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InDIYana 2024; "Inner Sanctum" theme announcement...
Welcome to the 'Inner Sanctum', the complementing secondary volume for a woofer alignment in a 2way or 3way consisting of 1.5ft^3 gross. Stand mounts preferred, but not required.
No cost limits of any kind, nor xover limits, nor restrictions on what drivers to use. If you have them, use them! Passive xover implementations only, please, for this challenge, but entering the challenge is not required for attendance if more than observing.
Photos or drawings of internal construction must be provided for verification as visual inspection will not likely be possible. Simple large window braces or simple large holes do not conform to the dual chamber specifications. This should be specified as a vent, PR, driver, or air flow restriction between the 2 chambers in the most common definitions.
Basically, the woofer alignment must incorporate a dual chamber arrangement. This allows isobaric, 4th or 6th order bandpass, Augmented PR (noted in the LDC), multichamber aperiodic(MAPD), dual (or more) chamber bass reflex or DCR+, HPAS, or any other dual-chambered or more arrangement. Feel free to do the same with the optional midrange if you wish, but it is not required, nor will it take the place of the required woofer envelopment.
Since multiple woofers can be used, 2 different alignments or one for each woofer can be applied. They do however have to be different alignments if both woofers do not share both chambers. However, using a pair of woofers in the same plane will require it be a 2.5way, no matter either TMM or MTM. Same plane dual woofer 3ways, or 3ways with dual woofers facing externally are not allowed. Dual external woofers are for 2 or 2.5ways alone.
Dual transmission lines are also allowed via a single driver like the Bose cannon, or dual driver while following the above rules.
Stubbed vented alignments, as in 4thtry's Plummer's Delights from the Nano challenge a few years ago are allowed, BUT the stub chamber and port diameter must not be of the same shape or cross-sectional area. This constitutes 2 chambers, and therefore is allowed.
I look forward to your experiments, and the outcome of this challenge.
See you there next year,
Wolf
Comments
I want some of what you are smoking when you come up with these theme/challenges!
In my experience and observance, it is pretty cool what kind of results can occur via careful multichamber arrangements. Chuck and I conversed on this at length initially, as this is something we've not yet required.
I almost feel like I have to use lawyer speak for clarity to reduce the number of queries or allowances that ensue. This is the main reason for the very wordy announcements. I always try to make the project doable as a rule, though some entrants feel I am too lax with the restrictions.
There are a few more ideas I have for themes yet to come....
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DCR has always been interesting to me, it's some kind of madness
Gotta stretch those minds!
I can't wait! I look forward to it.
Are Coax drivers allowed?
Sure.
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I’m going to have to study this for sure. One cup of coffee isn’t enough this morning to make much sense of it.
+1 to the second cup and to wanting to enter a design next Spring. Entering a design in the 20/20 theme was fun.
APR would be easy to do with 2 different sized PRs, a section of all thread, and a couple locking jam nuts.
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Not sure I understand what that would do, but probably a subject for another thread.
Oah gosh I just looked up some diagrams... That raises more questions than it answers.
Can you expand on the Bose cannon and transmission line comment? The Bose cannon looks like a bandpass arrangement with a mass loaded length. Would a front loaded TL with a sealed woofer section qualify? Only with a tapered front loaded TL? How do you distinguish between a front loaded horn and a TL?
Never seen or heard of one of those.
It was a prosound Bose subwoofer, IIRC, driver is centrally mounted in a tube (hence, cannon) and a different quarter wave resonator to either side. The length prevented cancellation of the driver, and the two different tunings added in output.
John, are you asking about a 4th order TL bandpass, where the exit is a TL + terminus on one side and sealed on the other? That would be fine.
I would have to draw the line at front horns though, as those are not really 'chambers'.
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Yeah, I searched it, just saying, in 7 years there, never even seen/heard of it.
They did use a pretty badass B&C driver in the 502 subwoofer. Almost scored a few of them, but parts guys scrapped them.😡
Still have the VC at my bench from that one.
https://www.google.com/search?q=bose+cannon&source=hp&ei=aOatZNztGqrG0PEPwtOK8A8&oq=bose+cannon&gs_lcp=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&sclient=mobile-gws-wiz-hp#cobssid=s
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Obviously, the dimensions allowed by the theme will not allow the full sized tube and 25Hz F3.
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I hope to hear stuff that will dig deeep next year. If I try something that'll be what I'm shooting for.
I'd like to see and hear that too. What options you can do are pretty vast...
Isobaric for reducing volume, aperiodic vents for damping where needed, multivents and chambers to smooth out the bass or yield emphasis via bandpass. I implore any entrants to try something different than the cookie cutter examples I gave earlier. Combinations or further extrapolation like 3CR, or using a dud driver with resistance across for aided damping as a PR. The choices abound...
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Based on your response to John, it sounds like a tapered and folded quarter wave pipe would qualify?
As long as you had another chamber, yes.
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Sealed or ported box with a front loaded horn seems to qualify. Gets a bit tricky when defining what a front load horn is. The extreme example would be a woofer in an H frame. There are chamber resonances in an H frame to deal with so are those two chambers?
So @DrewsBrews @Billet comment concerning a tapered quarter wave pipe in front of a driver is a front loaded horn.
Yeah, I was thinking of a classic folded Tapered Quarter Wave Pipe (TQWP) back loaded. It has two sections, but it is really one long chamber. So a no go for me...
A front loaded horn would be interesting, but I suppose doesn't really fit the intended spirit of the theme.
Excuse my ignorance , but what does the acronym APR stand for ? Acoustic Passive Radiator ?
JohnH-I don't see TL or MLTL as horns. What are you getting at?
Nick- Augmented Passive Radiator
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If you mounted a TB W6-1139SIF (Fs 35Hz) about 1/3rd the way down a 6" diameter concrete tube, you could get close to an 8 foot long TL before hitting the 1.5 cu. ft. limit. Quarter wavelength at 35Hz is 8 feet. Call it the Hose Wave Cannon!