Endo Posted June 6, 2020 Share Posted June 6, 2020 Hello, All I am building an existing design for the Eminence LAB 12 Professional (aka: tapped horn for LAB 12; Claude J1 calls it his "coffee table sub"). QUESTION: Can I "unfold" this design without altering the performance? In other words, if I am careful about maintaining fundamentals like: overall horn length; internal volume; sectional areas at throat, mouth and points between... can I take one of the folds out without hindering performance? The only thing I can think of--is the internal pressure might change due to a 'straighter' run (?) and that the driver might behave differently as a result? Pictures of the original plan and also what I'm suggesting: Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 9, 2020 Share Posted June 9, 2020 You should be able to but it'll be very long. The driver positioning is critical in a tapped horn so be sure you get that right. Pay close attention to the flare rate as well. When you design one of these in hornrsp it comes out as a long sub like you propose but it's folded to make the size more manageable. 2 Quote Link to comment Share on other sites More sharing options...
Schu Posted June 9, 2020 Share Posted June 9, 2020 49.5+20+52.75+44.75+4+27... 😟 1 Quote Link to comment Share on other sites More sharing options...
Coytee Posted June 9, 2020 Share Posted June 9, 2020 On 6/6/2020 at 1:27 PM, Endo said: Claude J1 calls it his "coffee table sub" I thought Claude gave up coffee.... I guess that's more manley sounding than your "Shirley Temple Table" Sub..... 1 Quote Link to comment Share on other sites More sharing options...
Edgar Posted June 9, 2020 Share Posted June 9, 2020 As long as the wavelengths are significantly longer than the height and width dimensions of the internal path, the sound does not even "see" the folds, so it also won't notice that they're not there. Where you get into problems is when the path lengths between the folds are about the same as half-wavelengths -- that causes standing waves. That said, see http://www.audioheritage.org/vbulletin/showthread.php?31499-Jensen-s-own-Transflex. Edit: Also see http://www.cowanaudio.com/images/air_coupler.jpg. 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted June 9, 2020 Share Posted June 9, 2020 is there any advantage to using a radius flare? 1 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 9, 2020 Share Posted June 9, 2020 28 minutes ago, Schu said: is there any advantage to using a radius flare? Not that I've ever heard of. 1 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 9, 2020 Author Share Posted June 9, 2020 Thanks to all for the responses. Ordinarily, I set a very high threshold for modifying a proven design---this is something I typically avoid. In this case, I have been living without a horn loaded, low-frequency cabinet because of the needed space. My wife and I share an 800 sq. ft home. Bring anything through the door and a game of Tetris immediately begins, followed by several OSHA violations. I played around with different locations for the coffee-table-sub, before I gave up and thought about un-folding the cabinet. If I can pull this off, the speaker will sit against the long wall of a room, under a window, and will be built like a bench to match the surrounding cabinets. Its part of a larger remodel project. Thanks, again for all the input. Quote Link to comment Share on other sites More sharing options...
Edgar Posted June 9, 2020 Share Posted June 9, 2020 37 minutes ago, Schu said: is there any advantage to using a radius flare? According to Kolbrek & Dunker, section 26.4, there is some advantage to radiused bends at low frequencies. According to Bruce Edgar (no relation), there is some advantage to full 45° reflectors at high frequencies. You're probably not going to encounter high frequencies, so a bit of corner radiusing might help. 1 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 9, 2020 Author Share Posted June 9, 2020 3 hours ago, Edgar said: 3 hours ago, Schu said: is there any advantage to using a radius flare? According to Kolbrek & Dunker, section 26.4, there is some advantage to radiused bends at low frequencies. According to Bruce Edgar (no relation), there is some advantage to full 45° reflectors at high frequencies. You're probably not going to encounter high frequencies, so a bit of corner radiusing might help. I could do something like the picture here, gluing stacks of MDF curves to fit the corners... don't know about flare at the mouth. after posting this thread, I was reading about the development of the LAB12 when I ran across the Danley DTS20 for the first time... Its roughly, similar in overall dimension and when you look at this photo of the mouth, it doesn't look flat-bottomed... looks like there is a curve or inclined surface just inside the mouth (?) Quote Link to comment Share on other sites More sharing options...
Endo Posted June 9, 2020 Author Share Posted June 9, 2020 ^ Now, I am retracting that last statement--like my eyes were playing tricks--looks like it might be square-cornered (?) I can see the bottom edge toward the back. Quote Link to comment Share on other sites More sharing options...
Edgar Posted June 9, 2020 Share Posted June 9, 2020 49 minutes ago, Endo said: I could do something like the picture here, gluing stacks of MDF curves to fit the corners... According to Kolbrek & Dunker, if you can't also radius the inner part of the fold at least half the height of the duct, then it doesn't much matter whether the outer part is fully radiused, like your drawing, or just uses a flat diagonal plate. They're all pretty much the same. 2 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 9, 2020 Author Share Posted June 9, 2020 I'm looking into this... With trepidation, I feel like I'm venturing into the unknown... right before I step into an unrecoverable abyss... [Leaning back, now, toward my original position of not deviating from a proven, successful design--not meddling with the hard-won efforts of other, more capable people] Reckless behavior can (sometimes) be fun--if you're all by yourself in some kind of parallel universe (or, if you are Bill Gates). But, not me. Not here. The "tapped-horn for LAB 12 driver" works; and not by accident. I will attempt a version that fits my circumstance with minimal alterations. It won't be difficult to improve on what I have now--which is nothing. 1 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 9, 2020 Author Share Posted June 9, 2020 ^ "nothing" translates to "nothing below 38 Hz". Quote Link to comment Share on other sites More sharing options...
Edgar Posted June 9, 2020 Share Posted June 9, 2020 33 minutes ago, Endo said: I'm looking into this... With trepidation, I feel like I'm venturing into the unknown... right before I step into an unrecoverable abyss... I suspect that there is greater danger in folding an unfolded horn than in unfolding a folded horn. The original tapped horns (Jensen TransFlex and JBL Air Coupler) were similar to what you have proposed, so perhaps you can take solace in the fact that it's been done before. 1 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 10, 2020 Author Share Posted June 10, 2020 10 minutes ago, Edgar said: The original tapped horns (Jensen TransFlex and JBL Air Coupler) were similar to what you have proposed ^ thank you, for that. I'm working within limits. Attempting to get this done. I'd rather try and fail, than... well, the other... worst-case-scenario: the driver is used for something else. 1 Quote Link to comment Share on other sites More sharing options...
Endo Posted June 14, 2020 Author Share Posted June 14, 2020 Now I'm contemplating Fitzmaurice's 'Tuba HT' - low profile version... I'm not a guy who can modify, test, and tweak a speaker design... Reading through posts on this forum, I happened on to a link to Bill F's website. Turns out he's got a design that uses the same driver that ALREADY approximates the dimensions of my 'unfolded' horn and fits my available space). Hmmm. Here's my question: Does anyone here have opinions about the Tuba HT coupled with a single LAB12? Comparisons? • The LAB12 has already shipped, so that's a given • also ordered: Lepai with TPA3118 (PE currently has it marked down, for those interested) I'm not finding data on the Tuba HT with a LAB12 (as apposed the 15" driver). Would love to hear from those who've been down this path before? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Edgar Posted June 15, 2020 Share Posted June 15, 2020 14 minutes ago, Endo said: I'm not finding data on the Tuba HT with a LAB12 (as apposed the 15" driver). Would love to hear from those who've been down this path before? The Tuba HT specifies a Dayton RSS390 HF4 15" driver. Substituting drivers in a tapped horn is likely much riskier than unfolding a folded horn. Quote Link to comment Share on other sites More sharing options...
Endo Posted June 15, 2020 Author Share Posted June 15, 2020 Yeah, that was my impression, then I stumbled across this on Bill's website (in the Forum) about using the LAB12 with the Tuba HT. Looks like the man himself (?) I imagined him taller. . Link to thread here... Quote Link to comment Share on other sites More sharing options...
Endo Posted June 15, 2020 Author Share Posted June 15, 2020 ^ It must be the camera angle that makes his ears look horn-loaded. Quote Link to comment Share on other sites More sharing options...
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