The tube that swallowed Seattle

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Vasubandu

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The tube that swallowed Seattle
« on: 17 Feb 2018, 09:06 pm »
I am relatively new to all this, but that hasn't stopped me from thinking. My wife of 30 years just sighs and finds a book to read when I tell her I have been thinking again.

My observation is that over the last 20 years, driver size for subwoofers has increased considerably. 12 inches used to be a big driver, and today it is a starter.  But over the same time, enclosure size seems static or even shrinking.  As I understand the first law of thermodynamics, matter can be neither created or destroyed, so where is all that air coming from? My suspicion is nowhere, and that more power is being used to compensate.

So I decided to make a subwoofer that had the recommended or required space.  And I decided to go big with it.  The WAF factor in my house is pretty lax because the home theater is in the basement, which is my space.  But I still wanted to avoid creating a monstrosity. Science generally says that round or curved objects are perceived to be smaller that square or rectangular objects of the same volume.  So I decided to round.  And to really test the idea, I decided to go with 2 24-inch SI-24 Mk II.  In a ported enclosure, they require 16-20 cubic feet each, so 2 in an opposed system are 32-40. 

In a box that would be a 2x4 footprint 5 feet tall.  Even in my house, that is going to raise some eyebrows. But a 3 foot wide column six feet high is just a large decorative feature, especially if it is covered with a nice finished veneer.  Putting two drivers in it is going to require one at the top and one at the bottom.  Sonotubes are made of cardboard, and No matter how think it is, I still am not a fan of putting a 115 pound subwoofer on top of it. I also am just morally opposed to the idea of a cardboard subwoofer in the first place.

An easy alternative exists.  Curved plywood is a readily available commodity, and it is easy to get half circles in most typical diameters. I can create my 3x6 tube of 5/8 inch plywood for under $500.  That is still a lot of money compared to a sonotube, but worth the cost as I see it.

My questions for the group are whether this makes sense and if anyone else has gone down this path?  The HS-24 are rated at 2000 watts, and a SP1-4000-HT amplifier from speakerpower.net could cost $999 and provide 2000W channels. Makes for an expensive sub, but seemingly an impressive one.

My primary purpose here is to experiment and learn, not to make the best subwoofer I can. I can easily reuse the parts for that later. Any thoughts would be welcome.

Doublej

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Re: The tube that swallowed Seattle
« Reply #1 on: 18 Feb 2018, 12:01 am »
As an alternative to making the biggest, baddest subwoofer you can, considering changing your objective to obtain the best bass you can possibly get in your room.

This might lead you down a different and to a more fulfilling outcome (or not).

Happy experimenting!

Mike B.

Re: The tube that swallowed Seattle
« Reply #2 on: 18 Feb 2018, 12:17 am »
Where's my book? How big of space is the room these will be in? If an average size room, I think you are going overboard. There are commercial subs available in moderate side cubes which can fill a room with flat response into the teens. I own a JL Audio Fathom 112 sub. It has DSP and you measure the room with the microphone provided at your listening position. It's interal amp is rated at 1500 watts.  It does two things. Reproduces the lowest bass recorded and does it cleanly thanks to the room correction. This is one 12" size driver. SVS is another manufacture offering similar performance.

JLM

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Re: The tube that swallowed Seattle
« Reply #3 on: 18 Feb 2018, 12:27 pm »
Yeah, what Mike B. said.  This seems more like a mad scientist effort than one based on a full understanding of physics.  Thermal concerns do affect driver performance but being in a small/sealed cabinet versus something more open would have almost no consequence.

Nothing wrong with Sonatubes (designed to hold wet concrete at fairly extreme depths, so can easily handle audio).  Check out the old Hsu and SVS tube subs that used them.  And BTW they were smaller and rated down to 16 Hz using a single driver.  Also note that you can find many reports of big subs shaking the entire house (wouldn't exactly be wife approved).

I run a 10 inch driver in a 14 inch cubic cabinet with a 300 watt amp in my 8ft x 13ft x 21ft audio room using DSP to match volume to my main speakers.  In my home theater (HT) system I picked up a 15 inch driver in a 18" x 18" x 24" ported cabinet with a 500 watt amp in my 8ft x 14ft x 17ft room and run the volume control at 15%.  Note that I'm a big believer that bass reproduction is foundational to high fidelity but not a bass-head.

Current thinking dictates that for the most uniform in-room bass you need multiple subs (that can be smaller).  Room gain makes up for the very deepest bass response (no need to look for F3 of say 20 Hz if you want to reach 20 Hz in-room).  Sealed subs are recommended for music or music/HT use.  Ported are preferred for HT but use correspondingly much larger cabinets.  Simple equations can be found to size cabinet and port for either design.

charmerci

Re: The tube that swallowed Seattle
« Reply #4 on: 18 Feb 2018, 01:09 pm »
Here on AC there's this - a bit smaller than what you are proposing.

http://www.audiocircle.com/index.php?topic=155412.0

http://gr-research.com/diysubwooferkits.aspx



SteveFord

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Re: The tube that swallowed Seattle
« Reply #5 on: 18 Feb 2018, 01:16 pm »
Might I suggest a different approach?
The TRW-17
http://www.eminent-tech.com/

A little on the expensive side, though.

Doublej

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Re: The tube that swallowed Seattle
« Reply #6 on: 18 Feb 2018, 01:59 pm »
On the other side of the price curve you could do a swarm of bucket subs.

THROWBACK

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Re: The tube that swallowed Seattle
« Reply #7 on: 18 Feb 2018, 02:21 pm »
You didn't say whether the sub was to used strictly for HT or whether you wanted it for music as well.

If both, you would do well to pay attention to HAL's thread. Great sound, well thought-out approach.

The Megaliths open baffle line array speakers
http://www.audiocircle.com/index.php?topic=142716.msg1522868#msg1522868

Also, check this one:

GR Research
The quality level of bass reproduction... exceeds any other...at any price.
http://www.audiocircle.com/index.php?topic=155412.msg1666245;topicseen#new

Note that both approaches use the GR Research 12" servo woofers. I have experimented with lots of woofers: everything from small acoustic-suspension AR types to a 24" Hartley mounted in the wall (infinite baffle) and in a 2x2x6' cabinet (transmission line). To my ears, the GR servos have them all beat.




Rusty Jefferson

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Re: The tube that swallowed Seattle
« Reply #8 on: 18 Feb 2018, 05:30 pm »
....My primary purpose here is to experiment and learn, not to make the best subwoofer I can. I can easily reuse the parts for that later......
That's what matters.  I say go for it, you're going to learn through diy.  How it sounds (and maybe looks) to you in the end is what should be important.  :drums: :guitar: :rock:

who?me?

Re: The tube that swallowed Seattle
« Reply #9 on: 6 Apr 2018, 05:46 pm »
My Scientist is a good thing in my book