FWIW, the way one solves the various cheap cardboard tube issues [as opposed to the much better constructed Sonotubes originally used] is to mass load them to quell spurious resonances same as any other speaker and being a tube, this historically negates any need for further bracing, though with some of the newer super high power sub drivers with their extremely long strokes, this may no longer hold true for all drivers.
You could just [commerical grade] Velcro a very heavy top plate to it as I did with low power drivers, but the best way is to tie all the plates together and to the driver, each 'section' under a slight tension to compress/clamp it all together to form a single device using the same basic construction as the popular 'Flexy' audio rack, though of course use whatever size threaded rod is required to mount the driver and pvc pipe or similar tube spacers in lieu of all the extra hardware to make it easy to get the correct pre-loading and cosmetics in the exposed sections down to the floor [if applicable]: Easy Flexy Rack
FWIW, a single large vent is more efficient [shorter] than multiples.
GM
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Now that is some bass! Wish I had that sort of space.
That is a bit more my speed. I like the dual-purpose as a table, I might steal that idea.
If you look at the lamp in my first post, it is actually built in a similar way which would make it easy to compress the tube a bit. I may still try to go this route, I did realize though that my "10 inch" tubes were more like 11 inch tubes. So I will have to go to the store with a ruler, no big deal.
As to the ports, aside from being shorter, is there any other advantage to a single big port in terms of SQ? Only reason for 2 is to make extra sure it wont chuff, and I can get 3 inch cardboard tube for free so that is why I chose 3 inch.
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The calculations for a single port may be easier, depending on what software you are using. My sub is 24" diam sonotube (sourced from local industrial contracting house) with a single 6" Schedule 40 PVC (the extra thick stuff) pipe as a vent. Keep port velocity under 0.1 of the speed of sound and you should be OK to prevent chuffing. The entire sub is about 28" tall.
Is this online calculator even remotely accurate for air speed? I will be powering it with a TPA3116 mono board, so "100W".
LinearTeam
I was looking at the other drivers in the Polk DB line as well. Am I crazy, or can the DB1040DVC hit an f3 of around 19Hz with only 4.5 ft3? That seems incredibly small for such a deep f3.
From the datasheet
Fs = 35Hz
Re = 3.4 ohm
Le = 5.1mH
Qms = 5.4
Qes = 0.66
Qts = 0.62
Vas = 1.07 ft3
Sd = 54.25 in2
Xmax = 9mm
VC Dia = 2in
Efficiency = 88dB/series
LinearTeam
I was looking at the other drivers in the Polk DB line as well. Am I crazy, or can the DB1040DVC hit an f3 of around 19Hz with only 4.5 ft3? That seems incredibly small for such a deep f3.
From the datasheet
Fs = 35Hz
Re = 3.4 ohm
Le = 5.1mH
Qms = 5.4
Qes = 0.66
Qts = 0.62
Vas = 1.07 ft3
Sd = 54.25 in2
Xmax = 9mm
VC Dia = 2in
Efficiency = 88dB/series
Married, and at least one small child, a toddler who kept putting stuff into the speakers.....one of the reasons that he sold the tube subs and built the enclosed subs. The enclosed boxes also seemed to put less bass into the neighbors identical house for some reason.
I noticed a strange phenomenon with some OB speakers that I built. They used 15 inch woofers in antique radio consoles with no back cover. I could crank some Pink Floyd DSOTM to wall shaking levels inside my house, and the bass was audible in the street outside, but not objectionable. It was however quite loud INSIDE the living room of the identical house across the street. It was not loud in the non identical house next door. Only certain notes, the ones that shook the walls in my house, were loud. The OB woofers obviously excited some kind of resonances in these cheap houses. This did not happen with enclosed boxes played at louder levels.
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I never met the kid, but Shervin's story was "my kid kept stuffing things into the opening".
I believe most of Shervin's speaker use revolved around HT application, and much of the LFE energy is at the low frequency extremes. Exactly why his speaker choice affected his neighbors house, I don't know.
In my case, the house across the street was about 120 feet from mine, while my neighbor's was about 15 feet away, but a totally different floor plan.
It was quite eerie to hear and feel the bass from certain notes played on my OB speakers, with open back facing a wall, come from the same wall in her house. These sounds did not come from anywhere else in her house. These were poorly constructed houses with thin 3/8 inch sheetrock on stamped steel studs. At first she thought she had rats in her attic until her son noticed the rhythmic pattern that matched the sound coming from my house.
The volume in my house was loud, but not excessive. A 15 watt tube amp into 96 db speakers.
It has greater efficiency, ergo puts out more bass than multiples, so depending on your definition of port SQ, the latter is probably more technically correct since all that extra friction is over-damping the vent, though of course if the single vent is efficient to the point of audible 'ringing' it can be critically damped and often will still have slightly more output, but down low not enough to be obviously audible.
Bottom line, easier to make, takes up less space and has more tuning flexibility.
Carpet roll tubes are very sturdy and are normally just trashed or recycled, so a good, free source of large cardboard tubes and for high power there's 8" -up concrete former tubes.
GM
Hmm,
Will have to check at the local hardware stores to see if they have any carpet roll tubes. I get my 3 inch tubes from work as core rolls for various materials.
Will have to weigh the pros and cons of a single large port vs multiple small ones for my application. The main con being that for a larger than 3 inch port I have to either make the footprint larger, or move the port to the back of the box and add ventilation for said port. As it is I can fit my dual 3" ports on the face plate so the driver and ports are both on one plate.
I should be able to just build another ~3.5in gap behind the port side though.
Will have to check at the local hardware stores to see if they have any carpet roll tubes. I get my 3 inch tubes from work as core rolls for various materials.
Will have to weigh the pros and cons of a single large port vs multiple small ones for my application. The main con being that for a larger than 3 inch port I have to either make the footprint larger, or move the port to the back of the box and add ventilation for said port. As it is I can fit my dual 3" ports on the face plate so the driver and ports are both on one plate.
I should be able to just build another ~3.5in gap behind the port side though.
FWIW, I got mine from the many local installers.
Ideally the vent will be at the top; if at the bottom, then there will be more ripple, so more stuffing required, hence the extra loading due to close coupling + floor loading is often [mostly] damped out.
It could come out the top back of course, but only if it's short enough, which I doubt, and sharp turns in a vent are normally a no-no, so would need to go in at an angle to keep the other end away from the opposite wall at least one diameter.
GM
Ah, yes, top is what I meant by back. Back face of driver = top of box. I think I should be able to get away with 36in of the 10in diameter tube I have for the enclosure volume I need once I account for the port volume and leave a bit extra for driver volume. Then another 3.5in or so on each end to let the driver and ports breathe.
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