https://www.htguide.com/forum/ HTGuide Forums en Mon, 10 Aug 2026 23:34:32 GMT vBulletin 60 https://www.htguide.com/forum/images/misc/rss.png https://www.htguide.com/forum/ https://www.htguide.com/forum/mission-possible-diy/build-stories/961267-sonosub-build-16-15-5-id-tube-ss12-22-15-hz-replacing-an-sb-1000 Mon, 10 Aug 2026 16:29:00 GMT
Going with a sonosub because I want the volume without the footprint, and because a 15.5" ID form tube is the cheapest 5 cubic feet you can buy. Everything is on hand now, so here's the design before I start cutting, partly to write it down and partly because if I've got something wrong I'd rather hear it from you lot than discover it after the glue sets. The parts

• Dayton Audio SS12-22, 12" DVC, ±23 mm Xmax, Sd 528 cm², Fs 27 Hz, Qts 0.35, Vas 49.4 L
• 15.5" ID form tube, 48" long, staying uncut
• ICEpower 1200AS1, mounted internally
• DSP, connectors
• Five 24×48 3/4" MDF hobby panels
• 4" Schedule 40 PVC port with flares on both ends
• 1 mm vinyl wrap, 6" metal legs, three of them in a tripod

The design

net volume 122.9 L / 4.34 cu ft
tuning 15.0 Hz
port 4" ID, 30.99" assembled, flared both ends
alpha (Vas/Vb) 0.402
h (Fb/Fs) 0.556
cavity 45.75" between caps
overall height 55.4" including legs
estimated mass 84 lb, CoG 21.1" off the floor

That's an extended-bass-shelf alignment rather than a maximally flat one, which the tube volume more or less chose for me. Modelled half space at 1 m it comes out flat within ±0.4 dB from 14 to 28 Hz, then tilting up about 5 dB to 100 Hz, and −3 dB at 13.4 Hz relative to its own bottom-end plateau. The tilt gets a shelf filter in DSP and the low pass sits at 80 anyway, so I'm not bothered by it.

For context against what it replaces — SB-1000 is published at 24 Hz, this models to 13.4 Hz, though I'll be the first to say those are different measurements under different conditions and I'm not pretending it's a clean comparison. It's about four and a half times the internal volume and three times the power, so it ought to be a decent step regardless. The part I'm less happy about


The 4" port is the limiting element in this design, not the driver, and I want to be upfront about it rather than have somebody point it out on page three.

Small's minimum vent diameter for Vd = 1.21 L at 15 Hz works out to 4.48". I've got 4.00", which is 12.57 in² — 15% of Sd. Near tuning that reaches 17 m/s peak, the usual ceiling for a flared port, at about 84 watts. So the bottom octave is port-limited, not amp-limited:
12 Hz 93.1 dB port-limited 117 W
15 Hz 98.9 dB port-limited 84 W
18 Hz 103.6 dB port-limited 253 W
20 Hz 106.3 dB port-limited 498 W
25 Hz 109.0 dB amp-limited 900 W
40 Hz 110.9 dB amp-limited 900 W
63 Hz 112.8 dB amp-limited 900 W

Half space, 1 m, no room gain — add 6-12 dB below 25 Hz in a real room.

I kept the 4" anyway, and here's why. Port length scales with area, so with diameter squared. A 5" port for 15 Hz in this box needs 52" and the cavity is only 45.75". A 4.5" needs 40", which fits, but leaves the inner mouth 5.75" off the bottom cap — less than one and a half diameters, close enough that the mouth starts loading against the cap. A 6" is off the table entirely at 76". So 4" is what physically fits at this tuning, and if I wanted more clean output down there the honest move would be to tune higher, not to fight the port. I may end up doing exactly that — the port length is the one thing that's trivial to change later. The amp is going inside, and I've talked myself into it


The 1200AS1 is going on a shelf in the box rather than in the wall. The datasheet is specific about cooling: 0.8 K/W reference heatsink, 40°C ambient limit passively, PSU shutdown at 95°C, and 27 W dissipated at idle with 80% efficiency at rated power.

Sealed inside the tube, the whole cabinet becomes the heatsink. External surface is about 1.84 m², and through the cardboard wall with natural convection on both sides that's roughly 3.4 W/K, which gives:
27 W idle internal air 30°C baseplate 52°C fine
60 W sustained internal air 40°C baseplate 88°C at both limits
120 W sustained internal air 57°C baseplate 153°C shuts down

Bolted straight to MDF with no heatsink it doesn't even survive idle — the module's own baseplate into still air is about 4 K/W, which is 143°C on 27 W. So a real heatsink is going in there regardless.

Where it lands is that idle is comfortable and sustained high output isn't. Bass has enough crest factor that programme material rarely sustains 60 W of dissipation, but that is genuinely the argument I'm making to myself and I'd be interested if anyone has run a 1200AS-series module sealed in a sub long term. The clean fix is an aluminium plate let into the tube wall with the fins in room air, and I don't want to break the cylinder. Compromise is the biggest heatsink that fits, sited under the port's inner mouth but offset from the centreline — that's the only place in the box with real air movement, and it moves hardest exactly when the amp is working hardest. Construction


Three internal braces: an amp shelf at 16", a brace at the port's free end at 27.4" that grips the tube above the flare rather than at it, and one at the port's mid point at 38.4". Port runs all the way up to the top baffle and exits through it, driver fires down through a 2.25" laminated bottom cap.

The end caps are a flush outer disc at tube OD + 2 mm so the vinyl wrap finishes level with no lip, plus inner discs that slip inside for glue area. I want it reading as one continuous cylinder rather than the usual chunky wood overhang — the legs overhang, nothing else does.

Two things I'm being careful about. Form tubes are wax impregnated and porous, so the inside is getting two coats of dewaxed shellac before anything else goes on, and no PVA anywhere — it won't bond to the wax. Polyurethane construction adhesive on the joints. And the port is butt jointed with slip rings over it, so both ends get cut dead square and deburred inside; a ridge halfway down a port that's already near its velocity ceiling is exactly what I don't need.

The tripod is a mild compromise I've made my peace with. Three legs tip at about 12.7° against 17.7° for four, because the inscribed radius of a triangle is R/2 where a square's is 0.707R — but three never rocks on an uneven floor, and nothing is going to lean on it. What's next


Cutting discs this week. Once it's together I'll run an impedance sweep to find where it actually tuned — the two inputs I'm least sure of are the driver's displacement, which Dayton doesn't publish, and the flares' end correction, which moves Fb by a couple of tenths either way. Worth noting the box air runs 8-18°C above room with the amp inside, and that alone lifts Fb another 0.2-0.45 Hz, so I'll be measuring it warm.

]]> Build stories Hdale85 https://www.htguide.com/forum/mission-possible-diy/build-stories/961267-sonosub-build-16-15-5-id-tube-ss12-22-15-hz-replacing-an-sb-1000 https://www.htguide.com/forum/mission-possible-diy/woodworking-tools-techniques/961257-denim-insulation-is-back Mon, 10 Aug 2026 00:54:11 GMT https://www.homedepot.com/p/Henry-R-13-ULTRATouch-Recycled-Denim-Insulation-Batt-15-in-x-93-in-HER13445/330252223 https://www.homedepot.com/p/Henry-R-...3445/330252223]]> Scareurpasenger https://www.htguide.com/forum/mission-possible-diy/woodworking-tools-techniques/961257-denim-insulation-is-back https://www.htguide.com/forum/mission-possible-diy/development-tools-techniques/961244-what-makes-you-close-the-sim-and-open-a-spreadsheet Sun, 09 Aug 2026 09:13:53 GMT
Most of my time has gone into getting the physics right rather than polishing the interface. I've been checking the results against published anechoic measurements, instead of only comparing them with other simulators. Two programs agreeing doesn't necessarily mean either one agrees with the real speaker, and testing that has caught me out more than once.

I'm curious about the parts of your own workflow that existing software doesn't handle well.

What do you still calculate by hand or keep a spreadsheet for — not because you enjoy doing it that way, but because the software doesn't give you a better option?

Are there any results you routinely double-check because you don't completely trust them?

What did you have to learn from forum threads rather than from the program itself?

And is there any variation or "what if?" idea you regularly skip because setting it up would take more effort than it's worth?

I'm not looking to pitch anything or collect a generic feature wishlist. I'm more interested in the awkward parts of the process that people have simply learned to work around.

If this turns up anything useful, I'll come back and share what I learned — and what I ended up doing about it.]]> Hdale85 https://www.htguide.com/forum/mission-possible-diy/development-tools-techniques/961244-what-makes-you-close-the-sim-and-open-a-spreadsheet https://www.htguide.com/forum/mission-possible-diy/design-studies-theory/961242-how-high-can-an-isobaric-midwoofer-pair-reasonably-be-used Sun, 09 Aug 2026 03:05:50 GMT Is there any inherent reason a pair of 6.5–7" midwoofers in a conventional isobaric arrangement can't be run cleanly to around 2 kHz?

Assume both drivers individually work well to 2 kHz. I am specifically wondering whether the isobaric arrangement itself — trapped air between the drivers, coupling, spacing, cavity resonances, etc. — creates problems as frequency rises, and what determines the practical upper limit.

It has obviously been done. The Totem Mani-2 reportedly ran its iso pair to around 3 kHz, and I just found the Dellichord FR6, a current 6.5" two-way using two identical SB Acoustics midwoofers isobarically, a passive radiator, and a 1.7 kHz crossover.

I am going to build a test box and compare a single driver directly against the iso pair, but I would be interested in any measurements, experience or technical explanation of what happens to an isobaric pair as frequency increases.

Please keep this to the question of using an isobaric pair into the midrange. I understand the usual iso tradeoffs and alternatives. “Use a different driver,” “use DSP,” “there's no reason to use isobaric anymore,” etc. may all be perfectly reasonable advice, but aren't the question I'm trying to answer.

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https://www.soundstageaustralia.com/...s-fr6-speakers]]> DaveFred https://www.htguide.com/forum/mission-possible-diy/design-studies-theory/961242-how-high-can-an-isobaric-midwoofer-pair-reasonably-be-used https://www.htguide.com/forum/dedicated-theaters-displays-remotes-computers/htpcs-computers-remote-controls-and-other-electronic-devices/961217-quick-question Sat, 08 Aug 2026 00:32:26 GMT ]]> HTPCs, Computers, Remote Controls, and other Electronic Devices Alaric https://www.htguide.com/forum/dedicated-theaters-displays-remotes-computers/htpcs-computers-remote-controls-and-other-electronic-devices/961217-quick-question https://www.htguide.com/forum/mission-possible-diy/project-development/961100-the-satori-mta-a-two-way-but-with-a-checkered-past-and-lots-of-different-dna Sun, 12 Jul 2026 20:48:43 GMT This is a project that you might say has multiple ancestors and source of design DNA, as far back as 20 years ago, and as recently as six months ago. And, just to get this out of the way, it's NOT another 6-1/2" two way, but rather, an upgrade? A 7-1/2" two way... and with well pedigreed parts.

And it's being driving partly by the desires of one long term HTG member, Darryl Glenn, and by my own speculations and itches.

So, what are the historical antecedents? (This is sort of like answering a question such as, "who in your family do you resemble?" Which can be very complicated, or obtuse, if who you resemble was never living when you were born, and a key example goes back to the mid 1800s, in my case). But no time span like this.

So, I'd list these items as being in the genetic soup of this project:

• M8ta, circa 2006/2007, for a roughly 8" two way in a tower format speaker similar to Avalons- too bad Charlie Hansen passed nearly 10 years ago, he could tell you about the prototype speakers I gave him when my development and business partner died from an aortic aneurysm when I was away at CES in 1980 scoping out the competition. Charlie was working for me in a small professional audio outfit in Boulder Colorado while attending school at CU. More than 45 years ago.
• NatalieP, also a two way, with smaller drivers, and an unusual crossover with a low turn-over frequency to get the most out of an Usher tweeter made for PE, the RS28a.
• SMJ Audio Calliope, with the SB Satori MW19P-8, and the Peerless DA25TX-008 Corundum dome tweeter. IN and Out of availability, never goes out of style.
• Ardent D, for overall enclosure concept, materials, and finishing options (possible to get a nice result with just golden Watco oil and wipe on polyurethane. Some modifications to dimensions and configuration, of course.
• Modula Magnifique, based on the concept of a Bessel fourth order high pass, given specific requirements for driver Qts, enclosure size, etc. are made. Complete analysis still pending.

So, I'd say the enclosure details are pretty close to being fully nailed down, with one special option set-

• for the more budget minded, a reflex port in the base
• For those favoring passive radiators, a pair of the new Dayton SS10's might be optioned... or the RSS265PR. The SS10's if you want a 4th order Bessel high pass. The RS265PR if you want options for a flatter measuring system, with a heavier low end.

For now, a few renders of the enclosure.


Just the facts, ma'am, as seen with basic visualization.



An X-Ray view of the ported version:





And a very basic rendering visualization:




For reference, this build will be done similarly to the Ardent D:

• Maple ply front panels, as used for piano tuning plates
• Maple ply top panel
• Bamboo board, not ply, the kind made with 3/4" wide strips, for the side walls and back.
• Back from combination of bamboo board and 1/2" Baltic Birch Ply, new old stock in my case.
• Internal bracing materials primarily from 1/2" and 3/4" Baltic Birch Ply.

]]> Project development JonMarsh https://www.htguide.com/forum/mission-possible-diy/project-development/961100-the-satori-mta-a-two-way-but-with-a-checkered-past-and-lots-of-different-dna