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Old 13th November 2016, 03:26 AM   #1
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Question Best Enclosure Options for LFE in a Limited Space?

My first post...

What sort of enclosures - and I use that term loosely - are best for generating reasonably clean response down to around 14-16Hz, and do it in a relatively small area? Large enclosure volume is okay; I just can't take up the 40+ square feet of floor space like I originally wanted to.

My first choice was a Bass Canon (Acoustic wave canon is a great discussion on the topic). It seemed ideal for giving the deepest bass without excessive booming and muddy sound, but my wife & daughter vetoed the 26' of 18" sonotube that I wanted to run down one wall of the basement/theater.

I've considered the possibility of a transmission line, but the discussions and articles I've read about them here and elsewhere all seem to disagree on everything except the fact that they're difficult to design & build.

Another option might be an Extended Bass Shelf design to get the really low frequencies. Their large volume isn't a problem since I plan on putting the sub behind the screen, which is stretched across a corner of the room.

I've also considered a folded horn. I'm not certain, but one that will handle 15 Hz may take more cubic feet than I have.


My mains are good down to around 50Hz. I've got a decent 15" professional sub, but it's really intended for live music and isn't good for much below 30-35Hz.

My reference and target for this project is the prolog sequence of Fellowship of the Ring; the part where Isildur cuts the ring from Sauron's finger and it falls to the ground. Sauron explodes and there's a long decreasing frequency sweep as the blast wave sweeps across the battlefield. It sounded amazing in theaters, but my sub checks out at least a couple of seconds - and I think more than a whole octave - early. I'm guessing the sweep bottoms out at around 15Hz, which is part of the reason I chose 26' for the bass canon I wanted to build.

I started planning this at least 10 years ago, and went so far as buying a 21" driver that I'd still like to use if possible. ...Then life happened and I'm just now getting back to it.
The driver is a Madison Executioner X-21 with these specs:
FS 31 Hz
VAS 14.67
SD 298
Qts 0.982
BL 21.18
Re 7.1
X max 0.75" (+/-)
An old post by robotnation - http://www.diyaudio.com/forums/attac...ecutionerx.jpg - gives more.

It may or may not be the ideal driver, but I chose it for the massive volume of air it can move and it's (relatively) low cost at the time.


Last question: The Qts for this driver is a lot higher than most. Despite reading quite a lot about the T/S parameters, I'm still confused about how Qts interacts with various types of enclosures. Is .982 really good for something like a bass canon, or really bad?

Thanks!
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Old 13th November 2016, 11:02 AM   #2
Scott L is offline Scott L  United States
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Location: Knoxville, TN
Default how to build a bass box enclosure ?

how to build a bass box enclosure ?

I decided the best answer I could give, would be not to answer, but rather guide you to start learning on your own.

Here's a way to start:

https://www.google.com/search?q=How+...+box+enclosure
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Old 13th November 2016, 11:08 AM   #3
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The high Qts is a problem. You could put it in a very large sealed enclosure and get a Qtc ~1, which will give a slight bump in response around 40Hz.

I'd probably go for a, say, 200L sealed box (or however big you can build), and EQ the result. Rooms will always do nasty things to any carefully designed response curve, so its worth having EQ anyway.

Chris
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Old 13th November 2016, 12:14 PM   #4
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Location: Toronto and Delray Beach, FL
Why not just get one of those vibrating things you screw to your furniture? Makes more sense.

A lot of sub-sub projects bring joy to builders... which is because humans mistake harmonic distortion coming from the speaker for the production of the fundamental notes. I bet a lot of tapped horns playing loud bass guitar and double-bass notes at 80 Hz result in comments about the great deep bass. Without a mic, few builders have the acuity to actually know what notes they are "experiencing".

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Old 13th November 2016, 04:26 PM   #5
TBTL is offline TBTL  Germany
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What are the maximum dimensions you can fit?

Putting a high Q woofer in a ported enclosure is no problem if parametric EQ is available. While other woofers might work better in a ported enclosure, if you have to use this woofer it's better than putting it in a sealed enclosure in terms of sound output. More sophisticated enclosures sometimes can squeeze a few dB more out of the woofer for a given enclosure size and extension, but those differences are small.
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