for relaxation

dunno - I'm telling you - trust to GM's words (even if I sometimes can't grasp sole simple sentence he's writing )

I'm just a tourist in those loudspeaker things
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File Type: jpg Moose_in_harness_t620.jpg (57.1 KB, 102 views)
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