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Zilch
05-14-2005, 11:52 PM
A driver that gets virtually no attention in the forum, what's the D123 good for besides acoustic guitar amps?

There's plenty of them out there, reasonably priced; what do we know about them?

4313B
05-15-2005, 07:14 AM
I never bought any while they were available in the LCS so I have no experience with them ( SURPRISE! :shock: ).

http://www.lansingheritage.org/html/jbl/catalogs/1976-comp.htm

http://www.lansingheritage.org/images/jbl/catalogs/1976-comp/page3.jpg

Also used in various 60's systems.

spkrman57
05-15-2005, 09:00 AM
I have a pair along with 075's and N2400 crossover in a GE cabinet that dates back to the late 50's or early 60's.

The sound is decent with them but the bass is light. The efficiency is around 96/97 db but not at the bottom octaves which are light up to around 80 hz.

The usable bottom end is just below 40hz, but at a level so low that you hear all the notes in a solo, but lost when the entire orchestra kicks in.

The cabinet is a "Distributed port reflex" system, which means the D123 and 075 are in the upper part of the front baffle and the bottom portion has around a dozen 1" holes drilled through.

These cabinets were from back in the day when most folks bought a enclosure and just found a driver to fit the baffle cutout. Basically a general purpose cabinet.

The pair I have are very nice to the eyes as they are detailed in the molding and looks like original grill cloth and the cabinets are made to fit in the corner as the back of the cabinet has the corner shape to it.

I paid premium cash for them as the drivers inside are "MINT" looking and orignal and in perfect working condition.

But the D123's are very effecient, thin in the bass and the chrome dust cap will beam above around 3 - 4 khz. I still like the simplistic design and run them once in awhile. I have several systems, so nothing stays in the center stage for very long.

Ron

GordonW
05-15-2005, 10:25 AM
Depends on the enclosure for them... but it looks like a D123 in about 5 cubic feet with fiberglass lined walls, tuned to about 40 Hz, should solidly make it down to 40 Hz.

Haven't measured one of them... but I suspect, as they share the cone profile of the 123A, that they MAY have a somewhat rising response in the mids (not as pronounced as say, a 2123, but a couple dB rise between 100 and 1000 Hz). This is probably what contributes to the "low bass level deficiency" thing mentioned above; this can be somewhat countered by tuning the box higher, to DELIBERATELY induce a "midbass peak" around 80 Hz, and generally raising the whole bass response output from 50-100 Hz, at the expense of a little bit of bottom end extension. In this case, maybe using a 42 or 45 Hz port frequency, might overcome the "weak bass" thing a bit...

Otherwise, one of these D123s might make a decent midbass driver in a large three- or four-way setup... in about 1 cubic foot sealed, STUFFED with fiberglass, it has a just-under-1-dB bump in the midbass region (which could be removed by making the box say, 1.25 or 1.5 cubic feet), and is solid in both power handling and response down to about 90 Hz. In a system with a 2240 or 2245 18" woofer for the bottom, this could make a good midbass, in the sense of using it like a 2020 would normally be used. With its curvilinear cone and extended response, it would be no problem to use the D123 up to 1200 or even 1500 Hz; crossing it over to a 1" throat horn/driver midrange/tweeter setup could be quite productive of an endeavor...

Regards,
Gordon.

spkrman57
05-15-2005, 10:37 AM
JBL literature puts the response at 45hz to 15Khz.

But with lowered output below 80hz and beaming in the upper octaves.

I would love to find a rear-loaded backhorn for these to fill in the lower octave response.

The 123A is a lower efficiency driver that will give more output on the bottom ocataves. Also I believe it is around 92 db vs the D123 at around 96/97db.

Still a nice sounding driver for low to medium listening. I use it alot for background music while working on something else.

Ron

Don C
05-15-2005, 11:34 AM
I had a pair of very nice 123s in bookshelf cabinets, roughly the size of L-100s. The cabinets were probably not tuned well, there was just a rectangular hole cut in the baffle with no port tube. Although the condition was great, they did not sound very good. Kind of a haystack frequency response curve, Like an L-100 but with no low bass or treble. I think that I got $190. for the pair in ebay, and I don't miss them.

Don C
05-15-2005, 11:37 AM
another

spkrman57
05-15-2005, 11:58 AM
More for their higher efficiency and extended HF response compared to say a 123A or 123A-1 which are more bottom octave minded.

Ron

LE15-Thumper
05-15-2005, 02:15 PM
I never bought any while they were available in the LCS so I have no experience with them ( SURPRISE! :shock: ).

http://www.lansingheritage.org/html/jbl/catalogs/1976-comp.htm

http://www.lansingheritage.org/images/jbl/catalogs/1976-comp/page3.jpg

Also used in various 60's systems.


"in the LCS" ?????

Zilch
05-15-2005, 02:37 PM
http://www.lansingheritage.org/images/jbl/specs/home-comp/d123/page1.jpg

4313B
05-15-2005, 02:46 PM
LCS = Loudspeaker Component Series
JBL was into component sales for awhile.
Without the LCS (mid 70's to early 80's) my interest in JBL would have been compromised.

LE15-Thumper
05-15-2005, 03:06 PM
LCS = Loudspeaker Component Series
JBL was into component sales for awhile.
Without the LCS (mid 70's to early 80's) my interest in JBL would have been compromised.

I thought that is what you meant. I was able to come up with a lot of Acronyms for "LCS" ;) , I wasn't sure what yours was :D

LE15-Thumper
05-15-2005, 03:09 PM
http://www.lansingheritage.org/images/jbl/specs/home-comp/d123/page1.jpg

What year was that bulletin ? Amazing how James B already had the foresight to make stuff to fit at the construction level.

4313B
05-15-2005, 03:18 PM
http://www.lansingheritage.org/html/jbl/specs/home-comp/d123.htm

spkrman57
05-15-2005, 07:09 PM
I would love to find a horn for mine, I see the potential they would have in a horn-loaded cabinet.

Ron

LE15-Thumper
05-15-2005, 07:57 PM
http://www.lansingheritage.org/html/jbl/specs/home-comp/d123.htm

D123 Driver Circa 1956 ????? :wtf:

And who would have thought to put a three inch voice coil in a 12" Driver ? and then a 4" inch ! Everybody else at the time saw fit with a two inch. Heck, how big was the voice coil on EV's Touted 30W ?

Kinda visionary I think

A minty D123 I picked up on the bay a while back. It is as pretty as it looks in the picture.

Steve Schell
05-16-2005, 12:24 AM
The D-123 appeared in the line about 1955. I have seen some that predated the oval badge on the rear. I suppose it was a replacement for the D-131, although I haven't researched this. It would have been simpler and cheaper to build than the D-131, with its 4" voice coil and D-130 style motor.

I have played with them off and on over the years and like them a lot. True, they don't reach low with that low moving mass, but they sound really lively in a two way system. Don't care for the sound of the aluminum dust cap. Probably my best results were with two D-123s per channel on open baffles, with big ESS Heil drivers crossed in at 1kHz. They would probably work fine as mid bass horn drivers as well.

Zilch
10-25-2006, 01:07 PM
http://audioheritage.org/vbulletin/showthread.php?t=12791

http://audioheritage.org/vbulletin/showthread.php?p=130709#post130709

Thom
10-25-2006, 06:30 PM
For a fact D123's and D131's were made concurently and are not very simular.
I wouldn't dare claim expertise I certainly don't manipulate the formulas and such. A D131 want's almost as much box as a D130 if you want best results. You can get away with a lot less box with a d123.

Zilch
10-26-2006, 12:36 AM
They're rear mount only drivers (see post #7, above,) and despite the "16 Ohms" on the foilcal and in the lit, I'm gonna hafta call 'em 8 Ohms:

[DRAT, there went my EZ MTM ambitions.... :( ]

Thom
10-26-2006, 11:48 AM
With an Le20 they used to sell pretty well against Heresy. I never saw tubes on ports until late 60's (I'm not saying it never happened) what you normaly saw was either just a hole or a hole with a baffle between the driver and the hole. I spent a couple of years early 70's working in a shop that sold mostly JBL componants mounted in cabinents built to JBL plans. The way things were set up I have to believe there was a time when JBL's emphasis was on selling their drivers which they considered to be the Rolex of drivers. The released full scale plans of just about every cabinet they made. I don't know of a cabinet they didn't release plans to but I'll play safe and say "just about".

Steve Schell
10-26-2006, 11:52 AM
Thom, you are correct of course about the D-131 and D-123 being made concurrently. My knowledge gets pretty shaky when I venture beyond 1950!

Zilch, as far as I know the rear mount only D-123s were the earlier ones. At some point they shortened the basket ribs to permit front or rear mounting. I think I still have examples of both types.

LE15-Thumper, the tradition of large voice coils in JBL drivers began with Jim Lansing's design work in the late 1940s. My theory is that he was influenced by Western Electric's postwar speaker line which had been introduced by about the time he introduced the D-130, D-130A and D-131. W.E.'s drivers featured the thin profile construction with 4" edgewound coils in their 12" drivers. They also used a 4" coil in their 10" 756A. Actually the 9" 750A from 1940 used a 4" edgewound aluminum coil on a pressed aluminum cone with large integral center dome, which might have provided some inspiration to Jim for both the Altec and JBL postwar drivers with the aluminum center domes.

Zilch
10-26-2006, 12:20 PM
With an Le20 they used to sell pretty well against Heresy. I never saw tubes on ports until late 60's (I'm not saying it never happened) what you normaly saw was either just a hole or a hole with a baffle between the driver and the hole.Yes, it took Thiele, Small, and others to develop the understanding of how bass reflex works which we now enjoy; I look forward to how elcamino's box retuning goes.

LE20 hardly even qualifies as a tweeter anymore. I'm thinking the inexpensive titanium 035tiA might be a good match, though it'll take some experimentation to determine the optimum crossover. If D123's aluminum dome is a problem, that's easily remedied.

The early literature touted the potential for "in-wall" appplication of D123. The rear mount versions won't fit in a 2 x 4 framed wall, but a flush-mount two-way seems like a good potential application.

I don't see any 12" in-walls on the market. It would appear to have a high WAF factor, as well; there's an easy and inconspicuous 2.5 cuft volume in a typical 8' 2 x 4 stud bay....

speakerdave
10-29-2006, 12:00 PM
Does anyone have the gap depth and voice coil depth on the D123?

David

John W
10-30-2006, 09:15 AM
I'm thinking the inexpensive titanium 035tiA might be a good match, though it'll take some experimentation to determine the optimum crossover. If D123's aluminum dome is a problem, that's easily remedied.


Try it Zilch! I don't think you will be dissapointed. I have been enjoying these quite a bit. Even my wife likes them. For crossover starters try the "forgotten" LX-8 with an 1.5mh inductor in series with the woofer. I pulled out the RTA on mine and and the bars confirmed a very flat response with the three position switch set at #2. I have an extra pair of LX-8s I picked up on ebay for $20 if you want to have a go.

Zilch
10-30-2006, 10:11 AM
Thanks, John, for the XO suggestion. I'll check to see if I have any here. I know there's LX 10s and "others."

Your projects are an inspiration for everyone. :thmbsup:

camusmuse
01-21-2008, 06:14 PM
Sorry for bringing back an old thread, but it deals almost exactly with a project that I have going on. What crossover frequency would you suggest between the mids and lows for the system described in the original post?

I am thinking of running four of the d123 for mids on top of four GTI1500(automotive versions of the 2226), along some custom horns for a three way active stereo setup. I'm pretty much set on 1200hz as the "high pass", and was considering 150hz or 250hz for the "low pass" all at 18db/oct. Probably want 150hz, but wanted to get some other opinions.

Thanks.....


Depends on the enclosure for them... but it looks like a D123 in about 5 cubic feet with fiberglass lined walls, tuned to about 40 Hz, should solidly make it down to 40 Hz.

Haven't measured one of them... but I suspect, as they share the cone profile of the 123A, that they MAY have a somewhat rising response in the mids (not as pronounced as say, a 2123, but a couple dB rise between 100 and 1000 Hz). This is probably what contributes to the "low bass level deficiency" thing mentioned above; this can be somewhat countered by tuning the box higher, to DELIBERATELY induce a "midbass peak" around 80 Hz, and generally raising the whole bass response output from 50-100 Hz, at the expense of a little bit of bottom end extension. In this case, maybe using a 42 or 45 Hz port frequency, might overcome the "weak bass" thing a bit...

Otherwise, one of these D123s might make a decent midbass driver in a large three- or four-way setup... in about 1 cubic foot sealed, STUFFED with fiberglass, it has a just-under-1-dB bump in the midbass region (which could be removed by making the box say, 1.25 or 1.5 cubic feet), and is solid in both power handling and response down to about 90 Hz. In a system with a 2240 or 2245 18" woofer for the bottom, this could make a good midbass, in the sense of using it like a 2020 would normally be used. With its curvilinear cone and extended response, it would be no problem to use the D123 up to 1200 or even 1500 Hz; crossing it over to a 1" throat horn/driver midrange/tweeter setup could be quite productive of an endeavor...

Regards,
Gordon.