4688 TCB Monster Subwoofer

[Zilch]

Hey, let's get some REAL volumn going here.

I gotta be careful not to trigger a seismic event in Kansas.

Actually, it came without drivers from subwoof. Wasn't cheap movin' that from NY to here.

BUT, I have a pair of E155-8's I'm gonna load in it today. BB6P says I'd get about 3 dB more SPL with 2242H's, and probably even lower distortion. No retuning necessary. I don't have a pair of those, tho....

The results will be reported here: http://earthquake.usgs.gov/

[JBLnsince1959]

I gotta be careful not to trigger a seismic event in Kansas.

Actually, it came without drivers from subwoof. Wasn't cheap movin' that from NY to here.

BUT, I have a pair of E155-8's I'm gonna load in it today. BB6P says I'd get about 3 dB more SPL with 2242H's, and probably even lower distortion. No retuning necessary. I don't have a pair of those, tho....

The results will be reported here: http://earthquake.usgs.gov/

Man, I've GOT to make a trip out to Ca. and see everyone...to many goodies out there

[Zilch]

a) View inside from one of the end chambers. Box is face down; end of duct in opposite chamber peeks in at the right. Gaskets in place, ready to load.

b) E155-8 Loaded.

c) View in through one of center chamber ports shows motors back-to-back. Only about 1" separates them. Might have to shim 2242H's to make 'em fit.

d) RTA measures actual performance. Mic at 1 M aimed midway between center chamber ports (where the action is). Mackie amp low pass at 125 Hz. Low end bars are 20, 22.5, 25, 28, 31.5, 35.5, and 40 Hz.

It plays better than JBL spec, basically. +/- 1.25 dB here from 28 to 100 Hz, down maybe 7.5 dB at 22.5 Hz.

As subwoof earlier observed, these are very efficient. Just a coupla watts rattles doors and windows throughout the house. That gets boring pretty quickly.

They have full bass tonality, i.e., no boominess. They don't do subsonic like paired B460's do tho. Could give 'em a little boost down there, probably, but only so long as I don't crank it....

[JBLnsince1959]

a)
They have full bass tonality, i.e., no boominess. They don't do subsonic like paired B460's do tho. Could give 'em a little boost down there, probably, but only so long as I don't crank it....

could try a pair of 2245's and a little eq. for more subsonic stuff if needed. the E-155's aren't subwoofs in the true sense.

[JBLnsince1959]

Maybe I've miss this ( sorry if I have), but what are these tuned to.

also, try running the software with some 2245's. Those were the big sub's JBL made. E-155's are more of a musical instrument speaker ( but then you know that)

[Zilch]

It's instructive, actually. While we don't think of E155 as a true subwoofer, and it certainly doesn't play like one in traditional alignments, the T/S parameters are very similar to 2240, the drivers that came standard in this box. Same with 2242H. What can be achieved with box design is quite amazing.

Also, we think of bandpass boxes as the boomy-sounding fabrications installed in pickup trucks. Having heard the surprising Control SB-5, I expected this TCB configuration to distinguish itself from those conceptions. It certainly does. Once again, the JBL specs on the design are reliable to the last decimal place.

The tuning is on the spec sheet. 24 Hz for the outer chambers, 68 Hz for the center one. Now that I know how good this is, I'll play a little with box designs for 2245. BUT, I'm most tempted to try the designs proposed by GordonW using 123A's or LE14's now that I know how they go together and operate. The one for LE14's is more appropriately scaled for HT and the drivers are plentiful. Check both out here:

http://audioheritage.org/vbulletin/s...ead.php?t=3922

[Zilch]

If we're not living on the edge... we're taking up too much room.

Floors are bouncin' here.

Zilch dubs the 4688 "impressive"....

[subwoof]

Nice to see someone was able to use this monster to it's intended duty.

Um..I know of 2 more of these still in the original factory boxes at a freinds garage.......his family has expanded which means the wife wants the garage back....:o)

anyone interested??? PM me

sub

[johnaec]

......his family has expanded which means the wife wants the garage back....

Use 'em for bedrooms for the kids.

John

[loach71]

Triple Chamber Bandpass sub uses dual 18" drivers in "Push-push" configuration. Motors in center chamber.

Drawing shows center (red) and outer (blue) chamber details separately. Bracing comprising center chamber "port tubes" only shown.

[Oodles more bracing therein. ]

Tech note here: http://audioheritage.org/vbulletin/s...ead.php?t=6289

JBL Lit here: http://www.jblpro.com/pub/obsolete/4688.pdf

This looks to be quite the subwoofer. Do you have any more dimensional information on the center chamber? I am interested in building four of these beasts -- I just acquired qty. 8 JBL 2245H drivers from a government auction. Do you think these drivers would work OK in this particular enclosure?

Thanks!

[Zilch]

Do you think these drivers would work OK in this particular enclosure?

My initial thought was "No way," but first looks in BB6P say 2245H will work fine.

Subwoof knows where there's a couple available for sale. Paying the freight and acquiring an original to build from would be my suggestion. That way, you can try it out first to be sure, too.

If you do that, prepare detailed construction drawings for the benefit of the forum.

I'm still looking for a 4685 and a 4682. Those smaller ones would also be fun to build. I have a preliminary design for 4685 in BB6P that I may build while the search continues....

[loach71]

My initial thought was "No way," but first looks in BB6P say 2245H will work fine.

Subwoof knows where there's a couple available for sale. Paying the freight and acquiring an original to build from would be my suggestion. That way, you can try it out first to be sure, too.

If you do that, prepare detailed construction drawings for the benefit of the forum.

I'm still looking for a 4685 and a 4682. Those smaller ones would also be fun to build. I have a preliminary design for 4685 in BB6P that I may build while the search continues....

I'm modeling this thing with BB6 Pro - but I only get gibberish on the center chamber and its vents. I've tuned the two outer chambers to 24 Hz ... and your 4" x 14" vent fits the model. I've tuned the center chamber to 68 Hz -- but BB6 Pro says NO WAY for the 4" x 14" vent. I must be doing something wrong..


The 4688s for sale on E-Pay are in upstate N.Y. and the seller wants $400 each for the cabs with no drivers. Shipped to rural Montana, the costs would be huge. So that is why I am doing the math... Sweat and sawdust equity for the impecunious..

Here are my initial results: (don't laugh too much!)

Internal dimensions quoted.

Outside chambers - 25.5" x 25.5" x 19.5" - single vent 5.991" I.D. x 14" long

Inside chamber - 25.5" x 25.5" x 22.6" - vent data comes out totally silly!

After I get this worked out I'll publish the complete data set and cut sheet info.

Any insights would be welcome.... thanks in advance for your kind help offered to this n00b...

[4313B]

I just acquired qty. 8 JBL 2245H drivers from a government auction.

Nice! That's four pairs of 4345's.

8.0 surround sound (won't need subs)

[loach71]

Nice! That's four pairs of 4345's.

8.0 surround sound (won't need subs)

With the right enclosure and all my old BGW 750s I might be able to generate the "brown note" <YIKES>

[Guido]

I felt (heard?) those beasts once in a club. Believe it or not 4 each stacked per side.
It was definitely an "adventure".

YEAH! Those where the times!