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View Full Version : Down firing vs. forward firing subwoofers



jim henderson
07-24-2003, 05:35 PM
My current subwoofer is a forward firing 2235H in an unfinished 5 cf baltic birch plywood cabinet placed in the rear corner of our family room. Unfortunately, my wife has made it clear that this is unacceptable, so Im considering making a coffee table/subwoofer cabinet with a down firing 2235.

What are the acoustic pros and cons of down firing versus forward firing subwoofers?

Mr. Widget
07-24-2003, 06:13 PM
Replace the wife. It is the simpler solution.

Well if that is deemed unacceptable I suppose a downward firing sub is not the end of the world. As long as it truly is a sub, i.e.. no output above 75-80 Hz the acoustic change will be very slight. Make sure that the air passage between the floor and cone/baffle is not restrictive. I would want the area of the slot all the way around to be 1.5 to 2 times the area of the cone as a minimum.

John
07-24-2003, 06:56 PM
I have to agree with Giskard a guy has 3 Billion choices!!!: :smsex: :hmm:

mikebake
07-24-2003, 08:28 PM
Back to reality, guys. 3 billion women; now subtract those two young and two old; down to 1 billion. Eliminate the unaccepatables; too bitchy, too ugly, too whatever...............now we are down to just several hundred million women we could live and mate with happily. Not a huge number, okay??!!

Alex Lancaster
07-24-2003, 08:43 PM
The ideal is a live-in-maid and and a day wife; If You insist on marriage, pick a wealthy one, they all scream at You anyway, and Youll be able to spend more on JBL products. (I am not in any way connected with JBL)

boputnam
07-24-2003, 08:52 PM
I can barely type from the hilarity of those prior posts... Ha! :rotfl:

"unfinished 5 cf baltic birch plywood cabinet

It ain't the size, it's the finish!

So, assuming the wifey is still in the mix, maybe you should barter for finishing the cabinet and sorting out some acoustically transparent grill cloth, parking a not-too-leafy fern at the baffle, and draping her (uh, the wifey...) in cubic Zirconia (ZrO2) before agreeing to the floor-directed decision. Anyway, a proper floor-directed sub will likely walk-off anything artistically parked on it's top, anyway. :D

My admittedly otherwise prejudicial wifey has grown quite fond of the 4345's - but there is a definite correlation with their fine cabinetry and clean grill cloths. Just a thought...

boputnam
07-24-2003, 09:51 PM
"...and draping her in cubic Zirconia..."

Just to be clear - I have nothing against your wife, nor her desire for a family room ever-ready for that possible impromtu photo opp by Sunset Magazine ;).

IMHO, diamonds have low real intrinsic value. Diamonds, an otherwise very useful industrial stone, have lofty valuations which are fabricated by cartel restriction over supply. :eek:

If it's worth supporting the cartel to get you a "proper" sub-woofer, by all means get it done! :D

jim henderson
07-24-2003, 10:16 PM
Did you guys all have wine with dinner? ;) Actually, the wife is a keeper :) Is a downward firing configuration acoustically inferior to forward firing?

Mr. Widget
07-24-2003, 10:41 PM
Originally posted by jim henderson
Did you guys all have wine with dinner? ;) Actually, the wife is a keeper :) Is a downward firing configuration acoustically inferior to forward firing?

Well my wife told me that if you guys are half as nerdy as I am you better rethink the millions or billions of options.

The truth be told I am very fortunate to have a wife that will tolerate five small speakers in the living room and share her photo studio downstairs with my home theater and monster stereo set up.

Ok, she just got off my chest and put the knife back in the drawer...

I have built very successful downward firing subs. In one situation I designed a sideboard type of thing with thin vertical slots configured into the design to hide the fact that there was a woofer in the cabinet. They simply looked like decorative elements in the design of the cabinet. Bo is right about the potential of vibration. It must be built like a brick...

Also if you are firing onto a carpeted floor great, if it is a hardwood floor have it fire into a piece of Sonex foam.

Tom Loizeaux
07-25-2003, 07:28 AM
I've wondered about down-firing speakers. Since gravity pulls on the cone, over time, will the voice coil become decentered? I assume that drivers designed for this position are designed to counteract this pull but the 2235 is designed for horizontal motion and may not fair well in the vertical mode. (?) Just my concerns.
I asked JBL Consumer about this before I bought my PB12 subwoofer and they basically said "What?".

Tom

mikebake
07-25-2003, 08:28 AM
Originally posted by Giskard
Hi Tom,

Yes, after a period of time the 2235/2245 suspension would sag.

I similar problem can be observed in some of the 3 billion women........

Charley Rummel
07-26-2003, 11:06 AM
And then there's the issue of weather larger cones start to sag sooner and farther than smaller cones. There's nothing like nice big cones in a new, well designed enclosure, but after a while, Ol' Father Time and gravity will have their effects...
:bouncy::bouncy:

ANYWAY....

As many of you may know, I was never a big proponent of the subwoofer concept, but in my opinion I think forward loading would be a better solution than downward loading (or firing, if you prefer). With downward loading, I've wondered about the effects of energy dissipation into the floor, regardless of enclosure design, flooring characteristics, etc., and the effects of phase shift and room characteristics on the wave propagation as well. I know these issues also impact forward loading, but I feel forward loading is the lesser of two evils. The argument has been that in the first couple of octaves the wave propagation has no directional charactoristics, so loading direction is irrelevant, but I respectfully submit I've always regarded this as a sales-pitch.

...With forward loading, and with good suspension and maintenance, the larger cones will resist gravity and last much longer without sagging setting in. We will be able to appreciate their good performance for many years to come:D .

Regards,
Charley

boputnam
07-26-2003, 11:20 AM
Hey, Charley...

"With downward loading, I've wondered about the effects of energy dissipation into the floor, regardless of enclosure design, flooring characteristics, etc., and the effects of phase shift and room characteristics on the wave propagation as well."

This won't be technically supported opinion, but merely obesrvation - last night, my neighbor, with simply the best 5.1 system for many blocks around, came over for my continuing "meet the cabinets" party. He brought a basket of CD's, and some DVD's. He was convinced his 5.1 and subs were tops, and that my retro 1980's 4345 stuff was nutty.

Well, he "get's it" now. Besides all the other accolades (most common: "this is like discovering stereo for the first time..."), after the first scene in "The Matrix", I had to get a 'nother neighbor to help pull him from out of the sofa. The 4345's simply pounded him into there. He was ga-ga. And that's his favorite DVD - he knows it by heart. He just never heard it before... ;)

There seems to be something "more" in front-facing VLF's, than I have heard floor-firing subs be able to approximate. Just MHO. It just seems that floor-facing subs are doing their best to lift their cabinet off the floor, whereas front-facing VLF's are coming right at you. :eek:

mikebake
07-26-2003, 01:11 PM
"The argument has been that in the first couple of octaves the wave propagation has no directional charactoristics, so loading direction is irrelevant, but I respectfully submit I've always regarded this as a sales-pitch."
For what?
I would think we are talking about physics, not sales pitches. There would be some minor differences perhaps between otherwise identical front and down firing systems, but most of the room effects for bass would seem to be there in either case. I suppose you might be right, though, that with front firing you MAY be at least avoiding the potential for greater problems.

Robh3606
07-26-2003, 07:24 PM
Hey Bo


"There seems to be something "more" in front-facing VLF's, than I have heard floor-firing subs be able to approximate. Just MHO."

It's funny how some are set-up. I have 12" slot loaded for LFE. The driver and the port face the floor and drive a slot 1 1/2 inches high at the base of the cabinet. I have never really understod slot loading. With a horn the diaphram drives the air in the horn so the area increases as the wave goes down the horn. With a slot it seems to be the opposite. You would think the cone would get more bite as the slot is much smaller than the cone diameter. I also think larger diaphrams with shorter throw sound better than the smaller long throws. They just seem cleaner and have better definition. Just sound more natural to me.

Rob:)

boputnam
07-26-2003, 07:57 PM
Hey, Mikebake..

Where the hell IS that place?? Whoa... So, there is NO WAY you can post a photo like that and not 'splain it! :no:

Tell us!


And, hey, Rob...

"[/i]I also think larger diaphrams with shorter throw sound better than the smaller long throws. They just seem cleaner and have better definition.[/i]" Me, too.

But, what of identical transducers used in the two different configurations (down, vs in-your-face) - do you think we could tell a difference? Physics tells me "acoustically" likely not, but I worry about all that energy forced into the floor, and how it muddies things. No? :confused:

Robh3606
07-26-2003, 08:15 PM
"But, what of identical transducers used in the two different configurations (down, vs in-your-face) - do you think we could tell a difference?


That is a very good question! I know diddly about slot loading but if you take a driver that can be used in a reflex box or a horn I would take the horn. Even though it is the same driver if its a good horn I would think under almost all circumstances you would have lower distortion and better loading from the horn. I guess the box would be more graceful at the extremes and the horn could limit the exremes on the frequency range but that's just part of the trade offs. Now could you/I hear the difference at a reasonable equivalent SPL??? That I just don't know. Never tried it.

Physics tells me "acoustically" likely not, but I worry about all that energy forced into the floor, and how it muddies things. No?

I wonder about that too. I think the extreme vent velocities that you see in those loading schemes are the reason for the loss of detail. You have a lot of friction in that vent I would think suptle preasure variations would just get lost in the air rush.

Rob:)

Robh3606
07-26-2003, 09:00 PM
Hello Rob

Good point! Damn near ruined a pair of 123A's I had in storage. Forgot to flip them so the sagged. Luckilly they went back after an extended flip in the opposite direction. Want to build a rack to store my spairs on edge.

Rob:) :)

mikebake
07-26-2003, 10:37 PM
That place is at my hairdressers.....okay, actually, it's a system in France, many drivers of which are JBL. Many of you probably have seen the photos. I'm at home now, and the photos are on my computer at work. He has since gone through 2 or 3 different systems; I'll post a few Monday-ish. Neat looking stuff. It's just fun to add a few un-related photos of interest..........
MBB

Royd
07-27-2003, 03:40 PM
I have a a dozen pairs of JBL 12" woofers in storage.
Some are stored facing downward, and some upward.
They are models 123a-1, 123a-3, 128H, and 128H-1.
They've been in storage about 2-3 years now in a room
without any insulation or temperature control. Storing
them vertically, would require my building some form
of structure to hold them in that position. Also,
doesn't vertical storage also have it's problems?

GordonW
07-27-2003, 09:45 PM
Royd, as somebody said somewhere before, just go in there every couple of months or so, and flip 'em all over. As long as you keep them rotating like that, I can't really see any serious problems coming about...

Regards,
Gordon.

Tom Loizeaux
07-27-2003, 10:14 PM
Royd,
As discussed in this Forum some time ago, the spiders and surrounds were designed to resist laterial movement, but allow front and back movement. Storing speakers "on edge", or with the cones vertical, is far better then storing them laying face up or face down!

Tom

Alex Lancaster
07-27-2003, 10:35 PM
I would think that storing them horizontally and flipping them around, lets say 3 times a Year, would be less detrimental than vertically, if just for simmetry.