[oz_audio_todd]

Ok, not sure where else to ask this, so here it is:
Is there any reason why Subwoofers are not all designed to be be pushed hard into corners or hard up against walls (and I dont mean the boxes, I mean the drivers (and ports) are firing against the walls and almost touching them)?
I figure that this would make them more efficient (a sort of horn loading) and mean there should be less destructive interference from bounce back off the walls(?).
Im sure its not that simple, so wondering if anybody can tell me what I am missing here?

[JLM]

1. Lots of ways to skin the cat (other ways to enhance performance from a given wattage/box size).

2. Many sub designs do use down firing drivers in their designs and several full range speakers are designed for placement along walls for bass reinforcement.  Infinite baffle subs are built into floors, walls, and ceilings.

3. That is the premise behind Klipschorns (invented before stereo).  Other than size and cost concerns, one of the factors that has hurt their sales over the years has been the lack of two adjoining/available/well suited corners to allow them to "work their magic" in so many rooms.  That can be a bit hard to fathom at first.

BTW my fave sub design would be in-phase, back-to-back woofers in in MLTL.  Because of the efficiency of involved with two drivers and MLTL the woofers could be quite small (5 - 8 inch I'd guess for most installations).

[oz_audio_todd]

OK, can we get some more info on your favourite sub (some sort of transmission line??)
Do you happen to be able to name any of these subs designed to be pushed up against the walls though?  (and its nice to know that the thought is worthy of commercial application    )
Yes, I know what IB subs are, pretty sure my strata would fail to embrace the pluss's though! 
yeah, not willing to run with the size of actual bass horns, but if the walls can be used successfully as a substitute, that I can live with! 
Thanks, Todd

[JLM]

Sorry, commercial MLTL subs are nearly impossible to find.

I said "would be".  Back in '79 I DIY'd a pair of 6 cu. ft. MLTL cabinets that passively each used an 8 inch woofer.  Wonderful sound, but too much of a good thing (rated 114 dB at 17 Hz) and I believe it.  Sounded great in a 20,000 cu. ft. chapel though.  If you search for transmission line speakers you'll find all kinds of MLTL applications.  Here's one place to start:  http://www.t-linespeakers.org/index.html

If you can't find what you're after, there are folks out there who can design for hire and you could DIY (or pay for local build).  Thankfully Martin King helped develop in the last few years a MathCad application for designing MLTL (and other designs) which really opened the door to MLTL (previously it was design by trial and error).

[JohnR]

Is there any reason why Subwoofers are not all designed to be be pushed hard into corners or hard up against walls (and I dont mean the boxes, I mean the drivers (and ports) are firing against the walls and almost touching them)?

Your neighbours probably won't like you very much could be one reason...

[oz_audio_todd]

Yeah John, the neighbours hate me enough when i dont let the puppies off their chains (but yeah get more complaints when i do!      ). (the puppies are my twin ported 12's     )

OK JLM, so you are talking about 'mass loaded transmission lines'? After ten mins of googling I gotta tell ya, I still dont know how they're more special than other TL's(?)
I do love the concept of transmission lines and I am sure there has to be a market for a good sized one that would happily do 15Hz all day, but as you said, doesnt seem to be case(?!). I know a few years back there were no programs to design them either, I would like to think that may have changed though(?)

So back to the original Q's, can anybody point me in the direction of any speakers that do use their woofers hard up against the walls for 1/4 or 1/8th sphere sort of loading?
Or is there any good reasons, that anybody can think of, why this wouldnt work really well?

Thanks again guys 

[JLM]

Mass loading of transmission lines is simply a means of increasing the effective density of air in the line thereby reducing the needed size of the cabinet.  Like other designs, stuffing helps reduce internal reflections.  It also allows for tweaking of the sonic characteristics of the cabinet based on where in the line and how much stuffing is used.

Facing into a wall would front load the driver.  Keep in mind that bass range sound waves are large relative to the dimensions you're thinking of.  (Length of wave = 330 meters/frequency, 15 Hz = 22 meters)  So any floor mounted sub that's half way close to a corner will be functioning in 1/8 sphere (1 Pi) space.

[oz_audio_todd]

OK, still dont fully understand, but dont have the means to design and test one anyway, so probably not important 
22 metres.. yeah, I guess that is a pretty good point in you average sized room.
Of course at 30Hz though, you only have to be 2.5 meters from a wall or ceiling to have the waves completely cancelled out!  (isnt your ceiling usually 2.4 or so?) (dam may be its better to have them away from the walls and have more frequencies destructively interfered??     ).
Dam, its all too hard!

[JLM]

30 Hz soundwaves (in air) are 330/30 = 11 meters long

[oz_audio_todd]

hahaha, OK fair enough, my bad, then you have to be 2.75m from the wall  (thats gonna make alllllll the difference!)

[JohnR]

Todd, what it basically comes down to is that you have to measure it.