[JLM]

Looking to add a swarm (refer to Duke LeJeune of Audio Kinesis) of 4 subs on the cheap.    I had a pair of 6 cubic foot mass loaded transmission line (MLTL) cabinets (passive) with 8 inch woofers in the 80's that I loved.  But they were too much for residential use (rated 114 dB at 17 Hz) but were so fast/tight/musical/accurate.

So my "babies" are single driver transmission lines, rated 25-20,000 Hz that work very well in my Cardas golden cuboid room (8ft x 13ft x 21ft).

Just picked up a pair of stand-mounts (active Dynaudio BM5 Mk III, see review) that need subwoofer help and thought I'd try a swarm.  But $3000 for a swarm is overkill for speakers I paid $850/pair for.  Note that the Dyn's reach 42 Hz and a maximum of 118 dB/w/m.

So is there small subs (hopefully MLTL) that can reach 20 Hz?  With four of them in the above room I wouldn't need monster spl's.

TIA

[JLM]

OK, so I'm underwhelmed by the response.  But I found one small MLTL sub:

Earthquake Sound FF6.5 6.5-Inch Front Firing Subwoofer ($220, 14"x8"x10", 28-180 Hz).
 
Doesn't look very promising IMO, but thought I'd post it just in case anyone was interested.

[JCS]

Well, you ask what seems to me impossible.  'Small' & 'sub' & 'TL' don't fit in the same sentence.  To develop real bass requires the TL to have significant length (for quarter wave action), even when you add mass loading, which I admit will shorten the TL some. I don't think of a 6.5" driver as serious bass; smallest I would go is 8".  By folding a couple times you can turn length into depth, but it probably won't fall in the category of small. 

I have built a few Metronomes--quadratic taper MLTL (see DIYaudio.com thread titiled; The Metronome).  Using a 6.5 Fostex full range drivers, they were about 66" tall (but small foot print) and had an f/10 around 38 Hz--clearly not sub territory, and hardly small.

[walkern]

If you are looking for fast, tight, musical and accurate in a compact sub you may need to resort to sealed enclosures instead of transmission line loading.  For a 'swarm' I'd check out the 'bucket sub' (some info here: http://www.transcendentsound.com/Subwoofer.html.  You can throw together 4 of these puppies for around $300, and then you'll need to find a good amp (or two) to drive them well (something like this from Parts Xpress should do the trick http://www.parts-express.com/bash-300s-digital-subwoofer-plate-amplifier-300w-rms--300-750.  Sealed enclosure subs roll off at a slower rate than vented subs, and with room reinforcement you can get pretty good extension (maybe not down to 20hz, but probably down to 25hz). 

I have not tried these subs myself, so I cannot speak from experience.  I have found the guys at Transcendent Sound to have pretty good ears though, so it might be worth checking out.  I VERY much like GR Research servo subs.  They are reasonably compact (1.5 cu foot for a sealed 12"), play very low with amazing speed, control and accuracy.  Trying to do a 'swarm' of them would be more expensive because of the specialized nature of the drivers and amps.

Good luck

[ohenry]

I have four buckets and they are very good. Also, I highly recommend a sub amp from the Crown XLS series, they trounce other class D amps that I had.  The Crowns have built-in adjustable low pass filters, so they are simple to implement and one of the higher powered models can handle four buckets.  I use two XLS 2500's, but it is overkill to run a total of 4800 watts into four ohms.  Good cheap fun. 

[JLM]

Sorry guys, but I'm in a finished room, not an ice shanty.  So bucket subs are OUT.

JCS,

Wouldn't using a woofer make a big difference from an extended range driver?  As I mentioned, my old Fried Model M MLTL's with 8 inch driver in 6 cubic foot cabinets were enough to each serve 10,000 cubic foot of space.  If I simply scaled down I'd be looking at 0.4 inch driver in a 0.3 cubic foot MLTL, ridiculous. 

[ohenry]

Sorry guys, but I'm in a finished room, not an ice shanty.  So bucket subs are OUT...

They really aren't all that bad especially if placed out of the way. 

...If I simply scaled down I'd be looking at 0.4 inch driver in a 0.3 cubic foot MLTL, ridiculous.

I do like tl bass and hope you are successful finding a reasonable trade off between size, output level and frequency response.

edit:
One other thought; I have two small TBI subs (Magellan VI, I think) that are good sounding and look nice.  A swarm would be pricey, but one or two can fill the room with bass.  They are low-mass and fast, and mate well with single driver speakers... and the aesthetics are fine.  I have the passive model allowing for greater placement flexibility.

[JLM]

Yes, I thought of the TBI subs, they'd be perfect.  Obviously I have a hard enough time understanding TL theory, but how the TBI's actually work is mind blowing to me.  But you're right about them - the price for 4 of them plus amps would exceed Duke's swarm price.

Oh well, there's always cheaper alternatives.  OTOH why spend money/space to smuck up the sound?  While trying to maintain F3 of 25 Hz or lower and 16" maximum width the better/higher priced options include the sealed Rythmik L12 ($2156/four via Ascend Acoustics, 14.5" cube, F3=18Hz) and SVS SB-1000 ($1900/four, 13.5" cube, F3=24Hz).  Next down on the quality/size/price scale is the vented Hsu STF-2 ($1276/four, 17"x14"x17", F3=25Hz).  Below that is a myriad of options including the sealed BIC America H-100II ($872/four, 17"x15"x18", F3=24Hz), and the vented Dayton Audio SUB-1200 ($592/four, 17"x16"x18", F3=25Hz) and they have sales all the time.  All of these seem like overkill in terms of volume for my application.

[JCS]

JLM,

You can't just scale a cabinet for a smaller driver.  Using a woofer rather than a FR driver enables you to tune lower to get bass, but bass wavelengths are long & you need a long path to get the quarter-wave action. 

Take a look at the Tang Band W6-1139SIF 6.5" driver ($48.32) on Parts Express.  Fs=35 Hz; Vas= 0.42 CF; Qts= 0.4; Sens= 83 dB/2.83 v; Xmax= 11.5 mm.  Looks like a nice little driver!  Check out the recommended box sizes; small vented box will have F3 only 38 Hz.  No where near what you want.  I don't have time to calc a box for an MLTL, but if you put it in a BIB (sort of tapped horn) tuned to 1/2 Fs you should get the extension you want w/ SPL sufficient for a modest sized room, assuming you aren't hoping to recreate explosions for HT.  HOWEVER, the enclosure (which needs to be against a wall because you need wall & floor or ceiling to act as part of the horn) will be 7.5" w x 9.5" d x 97" h.  An MLTL could be shorter, but it still needs to be pretty large to hit F3=25 Hz.

[JLM]

Yeah, I know that comparison was silly, but again thinking back to my old MLTL's that were so powerful, musical, and plenty deep.

[JLM]

Follow up:

A guy who apparently knows how to run the software, plugged in a 8" subwoofer driver and came out with an 11 foot long TL to reach 20 Hz.  As mentioned above those pesky laws of physics dictate length as the prime criteria for reaching a given frequency.

So I've given up on TL for a small/affordable sub.   

[Mark Korda]

Hi Guys,
     I got all charged up when I saw the 8 inch Peerless subwoofer 5 gallon bucket project. I made one and bought the Peerless sub from Parts Express. It came out great and to spec but I gave up and never pursued the hookup. Why....Because I've mixed cement all my life from working at installing tombstones to house reconstruction.
     When house painting a cement most used for repairs is Durobond. It's like drywall mud but you mix it up and it dries fast, some types in 20 minutes. To make a batch I use a 5 gallon bucket and some water and mix it up until it resembles Skippy peanut butter. To make a second batch and use the same bucket you simply give the bucket a small karate chop and the dried Durobond comes out very easily and almost perfectly in the shape of the inside of the bucket.
     With the way a sub woofer works and all the years I've read about speaker cabinet vibration I just let the project fade.
    I'd like to hear from you guys who made the bucket sub and see if you have a rattling bucket or not. When I did build mine I put big gouges and scratches on the inside of the bucket to give the cement, or Durobond some sort of anchor, kind of like scuffing up shiny paint so the new coat will adhere. I have the plans for the TUBA sub in AudioXpress if you need a copy. It's a long TL sub that was built 2 ways. One was behind your couch and the other was a coffee table affair....Mark Korda

[Abby356]

JLM,

We have similar taste in single driver sound (ie F200A) and I have experimented with a couple of options that I think may work for you. I agree that it takes a fast sub, and multiples, to keep up. I use the F200A in OB so don't have the full benefit you get with the Brines cabinet.

The TBI subs do work. I have a pair myself and a close friend bought a pair on my recommendation. They do fetch a fair sum but can be found used and become a much more affordable option.

Volvotreter has a nice small folded tapped horn for the Tang Band W6-1139 variants. I have built 4 of these (when that driver was only about 25 bucks) and they perform amazingly well.
 
http://wp.volvotreter.de/projects/th-2/the-tangband-38hz-horn/

The plans are available in that link. I built the double folded version, as the form factor is easier to hide.

Also Erich with DIY Soundgroup did a similar design out of void free baltic birch a couple of years ago.

http://www.diysoundgroup.com/anarchy-th.html

This design also works with the Tang Band drivers and Exodus Anarchy woofer. I have two of these boxes and the Exodus drivers tucked away. You could probably convince Erich to make some more flat packs or he might know who has a few. He's very helpful.

All three of the designs are very reasonable in size and could be veneered or painted to blend with any decor.

Let me know if I can provide any more info.

Regards,

Daniel.

[JLM]

Thanks Daniel, glad to find another F200A owner, but not interested in a 38 Hz "sub" (my F200A based TL speakers do much better than that and my Dynaudio BM5 MkIII have F3 = 42 Hz).  IMO a real sub reaches 20 Hz (just don't need high spls with 4 of them in a 2,100 cubic foot room).  And not interested in the front horn loaded sub (still doesn't go deep enough and a bit big - have got plans for a sub that performs as well in a $130 passive sealed pre-cut 12 inch MDF cube.)