Dig Down Deep... Devilishly Deep... Behold Other Subterranean Subwoofers Out There...

[JonFo]

Er... isn't it 2.54 cm in an inch? That would be

2.54x10 = 25.4 mm x 1.75" = 44.45 mm. If that's peak to peak, that's 22.2mm Xmax one way, which is not likely to all be linear (generally, depending on motor structure, your xmax is pretty far outside your linear excursion range)

The big question is here...is it peak to peak?

http://tcsounds.com/lms5400.htm

This is a monster driver. Weighs 75lbs, Costs $1000+, has 38mm linear Xmax (one-way) and has 2500 watts RMS power handling. The magnet alone is 516 oz (32+ lbs)

The DD-18 is a very nice sub, and has servo control, which is quite nice. Expensive though! And BIG!

Ok, the newer velo's do have significantly more displacement. And no question two DD-18's will pretty much handle most rooms.

An IB of 4 15's is about one eighth the price though ;-)

Iwalker, most vendors xmax rating is linear, one-way. So supposedly one can count on the volumetric displacement of that xmax with reasonably low distortion. But some will quote max physical p-p displacement just to impress in the marketing literature, so It’s important to read the true T/S specs on the driver.

That TC LMS 5400 with 38mm of Xmax is awesome!

Now, an IB made up of two LMS 5400’s would be pretty killer. A quad 5400 setup would be able to destroy most homes

 

[JonFo]

After exploring JohnFo's IB and others, I've been thinking
about building one myself. Perfect attic for it. Thing is,
I never could find a driver that would concentrate on the
reeeeeal low-end; say 5 Hz to no more than 35 Hz. I think
that range would complete the Summit's 25Hz bottom nicely.

TC Sounds LMS-5400
Cost: $1,200
Cone: Titanium !!!
Size: 18-inch
Stroke: 3-inch peak to peak!!!
Fs: 14.5 Hz !!!
Qts: 0.26

You can't hear, but just reading the specs causes me to
literally do that evil "mwuah ahh ahhhh" laugh. I didn't
think people really did that, but I guess we do.

JohnFo, if these are not the specs of an ideal IB driver,
please tell me what I should look for. Two of these 18-inch
drivers facing each other are equivalent to a single 26-inch
driver with a 6-inch peak to peak stroke. That's a HUGE amount
of air movement. I bet you could get 5 Hz with that setup.
...

Yep, that’s an ideal IB driver. It's being discussed over on the Cult of the Infinetly baffled. Some crazy person is talking about 15 of them

As you note, two balanced units in an attic manifold would give you all the bass you’d ever want. And yes, 5hz notes (use the TRW test disc) would be felt, as well as seen, as probably stuff will start walking around on it’s own from all the vibrations

I’d still cross over to the Summit at 40hz or even 60hz. You’d be surprised what that might do for upper bass clarity from the Summits.

 

[Joey_V]

I will get those Gothams in a few years... mark my words!!!

Argg!!!

 

[HsvToolFool]

I’d still cross over to the Summit at 40hz or even 60hz. You’d be surprised what that might do for upper bass clarity from the Summits.

I'm one of those who'd rather have too little bass than
risk mucking up the mid-bass. The Summit's -3db point
is 25 Hz, which is darn impressive for the speaker size.
Martin Logan gets it near perfect then a hack like me
comes behind them with a DIY project and mucks up
everything. Bleah.

But then again, you never know until you hook it up and
listen. I may get the Summit in here and decide I don't
need a sub. I suspect that will be the case, but I do like
the idea of adding that last 20 Hz of rumble.

The enclosure for an IB using the LMS-5400 had better be
welded from 1/4-inch steel plate. I suspect those woofers
will shake glued-and-screwed wood enclosures to pieces
after exposure to Summers with 70% humidity at 110 F.

Another consideration is the grill. Cloth or painted wire
mesh ain't gonna cut it when you're push-pulling gallons
of air per stroke. Don't want no flapping/bulging/pulsing/
buzzing rectangles hanging from my ceiling drawing
attention to themselves. No how. Nuh uh.

I bet some 1/2-inch thick aluminum honeycomb core
(used for composite panels) could be epoxied to an
aluminum grill. That would allow tons of air to pass freely
yet be rigid enough to withstand huge pressure change.

 

[Tj Bassi]

Does anyone have a recommendation for a good book or website that discusses subwoofer theory/design? I've always wanted to dig in and build one but never did. Maybe its time. I have this vision of a sub tower, almost similiar to the Statement E2 sub-bass array, standing next to my ReQuests. Unless, of course, someone has a spare pair of E2 bass arrays for grabs
Tj

 

[JohnA]

...
Here's a link to a supplier in the UK:
http://www.mcaudio.co.uk/audio-bass.htm...

Nice link.
I'll investigate if I decide to upgrade my current twin 12" sub drivers:cheers:

 

[Tj Bassi]

Jonathan stated :

" In my book, no box sub, and none of the ones listed so far can compete with a well designed Infinite Baffle sub. Yes, not everyone can host one, but if you can, do not waste your money on commercial subs. "

I've been doing some reading on IB subs, but have found several sources that describe a sealed-enclosure as being 'an infinite baffle', as such that the waves from the front of the driver cannot reach the rear waves because the baffle fully covers the rear radiating surface. In your comment you draw a direct distinction between 'box' subs and what is described as an 'infinite baffle'. Indeed, all of the subs on the I.B. Cult website use a seperate room at the box itself. Are these a variation of the infinite baffle or am I incorrect in my understanding of a sealed enclusure vs the latter?
Your project has me intrigued. I am (was) on the threshold of purchasing another Descent sub but since we have a dedicated room planned, an IB setup is a possibility.

T-

 

[risabet]

This is actually the original IB design. In this design the rear enclosure/room adds very little springiness to the driver and that allows for the bass cutoff freq to be lower with the standard IB rolloff of 12dB/octave. Result? Deeper bass with better transient response than in a smaller box.

The ultimate design IMO would be a transmission line built into a room. You could then get the benefits of an IB design with the benefits of a vented enclosure and few of the shortcomings of either.

 

[kwr]

I'm only posting this because of the name. I have never heard any of this company's products or have heard any credible opinions.

http://www.worldsbestspeakers.com/b_buster.htm

Kevin

 

[Tj Bassi]

In researching I havent come across any examples of a 'transmission line' sub, at least not so far, unless they are a variant of some of the IB projects posted elsewheres. In fact, I had not heard of an infinite baffle sub until reading Jon's posts in this thread, but there are plenty of pages on them if you do some looking.
Not all of the IB sub installations are pretty (not everyone is a wood craftsman, I guess), but almost everyone who has built one and written a page on it has proclaimed 'it far exceeded expectations'. Makes me think I might be missing out on something if I dont give the project some consideration.

T-

 

[risabet]

In researching I haven't come across any examples of a 'transmission line' sub, at least not so far, unless they are a variant of some of the IB projects posted elsewhere. T-

The TL is a variant of the standard vented design, in which in place of a vent a folded labyrinth is built in the cabinet/room that is equal to the length of the lowest note to be reproduced, ~50 feet for a 20Hz note. The labyrinth is then stuffed with some type of batting to, in theory, totally attenuate the backwave w/o adding any springiness to the driver. You can see why you can't find any due to the large size of TL enclosures.

 

[Tj Bassi]

After reading a few IB construction articles, I have the impression that the builders werent too concerned with the volume of the room behind the driver. Your HT or audio room might be a certain size, but the attic or basement the driver is mounted in could be 4~5 times in volume (just a guess). I'm also trying to figure out how these fellows chose the proper driver...a process that seems to be more lax than if you were building a small sealed unit.

It would be great if I could find someone locally that actually built one...

T-

 

[JohnA]

Another idea

Suppose that you have a fireplace in the room, which you are not using for lighting fires

That is an exit to the infinite outside world via a chimney. Wouldn't that be a good basis for an IB design? What if the sub fits in the fireplace and it has a 'chimney' that vents into the real chimney? Would it have to seal? There wouldn't be much of the backwave coming back, would there?

 

[Peter Hogan]

Suppose that you have a fireplace in the room, which you are not using for lighting fires

That is an exit to the infinite outside world via a chimney. Wouldn't that be a good basis for an IB design? What if the sub fits in the fireplace and it has a 'chimney' that vents into the real chimney? Would it have to seal? There wouldn't be much of the backwave coming back, would there?

I suspect that the flue in the chimney would act as a large 'tuned port', and based on its size and length, it would add a major resonance peak to the frequency response (much like one of the large pipes of a pipe organ)...quite different from using a large open space behind the speaker as most IB's do.

My .02,
Peter

 

[karma]

HI All,
I'm ambivalent concerning infinate baffle designs. One of the reasons for my indifference is the inability to control the low frequency resonance of a large driver. The baffle/enclosure offers no help as far as I know. I think that is a major drawback. It is definitely audible.

Is there an answer to this?

Sparky

 

[Tj Bassi]

There must be something to it, or all of these HT enthusiasts wouldnt be doing it. Note that I said "HT", for if you read enough of the IB construction articles, many of the users comment on it not working well for music-only. Take that for what its worth; I havent had anyone clarify that statement yet.

T-

 

[Robin]

Quad L-ite Subwoofer...

The Interesting Quad L-ite Subwoofer... :cheers:

 

[Robin]

Def Tech ~ Trinity Sub...

A relitively interesting Def Tech ~ Trinity Subwoofer design...

 

[Robin]

Dantey - DTS-20 Subwoofer...

This unusual subwoofer design deserves a look or two more... It's a long and low subwoofer speaker cabinet. :cheers:

 

[Robin]

The Biggest Subwoofer Speaker Ever...

:wow:This has got to be the biggest subwoofer cone speaker around...

http://images.google.com/imgres?img...prev=/images?q=Huge+Subwoofer&hl=en&sa=N&um=1