LE14A quandary

[Donald]

Just got a pair of LE14A. Still have intact, original surrounds but they have seen better days. Will have to get new surrounds. The serial numbers are 2858 and 2859. Very low numbers, no? The strange part is they are 16 ohms.

Which means I can't use it in my L222 or Dorian S12. Time to build somthing, I think.

Hmm, to build a cab all I need is a table saw, router, sander, clamps, etc, etc.
Couple of grand for a box. :-)

[Zilch]

Well, I have the other two 16-Ohm LE14's you're gonna need, S/N 5429 and 5430. I already have another 4 8-Ohm ones set aside for this project. We're gonna build triple-chamber bandpass subwoofers based upon the Control SB-5 model, scaled up for LE14's.

The drivers will mount in face to face isobaric pairs, wired inverse parallel, on the two interior panels dividing the box into three chambers. All we need is for the box-modeling gurus here to tell us the box dimensions and the sizes for the 3 ports. We're gonna build outta 1-1/8" Sturdifloor. :)

Check it out HERE (http://www.jblpro.com/pub/obsolete/Control_sb-5.pdf)!

[Alex Lancaster]

:) Hi: What is Sturdifloor?

[Zilch]

What is Sturdifloor?Structurally rated subfloor plywood or oriented strand board. Whichever the lumber yard has in that thickness, OSB preferred, probably.

The thickest and strongest stuff we can buy without payin' a huge premium....

[Oldmics]

Gentlemen,Gentlemen

Why fool around with measley little 14 inchers when the big guns were already done by the pros.

Follow this link and then when you are on that page-check out the 4688-4

http://www.google.com/custom?q=4688-4&sa=Google+Search&cof=LW%3A100%3BL%3Ahttp%3A%2F%2Fwww.jblpro.com%2Fj bl-pro-logo.gif%3BLH%3A100%3BAH%3Acenter%3BGL%3A0%3BS%3Ah ttp%3A%2F%2Fwww.jblpro.com%3BAWFID%3A6d393ea1cf387 9dc%3B&domains=www.jblpro.com%3Bwww.jblproservice.com&sitesearch=www.jblpro.com


Oldmics

[boputnam]

The strange part is they are 16 ohms. Which means I can't use it in my L222 or Dorian S12. :confused: Why not? Have you measured them, or is that what is labelled? Giskard has posted numerous times on this "labelled impedence" issue, and IMO, it may not preclude your planned project. Although, I too am intrigued with the replies you've gotten... :p

[Zilch]

Oldmics: 30 X 30 X 60 and 250 Lbs.? Naw, we're gonna build something PRACTICAL here. Those are just one channel. :p

Do we have any details on 4685 and 4688? They CLAIM to be pushpull, and even TCB (?), but only use two drivers.

Last made 1982, no exploded view Tech sheets. :mad:

SB-5 is two-channel acoustically summed in the center chamber using four pushpull drivers.

We can use up the surplus of LE14's floating around out there. :D

[Donald]

Bo,

I don't have a project. Although what is being talked about here is interesting.

Anyone here have thoughts about using 123As in this setup?

I have the speakers. I have sound deadening fiberglass. I can assemble circuits. No reason a xover can't be wired point to point. All I need is a box and a xover diagram. :-) And I just might have a cabinet builder that I could enlist. I guess I need dimensions.

What I want to know is cone motion. Do all 4 move left and right in unison? Or do the left face to face pair mome left and the right pair mobe right?

[Zilch]

Each face-to-face pair comprises a channel, left or right.

The two speakers in each pair are wired in parallel, but one the reverse of the other, so that they move in unison, one pushing, one pulling, toward and away from the center chamber.

The two pairs operate in phase, both "facing" the center chamber. Thus, given the same signal, the left pair moves left while the right pair moves right, and vice-versa, when the signal polarity reverses.

It's quite amazing. You have the lid off with all the speakers exposed, playing. Sounds wimpy and terrible. Drop the lid on, and it's, "OMG, where is that BASS coming from?"

WinISD has a bandpass mode, but I can't get it to produce reasonable numbers. It also warns that getting it tuned right is an art. We need the box-modeling gurus here to get us started with this, please....

123A's should work. Extended bass woofs are probably better, but what the Hell, give it a try. 4688 used 2240H's down to 23 Hz (-10 dB) while 4685 and 4682 (specs unknown) used 2225H's and 2206H's, respectively.

Control SB-5 uses a pair of CSB-5003 5-1/2" drivers on each side. They've got rubber surrounds, if I recall, but don't hold me to it until I open 'em up and look again.

They're wired inverse-series, but that doubles the impedance, thought it's not reflected in the data sheet:

http://www.jblproservice.com/pdf/Control%20Series/Control%20SB-5.pdf

I guess they're "nominal 4-Ohms" when 8-Ohm satellites are connected. Whatever. I'm wiring inverse parallel with 8-Ohm drivers to get an actual 4 Ohms each side.

Note shorter, larger diameter port in the center chamber....

[Donald]

>>Extended bass woofs are probably better
So 4 SUB1500 would be better? :-)

I assume no internal xover would be needed if the amp feeding the box was being fed the low output from an electronic xover?

[Zilch]

I assume no internal xover would be needed if the amp feeding the box was being fed the low output from an electronic xover?I assume the same. We don't want anything but wire in the path, and we're not doing "satellites" here.

Maybe Niklas will build with Sub1500's. :D

[GordonW]

WinISD has a bandpass mode, but I can't get it to produce reasonable numbers. It also warns that getting it tuned right is an art. We need the box-modeling gurus here to get us started here, please....



You rang? :D :D :D

Did the box model, not in WinISD, but in BassBox. The 123A will work, but NOT easily in the type of bandpass JBL used in the described above (triple-chamber). The problem, is the ports in the two outside chambers... it works much better, with a high-Q woofer such as a 123A, with the outside chambers SEALED and the center chamber VENTED.

I've included a line diagram of a proposed box, for 4- 123As in the push-pull isobaric configuration. Total box volume, is about 17 cubic feet. In the drawings, the measurements under the dividers are from the OUTSIDE of the end of the box, to the CENTERS of the dividers (ie, 3/8" into a 3/4" thick piece of wood). Also, the vent dimensions (and it needed them to be this big!) are 16.5" tall (full internal height of the box), 4" wide (internal dimension of the vent), and 26" long from the outside of the box to the very inside end of the vent. That's a 66 square inch vent!

According to my calculations, this box should be able to exceed THX spec by about 5 dB- something like 110 dB max output- with a bandwidth of 25 to 70 Hz, f3 on both ends. That's with only a 200 watt amp running the WHOLE thing!

BTW- the 123As should be wired in series-parallel... gets you back to about a 6 ohm load...

[Zilch]

Woo-HOO, Gordon! That looks like one Helluva nice project. 123A's are plentiful, for sure.

How about for LE14A's? Can you run them for us too, please? That's what I'm geared up to build here.

Have you ever opened up a 4682, 4685, or 4688 to see how they are designed? They're called "Triple-Chamber Bandpass," as well, but with just two drivers.

Looks like, wired inverse parallel, with the two sides kept separate, a 100W/channel amp could drive the box you designed here nicely, too, then. We tend to think of subs being driven with summed mono. This configuration lends itself to being driven stereo; summing occurs acoustically in the center chamber....

[MJC]

All the 16 ohm LE14A I've seen are coax units, I have one in a L55. Are the pair you have coax, or just a single driver?

[johnaec]

All the 16 ohm LE14A I've seen are coax units, I have one in a L55. Are the pair you have coax, or just a single driver?Isn't the LE14C the coax version?

John

[MJC]

Isn't the LE14C the coax version?

John
Ya, that's correct, I hadn't finished drinking my morning coffee when I wrote that reply.:banghead:

[Zilch]

4 ea. "8-Ohm" = 5.8, 5.8, 5.9, 6.1

2 ea. "16-Ohm" = 5.8, 6.2

The 16-Ohm units are the oldest ones; original Lansaloy surrounds, so not recones.

Looks like the early numbers game is all.

Still, I'd probably want to use 4 "16-Ohm" together, not mix them.





Notes:
A) Measured at the solder terminals behind the push terminals, which are oxidized and unreliable for DCR measurements.

B) Gotta be quiet. Microphone effect is apparent. DCR is measured with low current. How low, I dunno. Itza Fluke 77 multimeter.

[4313B]

4 ea. "8-Ohm" = 5.8, 5.8, 5.9, 6.1

2 ea. "16-Ohm" = 5.8, 6.2

The 16-Ohm units are the oldest ones; original Lansaloy surrounds, so not recones.

Looks like the early numbers game is all.Yep, we've hashed over this before but you've brought data to the hash. :p
Data is our friend.
Thanks! :)

[Zilch]

Having played just about every subwoof game ever conceived, do you have any insight as to the design layout of 4682, 4685, and 4688? Or specs on the first two? They claim to be "Push-pull" Triple-Chamber Bandpass with two drivers. I also see reference to an "upper chamber" in the literature. I'm guessin' the triple ports are the center chamber "output." Also, can you tell us what happened to these products? It's been 20+ years since JBL made them, apparently.

I've seen a design similar to what Gordon proposes here in a recent JBL subwoof product, no? At least from the exterior: no drivers visible, just a continuous wide slit in the center of the front? I'm thinking Gordon's design would make a good subwoof base under a widescreen home theater....

While I'm rambling here, readers might be interested in seeing a new Vertec sub I came across in nosing around for info. Looks outstanding in a "relatively" small B380+ size box:

http://www.jblpro.com/vertec1/new_vertec/vt4881.html

See also:

http://www.jblpro.com/vertec1/new_vertec/vt4882.html

[Heh, heh.]

Looks like them specs are with EQ, but similarly were B380/460....

[Donald]

So, really 16 or mislabeled 8?

[Earl K]

Obviously, JBL used to use 2 different labelling methods to arrive at their "conclusion" for stating a nominal impedance. This impedance territory/story has been extensively covered in this or past forums . An impedance "curve" is just that, it's a curve, pick any point on it and one will get a differing conclusion about the working ( AC ) impedance .

- Suffice it to say; people who want to "build something" according to "information" as superficial as what the foilcal label says - shouldn't use JBL in their projects.
- Learning how to measure AC impedance is also useful for the project-minded.

regards ,. Earl K

[GordonW]

Woo-HOO, Gordon! That looks like one Helluva nice project. 123A's are plentiful, for sure.

How about for LE14A's? Can you run them for us too, please? That's what I'm geared up to build here.

Have you ever opened up a 4682, 4685, or 4688 to see how they are designed? They're called "Triple-Chamber Bandpass," as well, but with just two drivers.


Your wish is my command... :D

Box for LE14s. HOWEVER- note that this one is NOT isobaric/clamshell... it IS push-pull, but with EACH driver mounted FLAT on a baffle... so that ALL 4 drivers are directly accessing both chambers of their box.

Note that this box IS a triple-ported bandpass (vents in ALL THREE chambers). The LE14, being lower Q than the 123A, lends itself quite well to this alignment.

In this, due to clearances, I'd get driver access through panels into the OUTSIDE chambers of the box, NOT the center chamber... the two "front" drivers (near the vent) CANNOT go in through the center chamber- they'll hit the vent, going in, and the magnet will not clear. With all the air pressure THIS monster is going to generate, you want that center chamber to be built like a Brinks truck... so making access through the OUTSIDE chambers is MUCH better anyway.

Box dimensions are: 56" wide, 36" deep and 20" high. This assumes 3/4" thick material (MDF or high-layer-count plywood). The internal chambers are 19" wide internal for the two outside chambers, and 15" wide for the center chamber. The vents are: 6.75" wide (inside width), full height of the box (18.5") and 18" deep for the center chamber vent, and 1" wide, full height of the box (18.5") and 18" deep for each of the two end chamber vents. Putting the vents near the outside wall, like shown, can reduce the parts count, by letting the outside walls act as one "side" of the vent...

This box will give a bandwidth of about 24 Hz to 89 Hz (f3 points), with a calculated max output of between 112 and 117 dB throughout that range. It'll take 400 watts total power (100 watts per driver) to do it, but it WILL be probably 4 db louder than the 123A box, or so...

Regards,
Gordon.

[Earl K]

Very Nice Work! Gordon :yes:

:cheers: <. Earl K

PS ; Next Magic Trick

Can You - turn a le15b/2216 into a usable le15a ( maybe Fs of 27hz ) ?

[GordonW]

Box for TWO Le14As. Basically, the above quad box, cut in half. But, with a little "gimmickry" to make the vent work right...

The problem was, to get enough area for the center vent with the reduced box volume/depth, it was necessary to "bend" the port... to make it turn a couple corners. This is done by using the back wall and a couple of "internal director" plates to extend the vent length.

The center vent width is 4"; the "auxilliary extensions" on the center vent should be 2" wide. The center vent plates should end 2" from the back wall. This can be done, if a vent plate 18.5" high and 14.5" deep, from 3/4" thick wood, is used for the center plates, mounted to the BACK of the front wall of the box (where a 4x18.5" rectangular hole is cut in the front of the box to open the vent to the outside, mating to the plates). Then, space the "side auxilliary vent plates" 2" away from the outside of the center plates. The auxilliary vent plates should be 18.5" tall x 8.25" deep, mounted to the back wall of the box.

The outer vents are only 3/8" wide... the internal plate is mounted 3/8" from the outside wall. The overall outer chamber vent lengths should be 14.5"; this can be accomplished by mounting 18.5" tall x 13.75" deep plates to the back of the front wall, and cutting a 3/8" wide slot into the front of the box to open the vent to the outside.

Again, this box assumes 3/4" thick wood everywhere. The woofers should again be accessed through the OUTER chambers... with this complex center chamber, it should be PERMANENTLY SEALED, to avoid leaks...

BTW: In case you want to play around with the center vent, the overall vent should be 18.5" tall, 4" wide and 26.25" long. When you add the 15.25" center, 2.75" across the back, and 8.25" back towards the front, you get 26"...

[Zilch]

I can hear them table saws buzzin' aready! :yes:

What's the predicted performance of the dual LE14A box?

Seems clamshelled LE14's would yield a smaller box than the quad push-pull you propose as well, since the Vas of the compound pair is half that of the individual drivers, no? Can't configure an alignment for that, as originally proposed? I mean, that's the big plus of isobaric, I assume.

[It's clear this is beyond my expertise here.] :rolleyes:



Suffice it to say; people who want to "build something" according to "information" as superficial as what the foilcal label says - shouldn't use JBL in their projects.Now, Earl, no need to be HARSH with us hackers here. We'll GET it, eventually. Them 16-Ohm LE14's aren't rare, they're CHEAP, 'cause nobody want's 'em. Nobody but US now, heh, heh.... :p

[Earl K]

- Sorry if I sounded "Harsh" ( I intended something else ) :coolness:

- anyhow,, its' you "Hackers" who were able to get Gordon to cough-up some neat designs ( for free ! ) . :thmbsup:

( & yeh - so much for cheap and cheerful "16 ohm" le14s flooding the market )

:cheers: <> Earl K

[10 Watt Street]

Here is an interesting 18" isobaric sub, uses four 18"s per cabinet:

http://cls.audiogon.com/cgi-bin/cls.pl?homesubw&1108139256

[Zilch]

Cool. Those 18's appear to be in "back to back" isobaric configuration. I think "face to face" couples them more closely, since the intervening air column "spring" between them is minimized.. Those are not bandpass boxes, of course.

While these below are not isobaric OR bandpass, JBL Precision Directivity products provide a suggestion as to how isobaric might be easily accomplished in conventional alignments:

http://www.jblpro.com/pages/pd_series/pd162.html

http://www.jblpro.com/pages/pd_series/pd125.html

I guess it IS some kinda bandpass box when you array 8 of them together as shown in the .pdf there. Heh.

[Don McRitchie]

While I'm rambling here, readers might be interested in seeing a new Vertec sub I came across in nosing around for info. Looks outstanding in a "relatively" small B380+ size box:

http://www.jblpro.com/vertec1/new_vertec/vt4881.html

See also:

http://www.jblpro.com/vertec1/new_vertec/vt4882.html

[Heh, heh.]

Looks like them specs are with EQ, but similarly were B380/460....Here's a picture of a stack of 2256G's from the new Vertec sub. The look to be relabelled, or maybe reconed, W15GTI car subwoofers.

[Zilch]

They look to be relabelled, or maybe reconed, W15GTI car subwoofers.There's certainly the suggestion of synergy between the car audio and pro lines, of late. Are they using "Differential Drive" technology in mobile? I should go look, maybe....

Apparently so:

http://www.jbl.com/car/products/product_detail.aspx?prod=W15GTI&ser=GTI&cat=SUB

They're no cheaper, tho. The "Boxes & Parameters" links there are kinda interesting.....

[Don McRitchie]

I'm not sure of the logic behind that sub choice. JBL has gone out of its way to pioneer lightweight neo drivers for the Vertec line to reduce transport costs for tour sound operators. Sticking a 30lb woofer in their sub goes against that whole approach.

[johnaec]

Are they using "Differential Drive" technology in mobile?I've got one of the 10" W10GTI differential drive speakers ready to go into a mobile sub cabinet. The magnet assembly is identical for the 10, 12, and 15 inch series. I think part of the reason they're going to very high output speakers is more for the space savings instead of weight, especially when considering extra weight of larger cabinets. Even this little 10" has an Xmax of 17.78 mm!

I wonder if the pro series wires them up the same, with separate leads going to each voice coil, as below:

[Zilch]

From U.S. Patent #5,313,525, May 17, 1994, to Klasco; Michael A. (Berkeley, CA): :D

"A further alternative enclosure system is the triple chamber bandpass system which utilizes a manifold bass reflex system with the manifold cavity enclosed and ported. The basic configuration is identical to the manifold bass reflex configuration, except that the common cavity is enclosed where the two woofers face each other and a port is added which is tuned to an upper frequency. Two tunings are utilized, one at the low frequency limit of the intended bandpass range (within the outer subenclosures), and the other in a center chamber and tuned to the high frequency limit (below a few hundred Hz). There are two frequency ranges over which enclosure tunings help to reduce distortion by minimizing cone motion. All acoustical output from the system is by way of its port openings, which act effectively as acoustical low-pass filters and further reduce distortion. Dual transducers are employed in a push-push arrangement which reduces mechanical stresses and minimizes third harmonic distortion through cancellation of non-linearities."

References:

Audio Engineering Society Preprint, "A Compound Loading Loudspeaker System: Simulation and Acoustic Characteristics in A Low Frequency Range", Noboru Kyouno, Nov. 1988.
Adamson B218F, 1989.
JBL Introduces SB-1 and SB-5 Control Series Sub-Bass Systems With Triple Chamber Bandpass, 1990.
Acustica, vol. 39, "Loudspeaker Enclosure To Simulate An Infinite Baffle", A. D. Broadhurst, pp. 316-322, 1978.
Speaker Builder, "Constructing a Sontek Subwoofer", Phil Todd, pp. 20-25, Feb. 1985.
Bose Professional Wave Systems, 1987.
Acoustic Research STC 660 Subwoofer Satellite System, 1988.
EAW 1988 New Product KF600, 1988.
Renkus-Heinz Model Sub-152, 1988.
JBL 4688 Sub-Bass System, Mar. 1990.
JBL 4688, 4688-4 TCB Subwoofer System, Aug. 1990.
SR2 System Subwoofer, undated.
Bose 302 Tandem-Tuned Bass System, undated.
ADC Soundshaper 3025 3-Piece Speaker System, undated.
JBL Technical Notes, vol. 1, No. 19, "Sub-Bass Systems Using Triple Chamber Bandpass (TCB) Technology", undated

Anybody have the referenced JBL Tecnical note Vol. 1, No. 19?

[Zilch]

Here's what I was thinking of when I alluded to JBL having a current bandpass product with center slot port similar to the proposed designs:

http://www.jblpro.com/mpro/PDF/MP255S.pdf

The Bose patent has expired, so "dual-tuned bandpass" enclosures are apparently again fair game. There are similar designs from other manufacturers.

This one's wired in mono "Pull-Pull" configuration, the back side of the woofers facing out. The rear chamber has no apparent ports:

http://www.jblproservice.com/pdf/MPro%20Series/MP255S.pdf

Installation of the front covers creates the front chamber with center slot port, looks like. Adroitly configured, this....

[loach71]

A very similar enclosure was designed by Steve Deckert at Decware.
It is called the Housewrecker.

http://www.decware.com